Voxtel Opto ROX APD Photoreceiver Series User manual

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USER MANUAL
PHOTORECEIVERS, LASERS,
LASER RANGEFINDERS, LRF MODULES,
AND LRF SYSTEM-INTEGRATOR KITS
Voxtel Literature LRF User Manual 26April2019_ed06Dec2019©. Voxtel makes no warranty or
representation regarding its products’ specific application suitability and may make changes to
the products described without notice.
Voxtel Inc. 15985 SW Schendel Avenue, Beaverton, OR 97006, USA
www.voxtel-inc.com

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CONTENTS
Safety.............................................................................................................................................................................3
Safety Symbols ..........................................................................................................................................................3
Handling Precautions ................................................................................................................................................4
Introduction...................................................................................................................................................................6
Cautions, Warnings, and Notes .................................................................................................................................6
Organization ..............................................................................................................................................................6
Resources .................................................................................................................................................................. 6
ROX APD Photoreceiver Products..................................................................................................................................7
Precautions................................................................................................................................................................ 7
Setup and Operation .................................................................................................................................................8
Adjusting the Voltage Threshold level..................................................................................................................9
Configuring Time-variable Threshold (TVT) ..........................................................................................................9
Changing the Decay Time on the Voltage Threshold............................................................................................9
Calibrating for Range Walk ...................................................................................................................................9
Troubleshooting ......................................................................................................................................................10
ROX APD Photoreceiver Evaluation Board ..............................................................................................................10
Initial Configuration ............................................................................................................................................11
Operation............................................................................................................................................................12
Configuring Time-variable Threshold (TVT).........................................................................................................12
DPSS Lasers and Laser Driver Boards...........................................................................................................................14
Precautions.............................................................................................................................................................. 14
Assembly, Configuration, and Operation ................................................................................................................15
Use of non-Voxtel laser driver boards.....................................................................................................................18
Disassembly/Storage ...............................................................................................................................................19
Troubleshooting ......................................................................................................................................................19
LRF System-Integrator Kit ............................................................................................................................................20
Precautions.............................................................................................................................................................. 20
Assembly and Configuration ...................................................................................................................................21
LRF OEM Module .........................................................................................................................................................25
Precautions.............................................................................................................................................................. 25
Assembly, Configuration, and Operation ................................................................................................................26
LRF Systems Operation................................................................................................................................................30
Precautions.............................................................................................................................................................. 30
Connectivity.............................................................................................................................................................30
Direct Cabled Connection to LRF system board .................................................................................................31
ISM Connection to LRF System Board.................................................................................................................31
Communication .......................................................................................................................................................31
Receiver Gain Configuration....................................................................................................................................33
Position LRF System.................................................................................................................................................34
Receiver Threshold Configuration...........................................................................................................................34
Ranging Commands.................................................................................................................................................35
Operational Examples .............................................................................................................................................37
Single-pulse Range Operation.............................................................................................................................37
Multi-Pulse Range Operation..............................................................................................................................39
Auxiliary Board ........................................................................................................................................................39

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Updating Module Software and Firmware..............................................................................................................40
Installing the LRF Commander Software ............................................................................................................40
Loading the Device Firmware .............................................................................................................................43
Appendix A—Unpacking, Inspection, and Cleaning.....................................................................................................45
Unpacking................................................................................................................................................................ 45
Inspection and Cleaning ..........................................................................................................................................46
Inspection ...........................................................................................................................................................46
Window Cleaning Techniques.............................................................................................................................46
Appendix B—LRF Detection Threshold........................................................................................................................48
Appendix C—Auxiliary Board.......................................................................................................................................49
Setup, Configuration, and Calibration.....................................................................................................................50
Mounting and Enclosure.....................................................................................................................................51
Sensor Initialization and De-initialization ...........................................................................................................51
Sensor Configuration ..........................................................................................................................................51
System Operation....................................................................................................................................................54

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SAFETY
Before unpacking the product, read and learn all safety and handling information provided in this section. Whenever
unpacking, handling, operating, moving, or storing the product, ensure all guidelines in this section are met.
References
•EN/IEC 60825-1 Ed.2 2007
•Laser Notice No. 50, dated June 24, 2007
SAFETY SYMBOLS
When handling a Voxtel laser product, the labels and hazard descriptions below apply. Due to size limitations, labels
do not appear on the product.
With the exception of the ESD warning label, the following labels are provided for application by the assembler or
end user of the product. Proper product labeling of the fully assembled product is required in order to meet FDA
certification guidelines. Proper labeling provides the user with appropriate warnings and product information when
applied in the following manner.
•Labels provided must be permanently fixed, legible, and visible according to their purpose.
•Labels provided must be read without the necessity for human exposure to laser energy in excess of the limits
associated with Class 1.
Further explanation can be found in IEC 60825-1 Ed.2, sec 5.1
Explanatory Label
This product is a Class 1 laser product as defined by EN/IEC
60825-1 2007.
Non-Interlocked Protective Housing Label
The eyesafe, microminiature DPSS laser contains a Class 4 laser
diode. There are no user-serviceable parts on any of the items
supplied. Do not attempt to open the laser to attempt
maintenance, service, repair or reconfiguration of any kind.
Certification Label
This laser complies with U.S. FDA performance standards for
laser products except for deviations pursuant to Laser Notice
No. 50, dated June 24, 2007.
Manufacturer’s Identification Label
Manufacturer, address, product and serial number.

