Pico Scale User Manual

User Manual:

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1 Introduction
2 Product safety
3 PICOSCALE fundamentals
4 Basic Concepts
5 PicoScale hardware
6 Setup and installation
7 PicoScale Control GUI
8 Concluding Remarks

PICOSCALE

USER MANUAL

www.smaract.com

tables or diagrams prohibited.

The information given in this document was carefully checked by our team and is constantly up-

dated. Nevertheless, it is not possible to fully exclude the presence of errors. In order to always

get the latest information, please contact our technical sales team.

SmarAct GmbH, Schuette-Lanz-Strasse 9, D-26135 Oldenburg

Phone: +49 (0) 441 - 800879-0, Telefax: +49 (0) 441 - 800879-21

Internet: www.smaract.com, E-Mail: info@smaract.com

Document Version: 2.1.4

PicoScale User Manual

TABLE OF CONTENTS

1 Introduction ................................................................................................................................. 6

1.1 Preface ................................................................................................................................. 6

1.2 Technical support ................................................................................................................ 6

1.3 Signal words and symbols in this manual.......................................................................... 7

1.3.1 Signal words ............................................................................................................. 7

1.3.2 Symbols .................................................................................................................... 8

2 Product safety ............................................................................................................................. 9

2.1 Optical safety ....................................................................................................................... 9

2.2 Electrical safety .................................................................................................................... 10

2.3 Safety precautions............................................................................................................... 11

2.4 Compliance .......................................................................................................................... 12

2.4.1 CDRH/EN60825-1 ..................................................................................................... 12

2.4.2 Low voltage directive ............................................................................................... 12

2.4.3 EMC directive............................................................................................................ 12

2.4.4 RoHS directive .......................................................................................................... 13

2.4.5 Declaration of Conformity ....................................................................................... 14

2.5 Intended use........................................................................................................................ 15

2.6 Unpacking ............................................................................................................................ 15

2.7 Disposal of old equipment.................................................................................................. 15

3PICOSCALE fundamentals ......................................................................................................... 16

3.1 General setup and basic components................................................................................ 16

3.2 Measurement principle....................................................................................................... 17

3.2.1 Michelson interferometer........................................................................................ 17

3.2.2 Sinusoidal phase modulation.................................................................................. 18

3.2.3 Working range.......................................................................................................... 19

3.3 Traceability........................................................................................................................... 19

3.4 Environmental compensation............................................................................................. 19

3.4.1 Dead path................................................................................................................. 20

4 Basic Concepts ........................................................................................................................... 21

4.1 Modular architecture........................................................................................................... 21

4.1.1 Advanced trigger...................................................................................................... 21

4.1.2 Stream generator..................................................................................................... 21

4.1.3 Digital and analog GPIO, AquadB............................................................................ 23

4.1.4 Clock Generator ....................................................................................................... 23

4.1.5 Signal Generator ...................................................................................................... 23

4.1.6 Calculation System................................................................................................... 23

4.1.7 Counters ................................................................................................................... 23

4.1.8 Environmental Module ............................................................................................ 24

PicoScale User Manual

TABLE OF CONTENTS

4.2 Data sources ........................................................................................................................ 24

4.3 Signal ﬂow............................................................................................................................ 25

4.4 Adjustment auto function ................................................................................................... 26

4.5 Events................................................................................................................................... 26

4.6 System ﬁlters ....................................................................................................................... 26

4.7 Streaming aggregation........................................................................................................ 27

4.8 Network discovery protocol................................................................................................ 27

5 PicoScale hardware .................................................................................................................... 29

5.1 PICOSCALE controller ........................................................................................................ 29

5.2 Interfaces ............................................................................................................................. 31

5.2.1 Environmental Module interface ............................................................................ 31

5.2.2 Optical outputs......................................................................................................... 32

5.2.3 Power connection .................................................................................................... 32

5.2.4 USB slave interface .................................................................................................. 33

5.2.5 Ethernet interface .................................................................................................... 33

5.2.6 USB master interface............................................................................................... 33

5.2.7 SmarAct Sensor Interface (SI).................................................................................. 33

5.2.8 SmarAct High Speed Sensor Interface (HSI)........................................................... 33

5.2.9 GPIO and Digital Diﬀerential Interface ................................................................... 33

5.3 Breakout-Box ....................................................................................................................... 35

5.3.1 Diﬀerential Digital Interface DDI............................................................................. 36

5.3.2 BOB digital GPIOs..................................................................................................... 38

5.3.3 BOB analog GPIOs ................................................................................................... 39

5.4 Sensor heads ....................................................................................................................... 40

5.5 Environmental Module........................................................................................................ 41

6 Setup and installation................................................................................................................. 42

6.1 System checklist .................................................................................................................. 42

6.2 Unpack the system .............................................................................................................. 43

6.3 Cabling ................................................................................................................................. 43

6.4 System power up................................................................................................................. 45

6.5 PICOSCALE software and APIinstallation......................................................................... 46

6.6 Firmware updates................................................................................................................ 46

6.6.1 Performing a PICOSCALE ﬁrmware update .......................................................... 47

6.6.2 System diagnostics data .......................................................................................... 47

7 PicoScale Control GUI ................................................................................................................ 49

7.1 Conﬁguration of the PicoScale............................................................................................ 50

7.1.1 Connecting to the controller ................................................................................... 50

7.1.2 General settings ....................................................................................................... 50

7.1.3 Status........................................................................................................................ 51

7.2 Adjustment .......................................................................................................................... 53

7.3 Advanced Trigger................................................................................................................. 55

7.3.1 Trigger Source conﬁguration ................................................................................... 56

7.3.2 Trigger conﬁguration ............................................................................................... 60

7.4 Interfaces ............................................................................................................................. 63

7.4.1 Digital IO interface conﬁguration ............................................................................ 63

7.4.2 Digital Diﬀerential Interface (DDI) conﬁguration.................................................... 64

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TABLE OF CONTENTS

7.4.3 DAC interface conﬁguration .................................................................................... 66

7.5 Modules ............................................................................................................................... 67

7.5.1 Clock Generator ....................................................................................................... 67

7.5.2 Arbitrary Signal Generator....................................................................................... 68

7.5.3 Calculation System................................................................................................... 69

7.5.4 Counter..................................................................................................................... 70

7.6 Streaming Monitor .............................................................................................................. 71

7.6.1 Conﬁgure data receiver layout ................................................................................ 71

7.6.2 Setting up a data receiver........................................................................................ 72

7.6.3 Manipulate the data................................................................................................. 73

7.6.4 Conﬁgure the data stream ...................................................................................... 73

7.6.5 PicoScale Data Reader ............................................................................................. 74

7.7 Environmental Monitor ....................................................................................................... 76

7.8 Conﬁguration Manager ....................................................................................................... 77

7.9 Property Dialog.................................................................................................................... 78

8 Concluding Remarks .................................................................................................................. 79

PicoScale User Manual

1INTRODUCTION

Congratulations on your purchase of the SmarAct PICOSCALE interferometer! You have acquired

a powerful tool for displacement measurements with picometer resolution. We are convinced

that the innovative features will make working with the PICOSCALE a pleasant and remarkable

experience.

1.1 Preface

This manual contains user information for the SmarAct PICOSCALE system, which includes a

control box, various sensor heads, a Breakout-Box and an Environmental Module.

NOTICE

Read this manual carefully before operating the PICOSCALE for the ﬁrst time.

Special attention should be given to the material in chapter 2 "Product Safety",

which describes the secure handling of the PICOSCALE system.

1.2 Technical support

Should you experience any diﬃculties with your PICOSCALE system or need any technical in-

formation, please visit our web site: www.picoscale.com. Additional support can be obtained by

contacting our technical support at PicoScaleSupport@smaract.com or by phone at +49 441 800 879

0. When communicating with our Technical Support, the Support Engineer responding to your

request will require the model and the serial number.

PicoScale User Manual

1 INTRODUCTION

1.3 Signal words and symbols in this manual

This manual may contain sections in which particular hazards are deﬁned or special attention is

drawn to particular conditions. These sections are indicated with signal words according to ANSI

Z-535.6 and safety symbols (pictorial hazard alerts) in accordance with ANSIZ-535.3 and ISO 7010.

1.3.1 Signal words

Four signal words are used in this documentation: DANGER,WARNING,CAUTION and NOTICE.

The signal words DANGER,WARNING and CAUTION designate the degree or level of hazard when

there is a risk of injury:

DANGER

Indicates a hazardous situation that, if not avoided, will result in death or serious injury.

Do not proceed beyond a DANGER notice until the indicated conditions are fully understood

and met. This signal word is to be limited to the most extreme situations.

WARNING

Indicates a hazardous situation that, if not avoided, could result in death or serious in-

jury. Do not proceed beyond a WARNING notice until the indicated conditions are fully

understood and met.

CAUTION

Indicates a hazardous situation that, if not avoided, could result in minor or moderate

injury. Do not proceed beyond a CAUTION notice until the indicated conditions are fully

understood and met.

The signal word NOTICE is used when there is a risk of property damage:

NOTICE

Indicates information considered important, but not hazard-related.

Messages relating to hazards that could result in both personal injury and property damage are

considered safety messages and not property damage messages.

PicoScale User Manual

1 INTRODUCTION

1.3.2 Symbols

The signal words DANGER,WARNING and CAUTION are always emphasized with a safety symbol

that indicated a special hazard, regardless of the hazard level:

This symbol is intended to alert the operator to the presence of important oper-

ating and maintenance instructions.

This symbol is intended to alert the operator to the danger of exposure to haz-

ardous visible and invisible laser radiation.

This symbol is intended to alert the operator to the presence of dangerous volt-

ages within the product enclosure that may be of suﬃcient magnitude to consti-

tute a risk of electrical shock.

PicoScale User Manual

2PRODUCT SAFETY

2.1 Optical safety

Because of its special properties, laser light poses safety hazards not associated with light from

conventional sources. The safe use of the lasers require that all laser users, and everyone near

the laser system, are aware of the danger involved. The safe use of the laser depends upon

the user being familiar with the instrument and the properties of coherent, intense beams of

light.

CAUTION

The PICOSCALE Controller contains an infrared diode laser with an output of

less than 0.2 mW at 1520 nm - 1580 nm (less than 0.3 mW for V1.4 and less than

0.6 mW for V1.4-HP) and red diode laser with an output power of less than 0.6

mW at 650 nm (no red laser for V1.4-HP).

Although the PicoScale is a Class Iproduct due to the low output power, it is

a good practice not to stare directly into the laser beam. Never use optical

instruments to observe the beam, this can cause serious eye damage.

Always use the PicoScale as intended by this manual!

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2 PRODUCT SAFETY

2.2 Electrical safety

The SmarAct PICOSCALE controller contains hazardous voltages. Do not disassemble the en-

closure. There are no user-serviceable components inside. All units are designed to operate as

assembled. Warranty will be voided if the enclosure is disassembled.

WARNING

High voltage inside. To avoid electrical shock before powering the unit, make

sure that the protective conductor of the 3-conductor power cord is correctly

connected to the protective earth contact of the socket outlet. Improper ground-

ing can cause electric shock resulting in severe injury or even death.

WARNING

Shock warning. Do not operate without cover installed. Do not stick any mate-

rial through the ventilation holes. Do not operate under wet/damp conditions.

WARNING

Observe all terminal ratings. To avoid damage, ﬁre or shock hazard, observe

all ratings marked on the PicoScale Controller or documented in the manual.

NOTICE

High electrostatic charges readily accumulate in the human body and equipment

and can easily discharge without detection. Although the electronics features

have impressive input protection, permanent damage may occur on devices

subjected to high-energy electrostatic discharges. Therefore, proper ESD pre-

cautions are recommended to avoid performance degradation.

The most common ESD damage occurs while handling the device during instal-

lation or use. Take the necessary measures to protect the system from ESD, e.g.

by wearing a wrist strap.

Dry air and carpet can create an even higher potential for ESD. Precautions or

shielding need to be taken for demonstrations or trade show exhibitions.

PicoScale User Manual

2 PRODUCT SAFETY

2.3 Safety precautions

NOTICE

End of life handling. The equipment contains substances that could be harm-

ful to the environment or human health. In order to avoid release of such sub-

stances into the environment, we encourage you to recycle this product in an

appropriate system that will ensure that most of the materials are reused or

recycled appropriately. Please contact your local authorities for disposal or recy-

cling information.

NOTICE

Provide proper ventilation. In order to prevent overheat events, system fail-

ure and damage the ventilation holes of the PicoScale Controller must not be

covered. Do not stack several PICOSCALE Controllers.

NOTICE

Always clean ﬁber prior connection! Prior to connecting an interferometer

head, make sure to clean both the ﬁber connector and the ﬁber receptacle with

suitable ﬁber cleaners. This is necessary to achieve the optimal signal quality

and avoid permanent damage to the ﬁber end surfaces.

For further information, please refer to the information presented in section 6.3.

NOTICE

Handle with care! The sensor heads and the optical ﬁbers are small high-

precision parts and subject to damage under rough handling. Please make sure

to treat the ﬁbers carefully and do not bend them too tightly; the minimum bend-

ing radius of 30 mm should always be respected. Be sure that the interferome-

ter heads are not torn or sheared oﬀthe ﬁbers. The PICOSCALE control system

contains sensitive optics and electronics. Make sure to use the original PicoScale

case for transport.

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2 PRODUCT SAFETY

2.4 Compliance

The PICOSCALE laser interferometer and its accessory products have been certiﬁed in coopera-

tion with an independent testing lab to be in compliance with the environmental and safety direc-

tives listed in the following chapters.

2.4.1 CDRH/EN60825-1

The PICOSCALE laser interferometer system complies with all of the requirements of EN60825-1.

It further complies with 21 CFR 1040.10 except for deviations pursuant to Laser Notice No. 50,

dated June 24, 2007.

The following table lists PICOSCALE part or model numbers, and their corresponding CDRH ac-

cession numbers.

Table 2.1: PICOSCALE CDRH Accession Numbers

Part/Model number Accession Number Part/Model number Accession Number

PS-CTRL-V1.1-TAB (*) 1711061-000 PS-CTRL-V1.3-RACK (*) 1711061-000

PS-CTRL-V1.2-TAB (*) 1711061-000 PS-CTRL-V1.4-RACK 1711252-000

PS-CTRL-V1.3-TAB (*) 1711061-000 PS-CTRL-V1.4-TAB-HP 1810594-000

PS-CTRL-V1.4-TAB 1711252-000 PS-CTRL-V1.4-RACK-HP 1810594-000

(*) Discontinued

2.4.2 Low voltage directive

The PICOSCALE laser interferometer complies with the basic requirements of the Low Voltage

Directive 2014/35/EU.

