THORLABS TQD001 User manual

TQD001
Quad Detector
User Guide
Original Instructions

2 HA0185T Rev 9 Feb 2014
Contents
Chapter 1 Safety ............................................................................................ 4
1.1 Safety Information .................................................................................. 4
1.2 General Warnings .................................................................................. 4
Chapter 2 Overview and Setup ..................................................................... 5
2.1 Introduction ............................................................................................. 5
2.2 T-Cube Controller Hub ........................................................................... 6
2.3 APT PC Software Overview ................................................................... 7
2.3.1 Introduction .........................................................................................................7
2.3.2 APTUser Utility ...................................................................................................8
2.3.3 APT Config Utility ...............................................................................................9
2.3.4 APT Server (ActiveX Controls) .........................................................................10
2.3.5 Software Upgrades ...........................................................................................11
Chapter 3 Initial Installation ............................................................................
3.1 Install The Software .............................................................................. 12
3.2 Mechanical Installation ......................................................................... 13
3.2.1 Environmental Conditions ................................................................................13
3.2.2 Mounting Options .............................................................................................13
3.2.3 Removing the Baseplate ..................................................................................14
3.3 Electrical Installation ............................................................................. 15
3.3.1 Description of Input/Output Connections ..........................................................15
3.3.2 Supply Voltage and Current Requirements ......................................................16
3.3.3 Connecting To A Standalone Power Supply ....................................................16
3.3.4 Using The USB Controller Hub ........................................................................17
Chapter 4 Getting Started - Basic Operation ............................................ 18
4.1 Introduction ........................................................................................... 18
4.1.1 Overview - Typical System Example ...............................................................18
4.2 Detector Head Descriptions ................................................................. 19
4.2.1 PDQ80A and PDQ30C Quadrant Detector Heads ...........................................20
4.2.2 PDP90A Lateral Effect Sensor .........................................................................20
4.2.3 Use of the Sum and Difference Signals for Alignment .....................................21
4.2.4 Beam Size Considerations ...............................................................................22
4.2.5 Sensor Data Precision ......................................................................................22
4.2.6 Temperature Considerations ............................................................................22
4.3 Control Panel Buttons and Indicators .................................................. 23
4.4 Operating Modes .................................................................................. 24
4.5 Basic Application Example ................................................................... 27
4.5.1 Introduction .......................................................................................................27
4.5.2 Wiring and Initial Set Up ...................................................................................27
4.5.3 Basic Operation ................................................................................................28
4.5.4 Signs of Instability ............................................................................................30
4.5.5 Troubleshooting ................................................................................................30
4.5.6 Using the Target Display ..................................................................................31
Continued...

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T-Cube Quad Detector Reader
Chapter 5 PC Operation - Tutorial .............................................................. 33
5.1 Introduction 3...........................................................................................3
5.2 Building An Auto-alignment System - PC Operation ............................34
5.2.1 Introduction ...................................................................................................... 34
5.2.2 Wiring and Software Settings for Revision 1 Piezo Drivers ............................. 35
5.2.3 Using Revision 1 Piezo Drivers On The TCH002 Hub ..................................... 38
5.2.4 Wiring and Software Settings for Revision 2 Piezo Drivers - Hub Operation ... 39
5.2.5 Revision 2 Piezo Driver Hub Mounting Options ............................................... 43
5.2.6 Wiring and Software Settings for Revision 2 Piezo Drivers - Off Hub Operation 43
5.2.7 Basic Operation ............................................................................................... 45
5.2.8 Signs Of Instability ........................................................................................... 50
5.2.9 Troubleshooting ............................................................................................... 50
5.3 Creating a Simulated Configuration Using APT Config ........................51
5.4 Programmed Operation ........................................................................53
Chapter 6 Software Reference .................................................................... 54
6.1 GUI Panel .............................................................................................54
6.2 Settings Window ...................................................................................57
Appendices
Appendix A Connector Pinout Details ....................................................... 60
Appendix B PID Tutorial ............................................................................. 62
Appendix C Preventive Maintenance ......................................................... 63
Appendix D Specifications and Associated Parts .................................... 64
Appendix E APTQuad Control Method Summary ..................................... 65
Appendix F Regulatory ................................................................................ 67
Appendix G Thorlabs Worldwide Contacts ............................................... 71

