SensL's presentation from the IWPC conference on LIDAR for automotive safety and advanced driver assistance systems.

1. Laser Range Finding and
Imaging LIDAR with Silicon
Photomultipliers
Dr. Carl Jackson – CTO and founder
IWPC - Advanced Radar, Camera, and Laser
Sensors for Automated Driving Workshop
March 21st, 2013
SensL - Laser Range Finding and Imaging LIDAR with
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2. SensL Quick Facts
Boston Ireland
Business Low Light Sensors
Beijing
Markets Medical Imaging
Hazard & Threat Detection
LIDAR & Automotive
Biophotonics
Model Fabless Semiconductor
SensL - Laser Range Finding and Imaging LIDAR with
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Silicon Photomultipliers

3. SensL Sensor Products for Automotive LIDAR
MicroFM-xxxxx-X18
• Sensor size: 0.25mm and 1mm
• Industry standard TO18 package
MicroFM-xxxxx-X05
• Sensor size: 3mm and 6mm
• Industry standard TO5 package
MicroFM-xxxxx-X39
• Sensor size: 1mm and 3mm
• Industry standard TO5 package with integrated TEC
MicroFM-xxxxx-SMT
• Sensor size: 0.25mm, 1mm, 3mm and 6mm
• Custom reflow solderable clear molded, surface
mount package
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4. LIDAR Requirements and the SensL Advantage
 LIDAR Requirements  SensL Benefits to Automotive
– Wide detection range – Dynamic range
– High range accuracy – Ambient light rejection
– Temperature stability – Temperature stability
– Miniaturized
– Rugged  Benefits of SiPM Technology
– Low power – High signal to noise
– Multi-sensor capability – High uniformity
– Low cost – Multi-sensor capable
– Low power
– Low cost
SiPM sensors are a superior alternative
to the APD and PIN Photodiode
SensL - Laser Range Finding and Imaging LIDAR with
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Silicon Photomultipliers

5. SensL SiPM for Automotive LIDAR
 What is an SiPM?
– Array of Geiger-mode photon sensors
optimized for gain and high speed
 Advantages of SiPM over PIN or APD
– Gain of SiPM is >1M
– Output response is picoseconds
– Temperature stability
– Uniformity of output response
– Wide dynamic range
– Large area array compatible SiPM Architecture
– CMOS compatible
 Advantages of SensL SiPM for Automotive
– Patented Fast Output terminal provides the
fastest output response of any silicon
sensor
– Picosecond response times provides the
highest range accuracy possible
Circuit Designator
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Silicon Photomultipliers

6. Sensor Technology Comparison
PIN APD PMT SiPM
Gain 1 102 106 106
Operating Voltage 0V to 5V 100V to 1kV 800V to 1kV 30 V
Temperature Sensitivity Low High Low Low
Mechanical Robustness High High Low High
Damage by Stray Light No Yes Yes No
Spectral range UV-VIS-NIR UV-VIS-NIR Blue/UV UV-VIS-NIR
Readout Electronics Complexity Complex Complex Simple Simple
Form Factor Small Small Bulky Small
System Cost Medium Medium High Lowest
Scalable Technology Yes No No Yes
Electromagnetic Immunity No No No Yes
Sensor Noise Low Med Low Lowest
Response time Fast Slow Fast Fastest
SiPM provides highest performance
and lowest system cost
SensL - Laser Range Finding and Imaging LIDAR with
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Silicon Photomultipliers

7. Why is Dynamic Range Important for the
Automotive Industry?
 Reflected light intensity varies by orders of dynamic range
 SensL SiPM provides wide dynamic range accuracy
 Benefits of a wide dynamic range sensor
– Ability to sense high photon flux signals
– Ability to sense low photon flux signals
LIDAR Output Pulse
LIDAR Return Pulse
LIDAR Output Pulse
LIDAR Return Pulse
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Silicon Photomultipliers

