Highresolution 3D Coherent Laser Radar Imaging

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High-resolution 3D Coherent Laser Radar Imaging
Joseph Buck, Andrew Malm, Andrew Zakel, Brian
Krause, and Bruce Tiemann Lockheed Martin
Coherent Technologies Louisville,
Colorado Presented at 14th Conference on
Coherent Laser Radar Technology
Applications Snowmass, Colorado July 8-13,
2007 Presenter Joseph Buck Acknowledgements of
financial support Brent Grime, Air Force
Research Laboratory AFRL/SNJM Bryce Schumm, Air
Force Research Laboratory AFRL/SNJM Contract
F33615-02-C-1106
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Outline

• S3 Overview
• Waveforms and Signal Processing
• Precision Jitter
• Speckle Impacts on Imaging
• Outdoor Imaging Results
• Outdoor Camouflage Tests
• Current Work Future Plans

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Super-resolution Sensor System (S3)
Indoor 3DI Tests

• S3 - AFRL sponsored program
• Seeks to maximize information extracted from
  ladar signals
• Developing true multi-function capability for
  signature retrieval
• Creating adaptable, multi-function waveforms for
  real-time sensor optimization
• Indoor demonstrations presented in 2006

Outdoor 3DI Demo at 0.5 km

• Current status
• Successful laboratory 3D Images
• Outdoor 3DI demos at 0.5km range
• Successful camo penetration demos
• Future Plans
• Implement multi-function operation
• Polarimetric imaging
• Simultaneous vibrometry SAIL
• Demonstrate scalable sensor resolution

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The Phase 1 S3 Team
Pictured Back Row (L to R) Brian Krause, Joe
Buck, John Wenzel, Wayne Garrett, Russ Sibell,
Bruce Tiemann. Front Row (L to R) Andy Zakel,
Rita Kamenz, Andrew Malm Not Pictured Don Jacob,
Duane Smith, Tim Carrig, Lois Grodsky, Phil Gatt,
Paul Cress, Dan Child
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Simplified System Block Diagram- Optical monitor
mitigates amplifier phase errors -

• Open architecture of encoder/decoder allows
  photonics/electronics dividing line to move
  incrementally towards more photonics
• Modular system facilitates upgrades and system
  development
• Optical monitor provides clean transmitted signal
  for applying the matched filter processing

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Imaging Method- Testing of high bandwidth
coherent waveforms for imaging -

• 3D image of 2m x 2m target at a range of 500m
• Flying spot scanner to create raster image of
  target
• 25 mm spot at 500m with lt 0.15mm jitter of spot
  (limited by atmosphere)
• 2 cm range resolution implies gt 7GHz signal
  bandwidth
• Placing scanner before the telescope reduces the
  pointing jitter

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Transmitted Waveforms- Intra-pulse phase
modulation improves range resolution -
Gaussian Amplitude Envelope

• Range Resolution A measure of the ability to
  distinguish two targets closely spaced in range
• Range Precision Error in the measurement of
  range to a single target

10ns Pulse Width
Binary Phase Modulation
83 ps Chip Duration
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Recovered Ladar Signals- Quadrature detection
allows unambiguous phase recovery -
Point Target Quadrature Signals

• Complex signal can be recovered analytically from
  quadrature measurements
• Quadrature detectors can be expanded to allow
  implementation of balanced detection, providing
  improved performance

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Matched Filter Processing- Optical monitor
allows straightforward matched filter processing -

• Maximizes the SNR
• Looks for time delayed versions of one specific
  waveform - ignores everything else
• Correlates the returned signal with an optical
  monitor of the transmitted waveform

B 7 GHz dR 20 mm

• usignal complex modulation of returned signal.
  Computed from returned I and Q signals
• umonitor complex modulation of the optical
  monitor. Computed from monitor I and Q signals
• Integral is numerically computed in software

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Indoor Range Jitter Precision- Indoor range
precision limited by system timing -
Indoor Range Jitter
Indoor Range Precision 0.35 mm

• Range precision tested with a test target at
  near-normal incidence
• Indoor range jitter is limited by the system
  timing jitter and platform stability
• Range precision of 0.35 mm consistent with system
  clock stability and SNR
• Improved system clock is being implemented in
  current system
• Precision can be further improved through signal
  averaging

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Outdoor Range Jitter Precision- Outdoor range
precision consistent with system parameters -
Outdoor Range Jitter
Outdoor Range Precision 1.05 mm

• Range precision tested with a test target at
  near-normal incidence at a range of 0.5 km
• Outdoor range jitter is limited by the system
  timing jitter, platform stability, and
  atmospheric conditions
• Precision can be further improved through signal
  averaging

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Speckle Impacts on Imaging- Speckle impacts
intensity measurements for coherent systems -
Amplitude of Outdoor Return Signal

• Shows impact of speckle on intensity imaging for
  a coherent system
• Timescale of intensity variations vary from 1 to
  7 ms depending on atmospheric conditions
• Averaging signals can mitigate speckle variations

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Indoor 3DI Demo- Intensity range provided by
ladar signals -

• Indoor Results
• 512 x 512 pixels
• Range 2 m
• 22 GHz BW
• 7 mm range res
• 0.1 mm prec
• 300kHz PRF
• Three channels
• No averaging

Movie Click to Play ?
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S3 3DI Field Demo at 0.5km - Simultaneous 3D
intensity image at 0.5 km range -
Conventional Image Imaged from 10m
Grayscale Log(Amplitude) of Matched
Filter Imaged from 0.5km

• 256 x 256 3D image of Jeep at standoff range of
  0.5 km
• 7 GHz signal BW yielded 2 cm range resolution
• Calibration targets demonstrated 1 mm range
  precision

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Outdoor 3DI Demo at 0.5 km- Intensity range
provided by ladar signals -
Target Range Depth 8 m Range Resolution 2
cm Range Precision 1 mm

• Outdoor Results
• 256 x 256 pixels
• Range 0.5 km
• 7 GHz BW
• - 2 cm range res
• 1 mm precision
• 300kHz PRF
• 1 W PAVG
• 8 averages

Movie Click to Play ?
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Camouflage Tests at 0.5 km- Initial tests used a
single layer of propped camo -

• Camouflage provided 50 obscuration
• Tests performed at standoff range of 0.5 km

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Outdoor 3DI Demo at 0.5 km- Intensity range
provided by ladar signals -
Target Range Depth 10 m Range Resolution 2
cm Range Precision 2 mm

• Camo Results
• 256 x 256 pixels
• Range 0.5 km
• 7 GHz BW
• - 2 cm range res
• 1 mm precision
• 300kHz PRF
• 1 W PAVG
• Single Run

Movie Click to Play ? 8 Averages Threshold
Movie Click to Play ? No Averaging
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Current Future Efforts

• Current S3 Effort
• Streamed data collection
• Multi-function operation
• Polarimetric imaging
• Simultaneous vibrometry
• Demonstrate scalable sensor resolution
• Future S3 Effort
• Streamed processing
• Synthetic aperture imaging

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