4
Chapter 1 Safety
1.1 Safety Information
For the continuing safety of the operators of this equipment, and the protection of the
equipment itself, the operator should take note of the Warnings, Cautions and Notes
throughout this handbook and, where visible, on the product itself.
The following safety symbols may be used throughout the handbook and on the
equipment itself.
1.2 General Warnings
Shock Warning
Given when there is a risk of injury from electrical shock.
Warning
Given when there is a risk of injury to users.
Caution
Given when there is a risk of damage to the product.
Note
Clarification of an instruction or additional information.
Warnings
If this equipment is used in a manner not specified by the manufacturer, the
protection provided by the equipment may be impaired. In particular,
excessive moisture may impair operation.
Spillage of fluid, such as sample solutions, should be avoided. If spillage does
occur, clean up immediately using absorbant tissue. Do not allow spilled fluid
to enter the internal mechanism.

5
Chapter 2 Overview and Setup
2.1 Introduction
The TQD001 quadrant detector T-Cube is designed to work with the Thorlabs PDP
and PDQ series detector heads. As a member of the T-Cube family of controllers this
unit benefits from a unified ActiveX software interface, USB connectivity, very
compact footprint and compatibility with the T-Cube Hub System. It is particularly
useful in laser beam alignment, position monitoring and beam stabilization
applications.
The detector head outputs signals that sense the position and intensity of the light
beam hitting the photo detector array. The TQD001 allows monitoring of these signals
and gives a visual indication of the position of the beam, both via the top panel LED
display and the software Graphical User Interface (GUI).
The unit features three main operating modes - Monitor, Open loop and Closed loop.
In Monitor mode, the unit outputs the XDiff, YDiff and Sum signals from the detector
array for use in a monitoring application. In open loop the XOut and YOut position
demand output signals can be turned off, to allow the mirrors to be positioned
manually.
Furthermore, this quadrant detector T-Cube also benefits from a closed loop mode.
In closed loop operation the unit can be configured to drive out a pair of position
demand analog signals. In typical applications these signals can be used to control
the positioning of a motorized or piezo driven turning mirror in an optical system. The
DSP processor within the unit runs two independent feedback loops, one for each
axis of the quadrant detector head. These feedback loops attempt to zero out the X
and Y difference signals by manipulating the position of the turning mirror to centre
the beam on the quad detector head. Full PID parametisation of these feedback loops
allow the system to be tuned to a wide variety of beam alignment applications. For
convenience it is possible to configure 2 TPZ001 piezo T-Cubes as
slave amplifiers in
order to drive piezo mirror products such as the ASM003 and KC1-PZ.
Fig. 2.1 T-Cube Quad detector (shown without base plate fitted)

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Chapter 2
For convenience the footprint of this unit has been kept to a minimum, measuring only
60mm x 60mm x 47mm (2.4” x 2.4” x 1.8”) and with the facility to directly mount to the
optical table close to the device under control. Table top operation also allows minimal
drive cable lengths for easier cable management. All controls are located on the top
face of the unit – very convenient when manually adjusting devices and monitoring
the positions via the easy to interpret ‘Target’ display.
USB connectivity provides easy 'Plug and Play' PC controlled operation - multiple
units can be connected to a single PC via standard USB hub technology or by using
the T-Cube Controller Hub (see Section 3.3.4.) for multi-axis motion control
applications. Coupling this with the user friendly apt™ software (supplied) allows the
user to get up and running in a short space of time. Advanced custom motion control
applications and sequences are also possible using the extensive ActiveX®
programming environment also supplied. This programming library is compatible with
many development tools such as LabView, Visual Basic, Visual C++, C++ Builder,
LabWindows/CVI, Matlab and Delphi.
See Section 2.3. for a full description of the APT system software.
In the remainder of this handbook, the Tutorial sections (Chapter 4 “Getting Started -
Basic Operation” on page 18 and Chapter 5 “PC Operation - Tutorial” on page 33)
provide a good initial understanding on using the unit, and the reference section
(Chapter 6) covers all operating modes and parameters in detail.
2.2 T-Cube Controller Hub
As a further level of convenience when using the new T-Cube Controllers Thorlabs
also offers the T-Cube Controller Hub (TCH002). This product has been designed
specifically with multiple T-Cube operation in mind in order to simplify issues such as
cable management, power supply routing, multiple USB device communications and
different optical table mounting scenarios.
The T-Cube Controller Hub comprises a slim base-plate type carrier (375mm x 86mm
x 21.5mm, 14.75” x 3.4” x 0.85”) with electrical connections located on the upper
surface to accept up to six T-Cubes.
Internally the Controller Hub contains a fully compliant USB 2.0 hub circuit to provide
communications for all six T-Cubes – a single USB connection to the Controller Hub
is all that is required for PC control. The Controller Hub also provides power
distribution for up to six T-Cubes, requiring only a single power connection.
Important Note
For convenience and consistency, all system descriptions and examples
throughout this manual assume that the TQD001 is used with a pair of TPZ001
T-Cube Piezo Controllers. It is also possible to use the MDT693 or BPC202
controllers, or a 3rd party piezo amplifier, or even a non-piezo actuated
positioning element, as long as they have suitable low voltage external control
inputs and a manual adjustment facility.

