9815Flyleaf ICAO DOC 9815 Manual On Laser Emitters And Flight Safety (2003)

User Manual:

Open the PDF directly: View PDF .
Page Count: 86

International Civil Aviation Organization

Approved by the Secretary General

and published under his authority

Manual on Laser

Emitters and

Flight Safety

First Edition — 2003

Doc 9815

AN/447



International Civil Aviation Organization

Approved by the Secretary General

and published under his authority

Manual on Laser

Emitters and

Flight Safety

First Edition — 2003

Doc 9815

AN/447

AMENDMENTS

The issue of amendments is announced regularly in the ICAO Journal and in the

monthly Supplement to the Catalogue of ICAO Publications and Audio-visual

Training Aids, which holders of this publication should consult. The space below

is provided to keep a record of such amendments.

RECORD OF AMENDMENTS AND CORRIGENDA

AMENDMENTS CORRIGENDA

No. Date Entered by No. Date Entered by

(ii)

(iii)

FOREWORD

Adequate lighting is necessary for all visual tasks. An

excess of light, however, can detrimentally affect vision to

the extent of rendering it ineffective. In aviation, a pilot

may experience high levels of lighting when flying into the

sun or looking at very bright artificial light sources such as

searchlights. The invention (in 1957) of the laser* is a

significant addition to the known aviation-related problems

associated with high-intensity lights.

Laser is an acronym for light amplification by stimulated

emission of radiation; this technique can produce a beam of

light of such intensity that permanent damage to human

tissue, in particular the retina of the eye, can be caused

instantaneously, even at distances of over 10 km. At lower

intensities, laser beams can seriously affect visual

performance without causing physical damage to the eyes.

There are, however, many useful applications of laser

technology, such as high-speed automatic scanning of bar

codes, laser printing, welding and cutting, micro-surgery,

communication by means of fibre optics, recording of

music, gyroscopes, light displays and the ubiquitous laser

pointer used by lecturers worldwide. Lasers are associated

with almost every aspect of modern life.

Whilst protection of the pilot against deliberate or

accidental laser beam strikes has been of interest to military

aviation medicine specialists for many years, it was only

with the advent of the laser light display for entertainment

or commercial purposes and subsequent accidental

illumination of civil aircraft from such displays that civil

aviation medicine specialists have become more concerned.

By 2001, many pilots had experienced incapacitation

following accidental laser beam strikes. Over 600 incidents

have been recorded worldwide, the majority of reports

coming from the United States (see Chapter 4, page 4-1 for

a summary of two significant incidents). It may be expected

that most civil aircraft laser beam strikes will be

inadvertent, but powerful laser emitters that can be

accurately targeted are now available at relatively low cost,

so the possibility of malicious use of such devices in the

future cannot be ignored.

In view of the increasing risk to flight safety posed by the

more widespread use of laser emitters around airports,

ICAO formed a study group in 1999 to evaluate the laser

risk and consider whether new Standards or Recommended

Practices (SARPs) were necessary.

The study group consisted of experts in ophthalmology and

vision care, light engineering and physics, flight operations

and regulatory aviation medicine. These experts were

nominated in part by four Contracting States: Canada,

Netherlands, United Kingdom and United States and in part

by the Aerospace Medical Association and the International

Federation of Airline Pilots’ Associations.

At the first meeting of the study group, documentation was

presented indicating that there was considerable

international concern that lasers might pose a significant

and increasing risk to flight safety and that without ICAO

action, development of necessary controls in individual

Contracting States would be inconsistent, insufficient or

worse, non-existent.

During 1999 and 2000, the Aviation Medicine Section of

the ICAO Secretariat, with the assistance of the study

group, developed the laser-related SARPs that are now

included in Annexes 11 and 14 to the Convention.

However, these SARPs do not provide the necessary

practical guidance for implementation of relevant

regulations in States. The study group, therefore,

recommended that a manual be written focussing on the

medical, physiological and psychological effects on flight

crew of exposure to laser emissions.

The information and guidance material provided in this

manual is primarily directed to decision-makers at

government level, laser operators, air traffic control

officers, aircrew, aviation medicine consultants to and

medical officers of the regulatory authorities, and doctors

involved in clinical aviation medicine, occupational health

and preventive medicine. The manual is aimed both at

reducing the need for regulatory authorities to seek

individual expert advice and at reducing inconsistencies

between Contracting States in the implementation of

national regulations.

∗The term laser has more than one meaning, see Glossary.

(iv) Manual on laser emitters and flight safety

In addition, it can be used to support training provided by

operators to flight crew with respect to the effect of laser

emitters on operational safety. It is recommended that the

information contained in Chapter 4, particularly in relation

to preventative procedures, be included in the operations

manual.

This manual contains information and guidance provided

by the study group. Comments from States and other

parties outside ICAO would be appreciated. They should be

addressed to:

The Secretary General

International Civil Aviation Organization

999 University Street

Montréal, Quebec H3C 5H7

Canada

(v)

TABLE OF CONTENTS

Page Page

Glossary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (vii)

List of abbreviations, symbols and units . . . . . . . . . (xi)

Chapter 1. Physics of lasers . . . . . . . . . . . . . . . . 1-1

1.1 Introduction to laser emitters . . . . . . . . . . . 1-1

1.2 Components of a laser . . . . . . . . . . . . . . . . 1-1

1.3 Types of lasers . . . . . . . . . . . . . . . . . . . . . . 1-2

1.4 Beam properties . . . . . . . . . . . . . . . . . . . . . 1-4

1.5 Characteristics of materials . . . . . . . . . . . . 1-6

Chapter 2. Laser hazard evaluation . . . . . . . . . . 2-1

2.1 Purpose . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-1

2.2 Background . . . . . . . . . . . . . . . . . . . . . . . . . 2-1

2.3 Accessible emission limit (AEL) . . . . . . . . 2-1

2.4 Laser hazard classification . . . . . . . . . . . . . 2-2

2.5 Nominal ocular hazard distance (NOHD) . 2-2

2.6 Optical density (OD) . . . . . . . . . . . . . . . . . 2-3

2.7 Other factors . . . . . . . . . . . . . . . . . . . . . . . . 2-3

Chapter 3. Laser beam bioeffects and

their hazards to flight operations . . . . . . . . . . . . . 3-1

3.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3-1

3.2 The hazard . . . . . . . . . . . . . . . . . . . . . . . . . 3-1

3.3 Biological tissue damage mechanisms . . . 3-2

3.4 The skin . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-4

3.5 The eye . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-5

3.6 Ocular laser beam damage terminology . . 3-8

3.7 Laser beam bioeffects . . . . . . . . . . . . . . . . 3-8

3.8 Laser beam bioeffects and air operations . 3-10

3.9 The future . . . . . . . . . . . . . . . . . . . . . . . . . . 3-15

3.10 Medical evaluation of laser beam

incidents . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-15

Chapter 4. Operational factors and

training of aircrew . . . . . . . . . . . . . . . . . . . . . . . . . . 4-1

4.1 Background . . . . . . . . . . . . . . . . . . . . . . . . 4-1

4.2 Situational awareness . . . . . . . . . . . . . . . . . 4-2

4.3 Orientation in flight . . . . . . . . . . . . . . . . . . 4-2

4.4 Preventative procedures . . . . . . . . . . . . . . . 4-3

Chapter 5. Airspace safety . . . . . . . . . . . . . . . . . 5-1

5.1 General . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-1

5.2 Airspace restrictions . . . . . . . . . . . . . . . . . . 5-1

5.3 Aeronautical assessment . . . . . . . . . . . . . . 5-4

5.4 Control measures . . . . . . . . . . . . . . . . . . . . 5-5

5.5 Determinations . . . . . . . . . . . . . . . . . . . . . . 5-5

5.6 Incident-reporting requirements . . . . . . . . . 5-7

Chapter 6. Documentation of incidents after

suspected laser beam illumination . . . . . . . . . . . . 6-1

6.1 Background . . . . . . . . . . . . . . . . . . . . . . . . 6-1

6.2 Procedures . . . . . . . . . . . . . . . . . . . . . . . . . 6-1

6.3 Documentation . . . . . . . . . . . . . . . . . . . . . . 6-1

Chapter 7. Medical examination following

suspected laser beam illumination . . . . . . . . . . . . 7-1

7.1 General . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7-1

7.2 Procedures . . . . . . . . . . . . . . . . . . . . . . . . . 7-1

Appendix A. Notice of proposal to conduct

outdoor laser operation(s) . . . . . . . . . . . . . . . . . . . . A-1

Appendix B. Suspected laser beam incident

report and suspected laser beam exposure

questionnaire . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . B-1

Appendix C. Amsler grid testing procedure . . . C-1



(vii)

GLOSSARY

Note.— The definitions of the terms listed below are

based on a pragmatic approach. The terms defined are

therefore limited to those actually used in this manual. This

listing is not intended to constitute a dictionary of terms

used in the laser field as a whole.

Absorption. Transformation of radiant energy to a different

form of energy (usually heat) by interaction with matter.

Accessible emission limit (AEL). The maximum accessible

emission power or energy permitted within a particular

laser class.

Accessible radiation. Optical radiation to which the human

eye or skin may be exposed in normal usage.

Actinic radiation. Electromagnetic radiation in the visible

and ultraviolet part of the spectrum capable of

producing photochemical changes.

Aerodrome reference point (ARP). The designated

geographical location of an aerodrome.

After-image. An image that remains in the visual field after

an exposure to a bright light.

Attenuation. The decrease in the laser beam power or

energy as it passes through an absorbing or scattering

medium.

Average power. The total energy imparted during exposure

divided by the exposure duration.

Aversion response. Closure of the eyelid or movement of

the head to avoid an exposure to a noxious stimulant or

bright light. In laser safety standards, the aversion

response (including blink reflex time) is assumed to

occur within 250 milliseconds (0.25 s).

Beam. A collection of rays that may be parallel, divergent

or convergent.

Beam diameter. For the purpose of this manual, the beam

diameter is the radial distance across the centre of a

laser beam where the irradiance is 1/e times the centre-

beam irradiance (or radiant exposure for a pulsed laser).

Beam waist. The minimum dimension of a cross section of

the beam.

Buffer angle. An angle added to the beam divergence or

intended laser projection field in order to ensure a

protection zone.

Buffer zone. A volume of air surrounding the laser beam,

all potential locations of the laser beam and all

hazardous diffuse or specular reflections, where the

maximum permissible exposure (MPE) or visual

interference levels are exceeded. It includes the beam

divergence or scanning extent of the laser beam plus the

buffer angle and the full range of the laser beam to the

point where the MPE or any applicable visual in-

terference level is not exceeded. Natural terrain or beam

masks may truncate part of this volume.

Cavity. The optical assembly of a laser usually containing

two or more highly reflecting mirrors which reflect

radiation back into the active medium of the laser.

Collateral radiation. Any electromagnetic radiation

emitted by a laser, except the laser beam itself, which is

necessary for the operation of the laser emitter or is a

consequence of its operation.

Collimated beam. A beam of radiation with very low

divergence or convergence and therefore effectively

considered parallel.

Continuous wave (CW). The output of a laser which is

operated in a continuous rather than a pulsed mode. In

laser safety standards, a laser operating with a

continuous output for a period greater than 0.25 s is

regarded as a CW laser.

Critical level. The minimum effective irradiance from a

visible laser beam which can interfere with critical task

performance due to transient visual effects.

Diffraction. Deviation of part of a beam, determined by the

wave nature of radiation and occurring when the

radiation passes the edge of an opaque obstacle.

(viii) Manual on laser emitters and flight safety

Diffuse reflection. The component of a reflection from a

surface which is incapable of producing a virtual image

such as is commonly found with flat finish paints or

rough surfaces. A matt surface will reflect the laser

beam in many directions. Viewing a diffuse reflection

from a matt surface may produce either a small or a

large retinal image, depending on the viewer distance

and the size of the illuminated surface.

Divergence (

). For the purpose of this manual, the

divergence is the increase in the diameter of the laser

beam with distance from the exit aperture, based on the

full angle at the point where the irradiance (or radiant

exposure for pulsed lasers) is 1/e times the maximum

value.

Electromagnetic radiation. The flow of energy consisting

of orthogonally vibrating electric and magnetic fields.

Electromagnetic radiation includes optical radiation,

X-rays and radio waves.

Electromagnetic spectrum. The range of frequencies or

wavelengths over which electromagnetic radiations are

propagated. The spectrum ranges from short wave-

lengths, such as gamma rays and X-rays, through

visible radiation to longer wavelength radiations of

microwaves, and television and radio waves.

Energy. The capacity for doing work. Energy content is

commonly used to characterize the output from pulsed

lasers and is generally expressed in joules (J).

Excited state. The state of an atom or molecule when it is

in an energy level with more energy than in its normal

or “ground” state.

Exposure duration. The duration of a pulse or a series or

a train of pulses, or of continuous emission of laser

radiation incident upon the human body.

Flash-blindness. The inability to see (either temporarily or

permanently) caused by bright light entering the eye

and persisting after the illumination has ceased.

Free radical. An atom or group of atoms in a transient

chemical state containing at least one unpaired electron.

Free radicals may be produced within or introduced into

biological tissue where they may cause damage.

Gaussian beam profile. The bell-shaped profile of a laser

beam when the laser is operating in the simplest mode.

Glare. A temporary disruption in vision caused by the

presence of a bright light (such as an oncoming car’s

headlights) within an individual’s field of vision. Glare

is unassociated with biological damage and lasts only as

long as the bright light is actually present within the

individual’s field of vision.

Hazard. Something with the potential to cause harm to

people, property or the environment.

Hazard zone. The space within which the level of radiation

during operation of a laser emitter exceeds the

applicable exposure limit. See also nominal hazard

zone (NHZ).

Infrared radiation. For the purpose of this manual,

electromagnetic radiation with wavelengths that lie

within the range 700 nm to 1 mm.

Instrument flight rules (IFR). A set of rules governing the

conduct of flight under instrument meteorological

conditions.

Interlock. See safety interlock.

Invisible laser beam. A laser emission with a wavelength

either shorter than 400 nm or longer than 700 nm. Laser

sources near these defining limits may be capable of

producing a visual stimulus.

Irradiance (E). The power per unit area, expressed in watts

per square centimetre (W/cm2) or watts per square

metre (W/m2).

Laser. 1) An acronym for light amplification by stimulated

emission of radiation. 2) A device that produces an

intense, coherent, directional beam of optical radiation

by stimulating emission of photons by electronic or

molecular transitions to lower energy levels.

Laser-beam critical flight zone (LCFZ). See protected

flight zones a).

Laser-beam free flight zone (LFFZ). See protected flight

zones b).

Laser-beam free level. The maximum level of visible optical

radiation which is not expected to cause any visual

interference to an individual performing critical tasks.

Laser-beam sensitive flight zone (LSFZ). See protected

flight zones c).

Laser emitter. Same as laser 2).

Laser safety officer (LSO). An individual who is knowl-

edgeable in the evaluation and control of laser hazards

and has responsibility for oversight of the control of

those hazards.

Glossary (ix)

Laser source. See source.

Light (visible radiation). A form of electromagnetic

radiation capable of producing a visual stimulus to the

human eye. Its wavelength range is approximately from

400 nm to 700 nm (between ultraviolet and infrared).

Laser sources of an equivalent power slightly outside

this range may be capable of producing less intense

visual stimuli.

Limiting aperture (Df). The diameter of a circle over which

irradiance or radiant exposure is averaged for

comparison to the maximum permissible exposure

(MPE).

Local laser working group (LLWG). A group, convened to

assist in evaluating the potential effect of laser

emissions on aircraft operators in the vicinity of the

proposed laser activity. Participants may include, but

are not limited to, representatives from the aerodrome

tower, area control centre, aerodrome management,

airspace users, local officials, military representatives,

qualified subject experts, laser manufacturers and the

laser proponent.

Maximum permissible exposure (MPE). The inter-

nationally accepted maximum level of laser radiation to

which human beings may be exposed without risk of

biological damage to the eye or skin.

Mitigation. Use of control measures aimed at neutralizing

the effect of laser beams on flight safety.

Nominal hazard zone (NHZ). The space within which the

level of the direct, reflected or scattered radiation

during operation of a laser emitter exceeds the

applicable maximum permissible exposure (MPE).

Exposure levels beyond the boundary of the NHZ are

below the applicable MPE level.

Nominal ocular hazard distance (NOHD). The distance

along the axis of the laser beam beyond which the

appropriate maximum permissible exposure (MPE) is

not exceeded (i.e. an indication of the “safe viewing”

distance). An equivalent term for skin exposure is “skin

hazard distance”.

Normal flight zone (NFZ). See protected flight zones d).

Optical density (OD). A physical property of a material that

quantifies the attenuation of the laser beam.

Optical radiation. Part of the electromagnetic spectrum

comprising infrared, visible and ultraviolet radiations.

Photon. In quantum mechanics, the smallest particle of

optical radiation.

Pointing accuracy. The maximum angle of expected error

in beam direction during all projected uses of the laser

emitter.

Population inversion. The condition needed for light

amplification to occur whereby the number of atoms in

an excited state is greater than the number of atoms in

a lower energy state.

Power. The rate at which energy is emitted, transferred or

received. Unit: watts (joules per second).

Proponent. The legal entity (corporation, company,

individual) applying to conduct an outdoor laser

operation at a specific time and location.

Protected flight zones. Airspace specifically designated to

mitigate the hazardous effects of laser radiation.

a) Laser-beam critical flight zone (LCFZ). Airspace

in the proximity of an aerodrome but beyond the

laser-beam free flight zone (LFFZ) where the

irradiance is restricted to a level unlikely to cause

glare effects.

b) Laser-beam free flight zone (LFFZ). Airspace in

the immediate proximity to the aerodrome where

the irradiance is restricted to a level unlikely to

cause any visual disruption.

c) Laser-beam sensitive flight zone (LSFZ). Airspace

outside, and not necessarily contiguous with, the

LFFZ and LCFZ where the irradiance is restricted

to a level unlikely to cause flash-blindness or after-

image effects.

d) Normal flight zone (NFZ). Airspace not defined as

LFFZ, LCFZ or LSFZ but which must be protected

from laser radiation capable of causing biological

damage to the eye.

Pulsed laser. A laser that delivers its energy in individual

pulses lasting less than 0.25 s. See repetitively-pulsed

laser.

Pulse duration. The duration of a laser pulse, usually

measured as the time interval between the half-power

points on the leading and trailing edges of the pulse.

(x) Manual on laser emitters and flight safety

Pulse repetition frequency (PRF). The number of pulses

that a laser produces over an applicable time frame

divided by that time frame. For uniform pulse trains

lasting over 1 s, the PRF is the number of pulses

emitted by the laser in 1 s. Unit: hertz (Hz).

Radian. A unit of angular measure equal to the subtended

angle at the centre of a circle by an arc whose length is

equal to the radius of the circle. 1 radian = 57.3

degrees; 2π radians = 360 degrees.

Radiant energy (Q). Energy emitted, transferred or

received as radiation. Unit: joule (J).

Radiant exposure (H). The laser beam energy per unit area,

expressed in joules per square centimetre (J/cm2) or

joules per square metre (J/m2).

Radiant power (

). Power emitted, transferred or received

as radiation. Unit: watt (W).

Reflection. Deviation of radiation following incidence on a

surface. A reflection can be either diffuse or specular.

See diffuse reflection and specular reflection.

Refraction. The redirection of light as it passes from one

medium to another.

Repetitively-pulsed laser. A laser producing multiple pulses

of radiant energy occurring in sequence with a pulse

repetition frequency (PRF) greater than 1 Hz.

Retinal hazard region. Wavelengths between 400 nm and

1400 nm.

Safety interlock. 1) A device which is activated upon entry

to a laser laboratory or enclosure, which terminates

laser operation or reduces personnel exposure to below

the maximum permissible exposure (MPE). 2) A device

that is activated upon removal of the protective housing

of a laser in such a way as to prevent exposure above

the maximum permissible exposure (MPE).

Scanning laser beam. Laser radiation that moves, i.e. has

a time-varying direction, source or pattern of

propagation with respect to a stationary frame of

reference.

Scintillation. Rapid changes in irradiance levels in a cross-

section of a laser beam, caused by variations of the

index of refraction in a medium as a consequence of

temperature and pressure fluctuations.

Sensitive level. The minimum effective irradiance from a

visible laser beam, which can cause temporary vision

impairment and therefore interfere with performance of

vision-dependent tasks. Illumination at this level may

cause after-images or flash-blindness.

Source. A laser emitter or a laser-illuminated reflecting

surface.

Specular reflection. A mirror-like reflection that usually

maintains the directional characteristics of a laser beam.

Terminated beam. An output from a laser which is directed

into airspace but is confined by a suitable object that

blocks the beam or prohibits the continuation of the

beam at levels capable of producing psychological

effects or visual disruption.

Transmission. Passage of radiation through a medium. If

not all the radiation is absorbed, that which passes

through is said to be transmitted.

Ultraviolet radiation. Electromagnetic radiation with

wavelengths shorter than those of visible radiation, for

the purpose of this manual: 180 to 400 nm.

Vestibular apparatus. The organ of equilibrium in the inner

ear. Because of its complicated anatomy, it is also

called the labyrinth. It consists of the semicircular

canals and the otolith organs.

Visible radiation. See light.

Visual flight rules (VFR). A set of rules governing the

conduct of flight under visual meteorological

conditions.

Visual interference level. A visible laser beam, with an

irradiance less than the maximum permissible exposure

(MPE), that can produce a visual response which

interferes with the safe performance of sensitive or

critical tasks by aircrew or other personnel. This limit

varies in accordance with the particular zone where the

laser is operating. A generic term for critical level,

sensitive level or laser-free level.

Wavelength (λ). The distance between two successive

points on a periodic wave that have the same phase. It

is commonly used to provide a numeric description of

the colour of visible laser radiation.

(xi)

LIST OF ABBREVIATIONS, SYMBOLS AND UNITS

ADI attitude direction indicator

AEL accessible emission limit

AGL above ground level

ANSI American National Standards Institute

ARP aerodrome reference point

ATC air traffic control

ATIS automatic terminal information service

CIE International Commission on Illumination

(Commission Internationale de l’Éclairage)

CW continuous wave

CZED critical zone exposure distance

Dflimiting aperture

DME distance measuring equipment

FAA Federal Aviation Administration

FDA U.S. Food and Drug Administration

FLIR forward looking infrared

FSEL flight safe exposure limits

H radiant exposure

HSI horizontal situation indicator

HUD head-up display

Hz hertz

IFR instrument flight rules

ILS instrument landing system

IMC instrument meteorological conditions

IR infrared

J joule

λwavelength

laser light amplification by stimulated emission

of radiation

LCFZ laser-beam critical flight zone

LED light emitting diode

LEP laser eye protection

LFED laser free exposure distance

LFFZ laser-beam free flight zone

LIDAR light detection and ranging

LLWG local laser working group

LSA loss of situational awareness

LSFZ laser-beam sensitive flight zone

LSO laser safety officer

MFD multifunction display

MIL maximum irradiance level

MOVL minimal ophthalmoscopically visible lesion

MPE maximum permissible exposure

mrad milliradian

MSL mean sea level

navaid aid to air navigation

Nd:YAG neodymium yttrium-aluminium-garnet

NFZ normal flight zone

NHZ nominal hazard zone

NIR near infrared

nm nanometre

NM nautical mile

NOHD nominal ocular hazard distance

NOTAM notice to airmen

NSHD nominal sensitivity hazard distance

NVD night vision device

NVG night vision goggles

OD optical density

PCP pre-corrected power

ϕbeam divergence

Φradiant power

PRF pulse repetition frequency

Q radiant energy

SAE Society of Automotive Engineers

SD spatial disorientation

SIAP standard instrument approach procedure

STAR standard terminal arrival route

SZED sensitive zone exposure distance

TVI temporary visual impairment

TVL temporary vision loss

UTC coordinated universal time

UV ultraviolet

VCF visual correction factor

VCP visually corrected power

VED visual effect distance

VFR visual flight rules

VMC visual meteorological conditions

Wwatt

YAG yttrium-aluminium-garnet

(xii) Manual on laser emitters and flight safety

Definitions of units

e. A term for the irrational number that corresponds to the base of natural logarithms: 2.71828183… .