Compliance with this directive has been veriﬁed by application of the following harmonized stan-

dards:

•EN 61010-1:2010:

Safety Requirements - Part 1: General requirements

•EN 60825-1:2014:

Safety of laser products - Part 1: Equipment classiﬁcation and requirements (compare 2.4.1)

2.4.3 EMC directive

The PICOSCALE laser interferometer complies with the basic requirements of the EMC Directive

2014/30/EU.

Compliance with this directive has been veriﬁed by application of the following harmonized stan-

dards:

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2 PRODUCT SAFETY

•EN 61326-1:2013:

EMC requirements - Part 1: General requirements

•EN 55011:2011:

Radio-frequency disturbance characteristics - Limits and methods of measurement

According to EN 61326-1:2013 the following test speciﬁcations have been used:

•EN 61000-4-2:2009 - Electrostatic discharge immunity test

•EN 61000-4-3:2010 -Radiated, radio-frequency, electromagnetic ﬁeld immunity test

•EN 61000-4-4:2010 - Electrical fast transient/burst immunity test

•EN 61000-4-5:2006 - Surge immunity test

•EN 61000-4-11:2004 - Voltage dips, short interruptions and voltage variations immunity tests

2.4.4 RoHS directive

The PICOSCALE laser interferometer complies with the basic requirements of the RoHS Directive

2011/65/EU.

Compliance with this directive has been veriﬁed by application of the following harmonized stan-

dards:

•EN 50581:2012:

Technical documentation with respect to the restriction of hazardous substances

PicoScale User Manual

2 PRODUCT SAFETY

2.4.5 Declaration of Conformity

Declaration of

Conformity

according to DIN EN ISO/IEC 17050-1:2010

Manufacturer: SmarAct GmbH

Manufacturer’s Address: Schütte-Lanz-Strasse 9

26135 Oldenburg, Germany

The manufacturer hereby declares that the product and its related accessory

Product Name: PicoScale

Model Numbers: PS-CTRL-V1.1-TAB, PS-CTRL-V1.2-TAB, PS-CTRL-V1.3-TAB,

PS-CTRL-V1.4-TAB, PS-CTRL-V1.3-RACK, PS-CTRL-V1.4-RACK

Product Options: all

complies with the following European directives:

2014/35/EU: Low Voltage Directive

2014/30/EU: EMC Directive

2011/65/EU: RoHS Directive

The applied standards certifying the conformity are listed below:

Electromagnetic Emission: DIN EN 61326-1:2013

DIN EN 55011:2011, Groupe 1, Class B 1

Electromagnetic Immunity: DIN EN 61000-4-2:2009/DIN EN 61326-1:2013 (DIN EN 61000-6-2)

DIN EN 61000-4-3:2010/DIN EN 61326-1:2013 (DIN EN 61000-6-1)

DIN EN 61000-4-4:2010/DIN EN 61326-1:2013 (DIN EN 61000-6-2)

DIN EN 61000-4-5:2006/DIN EN 61326-1:2013 (DIN EN 61000-6-2)

DIN EN 61000-4-11:2004/DIN EN 61326-1:2013 (DIN EN 61000-6-2)

Safety (Low Voltage Directive): EN 61010-1:2001

Environmental Aﬀairs: EN 50581:2012

Articles manufactured on or after the Date of Issue of the Declaration of Conﬁrmity do not contain

any of the restricted substances in concentrations/applications not permitted by the RoHS

Directive.

July 25, 2016

Oldenburg, Germany

Axel Kortschack

Managing Director

1with active PS-BOB-V1.0-TAB the emission Class is A

PicoScale User Manual

2 PRODUCT SAFETY

2.5 Intended use

The PICOSCALE Controller is intended to be used in indoor locations with constant temperatures

inside the speciﬁed range (see table 2.2). Temperature ﬂuctuations can have inﬂuence on laser

stability and measurement results and should be kept small (e.g., avoid exposure to direct sun-

light).

Table 2.2: Operation conditions for PICOSCALE Controller

General Conditions

Power supply 90-246 VAC @ 47-63 Hz

Input current 0.5 ARMS @ 230 VAC

Environment Pollution degree 2; Indoor location

Environmental temperature 15 °C - 30 °C

Environmental humidity 5% to 80% RH, non-condensing

Storage temperature 0 °C - 50 °C

2.6 Unpacking

Before unpacking the PICOSCALE Controller please refer to chapter 6 of this manual.

2.7 Disposal of old equipment

According to the EU directive 2012/19/EU, as of August, 13, 2012, electrical and electronic equip-

ment may not be disposed in the member states of the European Union with other waste.

SmarAct GmbH respects the manufacturer’s prod-

uct responsibility and will take care of environmen-

tally correct disposal of old SmarAct products free of

charge. To dispose old SmarAct equipment, you can

return it to SmarAct to the following address postage-

free:

SmarAct GmbH

Schütte-Lanz-Strasse 9

26135 Oldenburg, Germany

PicoScale User Manual

3 PICOSCALE FUNDAMENTALS

The PICOSCALE is a powerful system for optical and non-invasive displacement and vibration

measurements. The three channel system is based on a miniaturized Michelson interferometer.

The system features powerful interfaces and ﬂexible software modules. Due to useful accessories

the system can be adapted to speciﬁc needs. The PICOSCALE GUI allows to operate the system

out of the box. In summary, these versatile characteristics make the PICOSCALE a very powerful

tool for every lab!

3.1 General setup and basic components

Each PICOSCALE measurement setup requires a few basic components. The PICOSCALE con-

troller is the core component. In the controller, coherent light is generated by a laser diode. A

ﬁber network distributes the laser light into three output channels.

Sensor head

Reference

mirror

Target mirror

Working distance

Optical fiber

PICOSCALE

Figure 3.1: Basic setup of a PICOSCALE displacement measurement. Miniaturized sensor heads

are connected to the PICOSCALE controller via optical ﬁbers. The system measures

the displacements of a target mirror relative to the sensor head.

Up to three sensor heads can be connected to the controller via optical FC/APC-terminated ﬁbers.

Within the sensor head, the laser light is divided into a reference and a measurement beam by

a beam splitter, being the central component of a Michelson interferometer. In standard sensor

heads one side of the miniaturized beam splitter cube is coated with a reﬂective coating, which acts

as reference mirror. The measurement beam exits the head and is reﬂected by the measurement

target, which can be a mirror, a piece of glass or almost any other technological relevant surface.

Both, the reﬂected reference and measurement beam interfere in the center of the beam splitter

cube and the combined light is guided back to the controller. Due to advanced signal processing

methods, based on lock-in detection and fast FPGA based evaluation algorithms, the PICOSCALE

is able to measure target mirror displacements with single picometer resolution and sample rates

of up to 10 MHz.

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3PICOSCALE FUNDAMENTALS

3.2 Measurement principle

3.2.1 Michelson interferometer

The PICOSCALE displacement sensor is based on a Michelson interferometer with an extremely

compact and stable reference arm. .

λ/4 λ/2

Interferometer

signal

Displacement

vanishing

sensitivity

high

sensitivity

Sensor head

Target

mirror

Figure 3.2: Measurement principle of a Michelson interferometer. Constructive and destructive

interference occur due to a displacement of the target mirror. To circumvent these

blind spots the PICOSCALE utilizes sinusoidal phase modulation, see section 3.2.2.

The interferometer is driven by a laser, which is a coherent light source, that is required if a

Michelson interferometer is operated with (very) unequal arm lengths as it is the case for the

PICOSCALE. At a beam splitter, the light is divided into two parts. One part is reﬂected at a ﬁxed

reference mirror and guided back to the beam splitter. The other part of the light hits the target

mirror. This light is also reﬂected while picking up a relative phase with respect to the reference

beam. Inside the beam splitter, both reﬂected beams interfere and the coherent superposition is

recorded by a photo detector.

In the PICOSCALE system, the beam splitter is located in the sensor head, whereas the light

source, a stabilized, distributed-feedback (DFB) laser diode and the photo detector are located in

the controller housing. The wavelength of the laser is around 1550 nm. Inside the controller, a

ﬁber network distributes the laser light to three independent measurement channels. The output

power of each channel is around 150 µW.

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3PICOSCALE FUNDAMENTALS

The integration of the miniaturized beam splitter into the sensor head ensures that changes in the

ﬁber length, possibly caused by temperature gradients, do not aﬀect the measurement.

In a Michelson interferometer, two light beams interfere with each other. Due to path length

diﬀerences in the measurement and the reference arm of the interferometer, constructive and

destructive interference occur. In case of constructive interference, the recorded interferometer

signal is high, while at destructive interference the recorded signal is low. A displacement of the

target mirror causes a change in the relative optical path lengths and thus in the phase diﬀerence

of target and reference beam, compare ﬁgure 3.2. As a result, the intensity measured by the photo

diode is changed. This intensity change in turn is used to infer positions and displacements with

high accuracy.

In standard interferometry, the interference signal is sinusoidally dependent on the phase diﬀer-

ence between the reference and probe beam. This phase diﬀerence depends on the target mirror

position. Thus, during constant movement, the resulting intensity signal is a sinusoid, similar to

the signal shown in ﬁgure 3.2. Due to the symmetry of the sinusoid, it is not possible to determine

the movement direction at every working point. Furthermore, the sensitivity (change in signal in-

tensity due to change in target position) is not constant during movement. Thus, for long range

and high-resolution position measurements, the standard Michelson interferometry is not ideally

suited.

The PICOSCALE uses sinusoidal phase modulation of the laser beam to overcome these disadvan-

tages and provides high accuracy and resolution of position measurements as well as information

on the direction of the moving object mirror!

3.2.2 Sinusoidal phase modulation

Figure 3.3: Quadrature signal detection: points of low sensitivity in one signal are compensated by

high sensitivity in the quadrature signal.

Thus, sinusoidally modulating the wavelength of the laser light can overcome the aforementioned

disadvantages. This wavelength modulation is initiated by modulating the injection current of

the used distributed feedback (DFB) laser diode. The modulation of the wavelength produces

a sinusoidally phase modulated (SPM) interference signal. Due to appropriate demodulation, it

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3PICOSCALE FUNDAMENTALS

becomes possible to extract the quadrature signal, which is a two dimensional signal, dependent

on the target mirror position, depicted in ﬁgure 3.3. The two extracted sinusoidal signals are

phase-shifted by 90 degrees and thus are in quadrature. The X and Y components are shown in

ﬁgure 3.3, left. Constant movement of the target mirror produces a circle in a two dimensional

representation. The right part of the ﬁgure shows both signal components simultaneously and

it can be seen that any blind spot in one signal is compensated by a high sensitivity point in the

other. Thus, the sensitivity is maintained high during movement.

Furthermore, the phase relationship between the two components allows to unambiguously in-

fer the movement direction. While an increasing relative position of the target mirror leads to

a counter-clockwise rotation of the X-Y vector, a decreasing position leads to a clockwise rota-

tion. Thus, sinusoidal phase modulation interferometry is perfectly suited for high-resolution,

long-range position measurements.

3.2.3 Working range

During the initial adjustment phase it is required to deﬁne a so-called working range. This is the

region where the target mirror is expected to be during the measurement. The setting of the

working range is mapped to internally stored conﬁguration values and an appropriate setting sub-

sequently leads to highest accuracy and performance of the PICOSCALE position measurements.

3.3 Traceability

Although the DFB laser has a very high spectral purity, spectral width below 10 pm, the emitted

wavelength is not constant due to unavoidable thermal drifts. Since the measured target position

is directly dependent on the emitted wavelength, a feedback system stabilizing the wavelength of

the DFB laser is mandatory. In order to stabilize the temperature of the laser diode, it is equipped

with a thermo-electric cooler (TEC). Besides stabilizing the temperature, the TEC element can be

used to actively control and tune the temperature and thus the emitted wavelength. The wave-

length is locked to an absorption line of a gas absorption cell, according to the standards NIST

SRM 2517a or SRM 2519a. This reference cell is ﬁlled either with acetylene or hydrogen cyanide

and allows to determine the wavelength of the laser within a range of lower than ±1 pm. The gas

absorption cells are extremely insensitive to environmental parameters like temperature, humid-

ity, pressure and also on electro-magnetic ﬁelds. Thus, these cells oﬀer a persistent and reliable

wavelength standard to stabilize the wavelength of the DFB laser diode.

The gas absorption cell is integrated in the PICOSCALE controller housing. One part of the mod-

ulated laser light is guided through the reference cell and the transmitted signal is recorded and

evaluated. A feedback loop controls the laser chip temperature such that the wavelength is con-

tinuously kept at an absorption line.

3.4 Environmental compensation

When the interferometer is used in a vacuum environment, no environmental compensation is

necessary. When the interferometer system is operated in ambient conditions, variations in the

PicoScale User Manual

3PICOSCALE FUNDAMENTALS

refractive index of the air can signiﬁcantly inﬂuence interferometric position measurements. The

refractive index of air may change due to ﬂuctuations in temperature, pressure and humidity

(TPH). If the refractive index increases, the optical path length of the laser light increases propor-

tionally. This eﬀect would pretend a movement of the object mirror even if the geometrical path

did not change. To compensate a variation of the refractive index, it is necessary to measure the

atmospheric conditions such as air temperature, pressure and humidity. Based on these values,

the National Institute of Standards and Technology (NIST) suggests a formalism based on a set

of modiﬁed Edlén equations to calculate the refractive index of air1. The PICOSCALE follows the

suggested formalism to calculate the refractive index and thus to correct the position data.

3.4.1 Dead path

The dead path is the distance between the absolute and relative zero position of the PICOSCALE

system. As ﬁgure 3.4 highlights, the absolute zero position is at the surface of the beam splitter

cube. The relative zero position can be deﬁned freely. The system measures any position change

Sensor head

Reference

mirror

Target mirror

Optical fiber

absolute Position

relative Position

-D

D+X

X

Figure 3.4: The dead path is the distance between the absolute zero position, at the front face of

the beam splitter cube and the freely deﬁned relative zero position.

relative to this internal zero position. When the measurement is done in ambient environment,

the changes in the refractive index cause a measurable change in the PICOSCALE position signal.

Based on the recorded environmental parameters the system calculates a correction factor to

compensate this virtual drift. The PICOSCALE measures the absolute distance between sensor

head and target mirror during the initial adjustment phase. When the absolute measurement

is done, the controller automatically zeros the internal position value, such that the measured

absolute distance is equal to the dead path. The measured dead path is stored automatically in

the system and can be accessed with appropriate properties. Furthermore, each time the internal

position value is set, the dead path is updated automatically, if the environmental compensation

is active.

1http://emtoolbox.nist.gov/Wavelength/Documentation.asp#EdlenorCiddor

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4BASIC CONCEPTS

4.1 Modular architecture

The PICOSCALE is set up in a modular architecture to allow for highest possible ﬂexibility, un-

derstandability and eﬃcient maintenance. Each module has inputs and/or outputs that can be

conﬁgured by the user. The inputs may be outputs from other modules while the outputs can

either be directly linked to interfaces like the PICOSCALE Breakout-Box (BOB) or set up as input

for subsequent modules. This very open architecture allows you to set up sophisticated networks.