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T-Cube Quad Detector Reader
2.3 APT PC Software Overview
2.3.1 Introduction
As a member of the APT range of controllers, the TQD001 Quadrant Detector shares
many of the associated software benefits. This includes USB connectivity (allowing
multiple units to be used together on a single PC), fully featured Graphical User
Interface (GUI) panels, and extensive software function libraries for custom
application development.
The APT software suite supplied with all APT controllers provides a flexible and
powerful PC based control system both for users of the equipment, and software
programmers aiming to automate its operation.
For users, the APTUser (see Section 2.3.2.) and APTConfig (see Section 2.3.3.)
utilities allow full control of all settings and operating modes enabling complete ‘out-
of-box’ operation without the need to develop any further custom software. Both
utilities are built on top of a sophisticated, multi-threaded ActiveX ‘engine’ (called the
APT server) which provides all of the necessary APT system software services such
as generation of GUI panels, communications handling for multiple USB units, and
logging of all system activity to assist in hardware trouble shooting. It is this APT
server ‘engine’ that is used by software developers to allow the creation of advanced
automated positioning applications very rapidly and with ease. The APT server is
described in more detail in Section 2.3.4.
Aside
ActiveX®, a Windows®-based, language-independent technology, allows a user
to quickly develop custom applications that automate the control of APT system
hardware units. Development environments supported by ActiveX® technology
include Visual Basic®, LabView™, Borland C++ Builder, Visual C++, Delphi™,
and many others. ActiveX® technology is also supported by.NET development
environments such as Visual Basic.NET and Visual C#.NET.
ActiveX controls are a specific form of ActiveX technology that provide both a user
interface and a programming interface. An ActiveX control is supplied for each
type of APT hardware unit to provide specific controller functionality to the
software developer. See Section 2.3.4. for further details.

8 HA0185T Rev 9 Feb 2014
Chapter 2
2.3.2 APTUser Utility
The APTUser application allows the user to interact with a number of APT hardware
control units connected to the host PC. This program displays multiple graphical
instrument panels to allow multiple APT units to be controlled simultaneously.
All basic operating parameters can be altered and, similarly, all operations (such as
switching between Monitor, Open Loop and Closed Loo modes) can be initiated.
Settings and parameter changes can be saved and loaded to allow multiple operating
configurations to be created and easily applied.
For many users, the APTUser application provides all of the functionality necessary
to operate the APT hardware without the need to develop any further custom
software. For those who do need to further customize and automate usage of the
controller (e.g. to implement a positioning algorithm), this application illustrates how
the rich functionality provided by the APT ActiveX server is exposed by a client
application.
Use of the APT User utility is covered in the PC tutorial (Chapter 5) and in the
APTUser online help file, accessed via the F1 key when using the APTUser utility.

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T-Cube Quad Detector Reader
2.3.3 APT Config Utility
There are many system parameters and configuration settings associated with the
operation of the APT Server. Most can be directly accessed using the various
graphical panels, however there are several system wide settings that can only be
made 'off-line' before running the APT software. These settings have global effect;
such as switching between simulator and real operating mode and incorporation of
calibration data.
The APTConfig utility is provided as a convenient means for making these system
wide settings and adjustments. Full details on using APTConfig are provided in the
online help supplied with the utility.
Use of the APT Config utility is covered in the PC tutorial (Chapter 5) and in the
APTConfig online help file, accessed via the F1 key when using the APTConfig utility.