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ESD Warning Label
Handling this product requires ESD precautions.
HANDLING PRECAUTIONS
This section applies to all Voxtel LRF products.
For all units
equipped with a laser:
I
n addition to the requirements below, adhere to the
requirements of:
•
“DPSS Lasers and Laser Driver Boards” section of this
manual
•
Safe use of laser protocols using ANSI Z136.1-2014
•
ESD prevention protocols using
ANSI-ESD-S20.20-2014 as a guide
For units
not equipped with a laser:
In addition to
the requirements below, adhere to the
requirements of:
•
ESD prevention protocols using
ANSI-ESD-S20.20-2014 as a guide
⚠Warning
•For all units equipped with a laser, failure to follow laser protocols and precautions when handling the product
may result in personal injury and/or damage to the product.
⚠Caution
•Failure to follow ESD protocols and precautions when handling the product may result in damage to the product.
A single electrostatic discharge (ESD) event can cause catastrophic or latent device failure.
ESD Precautions
For all units that have a standalone laser:
•When Not in Use: Electrically short the laser anode and cathode electrical leads to prevent ESD damage.
oFor lasers with connectors attached, insert the shorting pin in the connector.
oFor lasers without connectors, twist the exposed conductive wires together.
•When Making the Connections: 1) do not connect the laser to a function generator, or other pulse
generator, with the pulse generator emitting pulses; 2) connect 5V to the laser diode driver before
attaching laser wires. Disconnecting and reconnecting the 5V with the laser wires attached to the anode
and cathode may damage the laser.
For all units (including those equipped with a laser):
•Clean, Static-free Environment: Do not open the package in an unclean environment; handle the product
only in a clean, static-free work environment, such as a grounded workbench or surface.
•Continuous Grounding: Ensure all persons and tools that may contact the product are continuously
grounded.
•ESD-protective Clothing/Accessories: When handling the product, wear: 1) a grounded wrist strap; 2) ESD
protection; and 3) ESD-safe (static-dissipative) lint-free (nonshedding) gloves. If any oil or grease is
apparent on the gloves, replace the gloves.

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•ESD-protective Container:When transporting the product beyond the confines of the workbench, place it
in an ESD-protective container that restricts product movement within the container, such as the original
shipping container, an antistatic bag, or a grounded cart.
•Powered-off for Connections: When making connections, ensure the product power supply is off. Do not
connect a product to a laser diode when the power supply voltage is on.
Additional Handling Protocols and Precautions
For all units (including those equipped with a laser):
•When placing or positioning the product, use a light touch.
•Except as described in “Appendix A—Unpacking, Inspection, and Cleaning,” do not allow anything to
contact the transmit window of a laser or the receive window of a photoreceiver.
•Handle the product using thumb and forefinger as shown:
For lasers, hold the top of the laser casing—
above the mounting flanges.
⚠
Caution
•Do not bend the laser mounting flanges.
The mounting f
langes are designed as
flexures to reduce torque effects
during
mounting. If not handled correctly, the
mounting flanges may become bent.
For photoreceivers, receivers are best handled by
holding with thumb and forefinger across the
diameter of the TO-8 can.
⚠
Caution
•Do not allow pins to bend
Take care when mounting, handling,
or placing
the product. If pins need to be straightened
,
use a standard pin-straightening tool.
•During handling, wear clean lint-free gloves to avoid contaminating the window.
⚠Note
•Do not touch the product with bare hands.
Any oil or grease that contacts the window can negatively impact performance; oil or grease that
contacts the product casing can negatively affect cosmetic appearance.
Additional Notes
⚠Note
•Voxtel is not responsible for the setup and operation of non-Voxtel supplied equipment.
⚠Note
•The product may look different than shown. Refer to the drawings on the datasheet.