The PICOSCALE modules and their possible dependencies are depicted in ﬁgure 4.1. The func-

tionality of the modules can be summarized as follows.

4.1.1 Advanced trigger

The Advanced Trigger module is a versatile tool that allows control of a variety of other modules.

Within this module, triggers can be conﬁgured that can be used as start or stop events for other

modules (Clock Generator, Counters, Signal Generator, Stream Generator) or they can be directly

displayed through the GPIO interface. Several data sources can be used within the Advanced Trig-

ger module to conﬁgure the respective events. Beyond others, position data, data increments or

external data (through the GPIO interface) can be used to conﬁgure trigger sources. Furthermore,

trigger sources can be linked with logical operations to allow for sophisticated trigger conﬁgura-

tions. A detailed description of the Advanced Trigger functions can be found in section 7.3.

4.1.2 Stream generator

The data transfer between the PICOSCALE controller and the user PC is called streaming. A so-

phisticated aggregation, compression and decompression protocol ensures highest possible data

rate of up to 480 Mbit/s so that position data, which is a 48 bit data source, can transferred with a

10 MHz rate.

The Stream Generator is the fundamental software module that handles PICOSCALE data

sources. Within this module you can conﬁgure the data stream to your PC (USB or Ethernet)

and set up the appropriate data rate as well as appropriate digital low-pass ﬁlters to avoid alias-

ing or unnecessary oversampling. The Stream Generator is connected to the trigger module so

that triggered data streaming can be set up. All functions of the stream generator can be con-

veniently be accessed via the PICOSCALE GUI. For example, start and stop trigger events can be

chosen and the number of frames to be acquired can be deﬁned. Details on the Stream Generator

conﬁguration can be found in section 7.6.4.

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Figure 4.1: Overview of all PICOSCALE modules and their possible dependencies.

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4 BASIC CONCEPTS

4.1.3 Digital and analog GPIO, AquadB

The general purpose input/output (GPIO) interface contains analog-to-digital (ADC) as well as

digital-to-analog converters (DAC) to digitize external signals and output data, respectively. For

example, it can output signals from the Clock Generator, Signal Generator, Calculation System

and the Advanced Trigger module. On the other hand, external signals can be interfaced with the

PICOSCALE. Thus, the GPIO interface allows to synchronize external devices with the PICOSCALE

and vice versa.

In combination with the Signal Generator module or Stream Generator module, function genera-

tor and oscilloscope functionality can be realized. Please refer to section 7.4.1 for details.

4.1.4 Clock Generator

The Clock Generator module can provide up to two clocks with user deﬁned frequency and phase.

Both clocks can be synchronized. Each clock generator may run in a direct mode or it may be

started and stopped by user deﬁned trigger events. Each clock can be used in the GPIO interface

for both digital and analog processing. A detailed description of the Clock Generator module can

be found in section 7.5.1.

4.1.5 Signal Generator

In the Signal Generator module pre-deﬁned shapes (sine, square, sawtooth) with user deﬁned

amplitude, oﬀset, phase and frequency can be conﬁgured that may then be used within the GPIO

interface. Furthermore, custom signal shapes can be uploaded to the module. A detailed descrip-

tion of the Signal Generator module can be found in section 7.5.2.

4.1.6 Calculation System

The Calculation System allows real-time processing of position data, GPIO data or environmental

data, for example. In total, three calculation systems can be conﬁgured and their output can either

be streamed or used in the GPIO interface. A detailed description can be found in section 7.5.3.

4.1.7 Counters

The Counter module allows to count either internal clocks (e.g., to use them as a timer) or trigger

events. This can be done either directly, or the counter can be started and stopped by triggers. In

total, two counters can be conﬁgured that may either be displayed in the Stream Monitor or they

may be used as source for trigger events. A detailed description of the counters is given in section

7.5.4.

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4 BASIC CONCEPTS

4.1.8 Environmental Module

The Environmental Module is an accessory that records temperature, humidity and the pressure

of the surrounding of the PICOSCALE. These data inﬂuence the refractive index of the air. By

tracking the environmental data the position data calculated by the PICOSCALE can be corrected

for the respective ﬂuctuations.

4.2 Data sources

Data sources are the basic data elements that provide data of any digital form over time. Position

of the target mirror, environmental temperature or GPIO data are data sources, for example. Data

sources that are related to each other are bundled into a channel.

The values of data sources may be retrieved from the device by streaming or polling them to the

user PC. The user may select a sub set of all available data sources and let the device stream the

values of these data sources over a period of time. An overview of all available data sources is

given in table 4.1.

Table 4.1: Overview of all streamable data sources. The data sources that are provided by the

modules are bundled into channel 1.

Channel 1 Channel 2 Channel 3

Position Position Position

Velocity Velocity Velocity

Acceleration Acceleration Acceleration

S(ω)raw S(ω)raw S(ω)raw

S(2ω)raw S(2ω)raw S(2ω)raw

S(ω)S(ω)S(ω)

S(2ω)S(2ω)S(2ω)

Counter 1&2

Env. module temperature

Env. module humidity

Env. module pressure

GPIO ADC 1-3

Calculation System 1-3

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4 BASIC CONCEPTS

4.3 Signal ﬂow

The PICOSCALE signals can be divided into three categories: optical signals, analog electrical

signals and digital signals. The basic and simpliﬁed signal ﬂow is shown in ﬁgure 4.2.

Figure 4.2: Signal ﬂow in the PICOSCALE.

At the beginning, an optical signal (light) is generated by a wavelength stabilized DFB laser diode.

The infra-red light is phase modulated with a frequency of ω=30 MHz and sent to the three sensor

heads. The interferometric signals generated in the sensor heads are detected by photo detectors

and converted into electronic signals.

The individual photo-electric signals are demodulated by both the modulation frequency and its

second harmonic (60 MHz). The resulting demodulation signals are digitized by analog-to-digital

converters (ADCs).

The digital signals are used to perform the position calculation. After appropriate ﬁltering, the data

stream is conﬁgured and the data are transferred to the user PC. You can select the desired data

sources and display them in graphs. Finally, the data can be exported to csv-ﬁles to be available

for data post-processing.

NOTICE

The position values, generated in the FPGA, have a resolution of 1 pm. Thus, all

internal modules, especially the Advanced Trigger System and the Calculation

System, process integer numbers with the unit picometer.

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4 BASIC CONCEPTS

4.4 Adjustment auto function

In the PICOSCALE auto functions are complex conﬁguration processes that, once triggered, au-

tomatically perform a sequence of internal routines to optimize the system performance. The

adjustment auto function performs certain procedures to achieve high accuracy of position data

and must be run once before measurement. It has three states:

•Disabled

By default the auto function is disabled.

•Manual Adjustment

In this state you have to adjust the targets that reﬂect the laser back into the sensor head

in order to get the highest possible signal quality. Once satisﬁed, the user must start the

automatic adjustment routine to complete the adjustment.

•Automatic Adjustment

In this state the device performs internal signal optimization routines to improve the accu-

racy of the position data. After this procedure, the activated channels will generate valid

position data and you can start measuring.

4.5 Events

In some situations events might occur that require further attention or reactions by the user.

To avoid that the status of the device has to be permanently checked, the PICOSCALE oﬀers a

notiﬁcation system that you may conﬁgure to your needs. By default, the most important alerts

are enabled.

For example, a beam interrupt event is produced if the probe beam is disturbed such that the

signal quality has fallen below a certain level. If at some point the signal quality is suﬃciently high

again, a beam restored event is sent. This information is important as you have to check if the

position data are still valid. Within the Advanced Trigger module, this event can be used as trigger

source which can be forwarded to a GPIO pin, for example. This way, you may react to unforeseen

incidents in the experimental setup and stop moving parts, for example.

4.6 System ﬁlters

Most PICOSCALE data sources are subject to low pass ﬁltering before they are provided to other

internal modules. Compared to depricated PICOSCALE ﬁrmware versions1, this has the advan-

tage that the following modules can operate with ﬁltered data:

•Calculation System. Data are ﬁltered before they can be processed in the module

•Advanced Trigger. Triggers can be set up to react on ﬁltered data

•Digital Diﬀerential Interface. Filtered data can be output via the AquadB or SD protocol

1In previous ﬁrmwares – older than 1.4.3 – the ﬁlters were implemented in the stream generator module. Therefore, only

data that were actually streamed via USB or Ethernet were subject to low pass ﬁltering. If data sources were used within

the Calculation System, Trigger System etc or output via AquadB interface, the data were suffering increased noise.

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4 BASIC CONCEPTS

NOTICE

When the data are streamed via USB or Ethernet, ﬁlter rate and frame rate have

to be matched. This is important as an inappropriate sample rate may lead to

oversampling or aliasing. In the PICOSCALE GUI, potential aliasing is indicated

by a small warning sign and the frame rate can easily be adapted to the ﬁlter.

NOTICE

When SmarAct’s motion controller MCS2 is connected, the ﬁlter rate is ﬁxed to

39.06 kHz to match the MCS2’s sample rate and thus to avoid aliasing.

4.7 Streaming aggregation

When data sources are streamed to the PICOSCALE via USB or Ethernet, the PICOSCALE usually

bundles a certain amount of data before it sends them. This so-called aggregation decreases the

communication overhead signiﬁcantly. If data are streamed with a speciﬁc frame rate, the PICO-

SCALE automatically uses a convenient aggregation size. This aggregation size is roughly set to

provide about 20 data packages per second. The protocol works most eﬃcient if the aggregation

size is a power of 2, i.e.

Aggregation =2n,n∈N

However, if an external clock is used as frame rate, the PICOSCALE cannot know the precise frame

rate and thus also an aggregation size cannot be estimated. The user has to set the desired aggre-

gation manually. In the following table please ﬁnd an overview on the frame rates and respective

aggregation size the PICOSCALE uses for direct streaming (i.e., an internal clock is used as frame

rate), which may serve as and rule-of-thumb to set the aggregation.

4.8 Network discovery protocol

The PICOSCALE network discovery protocol enables to list all available PICOSCALEs in your local

network. Within the PICOSCALE GUIyou may then easily select the appropriate device without

typing in the IP address after every startup of the PICOSCALE or restart of the GUI. See chapter 7

for usage of the protocol with the GUI.

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4 BASIC CONCEPTS

Table 4.2: PICOSCALE frame rates and corresponding aggregation sizes.

Frame rate Aggregation

10 / 5 / 2.5 / 1.25 MHz 1024

625 / 312.5 / 156.25 / 78.13 / 39.06 kHz 1024

19.53 kHz 512

9.77 kHz 256

4.88 kHz 128

2.44 kHz 64

1.22 kHz 32

610 Hz 16

305 Hz 8

152 Hz 4

76 Hz 2

38 / 19 / 9 / 4 / 2 / 1 Hz 1

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5PICOSCALE HARDWARE

Figure 5.1: Basic accessory, consisting of (1) PICOSCALE Controller, (2) sensor heads, (3) Environ-

mental Module, (4) One-Click cleaner and (5) User PC.

This chapter provides an introduction to the PICOSCALE Hardware. The basic accessories are

shown in ﬁgure 5.1. The main component is the PICOSCALE Controller. It is available as a table-

top version (1) and a 19" rack version. Up to three measurement heads (2) and an environmental

module (3) can be connected to the controller. Typically each PICOSCALE system is shipped with

some additional accessory (4) like a One-Click cleaner pen, head adapters, mirror mounts, etc.

Finally, a PC (5) is required. It is not part of the PICOSCALE system and must be provided by the

user.

5.1 PICOSCALE controller

The PICOSCALE Controller contains the laser source, various optics and detection electronics. It

furthermore holds the position calculation unit, which is a hybrid system with a high performance

FPGA and an embedded PC. This combination guarantees maximum ﬂexibility and highest perfor-

mance.

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5 PICOSCALE HARDWARE

Figure 5.2: (top) Front side of the PICOSCALE Controller with diﬀerent connectors for the (A) envi-

ronmental module, (B) external trigger connector, (C) sensor heads, (D) status LEDs, (E)

pilot laser and (F) power button. (bottom) Back side of the PICOSCALE Controller with

the (1) main power switch, (2) power connector (fuse included), (3) ground connector,

(4) GPIO and AquadB connector, (5) SmarAct sensor interface, (6) USB slave interface,

(7) SmarAct high-speed sensor interface, (8) USB master interfaces and (9) Ethernet

connector.

Figure 5.2 shows the front and back side of the PICOSCALE Controller. The front side exhibits

inputs for the environmental module (A), external trigger signals (B) and up to three measurement

heads (C). The environmental sensor is connected to the PICOSCALE simply by plugging the mod-

ule connector into the connector at the PICOSCALE housing. Red marks on the connector and

socket indicate the correct orientation.

The external trigger input is a BNC connector with an input range of [0,5] V. Internally, this trigger

input has a pull-up resistor (10 kΩ). Thus, the external trigger is always logically high when nothing

is connected to the input.

The optical inputs/outputs for up to three measurement heads are FC/APC connectors. It is impor-

tant, that only FC/APC connectors are used. Since these connectors have an 8◦-angled end face,

the orientation is crucial. Thus, the male connectors have keys, while the receptacles have corre-

sponding slots. It is mandatory to clean both, male and female connectors, with an appropriate

ﬁber cleaner (see chapter 6.3 for further information).

The status LED panel (D) oﬀers a convenient overview of the system state. At the top, three LEDs

indicate the channel valid status. A channel becomes valid after the PICOSCALE sensor head

adjustment and the corresponding automated optimization routines have been successful. At the

bottom, the ﬁrst LED indicates if the system is stable, which means that the wavelength of the

laser is actively stabilized. The PICOSCALE is ready for a measurement, if the desired channels

are valid and the system is stable. The next LED marks, if an active connection to an environmental

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5 PICOSCALE HARDWARE

module is established. The last LED indicates if the device is in standby mode. On the right hand

side of the front panel there is the pilot laser button (E) and the power button (F). Once the system

has fully booted, pressing the pilot laser button activates the red adjustment lasers of all three

channels. Active pilot lasers are indicated by the red LEDs integrated into the button. The power

button turns the system on (if it is in standby mode) or oﬀ. The two front panel buttons are also

used to update the controller ﬁrmware, see chapter 6.6.1.