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Chapter 2
2.3.4 APT Server (ActiveX Controls)
ActiveX Controls are re-usable compiled software components that supply both a
graphical user interface and a programmable interface. Many such Controls are
available for Windows applications development, providing a large range of re-usable
functionality. For example, there are Controls available that can be used to
manipulate image files, connect to the internet or simply provide user interface
components such as buttons and list boxes.
With the APT system, ActiveX Controls are deployed to allow direct control over (and
also reflect the status of) the range of electronic controller units, including the TQD001
Quad Detector. Software applications that use ActiveX Controls are often referred to
as 'client applications'. Based on ActiveX interfacing technology, an ActiveX Control
is a language independent software component. Consequently ActiveX Controls can
be incorporated into a wide range of software development environments for use by
client application developers. Development environments supported include Visual
Basic, Labview, Visual C++, C++ Builder, HPVEE, Matlab, VB.NET, and C#.NET.
Consider the ActiveX Control supplied for a TQD001 APT Quad Detector (one panel
is displayed for each controller).
This Control provides a complete user graphical instrument panel to allow the unit to
be manually operated, as well as a complete set of software functions (often called
methods) to allow all parameters to be set and control operations to be automated by
a client application. The instrument panel reflects the current operating state of the
quad detector unit to which it is associated (e.g. such as beam position and SUM
value). Updates to the panel take place automatically when a user (client) application
is making software calls into the same Control. For example, if a client application
instructs the associated Quad Detector Control to centralize the laser beam within the
quad detector photodiode array, progress is monitored automatically by changing
position on the spot display, without the need for further programming intervention.
The APT ActiveX Controls collection provides a rich set of graphical user panels and
programmable interfaces allowing users and client application developers to interact
seamlessly with the APT hardware. Each of the APT controllers has an associated

11
T-Cube Quad Detector Reader
ActiveX Control and these are described fully in system online help. Note that the
APTUser and APTConfig utilities take advantage of and are built on top of the
powerful functionality provided by the APT ActiveX Server (as shown in Fig. 2.2).
Fig. 2.2 System Architecture Diagram
Refer to the main APT Software online help file, APTServer.hlp (available from the
Windows Start menu), for a complete programmers guide and reference material on
using the APT ActiveX Controls collection. Additional software developer support is
provided by the APT Support pages included on the software installation CD supplied
with every APT controller. This CD contains a complete range of tutorial samples and
coding hints and tips, together with handbooks for all the APT controllers.
2.3.5 Software Upgrades
Thorlabs operate a policy of continuous product development and may issue software
upgrades as necessary.
Detailed instructions on installing upgrades are included on the APT Software
CD ROM.

12
Chapter 3 Initial Installation
3.1 Install The Software
DO NOT CONNECT THE CONTROLLER TO YOUR PC YET
1) Insert the CD into your PC.
2) The CD should run automatically. If your CD does not start, double click the file
‘autorun.exe’, found on the Software CD.
3) A Welcome dialogue screen is displayed. Before installing the software, you are
strongly advised to read the Installation Guide. Click the associated link.
Note
This section is applicable only if the T-Cube is to be used with a PC. If your
application consists only of local operation via the T-Cube front face, proceed
to Section 3.2.
When operating via a PC, direct user interaction with the unit is accomplished
through intuitive graphical user interface panels (GUIs), which expose all key
operating parameters and modes. The user can select multiple panel views
displaying different information about a particular hardware unit. The
multitasking architecture ensures that the graphical control panels always
remain live, showing all current hardware activity.
Caution
Some PCs may have been configured to restrict the users ability to load
software, and on these systems the software may not install/run. If you
are in any doubt about your rights to install/run software, please consult
your system administrator before attempting to install.
If you experience any problems when installing software, contact
Thorlabs on
[phone] and ask for Technical Support.