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INTRODUCTION
This user manual provides the information necessary to operate the ROXTM laser ranging photoreceivers, pulsed
diode-pumped solid-state (DPSS) lasers, electronics, and rangefinding or lidar products.
CAUTIONS, WARNINGS, AND NOTES
In this handbook, the following conventions are used:
⚠Warning
•Failure to follow this guidance may result in injury.
⚠Caution
•Failure to follow this guidance may result in damage to the equipment.
⚠Note
•Failure to follow this guidance may result in sub-optimal performance of equipment.
ORGANIZATION
This manual is generally organized by product. For devices that integrate multiple products as components—such as
the laser rangefinding (LRF) modules, which integrate ROX APD photoreceivers, DPSS lasers, and electronics—
information is available about the integrated product and additional information is available by component. For
example, while an integrated LRF module has its own section, specific information about the laser is provided in the
laser section and specific information about the photoreceiver is provided in the photoreceiver section of this
manual.
Information that is universal to all LRF products is provided in the following sections of this user manual:
•Safety
•Appendix A—Unpacking, Inspection, and Cleaning
For all products, before unpacking the product from the shipping package, ensure all safety and handling conditions
are met.
RESOURCES
•Product Datasheets
oIndividual product datasheets are available via the relevant product links from http://voxtel-
inc.com/products/.
oAsingle-file compilation of all LRF product datasheets is available at http://voxtel-
inc.com/files/LRF-Product-Catalog.pdf.
•Mechanical drawings and solid models are available at http://voxtel-inc.com/voxtel-news/user-resources/.
•Latest LRF firmware and software are available at http://voxtel-inc.com/voxtel-news/user-resources/.
•Voxtel Technical Notes on Laser Rangefinding—These technical notes are to help users understand how to
model, configure, integrate, and operate the laser-ranging products for specific applications. The technical notes
are available via the Technical Papers link on the Resources page at Voxtel-Inc.com.
•Voxtel’s Software Interface Control Document for Laser Rangefinder Modules, Kits, and Components (software
ICD) is available at http://voxtel-inc.com/files/LRF-Software-ICD.pdf.
•This user manual is available at http://voxtel-inc.com/files/LRF-User-Manual.pdf.

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ROX APD PHOTORECEIVER PRODUCTS
References
•ROXTM APD Photoreceiver Product Datasheet—Contains required operational information for connecting and
using the ROX APD photoreceivers, as well as information on the ROX APD Photoreceiver Evaluation Board.
•Voxtel Technical Notes on Laser Rangefinding—These technical notes are to help users understand how to
model, configure, integrate, and operate the laser-ranging products for specific applications. The technical notes
are available via the Technical Papers link on the Resources page at Voxtel-Inc.com.
PRECAUTIONS
APD photoreceivers are sensitive to damage by ESD or other voltage transients. ESD-mitigating procedures are
required when handling the photoreceivers. Before handling the equipment, read and become familiar with the
safety and handling information below and in the “Safety” section of this manual.
⚠Caution
•Failure to follow ESD procedures when handling the photoreceiver may result in damage to or destruction of the
photoreceiver.
•Do not connect the photoreceiver with the power-supply voltage powered on.
•Do not direct or focus laser light directly on the ROX APD photoreceiver.
APD photoreceivers are sensitive to being damaged by large optical signals. For optical damage threshold limits,
refer to the product datasheet.
•Do not direct high-pulse-energy lasers or high-average-power pulsed lasers directly onto the APD photoreceiver.
For testing, a sufficient signal level can be achieved by pointing the laser source at a very diffuse source, so that
only a diffuse reflection of the laser light reaches the photoreceiver. Alternatively, neutral density filters can be
placed in front of the laser and photoreceiver to attenuate the optical signals at the photoreceiver.
⚠Note
•Voxtel is not responsible for the setup and operation of non-Voxtel supplied equipment.

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SETUP AND OPERATION
1. Read and adhere to the safety and handling protocols described at the start of this product section and in the
“Safety” section of this manual.
⚠Warning
•Failure to follow the precautions and procedures in the “Safety” section of this manual may result in
catastrophic damage to the system.
2. Unpack, inspect, and (if necessary) clean the product as described in “Appendix A—Unpacking, Inspection, and
Cleaning.”
3. Consult the photoreceiver datasheet for electrical and optical interfacing to the photoreceiver.
4. Configure a printed circuit board to provide the electrical input and output signals shown on the datasheet.
5. APD photoreceivers are factory-configured to default on power up to Mode 1, which sets the APD to operate
with a gain of M= 1. For a description of the photoreceiver operating modes, refer to the ROX APD
Photoreceiver Product Datasheet.
6. Before integrating the photoreceiver in the circuit, verify that the electrical interfaces meet the specifications
of the datasheet.
7. If the photoreceiver analog output is being used, verify that the termination of the output is 50 ohms.
8. Configure the controller to send start commands to the photoreceiver with the pulse-width encoding shown
on the datasheet.
9. Adjust the voltage threshold (Vth) to 0.55V.
10. Power-off the circuit and insert the photoreceiver.
11. Darken the operating environment or place a shroud or other covering over the photoreceiver, so that
ambient lighting will not increase the noise floor.
12. Power-on the circuit, monitoring the power lines.
13. Ensure the current draw of the supplies are within the expected values on the datasheet.
⚠Note
•The APD photoreceiver output will not respond to DC light sources.
14. Send a START command for Mode 1 (M= 1) operation.
15. Continue to send START commands at regular time intervals (e.g., every few seconds) so that the APD bias is
adjusted to accommodate temperature changes. Do not allow the temperature of the APD photoreceiver to
lower more than a few degrees Celsius.
⚠Caution
•Failure to monitor temperature and re-bias the APD by sending START commands can damage the product.
If the temperature of the photoreceiver is changed by more than a few degrees Celsius, the change in the APD
gain characteristics can cause the APD to go into sustained avalanche breakdown, resulting in permanent
damage to the photoreceiver.
16. Test the photoreceiver to check if it is operational using one of the following methods:
•While operating without a pulsed light source, adjust the Vth bias down until false hits begin to be returned from
the digital outputs. This will occur between 0.4V and 0.5V; or
•Monitor the analog output and confirm there is a signal at the output when the laser source is firing.
17. Power off the laser source and reduce Vth in small steps from 0.6V until desired false-alarm rate (FAR) is
reached.
18. If using the optional evaluation board, setup and configure as described in “ROX APD Photoreceiver Evaluation
Board,” later in this section.