On the left side of the back panel there is the main power switch (1). When the main power is

turned on, the device is in standby mode and can be started with the power button at the front

panel. Next to the main power switch, there is the power connector (2) with integrated fuse. The

allowed input voltage range is [90,246] VAC with a maximum current of 0.5 ARMS and an AC fre-

quency between [47,63] Hz. The power input is protected with a 2.5 A slow blow fuse. For very

sensitive measurement setups, the PICOSCALE oﬀers a PE socket (3) to reference connected de-

vices to the same ground potential. The GPIO and the AquadB interface (4) are available via a

D-Sub 44HD connector. For convenient access to all GPIOs and the DDIinterface, a Breakout-Box

(BOB) is available as accessory for the PICOSCALE Controller, which is connected via the 44 pin

connector. The PICOSCALE oﬀers two bidirectional, high-level interfaces, USB and Ethernet. For

USB connection, the user PC is connected to the USB slave interface (6), for Ethernet correspond-

ingly to the Ethernet jack (8). Additionally, two integrated USB master interfaces are connected to

the embedded PC. Via these interfaces a software update can be installed, for example.

Besides the main, high-level interfaces, the PICOSCALE oﬀers two low-level interfaces. The Smar-

Act SI(5) and SmarAct HSI(7) allow direct access of other SmarAct products to the PICOSCALE

data sources.

5.2 Interfaces

To work with the PICOSCALE Controller the system has to be connected to a PC. Therefore, a

USB 2.0 slave and a GBit Ethernet interface can be used. Both interfaces can be used at the same

time so that up to two users can connect to the system via Ethernet and USB. This allows that

data can be read out from several terminals at the same time. However, to prevent unintentional

reconﬁguration, only one user has full access and the ability to conﬁgure the system.

The PICOSCALE oﬀers a multitude of analog as well as digital interfaces to input or extract data

to and from the device, respectively. This guarantees a seamless integration in laboratory setups

with great ﬂexibility that goes far beyond interferometric position measurements.

5.2.1 Environmental Module interface

The Environmental Module is connected to the PICOSCALE Controller with a four wire interface.

The communication to the PICOSCALE Controller is realized by a UART protocol, and the power

supply of the Environmental Module is also provided by this interface.

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5 PICOSCALE HARDWARE

5.2.2 Optical outputs

CAUTION

Laser outputs. The PICOSCALE Controller contains an infrared diode laser with

an output of less than 0.2 mW at 1520 nm - 1580 nm and a red diode laser with

an output power of less than 0.6 mW at 650 nm. Do not stare into the beam and

ensure the laser light is always appropriately guided.

The PICOSCALE Controller has three optical outputs at the front panel of the chassis. Directly

after start up, the infrared measurement laser is enabled. This laser source has an output power

of maximum 0.2 mW per channel at a wavelength of 1520 nm - 1580 nm.

To improve the adjustment of the interferometer heads the PICOSCALE Controller provides the

possibility to switch on a red pilot laser with the pilot laser button on the front panel. The pilot

laser has a output power of max. 0.6 mW per channel at a wavelength of 650 nm. It has no

inﬂuence on the measurement of the PICOSCALE Controller.

5.2.3 Power connection

Connect the PICOSCALE Controller only with the provided IEC power cord and properly estab-

lished protective earth. After connecting the power cord use the main power switch to set the

system into standby mode. Finally press the power button on the front panel to start the system.

Change the main fuse

The PICOSCALE Controller is protected with a 2.5 A glass tube fuse with a slow blow timing be-

haviour. To prevent permanent damage or ﬁre, the fuse must only be replaced with an equivalent

fuse if required (e.g. ESKA No. 522.500). The dimension of the glass tube is 20 x 5 mm.

WARNING

To prevent electrical shock, remove the power cord from the PICOSCALE Con-

troller before replacing the fuse.

To change the fuse, remove the power cord and open the fuse holder (see ﬁgure 5.2). There are

slots for two fuses. The ﬁrst slot contains the active fuse, in the second slot a fuse for replacement

is included. Remove the damaged fuse and replace it with a slow blow 2.5 A glass tube fuse with

the dimension of 20 x 5 mm.

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5.2.4 USB slave interface

The USB slave interface is one of the main bidirectional communication interfaces of the PICO-

SCALE Controller. It provides a USB 2.0 high speed connection with data-rates of up to 480 Mbits/s.

5.2.5 Ethernet interface

The Ethernet interface is the second main bidirectional communication interface of the PICO-

SCALE Controller. The interface is conﬁgured via the embedded PC and is able to provide GBit

Ethernet. To use the full performance of the PICOSCALE Controller, a GBit Ethernet connection is

required.

5.2.6 USB master interface

The USB master interface is connected to the embedded PC. Via this interface software updates

can be installed, for example (see chapter 6.6.1 for more information).

5.2.7 SmarAct Sensor Interface (SI)

NOTICE

The SmarAct sensor interface is sensitive to electrostatic discharge. Please use

wrist straps when using this interface.

The SmarAct SIinterfaces the PICOSCALE Controller with other SmarAct products, e.g. the Mod-

ular Control System 2 (MCS2). In this conﬁguration the PICOSCALE Controller may act as sensor

module for the motion system.

5.2.8 SmarAct High Speed Sensor Interface (HSI)

The SmarAct HSIis an optional interface to connect other SmarAct systems with the PICOSCALE

Controller. This interface has the advantage that data can be transceived with data-rates up to

6.5 Gbit /s. This allows to perform very fast data processing with high resolution.

5.2.9 GPIO and Digital Differential Interface

The D-Sub 44HD connector provides several interfaces including analog and digital GPIOs as well

as Digital Diﬀerential Interfaces (DDI) for all three channels. Each DDIchannel can either act as an

AquadB or a serial interface. These additional interfaces make the PICOSCALE Controller a very

versatile laboratory measurement instrument as it provides the functionality of signal generators,

trigger systems, signal trackers and position measuring sensor in one device. This integration

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5 PICOSCALE HARDWARE

in one device also has the advantage that diﬀerent data sources are synchronized and can be

handled with a single tool.

For easy access to the signals we recommend to use the PICOSCALE Breakout-Box which is de-

scribed in chapter 5.3. It includes additional buﬀering of analog and digital IOs and splits the

D-Sub 44HD connector to BNC connectors. However, for direct access via the D-Sub 44HD con-

nector, please contact SmarAct for information on the pin assignments.

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5.3 Breakout-Box

Figure 5.3: Breakout-Box connectors overview.

The PICOSCALE Breakout-Box (BOB) provides simple and convenient access to the great variety of

signals at the DSub 44HD connector. The chassis of the Breakout-Box is the same as the chassis of

the PICOSCALE Controller and BOB can be stacked on top of a PICOSCALE Controller. Ventilation

holes of the PICOSCALE Controller are passed on to the Breakout-Box, so that heated air can

disappear freely. Do not cover the holes to prevent overheating of the PICOSCALE Controller!

The connectors on the top of the Breakout-Box are placed in three groups. AquadB outputs are

placed on the left hand side, digital GPIOs can be found in the center and analog GPIO pins are on

the right hand side (see ﬁgure 5.3). Analog and digital GPIOs can be connected via BNC connectors

while the AquadB signals are mapped to DSub 15 connectors.

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5.3.1 Differential Digital Interface DDI

The Diﬀerential Digital Interface (DDI) provides two diﬀerential digital signals, which can be used

for diﬀerent digital protocols, e.g. AquadB and Serial Data. With the Breakout-Box the signals are

distributed to three DSub 15 connectors, one per channel. The pin assignment is shown in ﬁgure

5.4 and speciﬁed in table 5.1.

Figure 5.4: Pin assignment of the DSub 15 connector.

Table 5.1 –Pin assignment of DSub 15 AquadB connectors

Signal Direction AquadB serial data

1 Out A positive CLOCK positive

2 Out B positive DATA positive

3 - 7 - not connected -

8 - System Ground System Ground

9 Out A negative CLOCK negative

10 Out B negative DATA negative

11 - 15 - not connected -

Shielding - System Ground System Ground

The output levels of the speciﬁc DDIpins are illustrated in ﬁgure 5.5. Main performance parame-

ters are listed in 5.2.

3.5

AquadB.X_P

AquadB.X_N

Figure 5.5: Output level of the speciﬁc pins of the AquadB connector, where the Xis to be replaced

by the individual channel number and quadrature (A or B). The indices Pand Ndenote

the positive and negative part of a diﬀerential AquadB pair.

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Table 5.2: Main performance data DDI

Parameter Typical Value Unit Comment

VODiﬀ 0 - 5 V Diﬀerential output voltage

VIHDiﬀ 0.2 V Diﬀerential high-level input voltage

VILDiﬀ -0.2 V Diﬀerential low-level input voltage

fmax 5 MHz Max. frequency per diﬀerential pair

BOB AquadB

Industry standard AquadB receivers are often able to receive diﬀerential quadrature signals as

provided by the PICOSCALE Controller. In ﬁgure 5.6 the AquadB signals are shown schematically.

With the signals A and B four states can be encoded, each state indicates a position increment. So

the maximal increment frequency is 4 times the maximum diﬀerential pair frequency, in this case

20 MHz.

Figure 5.6: Scheme of the diﬀerential A and B signal and the according position increment of the

Quadrature interface.

The direction of the position change is given by the order of the cases.

BOB Serial Data

Figure 5.7: Clock and data cyles on the serial interface. The CLOCK LINE can either have a negative

zero level or a positive zero level. The DATA LINE can either be written with rising or the

falling edge of the clock.

Each of the three DSub 15 connectors can be conﬁgured to act as a serial data output. Inﬁgure

5.7 the options are illustrated. The upper part of the ﬁgure shows the options of the clock line and

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5 PICOSCALE HARDWARE

the lower part shows the options of the data line.

• (CPOL 0): The CLOCK LINE has a negative zero level .

• (CPOL 1): The CLOCK LINE has a positive zero level.

• (CPHA 0): The DATA LINE is written with the beginning of each clock cycle.

• (CPHA 1): The DATA LINE is written at the center of each clock cycle.

Furthermore, you can choose the data idle polarity.

5.3.2 BOB digital GPIOs

The digital GPIOs are buﬀered on the Breakout-Box. The signals labelled with Digital1 - Digital4

have a 5 V high level, while the Digital5-Digital9 signals have a 3.3 V high level. All digital GPIOs

are matched with a 50 Ωserial resistor. The direction of the buﬀers is automatically set with the

direction of the digital GPIOs within the PICOSCALE Controller. Main performance parameters

are listed in table 5.3 (for the Digital 1-4 signals) and table 5.4 (for the Digital 5-9 signals).

Table 5.3: Main performance data BOB Digital 1-4 GPIO Buﬀer

Parameter Typical Value Unit Comment

VO0 - 5 V Digital 1-4 output voltage

VIH3.5 V High-level input voltage

VIL1.5 V Low-level input voltage

rising/falling edge ≦50 ns

Table 5.4: Main performance data BOB Digital 5-9 GPIO Buﬀer

Parameter Typical Value Unit Comment

VO0 - 3.3 V Digital 5-9 output voltage

VIH2 V High-level input voltage

VIL0.8 V Low-level input voltage

rising/falling edge ≦50 ns

Due to the limited bandwidth it is recommended to use the digital GPIOs with a maximum fre-

quency of 1 MHz. Using higher frequencies may cause asymmetries in the duty cycle of the signal.

Depending on the cable connected to the BNC connector the digital GPIOs can over-/undershoot

with up to 1 V. The best signal form can be achieved in a 50 Ωenvironment and with short connec-

tions.

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5 PICOSCALE HARDWARE

5.3.3 BOB analog GPIOs

The Breakout-Box buﬀers and normalizes the analog GPIOs to single ended signals with an ampli-

tude of ±10 V.

At the input ADC1 the single ended ±10 V signal is converted to a diﬀerential signal with an ampli-

tude equivalent to a full scale modulation of the ADC. Due to component tolerances, oﬀsets and

gains can vary slightly so that ±10 V is not exactly equivalent to the ADC’s resolution. For an ex-

act mapping of voltage to ADC resolution it is recommended to do a calibration of the ADC input.

The input impedance of the ADC1 input is approx. 2.4 kΩ. The inputs ADC2 and ADC3 input are

converted a diﬀerential signal. Again, it is recommended to do a calibration to get an exact map-

ping from voltage to ADC resolution. The input impedance is approx. 34 kΩ. For a performance

overview see table 5.5 and 5.6.

Table 5.5: Main performance data of ADC1

Parameter Typical Value Unit

Full-scale input voltage ±10 V

Sample-rate 10 MS /s

Resolution 16 Bit

Bandwidth f1dB 2-2.5 MHz

Table 5.6: Main performance data of ADC2 and ADC3

Parameter Typical Value Unit

Full-scale input voltage ±10 V

Sample-rate 100 kS /s

Resolution 16 Bit

Bandwidth f1dB 35-45 kHz

The Breakout-Box converts the diﬀerential DAC1 signal from the PICOSCALE Controller to a single

ended ±10 V output signal. The output can drive currents up to 35 mA and a capacitive load up to

33 pF. DAC2-DAC5 are the PICOSCALE DAC signals normalized to ±10 V.If a single DAC channel

is connected, it can drive currents up to ±30 mA and a capacitive load of up to 200 pF. With more

channels connected, the maximum current reduces correspondingly. For a performance overview

see table 5.7 and 5.8.

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5 PICOSCALE HARDWARE

Table 5.7: Main performance data of DAC1

Parameter Typical Value Unit

Full-scale output voltage ±10 V

Sample-rate 10 MS /s

Resolution 12 Bit

Bandwidth f1dB 2-2.5 MHz

Table 5.8: Main performance data of DAC2-5

Parameter Typical Value Unit

Full-scale output voltage ±10 V

Sample-rate 200 kS /s

Resolution 16 Bit

Bandwidth f1dB 130-170 kHz

5.4 Sensor heads

Figure 5.8: Selection of PICOSCALE sensor heads: (A) PS-SH-C01, (B) PS-SH-F01, (C) PS-SH-C03, (D)

PS-SH-C02.

The PICOSCALE interferometer sensor heads are based on an optical ﬁber, a ﬁber ferrule, a colli-

mator and a beam splitter cube. The optical ﬁber (single mode, minimum bending radius 10 mm)

is terminated with a 8◦ferrule. The angle is introduced to suppress parasitic interferences. A gra-

dient index (GRIN) lens (also with 8◦angle) is glued to the ferrule and used to collimate the laser

beam. The key component is the beam splitter cube. The beam is split into two parts. One part is

guided to the reference mirror that is coated to one of the surfaces of the cube. The other part is

guided to the target. Given proper alignment, the probe beam interferes with the reference beam

in the beam splitter cube. The interfering light is guided through the optical ﬁber back into the

PICOSCALE Controller, where it is detected by a photo detector and the interference pattern is

evaluated.

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5 PICOSCALE HARDWARE

Figure 5.9: Setup of a PICOSCALE sensor head.

The open port of the beam splitter cube is the SmarAlign window. In speciﬁc sensor heads (for

example sensor head type C01) it can be used as a monitor to superimpose the beams reﬂected

from the reference and target mirror, respectively, using the visible pilot laser beam that is dif-

fusely scattered at this surface. All standard components are mounted in a titanium sleeve.