Hertz (Hz). The unit that expresses the frequency of a periodic oscillation in cycles per second.

Joule (J). A unit of energy. Joules = watts × seconds.

Milliradian (mrad). A unit of angular measure used for beam divergence. A milliradian is about 0.057 degree (one

seventeenth of a degree) or 3.44 minutes of arc.

Watt (W). A unit of power. 1 watt = 1 joule per second.

1-1

Chapter 1

PHYSICS OF LASERS

1.1 INTRODUCTION TO LASER EMITTERS

1.1.1 A basic insight into how a laser works helps in

understanding the hazards incurred when a laser emitter is

used. As shown in Figure 1-1, electromagnetic radiation is

emitted whenever a charged particle (e.g. an electron) gives

up energy. This happens every time an electron drops from

a higher energy state, Q1, to a lower energy state, Q0, in an

atom or ion as occurs in a fluorescent light. This can also

happen from changes in the vibrational or rotational state of

molecules.

1.1.2 The colour of light is determined by its

frequency or wavelength. The shorter wavelengths are the

ultraviolet (UV) and the longer wavelengths are the

infrared (IR). The smallest particle of light energy is

described in quantum mechanics as a photon. The energy in

joules, E, of a photon is determined by its frequency,

hertz (Hz), and Planck’s constant, h (6.63 × 10–34 J • s), as

follows:

1.1.3 The velocity of light in a vacuum, c, is 3 × 108

metres per second (m/s). The wavelength, λ, of light is

related to the frequency as follows:

1.1.4 The difference in energy levels across which an

excited electron drops determines the wavelength of the

emitted light. As the energy increases, the wavelength

decreases.

1.2 COMPONENTS OF A LASER

1.2.1 As shown in Figure 1-2, the three basic

components of a laser are:

• Lasing medium (crystal, gas, semiconductor, dye,

etc.)

Ehv×=

λc

--=

Figure 1-1. Emission of radiation from an atom by transition of

an electron from a higher energy state to a lower energy state

Q Lower energy state

Q Higher energy state

photon energy

hv = Q – Q

1-2 Manual on laser emitters and flight safety

• Pump source (adds energy to the lasing medium,

e.g. xenon flash lamp, electrical current to cause

electron collisions, radiation from another laser, etc.)

• Optical cavity (typically bound by reflectors to act

as the feedback mechanism for light amplification)

1.2.2 Electrons in the atoms of the lasing medium

normally reside in a steady-state lower energy level. When

energy from a pump source is added to the atoms of the

lasing medium, the majority of the electrons are excited to

a higher energy level, a phenomenon known as population

inversion. This phenomenon must occur in order to achieve

light amplification.

1.2.3 The excited state is an unstable condition for

these electrons. They will stay in this state for a short time

and then decay back to their original energy state. This

decay can occur in two ways — spontaneously or by

stimulation. If, before an excited electron spontaneously

decays, it is hit with a photon with a certain wavelength,

the electron will be stimulated into decay and will emit a

photon of the same wavelength and in the same direction as

the incident photon. If the direction of this reaction is

parallel to the optical axis of the cavity, the emitted photons

travel back and forth in the cavity stimulating more and

more transitions and releasing more and more photons all

in the same direction and with the same wavelength. The

light energy is therefore amplified. Since one of the mirrors

is a partial reflector, part of the amplified energy is emitted

as a laser beam.

1.2.4 In practice, it is very difficult to obtain a

population inversion when utilizing only one excited

energy level. Electrons in this situation have a tendency to

decay to their ground state very quickly. As shown in

Figure 1-3, a lasing medium typically has at least one

excited (metastable) state where electrons can be trapped

long enough (microseconds to milliseconds) to maintain a

population inversion so that lasing can occur. Although

laser action is possible with only two energy levels, most

lasers have four or more levels.

1.3 TYPES OF LASERS

1.3.1 There are a number of methods used in

producing laser energy. Common methods include the use

of semiconductors, liquid dye, solid state, gas and metal

vapour. Although the technology behind each type can be

quite different, the resulting laser energy has the same basic

characteristics (see Table 1-1).

1.3.2 In recent years, the semiconductor laser (laser

diode) has become the most prevalent laser type. The laser

diode is a light emitting diode (LED) with an optical cavity

to amplify the light emitted from the energy band gap that

exists in semiconductors.

Figure 1-2. Diagram of solid state laser

Pump source

Lasing medium

Partial

reflector

Laser

output

Optical cavity

Total

reflector

Chapter 1. Physics of lasers 1-3

Table 1-1. Examples of common lasers

Lasing medium Laser method Spectral region Wavelength

Argon fluoride Gas UV 193 nm

Xenon chloride Gas UV 308 nm

Helium cadmium Gas UV

Blue

325 nm

442 nm

Argon Gas Blue

Green

488 nm

514 nm

Krypton Gas Blue

Green

Yellow

Red

476 nm

528 nm

568 nm

647 nm

Copper vapour Metal vapour Green

Yellow

510 nm

578 nm

Frequency-doubled Nd:YAG Solid state Green 532 nm

Helium neon Gas Green

Yellow

Orange

Red

Near IR

543 nm

594 nm

612 nm

633 nm

1.15 µm

Rhodamine 6G Liquid dye Visible 550–650 nm

Gold vapour Metal vapour Red 628 nm

Gallium aluminium arsenide Semiconductor Visible – near IR 670–830 nm

Ruby Solid state Red 694 nm

Alexandrite Solid state Near IR 700–815 nm

Gallium arsenide Semiconductor Near IR 840 nm

Titanium sapphire Solid state Near IR 840–1 100 nm

Nd:YAG Solid state Near IR 1.06 µm

Erbium:glass Solid state Mid IR 1.54 µm

Erbium:YAG Solid state Mid IR 2.94 µm

Carbon dioxide Gas Far IR 10.6 µm

1-4 Manual on laser emitters and flight safety

1.3.3 Lasers can operate continuously (continuous

wave or CW) or may produce pulses of laser energy. Pulsed

laser systems are often repetitively pulsed. The pulse rate or

pulse repetition frequency (PRF) as well as pulse duration

and peak power are extremely important in evaluating

potential biological hazards. Due to damage mechanisms in

biological tissue, repetitively pulsed lasers can often be

more hazardous than a CW laser with the same average

power.

1.4 BEAM PROPERTIES

Laser output intensity

1.4.1 Lasers either emit continuously or produce

discrete pulses of optical radiation. When dealing with

continuous wave (CW) lasers, beam power is used. Beam

energy is used for single pulse lasers. However, when

dealing with repetitively pulsed lasers, either parameter can

be used. Care must be taken to ensure that the correct

parameter is considered when comparisons with safety

thresholds are made.

1.4.2 Laser power is the rate with which laser energy

is emitted. This means that at any given instant, a laser can

produce a certain quantity of laser power. Laser energy is a

measure of the amount of optical radiation received in a

given period of time (such as a single laser pulse). Power

is typically given in watts (W) and energy is typically given

in joules (J). They are mathematically related as follows:

Irradiance and radiant exposure

1.4.3 With the exception of what is absorbed by the

atmosphere, the amount of energy available at the output of

the laser will be the same amount of energy contained

within the beam at any point downrange. Figure 1-4

illustrates a typical laser beam with a sampling area smaller

than the cross-sectional area of the beam. The amount of

energy available within the sampling area will be

considerably less than the amount of energy available

within the total beam. Irradiance describes the power per

unit area, and radiant exposure describes the energy per

unit area of a laser beam.

Laser modes (laser power distribution)

1.4.4 Laser beams can have complex patterns and

shapes. The optical power distribution within a laser beam

(called the laser mode) is typically expressed with either a

single bell-shaped (Gaussian) power density profile or a

1 watt = 1 joule

1 sec

Figure 1-3. Diagram of three-level laser energy

Ground energy level

Stimulated emission

of radiation

Metastable energy level

Spontaneous

energy decay

Excited energy level

Pumping

energy

Chapter 1. Physics of lasers 1-5

combination of multiple bell-shaped profiles. A uniform

(constant) power mode is actually a combination of many

Gaussian profiles overlapping each other. The ideal laser is

considered to have a single Gaussian profile for most laser

applications. This mode is often assumed in order to

simplify laser hazards analyses.

1.4.5 Since a Gaussian distribution has no

mathematical beginning or ending (see Figure 1-5), defining

the diameter of a laser beam can be difficult. To solve this

problem, one can define the diameter of a laser beam by

determining the diameter of an aperture that would allow

only a certain percentage of the total beam output to pass

through. The 1/e beam diameter is defined as the size of an

aperture that would block 36.8 per cent (1/e) of the beam

output (allowing 63.2 per cent to pass). This is the method

most often used for laser safety evaluations. Some laser

manufacturers will specify their laser beam diameters

assuming an aperture that blocks 13.5 per cent (1/e2) of the

output (allowing 86.5 per cent to pass). The 1/e beam

diameter is equal to the 1/e2 beam diameter divided by the

square root of 2 (i.e. 1.414).

Line width

1.4.6 Light from a conventional light source is

extremely broadband (containing wavelengths across the

electromagnetic spectrum). If one were to place a filter that

would pass only a very narrow band of wavelengths (e.g. a

green filter) in front of a white or broadband light source,

only that colour or wavelength region would be seen

exiting the filter (see Figure 1-6).

Figure 1-4. Illustration of irradiance

Figure 1-5. Beam diameter

Sampling area

1 cm

Distance

Intensity

Beam

diameter

Beam diameter

1-6 Manual on laser emitters and flight safety

1.4.7 Light from the laser is similar to the light seen

from the filter. However, instead of a narrow band of

wavelengths, none of which is dominant as in the case of

the filter, there is a much narrower bandwidth about a

dominant centre frequency emitted from the laser. The

colour or wavelength of light being emitted depends on the

type of lasing material being used. For example, if a

neodymium:yttrium aluminium garnet (Nd:YAG) crystal is

used as the lasing material, light with a wavelength of

1 064 nm will be emitted. Certain materials and gases are

capable of emitting more than one wavelength. The wave-

length of the light emitted in such a case is dependent on

the optical configuration of the laser.

Divergence

1.4.8 Light from a conventional light source diverges

(spreads rapidly) as illustrated in Figure 1-7. The power or

energy per unit area may be large at the source, but it

decreases rapidly as an observer moves away from the

source. In contrast, the output of the laser shown in

Figure 1-8 has a very small divergence and the beam ir-

radiance or radiant exposure at shorter distances is almost

the same at the observer as at the source. Thus, within a

narrow beam, relatively low-power lasers are able to

project more energy than can be obtained from much more

powerful conventional light sources.

1.4.9 The divergence, ϕ, of a laser beam used in laser

safety calculations is defined as the full angle of the beam

spread measured between those points which include laser

energy or irradiance equal to 1/e of the maximum value. As

a laser beam propagates through space, it produces a profile

as shown in Figure 1-9. The beam diameter, DL, is a

function of range, r, from the exit port or beam waist and

can be calculated as:

where a is the 1/e beam diameter at the exit port or beam

waist.

1.5 CHARACTERISTICS OF MATERIALS

Reflection

1.5.1 Materials can reflect, absorb and transmit light

rays. Reflection of light is best illustrated by a mirror. If

light rays strike a mirror, almost all of the energy incident

on the mirror will be reflected. Figure 1-10 illustrates how

a plastic or glass surface will act on an incident light ray.

The sum of energy transmitted, absorbed and reflected will

equal the amount of energy incident upon the surface.

1.5.2 A surface is specular (mirror-like) if the size of

surface imperfections and variations are much smaller than

the wavelength of incident optical radiation. When

irregularities are randomly oriented and are much larger

than the wavelength, then the surface is considered diffuse.

In the intermediate region, it is sometimes necessary to

regard the diffuse and specular components separately.

1.5.3 A flat specular surface will not change the

divergence of the incident light beam significantly. Curved

specular surfaces, however, will change the beam

divergence. The amount that the divergence is changed is

DLa2r2ϕ2

Figure 1-6. Laser line width

“Line filter” with

broadband source

Laser source

Broadband source

Chapter 1. Physics of lasers 1-7

dependent on the curvature of the surface. Figure 1-11

demonstrates these two types of surfaces and how they will

reflect an incident laser beam. The divergence and the

curvature of the reflector have been exaggerated to better

illustrate the effects. The value of irradiance measured at a

specific range from the reflector will be less after reflection

from the curved surface than after reflection from the flat

surface, unless the curved reflector focuses the beam near

or at that range.

1.5.4 A diffuse surface will reflect the incident laser

beam in all possible directions. The beam path is not

maintained when the laser beam strikes a diffuse reflector.

Whether a surface is a diffuse reflector or a specular

reflector will depend upon the wavelength of the incident

laser beam. A surface that would be a diffuse reflector for

a visible laser beam might be a specular reflector for an IR

laser beam. As illustrated in Figure 1-12, the effect of

various curvatures of diffuse reflectors makes little

difference on the reflected beam. The phenomenon known

as scatter is the diffuse reflection from very small particles

in the air.

Refraction

1.5.5 Refraction is the deflection of a ray of light

when it passes from one medium into another. If light is

incident upon an interface separating two transmitting

media (such as an air-glass interface), some light will be

Figure 1-7. Divergence of conventional light beam

Figure 1-8. Divergence of laser beam

Wavefront

Conventional

source

Aperture

Observer

Laser

Wavefront

Aperture Observer

1-8 Manual on laser emitters and flight safety

transmitted while some will be reflected from the surface.

If no energy is absorbed at the interface, T + R = 1.00

where T and R are the fractions of the incident beam

intensity that are transmitted and reflected. T and R are

called the transmission and reflection coefficients,

respectively. These coefficients depend not only upon the

properties of the material and the wavelength of the

radiation but also upon the angle of incidence.

1.5.6 The angle that an incident ray of radiation forms

with the normal (perpendicular) to the surface will

determine the angle of refraction and the angle of reflection

(the angle of reflection equals the angle of incidence). The

relationship between the angle of incidence (θ) and the

angle of refraction (θ') is:

n sin (θ) = n' sin (θ')

where n and n' are the indices of refraction of the media

that the incident and transmitted rays move through,

respectively (see Figure 1-10).

1.5.7 Since refraction can change the irradiance or

radiant exposure, it can either increase or reduce a laser

hazard.

Absorption

1.5.8 As light propagates through the atmosphere or

any medium, its total power or energy is attenuated by

absorption and scattering. After propagating a distance, r,

through the atmosphere, intensity, I, is given by:

I = I0e–

where I0 is the initial intensity and

is the atmospheric

attenuation coefficient. The units of

must be the inverse

to that of r, that is, if r is represented in cm, then

must

be represented in cm–1 so that the term

r is dimensionless.

1.5.9 This equation shows that the intensity falls off

exponentially as a function of the distance from the laser

source. The attenuation coefficient is dependent on the

wavelength of the laser. Because of the combination of

absorption and scattering effects, the attenuation coefficient

is a complex function of wavelength having a large value at

some wavelengths and a small value at others.

Scintillation

1.5.10 Scintillation is caused by random variations in

the index of refraction of the atmosphere through which the

beam is passing. These index variations are caused by

localized temperature and pressure fluctuations. This results

in a focusing effect which creates hot spots in the beam

pattern, most pronounced at long ranges. Scintillation of a

laser beam creates a flickering pattern of light similar to

what one might expect at the bottom of a swimming pool

when the water surface is not calm and the sun shines into it.

Figure 1-9. Geometry of laser beam

Laser

Chapter 1. Physics of lasers 1-9

Figure 1-10. Light ray incident to a glass surface

Figure 1-11. Specular reflectors

Normal

Incident ray Reflected ray

Transmitted

(refracted) ray

n’

q’

Laser

1-10 Manual on laser emitters and flight safety

Figure 1-12. Diffuse reflectors

Laser

2-1

Chapter 2

LASER HAZARD EVALUATION

2.1 PURPOSE

The purpose of a laser hazard evaluation is to minimize the

potential for injury to personnel from a laser emitter. As

part of this evaluation, the accessible emission limit (AEL),

laser classification, nominal ocular hazard distance

(NOHD) and optical density (OD) required for personnel

protection are determined. In addition, engineering and

administrative control measures should be considered.

2.2 BACKGROUND

2.2.1 The retina is especially sensitive to laser light

beams for two reasons:

a) irradiance from a conventional source, such as a

light bulb, is reduced with increasing distance from

the source according to the inverse square law, i.e.

the irradiance is reduced as a function of the square

of the distance from the source. Since a laser beam

is collimated, it does not follow the inverse square

law and its irradiance for a given power output is

usually far greater at a given distance than that from

a conventional light source; and

b) if light from a conventional source is focused by

means of a reflecting surface, as in a searchlight,

the irradiance downrange of the source is greater

than would be expected according to the inverse

square law. However, it is not possible to collimate

conventional light energy. For a given power

output, a conventional light source cannot,

therefore, produce a light beam which has an

irradiance similar to that of a laser beam.

2.2.2 Collimated light rays reaching the eye are

focused by the cornea and lens onto a very small area of the

retina similar to the way parallel light rays from the sun can

be focused by a magnifying glass into a spot of sufficient

irradiance to burn paper. A laser beam can have an

irradiance which exceeds that of the sun, even if the laser

is of relatively low power (e.g. 5 milliwatt) and the

observer is at a considerable distance from the source. In

this context, the focusing ability of the eye is very

important. Laser light passing through a pupil of 7 mm

diameter can be focused into a spot on the retina only 2–20

µm big. It can be calculated that the irradiance of

collimated light is increased up to 100 000 times from the

cornea to the retina.

2.3 ACCESSIBLE EMISSION LIMIT (AEL)

2.3.1 The AEL is defined as the maximum accessible

emission power or energy permitted within a particular

class. The class 1 AEL is the value to which laser output

parameters are compared. The class 1 AEL is calculated by

multiplying the maximum permissible exposure (MPE) by

the area of the limiting aperture.

Maximum permissible exposure (MPE)

2.3.2 The MPE is a function of wavelength, exposure

time and the nature of exposure (intrabeam, diffuse

reflection, eye or skin). MPE values are determined from

biological studies and are published in regional, national

(e.g. American National Standards Institute ANSI Z136.1)

and international (e.g. International Electrotechnical

Commission IEC 60825-1) laser safety standards.

2.3.3 MPE values are expressed in terms of irradiance

or radiant exposure and are given in W/cm2 or J/cm2 (W/m2

or J/m2). They represent the maximum levels to which a

person can safely be exposed without incurring biological

damage. However, sub-damage threshold effects may be

significant at exposure levels below the MPE.

Limiting aperture (Df)

2.3.4 The limiting aperture (Df) is the maximum

diameter of a circle over which irradiance or radiant

2-2 Manual on laser emitters and flight safety

exposure can be averaged. It is a function of wavelength

and exposure duration. These values are provided in

national and international laser safety standards. The

limiting aperture is a linear measurement and is thus

expressed in terms of cm or mm.

2.3.5 The MPE for eye exposure in the 400 to 1 400

nm band (retinal hazard region) is based upon the total

energy or power collected by the night-adapted human eye,

which is assumed to have an entrance aperture of 7 mm in

diameter. This diameter is the limiting aperture. To

determine the potential hazard, the maximum energy or

power that can be transmitted through this aperture must be

determined. This amount is compared to the class 1 AEL.

For lasers with wavelengths outside the retinal hazard region

and for the skin, other limiting apertures may apply (see

applicable national or international standards).

2.4 LASER HAZARD CLASSIFICATION

2.4.1 Laser hazard classifications are used to indicate

the level of laser radiation hazard inherent in a laser system

and the extent of safety controls required. These range from

class 1 lasers, which are safe for direct beam viewing under

most conditions, to class 4 lasers, which require the most

strict controls.

2.4.2 Classification is based only on unaided and

5-cm-aided viewing conditions. This means that the power

or energy that can pass through the limiting aperture

(known as the effective power or energy) is compared to the

appropriate AEL when determining hazard classification.

The laser classification system is summarized below (for a

full description, reference should be made to the applicable

national or international standards).

Class 1 lasers

2.4.3 Class 1 lasers are lasers which cannot emit

radiation in excess of the class 1 AEL (based on the

maximum possible duration inherent in the design or

intended use of the laser) or which have adequate

engineering controls to restrict access to the laser radiation

from an embedded higher class of laser. This does not,

however, necessarily mean that the system is incapable of

doing harm. Since only unaided and 5-cm-aided viewing

conditions are considered, hazards may still be posed when

viewing optics with a greater optical gain than 7.14 (5-cm

optics) are used or if access to the interior of the laser

emitter is possible.

Class 2 lasers

2.4.4 Class 2 lasers are low-power visible (400 to

700-nm wavelength) lasers and laser systems that can emit

an accessible output exceeding the class 1 limits but not

exceeding the class 1 AEL for a 0.25 second exposure

duration. The class 1 AEL for a 0.25 second exposure

duration is 1 mW. Invisible lasers cannot be class 2.

Class 3 lasers

2.4.5 Class 3 is subdivided into 3a and 3b (3A and 3B

in international standards). Class 3a lasers are medium-

power lasers with an output between 1 and 5 times the

class 1 AEL (class 2 AEL for visible lasers) based on the

appropriate exposure duration. All other lasers at any

wavelength not classified as class 1 or class 2 with a power

less than 500 mW and unable to produce more than 125 mJ

in 0.25 seconds are defined as class 3b (3B). The Inter-

national Electrotechnical Commission (IEC) international

standard also has a limit on irradiance for class 3A lasers

of 25 Wm–2 (2.5 mW cm–2).

Class 4 lasers

2.4.6 Class 4 lasers are high-power lasers including

all lasers in excess of class 3 limitations. These lasers can

often be fire hazards. Both specular and diffuse reflections

are likely to be hazardous.

2.5 NOMINAL OCULAR

HAZARD DISTANCE (NOHD)

2.5.1 The NOHD is the maximum range at which the

power or energy entering the limiting aperture can exceed

the class 1 AEL. This value expresses the minimum safe

distance from which a person can directly view a laser

source without a biological damage hazard. The class 1

AEL is calculated by multiplying the MPE by the area of a

circle with a diameter of the limiting aperture (Df).

2.5.2 The following equation describes the

relationship between energy through a limiting aperture, Qf,

(effective energy) to total energy, Qo, of a Gaussian laser

EL MPE πDf

-----





×× MPE πDf

⋅⋅

-----------------------------

----

Chapter 2. Laser hazard evaluation 2-3

beam, given the 1/e beam diameter, DL, the aperture

diameter, Df, and neglecting atmospheric losses.