13
T-Cube Quad Detector Reader
4) Once you are familiar with the installation procedure, click the ‘Install APT
Software’ hyperlink displayed on the Welcome dialogue screen.
5) Follow the on-screen instructions - see the Installation Guide supplied for more
information
3.2 Mechanical Installation
3.2.1 Environmental Conditions
Location Indoor use only
Maximum altitude 2000 m
Temperature range 5oC to 40oC
Maximum Humidity Less than 80% RH (non-condensing) at 31°C
To ensure reliable operation the unit should not be exposed to corrosive agents or
excessive moisture, heat or dust.
If the unit has been stored at a low temperature or in an environment of high humidity,
it must be allowed to reach ambient conditions before being powered up.
3.2.2 Mounting Options
The T-Cube Quad Detector is shipped with a baseplate fitted, ready to be bolted to a
breadboard, optical table or similar surface.
If desired, the baseplate can be removed and the unit can be stood on rubber feet -
see Section 3.2.3.
For multiple cube systems, a USB controller hub (TCH002) is available - see Section
2.2. for further details. Full instructions on the fitting and use of the controller hub are
contained in handbook ha0146 T-Cube Controller Hub, shipped with the product.
Warning
Operation outside the following environmental limits may adversely affect
operator safety.
Caution
When siting the unit, it should be positioned so as not to impede the
operation of the control panel buttons.
Ensure that proper airflow is maintained to the rear of the unit. Do not
cover/obscure the ventilation holes.

14 HA0185T Rev 9 Feb 2014
Chapter 3
3.2.3 Removing the Baseplate
The baseplate must be removed before the rubber feet (supplied) can be fitted, or the
unit is connected to the USB controller hub.
Fig. 3.1 Removing The Baseplate
Using a hexagon key, remove the bolts securing the unit to the baseplate. Retain the
bolts for future use if the baseplate is refitted.
1) Turn the unit upside down.
2) Remove the backing paper from the rubber feet (supplied) taking care not to touch
the exposed adhesive surface.
3) Position the feet as desired, then press and hold for a few seconds until the
adhesive has bonded.
4) The unit may now be used freestanding, sitting on its rubber feet.
Detail A Detail B
Baseplate removed and rubber feet fittedBaseplate attachment screws

15
T-Cube Quad Detector Reader
3.3 Electrical Installation
3.3.1 Description of Input/Output Connections
Fig. 3.2 Rear Panel Connections
DETECTOR IN – used to connect the detector (compatible with Thorlabs PDQ and
PDP series detectors) - see Section A.2. for pin out details.
SUM, LV OUT XDIFF and LV OUT YDIFF (Female SMAconnectors) –Usedtooutput
the signals from the detector to the rest of the system. Typically, the sensor head is a
quad photodiode array that provides top-minus-bottom (Y-Axis alignment) and left-
minus-right (X-Axis alignment) difference signals (-10V to +10V). These two
difference signals are voltage analogs of the light intensity difference sensed by the
pairs of photodiode elements in the array. Additionally, the sensor provides a signal
that is the sum of signals (total beam power) from all four quadrants (0 to 10V).
The signal present on the LV OUT XDIFF and LV OUT YDIFF terminals depends on
the operating mode selected (Monitor, Open Loop or Closed Loop - see Section 4.4.)
The SUM signal from the detector is always present on the rear panel SUM SMA
connector irrespective of the operating mode selected. This signal is proportional to
the total amount of light hitting the detector.
Note
Throughout this document, references to the XDIFF and YDIFF signals follow
the general mathematical convention of drawing graphs, so the positive
values are on the right hand side and upper half of the X-Y plane. However, as
a voltage coming from the sensor (and measured on the rear panel SMA output
connectors in monitor mode), XDIFF is inverted, so the voltage becomes more
negative as the beam is moving from left to right. The equations describing the
detector heads also show this fact
Note
Thorlabs supply a variety of SMA to BNC and SMC to BNC adaptor and
extension cables. Please see our catalog, or visit www.thorlabs.com for
further details.
DETECTOR IN
SUM LV OUT
XDIFF
LV OUT
YDIFF