5.5 Environmental Module

Figure 5.10: Environmental Module

To measure the environmental parameters (temperature, pressure, humidity), an environmental

module can be connected to the PICOSCALE Controller. Since the measurement of the environ-

mental conditions is most meaningful close to the sensor head, the environmental module has a

small chassis to make it possible to place it in close vicinity of the heads. The environmental mod-

ule is contained in an aluminum housing as small as 32x50x16 mm³. A microprocessor collects the

data of the individual sensors and sends them to the FPGA for further processing. The measure-

ment bandwidth is 1 Hz which is suﬃcient to detect variations in the environmental conditions.

The accuracy of the environmental module is:

•temperature: ±200 mK

•pressure: ±2 mbar

•relative humidity: ±2%

These measurement uncertainties result in a position accuracy of typically <1 ppm.

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6SETUP AND INSTALLATION

The following chapter describes the installation of a PICOSCALE system. Since many of the PICO-

SCALE components are fragile, please read and follow the information in this chapter carefully!

6.1 System checklist

If any cartons have been damaged, contact the shipper or SmarAct sales team at once. The ship-

ping boxes for a standard PICOSCALE interferometer should contain the following equipment

and documentation:

Table 6.1 –Components of a PICOSCALE System

Transport Case Image Dimension and Weight Content

Height x Width x Depth: (1) PICOSCALE Controller

15cm x 45cm x 40cm (2) USB Cable

Weight: (3) Power Cable

5.94kg (4) One-Click Cleaner Pen

(5) User Manual

(6) Software CD

Height x Width x Depth: (7) Sensor Head

4cm x 16cm x 15cm (8) Data sheet

Weight:

0.20kg

Continued on next page

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6 SETUP AND INSTALLATION

Table 6.1 – Continued from previous page

Transport Case Image Dimension and Weight Content

Height x Width x Depth: (9) Environmental Module

4cm x 16cm x 15cm (optional)

Weight:

0.3kg

Height x Width x Depth: (10) Breakout-Box

15cm x 45cm x 40cm (optional)

Weight: (11) BOB Cable

4.62kg (optional)

In case you have bought an in-vacuum system, there should be additional components like ﬁber

feed-throughs and ﬁber patch cords. A complete list of all PICOSCALE components and accessory

can be found on the SmarAct web page.

6.2 Unpack the system

1. Unpack the PICOSCALE system in an area that is clean and dry. Be very careful, especially

with fragile optical and vacuum components.

2. Check each shipping container to be sure you have removed all transport cases and addi-

tional items. Do not discard the reusable shipping containers until it is certain that all items

have been removed. It is recommended to keep the shipping containers in case you must

return any equipment to SmarAct.

3. Open each transport case and unpack the system components.

4. You are now ready to set up the system in the desired location.

6.3 Cabling

For the ﬁrst time installation, the PICOSCALE has to be connected via USB to the measurement

PC. Note, that the PC is not part of the system and has to be supplied by the customer separately.

Connect the included USB cable to the USB slave interface at the back side of the PICOSCALE

Controller (ﬁgure 5.2, No. 6) and to the desired USB port at the user PC. After that, connect the

power supply cable to the power connector at the back side of the controller (ﬁgure 5.2, No. 2).

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6 SETUP AND INSTALLATION

Next, connect the measurement heads to the corresponding adapters at the front side of the

PICOSCALE (ﬁgure 5.2, No. 4).

NOTICE

Glass ﬁber cables are very fragile and sensitive to bending. Please always respect

a minimum bending radius of 30 mm, unless otherwise speciﬁed.

NOTICE

Please note, that dirt attached to the ﬁber end-face can signiﬁcantly lower the

system’s performance or even destroy the ﬁber connector. In this case, the

PICOSCALE and/or the corresponding sensor head has to be sent back to Smar-

Act to get repaired.

To ensure optimal signal quality and also to prevent damage of the ﬁber surfaces, it is very impor-

tant to clean all connectors ﬁrst. This can be done using the One-Click cleaner pen which is part

of our shipment, cf. ﬁgure 6.1. Open the plastic cap and push the plastic tube onto the glass ﬁber

end piece until you hear a click. To clean the connectors on the PICOSCALE Controller or vacuum

feedthroughs, remove the plastic tube on top of the ﬁber optic cleaner and then repeat the same

process.

Figure 6.1: (left) Closeups of a clean (a) and dirty (b) ﬁber endface. Cleaning of the connectors and

sockets using the One-Click pen is illustrated on the right hand side.

Figure 6.1 (a) shows a close-up of a clean end-face, while image (b) shows dirt accumulated on

the end-face. On the right hand side cleaning of the ﬁber using the One-Click pen is illustrated.

For a detailed description of the One-Click pen please refer to the brief application note delivered

together with the tool.

When the ﬁber surfaces have been cleaned, gently plug the ﬁber connectors into the correspond-

ing sockets. The key of the connectors must slide into the matching slot in the socket (ﬁg. 6.2).

Then fasten the connectors by turning the coupling ring.

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6 SETUP AND INSTALLATION

Figure 6.2: Connection of sensor head.

NOTICE

The PICOSCALE ﬁber network consists of FC/APC connectors. Do not plug any

other optical connector types to the system or its subcomponents. This may

cause signiﬁcant damage to the optical system and dramatically drops the sys-

tem performance.

If purchased, connect the environmental module to the system front panel (ﬁgure 5.2, No. 1). A

red line and dot printed to the plug and connector mark the correct orientation. Place the sensor

as close as possible to the measurement head(s), to ensure that the sensor measures the local

environmental parameters, thus, reducing compensation errors.

The Breakout-Box (BOB) is connected using the included cable to the back panel of the PICO-

SCALE housing. Although the Breakout-Box is hot pluggable, it is recommended to connect BOB

before the system is switched on.

NOTICE

The included BOB cable is quite sensitive to bending, thus respect a minimum

bending radius of 50 mm. Please handle the large cable connectors with care

and ensure that no pins are bent prior plugging.

6.4 System power up

Connect the power cable and press the main power switch on the back side (ﬁgure 5.2, No. 1). Now

the standby LED at the front panel should be on, indicating an active power connection (ﬁgure 5.2,

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6 SETUP AND INSTALLATION

No. 4). Press the power button at the right-hand-side of the front panel to power up the system

(ﬁgure 5.2, No. 6). A green LED ring should now illuminate the power button. The status LEDs start

blinking, indicating the boot sequence of the embedded controllers. After a few seconds, the LED

blinking stops and the system is ready to use.

With the Pilot Laser button (ﬁgure 5.2, No. 5) at the front panel, an additional red laser can be

activated, which is very helpful during the alignment of the sensor heads.

6.5 PICOSCALE software and API installation

The PICOSCALE Software provides you with a graphical user interface (GUI) as well as an applica-

tion programming interface (API). For proper operation of the software Windows 7 or later should

be used.

The minimum requirement regarding the cpu is an Intel Core-i5 processor of the fourth generation

or similiar and 4 GB of RAM. Recommended is an Intel Core-i7 processor of the fourth generation

or similiar with at least 3GHz and 8 GB of RAM.

To install the PICOSCALE software and API, open the included software CD and start the installer

program PicoScale_Installer_<version>.exe. At ﬁrst, the installer dialogue presents some

important information about software and APIchanges. After conﬁrming these information, you

can select a destination folder (default: C:\SmarAct\). Lastly, you can select which components

should be installed. After the installer is ﬁnished the PICOSCALE software and documentation

can be found in the PICOSCALE folder in the destination path.

To uninstall the PICOSCALE software navigate to the Uninstall folder in the PICOSCALE main

folder. Execute the program unins000.exe. After the program is ﬁnished, the complete PICO-

SCALE software is removed from the system.

6.6 Firmware updates

SmarAct will release ﬁrmware updates for the PICOSCALE from time to time. Firmware updates

usually contain updated software that ﬁxes bugs, improves the system performance or adds new

features. Some ﬁrmware updates can be skipped, because later updates contain all the content

of earlier updates. However, some ﬁrmware version updates are required before later versions

can be installed. This holds for relatively old ﬁrmware versions. For example, if your PICOSCALE

has ﬁrmware version 1.0.5 installed, and you want to install version 1.1.7, you must ﬁrst update

to version 1.1.0 and then to 1.1.7. The following ﬁrmware versions have to be installed before

updates to more recent versions are possible:

•picoscale-1.1.0_2015-12-18_160315.fw (contains PICOSCALE ﬁrmware version 1.1.0)

•picoscale-2.0.0_2017-09-22_093253.fw (contains PICOSCALE ﬁrmware version 2.0.0)

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6 SETUP AND INSTALLATION

6.6.1 Performing a PICOSCALE ﬁrmware update

Firmware updates are ﬁles named like "picoscale-1.0.1__2015-12-01_160436.fw". The ﬁle

must be copied to a USB memory stick, which has to be plugged into one of the PICOSCALE

USB ports. For reducing problems, the stick should be empty (possibly freshly formatted) before

copying the new ﬁrmware to it.

Before starting the update process, the PICOSCALE has to be switched oﬀ. Hold the pilot laser

button and switch the device on, by pushing the power button. Do not release the pilot laser

button until it starts blinking, which indicates that the device is in the update or reconﬁguration

mode.

NOTICE

It is important that the update process is NOT INTERRUPTED by switching oﬀ

the power supply. Otherwise the device may become unresponsive and must be

sent in for repair!

The update process may take a few minutes (5-15). When it has ﬁnished, the device will be in its

normal operation mode and the pilot laser button should have stopped blinking.

NOTICE

In rare cases the update procedure does not ﬁnish after a few minutes. This

problem may occur when updating PICOSCALE Controllers with an installed

ﬁrmware version older than v1.1. If the pilot laser button does still blink af-

ter 30 minutes, please switch the device oﬀand on. The device will continue its

ﬁrmware update. During this phase, as described above, it must not be switched

oﬀ. Now, the update should ﬁnish after a few minutes.

Some ﬁrmware updates may also require an update of the programming interface libraries (SDK)

and the software tools for the PICOSCALE.

6.6.2 System diagnostics data

The PICOSCALE interferometer allows saving system diagnostics data (to a USB stick) for analysis

of problems. To save diagnostics data, start the device and plug in a USB memory stick. Wait until

it has booted and entered the normal operation mode. Hold the pilot laser button until it starts

blinking (this should happen after at most 10 to 15 seconds).

NOTICE

It is important, that the device is in normal operation mode, before the pilot

laser button is pressed!

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6 SETUP AND INSTALLATION

When the blinking has stopped, you may unplug the memory stick. On the stick you will ﬁnd two

ﬁles: "system.log" and "sysdiag_<uptime>_<bootcount>.dump".

"system.log" is a text ﬁle that contains a list of important system activities, like successful or failed

ﬁrmware updates. It may also include information about the reason why a system operation like

aﬁrmware installation has failed. The "system.log" can additionally be downloaded from the

device using the PICOSCALE Control GUI, see chapter 7.

The "sysdiag_<uptime>_<bootcount>.dump"ﬁle contains status data in a binary format that can

be sent to SmarAct for a detailed problem analysis.

PicoScale User Manual

7PICOSCALE CONTROL GUI

The PICOSCALE can be controlled with the LabVIEW based graphical user interface (GUI). It con-

tains all main functions to connect to a PICOSCALE system, to adjust it, read the device’s status,

conﬁgure all installed modules and, of course, read and process the data source values generated

by the device.

In this chapter the GUIfeatures are presented. First, it is shown how to connect to the device

via diﬀerent interfaces (USB and Ethernet) and read its status. Furthermore, the GUIexhibits an

adjustment panel, which guarantees a quick and easy adjustment of the PICOSCALE system with

user friendly auto-functions. Position data as well as other data sources can be displayed in the

the Stream Monitor.

Figure 7.1: PICOSCALE GUIoverview. (1) Menu (2) Connect to PICOSCALE (3) Adjustment, Envi-

ronmental Monitor and Stream Monitor (4) PICOSCALE Status (5) Interfaces, Modules

and Settings.

After the program is started you can see the HOME panel as shown in ﬁgure 7.1. All parts of

the GUIcan be reached from the HOME panel either by clicking on the corresponding buttons or

with the menu (1). All available PICOSCALEs are listed in (2). After connecting to the system the

adjustment and data streaming (3) as well as the PICOSCALE status (4) are available. All interfaces,

modules and the general settings can be centrally reached (5).

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7 PICOSCALE CONTROL GUI

7.1 Conﬁguration of the PicoScale

When starting the GUI, the HOME panel seen in ﬁgure 7.1 is opened. All elements of the GUIcan

be reached from here.

7.1.1 Connecting to the controller

The PICOSCALE is a multi-user system and up to two users can be connected to the same instru-

ment. Therefore, the device oﬀers two interfaces, USB and Ethernet. When more than one user

is connected to the instrument, the PICOSCALE requires one main user (full-access connection)

who can control the system and change properties, for example. The other user can only extract

data from the device.

Figure 7.2: Connect System menu.

You can connect to a PICOSCALE Controller in the Connect

System menu, shown in ﬁgure 7.2. When the GUIis started,

all PICOSCALE devices are listed with their ID-strings in the

Available PicoScale Systems menu. You can refresh the list

at any time with the reload button next to the drop-down

menu. The Device Info shows additional information on the

device like Device ID,Info about the system and IP address

of an Ethernet interface. Below this ﬁeld, you can check

whether a full-access connection should be forced. If the

Force Full Access check box is marked, all potentially exist-

ing full-access connections of other users are ignored and

a full-access connection is established. When this box is

unchecked, the GUIchecks if a full-access connection is al-

ready set up. If not, it establishes a full-access connection, if yes, the PICOSCALE GUIconnects

with limited access. The Full Access LED indicates if a full-access connection is established.

7.1.2 General settings

The basic setup of the system is located under General Settings in the Home panel. The PICO-

SCALE device generates user notiﬁcations, so-called Events. You can track these events to validate

received data or check the experimental setup, for example. In the Event Notiﬁcation menu you

can subscribe or unsubscribe to events. It is located on the left side in ﬁgure 7.3. Especially if

high streaming rates (close to 10 MHz) are used, it is recommended to unsubscribe from all un-

necessary events in order to guarantee optimal performance of the PICOSCALE GUI. Subscribing

or unsubscribing to a speciﬁc event can be done by clicking on the appropriate check box in the

Event Notiﬁcation menu. Furthermore, two buttons are available to subscribe or unsubscribe to

all events. After connecting to a PICOSCALE Controller, the GUIsubscribes to all events auto-

matically. Note that higher level events, such as streaming events, cannot be unsubscribed. For

detailed information on the event system, please refer to the PICOSCALE Programmer’s Guide.

