Coherent Doppler Lidar Measurement of River Surface Velocity Michael J. Kavaya NASA/LaRC to
Coherent Lidar for 3D- imaging through obscurants Marti… · Coherent Lidar for 3D-imaging through...
Transcript of Coherent Lidar for 3D- imaging through obscurants Marti… · Coherent Lidar for 3D-imaging through...
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Coherent Lidar for 3D-
imaging through obscurants
AUDE MARTIN , JÉRÔME BOURDERIONNET, LUC
LEVIANDER, JOHN F. PARSONS, MARK SILVER, PATRICK FENEYROU THALES RESEARCH AND TECHNOLOGY, PALAISEAU, FRANCE
THALES LTD, 1 LINTHOUSE ROAD, GLASGOW, G51 4BZ, UK
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FMCW coherent LiDAR for 3D-imaging
Main advantages of the system ?
• Directly measure range and velocity
• Versatile waveform defined through
software
• Reduced peak power and large
dynamic
• Insensitive to sunlight glare
• Resistant to jamming and hacking
• Signal processing easily discriminates
hard target from obscurants
P. Feneyrou, et al., Appl. Opt. 56, 9663-9675 (2017) P. Feneyrou, et al., Appl. Opt. 56, 9676-9685 (2017)
Smoke signal
Target
signal
Target
signal
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The FMCW coherent lidar setup
Electronics + fibered optics
+ power management
Optical head
InGaAs camera
Optical scanner
Free-space optics
Gimbal head
▌ Long pulse (few ms) to preserve eye safety
while increasing optical power of the laser amplifier
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Pre-Trial - System check - scene at 70m – 100m – no obscurant
Buildings
and trees
Grass
behind sign Road sign
Measurement on a
windy day… see later
Scanner
field of view Buildings
and trees
Road sign
Grass
LIDAR Range Image
Visible Image
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Pre-Trial - Detail on tilted Road sign
Trial system resolution ~30 cm
Mod. BW ~ 400 MHz
Range Velocity
Speed measurement should
help target recognition
Moving grass and trees (~5 cm/sec)
Stationary sign
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A Selection of Targets from 75m to 1400m at DSTL facilities
~700 m
~75 m
~1400 m
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Clear air images (NO SMOKE)
▌64 x 64 image in approx 90 sec
(acquisition + processing + plots)
Limited by current scan head speed and
processor hardware
Mast at 700m: Image 3.5x3.5m Average power : ~100 mW, 5 ms laser on per pixel
Mast and
attachments
Dirt tracks
Tent walls flapping in the wind (~ 20 cm/sec)
Tent at ~ 1400m: Image: 7 x 7m Average power : ~160 mW & 7 ms int. time
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Range Resolution and discrimination (NO SMOKE)
- 30 cm resolution @ 700m measured during trial
- Limited by current trial system.
1 m
range scale
Resolution
~30 cm
Mast at panel at 700m
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Mannequin (WITH SMOKE)
▌Simultaneous LIDAR acquisition and Visible picture…
▌Image obtained with a smoke transmission down to 0.04 % (double pass)
~4 attenuation lengths (single pass), confirmed with transmission data
Consistent with performance modeling
LIDAR Camera
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Main advantages of photonic integrated LiDAR
Monolithic integration
- Integrated function with both electronic and optical devices on the same chip
- Thermal / mechanical stability
- Active & passive devices integration Today: from optical devices to detectors, tomorrow : from laser to detectors
After : from laser to signal processing ?
Parallel manufacturing
- Cost reduction for mass production
Beam scanning though beam switching / forming
- Fast and reliable scanning with reduced power for driving electronics
Compatibility with fiber technology
- Fiber devices available to cope with (rare) un-mature PIC optical function
- Remote optical head still possible
But… technology not compatible with high peak power and for 𝜆 < 1100 𝑛𝑚
Frequency-modulated continuous-wave coherent LiDAR @ 1.55 𝝁𝒎
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Integrated multichannel FMCW LiDAR
▌8 emission channels
Addressed using cascaded MZ switch
network (SN2)
Each of the emission port covering desired
angle after passing through collimators
Avoid beam scanning
▌8 collection channels corresponding to the emission channels
Addressed using paired MZ switch network
(SN1)
▌8 PBD pairs for signal collection
Connected in // : photocurrents addition
▌Single waveform calibration channel
▌External DFB and circulators
Frequency
shifter
Scanning
system
Balanced
detectors
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Device fabrication and packaging
▌Device fabricated in the Imec ISiPP25G pilot line and packaging by Tyndall Institute
~20 DC connections for switch control
TIA amplifier for RF output -> limited by shot noise
20 optical I/O
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▌ Range up to 50 m with emitted power < 5 mW
▌ Checked switching
Simultaneous range and speed measurement
A. Martin et al., "Photonic integrated circuit based FMCW coherent LiDAR,” in Journal of Lightwave Technology (2018)
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Conclusion
▌Photonic ICs provides key building blocks
for LiDAR applications
Balanced detectors
Frequency shifter
Optical beam steering or switching
▌Demonstration of multichannel on-chip FMCW LiDAR
Speed and range measurement up to 50 m for
5mW emitted power
- Limited by laser linewidth (>100 kHz)
▌Perspectives towards complete monolithic integration
Increased power (longer range): hybrid SiN
platform or optical phased array
Narrow linewidth laser (10 kHz)
▌Field trial of scanning FMCW Lidar
Advantages of FMCW over other 3D
imaging tech.