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ADJUSTING THE VOLTAGE THRESHOLD LEVEL
Proper management of the detector voltage threshold level is critical for optimal operation of the photoreceiver.
The threshold settings, during the ranging event, set: the voltage level in the detector that determines the probability
of detecting the return laser pulses; and the false-alarm rate (FAR) of the photoreceiver. Generally, low voltage
threshold settings allow for a high probability of pulse detection with a higher FAR, and high voltage threshold
settings allow for a lower probability of pulse detection, with a lower FAR.
To optimize the voltage threshold for various applications, refer to Voxtel’s Technical Notes on laser rangefinding.
CONFIGURING TIME-VARIABLE THRESHOLD (TVT)
While synchronizing to the outgoing laser pulse, reduce Vth from a voltage bias level of Vth_high to a voltage bias level
of Vth_low. An RC circuit in the APD photoreceiver will drop the threshold with the decay time specified in the
datasheet. The RC decay time is also user-configurable.
In the standard configuration, the photoreceiver includes an RC time delay circuit that allows the user to change the
threshold level while ranging. This allows the photoreceiver detection probability to change as a function of range,
so that probability of detection of a target is somewhat normalized as a function of range.
A time-variable threshold (TVT) can be achieved by changing the Vth level from a high voltage level to a low voltage
level. The threshold begins to lower immediately once the Vth level is switched from the end system. This is typically
done when the T0 pulse is detected.
The photoreceiver is designed to allow for TVT, which allows for the detection threshold to change over a decay
time. The specific decay-time constant at which the detection threshold lowers as a function of time is included in
the photoreceiver datasheet. RC delay circuits tailored to user-specific requirements can be accommodated (contact
Voxtel for details).
To cause a TVT, set Vth to the highest threshold voltage level (Vth_high) optimal for detecting the near-field optical
pulse returns. Vth_high is generally set to between 0.65V and 0.70V.
•Vth high should be set so that the outgoing pulse can be detected.
•Vth low should be set to the desired false alarm rate of the end system.
When Vth is switched from high to low the voltage threshold is dropped to a lower voltage, Vth_low.
Vth_lowdetermines pulse-detection probability and false-alarm probability at the end of the TVT decay time, which
means it must be set specifically for the application requirements. The low voltage threshold, Vth_lowis generally
between 0.45V and 0.6V.
CHANGING THE DECAY TIME ON THE VOLTAGE THRESHOLD
The time constant changes the threshold as follows:
Vth (τ) = Vth_high - (Vth_high – Vth_low)·e-τ⁄R·C
When the external value of Vth is changed from one value to another—e.g., from a high voltage level, Vth_high, to a
low voltage level, Vth_low—as configured at the factory, the internal threshold Vth(τ) changes according to the RC time
constant. The RC value can be found on the datasheet. It may be possible to modify the RC time constant by adding
a resistor to the circuit, outside of the TO-8 package. For details, contact Voxtel.
CALIBRATING FOR RANGE WALK
Range walk is the systematic dependence of the range accuracy on the return pulse amplitude. The effects of range
walk can be mitigated in the photoreceiver by approximating the pulse amplitude by recording the leading-edge and
falling-edge threshold crossings of the return laser pulse. The difference between the times of the falling edge and