The Network Conﬁguration menu at the center of ﬁgure 7.3 allows to deﬁne the Ethernet conﬁgu-

ration used by the PICOSCALE system. If you use the Ethernet connection for the ﬁrst time, we

recommended to connect the PICOSCALE Controller via USB, set up the desired Ethernet conﬁg-

uration and reconnect to the PICOSCALE Controller via Ethernet.

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7 PICOSCALE CONTROL GUI

Figure 7.3: General Settings: (left) Conﬁguration menu for Event Notiﬁcation. (center) Network Con-

ﬁguration. (right) Features Conﬁguration.

You may activate the Dynamic Host Conﬁguration Protocol (DHCP) if your server supports au-

tomatic assignment of IP addresses. If activated, the other ﬁelds are deactivated and have no

meaning. If DHCP is deactivated, a static IP Address, as well as other Ethernet properties like Sub-

net Mask,Gateway,Name Server and Domain Name can be conﬁgured in the appropriate panels.

Once all properties are deﬁned, the conﬁguration can be transmitted to the system by clicking on

the Store Conﬁg button. During transmission, the PICOSCALE checks the entered values, and if all

values are valid (indicated by the green LEDs), the desired conﬁguration is activated.

The PICOSCALE oﬀers chargeable ﬁrmware upgrades, such as the Advanced Trigger System, the

Signal Generators and the Calculation System.In the Features menu at the right hand side of ﬁgure

7.3, the available features are displayed in the Feature drop-down menu.

All chargeable features can be evaluated for a certain time. Generally, 10 time slots are available

and can be activated individually. Each time slot allows to evaluate the selected feature for 8

hours. The remaining evaluation time slots are displayed in the Remaining Evaluation Slots ﬁelds.

By clicking the Start Evaluation button, a new time slot is started.

If you decide to upgrade your system with the feature, please contact SmarAct. You will receive a

ﬁrmware upgrade and the feature time is set to inﬁnity automatically.

7.1.3 Status

The PicoScale status is located in the lower left part of the GUIand displays the current status of the

system. The red box (4) in ﬁgure 7.1 illustrates the location. The active channels are marked with

a green rectangle. The value Dead Path besides the active channels is calculated during the ad-

justment process and indicates the absolute distance between the measurement head and object

mirror.

The working range of the system is displayed below the channel indicator. If the target leaves

this range a new adjustment might be necessary. The Filter Rate describes a low pass ﬁlter that is

applied to position and ADC data and can be adjusted with the drop-down list. It can be switched

to the corresponding Cut-oﬀ Frequency using the button on the right side. The ﬁlter is implemented

in the FPGA and determines the system bandwidth.

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7 PICOSCALE CONTROL GUI

When the system recognizes optional components like the environment sensor, the Breakout-Box

and the MCS2, the rectangle besides the components is green. With the button Show Log the log

of the GUIcan be displayed. It shows log entries in case of system start-ups and displays error

codes. Each log entry is formatted with a date and time string and a clear text message. If the

last log entry was a system error message the Show Log button has red borders. The Clear button

deletes all log entries of the GUI.

Figure 7.4: System log of the PICOSCALE

controller

All ﬁelds in the PicoScale status are updated auto-

matically after connecting to a PICOSCALE sys-

tem. The system information is important for all

service requests.

The System Log of the PICOSCALE controller

shown in ﬁgure 7.4 is located in the menu bar un-

der Help.It contains a list of important system

activities like the activation of optional software

modules. It may also include information about

the reason why a system operation like a ﬁrmware

installation (cf. section 6.6.2) has failed. The infor-

mation can be relevant for service requests and

can easily be copied to the clipboard using the but-

ton Copy to Clipboard.

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7 PICOSCALE CONTROL GUI

7.2 Adjustment

Figure 7.5: PICOSCALE Adjustment Panel.

The three input channels of the PICOSCALE can be conﬁgured in the Adjustment Monitor. The goal

of the adjustment is to align the interferometer heads in front of the target mirrors and optimize

the signal quality. Furthermore, internal subsystems of the PICOSCALE device are optimized

to achieve highest possible resolution and accuracy of position measurements. Note that a full-

access connection has to be established to perform the adjustment procedure. Each channel can

be enabled and disabled with the corresponding check box below the graphs before the manual

adjustment is started. With the drop-down menu besides each check box the connected head type

can be conﬁgured. The head type is written on the housing of each head and in the corresponding

data sheet. For older heads, please use the standard head type C01.

On the upper left side of the GUIin ﬁgure 7.5 the ﬁber length can be changed. A standard sensor

head is delivered with a ﬁber length of about 1600 mm. If additional extension ﬁbers are used

the length should be inserted in the ﬁeld Extension ﬁber [mm]. Furthermore, the beam interrupt

tolerance can be set: The PICOSCALE generates so-called beam interrupt events when the signal

quality drops below a certain threshold. The PICOSCALE can be made more tolerant to these

events by increasing the value of the beam interrupt tolerance (default: 33%). A value of 100%

means that no beam interrupt events are produced any more.

Channel enabling/disabling and conﬁguration of the head type must be done before the adjust-

ment process is initiated, the beam interrupt tolerance can be set at any point.

The manual adjustment procedure is started by clicking on the Start Manual Adjustment button.

Figure 7.5 shows the Adjustment Monitor with one Lissajous graph for each channel after the man-

ual adjustment is started. Enter the expected working range (which inﬂuences the modulation

amplitude) and conﬁrm it by clicking Set. The more precise you enter the expected working range,

the higher the accuracy of your measurement will be.

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7 PICOSCALE CONTROL GUI

Then you have to align sensor head and target mirror with respect to each other. To rate and

optimize the alignment, use the Lissajous graph and the signal quality bar.

NOTICE

The absolute number of the signal quality has no meaning. It is just a temporary

indicator which helps you to optimize the current alignment. It is dependent on

many factors so that it cannot be used for comparison with previous alignments

with slightly diﬀerent settings (working range, diﬀerent channels, etc.).

When the sensor head is tilted relative to the target mirror, the shape (diameter and thickness) of

the Lissajous ﬁgure as well as the signal quality change. However, during this alignment the signal

ampliﬁcation is actively adjusted, so that the signal amplitudes cover the whole ADC range. A

very sensitive way to optimize the orientation of the measurement heads is to "freeze" the analog

gains, by pressing the Freeze Gains button. In this case, the diameter of the corresponding Lissajous

ﬁgure changes due to tilting of the sensor heads and should be maximized. (If, during this process,

the Lissajous ﬁgure size exceeds the display, simply "unfreeze" and freeze the gains again.)

After the manual adjustment is done, start the automatic adjustment by clicking the Start Auto Ad-

justment button. During this phase, the channel electronics (gains, demodulation phases, etc.), as

well as the internal signal processing algorithms are optimized automatically. A Progress bar indi-

cates the status of the auto adjustment. The Results panel summarizes the results of the individual

subroutines of the adjustment process. To guarantee optimal performance, the enabled channels

should be valid and the system must be stable. The adjustment process can be aborted at any

time, simply by deactivating the Manual Adjust or the Auto Adjust buttons.

Figure 7.6: Results of the Auto Adjustment routine. All channels are valid and the laser is stable.

The label Optical indicated that optical pathlengths are measures, i.e. environmental

compensation is not active.

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7 PICOSCALE CONTROL GUI

7.3 Advanced Trigger

Figure 7.7: Block Diagram of the PICOSCALE Trigger System.

The Advanced Trigger System can be purchased as an additional feature for the PICOSCALE system

which allows to synchronize internal and external processes. Figure 7.7 shows the block diagram

of the Advanced Trigger System. The system oﬀers eight trigger sources (left side) which can be log-

ically combined to up to eight actual trigger output signals (right side). These signals may be used

by other internal sub systems or can be output by the GPIO interface to control and/or synchronize

external devices.

Each individual trigger source has an output signal, which can be logically HIGH or LOW. All trigger

source signals are stored in a trigger source state register to which all eight triggers have access.

Each trigger can combine several trigger sources by logical operations (AND, OR, etc.) which allows

to deﬁne very complex trigger logics. Additionally, the trigger signal can be delayed or debounced

to produce stable and reliable output signals that can be logically HIGH or LOW. The following sub

systems can use trigger signals:

•Stream Generator, see section 7.6

–start / stop / pause the data stream

–deﬁne the rate at which the data frames are generated

•Digital IO Interface, see section 7.4.1

–output trigger signals as TTL or CMOS signals

•Clock Generators, see section 7.5.1

–start / stop a clock generator

•Counters, see section 7.5.4

–start / stop / increment a counter

The advanced trigger system can be conﬁgured in the Advanced Trigger System panel of the PICO-

SCALE Control GUI.

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7.3.1 Trigger Source conﬁguration

Figure 7.8: Trigger Source Conﬁguration; highlighted by green boxes

A trigger source is a basic component in the FPGA, which may be conﬁgured to listen to speciﬁc

events and react in a speciﬁc way. The conﬁguration of a trigger source can be controlled within

the Advanced Trigger System panel. This enables access to speciﬁc properties, which are explained

in detail in the Programmer’s Guide. The table on the right part of ﬁgure 7.8 presents the values

of the corresponding trigger source conﬁguration properties, thus, providing an overview of all

enabled trigger sources.

In the center of ﬁgure 7.8 you can select one of the eight available trigger sources. You can then

select the desired trigger source Event. This is the signal to which the trigger source listens to. The

meaning of the other ﬁelds depends on the chosen Event. The GUIdisables unnecessary ﬁelds

and updates the names of the controls.

Trigger Event None

The ﬁrst Event is None. This event disables a trigger source and its output will remain in the logical

LOW state. All other register ﬁelds are not used and have no meaning.

Trigger Event Software

The Software event performs a state change of the trigger source when a software event is re-

ceived. To generate a software event, the APIoﬀers a special trigger source property Software

Trigger, which can be addressed using the Property Dialog (see section 7.9). For this event, the

Index 0 register holds the Software Trigger ID, a number that is compared to the trigger ID given

by the software event. On a match the trigger source switches to the state given by the property

value.

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Trigger Event Data Source Value

The Data Source Value event performs a state change of the trigger source output when a data

source value passes a certain threshold or enters a certain range. Please note that not all data

sources are available. The possible data sources are restricted to position, Calculation System

outputs, ADCs and counters. The Condition menu allows to deﬁne how the selected data source

value and the conﬁgured threshold(s) are evaluated. The following conditions are available which

are illustrated in ﬁgure 7.9 and 7.10:

•Single Rising/Single Falling: The trigger source output is HIGH when the selected data source

value passes the Threshold from below/above. Once the trigger source is in a logically high

state, it stays high until reset.

•Single Either: The trigger source output is HIGH when the selected data source value passes

the Threshold from below or above. Once the trigger source is in a logically high state, it stays

high until reset.

•Positive/Negative Level: The trigger source is HIGH when the data source value is above the

Threshold and is LOW when the data source value is below the Threshold. For the negative

level it is vice versa.

•Positive/Negative Range: The trigger source is HIGH when the data source value is inside the

range deﬁned by the Lower and Upper Threshold and LOW otherwise. For the negative range

it is high when the data source value is outside the speciﬁed range.

Figure 7.9: Summary of trigger conditions. Two traces of a data source are shown (position, for

example) with a user deﬁned threshold. The trigger conditions single rising, single falling,

single either, positive level and negative level are illustrated.

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Figure 7.10: Summary of trigger conditions. The trigger conditions positive range and negative range

are illustrated, which both require an upper and lower threshold to deﬁne the appro-

priate range.

The next ﬁeld Data Source allows for selecting the desired data source. With the last two ﬁelds the

Thresholds for the selected condition can be deﬁned.

Trigger Event Data Source Increment

The Data Source Increment event generates positive pulses (a state change from LOW to HIGH

and back again) on the trigger source output whenever a certain increment of a data source value

is detected. A start Threshold can be deﬁned and after the data source passes this value, the

threshold register is incremented by the deﬁned Increment value. Please note, that not all data

sources are available. The Condition menu allows to deﬁne how the selected data source value and

the conﬁgured threshold/increment tuple are compared to each other. The following conditions

are available:

•Single Rising/Single Falling: A pulse is generated when the selected data source value passes

the Threshold from below/above. When this happens the Threshold is incremented or decre-

mented by the Increment value.

The next two ﬁelds, Channel and Source, allow for selecting the desired data source. Finally, you

can deﬁne the start Threshold and the Increment.

Trigger Event GPIO Trigger

The GPIO Trigger event listens to a speciﬁc GPIO input pin. To use a GPIO pin as trigger input

signal, the corresponding pin has to be deﬁned as input, cf. section 7.4. The Condition menu

allows to deﬁne how the trigger source reacts on the selected input pin. The following conditions

are available:

•Single Rising/Single Falling: The trigger source output is HIGH when a rising/falling edge is

detected on the selected input pin. Once the trigger source is in a logically high state, it stays

high until reset.

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•Single Either: The trigger source output is HIGH when a rising or a falling edge is detected on

the selected input pin. Once the trigger source is in a logically high state, it stays high until

reset.

•Positive Level,Negative Level: The level or the inverted level of the selected input pin is for-

warded to the trigger source output. In this case the state of the trigger source depends on

the level of the input pin.

The next ﬁeld Channel allows for selecting the desired input pin. The pin labels are in accordance

with the pin labels of the PICOSCALE Breakout-Box (BOB).

Trigger Event External Trigger

The Event External Trigger listens to the external trigger pin that is on the front panel of the PICO-

SCALE Controller housing. The Condition menu allows to deﬁne how the trigger source reacts on

the External trigger input pin. The following conditions are available:

•Single Rising/Single Falling: The trigger source output is HIGH when a rising/falling edge is

detected on the input pin. Once the trigger source is in a logically high state, it stays high

until reset.

•Single Either: The trigger source output is HIGH when a rising or a falling edge is detected on

the input pin. Once the trigger source is in a logically high state, it stays high until reset.

•Positive Level,Negative Level: The level or the inverted level of the input pin is forwarded to

the trigger source output, respectively. In this case the state of the trigger source depends

on the level of the input pin.

All other ﬁelds are not used and have no meaning.

Trigger Event Internal Event

The last Event,Internal Event, reacts to signals that are generated when internal events occur, for

example a Beam interrupt event. The Condition menu deﬁnes how the trigger source reacts on the

selected event signal. The following conditions are available:

•Single Rising/Single Single Falling: The trigger source output is HIGH when a rising/falling is

detected on the input pin. Once the trigger source is in a logically high state, it stays high

until reset.

•Single Either: The trigger source output is HIGH when a rising or a falling edge is detected on

the input pin. Once the trigger source is in a logically high state, it stays high until reset.

•Positive Level,Negative Level: The level or the inverted level of the input pin is forwarded to

the trigger source output, respectively. In this case the state of the trigger source depends

on the level of the input pin.