8. Why is Ambient Light Rejection Important for
the Automotive Industry?
 Automotive LIDAR systems must deal with reflected ambient light
from the environment
– Sunlight
– Environmental lighting
 Ambient light can be rejected through system design
– Reduction in field of view
– Filters
– Sensor with better ambient light rejection
 Benefits of ambient light rejection at the Sensor
– Improved range accuracy
– Wider dynamic range
– Reduced system cost
SensL - Laser Range Finding and Imaging LIDAR with
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Silicon Photomultipliers

9. Ambient Light Rejection Example
Light Pulse Ambient Noise
• This is an example of
a low photon LIDAR
APD signal pulse in a high
ambient background
• Amplifier noise
excluded
• SiPM provides
superior background
suppression
SensL SiPM
SensL - Laser Range Finding and Imaging LIDAR with
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Silicon Photomultipliers

10. Why is Temperature Stability Important for the
Automotive Industry?
 Temperature stability is required to maximise range accuracy over
the operating temperature range
 Benefits of a temperature insensitive sensor
– Minimal need to adjust bias voltage with temperature
– No need for a variable gain amplifier
– Reduction in calibration requirements
– Increased system stability over operating lifetime
– Ability to have multi-sensor or arrays for Imaging LIDAR
APD SiPM
Operating Voltage Variation 50V 0.5V
Temperature Stability 0.65V/˚C 0.02V/˚C
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11. Temperature Stability of SensL SiPM
• APD gain varies non-linearly
with voltage
• APD is highly temperature
sensitive
• SiPM gain varies linearly with
voltage
• SiPM is insensitive to
temperature variation
Gain vs. Voltage APD
Gain vs. Voltage SiPM Temperature Sensitivity
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Silicon Photomultipliers

12. Case Studies
Two case studies showing the SensL SiPM in LIDAR
applications
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13. Industrial Application of LIDAR
 Time of flight for industrial
measurement applications
 Key system advantages
– Wide dynamic range
– Ambient light suppression
– Speed of detector response
– Uniformity MicroFM-xxxx-X18
– Temperature stability
– Low cost
Impulse response function of SensL
MicroFM-02520-X18
• 68.7ps onset time
• 155ps total response time (FWHM)
Plot courtesy of Photek Ltd. (UK)
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14. Advanced Imaging LIDAR
LIDAR ranging and Imaging System for MARS Lander
256x1 linear array with a dual ASIC packaged
with TEC controller and interface board.
Image taken using SensL’s detector
head for ESA Imaging LIDAR program
Detector head and interface electronics provides high resolution LIDAR ranging and imaging.
20Km accurate to +/- 1.5m for ranging 5Km accurate to +/- 1.5cm for imaging
• Coarse ranging clock = 100MHz. High resolution required over < 5Km
• Return Time = Count x 10 x 10-9 High resolution uses interpolators for sub 10ns resolution
Distance = 0.5 x Return Time x 3 x 108 Interpolator accuracy is +/-50ps
• Distance = 1.5 x Count Metres Imaging accuracy = 3 x 108 x 50 x 10-12 = +/- 1.5cm
• Accuracy is +/- 0.75 metres
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15. LIDAR Reference
Design with SensL
SiPM
Reference design comparing SensL SiPM to a
standard APD based LIDAR electronics design
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16. SiPM LIDAR Reference Design Advantageous
APD Reference Design • SiPM does not need trans-
impedance amplifier
• RF voltage amplification
matched to 50Ω without
reduction in bandwidth
-100V to -400V • Advantages:
• Overall higher performance
(SNR, range accuracy)
• Lower cost
SPM Reference Design • Higher bandwidth
30V ADC or • Array compatible
comparator • Insensitive to microphonics
SPM
0V
*Reference: Texas Instruments LiDAR system design tech note
Literature Number: SNAA123
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17. Thank You
For more information please visit us on the web at:
www.sensl.com/automotive
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