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the rising edge is called the time over threshold and is used to estimate the pulse amplitude so that a range-walk-
correction factor may be applied.
A description of range walk is provided in the datasheet and methods of calibrating for range walk are described in
Voxtel Technical Notes on laser rangefinding.
TROUBLESHOOTING
No analog output:
•Ensure the optical source is pulsed, with a pulse width between approximately 0.1 ns and 100 ns. The
photoreceiver will not respond to DC (non-modulated) optical sources.
•Make sure the analog output has a 50-ohm termination.
•Using an oscilloscope or voltage meter, verify that the input bias levels at the APD photoreceiver are as specified
in the datasheet. In particular, monitor VAPD, VCMOS1, and VCMOS2 to confirm they are at the proper bias
levels.
•Measured VAPD bias levels that are lower than expected indicate that:
oThe APD is being operated at signal levels above the specified dynamic range; or
oThe photoreceiver has short circuited or is otherwise damaged.
•Verify that there is not too much optical signal.
•After performing the above, power down the photoreceiver and contact Voxtel for further troubleshooting tips.
Noise on the digital output lines:
•Verify that the digital output lines are properly terminated.
•Adjust Vth up to about 1 V to verify that the photoreceiver is not triggering off the electronic noise.
The calculated range changes with the reflectivity of the target:
•Changes in range accuracy are generally due to range walk. A description of range walk is included in the
datasheet and in Voxtel's Technical Notes on laser rangefinding.The system must be calibrated to accommodate
the amplitude-dependent detection timing offsets that will result in the desired range accuracy errors.
The calculated range changes with the voltage threshold:
•Changes in range accuracy are generally due to range walk. A description of range walk is included in the
datasheet and in Voxtel's Technical Notes on laser rangefinding.The system must be calibrated to accommodate
the amplitude-dependent detection timing offsets that will result in the desired range-accuracy errors.
•Changes in range precision are generally caused by signal pulse amplitudes that are close in value to the voltage
threshold levels. At low signal levels, jitter caused by electronic noise may result in range-precision errors, as
evidenced by a large standard deviation in the timing measurements. A description of how to optimize the signal-
to-threshold levels is included in Voxtel's Technical Notes on laser rangefinding.
ROX APD PHOTORECEIVER EVALUATION BOARD
The ROX APD Photoreceiver Evaluation Board is an option (sold separately) that allows operation and rapid
evaluation of the ROX APD photoreceivers. The evaluation board provides the control and signal conditioning
necessary to operate the APD photoreceiver and to evaluate the various operating modes of the photoreceiver. The
evaluation board is delivered with an AC-to-DC power adaptor that provides the power necessary to operate the
photoreceiver and is shipped with hardware to allow it to be mounted on an optical table for evaluation. The
photoreceiver operating modes can be chosen using a simple dual-in-line plug (DIP) connector. The threshold voltage

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setting is adjusted with a potentiometer. The evaluation board also accommodates time-variable threshold
operation.
INITIAL CONFIGURATION
⚠Caution
•Do not aim the laser directly at the photoreceiver.
Aiming lasers directly at the receiver may result in a power density exceeding the photoreceiver damage threshold.
For the purposes of testing, use neutral density filters in front of the APD and photoreceiver and reflect the laser
off of diffusely scattering targets—preferably at ranges of 50 meters or longer. Do not test the photoreceiver using
lasers aimed at highly reflective or retro-reflectors.
⚠Caution
•To avoid damage to the APD, return the evaluation board to Mode 1 (M= 1) when repositioning the laser or
when the photoreceiver is not in active use.
1. Read and adhere to the safety and handling protocols described at the start of this product section and in the
“Safety” section of this manual.
⚠Caution
•Failure to follow the precautions and procedures at the start of this section and in the “Safety” section of
this manual may result in catastrophic damage to the system.
2. Unpack, inspect, and (if necessary) clean the product as described in “Appendix A—Unpacking, Inspection, and
Cleaning.”
3. Mount the evaluation board within an optical test apparatus.
4. Ensure the jumper on J7 is removed or is otherwise not connecting any of the three pins together. The jumper on
J7 is used only to enable time-variable threshold (TVT) functions. For details of the jumper configuration, refer
to “Triggering TVT with Optical Signal (T0 pulse detected by photoreceiver) .”
5. Using a 50-Ω coaxial cable, connect the analog output to an oscilloscope channel configured for DC-coupled
50-Ω termination.
⚠Note
•Failure to use a 50-Ω termination will cause the output buffer amplifier to oscillate.
6. Set the oscilloscope channel to 100 mV per division.
7. Using a second 50-Ω coaxial cable, connect the comparator output to a second channel of the oscilloscope,
also configured for DC-coupled 50-Ω termination. Set the oscilloscope channel to 1V per division.