2.5.3 When including the effects of divergence, at-

mospheric attenuation and viewing aids (see 1.4.9, 1.5.8 to

1.5.10 and 3.7.7, respectively, for further explanation), this

equation becomes:

where G represents the effective optical gain and τ

represents the transmission of viewing aids.

2.5.4 If the class 1 AEL (the maximum safe level of

exposure) is substituted for Qf (the actual exposure that

could be received), the range, r, becomes the NOHD.

Making these substitutions and solving for NOHD results in

the following:

2.6 OPTICAL DENSITY (OD)

2.6.1 Since some lasers or laser systems may produce

energy or power millions of times that of the class 1 AEL,

the use of logarithms is the preferred method to express

personnel protection requirements. To fully specify the eye

protection requirements for a particular laser system,

unaided and aided OD values are calculated.

2.6.2 To determine the OD of eyewear required to

protect personnel from incident laser radiation, the ratio of

the effective energy, Qf, to the class 1 AEL is used as

shown:

2.6.3 To consider the effects of binoculars or other

viewing aids, the change in the effective energy will

produce different OD values and must be considered if

those viewing conditions are possible. However, the

maximum OD will never be more than:

2.6.4 This equation assumes that all laser energy is

concentrated into the limiting aperture with no transmission

loss through optics. This is the worst case condition.

2.7 OTHER FACTORS

2.7.1 In performing a laser hazard evaluation, other

issues must be considered. Things such as critical task

impairment, properly working safety interlocks, standard

operating procedures, and signs and labels are integral

factors in establishing a safe environment for laser

operation. The significance of specific control measures

depends upon the laser hazard classification. A start-up

delay, for example, should not be necessary for a class 2

laser device. Applicable national or international laser

safety standards list the control measures required for each

laser hazard class.

Buffer zones

2.7.2 With outdoor lasers, a buffer zone should be

established and utilized for each laser system. A buffer

zone is a conical volume centered on the laser’s line of

sight with its apex at the laser aperture using a specified

buffer angle. Within the buffer zone, the beam will be

contained with a very high degree of certainty. The laser

system’s buffer zone depends on the aiming accuracy and

boresight retention of the laser system. Typically, the laser

system’s buffer zone is equal to five times the system’s

aiming accuracy. The typical buffer angles for lasers used

outdoors are 10 mrad for hand-held lasers and 5 mrad for

lasers on a stable platform.

Nominal hazard zone (NHZ)

2.7.3 The volume of space defined by all locations

capable of exceeding the class 1 AEL (including the buffer

zone) is known as the nominal hazard zone (NHZ). Anyone

outside the NHZ is considered to be safe from laser

hazards. Anyone within the NHZ should be protected by

either procedural safeguards or personnel protection

equipment (e.g. laser safety goggles). Small specular

reflectors in the laser beam path can create unwanted beams

and should be considered in determining the NHZ.

----- 1e

-------







–2

–

oτeµr⋅–

⋅⋅

------------------------------1e

⋅

a2r2ϕ2

⋅+

-----------------------------







–

OHD 1

--- Df2G

×–

1n 1 AEL

QoτeµNOHD⋅–

⋅⋅

-------------------------------------------–





---------------------------------------------------------------- a

–=

D10

AEL

-----------





log=

OD 10

AEL

-----------





log=

2-4 Manual on laser emitters and flight safety

Laser-beam sensitive, laser-beam critical and

laser-beam free flight zones

2.7.4 Biologically safe exposure of the eye to a visible

laser beam can create unwanted effects that can reduce or

destroy the ability of a person to perform a task. These

effects can be very hazardous if the task is safety-critical

(e.g. landing an aircraft). Three visual interference levels

have been defined and are described in 2.7.5 and in greater

detail in 3.8. These values are as follows:

• sensitive level — 100 µW/cm2

• critical level — 5 µW/cm2

• laser beam free level — 50 nW/cm2

2.7.5 The sensitive level approximates the level at

which a person could experience severe, lingering after-

effects from exposure to a laser beam. The critical level

approximates the level to which a person could experience

significant loss of vision during exposure to a laser beam

and some residual, lingering after-effects. The laser beam

free level approximates the level at which a person would

receive a distracting glare but no after-effects. The laser

beam sensitive, critical and free flight zones are the

respective volumes of space where levels above these are

prohibited.

2.7.6 Determining the distances associated with these

visual interference levels is done the same way as when

evaluating the NOHD values. The values mentioned in

2.7.4 are substituted for the appropriate MPE, new AEL

values are determined, and the range is recalculated. Note

that these values are only relevant to visible laser beams.

These values have no meaning for wavelengths outside the

visible spectrum (400–700 nm).

Non-beam hazards

2.7.7 Although laser radiation is the most obvious

hazard associated with laser systems, many other hazards

should be considered in a laser hazard evaluation. These are

known as non-beam hazards. The following list shows

several non-beam hazards common to laser use:

• collateral radiation

• compressed gases

• confining space

•cryogenics

• electrical

• electromagnetic interference

• ergonomics

•explosion

•fire

• laser dyes

• mechanical

•noise

• toxic materials

• trailing cables/pipes

• waste disposal

•X-rays

3-1

Chapter 3

LASER BEAM BIOEFFECTS AND

THEIR HAZARDS TO FLIGHT OPERATIONS

3.1 INTRODUCTION

3.1.1 The development of the laser and the industrial

application of laser technology stand out as some of the

most significant scientific contributions of the 20th century.

Presently, lasers are found virtually everywhere, from

supermarkets and schools to satellites and operating rooms,

and have become fundamental components in consumer

products and complex industrial devices, including

sophisticated weapon systems. The accessibility of the

technology and the significant reduction in cost place lasers

at almost everyone’s disposal. Furthermore, the application

of laser technology to modern society is still emerging and

its future potential appears boundless.

3.1.2 However, if used improperly, laser energy also

poses a significant biohazard. Consequently, even the most

innocuous laser pointer can become a safety hazard, either

through direct bioeffects or by causing a disruption of

critical performance tasks in hazardous situations.

3.1.3 Not surprisingly, as lasers proliferate, an ever-

increasing number of laser beam-related incidents, some

from misadventure and others caused by intentional misuse,

have been reported. A significant number of these incidents

involve aircraft operations, both civil and military. Low-

flying helicopters, as used by police and for medical

evacuation, are particularly vulnerable, not only because of

their proximity to the ground but also because of their

proximity to ground-based lasers. In some aviation

environments, even the most trivial of laser beams have the

potential to become a lethal threat, e.g. by distraction of

aircrew during a critical phase of flight. This chapter will

elaborate on the bioeffects and damage mechanisms of

laser beam energy particularly from the perspective of its

effects on aircraft operations. However, the ongoing

development of new lasers and the continued advances in

research associated with lasers and their effects make this

a vast and still evolving area of biological science.

Therefore, this chapter will only serve to be an overview of

particular aspects of those effects, namely their bioeffects

and how they relate to aircraft operations. Other technical

publications exist that cover this topic more compre-

hensively, some of which are listed in the bibliography at

the end of this chapter.

3.1.4 Depending on power and other physical

characteristics, laser beams have the potential to generate a

variety of bioeffects, including the capacity to vapourize

biological tissue, either in part or in full, sometimes

destroying the entire organism. This chapter, however, will

be limited to those laser beam bioeffects likely to be

encountered within civilian aircraft operations and pri-

marily those affecting the skin and the eye. The major part

of this chapter will address this risk from the perspective of

its potential effect on vision, since this is the primary

aeromedical concern.

3.2 THE HAZARD

3.2.1 The spectrum of electromagnetic radiation

ranges from the shortest of cosmic rays at 10–5 nm to very

long waves in the order of 1014 nm (100 km), as associated

with communications and power sources. Each of these

wavelengths is associated with photons of varying energy.

The shorter the wavelength, the higher the energy asso-

ciated with the photons at that specific wavelength. For

tissue interactions at the atomic level, the higher the level

of energy associated with these photons, the higher the risk

for biological effects. Therefore, radiation of shorter

wavelengths has the greatest potential to be biologically

hazardous.

3.2.2 The sun is the source for most of the natural

electromagnetic radiation reaching the earth. Fortunately,

the atmosphere protects the surface of the planet from many

3-2 Manual on laser emitters and flight safety

of these wavelengths and their associated hazards, but a

significant portion of the electromagnetic spectrum still

penetrates this protective barrier to become an en-

vironmental biohazard. In addition, industrial sources can

create hazardous radiation in any environment.

3.2.3 The optical radiation portion of the

electromagnetic spectrum can interact with the human eye

and skin. Optical radiation extends from the shortest

ultraviolet wavelength, at 100 nm, through the visible

spectrum up to and including longer IR wavelengths around

1 mm (106 nm), such as those associated with radar. The

optical radiation portion of the electromagnetic spectrum

can be a biohazard when associated with visible and

invisible laser beams.

3.2.4 The International Commission on Illumination

(CIE) has divided the optical radiation portion of the

spectrum into the bands listed in Table 3-1, which include

IR, visible (VIS) and UV wavelengths:

3.2.5 The atmospheric contents normally shield the

surface of the planet from UVC radiation. Wavelengths

below 180 nm are completely blocked by the atmosphere.

Without this protection, biological life on the planet would

not be possible. Although not a naturally occurring

biological threat, any of these wavelengths can be

artificially generated and exploited by means of laser-based

technology.

3.3 BIOLOGICAL TISSUE

DAMAGE MECHANISMS

3.3.1 In order for phototoxic damage to occur in a

biological tissue, radiation must be absorbed by some

molecular constituent of that biological tissue. If the

radiation passes through the tissue without molecular

absorption, no biological damage occurs. However, most

molecules have the ability to absorb at least some portion

of the electromagnetic spectrum. It is possible to plot, for

any given tissue, those ranges of radiation (wavelengths) to

which that individual tissue is sensitive. That tissue plot

represents a summation of the individual sensitivities of all

of its constituent molecules and is known as the action

spectrum. In many cases, the action spectra of different

individual tissues have been precisely calculated and they

are associated with very specific wavelengths. Most action

spectra have been well described for the different tissue

types. A classic example of this is the action spectrum for

photokeratitis (inflammation of the cornea), which is

related to excessive ultraviolet exposure (see Figure 3-1).

Table 3-1. Optical radiation spectral bands

3.3.2 In order for biological damage to occur, a

molecule must absorb the photons emitted by the radiation

source. The Grotthus-Draper Law states that photons must

be absorbed by a molecule before a photochemical effect

can occur. The Stark-Einstein Law states that only one

photon has to be absorbed by a molecule to cause an effect.

If a photon is absorbed, then biological damage may occur

as a consequence of one of three main damage mechanisms

or any combination thereof: photochemical (photolytic),

thermal (photocoagulative) and acoustico-mechanical.

3.3.3 Within any given biological tissue, the amount

of damage that occurs represents a summation of all these

mechanisms as well as other propagated local tissue effects;

therefore, tissue damage will usually extend beyond the

immediate confines of individual molecular locations. In

some cases, tissue damage can be induced at a considerable

distance from the location of the absorbing molecules,

e.g. from oedema or vascular disruption.

Photochemical damage

3.3.4 Photochemical (photolytic) damage occurs

when the energy of an incoming photon is high enough to

break (lyse) existing chemical bonds within individual

molecules. The effect of this is to alter or destroy the

absorbing molecules and to transform them into unwanted

free radicals. A considerable amount of research and

interest continues regarding the acute and chronic tissue

effects from the generation of free radicals, regardless of

cause. A large portion of an organism’s ability to resist the

long-term consequences of tissue-free radicals that are

generated on a daily basis involves many chemical

mediators that repair this damage and remove these free

radicals from individual tissues in order to neutralize their

potential negative effects. When these damage repair

Spectral band Wavelength (nm)

UVC 100–280

UVB 280–315

UVA 315–400

VISIBLE 400–700*

IRA 700–1 400

IRB 1 400–3 000

IRC 3 000–1 000 000

* Although the visible range can be regarded to extend beyond

700 nm, usually up to 770 nm or even higher in some in-

dividuals, by convention and to maintain consistency with

other accepted international standards, the visible range will be

limited to 400–700 nm in this manual.

Chapter 3. Laser beam bioeffects and their hazards to flight operations 3-3

mechanisms or mediators cannot compensate for the rate of

free-radical generation, many acute and chronic diseases

are known to follow. Examples of these include cataracts,

macular degeneration, corneal degenerations and a variety

of degenerative skin conditions, from loss of elasticity

(wrinkles) to skin cancers.

3.3.5 The shorter the wavelength, the higher the

energy associated with those particular photons. High-

energy photons, for example UVC, have sufficient energy

to break carbon-to-carbon bonds, which are some of the

strongest biochemical bonds in living tissue. This is why

atmospheric UVC absorbers, such as oxygen, ozone, water,

carbon dioxide and other atmospheric constituents, are

critically linked to human survival on earth. Thus, it is the

energy associated with these shorter UV wavelengths that

accounts for a significant portion of the photochemical

damage seen in both the skin and the eye. In fact,

wavelengths shorter than 320 nm are regarded as the active

actinic ultraviolet range. Lasers can provide a concentrated

source of photons at virtually any wavelength and thus are

quite efficient at causing photochemical damage, either

from low-intensity long exposures or high-intensity short

exposures.

Thermal damage

3.3.6 When an inorganic or organic molecule absorbs

a photon, this additional new energy drives the molecule

into one of several types of unstable excited states, the most

unstable of which is often referred to as a triplet state.

These states are very unstable. The newly acquired level of

excess energy is usually shed quickly and these states,

therefore, are of extremely short duration. In some cases,

the release of energy occurs visibly by re-radiation of the

energy as light at another wavelength, either as

phosphorescence or fluorescence. Generally, however, this

energy is released as an exothermic reaction by giving off

heat. Depending on the amount of heat generated and the

thermal sensitivity of the surrounding tissues, if normal

thermal dissipating mechanisms fail to compensate or are

overloaded, this thermal process will then induce thermal

damage. The heat can damage surrounding proteins and

other tissues well beyond the immediate surrounds of the

absorbing molecules. This explains why the visual effects

of a retinal burn from a laser beam can be much larger than

expected from the size of the visible retinal lesion.

Acoustico-mechanical damage

3.3.7 Acoustico-mechanical damage occurs as a

consequence of high energy, short-duration exposures to

laser beams. This damage mechanism consists of several

sub-processes. These include acoustic shock waves induced

by the impact of the laser beam itself and several

consequences thereof. For example, ultra-fast elevations of

tissue temperature can generate steam bubbles in the tissue.

Mechanically, this can either destroy surrounding tissue as

Figure 3-1. Action spectrum for photokeratitis

0.2

0.4

0.6

0.8

1.2

1.4

1.6

220 230 240 250 260 270 280 290 300 310 320

Wavelength in nanometres (nm)

Threshold exposure in J/cm × 10

-2 -2

3-4 Manual on laser emitters and flight safety

a function of being a space-occupying lesion or by inducing

additional shock waves, which then propagate into and

through various neighbouring tissues inducing even further

structural damage. In addition, the ability of radiation to

create a highly ionized state of matter (plasma) in

combination with this steam-generating process can result

in a cavitation process with formation of bubbles that can

further disrupt delicate tissue structures. Such effects can be

very dramatic and may affect areas up to 200 times larger

than the thermal damage area. This cavitation process, also

called an optical breakdown, can be used quite effectively,

e.g. by a Nd:YAG laser, to create mechanical disruption of

tissue. This effect is used clinically by ophthalmologists to

cut through opacifications of the posterior capsule of the

lens (capsulotomy) which may form after extracapsular lens

extraction, to lyse tissue bands deeper in the eye and to

create holes in the iris (iridotomy) to treat angle closure

glaucoma.

3.3.8 The types of bioeffects and related tissue

damage induced by a laser beam in either the skin or the

eye are dependent on many variables, including the

physical characteristics of the laser emitter itself, the

environmental setting and the biological characteristics of

the target tissue and its surrounding structures.

3.3.9 The physical characteristics related to the laser

emitter itself are discussed in depth in Chapter 1. The most

important are:

• wavelength

• initial beam size

• power and power density

• beam divergence

• output mode (pulsed or CW)

• pulse properties (PRF, pulse width, etc.)

3.3.10 The ability of any given laser beam to induce

bioeffects and generate damage can be tempered or

enhanced by environmental factors. This is particularly

germane with respect to the eye. Such environmental

factors include:

• ambient luminance (which determines the level of

light adaptation)

• distance from laser source

• atmospheric conditions

• angle of incidence

• intervening optical interfaces

• viewing conditions (unaided or with magnification

device)

3.3.11 The individual sensitivity of any biological

tissue to any given radiation can be artificially increased

(damage threshold decreased) by the use of certain

photosensitizing agents or medications. There is a large and

growing list of assorted pharmaceutical agents, both topical

and systemic, that can make an individual more vulnerable

to biological damage in some tissues in any given setting.

In some cases, this can elevate tissue sensitivity to such a

degree that a known non-damaging level of a particular

radiation can suddenly and unexpectedly become a

significant biohazard. A list of some common photo-

sensitizers is provided in Table 3-2.

3.4 THE SKIN

3.4.1 The wavelength sensitivity range of the skin and

the eye to optical radiation are generally very similar.

While the likelihood of a skin injury is statistically higher

because the skin has a much larger vulnerable surface area

than the eye, the actual operational consequences of such

skin effects are generally trivial. Furthermore, this

vulnerability of the skin can easily be diminished by simple

protective measures, such as covering the exposed areas

with garments or chemical blocking agents. Nonetheless,

when exposed to optical radiation, the skin can suffer the

consequences, both acute and chronic, of all three

biological tissue-damage mechanisms. The typical acute

skin injury is likely to be a surface burn that may be severe

enough to require medical management. Cumulative effects

manifest themselves later in life as chronic conditions, such

as wrinkles, skin folds (e.g. cutis rhomboidalis nuchae) and

skin cancers. It is estimated that 80 per cent of the lifetime

carcinogenic exposure to UV radiation occurs before age

21. Proper UV protection should be diligently followed

from the earliest possible age; especially important is the

protection of infants.

3.4.2 It is possible to disrupt skin and entire

organisms with more powerful lasers such as those

developed for military, industrial and scientific use. It is,

however, unlikely that acute skin damage from a laser

beam will disable aircrew, either physically or

psychologically, and thus play a role in the disruption of

safe air operations. Additional information is available in

technical publications dealing with induced skin damage.

Unnecessary exposure to radiation, particularly UV, should

be avoided to reduce potential toxic cutaneous effects, both

acute and chronic. The amount of UV radiation increases

with altitude, as a general rule increasing three to four per

cent for every 300 m (1 000 ft) gain in altitude.

Chapter 3. Laser beam bioeffects and their hazards to flight operations 3-5

Table 3-2. Common photosensitizing agents

3.5 THE EYE

3.5.1 It is the acute disruption in visual performance

and the potential of laser beams to induce ocular damage that

are of paramount importance to aircrew in the performance

of their duties and which implies a threat to flight safety.

3.5.2 Optical radiation can be divided into two

general regions with respect to the potential of a laser beam

to cause damage: the retinal hazard region and the non-

retinal hazard region. The wavelengths of the retinal hazard

region include the visible and near infrared (NIR) band and

represent those wavelengths that are transmitted through

the optical media of the eye (cornea, aqueous humour, lens

and vitreous body) and are focused on the retina. This band

includes the entire visible range between 400 and 700 nm,

up to the end of the near infrared (IR-A) range at 1 400 nm.

3.5.3 The non-retinal hazard region refers to those

wavelengths that are mostly absorbed by anterior ocular

tissues (cornea and lens) without significant transmission

posteriorly to the retina. This band includes UV and the

longer IR bands, those greater than 1 400 nm (IR-B and

IR-C). Although some of the non-retinal hazard radiation

can be transmitted through some ocular tissues, almost all

of it is normally absorbed before it reaches the retina. This

absorption process, however, can also have acute and

chronic effects on the absorbing tissues themselves,

especially if normal repair capabilities are exceeded. The

classical example of this is the crystalline lens, which is the

final tissue barrier to UV radiation. It absorbs virtually all

of the residual UV radiation that passes through the cornea

and the aqueous humour.

3.5.4 This absorption process induces changes within

the lens, such as yellowing, which make it a more effective

blue-wavelength and UV filter. But the absorption may also

result in increasing opacification of the lens in the form of

nuclear and cortical sclerosis (senile cataract) that

eventually disrupts overall visual performance. Once the

lens is removed surgically, this normal barrier to UV

radiation is also removed and thus retinal tissue is now

exposed to higher levels of UV that normally would have

been absorbed by the natural lens. This necessitates

additional sun protection even in individuals with im-

planted intraocular lenses (IOL) containing UV radiation-

absorbing additives because such lenses do not reliably

protect the retina against UV radiation.

3.5.5 The characteristics of each ocular tissue with

respect to optical radiation will now be discussed in more

detail. Figure 3-2 is provided to facilitate the discussion.

The cornea

3.5.6 The multi-layered cornea is a clear ocular

structure, which contributes the bulk of the light-bending

power (refractive power) of the eye as it naturally focuses

incoming light rays on the retina. The cornea can absorb

virtually 100 per cent of UV wavelengths shorter than

280 nm (UVC). This is usually of little importance as the

atmosphere already absorbs almost all of the natural UVC,

even at the highest flight levels. Artificial sources that

generate UVC within the environment are a different

matter. The overall absorption of the UV radiation band by

the cornea decreases as the wavelength increases, so that

more and more UV radiation is gradually passed on

through the aqueous humour to the lens. At 360 nm, the

cornea absorbs about 34 per cent of the UV radiation. On

the other hand, the cornea absorbs very little of the visible

and NIR portions of the spectrum, passing over 95 per cent

of this range on to the retina as a more concentrated or

focused beam.

3.5.7 Absorption of excessive UV radiation by the

cornea can cause corneal tissue damage as a function of its

action spectrum. The classic example of this is photo-

keratitis associated with arc-welding, artificial suntanning

or exposures to high levels of environmental UV radiation,

such as that typical of snow and water activities. UV

radiation has also been identified as causing several types

of corneal degeneration often referred to as climatic droplet

keratopathies, such as Bietti’s corneal degeneration and

Labrador Keratopathy. Damage repair mechanisms and the

replicating nature of the corneal epithelium generally limit

such effects to only a temporary condition, albeit an

extremely painful one. Such exposures can be epidemic as

Antibiotics (tetracyclines)

Chlordiazepoxide (Librium®)

Chlorthiazides

Cyclamates

Furocoumarins (psoralens)

Griseofulvin

Nalidixic acid

Oestrogens/progesterones

Phenothiazines

Porphyrins (porphyria)

Sulfonamides

Sulfonylurea

Tretinoin (retinoic acid, vitamin A acid, Retin-A®)

Triacetyldiphenolisatin (laxative)

3-6 Manual on laser emitters and flight safety

described by Xenophon in Anabasis where large multitudes

of Greek soldiers at altitude were incapacitated by “solar

blindness” during an organized military retreat. However,

with very high-intensity laser beams, it is possible to induce

stromal damage deep in the cornea. This would cause

formation of a permanent corneal scar with the potential

loss of vision depending on its location. Fortunately, such

powerful UV radiation laser emitters are not readily

available.