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Chapter 3
3.3.2 Supply Voltage and Current Requirements
3.3.3 Connecting To A Standalone Power Supply
Fig. 3.3 Front Panel Power Supply Connector
1) Using the front panel connector as shown above, connect the unit to a regulated
DC power supply of the rating detailed in Section 3.3.2.
2) Switch on the Power Supply unit.
3)
Thorlabs offers a compact, two-way power supply unit (TPS002), allowing up to two
Quad Detector or Piezo driver T-Cubes to be powered from a single mains outlet.
However, if an external supply is to be used, see Appendix A.1 for power supply
connector pin out details.
Supply Minimum Maximum Max Operating Current
+5V +4.9V +5.1V 200 mA
+15V +14.5V +15.5V 50 mA
-15V -14.5V -15.5V 50 mA
Warning
The unit must be connected only to a DC supply as detailed in Section
3.3.2. Connection to a supply of a different rating may cause damage to
the unit and could result in injury to the operator.
Caution
Do not connect the T-Cube unit to a 'live' external power supply. Doing so (i.e.
“hot plugging”) carries the risk of PERMANENT damage to the unit. Always
ensure the DC power supply unit is isolated from the mains before connecting
to the T-Cube unit. Always power up the units by connecting their power
supply to the mains. Similarly, to power down the unit, disconnect the power
supply from the mains before disconnecting the T-Cube.
USB POWER
DC +15V, -15V, +5V

17
T-Cube Quad Detector Reader
3.3.4 Using The USB Controller Hub
The TCH002 USB Controller Hub provides power distribution and USB comms for up
to six T-Cubes. It requires only a single power connection and a single USB
connection to the host PC. Further details are contained in handbook ha0146T T-
Cube Controller Hub, supplied with the unit.
Caution
If an external power supply is used, ensure that the 3 supply voltages are
turned on and off simultaneously. Applying the supply voltages with a
large (more than 1 second) time delay between them can result in the
Quad Detector cube showing an incorrect reading.
Warning
DO NOT PLUG A POWERED UP T-CUBE INTO THE TCH002 USB
CONTROLLER HUB. Always ensure that all power is disconnected from
the Controller T-Cubes AND the hub before the T-Cube is plugged into the
hub. Failure to observe this precaution will seriously damage the T-Cube
unit and could result in personal injury.
Caution - T-Cube Hub Signal Routing (Revision 2 units or later).
The T-Cube Hub allows the transfer of voltage signals between T-Cubes
with two available analog lines. This is used by the TPZ001 Piezo Cube
and TSG001 Strain Gauge Cube to route a feedback signal via the Hub for
closed loop operation. It is also used by the TQD001 Quad Detector Cube
to send position demand signals to a pair of slave revision 2 TPZ001
Piezo Cubes (firmware version 2.0.X). The firmware version is displayed
on power up.
A clash can occur if a TSG001 Strain Gauge Cube and a TQD001 Quad
Detector Cube are combined on the hub, and both attempt to drive
voltage signals out via the Hub. In this instance it is recommended that
the TQD001 Quad Detector Cube is configured to drive signals out via its
SMA connections and the associated TPZ001 Piezo Cube pair configured
to pick these signal up via SMA inputs. This will require small SMA to
SMA connection cables (e.g. CA2912), various lengths of which are
available from Thorlabs
Caution
The TCH002 hub cannot be used to communicate between Revision 1
(firmware version 1.0.X) TPZ001 Piezo T-Cube units and the TQD001 Quad
Detector T-Cubes. However, the hub may be used to supply power to
each unit in the system. The firmware version is displayed on the piezo
units, immediately after power up.

18
Chapter 4 Getting Started - Basic Operation
4.1 Introduction
The TQD001 T-Cube Quadrant Detector interfaces with the Detector Sensor Head
and can be used either to measure the position of the beam on the sensor or to
generate a signal that can be used as the feedback input for an automated beam
steering element (e.g. TPZ001 Piezo Driver T-Cube). The signal generated can be
used to steer the beam to the center of the quadrant detector sensor. This active
feedback system is particularly useful in beam stabilization applications.
Throughout this section, the sensor described is a PDQ80A quad detector. However,
the TQD001 unit is also compatible with other Thorlabs detectors, such as the
PDQ30C IR detector head or the PDP90A Lateral Effect Detector.
4.1.1 Overview - Typical System Example
The system comprises a TQD001 Quad Detector T-Cube, a Sensor Head and two
TPZ001 Piezo Drivers, together with the associated piezo-actuated stage, turning
mirror and laser source (see Fig. 4.1). The objective of the system is to position and
hold the laser beam centrally within the detector array.
Fig. 4.1 Typical Stand Alone Set Up
The unit is first set to open loop mode. The turning mirror is adjusted manually to
position the laser beam within the detector array. The Quad Detector unit reads the
signal from the PDQ80A photodiode sensor to indicate the position of the beam on
the target display. When set to closed loop mode, the quadrant reader T-Cube sends
a pair of position demand signals to the piezo drivers, which control the position of the
piezo turning mirror.
HeNe
ASM003
Piezo Mount
KM100
Mirror Mount
POWER
apt
VOLTS
JOG
CONTROL
POWER
apt
VOLTS
JOG
CONTROL
TPZ001
TPZ001
TQD001
PDQ80A PSD Sensor BP150
Beam Splitter
CLOSED LOOP
OPEN LOOP
MODE
POWER
DETECTOR IN
SUM LV OUT
XDIFF
LV OUT
YDIFF
EXT IN
HV OUT
MONITOR
EXT IN
HV OUT
MONITOR
To Piezo Actuators
To Experiment