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8. Plug the provided 5V power supply into the evaluation board.
9. Set the high threshold voltage level, Vth_high, as follows:
a. When no optical signal is present, turn the R35 potentiometer counterclockwise until the digital channel
reacts to electrical noise, which indicates the signal path is functioning.
b. After verifying that the output is reacting to the electronic noise, turn the Vth_high potentiometer back
(about a half-turn clockwise), so that any digital output due to noise is rare. The threshold voltage level
for the desired false-alarm rate (FAR) for Vth_high can be set precisely using a digital counter.
10. Set the low threshold voltage level, Vth_low, as follows:
a. Press and hold the SW5 switch (located adjacent to the potentiometers).
b. Monitoring the digital output, turn the R20 potentiometer counterclockwise until the desired output FAR
is achieved. The FAR can be measured using a digital counter.
The ROX APD Photoreceiver Evaluation Board is now configured for operation and is optical-signal ready.
OPERATION
For descriptions of the operating modes used in the various ROX APD Photoreceiver models, refer to the datasheet.
When power is applied to the evaluation board, it automatically configures the photoreceiver to operate in mode 1,
which, for most standard factory configurations, sets the APD gain to M= 1.
Each of the four micro-pushbutton switches enables one of the four factory-calibrated photoreceiver operating
modes (SW1 = mode 1; SW2 = mode 2; SW3 = mode 4; and SW4 = mode 3). The switches can be used to optimize
photoreceiver performance for a particular application.
Each time an SW switch is pressed, the following sequence occurs:
1. The high-voltage supply is enabled.
2. A measurement of the temperature of the photoreceiver is performed.
3. The APD in the ROX APD photoreceiver is configured to the bias voltage that was factory calibrated. These
calibrated operating voltages are stored in memory in the ROX APD photoreceiver.
While, a significant change in temperature is unlikely in lab-test scenarios, it is generally advisable to regularly set
the APD gain by periodically re-affirming the photoreceiver operating mode. This can be achieved, for example, by
pressing the SW switch prior to making a sequence of measurements, so that the APD bias is adjusted for the current
ambient temperature. This achieves optimized performance and reduces the risk of damage due to breakdown
avalanche currents.
When temperature changes are likely—e.g., during field testing—either manually set the various modes frequently, or
automatically set the various modes using a temperature sensor and a controller.
The optical signal that results from an outgoing laser pulse—often referred to as a T0 pulse—provides a precise
reference for the beginning of a laser range sequence.
CONFIGURING TIME-VARIABLE THRESHOLD (TVT)
To adjust the high threshold voltage level (Vth_high) and the low threshold voltage level (Vth_low), adjust the
potentiometers as described in “Initial Configuration,” earlier in this section.
Disable Time-variable Threshold (TVT)
To disable time-variable-threshold operation, remove the J7 jumper.
Operating Time-variable Threshold (TVT)
To enable time-variable threshold (TVT), place a jumper between any two adjacent pins on the J7 connector so that
they are electrically connected. When configured in this way, the threshold voltage of the pulse-detection
comparator is set to Vth_high; during operation after the TVT circuit is triggered, the threshold voltage Vth drops from
Vth_high to Vth_low in a decay time specified in the datasheet.

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The threshold voltage remains at the low setting for ~20 ms before automatically resetting to high. Note that this
reset time limits the pulse-repetition-rate capabilities of the evaluation board to 50 Hz.
Selecting T0 Trigger Source (Electrical or Optical)
The J7 jumper setting determines if the TVT circuit has been triggered by an optical T0 pulse incident on the detector,
or by an externally supplied 5V logic signal. If the jumper is removed, the TVT function is disabled.
•Triggering TVT with Optical Signal (T0 pulse detected by photoreceiver)
The TVT will be initiated by the outgoing laser pulse (T0 pulse) when it is detected by the photoreceiver, if Pin 2
and Pin 3 of Jumper J7 are electrically shorted together. In this configuration, after the photoreceiver detects
the laser pulse, the detection threshold voltage bias will lower from Vth_high to Vth_low over the factory-configured
decay time.
•Triggering TVT with Electrical Logic Signal (T0 pulse generated by external electronics)
To start the TVT using the rising edge of an external provided electrical trigger, place a jumper to electrically
short Pin 1 and Pin 2 of J7. The trigger logic signal should be applied to the SMA connector labeled J6. The rising
edge of the user-supplied T0 trigger signal will cause the voltage threshold level to decay from Vth_high to Vth_low
over a factory-configured decay time.

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DPSS LASERS AND LASER DRIVER BOARDS
PRECAUTIONS
Laser products described in this manual are Class 1. Before handling the equipment, read and become familiar with
the safety and handling information below and in the “Safety” section of this manual. DPSS lasers are very sensitive
to damage by electrostatic discharge (ESD) or other voltage transients. When storing, handling, or operating the
laser, ensure all requirements are met.
⚠Warning
•Use of controls or adjustments or performance of procedures other than those specified herein may result in
hazardous radiation exposure.
Voxtel’s DPSS lasers are designated as a Class 1 laser product when used as described for all procedures and
operations in the information accompanying the product.
•Do not attempt to open the laser for maintenance, service, repair, or reconfiguration of any kind.
There are no user-serviceable parts. Users are not authorized to perform any maintenance—scheduled or
otherwise—on any items supplied. Service, repair, or reconfiguration is only to be carried out by Voxtel-trained
technicians and engineers.
•Do not operate if there is any mechanical damage to the base or cover, or if the cover is removed.
The DPSS lasers contain a Class 4 laser diode.
•Do not attempt to view laser output directly with any external viewing aid such as magnifying lens or microscope.
Any focusing of the beam directly into the eye may cause damage or blindness.
⚠Caution
•Do not operate with a laser trigger pulse longer than 3.5 ms.
The laser trigger pulse provides current to the pump laser diode while the signal is high. A laser trigger pulse with a
duration longer than 3.5 ms can overdrive the laser and result in damage.
•Do not operate with a frequency above the maximum specified frequency.
Each laser has a specified maximum pulse-repetition rate (refer to the product datasheet); exceeding it can
overdrive the laser and cause damage.
⚠Note
•Voxtel is not responsible for the setup and operation of non-Voxtel supplied equipment.