3.5.8 UV radiation-induced corneal injury is usually

superficial, temporary and reversible. Nonetheless, it can be

very disabling and painful. A severe acute corneal lesion

could render aircrew visually incapacitated.

The aqueous humour

3.5.9 The aqueous humour is a transparent fluid with

very few floating cellular elements. It does, however,

absorb some of the UV radiation that gets through the

cornea but not in any appreciable quantities. Similarly, it

passes IR and visible radiation virtually unattenuated

through to the lens.

The lens

3.5.10 The crystalline lens provides the final focusing

element of the optical structures of the eye. While it provides

substantially less refractive power than the cornea, it is the

only dynamic focusing element with the ability to refine the

final focus on the retina. It does so automatically and almost

instantaneously. It is also, essentially, the last tissue barrier to

any of the UV radiation that penetrates the cornea and

aqueous humour. The lens absorbs increasing amounts of

UV radiation above 300 nm (UVB), such that it absorbs

approximately 50 per cent of UV radiation at 360 nm

(UVA). As addressed earlier, the penalty for providing this

final barrier of UV radiation protection for the retina is

increasing yellowing and other changes that eventually result

in opacification and cataract formation (cataractogenesis).

3.5.11 The UV radiation absorption capability of the

anterior segment of the eye results in virtually no UV

radiation shorter than 300 nm being passed into the vitreous

body and only about one to two per cent of UVB and UVA

passing through the lens. A unique window of UV radiation

transmission has been identified in the lens through which

a disproportionate amount of UV radiation at 320 nm

(UVA) is transmitted. This is of some interest but does not

represent a significant vulnerability. Since the lens is an

avascular and encapsulated structure, its ability to dissipate

heat and other damage effects is very limited, a factor

which ultimately contributes to cataract formation later in

life. The lens transmits visible and near IR radiation

virtually unattenuated but with some scatter. However, the

lens will absorb mid-infrared energy (IRB) such that it is

possible to induce lenticular damage with levels of IR

energy that are not high enough to induce corneal damage.

The lens will also absorb increasing amounts of short,

visible wavelengths (violet and blue) as it yellows with age.

The vitreous humour

3.5.12 The vitreous humour or vitreous body (corpus

vitreum) is an optically clear structure composed of

gelatinous and aqueous material with few structural fibres

and cells. It does, however, have some very limited ability

to absorb UV radiation and by design passes visible and

NIR radiation to the retina virtually without attenuation.

The retina

3.5.13 The retina contains the neural elements and

photoreceptors (rods and cones) of the visual system and it

is the prime concern with respect to phototoxic damage

induced by any optical radiation.

3.5.14 Retinal susceptibility to photolytic damage

increases as the wavelength decreases. Furthermore, the

absorption of the retinal pigment epithelium is higher in the

near UV range than in the visible range. Therefore, thermal

retinal damage can occur if UV reaches the retina in

significant amounts. While normally protected from UV by

the anterior segment of the eye, the retina is vulnerable to

UV exposure, especially from 320 nm radiation. The retinal

sensitivity to UVA radiation has also been demonstrated in

aphakic eyes.

3.5.15 The retina is uniquely configured to respond to

the narrow band of solar radiation that typically reaches the

surface of the planet, namely the visible spectrum. As

mentioned previously, that spectrum generally extends

from 400–700 nm, but the retina is particularly more

sensitive to certain wavelengths within that range. That

sensitivity peaks at approximately 555 nm (yellow-green)

due to cone sensitivity under photopic conditions (daylight)

but shifts down towards shorter wavelengths, reaching

approximately 510 nm (blue-green) at twilight, which

coincides with the peak rod sensitivity under scotopic

conditions (night). This shift between cone sensitivity and

rod sensitivity is known as the Purkinje Shift.

Chapter 3. Laser beam bioeffects and their hazards to flight operations 3-7

Figure 3-2. The anatomy of the eye

ora serrata

(anterior ending

of retina)

vitreous body

equator

anterior chamber

iris

optic nerve

lens

capsule

POSTERIOR

optic disc

ciliary

body

cornea

corneal-scleral

limbus

visual axis

pars

plana

retina

choroid

sclera

vitreous

humour

RETINA:

NTERIOR SEGMENT

(CORNEA):

Top view of left eye

1. epithelium

2. Bowman’s layer

3. stroma

4. endothelium and Descemet’s membrane

5. anterior chamber (contains the aqueous humour)

Internal limiting membrane

Nerve fiber layer

Ganglion cell layer

Inner plexiform layer

Inner nuclear layer

Outer plexiform layer

Outer nuclear layer

Rods and cones

Retinal pigment epithelium

Vitreous

Choroid

Layers of the retina

foveola

~1º

macula lutea with

fovea centralis ~5º

posterior chamber

lens

3-8 Manual on laser emitters and flight safety

3.5.16 In some cases, a physiological retinal reaction

to UV and IR radiation can be documented. While IR

radiation is generally invisible, it has been possible to

demonstrate spectral sensitivity in the human eye as high as

1 064 nm (Sliney, et al., 1976).1

3.5.17 To initiate the visual process, the retina must

absorb visible radiation. The retina is also capable of

absorbing IR radiation. This absorbable radiation (visible

and IR) defines the in-band range and classifies those

lasers that emit photons within this band as having in-band

laser threat wavelengths.

3.5.18 As mentioned previously, the potential for any

given laser beam to induce bioeffects is not only a function

of the physical characteristics of the laser beam itself, but

also of assorted environmental or atmospheric conditions

present at the time. To these variables, certain biological

characteristics of the eye must be added that also modify

damage thresholds in the eye. These include:

• pupil size

•age

• photosensitivity level

• tissue vascular supply

• clarity of the ocular media (transmission and

scatter)

• level of light adaptation

• type of tissue exposed

3.6 OCULAR LASER BEAM

DAMAGE TERMINOLOGY

There are a few specific terms relevant when addressing

laser-beam damage in an eye. These are:

a) Maximum permissible exposure (MPE). The MPE

is that level of laser beam energy below which

exposure to a laser beam is not expected to produce

adverse biological damage. There are differences in

MPE calculations depending on whether the laser

beam is pulsed or continuous. MPEs for the skin and

eye for any laser beam and exposure condition are

available in the American National Standards

Institute ANSI Z136-1-2000,2 the International

Electrotechnical Commission (IEC) 60825-1: 19983

and other related international documents.

b) Nominal ocular hazard distance (NOHD). The

NOHD is the distance from a laser beam beyond

which the MPE is not exceeded. Within the NOHD,

the MPE may be exceeded and biological damage

may be expected. It therefore defines the so-called

“safe range” from any given laser emission. That

“safe range” relates to actual biological damage and

not necessarily to disruptions in visual performance.

c) Minimal ophthalmoscopically visible lesion

(MOVL). The MOVL can be defined as the

minimal lesion caused by a laser beam exposure,

which can be seen by direct ophthalmoscopy.

Tissue damage may not be immediately apparent

and it may take over 24 hours for a lesion to

become visible. In general, the energy required to

produce an MOVL increases as a function of

distance from the fovea on the retina. Radiant

exposure and irradiance thresholds capable of

creating MOVLs have been determined for most

common laser beam wavelengths.

3.7 LASER BEAM BIOEFFECTS

3.7.1 The range of potential bioeffects associated with

laser beam illumination is a continuum of reversible and

irreversible histological damages dependent on the physical

laser beam characteristics, environmental factors and

vulnerability of the tissue.

3.7.2 It is therefore possible to define a broad range

and continuum of potential bioeffects, involving the optical

radiation range, that include both pathological damages

(either reversible or irreversible) and performance impacts,

all of which represent a threat to safe air operations

(Figure 3-3). This ranges from distraction, glare and dazzle

through flash-blindness, assorted after-images and residual

scotomas, to retinal burns, retinal hemorrhages and even an

ocular hole. It also includes physical and psychological

phenomena that may further disrupt visual and cognitive

function during a particular task. Consequently, it is not

necessary for the MPE to be exceeded or the NOHD to be

violated before a potentially significant effect will occur.

1. Sliney, D.H., R.T. Wangemann, J.K. Franks and M.L.

Wolbarsht. “Visual Sensitivity of the Eye to Infrared Laser

Radiation”. Journal of the Optical Society of America,

66(4): pp. 339–341.

2. American National Standards Institute ANSI Z136.1-2000.

“American National Standard for the Safe Use of Lasers”.

3. International Electrotechnical Commission IEC 60825-1:

1998. “Safety of Laser Products, Part 1; Equipment

Classification, Requirements, and User’s Guide”.

Chapter 3. Laser beam bioeffects and their hazards to flight operations 3-9

3.7.3 At the very minimum, any visible laser beam can

be potentially distracting and psychologically disruptive.

During a critical phase of flight, even a low-powered laser

beam could prove lethal to crew and passengers while not

having the power to cause any biological tissue damage.

3.7.4 A single exposure to a laser beam may induce

several effects at the same time. Such an exposure can be

distracting (on occasion even terrifying), induce glare or

dazzle effects, cause flash-blindness and create after-images

and scotomas, as well as being capable of creating a retinal

burn or hole or inducing an intraocular haemorrhage.

3.7.5 A laser beam capable of inducing a retinal burn

will also induce a surrounding area of oedema and other

related biological tissue damage or bioeffects that will

encompass a much broader area beyond the confines of the

actual visible lesion itself. The MOVL refers to the smallest

laser beam induced lesion that is ophthalmoscopically

visible and refers only to lesions visible with direct view

examination devices and does not extend to microscopic

examination techniques. Specialized equipment is needed

to see areas of microscopic damage induced by laser beam

exposure. However, it can be anticipated that these changes

are an ever-present part of the tissue bioeffect continuum

and are invariably present in and around any discrete laser

beam induced focal lesion. This collateral damage is

primarily due to other tissue damage mechanisms, such as

distal effects from occlusion of proximal blood supply or

oedema that disrupts adjacent cell structures and com-

presses local blood vessels.

3.7.6 Generally, the susceptibility of the human eye to

actual damage is also a function of the environmental

luminance and level of light adaptation at the time of

exposure. For example, any given laser beam would have

to be significantly more powerful to induce similar

photopic (daylight) bioeffects, such as flash-blindness,

glare, dazzle and distraction, than such an illumination

under mesopic (twilight) or scotopic (night) conditions. For

the same average power, a pulsed laser beam will have a

higher peak power and is therefore more hazardous than a

CW laser beam. However, when it comes to many of the

potential bioeffects common to all laser beams, the clinical

and subjective difference between pulsed and CW beams is

irrelevant.

3.7.7 Due to their light-collecting capability, viewing

aids, such as periscopes, telescopes and binoculars, have a

potential to increase the amount of laser radiation entering

Figure 3-3. Ranges of laser beam bioeffects

LASER

SOURCE

•Tissue

vaporization •Retinal

haemorrhage

•Ocular holes

•MOVL

•Retinal

burn

•Irreversible

scotomas

•Histological

damage

•Irreversible

scotomas

•NOHD

•MPE

•Flash-blindness

•After-images

•Reversible

scotomas

•Glare

•Dazzle

•Distraction

IRREVERSIBLE REVERSIBLE

TRANSITION ZONE

VISUAL EFFECTS

PSYCHOLOGICAL EFFECTS

Near INFRARED

DISTANCE

VISIBLE

3-10 Manual on laser emitters and flight safety

the eye, thus increasing the hazard. This would increase the

NOHD and OD requirements for eye protection. When the

beam diameter is made 50 per cent smaller, the power

density of the beam is quadrupled.

3.7.8 Imaging devices that do not provide direct

viewing of a laser beam, such as night vision goggles

(NVG) or forward looking infrared (FLIR) sensors, do not

transmit the incoming laser photons directly to the human

eye. These devices use visible photons that have been

newly generated and then multiplied using photosensitive

materials. The output of these devices is not a laser beam.

The new photons emitted out of the viewing port of such

devices are considerably different from those that actually

enter the light-gathering device. Consequently, although

such sensors and their data can be disturbed or destroyed by

a laser beam, they do provide a significant level of laser

beam eye protection along their line of sight.

3.8 LASER BEAM BIOEFFECTS

AND AIR OPERATIONS

3.8.1 This section will elaborate on the individual

features of the bioeffects continuum as they relate to the

eye and air operations. These bioeffects include:

• distraction

• glare (also referred to as dazzle)

• flash-blindness

• after-images

• scotomas

• retinal burns

• retinal haemorrhages

• globe rupture

•other

Distraction

3.8.2 When a person sees a bright light, particularly at

night, the natural reaction is to look at it. While in flight,

aircrews are particularly sensitive to unexpected bright

lights. Such a light may be perceived as representing a

potential threat, such as the prospect of a collision with

another aircraft or a ground obstacle. Pilots, because of

their extensive training in combination with normal

biological reflexes, instinctively divert their attention

toward any new unexpected light in order to assess its

significance. A distraction that occurs during a critical

phase of flight could have serious consequences unrelated

to the light source’s ability to induce actual ocular damage.

If the light is a laser beam illumination that exceeds the

MPE, then even a brief direct visualization of the laser

beam before a compensatory blink occurs could result in

irreversible biological damage, as well as acute disturb-

ances in visual performance.

3.8.3 Due to the strobe effect of some pulsed laser

beams, they can be more distracting than CW laser beams

of the same average power.

3.8.4 If the light proves to only be a trivial distraction,

attention can be rapidly refocused to the aeronautical task

at hand with little more than perhaps an inconsequential

time penalty. However, if the light is bright enough,

residual psychological and visual bioeffects can prevent

resumption of normal visual and cognitive function and

related performance tasks.

3.8.5 When a suspected laser beam exposure occurs,

experience has shown that there will be an immediate

psychological reaction as a direct consequence of what may

initially be perceived as a serious eye injury, especially if

the light is strong enough to induce persistent visual effects.

The resulting mindset will persist until some functional

vision returns but will not completely dissipate until it

resolves completely or assurances are given that no

permanent damage has occurred. Therefore, there may be a

period of time during which the exposed aircrew members

may be functionally disabled, visually and/or psycho-

logically. Reactions to such events are an unpredictable

aspect of human nature, but experience has taught us that

significant exposures to laser beams under these conditions

can result in serious psychological disruptions, inciting

panic and necessitating transfer of control of the aircraft to

the other flight crew members.

Glare and dazzle

3.8.6 Glare and dazzle are two terms often used

interchangeably that refer to temporary disruptions in

visual acquisition without biological damage. Glare can be

caused by virtually any light and is particularly disruptive

under scotopic viewing conditions, especially when the

eyes are fully dark-adapted. However, any glare source in

the cockpit is undesirable. Glare is regarded to be a source-

fixed effect, meaning that as the position of gaze shifts

away from the light source, glare effects are diminished.

Glare only occurs when the light source is on. The length

of time during which glare is in effect is not only a function

of how long the light is viewed but also of the overall dark-

adaptation state and pupil size in the target eye. Glare can

be divided into discomfort glare and disability glare.

Discomfort glare refers to glare of high enough il-

lumination that forces the viewer to turn away. Discomfort

Chapter 3. Laser beam bioeffects and their hazards to flight operations 3-11

glare tends to be exacerbated when the overall ambient

illumination is low. Disability glare refers to the inability to

see an object because of the light. Veiling glare represents

the ability of glare to impede visualization of structures

around the glare source beyond the actual size of the glare

source itself and is a more functional representation of the

true level of visual performance degradation.

3.8.7 Disability glare from an external light can be

reduced by any intervening interfaces, such as windscreens,

canopies or other optical media that scatter incident light.

Scratched or dirty spectacles, contact lenses, as well as the

cornea and crystalline lens, may also attenuate the

disability glare. However, the more scatter that occurs, the

greater the degrading effect from veiling glare.

3.8.8 Some interface materials can also reradiate at

different wavelengths; thus an invisible laser beam can

cause reradiation at a visible wavelength. This effect is not

likely to be significant outside the NOHD for the invisible

laser beam.

3.8.9 It has been shown that glare sensitivity increases

with age as it is a function of age-related changes in the

optical media, particularly the crystalline lens. In general, a

visible laser beam is a very bright light that can be an

extremely effective cause of disability glare. Laser beam

induced glare can be initiated by both CW and pulsed laser

beams, although it tends to be more of a concern with a

CW laser beam source. It also appears that within the visual

spectrum, all wavelengths have approximately the same

scattering characteristics. Consequently, all colours have

the capacity to induce glare.

Flash-blindness

3.8.10 Flash-blindness is a visual interference effect

caused by a bright light that persists after the light is

terminated. Flash-blindness persists while an eye attempts to

recover from an exposure to the bright light. The ability of

any given light source to induce flash-blindness is directly

related to the brightness of the light and the level of dark

adaptation in the target eye at the time of the exposure. It

can be shown that the brighter the environmental luminance

levels to which an eye is adapted at the time of the exposure,

the brighter the light needed to induce flash-blindness. The

corollary to this is that the brighter the light in any given

situation, the longer the ensuing flash-blindness period. This

relates directly to the ability of the eye to recover from

bleaching of the photosensitive pigments caused by the new

bright extrinsic light. During the period of recovery, the

luminance conditions of the objects being viewed as a

primary task will also determine how long it takes to

recover functionally from the flash-blindness. If the visual

task being undertaken at the time of exposure is well

illuminated, recovery times will be shorter than recovery

from poorly illuminated visual tasks. These recovery times

reflect differences between the photochemical rejuvenation

rate of rods and that of cones.

3.8.11 Flash-blindness can last from several seconds

to several minutes and has been shown to be more

prolonged in older individuals, largely based on the speed

and efficiency of recovery mechanisms and richness of

vascular supply available in the target ocular tissue. CW

and pulsed laser beams are equally adept at inducing flash-

blindness.

After-images

3.8.12 After-images refer to perceptions, or so-called

after-effects, which persist following illumination with a

bright light. They are often described as light, dark or

coloured spots following exposure. Such after-images are

essentially a type of flash-blindness, although after-image

effects may last for more prolonged periods of time, often

well beyond recovery of the ability to perform visual tasks

required while in the cockpit. After-image effects may

include colour distortion that represents selective cone

pigment depletion similar to those induced with flash-

blindness. However, after-images may persist for much

longer periods than flash-blindness and can persist from

minutes to hours or several days. They can also have

different effects depending on the characteristic of the

background under observation. Like flash-blindness, after-

images also tend to last longer in older individuals. Their

intensity, density and duration are in direct proportion to

the intensity of the instigating light.

3.8.13 After-images can occur following illumination

with both visible and invisible radiation. The latter reflects

normal retinal sensitivity to some of these wavelengths, i.e.

to some limited UV or IR bands, or is an expression of

actual biological damage.

Scotomas

3.8.14 A scotoma is an after-effect which is either

temporary (reversible) or permanent. A scotoma in its most

benign form represents a resolving residual after-image.

However, it can also be permanent and may thus reflect the

earliest sign of permanent biological tissue damage.

Scotomas typically follow flash-blindness reflecting normal

biochemical recovery of photosensitive pigments in both

rods and cones. The typical scotoma can be caused by

exposure to a bright light but can also be caused by some

non-visible wavelengths.

3-12 Manual on laser emitters and flight safety

3.8.15 A permanent scotoma can be either relative or

absolute. A relative scotoma is an area of the visual field in

which objects of a certain size, brightness or colour may be

seen while other objects that are smaller, less bright or of a

different colour are not seen. This indicates damage to the

retina but not complete loss of function. It is a reflection of

the degree of tissue damage in the immediate area or to its

vascular supply at a more distant location.

3.8.16 An absolute scotoma, on the other hand, is a

more pronounced manifestation of visual damage and

essentially represents an area of the visual field where no

object, regardless of size, colour or luminance, is visible. In

effect, it represents a part of the retina where there is no

longer any functioning neural retina remaining as a result

of direct localized tissue damage or disruption of vascular

supply or neural pathways elsewhere.

3.8.17 The visual performance ramifications of such

scotomas are related to their size and location. Even the

smallest of absolute scotomas can have devastating visual

consequences if it occurs directly in the fovea (central

vision), as opposed to a few degrees away.

3.8.18 Retinal cones mediate fine visual acuity and

are maximally concentrated in and around the fovea,

achieving their densest population in a specialized area

called the foveola. Here the visual acuity is maximal as

illustrated in Figures 3-4 and 3-5. This highest level in

cone-mediated visual acuity at that location is known as

central vision. Cone population density, however, quickly

drops off as a function of distance from the fovea,

especially outside a 10-degree radius from the fovea.

3.8.19 This cone distribution accounts for the fact that

6/6 or better visual acuity occurs within the central one

degree of the fovea, in the foveola. By five degrees away,

visual efficiency has dropped off to approximately 6/12 to

6/18 and by 10 degrees away, visual degradation reaches

6/18 to 6/24. Vision outside the fovea is referred to as

peripheral vision, which typically degrades to 6/60 to

6/120 levels as cones become less common and more

widely spaced.

3.8.20 Therefore, it is the precise location of any

permanent ocular damage relative to the fovea that will

determine the resulting level of functional visual acuity.

Any focal lesion in the eye will produce a scotoma.

Permanent scotomas are usually associated with observable

retinal lesions, but the area of scotoma may be much larger

than the size of the retinal lesion suggests because of

collateral histological damage in surrounding tissue.

Consequently, the size and location of the retinal lesion will

determine the overall visual effect of any given lesion in an

eye.

Retinal burns

3.8.21 A retinal burn represents more significant and

permanent damage induced by intense radiation and is very

characteristic of laser beam induced phototoxic damage. A

laser beam focused on the retina is more likely to cause

injury than a non-focused beam. The ability of a laser beam

to induce such damage is used as a surgical tool to treat

certain ophthalmological disorders, such as retinal tears and

diabetic retinopathy. In the latter case, approximately 1 500

deliberate retinal burns are created with an argon laser

beam to reduce the risks of retinal neovascularization that

occurs in about five percent of diabetes mellitus cases.

However, such laser beam induced events in normal eyes

are otherwise significant, unwanted occurrences. It is also

possible that other histological damage, occurring at levels

not observable ophthalmoscopically, can account for sur-

prising amounts of visual damage without an apparent

retinal burn. As mentioned previously, the size of any area

of retinal damage will generally extend beyond the confines

of the visible lesion because of the other tissue-damage

mechanisms. A small retinal burn that closes or interrupts

vascular supply or neural pathways can affect a much larger

area of retina, although collateral blood flow may temper

this effect to some degree.

3.8.22 It is the ability of a laser beam to induce a

retinal burn that is one of the most ominous unwanted

effects in a normal eye, and any resultant visual conse-

quences will be a direct function of the size and location of

the lesion.

3.8.23 Direct viewing of a high-powered laser beam

on the visual axis will cause burns that have greater visual

ramifications than off-axis burns. The retina can sustain

many small burns in the periphery without any obvious

physiological consequence. These peripheral lesions, while

not usually symptomatic, indicate the presence of a

significant laser beam exposure in the given operational

environment. In addition, a laser beam has the ability to

remain quite powerful even after reflection from shiny

surfaces, so that those whose visual attention are directed

away from the primary laser beam may still receive an on-

axis reflection from an unexpected quadrant of gaze. In

some cases, certain reflective sources, such as concave

mirrors, may concentrate the laser beam even further. Other

observations related to the ability of a laser beam to induce

a retinal burn reveals that the energy requirements to induce

such a lesion generally increase as the distance from the

fovea increases. Similarly, it has been shown that repetitive

re-exposures (multiple subthreshold exposures) in any

given area may reduce the threshold for inducing biological

damage at that location. This further supports the need to

redirect gaze immediately away from any laser beam that

enters the eye.