19
T-Cube Quad Detector Reader
In order for the system to operate correctly in different applications, various software
settings (explained in Section 6.2.) may need to be adjusted. However, the default
settings should allow the Quad Detector to be operated in most cases, straight out of
the box without the need for a PC.
4.2 Detector Head Descriptions
The TQD001 unit is compatible with quadrant detector heads and lateral effect
sensors. Quadrant detectors are used primarily for beam alignment whereas lateral
effect sensors are normally used for position measurement. However, the TQD001
can be used with either type of sensor for both auto-alignment and position
measurement. Both types of sensor output three voltages (XDiff, YDiff and SUM) that
are proportional to the position of the beam and the total optical power, however,
lateral effect sensors like the PDP90A have a defined accurate relationship between
these three voltages. Furthermore, if the user selects the PDP90A sensor type in the
settings panel (see Section 6.2.) the displays shows the XPos and YPos values in
millimeters, whereas if the PDQ80A or PDQ30C sensor type is selected, the display
showstheXDiffand YDiffvalues thatthe sensor outputs in Volts. The TQD001 always
reads the voltages, but additionally for the PDP90A sensor, it is capable of calculating
the exact X, Y position from these voltages.
Caution
The TQD001 must be calibrated before it can be used with the PDP90A as
a position measurement tool, so that the analog voltages are read
accurately. New units are calibrated at the factory before shipment.
Existing units (i.e. those units running embedded code V1.0.3 or earlier)
must be returned to the factory for recalibration. Although upgrading the
embedded code on these earlier units will enable the position
measurement functionality, significant positional error s will occur.
Contact Thorlabs for more details.

20 HA0185T Rev 9 Feb 2014
Chapter 4
4.2.1 PDQ80A and PDQ30C Quadrant Detector Heads
The PDQ80A and PDQ30C are quad photodiode arrays that provide top-minus-
bottom (Y-Axis alignment) and left-minus-right (X-Axis alignment) difference signals.
Additionally, the sensor provides a signal that is the sum of signals (total beam power)
from all four quadrants. The two difference signals are voltage analogs of the light
intensity difference sensed by the pairs of photodiode elements in the array. These
three signals are sent in analog form to the TQD001 Quad Detector via its rear panel
DETECTOR IN (6-pin HRS) connector.
Fig. 4.2 Photodiode Array Details
4.2.2 PDP90A Lateral Effect Sensor
The 2D lateral effect position sensors are sensitive to the position of the beam
independent of the power density or beam shape. The sensing element has four
anode electrodes bonded to the surface (A, B, C & D below).
One cathode electrode is connected to the back surface, which is covered with
resistive material. When radiation is incident upon the sensor, a photocurrent is
generated at that position and it is proportional to the incident light energy. The
photocurrent is proportionally distributed between the four electrodes on the front
surface relative to the position of the light spot on the sensor. A transimpedance
amplifier is used to create measurable voltages. These values are used to calculate
the position using the equations below.
Fig. 4.3 Lateral Effect Sensor
X-axis sensor: (Q2 + Q3) - (Q1 + Q4)
Y-axis sensor: (Q1 + Q2) - (Q3 + Q4)
SUM: (Q1 +Q2 + Q3 + Q4)
Q1Q2
Q3 Q4
(B+C) - (A+D)X Diff =
(A+B) - (C+D)Y Diff =
C
B
D
A
SUM = A+B+C+D