The next two ﬁelds, Event and Channel, allow for selecting the desired internal event and the cor-

responding channel. All other ﬁelds are not used and have no meaning.

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Trigger Reset

The two LEDs indicate the State of the trigger source. As explained above, the trigger source re-

mains HIGH when the selected condition is Rising,Falling or Either until it is reset. This means that

the trigger source is inactive and ignores further input changes. In this case the State LEDs show

Triggered.If the trigger source is ready and active, the LEDs show Armed.

If the trigger source is in the (inactive) Triggered state, the button Reset switches the trigger source

to logically LOW and activates the trigger again. The State LEDs will switch to Armed.

7.3.2 Trigger conﬁguration

Figure 7.11: Trigger Conﬁguration; highlighted by green boxes

Triggers logically combine the outputs of one or more trigger sources to generate an actual trigger

output signal. Each trigger has a set of registers, like AND Mask,OR Mask,Logic Operation, as well

as Output Mode and Output Delay. The PICOSCALE GUIallows to conﬁgure these registers. The

Trigger Index drop-down menu in the lower right corner of ﬁgure 7.11 allows to select a trigger.

For the trigger conﬁguration, an AND Mask and an OR Mask are available, where you can combine

all trigger sources with logical ANDs or ORs, respectively. The outputs of these two masks are

logically connected by another Logic Operation, to form the trigger output signal. The following

Logic Operations are available:

•Disabled Deactivates the selected trigger. The GUIautomatically removes the trigger from

the Active Trigger Conﬁguration tabular.

•OR: The output becomes LOW if both inputs are LOW. In all other cases, the output is HIGH.

•NOR or NOT OR The output becomes HIGH if both inputs are LOW. In all other cases, the

output is LOW.

•AND The output becomes HIGH if both inputs are HIGH. In all other cases, the output is LOW.

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•NAND or NOT AND The output becomes LOW if both inputs are HIGH. In all other cases, the

output is HIGH.

•XOR The output becomes LOW if both inputs are simultaneously HIGH or simultaneously

LOW. In all other cases, the output is HIGH.

•NXOR or NOT XOR The output becomes HIGH if both inputs are simultaneously HIGH or

simultaneously LOW. In all other cases, the output is LOW.

NOTICE

If you simply want to pipe through a trigger source as a trigger output signal,

select the corresponding trigger source in the AND Mask, do not select anything

in the OR Mask (so that its output is always LOW) and combine the two masks by

an OR operation in the Logic Operation.

Finally, you have to conﬁgure the Output Mode and Output Delay of your trigger signal. Some trigger

sources simply create short pulses or the trigger condition may be subject to high frequency state

changes. In order to debounce or widen the pulses you can select an appropriate Output Mode

as well as an Output Delay. The PICOSCALE oﬀers four diﬀerent Output Modes, which are also

illustrated in ﬁgure 7.12:

•Immediate No Reset: In this mode the output control logic forwards a change of the trigger

state immediately and the state is kept stable for the conﬁgured delay.

•Immediate Reset: In this mode the output control logic forwards a change of the trigger

state immediately and the state is kept stable for the conﬁgured delay. A state change during

this delay resets the delay counter.

•Delayed No Reset: In this mode the output control logic starts a delay counter when the

trigger state changes. State changes during this delay are ignored. At the end of the delay

the current state is forwarded.

•Delayed Reset: In this mode the output control logic starts a delay counter when the trigger

state changes. State changes during this delay are ignored, but cause the delay counter to

be reset. At the end of the delay the current state is forwarded.

Note that the output mode only takes eﬀect when a non-zero output delay is conﬁgured. When

the output delay is set to zero (default), the resulting trigger signal is identical to the input signal.

The output modes are divided into two categories, Immediate and Delayed.Immediate performs a

state change of the trigger output immediately after a state change of the input signal is recorded.

Delayed on the other hand keeps the current trigger state and waits for a certain time until the

trigger output reacts on an input signal state change.

The subcategories Reset and No Reset determine how the entered Output Delay is taken into ac-

count by the trigger system. Once a state change of the input signal is recorded, a delay counter is

started. In the No Reset case this counter runs independently of the input signal, thus deactivating

the trigger output for a ﬁxed time. In case of Reset, the delay counter is restarted every time the

input signal changes its state. Thus, this mode guarantees that the trigger output remains in its

current state until the input signal is stable for the deﬁned Output Delay time.

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Input

Immediate No Reset

Immediate Reset

(a)

Delayed No Reset

Delayed Reset

(b)

Figure 7.12: Trigger Output Control Behavior (output delay = 10). The input traces are the result

of the conﬁgured logic operation of the trigger and the eight traces below show the

resulting trigger signal for the four output modes. The ﬁrst input trace (a) shows some

short pulses (e.g. a steady low level with some noise) while the second trace (b) shows

a noisy transition of the input signal from low to high (similar to a trace of a mechanical

button when pressed).

In the middle of ﬁgure 7.11 the Active Trigger Conﬁguration table provides an overview of the con-

ﬁgured triggers. In this table the ﬁrst column displays the name of the active triggers. The next

two columns show the state of the eight AND and OR masks. The last three columns display the

chosen logic Operation, the output Mode and the output Delay.

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7.4 Interfaces

The Interfaces panel allows to conﬁgure the GPIO interface of the PICOSCALE system. It groups

the Digital IO,AquadB and the Digital-to-Analog (DAC) sub-panels.

7.4.1 Digital IO interface conﬁguration

Figure 7.13: Conﬁguration Menu of the Digital IOInterface.

The PICOSCALE oﬀers nine digital IO pins, which are directly connected to the FPGA controller.

The IO pins Digital 1 to Digital 4 are TTL ports and Digital 5 to Digital 9 are CMOS ports. They have a

voltage range of 0 to 3.3 V1. Each pin can be conﬁgured as input or as output pin and is accessible

via the D-Sub 44HD connector at the system back side or more conveniently via the Breakout-Box

(BOB). When the Digital 1 to Digital 4 pins are accessed via the Breakout-Box (BOB), their voltage

range is raised to 0 to 5V.

Figure 7.13 shows the Digital IO Interface Conﬁguration panel. Each pin can be conﬁgured individu-

ally. Digital 1 to Digital 3 are conﬁgured as Output ports, Digital 4 to Digital 9 are Input ports in this

ﬁgure.

The arrangement of the individual menus is equal to the pin arrangement of the PICOSCALE

Breakout-Box. Each pin conﬁguration has a drop-down menu in the bottom right corner, with

which the direction of the corresponding pin can be conﬁgured. The triangle in front of each LED

indicates whether the pin is conﬁgured as input or output.

On the left hand side of each panel three drop-down menus are available:

•Constant Level The output can be set to either logically HIGH or LOW.

1In PICOSCALE Controllers with the product codes PSC-CTRL-V1.0-TAB and PSC-CTRL-V1.1-TAB the signals GPIO.TTL*

have a 5V TTL level

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•Trigger Index A trigger (that has been deﬁned in the Advanced Trigger module) controls the

output of the pin. In the drop-down menu the respective trigger index can be chosen.

•Clock Gen. Index A clock as deﬁned in the Clock Generators conﬁguration controls the out-

put. In the corresponding menu it’s index can be chosen.

The switch to the right hand side of the three menus ﬁnally deﬁnes, if the conﬁgured manual state,

the trigger or the clock generator output controls the pin. Note, that the mentioned options are

pin output options and only have eﬀect, if the pin is conﬁgured as output pin. If a pin is conﬁgured

as output, e.g. Digital 1, the switch is connected to the triangle. While if a pin is conﬁgured as input,

e.g. Digital 4, the drop-down menus are not visible.

7.4.2 Digital Differential Interface (DDI) conﬁguration

Figure 7.14: Conﬁguration Menu of the Quadrature Interface.

The PICOSCALE oﬀers three DDIoutputs, which are accessible via the D-Sub 44HD connector at

the system’s back plane or more conveniently via the Breakout-Box (BOB). Each of these outputs

can be conﬁgured as a Quadrature (AquadB) or a Serial Data interface.

The source of each channel can be chosen by the Source drop-down list. Available are the options

Position, which provides position data, and CalcSys that maps the output of the calculation system.

In the top right corner of each menu, an Enable button allows to activate the output.

With the drop-down list Mode the Quadrature or the Serial Data option is selected.

Below the conﬁguration panels the principle of data representation is explained and the relevant

properties are deﬁned. Note, that since the PICOSCALE only measures relative position changes,

no AquadB index signal is available.

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Quadrature output (AquadB)

For each quadrature output a conﬁguration menu is available. It allows the conﬁguration of the

following paramters:

•Step Size The step size is entered in picometer (pm). Values between 1 pm and 1 cm are

accepted.

•Step Frequency. The drop-down menu allows to change the step frequency of the quadra-

ture interface with preset values ranging from 100kHz up to 20MHz.

The maximum target velocity is calculated by the PICOSCALE according to the conﬁguration of

the AquadB channel and displayed underneath the Step Frequency ﬁeld.

Serial data output (SD)

For each serial data output the conﬁguration menu allows the conﬁguration of the following pa-

rameters:

•Clock Frequency deﬁnes the data rate of the serial signal in Hz. It can be conﬁgured from

100kHz up to 10MHz.

•Clock Pause Delay deﬁnes a delay between two data words and is counted in clock cycles.

•Data Idle Priority deﬁnes the idle state of the data lines. It can be either low or high.

•Clock Mode deﬁnes the clock and data modes as described in chapter 5.3.1.

•Bitwidth deﬁnes the Bitwidth of a data word and the Shift.

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7.4.3 DAC interface conﬁguration

Figure 7.15: Conﬁguration Menu of the DAC Interface.

The PICOSCALE oﬀers ﬁve DAC outputs that can be conﬁgured in the DAC Interface panel. DAC

1 is a fast 10 MHz output channel with 12 bit resolution, DAC 2–5 have 16 bit resolution but their

sample rate is limited to 200 kHz. The corresponding bit widths and sample rates are displayed in

the bottom right corner of each conﬁguration panel.

Each DAC interface can be controlled by one of the following options, that can be selected via the

switch next to the drop-down menus:

•DAC Value A constant output with the speciﬁed value is generated. The range is [-1,1]

(ﬂoat64) corresponding to a ±10 Volt output.

•Calc Sys Index Select The result of the speciﬁed calculation system is mapped to the DAC.

•Sig Gen Index Select The signal generator with the speciﬁed index is mapped to the DAC.

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7.5 Modules

The PICOSCALE modules add much more versatility to your applications. These modules are the

Clock Generator module, the Arbitrary Signal Generator module, the Calculation System module and

the Counter module.

7.5.1 Clock Generator

Figure 7.16: Conﬁguration Menu of the Clock Generators.

The PICOSCALE oﬀers two digital clock generators, which can output frequencies from 1 Hz to

10 MHz. A clock generator can be used to simply output a clock via one of the GPIO pins, or it

can be used inside the advanced trigger system to synchronize internal data sources with external

processes, for example. In these applications, the PICOSCALE generates the master clock.

All clock generators are derived from the same master clock and can thus be synchronized. As

depicted in ﬁgure 7.16, each clock generator can be conﬁgured by a Frequency and a Phase Shift.

Enabling of each clock generator is done by the Enable button in the center of the each Clock Gen-

erator. Both generators can be synchronized to each other with a deﬁned phase shift by clicking

the Synchronize button on the left side of the window.

Continuous output of a conﬁgured clock is realized in the Direct mode of the clock generator.

However, when you want to control external devices by the PICOSCALE or vice versa, it is helpful

to start and/or stop the clock generators once appropriate trigger conditions are given. For this,

the Mode of the clock generator must be set to Triggered and the the corresponding start and stop

trigger indices deﬁned (cf. ﬁgure 7.16). The start and stop triggers are selected in the two drop-

down menus on the left side of each clock generator conﬁguration panel. The triggers can be

conﬁgured in the respective menu of the Advanced Trigger panel. If the Auto Reset Mode is enabled,

the clock generator will listen for another start trigger after receiving a stop trigger. Otherwise the

clock generator can only be restarted by disabling and enabling it again manually. The auto reset

mode has no meaning in the direct clock generator mode.

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7.5.2 Arbitrary Signal Generator

Figure 7.17: Conﬁguration Menu of the Arbitrary Signal Generators. In this example a frequency

modulation was uploaded as customized signal shape.

The PICOSCALE oﬀers basic signal generator functionality with sine, square and sawtooth shapes.

Additionally, custom shapes can be uploaded as CSV ﬁles. In the conﬁguration panel, see ﬁg.

7.17, you can conﬁgure up to ﬁve signals (corresponding to ﬁve DAC interfaces). For each signal

generator you can choose sine, square, sawtooth (P: slow positive ramp, N: slow negative ramp)

or custom shapes in the Shape drop-down menu.

The frequency of the signals can be chosen between 1 mHz and 2.5 MHz. Note, that only DAC1

has a high 10 MHz sample rate and may be used to output fast signals. DAC2–DAC5 are limited to

200 kHz sample rate. The amplitude can be set in a range between 0 and 1 and the oﬀset of the

signal can individually be set in a range between -1 and 1, where -1 corresponds to −10 V and 1

to 10 V. For example, a square signal with values between 0 and 5 Volt (i.e. TTL standard) can be

generated with the setting: shape Square, amplitude 0.25, oﬀset 0.25.

When more than one signal generator is used, the signals can be synchronized with each other by

clicking the Synchronize button in the upper left part of the Signal Generator panel.

In the Custom Shapes panel, up to ﬁve custom shapes can be uploaded from CSV ﬁles. The ﬁles

must consist of 212=4096 ﬂoat numbers (double, 64 bit) which represent the amplitude of the

signal at each point. Thus the numbers have to be in the range [-1,1]. (Decimal sign is "." and

the individual entries have to be separated by a line break.) The shape of the uploaded signal

is displayed in the graph. The Edit Shape button opens the Custom Shape Editor which allows to

deﬁne a custom signal shape by entering a formula or by uploading it from a CSV ﬁle.

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7.5.3 Calculation System

Figure 7.18: Conﬁguration Menu of the Calculation System.

Within the Calculation System you can perform basic calculations with data sources. Up to eight

calculation systems can be conﬁgured with the Calculation Systems drop-down menu in the upper

left part of the window.. First, you can deﬁne up to four operands (1.1–1.4). Each operand can

be a constant, a position/velocity/acceleration value from one of the three PICOSCALE channels,

an ADC value, a data source value from the environmental module (temperature, pressure or

humidity), signal generator outputs or a counter value. Then, you can sum up the four channels

or the minimum or maximum value can be calculated as deﬁned in the grey Operator 1 box. If, for

instance, a subtraction is required, the Negate Output button can be activated in order to multiply

an operand by -1 before performing the summation. The exact same operations can be performed

with a second branch of data by deﬁning operands 2.1–2.4 and Operator 2.In the third stage, the

results of Operator 1 and Operator 2 can be processed with Operator 3, resulting in a Calc Sys

Result.Operator 3 allows summation, subtraction, multiplication, division or Max/Min operation.