Chapter 3. Laser beam bioeffects and their hazards to flight operations 3-13

Figure 3-4. Visual acuity as a function of cone distribution

Figure 3-5. Visual acuity as a function of retinal location

60 40 20 0 20 40 60

Foveola

Degrees away from foveola

High-contrast Snellen acuity

6/4.5

6/6

6/7.5

6/9

6/15

6/60

6/30

20/15

20/20

20/25

20/30

20/50

20/100

20/200

Vascular arcade

Posterior pole

(area centralis):

≥

6 mm (20°)

6/30 – 6/60

Parafovea:

≥

3 mm (10°)

6/18 – 6/24

Fovea (macula):

1.5 mm (5°)

6/12 – 6/18

Foveola:

0.33 mm (1°)

6/3 – 6/6

Optic disc (physiological blind spot):

Outside posterior pole

(peripheral retina):

6/60 – 6/120

1.5 mm (5°) × 1.75 mm (7°)

3-14 Manual on laser emitters and flight safety

Retinal haemorrhages

3.8.24 A retinal haemorrhage will occur if a laser

beam disrupts a blood vessel somewhere in the eye. The

characteristics of that haemorrhage will depend on the

location of the damaged blood vessel within the retina, its

distribution and the orientation of the cell structure at the

disruption site. Haemorrhages involving superficial retinal

vessels will tend to follow the nerve fibre layer and assume

a flame-shaped configuration as the blood follows the nerve

fibres out radially from the optic nerve. Haemorrhages in

retinal layers deeper than the nerve fibre layer tend to be

dot- or blot-shaped. This blood can originate from deeper

vascular supplies, such as from the choroid (middle layer)

of the eye. It is also possible to disrupt a vessel or vascular

plexus to the extent that a large intraocular bleed occurs.

This blood may either collect on the retinal surface as a

preretinal haemorrhage or diffuse into the vitreous cavity.

Blood that enters the vitreous body will tend to remain

localized, particularly in younger individuals, but with

increasing age, the jelly-like vitreous body liquefies and

will allow blood to diffuse throughout the entire vitreous

cavity. This change in the vitreous body with age is a

normal aging process known as vitreal liquefaction, but it

may also occur as a result of other pathological processes

such as trauma.

3.8.25 A haemorrhagic event can have significant

visual impact. Recovery will depend on the location of the

bleed and other induced cytoarchitectural disruptions, as

well as the rate of reabsorption of the blood, e.g. from the

vitreous body, where it acts as a light-blocking filter. In

general, blood in the vitreous cavity will take approximately

six to twelve months to resolve spontaneously but will not

always do so. In many cases, removal of the cloudy vitreal

contents will be required surgically (vitrectomy) to restore a

clear ocular medium within the vitreous cavity. In some

cases, blood in the vitreous body will fibrose into localized

areas of vitreal opacification or induce fibrous strands that

can produce retinal traction or retinal tears.

Globe rupture

3.8.26 It is possible with a laser beam to disrupt tissue

to such an extent that neither a burn nor a haemorrhage

occurs, but rather a tear in the tissue is caused. This can be

a deleterious effect from exposure to high-peak power laser

beams of certain wavelengths. But this can also be used

therapeutically to disrupt unwanted membranes or traction

bands within the eye. Such tissue disruption may be

complete, either extending through an entire tissue layer,

such as the retina and choroid, or with more powerful laser

beams, to create a tear or hole in the entire outer coat of the

eye, the sclera-globe rupture. Such laser beams would need

to be very powerful to retain that capability at considerable

distances and would not likely be associated with laser

beams routinely encountered in civil aviation. Furthermore,

lasers of this peak power at extended ranges are likely to

have other much more significant effects that would

overshadow the eye and vision considerations.

Other bioeffects

3.8.27 In addition to the previous discussion of the

psychological and ocular effects associated with laser beam

exposures, there are other bioeffects that need to be

addressed. It is quite common in response to a perceived

bright light, particularly if it induces symptoms or a lesion,

for those affected to rub their eyes. This can induce

mechanical trauma to the cornea and conjunctiva that is

unrelated to the biological damage mechanisms of laser

beams. For example, excessive rubbing can induce con-

junctival haemorrhages and superficial epithelial lesions of

the cornea or even corneal abrasions that can induce further

symptoms and discomfort that are unrelated to, but often

attributed to, the laser beam itself. This can become even

more problematic if the rubbing occurs over contact lenses,

especially lenses made from rigid materials.

3.8.28 As a result, best corrected visual acuities and

any ocular damage must be carefully recorded in the

medical record so that a determination can be made, either

by on-scene medical examiners or by subject matter experts

who later review such cases as to cause and effect. A

corneal and retinal drawing should always be made to show

the precise location and configuration of any lesions related

to the event. This is extremely important especially since

these events invariably become medical, occupational, legal

and political controversies at some point.

3.8.29 Beyond the description of biological damage

mechanisms and related bioeffects associated with laser

beams, consideration should be given to the visual

performance ramifications of this damage from a different

perspective. Those categories of visual performance that

are related to either temporary or permanent laser beam

effects include: central visual acuity, peripheral visual

acuity, colour perception, contrast sensitivity and

stereopsis. Therefore, the consequences of specific laser

beam induced lesions must also be viewed with regard to

their ability to affect these other areas of visual

performance. In many cases, these visual functions will be

tested to determine deviations from normal and to monitor

recovery. It should be noted that colour perception

screening (which should include both red/green and

yellow/blue testing) can be particularly useful in

Chapter 3. Laser beam bioeffects and their hazards to flight operations 3-15

identifying phototoxic retinal damage and may indicate

laser beam damage even when the Amsler grid and Snellen

visual acuity tests are normal. This ability to identify

phototoxic events with colour vision tests has been shown

to exceed the ability of the Amsler grid to identify the

presence of an actual laser beam related injury. Therefore,

colour vision testing (including red/green and blue/yellow

testing) remains a significant tool to assess the level and

degree of potential damage related to any light or laser

beam exposure.

3.8.30 Individual variations in affected eyes make

accurate prediction of rate and degree of recovery almost

impossible. The closer the lesion to the macula, the greater

the likelihood of significant visual impairment, but

appearance alone is not always a good indicator of

function. Some eyes with significant lesions seen with the

ophthalmoscope have surprisingly good visual function.

Other eyes may have significantly reduced visual function

with very little to see ophthalmoscopically. The normal

retina is transparent and it is only with some of the newer

instruments, such as the confocal scanning ophthalmoscope

that subtle retinal changes can be studied. The most subtle

lesions may be impossible to detect except with electron

microscopy. Corneal lesions are somewhat easier to

evaluate clinically. As with the retina, location is critical. A

small corneal scar in the visual axis will affect vision

severely, while a dense peripheral corneal scar may have no

effect on visual acuity.

3.9 THE FUTURE

3.9.1 Although much is known about laser beam

bioeffects, the proliferation of laser technology mandates

continued research as new laser beam wavelengths and

laser characteristics are developed. Several areas of concern

related to laser beam exposure remain to be defined, such

as cumulative effects as a result of repetitive low-intensity

exposures and age-related sensitivities.

3.9.2 Another area of interest is neuroprotective

drugs. While no effective neuroprotective agents have yet

been identified, several types are being pursued in the

hopes of eliminating or decreasing retinal sensitivity to

injury from laser beam exposure.

3.9.3 On the other hand, the increasing use of a variety

of medications can potentially photosensitize the skin and

the eyes, increasing their susceptibility to phototoxic

damage. Research in this area remains difficult. It is

expensive, complicated, time consuming and would need to

encompass a huge and ever-expanding pharmacopoeia of

both natural and synthetic drugs.

3.10 MEDICAL EVALUATION OF

LASER BEAM INCIDENTS

3.10.1 The medical tools and methodologies

recommended for evaluating suspected laser beam induced

injuries are described in Chapter 7. It is extremely

important that every effort be made to promptly record all

relevant details of the exposure at the earliest opportunity

as this may have critical occupational, medical, legal and

operational value to all parties concerned. Experience

shows that in many such exposures, damage attributed to

laser beam illuminations has, in fact, another cause. The

following report gives an example of this.

On 29 November 1996, at about 6:50 p.m. local

time, the captain of an Embraer 120 sustained an

eye injury when hit by a laser beam during

approach to Los Angeles, California (United

States). The aircraft was at 6 000 feet MSL in VMC

on right base for a visual approach to runway 24R.

The captain was looking for other traffic through

the right window of the cockpit when he was struck

in his right eye by a bright blue beam of light. As

the flight continued, it became more difficult for the

captain to see with his right eye because of

increasing pain and tearing. By the time the aircraft

was established on final approach, the captain was

in so much discomfort that he relinquished the

control to the co-pilot who completed the landing.

The captain requested immediate medical attention,

and examination at a local hospital revealed

multiple flash burns to his right cornea. The captain

was also examined by specialists at Armstrong

Laboratory, Brooks AFB, San Antonio, Texas. This

examination revealed no evidence of permanent

effects from the exposure. Investigators from the

FDA attempted without success to identify the

source of the laser beam. There were no NOTAMs

in effect for laser light activity in the Los Angeles

area at the time of the incident.

(Summary of NTSB Full Narrative Report

LAX97IA056)

3.10.2 In this report, the initial diagnosis of corneal

damage (“multiple flash burns to his right cornea”) cannot

be directly attributed to a visible laser beam because light

passes through the cornea without affecting it. The damage

to the cornea was most likely caused by rubbing of the eye

in response to the light beam exposure.

3.10.3 The inability of some examiners to correctly

diagnose an injury following laser beam exposure can be

attributed to a lack of understanding of the significance of

3-16 Manual on laser emitters and flight safety

the events involved and inadequate experience with this

kind of injury. It is common for people to vigorously rub

their eyes in response to an insult they may have received,

whether it was from radiation or particulate matter. They

often do so instinctively, sometimes in a state of panic and

in such a coarse way that they induce ocular damage to the

conjunctiva and cornea. This damage can be misconstrued

as caused by the laser beam itself when, in fact, it was a

self-induced mechanical trauma after the event. It is

therefore absolutely critical, when such events occur, that

these patients be examined by subject-matter experts with

adequate experience and knowledge of laser beam injury

patterns and source characteristics. Only such experts can

definitively establish whether or not such events are related

to a laser beam exposure.

3.10.4 Physical characteristics and other historical

details related to the laser beam and exposure setting need

to be evaluated carefully. For the most part, this will be

beyond the capability of ordinary medical practioners who

lack a comprehensive background in lasers and their

bioeffects. In the absence of national laser injury

management centres, an international point of contact

should be established to help facilitate the recording of

such incidents.

References

American National Standards Institute ANSI Z136.3-1996.

“Laser Safety and the Healthcare Environment”.

Boettner, E.A. and J.R. Wolter. “Transmission of the

Ocular Media”. Investigative Ophthalmology and Visual

Science 1, pp. 776–783.

Green, R.P., R.M. Cartledge, F.E. Cheney and

A.R. Menendez. “Medical Management of Combat Laser

Eye Injuries”. USAFSAM-TR-88-21, October 1988.

[Requests can be addressed to: Freedom of Information Act

Office (FOIA), 311th CS/SCSD, 8101 Arnold Drive,

Brooks AFB, TX 78235-5367, United States.]

International Electrotechnical Commission IEC 60825-8:

1999. “Safety of Laser Products, Part 8; Guidelines for the

Safe Use of Medical Laser Equipment”.

Ivan, D.J. and H.J. O’Neill. “Laser Induced Acute Visual

and Cognitive Incapacitation of Aircrew, Protection

Management, and Cockpit Integration”. AGARDOGRAPH

AGARD-AR-354, Chapter 11: pp. 73–85, April 1998.

[Requests can be addressed to: NATO Research and

Technology Organization, BP-25, 7 Rue Ancelle, F-92201,

Neuilly-Sur-Seine, CEDEX, France.]

Lerman, S. Radiant Energy and the Eye. Macmillan

Publishing Co., Inc. New York, 1980.

Sliney, D.H. and M.L. Wolbarsht. Safety with Lasers and

Other Optical Sources — A Comprehensive Handbook.

Plenum Press, New York, 1982.

Thomas, S.R. “Review of Personnel Susceptibility to

Lasers: Simulation in Simnet-D for CTAS-2.0”. AL/OE-

TR-1994-0060, January 1994.

[Requests can be addressed to: Freedom of Information Act

Office (FOIA), 311th CS/SCSD, 8101 Arnold Drive,

Brooks AFB, TX 78235-5367, United States.]

Zuclich, J.A. and J. Taboada. “Ocular Hazard from UV

Laser Exhibiting Self-Mode-Blocking”. Applied Optics 17,

pp. 1 482–1 484.

4-1

Chapter 4

OPERATIONAL FACTORS

AND TRAINING OF AIRCREW

4.1 BACKGROUND

4.1.1 An increasing incidence of in-flight laser beam

illuminations of flight crew personnel has been reported in

recent years. Incidents have occurred primarily near

airports located in close proximity to large cities, resort

destinations and entertainment venues. Such illuminations

have resulted in aversion responses (blinking, squinting,

head movement), temporary visual impairment (TVI),

temporary vision loss (TVL), a variety of psychological

effects and evasive actions.

On 19 November 1993, at 10 p.m. local time, a

B-737 departing Las Vegas, Nevada (United States)

was struck by a green laser beam at 500 feet AGL.

The beam entered the cockpit through the co-pilot’s

window, flash-blinding both pilots for 5-10 seconds.

The co-pilot reported problems with his right eye

and needed medical attention at the end of the

flight. The captain of the flight stated as his opinion

that if the laser beam had passed through the front

windshield illuminating both pilots at a more direct

angle, they would have lost control of the aircraft.

The laser beam source was reported to have been

located at one of the hotels near the airport.

(Summary of Report of Irregularity, dated

24 November 1993)

4.1.2 During the following two years in the vicinity of

Las Vegas airport, there were more than 150 laser beam

illuminations of air carriers, regional carriers, military

aircraft and local helicopter operators, including emergency

and law enforcement operators.

On 30 October 1995, at 6:10 p.m. local time, a

B-737 was climbing through 4 500 feet AGL on

departure from Las Vegas when the first officer,

who was the flying pilot, was hit by a laser beam.

He immediately experienced eye pain and was

completely blinded in the right eye. After-image

effects also impaired vision in his left eye. He

reported that his inability to see lasted 30 seconds

and for an additional period of two minutes he was

unable to interpret any instrument indications. The

captain assumed control of the aircraft and

continued the climb.

(Summary of NTSB Aviation Accident/Incident

Database Report LAX96IA032)

4.1.3 These incidents made it clear that TVI at

illumination levels much lower than those normally

associated with physical eye injury could affect flight

safety. On 11 December 1995, a moratorium on all outdoor

laser activities in Las Vegas was declared.

4.1.4 There are two situations where outdoor laser

operations may compromise aviation safety. The first is

where the MPE is exceeded and physical injury to the eye

can occur. The second is the situation where the MPE is not

exceeded, but where there is a potential for functional

impairment, such as flash-blindness, after-image and glare

that can interfere with the visual tasks of the pilots during

critical phases of flight. The two excerpts above are

believed to be examples of the second situation.

4.1.5 There are obvious flight safety risks associated

with laser beam illumination during critical phases of flight

(especially procedures requiring steady-state turns). These

are caused by ocular, vestibular and psychological effects,

which individually or combined may lead to loss of

situational awareness (LSA). TVI leaves the pilot reliant

upon other sensory input, which may provide inadequate but

compelling information, resulting in incorrect decisions.

TVI can lead to startle, distraction, disruption, disorientation

and in extreme cases, complete incapacitation.

4.1.6 Pilots receive most of their flight information

visually, and in order to maintain situational awareness in a

4-2 Manual on laser emitters and flight safety

dynamic environment, they rely on frequent reference to

their instruments. This reliance is greater at night and

becomes total in instrument meteorological conditions

(IMC).

4.1.7 It is important to understand how trained pilots

interpret, integrate and process information without visual

reference to the outside world. Thorough instrument flight

training is a prerequisite for maintaining normal task per-

formance, information integration and situational aware-

ness when operating under instrument flight rules (IFR).

4.1.8 Pilots use a visual scan technique of glancing at,

rather than dwelling upon, the flight instruments. Pilots

construct mental images of their position in space from

information provided by the flight instruments. Spatial

orientation is maintained through the brain’s comparison of

visual inputs with a pre-existing mental model. When

conditions permit, this model is continually updated with

reference to the outside world for comparison and

processing.

4.2 SITUATIONAL AWARENESS

4.2.1 Situational awareness (SA) is the accuracy by

which a person’s perception of his environment mirrors

reality. SA is determined by several factors. Anything that

leads to a loss of SA can create a flight safety hazard. One

of the most critical factors, and the one most likely to be

affected by laser beam illumination, is spatial orientation.

4.2.2 Loss of spatial orientation is called spatial

disorientation (SD). It can be classified into three types:

• Type I (unrecognized SD) occurs when a person is

unaware of being disorientated;

• Type II (recognized SD) occurs when a person is

aware of being disorientated and is able to

compensate for it; and

• Type III (incapacitating SD) occurs when a person

is aware of being disorientated but is unable to

compensate for it.

4.2.3 A laser beam illumination may cause all three

types of SD but is most likely to cause Types II and III.

4.3 ORIENTATION IN FLIGHT

4.3.1 Orientation in flight is determined primarily by

cues provided by the following four senses:

a) Sight (vision). This is the single most important

sense for maintaining spatial orientation during

flight. When vision is impaired, spatial orientation

is degraded because motion and position cues

provided by other senses are not reliable during

flight.

Vision can be divided into peripheral and central

vision. Peripheral vision provides low resolution

but is highly sensitive to movement and light. It is

primarily concerned with the question of “where”,

thus supporting spatial orientation. Central vision

provides high resolution and colour perception but

is less sensitive to light. It is primarily concerned

with the question of “what”. With the loss of visual

orientation cues, inadequate but compelling in-

formation from other senses causes a variety of

illusions, sometimes leading to overwhelming SD.

b) Vestibular sense (sense of equilibrium). The

vestibular apparatus provides information from the

inner ear about motion and balance. In addition, the

middle ear provides information about ambient

pressure changes. Normally, visual input will

suppress input from other senses. Because flight

motion is different from that of everyday activities,

the loss of visual input is critical, as vestibular

information alone may result in illusory perception

of flight attitude and motion. For example, to

stimulate the inner ear, an angular acceleration of

0.5 to 2.2 degrees per second per second is

required. When the angular acceleration ceases,

such as when a constant rate turn has been

established, the vestibular apparatus is no longer

able to detect the turn. If visual input is absent,

pilots will not recognize that the aircraft continues

to turn.

c) Proprioception (kinaesthetic sense). A variety of

sensory nerve endings in the skin, the capsules of

joints, muscles, ligaments and deeper supporting

structures are stimulated mechanically and, hence,

are influenced by the forces acting on the body.

These proprioceptive mechano-receptors provide

useful equilibrium information based on sensation

of position and movement. The kinaesthetic sense is

better known to pilots as “seat-of-the-pants”. Alone,

the kinaesthetic perception of an aircraft’s attitude

in space is unreliable but can easily be overcome by

more vital sensory input.

d) Hearing (audition). The auditory system provides

information about sound level, pitch and direction.

Chapter 4. Operational factors and training of aircrew 4-3

Pilots learn to recognize certain sounds during

flight. For example, airflow over the windscreen

during acceleration and deceleration of the aircraft

and the change in pitch as the engine power-setting

changes can be detected.

4.3.2 Loss of visual references caused by a laser beam

illumination, coupled with inadequate information from the

vestibular apparatus, the proprioceptive mechano-receptors

and the auditory system, may result in SD (often referred to

by pilots as “vertigo”), which can lead to accidents.

Disorientation demonstration courses and laser-awareness

training are therefore recommended.

4.4 PREVENTATIVE PROCEDURES

Pre-flight procedures

• Notices to airmen (NOTAMs) should be consulted

for location and operating times of laser activities

and alternate routes should be considered.

• Aeronautical charts should be consulted for

permanent laser activities (theme parks, research

facilities, etc.).

In-flight procedures prior to entering

airspace with known laser activity

• Exterior lights should be turned on to aid ground

observers in locating and identifying aircraft.

• The autopilot should be engaged.

• One pilot should stay on instruments to minimize

the effects of a possible illumination.

• Flight deck lights should be turned on.

In-flight procedures during and after

laser beam illumination of the cockpit

4.4.1 If a pilot is exposed to a bright light suspected

to be a laser beam, the following steps are recommended to

reduce the risk unless the specific action would com-

promise flight safety:

• Look away from the light source.

• Shield eyes from the light source.

• Declare visual condition to other pilots.

• Transfer control of the aircraft to another pilot.

• Switch over to instrument flight.

• Engage autopilot.

• Manoeuvre or position the aircraft such that the

laser beam no longer illuminates the flight deck.

• Assess visual function, e.g. by reading instruments

or approach charts.

• Avoid rubbing eyes.

• Notify air traffic control (ATC) of a suspected in-

flight laser beam illumination and, if necessary,

declare an emergency.

4.4.2 It is important to notify appropriate authorities

of a suspected in-flight laser beam illumination. Upon

landing, the pilot should notify the authorities and provide

details about the incident, then seek immediate medical

evaluation, preferably by a qualified vision specialist.

Documentation of incidents and medical examinations are

covered in Chapters 6 and 7, respectively.



5-1

Chapter 5

AIRSPACE SAFETY

5.1 GENERAL

5.1.1 This chapter provides guidance for determining

and minimizing the potential adverse effects of outdoor

laser operations on aviation safety. Provisions* concerning

laser emitters and protected flight zones are contained in:

Annex 11 — Air Traffic Services

“2.17.5 Adequate steps shall be taken to prevent

emission of laser beams from adversely affecting flight

operations.”

Annex 14 — Aerodromes, Volume I — Aerodrome Design

and Operation

“Laser emissions which may endanger

the safety of aircraft

“5.3.1.2 Recommendation.— To protect the safety of

aircraft against the hazardous effects of laser emitters, the

following protected zones should be established around

aerodromes:

—a laser-beam free flight zone (LFFZ)

—a laser-beam critical flight zone (LCFZ)

—a laser-beam sensitive flight zone (LSFZ)

“Note 1.— Figures 5-10, 5-11 and 5-12 may be used to

determine the exposure levels and distances that adequately

protect flight operations.

“Note 2.— The restrictions on the use of laser beams in

the three protected flight zones, LFFZ, LCFZ and LSFZ,

refer to visible laser beams only. Laser emitters operated by

the authorities in a manner compatible with flight safety

are excluded. In all navigable air space, the irradiance

level of any laser beam, visible or invisible, is expected to

be less than or equal to the maximum permissible exposure

(MPE) unless such emission has been notified to the

authority and permission obtained.

“Note 3.— The protected flight zones are established in

order to mitigate the risk of operating laser emitters in the

vicinity of aerodromes”.