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References
•Voxtel’s DPSS Lasers and Laser Driver Boards datasheet contains electrical and mechanical interface information
for Voxtel’s DPSS lasers and laser driver boards, as well as assembly options (such as collimating optics and
integrated T0 detector).
•Mechanical drawings, solid models, and this user manual are available at voxtel-inc.com via the “Drawings, Solid
Models, Software, Firmware, and Document” link on the Resources page.
•IEC 60825-1 Ed.2—Contains definition of laser classification
•ANSI Z136.1—Safe Use of Lasers
ASSEMBLY, CONFIGURATION, AND OPERATION
This section describes the setup and operation of Voxtel DPSS lasers used with a Voxtel-supplied laser driver board.
Equipment
Laser setup requires the following basic equipment:
•Laser driver board for use with the specific laser product (e.g., 100 µJ, 300 µJ, 750 µJ, etc. variant)
•User-provided mount for the laser driver board (for mounting hole size and spacing, refer to Voxtel’s mechanical
drawings of the laser driver board)
•5V power supply: 1.5A, center positive standard barrel plug
•Pulse generator with BNC cable: Laser trigger output—square pulse, max 2.5 V, min 0 V, max 10 Hz, pulse width
max 3.5 ms
•Custom tri-furcated cable
•Mechanical mounting surface for orienting the laser (for mounting hole size and spacing, refer to Voxtel’s
mechanical drawings of the laser base)
Procedure
1. Read and adhere to the safety and handling protocols described at the start of this product section and in the
“Safety” section of this manual.
⚠Warning
•Failure to follow the precautions and procedures at the start of this section and in the “Safety” section of
this manual may result in personal injury and/or catastrophic damage to the system.
Unpack, inspect, and (if necessary) clean the product as described in “Appendix A—Unpacking, Inspection, and
Cleaning.”
Shipping Box for Laser only (ESD-Protective Container)
Voxtel DPSS lasers are shipped in an ESD-protective box.
The ~7 x 3½ x 1-in3(18 x 9 x 25-mm3) box shown will
contain up to four lasers. Each Voxtel DPSS laser includes:
•a cathode (black wire)
•an anode (red wire)
•(optional) an integrated T0 detector (white
wire; 26 – 28 AWG)
•a laser certificate of compliance

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Voxtel DPSS Lasers
All Voxtel DPSS lasers include a cathode (black wire) and an anode (red wire), as pictured below.
Voxtel DPSS Lasers with Optional T0 Detector
Some Voxtel DPSS lasers, such as pictured below, are configured with an optional T0 detector. The T0 detector
may be used to detect the outgoing laser pulse.
The T0 detector consists of an InGaAs PIN diode integrated onto a printed circuit board, with passive filtering
circuitry. The PIN diode is mounted directly over the laser cavity.
All lasers with the integrated T0 detector option have a coaxial cable and the laser lid has a mini-coaxial
connector (T0 signal cable) and a white wire (26 – 28 AWG) connected as a 3rd pin to the laser connector (T0
bias). The white wire is used to bias (i.e., 5 VDC) the T0 detector located inside the laser. The output from the
T0 detector is at the coaxial connector and is designed to be terminated to 50 Ω.
Assembly and operation of lasers with the T0 detector is otherwise identical to those without.
2. Ensure the pulse generator is set correctly to the voltage levels specified to trigger the laser and that the
output (laser trigger) is off.
⚠Note
•Laser wires may be soldered after mechanical mounting of laser and laser driver board.
If desired, this step can be performed after performing the mechanical mounting of the laser and laser-
driver board.