- Large range dynamic
- Speed measurement
90 s for a 64x64 pixels image for this first
implementation
- Strongly limited by the scanning speed &
data transfer
- Already X3 image rate increase (30 s)
▌ Imaging through obscurants
4 attenuation lengths of smoke
▌Perspectives
Increase scanning and processing speed
- Use a laser with broader modulation
bandwidth and narrow linewidth
- Non Mechanical Beam Steering
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Conclusion
▌Photonic ICs provides key building blocks
for LiDAR applications
Balanced detectors
Frequency shifter
Optical beam steering or switching
▌Demonstration of multichannel on-chip FMCW LiDAR
Speed and range measurement up to 50 m for
5mW emitted power
- Limited by laser linewidth (>100 kHz)
▌Perspectives towards complete monolithic integration
Increased power (longer range): hybrid SiN
platform or optical phased array
Narrow linewidth laser (10 kHz)
▌Field trial of scanning FMCW Lidar
Advantages of FMCW over other 3D
imaging tech.
- Large range dynamic
- Speed measurement
90 s for a 64x64 pixels image for this first
implementation
- Strongly limited by the scanning speed &
data transfer
- Already X3 image rate increase (30 s)
▌ Imaging through obscurants
4 attenuation lengths of smoke
▌Perspectives
Increase scanning and processing speed
- Use a laser with broader modulation
bandwidth and narrow linewidth
- Non Mechanical Beam Steering
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Thank you
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2. Frequency
shifter
3. Scanning
system
Previous demonstrations of 3D imaging on chip
B. Behroozpour, et al., IEEE Journal of Solid-State Circuits, 1, 161-172,(2017)
C. Poulton, et al., Optics Letters, 42 (20), 4091(2017)
R =1.4 m
R = 0.5 m
F. Aflatouni, et al., Optics Express, 4(23), 5117-5125 (2015)
R =0.5 m
1. Balanced
detectors
Optical
Phased Arrays
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Photonic IC functional characterization
▌Switch networks :
Channel isolation > 25dB
<1 dB channel transmission uniformity
9 dB fiber-to-fiber insertion loss (~6 dB coupling, 1 dB for delay line interf., 2 dB switches)
▌PIC power handling
Maximum emitted power without nonlinear absorption in waveguides : 30 mW for 200 mW input
Transmission vs input power for the shunt waveguide:
1 dB compression input power at 22 dBm
▌Detectors
1dB compression point : 8 mA (10 mW optical power)
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▌ Emitted power < 5 mW Pupil diameter : 1 inch
▌ Frequency Bandwidth : 500 MHz/FFT -> resolution = 30 cm
▌ Range finding / Velocimetry > 50 m
Simultaneous measurement of speed and range
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▌Features
Advantages of coherent detection
RADAR Pulsed LiDAR FMCW Lidar
3D-imaging / axial resolution
Simultaneous high resolution Speed and Range
Versatile resolution and range ambiguity
Jamming/Hacking immunity
Sun insensitivity
Degraded vision environment proof (clouds, dust, fog)
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Device power handling
▌Specific input grating coupler/splitter (U. Ghent)
Fiber to chip coupling losses = 3.2 dB
▌Linear transmission up to almost 1 Watt of input power
T. Spuesens, et al., " Integrated Grating Coupler/Power Splitter for On-chip Optical Power Distribution," Group IV
Photonics Conference, Paris, 2014
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Balanced photodetection
▌Requirements for shot-noise limited measurement :
Photodiodes :
- Handle enough optical power to ensure
shot noise > thermal noise
Balanced scheme :
Reject RIN below shot noise at high input power
CMRR>50dB achieved
1 dB compression point at 11dBm
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ll rig
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23 OPEN JPAL 2018 – 30/05/18
Thales Research & Technology France
Calibration of the waveform
▌Shorter delay line -> larger error on the waveform optimisation
-> demodulation error
Delay line : 𝜏 = 1 𝑛𝑠 Delay line : 𝜏 = 24 𝑛𝑠
This
do
cu
me
nt
ma
y n
ot
be
re
pro
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d, m
od
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ad
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o a
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Tha
les
- ©
Th
ale
s 2
01
8 A
ll rig
hts
re
serv
ed
.
24 OPEN JPAL 2018 – 30/05/18
Thales Research & Technology France
Temps de traitement
≈ 10 Hz
Data
presentation
Data Transfer
25
ms
25
ms
50
ms
Signal processing
Peak
Detection : 75 %
≈ 250 Hz
Data Transfer
5 m
s
< 1
ms
Signal processing
Before Now*
* Figure dilatée…