5.1.2 Contracting States may be guided by the

following text examples when controlling the hazards of

laser beam emissions or enacting regulations in accordance

with Annexes 11 and 14:

a) No person shall intentionally project, or cause to be

projected, a laser beam or other directed high

intensity light at an aircraft in such a manner as to

create a hazard to aviation safety, damage to the

aircraft or injury to its crew or passengers.

Note.— Also see Annex 14, Volume I, 5.3.1.1.

b) Any person using or planning to use lasers or other

directed high-intensity lights outdoors in such a

manner that the laser beam or other light beam may

enter navigable airspace with sufficient power to

cause an aviation hazard shall provide written

notification to the competent authority.

c) No pilot-in-command shall deliberately operate an

aircraft into a laser beam or other directed high-

intensity light beam unless flight safety is protected.

This may require mutual agreement by the operator

of the laser emitter or light source, the pilot-in-

command and the competent authority.

5.2 AIRSPACE RESTRICTIONS

5.2.1 To protect the safety of aviation in the vicinity

of aerodromes, heliports and certain other areas, such as

low-level visual flight rules (VFR) corridors, it is necessary

to protect the affected airspace against hazardous laser

* The provisions are not intended to confer any responsibility

onto airport operators.

5-2 Manual on laser emitters and flight safety

beams. For non-visible laser beams, the nominal ocular

hazard distance (NOHD) value is the sole consideration.

For visible laser beams, in addition to the NOHD, visual

disruption must also be considered.

5.2.2 According to 5.3.1.2 in Annex 14, airspace

around aerodromes should be designated as laser-beam

sensitive flight zones, laser-beam critical flight zones, and

laser-beam free flight zones, in order to prevent visible

laser beams from interfering with a pilot’s vision, even if

the maximum permissible exposure (MPE) is not exceeded.

The beam from a visible laser must not enter any zone,

when the irradiance is greater than the corresponding visual

interference level, unless adequate protective means are

employed to prevent personnel exposure. Lasers with beam

irradiances less than the MPE but exceeding the sensitive

level or critical level, may be operated in the sensitive zone

or critical zone, respectively, if adequate means are used to

prevent aircraft from entering the beam path.

Laser-beam free flight zone (LFFZ)

5.2.3 The LFFZ is the airspace in the immediate

proximity to the aerodrome, up to and including 600 m

(2 000 ft) above ground level (AGL), extending 3 700 m

(2 NM) in all directions measured from the runway centre

line, plus a 5 600 m (3 NM) extension, 750 m (2 500 ft) on

each side of the extended runway centre line of each

useable runway. Within this zone, the intensity of laser

light is restricted to a level that is unlikely to cause any

visual disruption. The following conditions are applicable

to LFFZ:

a) parallel runways are measured from the runway

centre line toward the outermost edges, plus the

airspace between runway centre lines;

b) within this airspace, the irradiance is not to exceed

50 nW/cm2 unless some form of mitigation is

applied. The level of brightness thus produced is

indistinguishable from background ambient light;

and

c) to allow laser operations below the arrival path, a

1:40 slope may be applied to the 5 600 m exten-

sions. This slope is calculated from the runway

threshold.

Laser-beam critical flight zone (LCFZ)

5.2.4 The LCFZ is the airspace within 18 500 m

(10 NM) of the aerodrome reference point (ARP), from the

surface up to and including 3 050 m (10 000 ft) AGL (see

Figures 5-1, 5-2 and 5-3). This zone may have to be

adjusted to meet air traffic requirements. Within this

airspace the irradiance is not to exceed 5 µW/cm2 unless

some form of mitigation is applied. Although capable of

causing glare effects, this irradiance will not produce a

level of brightness sufficient to cause flash-blindness or

after-image effects.

Laser-beam sensitive flight zone (LSFZ)

5.2.5 The LSFZ is the airspace outside the LFFZ and

LCFZ where the irradiance is not to exceed 100 µW/cm2

unless some form of mitigation is applied. The level of

brightness thus produced may begin to produce flash-

blindness or after-image effects of short duration; however,

this limit will provide protection from serious effects. The

LSFZ need not necessarily be contiguous with the other

flight zones.

Normal flight zone (NFZ)

5.2.6 The NFZ is any navigable airspace not defined

as LFFZ, LCFZ or LSFZ. The NFZ must be protected from

laser radiation capable of causing biological damage to the

eye.

5.2.7 Figures 5-1 through 5-3 define the zones

established to protect aircraft in navigable airspace. The

dimensions indicated are given as guidance but have been

found to protect safety well.

5.2.8 The amount of airspace affected by a laser

operation varies with the laser systems output power, which

is measured in watts or joules. The following maximum

irradiance levels (MILs) can be used for evaluating laser

activities in close proximity to an aerodrome:

a) LFFZ: MIL is equal to or less than 50 nW/cm2;

b) LCFZ: MIL is equal to or less than 5 µW/cm2;

c) LSFZ: MIL is equal to or less than 100 µW/cm2;

and

d) NFZ: MIL is equal to or less than the MPE for CW

or pulsed lasers.

Note.— Items a), b) and c) refer to visible laser

emissions only.

Chapter 5. Airspace safety 5-3

Figure 5-1. Protected flight zones

Figure 5-2. Multiple runway laser-beam free flight zone (LFFZ)

To be determined by

local aerodrome

operations

Aerodrome

reference

point

Laser-beam

free flight

zone

18 500 m

Laser-beam

sensitive

flight zone

Laser-beam

critical

flight zone

Note.— The dimensions indicated are given as guidance only.

3 700 m

9 300 m

5 600 m

3 700 m

9 300 m

3 700 m

1 500 m

Note.— The dimensions indicated are given as guidance onl

5-4 Manual on laser emitters and flight safety

5.2.9 Protective means (mitigation) are required to

protect pilots and other personnel when the visual

interference level is exceeded. Redundant systems are

advisable in locations noted for heavy air traffic.

5.3 AERONAUTICAL ASSESSMENT

5.3.1 The procedures outlined below may be used to

evaluate the potential effect of laser activity on aircraft

operations. The proponent should notify the competent

authority in sufficient time to allow an aeronautical assess-

ment to be completed.

5.3.2 A Contracting State may provide a submission

form which, when completed, will provide sufficient

information for an aeronautical assessment to be

completed. A sample “Notice of Proposal to Conduct

Outdoor Laser Operations” form and instructions are

attached in Appendix A. The competent authority should:

a) determine the location of the laser activity and the

laser MPE and NOHD;

b) plot the LFFZs, LCFZs and LSFZs at aerodromes;

c) establish additional LSFZs, if required, to protect

locations of aviation activity that may also be

affected, such as substantial helicopter traffic

operating below 300 m (1 000 ft), VFR corridors,

the airspace around high-energy lasers used to

support astronomical observatories, active training

areas, etc.;

d) consider the laser operations in relationship with

the established zones. Use the MILs established by

the competent authority when evaluating laser

activities in proximity to an aerodrome;

e) review airspace and aircraft operations that may be

affected by the proposal;

f) coordinate with local officials, e.g. aerodrome

managers, air traffic managers, military represen-

tatives, local police organizations;

g) convene a local laser working group (LLWG) if the

operations appear to be complex or controversial;

h) consider the proponent’s proposed mitigation

measures and any additional measures taken to

Figure 5-3. Protected flight zones with indication of maximum

irradiance levels for visible laser beams

To be

determined

To be

determined

5 600 m 3 700 m

18 500 m 18 500 m

Aerodrome reference point

AGL is based on published aerodrome elevation

600 m

AGL

600 m

AGL

2 400 m AGL

To be determined by

local aerodrome operations

To be determined by

local aerodrome operations

PROTECTED FLIGHT ZONES

Elevation

Laser-beam critical flight zone

5 W/cm

Laser-beam free flight zone

50 nW/cm

Laser-beam sensitive flight zone

100 W/cm

Chapter 5. Airspace safety 5-5

ensure that aircraft operators will not be exposed to

laser emissions that have the potential to impair

their performance of duties. Such measures include,

but are not limited to, physical, procedural, manual

and automated control measures;

i) compile a cumulative impact assessment on per-

manent or long-term laser operations effects on

local operations;

j) assess the capability of the affected ATC facilities

to provide real-time management of air traffic to

ensure no cockpit illuminations by the laser beams;

k) coordinate with the proponent, identify objection-

able effects and negotiate appropriate mitigation to

protect aviation safety; and

l) communicate to the proponent and all participating

authorities the completed aeronautical assessment.

If the proposal is complex or controversial, the

competent authority should document all pertinent

information and disseminate copies as appropriate.

5.4 CONTROL MEASURES

Physical, procedural and automated control measures

established to ensure that aircraft operations will not be

exposed to levels of illumination greater than the respective

MILs considered acceptable should meet one or more of the

descriptions listed below:

a) ATC control measures:

1) NOTAM;

2) Voice advisory (e.g. automatic terminal

information system (ATIS), pilot-controller

communications);

3) Airspace restrictions;

whereas the proponent must ensure that the operator control

measures are in accordance with one or more of the

following:

b) Operator control measures:

1) The laser beam may be physically blocked

(terminated beam) to prevent laser light from

being directed into protected volumes of

airspace.

2) The laser beam divergence and output power or

pulse energy emitted through the system

aperture may be adjusted to meet appropriate

exposure levels.

3) Beams can be directed in a specific area.

Directions should be specified by giving

bearing in the azimuth scale 0–360 degrees and

elevation in degrees ranging from 0–90 degrees,

where 0 degrees is horizontal and 90 degrees is

vertical. Both true and magnetic bearings

should be given.

4) Manual operation of a shutter or beam-

termination system can be used in conjunction

with airspace observers. Observers should be

trained and able to see sufficient airspace

surrounding beam paths to terminate the beam

prior to illumination of aircraft.

5) Scanning the laser beam may reduce the level

of illumination; however, it may increase the

potential risk of illumination.

6) Automated systems designed to detect aircraft

and automatically terminate or redirect the

beam or shutter the system may be used. The

proponent should include detailed information

that describes the operation of the automated

system, its effectiveness and how it can be

tested for full functionality prior to each use.

5.5 DETERMINATIONS

5.5.1 If the proponent’s notification satisfies the

requirements of the aeronautical assessment, the competent

authority should issue, as a minimum, the following:

a) a statement advising the proponent that his

notification satisfies the requirements of the

competent authority and is approved subject to

conditions or limitations (such as aircraft spotter

requirements), as applicable;

b) a statement to the proponent that changes should

not be incorporated into the proposed activity once

permission has been granted, unless approved by

the competent authority in writing;

c) a statement that the proponent notify the

appropriate authority or their designated represen-

tative of any changes to show start/stop times or

cancellation 24 hours in advance;

5-6 Manual on laser emitters and flight safety

d) a statement that approval does not relieve the

sponsor or operator of responsibility for complying

with the mitigation agreed upon, the laws, ordin-

ances or regulations of any relevant authority; and

e) NOTAM. (See examples in 5.5.4.)

5.5.2 If the proponent’s notification does not satisfy

the requirements of the aeronautical assessment, the

competent authority should issue a statement advising the

proponent that an objection is being issued. Specifically, it

should indicate why the proponent does not satisfy safety

requirements, and that new data or other appropriate

information may be submitted for consideration. If

negotiations to resolve any objectionable effects have not

been successful, the objection should stand.

5.5.3 To enhance aviation safety, a NOTAM should be

prepared alerting pilots of known laser activities. It is

important to emphasize the hazardous effects and other

related phenomena that may be caused by laser beams.

5.5.4 The competent authority should provide

information for the publication of a NOTAM* as shown in

the following sample formats. Laser activities that last

more than 180 days should be considered permanent (e.g.

annual ongoing activities). Information pertaining to such

activities should be published in applicable aviation

publications.

Sample publication format

of temporary laser activity

LASER LIGHT DEMONSTRATION WILL BE

CONDUCTED AT (place, city, province or state),

(NAVAID ID, type, radial) RADIAL (dist.) NAUTICAL

MILES, (lat./long.). BEAMS FROM SITE PROJECTING

(direction) BETWEEN RADIALS (xxx-xxx), ON (dates),

BETWEEN (time/UTC). LASER LIGHT BEAMS MAY

BE INJURIOUS TO PILOTS/AIRCREW AND

PASSENGERS EYES WITHIN (nominal ocular hazard

distance) VERTICALLY AND/OR (nominal ocular hazard

distance) LATERALLY OF THE LIGHT SOURCE.

FLASH-BLINDNESS OR COCKPIT ILLUMINATION

MAY OCCUR BEYOND THESE DISTANCES.

LASER RESEARCH WILL BE CONDUCTED AT (place,

city, province or state, lat./long.), ON/FROM (dates),

BETWEEN (times/UTC), AT AN ANGLE OF (degree),

FROM THE SURFACE, PROJECTING UP TO (height)

MSL AVOID AIRBORNE HAZARD BY (NM). THIS

LASER LIGHT BEAM MAY BE INJURIOUS TO

PILOTS/AIRCREW AND PASSENGERS EYES.

AIRBORNE TO GROUND LASER ACTIVITY WILL BE

CONDUCTED ON (dates), BETWEEN (lat./long.,

altitude) AND BELOW. AVOID AIRBORNE HAZARD

BY (NM). THIS LASER BEAM MAY BE INJURIOUS

TO PILOTS/AIRCREW AND PASSENGERS EYES.

AIRBORNE LASER ACTIVITY WILL BE

CONDUCTED ON/FROM (dates), AT/FROM (times/

UTC), BETWEEN (NAVAID ID, type, radial) RADIAL

(dist.) NAUTICAL MILES, (lat./long.), AND (NAVAID

ID, type, radial) RADIAL (dist.) NAUTICAL MILES, (lat./

long.), BETWEEN (altitude) MSL AND (altitude) MSL (or

the surface). AVOID AIRBORNE HAZARD BY (NM).

THE LASER LIGHT BEAM MAY BE INJURIOUS TO

PILOTS/AIRCREW AND PASSENGERS.

Sample publication format

of a permanent laser site

(place, city, province or state).

UNTIL FURTHER NOTICE A LASER LIGHT

DEMONSTRATION WILL BE CONDUCTED NIGHTLY

BETWEEN SUNDOWN AND DAWN AT THE (place,

city, province or state) (NAVAID ID, type radial) RADIAL

AT LAT./LONG. RANDOM BEAMS ILLUMINATING

(directions indicated) QUADRANTS. THE BEAM MAY

BE INJURIOUS TO EYES IF VIEWED WITHIN (NOHD

dist.) VERTICALLY AND (NOHD dist.) LATERALLY OF

THE LIGHT SOURCE. FLASH-BLINDNESS OR

COCKPIT ILLUMINATION MAY OCCUR BEYOND

THESE DISTANCES.

NOTAMs concerning temporary laser activity at

Harboøre in København FIR (issued by the Civil

Aviation Administration, Denmark)

XXXXX/XX NOTAMN

Q) EKDK/QWXXX/V/B/W/000/103/

A) EKDK B) 0006091900 C) 0006102200

D) DAILY 1900-2200

E) TEMPO NAV WRNG. LASER LIGHTSHOW WILL

TAKE PLACE AT HARBOOERE PSN 563713N

0081130E. THE LASERBEAM MAY CAUSE

BLINDNESS IF VIEWED WITHIN A VERTICAL

DISTANCE OF 500FT AND HORIZONTAL DISTANCE

* More information about the NOTAM format can be found in

Annex 15.

Chapter 5. Airspace safety 5-7

OF 0.5NM OF THE LIGHT SOURCE.

FLASHBLINDNESS OR COCKPIT ILLUMINATION

MAY OCCUR WITHIN A VERTICAL DISTANCE OF

8300FT AND A HORIZONTAL DISTANCE OF 8NM

F) GND

G) 8300FT MSL

XXXXX/XX NOTAMN

Q) EKDK/QWXXX/V/B/W/000/103/

A) EKDK B) 0006091900 C) 0006102200

D) DAILY 1900-2200

E) TEMPO NAV WRNG. AIRBORNE TO GROUND

LASER ACTIVITY WILL TAKE PLACE WITHIN A

10NM RADIUS OF HARBOOERE PSN 563713N

0081130E. THE LASERBEAM WILL OPERATE FROM

10,000FT MSL DOWNWARD AND MAY CAUSE

BLINDNESS IF VIEWED WITHIN A VERTICAL

DISTANCE OF 5000FT AND HORIZONTAL DISTANCE

OF 2.5NM OF THE LIGHT SOURCE.

FLASHBLINDNESS OR COCKPIT ILLUMINATION

MAY OCCUR WITHIN A VERTICAL DISTANCE OF

5300FT AND A HORIZONTAL DISTANCE OF 8NM

F) GND

G) 8300FT MSL

5.6 INCIDENT-REPORTING REQUIREMENTS

Contracting States may wish to establish an incident-

reporting system to provide a means of monitoring

unauthorized use of lasers in airspace. Rapid notification

of an incident will assist in the investigation and possible

enforcement action against the offender. Sample incident

report formats are found in Appendix B.



6-1

Chapter 6

DOCUMENTATION OF INCIDENTS

AFTER SUSPECTED LASER BEAM ILLUMINATION

6.1 BACKGROUND

Laser beams with the potential to compromise flight safety

may be visible or invisible. Laser beams may cause damage

to the retina, especially at higher levels of exposure. The

bright light from visible laser beams can cause glare, after-

images and flash-blindness. Exposure to invisible laser

beams may result in pain, vision loss or skin burns, but they

are not normally associated with glare and flash-blindness.

Damage to the tissue of the eye’s cornea and conjunctiva

requires a higher exposure level than that required to cause

damage to the retina. This is due, in part, to the eye’s

natural focusing mechanism that can increase the energy

per unit area delivered to the retina. Besides glare, flash-

blindness and after-images, other symptoms of laser beam

light exposure may include pain, eye fatigue, tearing, eye

irritation and headache. Laser beam light can and has

interfered with safe and efficient performance of flight

procedures by causing temporary distraction, disorientation

and visual incapacitation.

6.2 PROCEDURES

Whenever an unexpected illumination by an unknown

source occurs, a laser incident should be suspected and

reported. It is recommended that all suspected laser beam

incidents be reported to the national aviation medicine and

flight safety authorities. In general, individuals should,

without delay, consult an optometrist, ophthalmologist or

designated medical examiner whenever they have

experienced a suspected laser beam exposure. Those with

persistent symptoms or abnormal clinical findings may

require referral to an ophthalmologist for further medical

evaluation and treatment.

Note.— Chapter 7, entitled “Medical Examination

Following Suspected Laser Beam Illumination”, provides

guidance for evaluating aircrew and other aviation per-

sonnel who may have been injured or incapacitated by a

laser beam illumination.

6.3 DOCUMENTATION

6.3.1 Documentation of a suspected laser beam

illumination incident has three important functions. First, it

provides information on the effectiveness of current

policies and procedures used to protect the navigable

airspace against hazardous laser beams. Second, it provides

a protocol for medical assessment. Third, it provides

updates on new devices or sources of hazardous laser

beams that may affect visual performance.

6.3.2 Guidance on how to document suspected laser

beam illumination incidents is provided in Appendix B.

The two forms (Suspected Laser Beam Incident Report and

Suspected Laser Beam Exposure Questionnaire) may be

used for investigation of illumination incidents. The report

should be completed by the illuminated persons as soon as

possible after the incident. The questionnaire may be used

by an official of the competent authority during the initial

interview.



7-1

Chapter 7

MEDICAL EXAMINATION FOLLOWING

SUSPECTED LASER BEAM ILLUMINATION

7.1 GENERAL

7.1.1 All cases of suspected laser beam exposure

should be promptly reported to the medical section of the

competent authority. In cases of suspected laser beam

exposure, two forms should be used:

a) Suspected Laser Beam Incident Report. This form

is to be completed by the persons illuminated.

b) Suspected Laser Beam Exposure Questionnaire.

This form may be used by the competent authority

during the initial interview of an exposed person.

Note.— Samples of these two forms can be found in

Appendix B.

7.1.2 The following information provides guidance

for the medical examination and evaluation of those who

may have been exposed to a laser beam.

7.2 PROCEDURE

7.2.1 A basic ocular examination should be performed

on any person suspected of having been exposed to a laser

beam to verify that no permanent damage has occurred and

to confirm normal ocular health. An optometrist, ophthal-

mologist or a designated medical examiner may complete

the basic examination.

Basic ocular examination

• History (review Suspected Laser Beam Exposure

Questionnaire, if available)

• External examination

• Best corrected visual acuity (near and far) in each

eye separately

• Amsler grid for each eye separately (see

Appendix C)

• Stereopsis (specify test used)

• Colour-vision testing with pseudoisochromatic

plates of each eye separately

• Confrontation visual fields of each eye separately

• Nondilated funduscopy on each eye separately

7.2.2 If the results of this examination are normal and

the person does not have persistent visual complaints,

further examinations are not necessary.

7.2.3 If the results of the basic examination are

abnormal or questionable, an intermediate ocular exam-

ination to assess the condition of the person’s eyes should

be performed. An optometrist or an ophthalmologist may

complete the intermediate examination.

Intermediate ocular examination

• Pupils of each eye separately

• Slit lamp of each eye separately

• Automated visual fields of each eye separately

• Motility (ductions and versions; cover test)

• Dilated funduscopy on each eye separately

7.2.4 If the results of this examination are normal and

the person does not have persistent visual complaints,

further examinations are not necessary.

7.2.5 If the results of the intermediate ocular

examination are abnormal or if visual complaints persist,

the person should be referred to an ophthalmologist

(preferably a retinal specialist), as advised by the aviation

medicine section of the competent authority. This

ophthalmologist should conduct an advanced ocular

examination.

7-2 Manual on laser emitters and flight safety

Advanced ocular examination

• Retinal photography

• Comprehensive testing of colour vision (to include

blue/yellow tests)

• Electrodiagnostic tests, as needed

• Scanning laser ophthalmoscopy, as needed

• Fluorescein angiography, as needed

A-1

Appendix A

NOTICE OF PROPOSAL TO CONDUCT

OUTDOOR LASER OPERATION(S)

Note.— The sample form below was adapted by ICAO and reproduced with the permission of the Federal Aviation Administration.

NOTICE OF PROPOSAL TO CONDUCT OUTDOOR LASER OPERATION(S)

1. GENERAL INFORMATION

2. BRIEF DESCRIPTION OF OPERATION

3. ON-SITE OPERATION INFORMATION

4. ATTACHMENTS

5. DESIGNATED CONTACT PERSON (if further information is needed)

To : (Competent Authority) From: (Applicant) Report date:

Event or facility

Customer Site address

GEOGRAPHIC LOCATION

Latitude ________ deg (

) ________ min (′)________ sec (″)Longitude ________ deg (

) ________ min (′)________ sec (″)

Ground elevation at site

(above Mean Sea Level)

Laser elevation above ground

(if on buildings, etc.)

Determined by: G GPS G Map G Other

(specify)

DATE(S) AND TIME(S) OF LASER OPERATION

Testing and alignment Operation

Operator(s)

On-site phone #1 On-site phone #2

BRIEF DESCRIPTION OF CONTROL MEASURES

Number of laser configurations [Fill out one copy of page 2 of this notice (“Laser Configuration”) for each configuration.]