Alternatively, the inputs of Operator 3 can be set to a ﬂoat constant or the Calc Sys Result of another

calculation system.

In the exemplary operation as shown in ﬁgure 7.18 the calculation is set up to give

Calc Sys Result =Position 1 −Position 2

12000000000 .

By default, the result is simply forwarded to the 64 bit Calc Sys Output. However, it is possible to

map the result to a speciﬁc value deﬁned by a lookup-table (LUT). Note that in this case, the cal-

culation system result has to be in the range of [-1,1]. Results outside this range will be truncated.

The lookup-table needs to have 12 bit resolution (and thus has a length of 212=4096 points). The

result is interpolated based on those 4096 points to again give a 64 bit resolution. User deﬁned

LUTs can be uploaded as CSV ﬁles in the Custom Shapes panel. (Decimal sign is "." and the 4096

individual entries have to be separated by a line break.) Once a calculation system is conﬁgured,

it can be stored in conﬁguration slots for later usage by using the Module Conﬁgurations button.

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7.5.4 Counter

Figure 7.19: Conﬁguration Menu of the Counters.

The PICOSCALE oﬀers two Counters that may be used as a timer (counting FPGA clock cycles) or

as an event counter of trigger events, see ﬁg. 7.19. The counter trigger index can be set to one of

the eight trigger indices that can be conﬁgured within the Advanced Trigger module. If the Counter

Mode is set to Direct, the Counter simply counts when it is activated by the Enable CNT button in

the Counter Control panel. The Synchronize button in the upper left of the window enables both

counters simultaneously.

In the Triggered counter mode the counting starts in case of a Start Trigger event and stops in case

of a Stop Trigger event. Both can be selected on the left hand side of the conﬁguration panel. In

the selection of the Trigger Reset Mode, there are three options:

•Disabled Counting starts at the pre-deﬁned Start Value at a Start Trigger event and stops at

aStop Trigger event. Restart of the counter can only be done by disabling and enabling the

counter.

•Enabled Counting starts at the pre-deﬁned Start Value at a Start Trigger event and stops at a

Stop Trigger event. Another Start Trigger event, starts counting again from the counter value

stored from the preceding counting period.

•Reset Value Counting starts at the predeﬁned Start Value at a Start Trigger event and stops

at a Stop Trigger event. Another Start Trigger event, starts the counting again from the Start

Value, thus resets the preceding value.

The LED in the Counter panel indicates if a counter is currently running (LED green), oﬀ(LED oﬀ) or

armed (LED yellow). An armed counter means that the counter is waiting for a start trigger event.

The Reset Value button resets the counter to the corresponding start value.

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7.6 Streaming Monitor

Figure 7.20: Stream View Panel with two active streams.

For continuous data extraction from the PICOSCALE system, data frames can be conﬁgured and

afterwards streamed to the user PC. In the PICOSCALE GUIthe streaming interface can be con-

trolled and used within the Stream Monitor panel. Each panel can be undocked using the small

symbol next to the "STREAMMONITOR" headline so that you may move it to a diﬀerent screen, for

example.

7.6.1 Conﬁgure data receiver layout

Figure 7.21: Setting up a new data receiver layout.

PICOSCALE Control allows to deﬁne a great variety of diﬀerent plot layouts. When clicking the

Add button a new windows opens up and by sweeping over the desired pattern you can deﬁne a

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new panel. The more tiles you select, the smaller the individual plots will be as the pattern will be

scaled to the window. You may also want to name the new panel appropriately.

7.6.2 Setting up a data receiver

Each empty plot panel contains a Conﬁgure button that opens a Receiver Settings window shown in

ﬁgure 7.22.

Figure 7.22: Plot conﬁguration.

The drop-down menu Receiver Type allows to select the diﬀerent data streams that can be pro-

cessed and displayed. There are several types of data output possible:

•Timeplot A single plot window is shown plotting the data source(s) on the y axis over time

on the x axis.

•Timeplot (Stacked) Several timeplots (one per data source) are stacked over each other.

•XY Graph The XY graph requires two inputs. The ﬁrst stream is used for the x axis and the

second stream for the y axis. A Lissajous ﬁgure can be plotted using the data sources Sw

and S2w.

•Numeric A numeric output of the data stream.

•FFT (Power Spectrum) The power spectrum (PS) of one data source is calculated. You may

change to linear scaling (taking the square-root) of the power spectrum to display the am-

plitude spectrum (AS). Changing between PS and AS can be done be right-clicking into the

plot and selecting the appropriate scaling in the Spectrum Scaling selector. Units: If you, for

example, calculate the PS of a position data source, the unit will be m2.If you calculate the

AS of a position data source, the unit will be m.

•FFT (Power Spectral Density) The power spectral density (PSD) of one data source is cal-

culated, which is the power spectrum scaled by the noise equivalent bandwidth. The user

may change to linear scaling (taking the square-root) of the power spectral to display the

amplitude spectral density (ASD). Changing between PS and AS can be done be right-clicking

into the plot and selecting the appropriate scaling in the Spectrum Scaling selector. Units: If

you, for example, calculate the PSD of a position data source, the unit will be m2/Hz.If you

calculate the ASD of a position data source, the unit will be m/sqrtHz.

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7 PICOSCALE CONTROL GUI

•File The data stream is directed to a ﬁle. The data are stored in binary format but using the

included Data Reader you can convert them to *.csv ﬁles, see section 7.6.5. A header ﬁle is

stored as well containing information on frame rate and a time stamp. If you stop and start

the stream several times, this information is also stored in this ﬁle and you can isolate the

data block later.

The white text box in the middle of the Receiver Settings window shows the active data sources

for this plot. Sources can be added and deleted using the appropriate buttons. The drop-down

menus below the text box allow to select the diﬀerent channels and data types.

The available data sources have diﬀerent data types which are summarized in table 7.1.

Data source Data type Size [bit]

Position int48 48

Velocity int64 64

Acceleration int64 64

Sw Raw uint16 16

S2w Raw uint16 16

Sw uint16 16

S2w uint16 16

Counter 1–2 uint48 48

Env Sensor Temperature int32 32

Env Sensor Humidity int32 32

Env Sensor Pressure int32 32

GPIO ADC1–3 uint16 16

Calculation System 1–3ﬂoat32 32

Table 7.1: Overview of all data sources and their respective data types and sizes.

After selecting the Receiver Type and adding one or more data sources, the plot window is con-

ﬁgured using the Apply button. A plot is closed using the cross in the upper right corner of the

window.

7.6.3 Manipulate the data

The Clear all Plots button allows to clear the history of all active time plots simultaneously. For

most applications it is useful to zero the interferometer positions. This is achieved by clicking the

Set Zero Ch1,Ch2 and Ch3 buttons. To zero all channels simultaneously the Zero All button is used.

7.6.4 Conﬁgure the data stream

In the Settings region the Frame Rate drop-down menu changes the streaming frame rate to opti-

mize the data visualization corresponding to the experimental needs. You may choose data rates

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7 PICOSCALE CONTROL GUI

ranging from about 1 Hz to 10 MHz. The possible frame rates are dependent on the selected data

sources and the performance of your PC and network. Depending on the active data sources the

system automatically determines the maximum frame rate and corrects the displayed value in the

Frame Rate menu. You can also select triggers as frame rates so that you can use external clocks

for data sampling.

The Mode menu allows either Direct or Triggered streaming. In case of Triggered streaming the

Start and Stop triggers can be selected. After the stream is stopped by a corresponding trigger,

the stream generator in the PICOSCALE FPGA still sends a certain amount of data frames, speci-

ﬁed by the Post Frame Count value. After receiving a stop trigger the stream generator is disabled

and needs to be enabled again, if further stream data should be recorded. Thus after receiving a

stop trigger, a subsequent start trigger event does not activate the data stream again. However,

sometimes this is necessary. With the Reset on Stop function the stream generator can be auto-

matically reactivated/armed, after a stop trigger was received and the corresponding post frames

were acquired.

The streaming is started and stopped with the Enable button.

With the drop-down menu Filter Rate, in the PICOSCALE status window, a low-pass ﬁlter can be

selected, used to ﬁlter the data inside the FPGA before transmitting it. The button to the right

side of the Filter Rate changes the drop-down menu to the corresponding Cutoﬀ Frequency. The

Filter Rate and Frame Rate options should be set carefully to avoid aliasing. The system indicates

potential aliasing by a red logo on-top of the Frame Rate menu. By clicking on this logo, the Frame

Rate is automatically adjusted to meet the Filter Rate.

7.6.5 PicoScale Data Reader

Figure 7.23: PICOSCALE Data Reader. A data ﬁle has been loaded and the data are shown. Im-

portant information on frame rate and a time stamp are also given.

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7 PICOSCALE CONTROL GUI

The data reader can process the ﬁles you have streamed to your hard disk. As the data are stored

in binary format you may want to convert them to human-readable CSV ﬁles. Therefore, navigate

to the Data Reader via File →Read Stream Data File. Here, you can select the desired header ﬁle

which contains the necessary information on frame rates etc. By clicking the Export to CSV button

you can store the data in a human-readable ﬁle that can be used for further data processing.

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7 PICOSCALE CONTROL GUI

7.7 Environmental Monitor

Figure 7.24: Environmental Monitor.

The Environmental Monitor displays the temperature, humidity and pressure. When an environ-

mental module is connected to the PICOSCALE and the GUIsubscribes to the corresponding

event, temperature, humidity and pressure are recorded automatically. The inﬂuence on the mea-

surement can be corrected using the Deadpath Correction for the individual channels.

In the center of the display you ﬁnd the environmental values plotted over time. Above the plot

the current values are shown. The environmental module records data with approximately one

Hertz sampling frequency and each plot can hold 24 hours of measurement data.

On the lower left hand side, the Dead Path Correction can be activated. During adjustment the

PICOSCALE roughly determines the absolute distance between target mirror and sensor head

and automatically determines the current dead path. The Channel Dead Path [mm] panels show

the dead paths (in millimeters) of the active channels.

Only when the dead path correction is enabled, variations of the refractive index are taken into

account and used for correction of position data. The dead paths can also be updated manually

when you enter a new value and enable the dead path correction for the speciﬁed channel.

When user deﬁned environmental parameters are inserted on the lower right side of the window

a new adjustment described in chapter 7.2 will be necessary if you want to switch back to standard

dead path correction. For further details on dead path correction, please refer to section 3.4.

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7 PICOSCALE CONTROL GUI

7.8 Conﬁguration Manager

Figure 7.25: Conﬁguration Manager. The current settings can be stored in so-called conﬁguration

slots. Each conﬁguration slot can also be down- and uploaded to *.XML ﬁles.

The PICOSCALE allows to store speciﬁc conﬁguration settings to provide an easy and eﬃcient way

to proceed your measurements after a restart of the system. Therefore, there are eight conﬁgura-

tion slots available, that can be named freely. Each conﬁguration slot contains the settings of the

following modules:

•Advanced Trigger

•Calculation System, including look-up tables

•Clock Generator (*)

•Counter (*)

•Signal Generator, including custom shapes (*)

•Digital-to-analog converters

•Digital IO interface

•Digital Diﬀerential interface

(*) The outputs of these modules are disabled when the corresponding settings are loaded and

need to be enabled when needed. This prevents unintended signal output.

Once you have conﬁgured your system, you may store the settings in a conﬁguration slot which

can optionally be renamed. The conﬁguration slots are stored in the PICOSCALE internally. Ad-

ditionally, you may download the active conﬁguration (independently of the actual slots) to an

*.XML ﬁle. This ﬁle can be uploaded and several PICOSCALE controllers can thus be conﬁgured

the same way.

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7 PICOSCALE CONTROL GUI

7.9 Property Dialog

Figure 7.26: Properties dialog box.

Properties are conﬁguration values that deﬁne the behaviour of the device. The dialog can be

reached over the menu Navigation,Settings and Properties. Each property has a data type and

an access mode. Some properties may be read and written, while others are read only or (in

rare cases) write only. Within the Property Dialog, you can read or write these properties. For a

detailed description of the properties, please refer to the PICOSCALE Programmer’s Guide. Please

note that changing properties without due consideration may have signiﬁcant consequences in

the performance of the PICOSCALE.

PicoScale User Manual

8CONCLUDING REMARKS

In this manual the basic operation principles, hardware and software of a PICOSCALE system are

introduced. You should now be able to work eﬃciently with the PICOSCALE to perform position

measurements with high accuracy. However, the PICOSCALE functionality goes far beyond mea-

suring positions only. You may use it as a signal generator, timing module in your laboratory, data

acquisition, perform basic calculations with high speed and many others. A selection of possible

applications as well as summaries of key performances you can ﬁnd in the application notes on

SmarAct’s homepage or on request. SmarAct will constantly add more and more application notes

so it is worth checking the homepage regularly. You will also ﬁnd an overview of convenient acces-

sories there. However, if you do not ﬁnd solutions for your application directly there, please do

not hesitate to contact us. We will be very happy to help and try to ﬁnd a solution for your precise

measurement or implementation issue as quickly as possible.

We are convinced that the great versatility of the PICOSCALE oﬀers great potential for many high

precision metrology environments. Enjoy your PICOSCALE!

PicoScale User Manual

Sales partner / Contacts

Headquarters

SmarAct GmbH

Schuette-Lanz-Strasse 9

26135 Oldenburg

Germany

T: +49 441 – 800 87 90

Email: info-de@smaract.com

www.smaract.com

France

SmarAct GmbH

Schuette-Lanz-Strasse 9

26135 Oldenburg

Germany

T: +49 441 – 80 08 79 956

Email: info-fr@smaract.com

www.smaract.com

Israel

Trico Israel Ltd.

P.O.Box 6172

46150 Herzeliya

Israel

T: +972 9 – 950 60 74

Email: info-il@smaract.com

www.trico.co.il

Japan

Physix Technology Inc.

Ichikawa-Business-Plaza

4-2-5 Minami-yawata,

Ichikawa-shi

272-0023 Chiba

Japan

T/F: +81 47 –370 86 00

Email: info-jp@smaract.com

www.physix-tech.com

South Korea

SEUM Tronics

# 801, 1, Gasan digital 1-ro

Geumcheon-gu

Seoul, 08594,

Korea

T: +82 2 868 –10 02

Email: info-kr@smaract.com

www.seumtronics.com

USA

SmarAct Inc.

2140 Shattuck Ave. Suite 1103

Berkeley, CA 94704

United States of America

T: +1 415 –766 9006

Email: info-us@smaract.com

www.smaract.com

PicoScale User Manual

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