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3. Solder the anode and the cathode to the laser-driver board. Solder the red and black wires to the board as
shown below.
⚠Note
•Instead of soldering the wires directly into the board, a user-provided terminal block may be used.
A two-position terminal block that can be easily soldered into the anode and cathode holes on the board is
recommended. A suitable part is TE Connectivity P/N 796911-2.
⚠Note
•A laser and laser-driver board with custom connectors may be used.
Contact Voxtel for this custom option.
⚠Note
•For temporary use, the laser-driver board may be mounted using one mounting hole.
4. Mount the laser to a custom fixture and torque the screws to 1.0 in-lbs. (M2 x 3 mm or 2–56 x 1/8”).
The recommended laser mounting is via two screws through the mounting flanges onto a flat surface using the
recommended torque. Voxtel cannot guarantee laser performance will meet criteria if mounted otherwise.
5. Mount the laser driver board through the corner mounting hole(s) to a post to prevent shorting.
6. Connect the 2 x 5 IDC connector (J1) of the custom tri-furcated cable to the J4 connector of the laser driver
board.
7. Connect the 5V supply to the 5V input receptacle (J2) of the custom tri-furcated cable.
Connect the 5V to the laser diode driver before connecting the laser to the laser diode driver.
8. Connect the pulse generator output BNC cable to the BNC connector (J3) of the custom tri-furcated cable.
⚠Caution
•Do not allow the pulse-repetition frequency to exceed the specification.
The laser has been designed for a maximum pulse-repetition frequency, which is specified on the
datasheet. Exceeding the specification can overdrive the laser and result in damage.

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9. For models with an external integrated T0 detector (for all other models, skip this step):
a. Connect the laser to the laser driver board using the 3-pin harness (already attached to the laser driver board).
b. Connect one end of the coaxial cable with the coaxial connector to the T0 signal connector on the laser lid.
c. If the laser is for use with the Voxtel System-Integrator Kit:
i. Connect the other end of the coaxial cable to the J3 connector on the LRF system board.
ii. Follow the additional “Assembly and Configuration” instructions provided in the “LRF System-Integrator Kit”
section of this manual.
10. Configure the pulse generator to provide a laser trigger as follows:
a. Set the duration of the laser trigger as follows:
i. If the laser certificate of compliance is available: Set the duration of the laser trigger to exceed the laser
delay time by 0.05 ms. The laser delay time can be found in the laser certificate of compliance.
ii. If the laser certificate of compliance is unavailable: Set the duration of the laser trigger to 1.00 ms.
b. Set the pulse repetition frequency of the laser trigger to 2 Hz.
11. Place the laser-pulse detection card about 4 inches from the exit window.
12. Enable the pulse generator output.
13. Verify the laser pulse can be observed on the laser-pulse detection card.
⚠Caution
•Do not allow the laser trigger signal pulse width to exceed 3.5 ms.
If the laser trigger signal pulse width is too long, permanent damage will occur to the laser.
14. If the laser pulse is not observed:
a. Increase the duration of the laser trigger pulse time in increments of 0.01 ms until the laser is observed
firing, then increase the laser-on time once more by 0.05 ms.
b. If the laser-on time reaches 3.0 ms and the laser pulse is not observed, contact Voxtel.
15. Ensure the laser trigger (pulse generator output) is off before disconnecting laser from laser driver board.
USE OF NON-VOXTEL LASER DRIVER BOARDS
⚠Note
•Voxtel is not responsible for the setup and operation of non-Voxtel-supplied equipment.
When using a user-supplied laser driver board to drive a Voxtel laser, ensure the driver board output meets the
specification given in the “Electrical” section of the laser datasheet.

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DISASSEMBLY/STORAGE
⚠Caution
•The laser trigger (pulse generator output) must be off before disconnecting the laser from the laser driver board.
1. Ensure the laser trigger (pulse generator output) is off.
2. Connect the anode and cathode contacts of the laser (this is an ESD precaution): For soldered connections,
unsolder the wires and twist the wires together as shown. If unsoldering is not feasible, proceed to the next
step.
3. Store the product in an ESD protective container (e.g., a nickel bag). The Voxtel shipping container may be
used as an ESD protective container for storage.
TROUBLESHOOTING
Symptom Troubleshooting Actions
No light 1. Verify the 5V DC supply using a digital multimeter (DMM).
2. Verify the laser anode and cathode are connected to the laser driver board.
3. Verify the polarity of the anode and cathode connections.
4. Verify the laser trigger signal with an oscilloscope.
5. Verify the laser trigger signal is at the TTL level.
6. Verify the laser trigger signal duration is between 1.00 ms and 3.0 ms.
7. Verify the laser trigger signal repetition rate does not exceed 2 Hz.
Note: 2 Hz should be used for troubleshooting purposes.
8. Place the pulse detection card directly in front of the laser—about 4 inches
from the exit window.
9. If the problem persists, contact Voxtel.
Dim light, large
area on laser-pulse
detection card
1. Verify that both mounting screws are torqued correctly to 1.0 in.-lb.
2. Verify the laser trigger pulse width by starting at a 1.00-ms duration and
increasing to no more than 3.0 ms in 0.1-ms increments.
3. Loosen both mounting screws so there is zero torque on both and recheck for
lasing as described above.
4. If no lasing is observed after trying the above steps:
a. Carefully note the following:
oTorque used to mount the laser screws
oLaser trigger pulse-repetition rate
oTemperature of operation
oReflective or other surfaces located in front of the laser
oPotential ESD events
b. Contact Voxtel with a message that includes the notes listed above.