List any additional attachments needed to evaluate this operation (could include maps, diagrams, and details of control measures).

Name Position

Phone Fax E-mail

STATEMENT OF ACCURACY

To the best of my knowledge, the information provided in this Notice of Proposal is accurate and correct.

Name (if different from contact person) Position

Signature Date

A-2 Manual on laser emitters and flight safety

LASER CONFIGURATION

Fill out one copy of this form for each laser or laser configuration used at the Outdoor Laser Operations site.

1. CONFIGURATION INFORMATION

2. BEAM CHARACTERISTICS AND CALCULATIONS (check one Mode of Operation only, and fill in only that column)

3. BEAM DIRECTION(S)

4. DISTANCES CALCULATED FROM ABOVE DATA

4. (Fill in all three columns for NOHD. If a visible laser, fill in all three columns for SZED, CZED, and LFED.)

5. CALCULATION METHOD

Name of event/facility This page is configuration number _____ of _____ Report date

Brief description of configuration

Mode of Operation G Single pulse G Continuous wave G Repetitively pulsed

Laser Type

(lasing medium)

Power

Watts (W)

(not applicable) Maximum power Average power

Pulse Energy

Joules (J)

(not applicable)

Pulse Width

Seconds (s)

(not applicable)

Pulse Repetition Frequency

Hertz (Hz)

(not applicable) (not applicable)

Beam Diameter @ 1/e points

Centimetres (cm) (not mm)

Beam Divergence 1/e @ full angle

Milliradians (mrad)

Wavelength(s)

Nanometres (nm)

MAXIMUM PERMISSIBLE EXPOSURE (MPE) CALCULATIONS (will be used to calculate NOHD)

MPE

W/cm2

(not applicable)

MPE per pulse

J/cm2

(not applicable)

VISUAL EFFECT CALCULATIONS (will be used only for visible lasers to calculate SZED, CZED and LFED)

Pre-corrected Power (PCP)

Watts (W)

Pulse Energy (J)*4Maximum Power (from above) Average Power OR Pulse Energy

(J) x PRF (Hz)

Visual Correction Factor (VCF)

Enter “1.0” or use Table 5

Visually Corrected Power

PCP x VCF

Azimuth (degrees) G True G Magnetic Magnetic variation (degrees)

Minimum elevation angle (degrees, where horizontal = 0°) Maximum elevation angle (degrees)

Slant range (ft) Horizontal distance (ft) Vertical distance (ft)

NOMINAL OCULAR HAZARD DISTANCE

NOHD (based on MPE)

VISUAL EFFECT DISTANCES

If the laser has no wavelengths in the visible range (400–700 nm), enter “N/A (non-visible laser)” in all blocks below.

For visible lasers, if the calculated visual effect distance is less (shorter distance) than the NOHD, you must enter “Less than NOHD”.

SZED (for 100

W/cm2 level)

CZED (for 5

W/cm2 level)

LFED (for 50 nW/cm2 level)

G Commercial software (print product name) G Other [describe method (spreadsheet, calculator, etc.)]

Appendix A A-3

The information in this form will be used by the Competent Authority to perform an aeronautical study to evaluate the safety

of a proposed laser operation. Provide all information that the Authority may need to perform the study. If additional details

are necessary, list these in the “Attachments” section of this form.

To: Enter the name, address, phone and fax of the Competent Authority’s Office responsible for the area which includes the

laser operation site. (A list of Offices is available at the end of these instructions.)

From: Enter the name, address, phone, fax, and E-mail of the applicant. This is the party primarily responsible for the laser

safety of this operation. In some cases, the applicant is a manufacturer or a governmental agency, and the laser is located at

a different site. In such a case, list the applicant here; the site location is filled in elsewhere in the form.

Report date: This is the date the report is prepared or sent to the Authority. It is not the date of the laser operation.

1. GENERAL INFORMATION

Event or facility: Enter the event name (for temporary shows) or the facility name (for permanent installations).

Customer: If the laser user is different from the applicant, fill in the “Customer” section; if not, enter “Same as applicant”.

Site address: Street address, city, province or state.

GEOGRAPHIC LOCATION

Latitude and longitude: Be sure that latitude and longitude are specified in degrees, minutes and seconds. Some maps or

devices may give this information in “Degrees.Decimal” form; this must be converted into degrees, minutes and seconds.

Ground elevation at site: This is the elevation in feet above Mean Sea Level, at the show site. It can be found on a

topographic map or other resource.

Laser elevation above ground: If the laser is on a building or other elevated structure, enter the laser’s height in feet above

the ground.

Note.— For lasers on aircraft or spacecraft, attach additional information on the flight locations and altitudes.

DATE(S) AND TIME(S) OF LASER OPERATION

Testing and alignment: Enter the date(s) and time(s) during which testing and alignment procedures will take place.

Operation: Enter the date(s) and time(s) during which laser light will enter airspace.

2. BRIEF DESCRIPTION OF OPERATION

This should be a general overview. Specific laser configurations at the operation are described in detail using the Laser

Configuration form on page 2. If necessary, attach additional pages.

3. ON-SITE OPERATION INFORMATION

Operator(s): List names and/or titles of operators.

INSTRUCTIONS FOR FILLING OUT NOTICE OF PROPOSAL FORM (page 1)

A-4 Manual on laser emitters and flight safety

On-site phones: There should be at least one working, direct phone link to the operator, or equivalent way of quickly

reaching the operator (e.g. phoning to a central station that reaches the operator via radio). Two telephone numbers are listed

on the form, so one can be used as an alternate or backup.

BRIEF DESCRIPTION OF CONTROL MEASURES

Describe the control measure(s) used to protect airspace; for example, termination on a building (where the beam path is not

accessible by aircraft including helicopters), use of observers, use of radar and imaging equipment, physical methods of

limiting the beam path, etc. The more that the operation relies on the control measures to ensure safety, the more detailed

the description should be.

4. ATTACHMENTS

Number of laser configurations: List how many “Laser Configurations” you are submitting with this proposal. If a

particular set-up operates with more than one laser, with different beam characteristics (power settings, pulse modes,

divergence, etc.) or has multiple output devices (example: projector heads), then each should be analysed as a separate Laser

Configuration using the form on page 2.

List additional attachments: You may need to add attachments such as maps, diagrams and details of control measures.

Include whatever materials you feel are necessary to assist the Authority in sufficiently evaluating your proposal.

5. DESIGNATED CONTACT PERSON

This is the person whom the Authority will contact if additional information is needed. This should be the person with the

most knowledge about laser safety at this operation. However, it could also be a central contact person who interfaces

between the Authority and the laser operation personnel. The Designated Contact Person must work for or represent the

applicant listed in the “From:” area at the top of the form.

STATEMENT OF ACCURACY

The Designated Contact Person should sign the form. However, in some cases the responsibility for the accuracy of the

information may rest with another person, such as a Laser Safety Officer who is not acting as the contact. Therefore, the

person who has the authority to bind the applicant must sign the form.

A single outdoor operation may have a number of lasers or “laser configurations” — power settings, pulse modes, divergence,

etc. On the Notice of Proposal form (page 1), in the first row of the Attachments table, enter the number of different laser

configurations for the outdoor operation. Then, fill out one Laser Configuration form (page 2) for each different configuration

to be analysed.

Alternative analysis: This form and accompanying tables must cover a wide variety of laser configurations. They are

necessarily simplified, and they make conservative assumptions. Some laser configurations may warrant a more complex

analysis. Any such alternative analysis should be based on established methods. Both the methods and the calculations must

be documented. (See ICAO Doc 9815 for further information.)

1. CONFIGURATION INFORMATION

Brief description of configuration: Describe the beam projecting or directing system. Include description of site layout.

Attach additional information if more space is required.

INSTRUCTIONS FOR FILLING OUT LASER CONFIGURATION FORM (page 2)

Appendix A A-5

2. BEAM CHARACTERISTICS AND CALCULATIONS

This section requires data about the laser beam’s characteristics. The data can be obtained from direct measurement,

manufacturer specifications or specialized instruments. You can also derive data by making reasonable, conservative

assumptions (for example, that a certain value makes the beam more hazardous than it would be in reality). All data should

err on the side of safety. In borderline situations where data accuracy is crucial to compliance, provide additional data on

measurement techniques, data sources and assumptions.

Mode of operation: Determine the mode of operation for this configuration: Single Pulse, Continuous Wave, or Repetitively

Pulsed. Put a check in the appropriate column. Fill out only that column for the remainder of this Beam Characteristics and

Calculations section.

• Single Pulse: Lasers that produce a single pulse of energy with a pulse width <0.25 seconds or a pulse repetition

frequency <1 Hz.

• Continuous Wave: A laser that produces a continuous (non-pulsed) output for a period >0.25 seconds.

• Repetitively Pulsed: Lasers that produce recurring pulses of energy at a frequency of 1 Hz or faster.

Note on “repetitively pulsed” vs. scanning: “Repetitively pulsed” refers to lasers that naturally emit repetitive pulses,

such as Q-switched lasers. The form and tables are not intended for analysing pulses due to scanning the beam over a viewer

or aircraft (examples: graphics or beam patterns used in laser displays; scanned patterns used for LIDAR). Pulses resulting

from scanning are often extremely variable in pulse width and duration. Therefore, for a conservative analysis, assume the

beam is static (non-scanned). Should you rely on scanning to be in compliance, you must 1) provide a more comprehensive

analysis, documenting your methods and calculations, and 2) document and use scan-failure protection devices.

Laser Type: Enter the lasing medium, for example, “Argon”, “Nd:YAG”, “Copper-vapour”, “CO2”, etc.

Power: If a continuous wave laser (Column 2), fill in the power in watts. If a repetitively pulsed laser (Column 3), fill in

the average power in watts [energy per pulse (J) × pulse repetition frequency (Hz)]. For both types of power, this is the

maximum power during the operation that enters airspace.

For simplicity and safety you can enter a higher value, the maximum power of the laser; this ignores any additional losses

in optical components in the beam path, before the beam enters airspace.

Pulse Energy and Pulse Width: If a single pulse laser (Column 1) or repetitively pulsed laser (Column 3), fill in the pulse

energy in joules and the pulse width in seconds. This is the maximum power that enters airspace. For simplicity and safety

you can enter a higher value, the maximum pulse energy of the laser; this ignores any additional losses in optical components

in the beam path, before the beam enters airspace.

Beam Diameter: Provide the beam diameter using the 1/e peak-irradiance points.

Note.— Diameter is often expressed in millimetres; however, in this form you must enter the diameter in centimetres.

Beam Divergence: The beam divergence is the full angle given at the 1/e points. If you know the diameter or divergence

measured at the 1/e2 points instead, multiply by 0.707 to convert to 1/e diameter or divergence.

Note.— Diameter and divergence measurements can be complex. You can use simplifying assumptions for safety. It is

safer to assume the beam divergence is smaller than it really is.

For example, as a beam travels from the laser through a laser show projector, the divergence generally increases. To be

conservative (safer), use the smaller divergence of the beam at the laser, before it goes through the projector. This will assume

the beam is tighter (and thus more hazardous) than it really is.

A-6 Manual on laser emitters and flight safety

Wavelength(s): Enter the wavelengths of laser light that enter airspace.

If the laser emits multiple wavelengths, each wavelength will need to be analysed separately to find their MPEs and

NOHDs. In addition, for lasers emitting visible wavelengths, each wavelength can be analysed separately to find the Visual

Effect Distances (SZED, CZED, and LFED corresponding to LSFZ, LCFZ, and LFFZ). This process is described in more

detail in the Visual Effect Distances instructions below.

In all cases of multiple-wavelength lasers, you must document your methods and calculations. If you do not analyse all

wavelengths in full, then you must explicitly state your simplifying, conservative assumptions.

MAXIMUM PERMISSIBLE EXPOSURE CALCUATIONS

MPE and MPE per pulse: Provide the Maximum Permissible Exposure (MPE) calculation results in the applicable block.

This will be used later to determine the Nominal Ocular Hazard Distance (NOHD).

The easiest way to find the MPE is to use Tables 1 to 4 as described immediately below. These tables provide a simple,

conservative method. If you require less conservative levels, use the American National Standards Institute (ANSI) Z136

series of standards or other established methods. Both the methods and calculations must be documented.

• Single Pulse (Column 1): Use Table 1 to find the MPE. Fill in the “MPE per pulse” block in the Single Pulse column.

• Continuous Wave (Column 2): Use Table 2 to find the MPE. Fill in the “MPE” block in the Continuous Wave

column.

• Repetitively Pulsed (Column 3): Lasers that produce recurring pulses of energy can produce an additional hazard

above that of a single pulse or continuous wave laser. The MPE is adjusted for repetitively pulsed lasers based on its

pulse repetition frequency. The adjusted MPE is designated as MPEPRF. The MPEPRF can be determined using either

the per-pulse energy or the average power. This document provides a simplified method for calculating the MPEPRF

for average power with wavelengths in the visible and infrared region. (ANSI Z136 series can provide a less

conservative value in some cases.) Although designated MPEPRF, the values should be placed in either the “MPE” or

“MPE per pulse” blocks of the repetitively pulsed column. Following are the simplified methods for determining the

MPEPRF for:

1. Ultraviolet wavelengths: Reference the American National Standards Institute ANSI Z136 series.

2. Visible wavelengths: Use Table 3 to determine the MPEPRF. Table 3 results have already applied the correction

factor to the CW MPE. Fill in the “MPE” block in the Repetitively Pulsed column.

3. Infrared wavelengths:

a) Use Table 2 to find the CW MPE.

b) Use Table 4 to find the infrared pulse repetition correction factor.

c) Multiply the CW MPE times the infrared pulse repetition correction factor to give the MPEPRF. Fill in the

“MPE” block in the Repetitively Pulsed column.

Note for Repetitively Pulsed lasers: The simplified methods of Tables 2 to 4 use the Average Power to determine the

MPE in W/cm2. It is possible with other methods to use the Pulse Energy to determine the MPE per pulse in J/cm2. Only

one of the two MPEs is required.

VISUAL EFFECT CALCUATIONS (for visible lasers only)

If the laser has no wavelengths in the visible range (400–700 nm), enter “N/A — non-visible laser” in these blocks and go

to the next section (Beam Directions).

Appendix A A-7

For visible lasers, the Authority is concerned about beams that are eye-safe (below the MPE) but are bright enough to

distract aircrews. In accordance with ICAO Recommendations (see Annex 14, Volume I — Aerodrome Design and

Operations, 5.3.1.2), the Authority has therefore established Laser-beam Sensitive, Laser-beam Critical and Laser-beam Free

Flight Zones where aircraft should not be exposed to light above 100 µW/cm2, 5 µW/cm2, and 50 nW/cm2, respectively.

Because apparent brightness varies with wavelength — green is more visible than red or blue — a visual correction factor

can be applied if desired. This has the effect of allowing more power for red and blue beams than for green beams. For any

visible laser, you must submit Visual Effect Calculations.

Pre-Corrected Power: The PCP is the power before applying any visual correction factor. The method used to determine

the PCP depends on which type of laser you are using:

• Single Pulse (Column 1): Multiply the Pulse Energy (J) by 4, and enter in the form. Note.— This technique averages

the pulse’s energy over the 0.25 sec maximum pulse duration and is a conservative approximation of the visual effect

of a pulse. If you use less conservative calculations, you must document your methods and calculations.

• Continuous Wave (Column 2): The Pre-Corrected Power is the same as the maximum power of the laser. Enter the

same value you previously filled out in the Power (W) block of the form.

• Repetitively Pulsed (Column 3):

A) If you filled out the Power (W) block on the form, enter that value.

B) If you filled out the Pulse Energy (J) block on the form, multiply that value times the Pulse Repetition Frequency

(Hz) to determine the average power.

Visual Correction Factor and Visually Corrected Power: The VCF takes into account the beam’s apparent brightness,

which varies depending on wavelength. Once you find the VCF, you can then determine the VCP. You have a choice of

methods, depending on how precise you want to be:

1) For the simplest, most conservative analysis of a single- or multiple-wavelength beam: Assume there is no

correction factor at all — the laser is at maximum apparent brightness (VCF of 1.0). In the Visual Correction Factor

block of the form, enter “1.0 (assumed)” for the Visual Correction Factor. In the Visually Corrected Power block,

enter the same value you filled out for the Pre-Corrected Power.

2) For a single-wavelength beam: To find the Visual Correction Factor, use Table 5. To find the Visually Corrected

Power, multiply the Visual Correction Factor by the Pre-Corrected Power. (An example calculation is provided at

Table 5, example 1.)

3) For a beam with multiple wavelengths, choose one method:

A) Make a simplifying, conservative assumption. Use Table 5 to determine which wavelength has the largest Visual

Correction Factor (is the most visible). Enter this in the Visual Correction Factor block of the form. To find the

Visually Corrected Power, multiply this Visual Correction Factor by the Pre-Corrected Power of the laser (all

wavelengths). Note.— You must attach data and calculations showing how you arrived at the Visually Corrected

Power.

B) Analyse each wavelength separately, then sum them. First, determine the Pre-Corrected Power for each

wavelength. Next, use Table 5 to find the Visual Correction Factor for each wavelength. Multiply each

wavelength’s Pre-Corrected Power by its Visual Correction Factor, to find the Visually Corrected Power (VCP)

for that wavelength. Add all the VCPs together to determine the total VCP. Enter the total VCP in the “Visually

Corrected Power” block of the form. (An example calculation is provided in Table 5, example 2.) Note.— You

must attach data and calculations showing how you arrived at the Visually Corrected Power.

A-8 Manual on laser emitters and flight safety

3. BEAM DIRECTIONS

Provide the pointing directions of the beam projections for this configuration.

Azimuth: If the beam is moved horizontally during the operation, enter the movement range under “Azimuth”; for example,

“20 to 50 degrees”. Make sure you give the range going clockwise; otherwise your data will be interpreted as directing the

beam everywhere but where you intend. Specify if azimuth is in true or magnetic readings.

Magnetic Variation: Provide the magnetic variation for the location if this is known (this must be done if you mark the

“Magnetic” check box or if you are using a compass as part of your control measures).

For some configurations, additional information about the beam direction may be needed. For example: lasers that are very

widely separated at the Geographic Location listed on page 1, or a laser used on an aircraft or spacecraft which is moving

and/or shoots downwards. If this additional information is useful for the Authority to evaluate the proposal, then attach the

information to this form.

4. DISTANCES CALCULATED FROM ABOVE DATA

There are four distances that are important in evaluating the safety of outdoor operations. Here are brief definitions:

• Nominal Ocular Hazard Distance (NOHD): The beam is an eye hazard (is above the MPE), from the laser source

to this distance.

• Sensitive Zone Exposure Distance (SZED): The beam is bright enough to cause temporary vision impairment, from

the source to this distance. Beyond this distance, the beam is 100 µW/cm2 or less.

• Critical Zone Exposure Distance (CZED): The beam is bright enough to cause a distraction interfering with critical

task performance, from the source to this distance. Beyond this distance, the beam is 5 µW/cm2 or less.

• Laser-Free Exposure Distance (LFED): Beyond this distance, the beam is 50 nW/cm2 or less — dim enough that

it is not expected to cause a distraction.

For each of these four distances, it is important to know the distance directly along the beam (the Slant Range) as well as

the ground covered (the Horizontal Distance) and the altitude (the Vertical Distance). The diagram shows these three

distances.

Horizontal distance

Vertical

distance

Slant

range

Appendix A A-9

NOMINAL OCULAR HAZARD DISTANCE

NOHD Slant Range: Use Equation 6.1 for Single Pulse, or for Repetitively Pulsed if you calculated the Pulse Energy and

MPEPRF. Use Equation 6.2 for Continuous Wave, or for Repetitively Pulsed if you calculated the Average Power and MPE.

Equation 6.1

Where:

SRNOHD = NOHD Slant Range in feet

Q = Pulse Energy (J)

ϕ = Beam Divergence (mrad)

MPEH = MPE per pulse in J/cm2

1366 = Conversion factor used to convert centimetres into feet and radians into milliradians

Equation 6.2

Where:

SRNOHD = NOHD Slant Range in feet

ϕ = Beam Divergence (mrad)

Φ = Power (W)

MPEE = MPE in W/cm2

1366 = Conversion factor used to convert centimetres into feet and radians into milliradians

Example: A 40-watt CW laser has a beam divergence of 1.5 milliradians

Given:

ϕ = 1.5 mrad

Φ = 40 W

MPEE = 0.00254 (2.54 mW/cm2, from Table 2)

Solve Equation 6.2:

= 3092 ft

NOHD Horizontal Distance is the distance along the ground. Note that the horizontal distance uses the minimum elevation

angle. Calculate the horizontal distance using the equation:

HD = SRNOHD ×cos(Minimum Elevation Angle)

Where:

HD = Horizontal distance along the ground. The units are the same as for the Slant Range. If SR is in feet, then HD will

also be in feet.

SRNOHD = NOHD Slant Range

Minimum Elevation Angle = Data from “Minimum elevation angle” block on form.

Example: The NOHD Slant Range is 1000 feet, and the beam is elevated at 30 degrees above horizontal. The Horizontal

Distance along the ground is 1000 ×cos(30), or 866 feet.

SRNOHD

1366 Q×

ϕ2MPEH

----------------------------=

SRNOHD

1366 Φ×

ϕ2MPEE

----------------------------=

SRNOHD

1366 40×

1.520.00254×

----------------------------------- 54640

0.005715

---------------------- 9560804===

A-10 Manual on laser emitters and flight safety

NOHD Vertical Distance is the distance above the ground. Note that the vertical distance uses the maximum elevation angle.

Calculate the vertical distance using the equation:

VD = SRNOHD ×sin(Maximum Elevation Angle)

Where:

VD = Vertical distance (altitude). The units are the same as for the Slant Range. If SR is in feet, then VD will also be in

feet.

SRNOHD = NOHD Slant Range

Maximum Elevation Angle = Maximum elevation angle of laser beam as provided on form.

Example: The NOHD Slant Range is 1000 feet, and the beam is elevated at 30 degrees above horizontal. The Vertical

Distance (altitude) is 1000 ×sin(30) or 500 feet.

VISUAL EFFECT DISTANCES

Fill in this section only if one or more of the laser wavelengths are visible (in the range 400–700 nm).

• If the laser is outside the visible range, enter “N/A — non-visible laser” in all SZED, CZED, and LFED blocks.

• If the laser is visible, then perform the SZED, CZED, and LFED calculations below.

Important: For some visible pulsed lasers, the SZED, CZED, and LFED may be calculated to be less (shorter distance) than

the NOHD. If this is the case, for safety reasons do not enter the distance numbers in the applicable block. Instead, you must

enter that the distance is “Less than NOHD”. This is because in this case, the NOHD (eye-damage distance) would be the

most important for calculating safety distances and airspace to be protected.

SZED Slant Range: Use the following equation:

Equation 6.3

Where:

SRSZED = SZED Slant Range

ϕ = Beam Divergence (mrad)

ΦVCP = Visually Corrected Power (from form)

3700 = Conversion factor used to convert centimetres into feet and radians into milliradians

SZED Horizontal Distance: Use the following equation. For details, see the NOHD Horizontal Distance instructions above.

HD = SRSZED ×cos(Minimum Elevation Angle)

SZED Vertical Distance: Use the following equation. For details see the NOHD Vertical Distance instructions above.

VD = SRSZED ×sin(Maximum Elevation Angle)

SRSZED

3700

------------ΦVCP

×=

Appendix A A-11

CZED Slant Range, Horizontal Distance and Vertical Distance: Multiply the SZED values above by 4.5. Example: If

SZED Slant Range was 5 000 feet, HD was 866 feet, and VD was 500 feet, then the CZED SR is 22 500 feet, HD is 3 897

feet and VD is 2 250 feet.

LFED Slant Range, Horizontal Distance and Vertical Distance: Multiply the SZED values above by 45.

5. CALCULATION METHOD

List the method by which the calculations were performed.

Source note for equations: The equations above are derived from ANSI Z136.1 and have been re-expressed to a simpler

form as follows: Beam divergence (ϕ) is entered in milliradians, making the first ANSI fraction 1000/ϕ instead of 1/ϕ. The

radical (square root) sign is used instead of raising to a power of 0.5. Under the radical, the expression 4/π is reduced to

1.27, while beam diameter (a2) is not used since its contribution to the overall slant range distance is negligible. ANSI results

are in cm; to convert to feet, a conversion factor of 0.0328 is used (1 cm = 0.0328 ft). There are now two numeric constants,

1 000 (from the milliradians fraction) and 0.0328, which are multiplied into a single constant, 32.8, to give results in feet.

For results in cm, use “1 000” as the constant; for results in metres, use “10”.

Note.— The assumption that a constant can be used to derive the CZED and LFED from the previously-calculated SZED

is valid only if atmospheric attenuation is ignored. Should you be relying on atmospheric attentuation for a safety factor, you

must use a more detailed analysis which independently calculates these three Visual Effect Distances.

A-12 Manual on laser emitters and flight safety

Table 1. Single Pulse Selected Maximum Permissible Exposure (MPE) Limits

To find CA:

For wavelength = 700 to 1050 nm, CA = 100.002 (wavelength – 700)

Example 1: Laser wavelength is 850 nm; CA = 100.002(850 – 700) = 100.002*150 = 100.3 = 1.995

Example 2: Laser wavelength is 933 nm; CA = 100.002(933 – 700) = 100.002*233 = 100.466 = 2.924

To find CC:

For wavelength = 1050 to 1150 nm, CC = 1.0

For wavelength = 1150 to 1200 nm, CC = 100.018 (wavelength – 1150)

For wavelength = 1200 to 1400 nm, CC = 8.0

Example 3: Laser wavelength is 1175 nm; CC = 100.018(1175 – 1150) = 100.018*25 = 100.45 = 2.8

To find t: “t” is the pulse duration in seconds.

Wavelength

(nm)

Exposure Duration

(sec)

MPE

(J/cm2)

Ultraviolet

180 to 400 10–9 to 10 Reference American National Institute

Standard (ANSI)

Z136 series

Visible

400 to 700 <10–9

10–9 to 18 ×10–6

18 ×10–6 to 10

0.25

Reference ANSI Z136 series

0.5 ×10–6

1.8 ×t0.75 × 10–3

0.64 ×10–3

Infrared

700 to 1 050 <10–9

10–9 to 18 ×10–6

18 ×10–6 to 10

0.25

Reference ANSI Z136 series

0.5 ×CA×10–6

1.8 ×CA×t0.75 ×10–3

0.64 ×CA×10–3

10 ×CA×10–3

1 050 to 1 400 <10–9

10–9 to 50 ×10–6

50 ×10–6 to 10

Reference ANSI Z136 series

5.0 ×CC×10–6

9×CC×t0.75 ×10–3

50 ×CC×10–3

1 400 to 1 500 <10–9

10–9 to 10–3

10–3 to 10

Reference ANSI Z136 series

0.1

0.56 ×t0.25

1.0

1 500 to 1 800 <10–9

10–9 to 10

Reference ANSI Z136 series

1.0

1 800 to 2 600 <10–9

10–9 to 10–3

10–3 to 10

Reference ANSI Z136 series

0.1

0.56 ×t0.25

1.0

2 600 to 10 000 <10–9

10–9 to 10–7

10–7 to 10

Reference ANSI Z136 series

10 ×10–3

0.56 ×t0.25

1.0

Appendix A A-13

Table 2. CW Mode Maximum Permissible Exposure (MPE) Limits

Values are for selected wavelengths for unintentional viewing.

Example 1: Laser wavelength is visible; MPE = 0.00254 W/cm2

Example 2: Laser wavelength is 850 nm; MPE = (100.002(850 – 700))(1.01 × 10–3) = (100.002*150)(0.00101) = (100.3) × 0.00101

= 1.995 × 0.00101 = 0.002 W/cm2

Example 3: Laser wavelength is 1175 nm; MPE = (100.018(1175 – 1150))(5 × 10–3) = (100.018*25)(0.005) = (100.45) × 0.005

= 2.818 × 0.005 = 0.01409 W/cm2

“Unintentional viewing”: Exposure durations used for unintentional viewing of a CW exposure are 0.25 seconds or shorter

for visible lasers, and 10 seconds or shorter for infrared lasers. (For visible light, it is assumed that within 0.25 seconds, the

person will blink or will move to avoid the light. For infrared, it is assumed that the laser will not stay in the same spot for

more than 10 seconds, due to normal body movement.)

Source: ANSI Z136.1 Table 5 for CW Exposure.

Wavelength

(nm)

MPE

(W/cm2)

Ultraviolet

180 to 400 Reference American National Standards Institute ANSI

Z136 series

Visible

400 to 700 2.54 ×10–3

Infrared

700 to 1 050 (100.002(wavelength – 700))(1.01 ×10–3)

1 050 to 1 150 5×10–3

1 150 to 1 200 (100.018(wavelength – 1150))(5 ×10–3)

1 200 to 1 400 4.0 ×10–2

1 400 to 10 000 0.1

A-14 Manual on laser emitters and flight safety

Table 3. Maximum Permissible Exposure — Pulse Repetition Frequency (MPEPRF) Limits for Visible Lasers

For unintentional viewing of repetitively pulsed visible (400–700 nm) laser light with pulse width between 1 ns and 18 µs.

If the laser’s pulse repetition frequency falls between two table entries, use the more conservative (smaller) value of the two

resulting MPEPRF values.

Note.— This table for MPEPRF is based on repetitively pulsed lasers with a pulse width between 1 ns and 18 µs. These

MPEPRF numbers can be used to estimate larger pulse widths, and will provide a conservative (safer) result.

Not intended for scanning analysis: This table is intended for lasers that naturally emit repetitive pulses, such as Q-switched

lasers. It is not intended for analysing “scanned” pulses, caused by moving the beam quickly over a viewer or aircraft.

(Examples: graphics or beam patterns used in laser displays, or scanned patterns used for atmospheric analysis.) Pulses

resulting from scanning are often extremely variable in pulse width and duration, and thus require a more stringent analysis.

Pulse

Repetition

Frequency

(Hz)

MPEPRF

(W/cm2)

Pulse

Repetition

Frequency

(Hz)

MPEPRF

(W/cm2)

Pulse

Repetition

Frequency

(Hz)

MPEPRF

(W/cm2)

17.07 ×10–07 30 9.06 ×10–06 5 000 4.20 ×10–04

21.19 ×10–06 40 1.12 ×10–05 10 000 7.07 ×10–04

31.61 ×10–06 50 1.33 ×10–05 15 000 9.58 ×10–04

42.00 ×10–06 75 1.80 ×10–05 20 000 1.19 ×10–03

52.36 ×10–06 100 2.24 ×10–05 25 000 1.41 ×10–03

62.71 ×10–06 150 3.03 ×10–05 30 000 1.61 ×10–03

73.04 ×10–06 200 3.76 ×10–05 40 000 2.00 ×10–03

83.36 ×10–06 250 4.45 ×10–05 50 000 2.36 ×10–03

93.67 ×10–06 500 7.48 ×10–05 55 000 2.54 ×10–03

10 3.98 ×10–06 1 000 1.26 ×10–04 100 000 2.54 ×10–03

15 5.39 ×10–06 1 500 1.70 ×10–04

20 6.69 ×10–06 2 000 2.11 ×10–04

25 7.91 ×10–06 2 500 2.50 ×10–04

Appendix A A-15

Table 4. Correction Factors (MPEpulsed / MPEcw) for Repetitively Pulsed Infrared Lasers

Use to find MPEPRF of repetitively pulsed infrared (700–1 400 nm) laser light with pulse width between 1 ns and 18 µs.

*The MPE for lasers which operate at a PRF greater (faster) than 55 000 Hz for wavelengths 700–1 050 nm (or 22 000 Hz

for wavelengths 1 050–1 400 nm) is the same as for continuous wave lasers, so the correction factor is 1.

To find the MPE for repetitively pulsed infrared lasers, multiply the CW Mode MPE by a correction factor from this table.

If the laser’s pulse repetition frequency falls between two table entries, use the more conservative (smaller) value of the two

resulting correction factors.

Example: A laser operating at a pulse repetition frequency (PRF) of 12 000 Hz emits infrared light at 850 nm. First, go to

Table 2 and find the CW Mode MPE for the 850 nm wavelength, which is 0.002 W/cm2 (see example 2 from Table 2). Next,

from the table above determine which of the right two columns should be used; in this case, the column labelled “For

wavelength 700–1 050 nm”. The laser’s PRF of 12 000 Hz falls between the 10 000 and 15 000 rows, so use the more

conservative (smaller) value of the 10 000 Hz PRF: 2.8 × 10–1. The correction factor is thus 0.28. Multiply this by the CW

Mode MPE found from Table 2 to get a MPEPRF of 0.28 × 0.002 W/cm2 = 0.00056 W/cm2 = 5.6 × 10–4 W/cm2.

Pulse Repetition

Frequency

(Hz)

Correction

Factor

For wavelengths

700–1 050 nm

Correction

Factor

For wavelengths

1 050–1 400 nm

12.8×10–4 5.5 ×10–4

59.4×10–4 1.8 ×10–3

10 1.6 ×10–3 3.1 ×10–3

15 2.1 ×10–3 4.2 ×10–3

20 2.6 ×10–3 5.2 ×10–3

25 3.1 ×10–3 6.2 ×10–3

50 5.3 ×10–3 1.0 ×10–2

75 7.1 ×10–3 1.4 ×10–2

100 9.0 ×10–3 1.7 ×10–2

150 1.2 ×10–2 2.4 ×10–2

200 1.5 ×10–2 2.9 ×10–2

250 1.8 ×10–2 3.5 ×10–2

500 3.0 ×10–2 5.9 ×10–2

1 000 5.0 ×10–2 1.0 ×10–1

2 000 8.0 ×10–2 1.7 ×10–1

3 000 1.1 ×10–1 2.3 ×10–1

4 000 1.4 ×10–1 2.8 ×10–1

5 000 1.7 ×10–1 3.3 ×10–1

10 000 2.8 ×10–1 5.6 ×10–1

15 000 3.8 ×10–1 7.5 ×10–1

20 000 4.7 ×10–1 9.3 ×10–1

21 000 4.8 ×10–1 9.7 ×10–1

22 000 5.0 ×10–1 1.00*

23 000 5.2 ×10–1 1.00

24 000 5.4 ×10–1 1.00

25 000 5.5 ×10–1 1.00

30 000 6.3 ×10–1 1.00

40 000 7.9 ×10–1 1.00

50 000 9.3 ×10–1 1.00

55 000 1.00* 1.00

A-16 Manual on laser emitters and flight safety

Table 5. Visual Correction Factor for Visible Lasers

Use for visible lasers only (400–700 nm).

To find the Visually Corrected Power (VCP) for a specified wavelength, multiply the Visual Correction Factor (VCF) for the

wavelength (from the table above) by the Average Power. If the laser’s wavelength falls between two table entries, use the

more conservative (larger) value of the two resulting VCFs.

Example 1: A frequency-doubled YAG laser emits 10 watts of 532 nm continuous wave light. From the table, 532 is between

530 and 540; use the more conservative (larger) Visual Correction Factor of 540 nm: 9.524 × 10–1. Multiply the VCF of

0.9524 by the Average Power of 10 watts to obtain the Visually Corrected Power of 9.524 watts.

Example 2: An 18-watt argon laser emits 10 watts of 514 nm light, and 8 watts of 488 nm light, both continuous wave.

Calculate each wavelength separately, then add the resulting Visually Corrected Powers together.

10 watts at 514 nm: From the table, 514 is between 510 and 520; use the more conservative (larger) VCF of 520 nm:

7.092 × 10–1. Multiply the VCF of 0.7092 by the Average Power of 10 watts to obtain the Visually Corrected Power of

7.092 watts.

Laser

Wavelength

(nm)

Visual Correction

Factor

(VCF)

400

410

420

430

440

450

460

470

480

490

500

510

520

530

540

550

555

560

570

580

590

600

610

620

630

640

650

660

670

680

690

700

4.0 ×10–4

1.2 ×10–3

4.0 ×10–3

1.16 ×10–2

2.30 ×10–2

3.80 ×10–2

5.99 ×10–2

9.09 ×10–2

1.391 ×10–1

2.079 ×10–1

3.226 ×10–1

5.025 ×10–1

7.092 ×10–1

8.621 ×10–1

9.524 ×10–1

9.901 ×10–1

1.0 ×100–

9.901 ×10–1

9.524 ×10–1

8.696 ×10–1

7.576 ×10–1

6.329 ×10–1

5.025 ×10–1

3.817 ×10–1

2.653 ×10–1

1.751 ×10–1

1.070 ×10–1

6.10 ×10–2

3.21 ×10–2

1.70 ×10–2

8.2 ×10–3

4.1 ×10–3

(VCF = 1)

Appendix A A-17

8 watts at 488 nm: From the table, 488 is between 480 and 490; use the more conservative (larger) VCF of 490 nm:

2.079 × 10–1. Multiply the VCF of 0.2079 by the Average Power of 8 watts to obtain the Visually Corrected Power of

1.6632 watts.

Finally, add the two VCPs together: 7.092 + 1.6632 = 8.7552. The 18-watt laser in this example has a Visually Corrected

Power of only 8.7552 watts. Note that the 10-watt YAG in Example 1 appears brighter to the eye (9.5 WVCP) than an 18-watt

argon (8.8 WVCP).

Source: The Visual Correction Factor used in this table (CF) is the CIE normalized efficiency photopic visual function curve

for a standard observer. The luminance (lm •cm–2) is the measured irradiance multiplied by CF and 683. The effective irradiance

is the actual (measured) irradiance multiplied by CF. The effective irradiance (W •cm–2) multiplied by 683 lm •W–1 is the

illuminance (lm •cm–2). The term “Visually Corrected Power” divided by the area of the laser beam is the “effective irradiance”,

as used in this document.



B-1

Appendix B

SUSPECTED LASER BEAM INCIDENT REPORT AND

SUSPECTED LASER BEAM EXPOSURE QUESTIONNAIRE

SUSPECTED LASER BEAM INCIDENT REPORT

This form may be used by local ATC or airline authorities to report a suspected laser beam exposure. When completed, the

report should be forwarded to the competent authority as soon as possible for further investigation.

Name _____________________________________________________________ Age _______________________________

Position (pilot, co-pilot, controller, etc.) _________________________________ Phone _____________________________

Type of vision correction worn at time of incident (spectacles/contact lenses) _____________________________________

Type of aircraft _______________________________________________________________________________________

Aircraft ID or call _____________________________________________________________________________________

Date and time of incident (UTC) _________________________________________________________________________

Date and time report is being completed (UTC) _____________________________________________________________

Environmental factors:

Weather conditions __________________________________________________________________________________

VMC/IMC _________________________________________________________________________________________

Ambient light level (day, night, sunlight, dawn, dusk, starlight, moonlight, etc.) ________________________________

__________________________________________________________________________________________________

Location of incident:

Near (aerodrome/city/NAVAID) ________________________________________________________________________

Radial and distance _________________________________________________________________________________

Phase of flight _____________________________________________________________________________________

Type/name of approach or departure procedure ___________________________________________________________

Heading/approximate heading if in turn _________________________________________________________________

Altitude (AGL) ____________________________ (MSL) __________________________________________________

Aircraft bank and pitch angles _________________________________________________________________________

Angle of incidence:

Did the light hit your eye(s) directly or from the side? _____________________________________________________

__________________________________________________________________________________________________

B-2 Manual on laser emitters and flight safety

Light description:

Colour ____________________________________________________________________________________________

Nature of beam (constant/flicker/pulsed) ________________________________________________________________

Light source (stationary or moving) ____________________________________________________________________

Do you feel you were intentionally tracked? _____________________________________________________________

Relative intensity (flashbulb, headlight, sunlight) __________________________________________________________

Duration of exposure (seconds) ________________________________________________________________________

Was the beam visible prior to the incident? ______________________________________________________________

Position of light source (relative to geographical feature or aircraft) __________________________________________

__________________________________________________________________________________________________

Circle the window where the light entered the cockpit:

Left left-front centre right-front right other __________________

Elevation of the beam from horizontal (degrees) __________________________________________________________

Effect on individual:

Describe visual*/psychological/physical effects ___________________________________________________________

__________________________________________________________________________________________________

Duration of visual effects (seconds/minutes/hours/days) ____________________________________________________

Do you intend to seek medical attention? ________________________________________________________________

__________________________________________________________________________________________________

Note.— This is recommended if even minor symptoms were experienced.

Effect on operational or cockpit procedures: ________________________________________________________________

_____________________________________________________________________________________________________

* Examples of common visual effects:

After-image. An image that remains in the visual field after an exposure to a bright light.

Blind spot. A temporary or permanent loss of vision of part of the visual field.

Flash-blindness. The inability to see (either temporarily or permanently) caused by bright light entering the eye and

persisting after the illumination has ceased.

Glare. A temporary disruption in vision caused by the presence of a bright light (such as an oncoming car’s headlights)

within an individual’s field of vision. Glare lasts only as long as the bright light is actually present within the individual’s

field of vision.

— — — — — — — —

Appendix B B-3

SUSPECTED LASER BEAM EXPOSURE QUESTIONNAIRE

This questionnaire may be filled out by the competent authority during interviews with persons exposed to laser beams. This

information will be used to aid in any subsequent investigation and provide important medical and statistical data for the

review of regulatory and enforcement issues associated with new laser beam applications and threats to aviation safety. The

completed form should be forwarded to the appropriate aviation authority as soon as possible.

1. Did anyone else see the light beam? ___________________________________________________________________

2. What was the colour(s) of the light? __________________________________________________________________

Did the colour(s) change during the exposure? ___________________________________________________________

3. Did the light come on suddenly, and did it become brighter as you approached it?______________________________

_________________________________________________________________________________________________

4. Was the light continuous or did it seem to flicker? _______________________________________________________

If it flickered, how rapidly and regularly? _______________________________________________________________

5. Did the light fill your cockpit or compartment? __________________________________________________________

6. How would you describe the brightness of the light? _____________________________________________________

Was it equally bright in all areas or was it brighter in one area?_____________________________________________

7. Did you attempt an evasive manoeuvre? _______________________________________________________________

If so, did the beam follow you as you tried to move away? ________________________________________________

How successful were you in avoiding it? _______________________________________________________________

8. Do you know the source of the light emission? __________________________________________________________

9. Can you estimate how far away the light source was from your location? _____________________________________

Was the source moving? _____________________________________________________________________________

10. What was between the light source and your eyes — windscreen, glasses, contact lenses, etc.? ___________________

Did any of these sustain damage by the light? ___________________________________________________________

11. Was the light coming directly from its source or did it appear to be reflected off other surfaces? __________________

Were there multiple sources of light? __________________________________________________________________

12. Did you look straight into the light beam or off to the side? ________________________________________________

13. How long was the exposure? _________________________________________________________________________

Did the light seem to track your path or was there incidental contact? ________________________________________

14. At what time of the day did the incident occur? _________________________________________________________

15. What was the visibility? ____________________________________________________________________________

What were the atmospheric conditions — clear, overcast, rainy, foggy, hazy, sunny? ____________________________

B-4 Manual on laser emitters and flight safety

16. What tasks were you performing when the exposure occurred? _____________________________________________

Did the light prevent or hamper you from doing those tasks, or was the light more of an annoyance? ______________

17. What were the visual effects you experienced (after-image, blind spot, flash-blindness, glare*)? __________________

18. How long did any symptoms you experienced from the exposure last? _______________________________________

Are any symptoms (tearing, light sensitivity, headaches, etc.) still present? ____________________________________

19. Did you touch or rub your eyes at the time of the incident? _______________________________________________

20. Did you have your eyes examined after the incident? _____________________________________________________

If so, when and by whom? __________________________________________________________________________

What were the results of this visit? ____________________________________________________________________

21. Did you report the incident? _________________________________________________________________________

If so, to whom (ATC, medical personnel, safety officer, etc.) and when? ______________________________________

* Examples of common visual effects:

After-image. An image that remains in the visual field after an exposure to a bright light.

Blind spot. A temporary or permanent loss of vision of part of the visual field.

Flash-blindness. The inability to see (either temporarily or permanently) caused by bright light entering the eye and

persisting after the illumination has ceased.

Glare. A temporary disruption in vision caused by the presence of a bright light (such as an oncoming car’s headlights)

within an individual’s field of vision. Glare lasts only as long as the bright light is actually present within the individual’s

field of vision.

C-1

Appendix C

AMSLER GRID TESTING PROCEDURE

The Amsler grid test is designed to detect defects in the central visual field of an eye, corresponding to retinal lesions as

small as 50 micrometres.

The chart below is sized to be viewed at a distance of 28–30 cm, the usual distance for reading tests. At this distance the

test will examine the central 20 degrees of the patient’s field of vision for abnormalities, with each small square equivalent

to 1 degree. Before using this chart:

a) the refraction of the eye in question must be exactly corrected for this distance;

b) the chart must be clearly and evenly illuminated as for a reading test;

c) all artificial mydriasis and any ophthalmoscopy immediately before the examination must be avoided; and

d) the other eye should be covered, preferably with an occluder.

C-2 Manual on laser emitters and flight safety

While continually urging the patient to look steadily upon the central point, ask the following questions. Record the responses

and ask the patient to carefully draw any abnormal results on the grid chart.

1. Do you see the spot in the centre of the square chart?

2. Keeping your gaze fixed upon the spot in the centre, can you see the four corners of the big square? Can you also

see the four sides of the square? In other words, can you see the whole square?

3. Keeping your gaze fixed upon the spot in the centre, do you see the network intact within the whole square? Are there

any interruptions in the network of squares, such as holes or spots? Is it blurred in any place? If so, where?

4. Keeping your gaze fixed upon the spot in the centre, are both the horizontal and vertical lines straight and parallel?

In other words, is every small square equal in size and perfectly regular?

5. Keeping your gaze fixed upon the spot in the centre, do you see any movement of certain lines? Is there any vibration

or wavering, shining or colour tint? If so, where?

6. Keeping your gaze fixed upon the spot in the centre, at what distance from this point do you see the blur or distortion?

How many small intact squares do you find between the blur or distortion and the centre point where your gaze is

fixed?

— END —



09/03, E/P1/2000

Order No. 9815

Printed in ICAO

9815Flyleaf ICAO DOC 9815 Manual On Laser Emitters And Flight Safety (2003)

Navigation menu

Versions of this User Manual:

Views

Navigation