Mohan Vaidyanathan, Steven Blask, Thomas Higgins, William Clifton, Daniel Davidsohn, Ryan Carson, Van Reynolds, Joanne Pfannenstiel, Richard Cannata, Richard Marino, John Drover, Robert Hatch, David Schue, Robert Freehart, Greg Rowe, James Mooney, Carl Hart, Byron Stanley, Joseph McLaughlin, Eui-In Lee, Jack Berenholtz, Brian Aull, John Zayhowski, Alex Vasile, Prem Ramaswami, Kevin Ingersoll, Thomas Amoruso, Imran Khan, William Davis, Richard Heinrichs
KEYWORDS: Sensors, LIDAR, 3D image processing, 3D acquisition, Target detection, Imaging systems, Image processing, Control systems, Image sensors, Data processing
Jigsaw three-dimensional (3D) imaging laser radar is a compact, light-weight system for imaging
highly obscured targets through dense foliage semi-autonomously from an unmanned aircraft. The
Jigsaw system uses a gimbaled sensor operating in a spot light mode to laser illuminate a cued
target, and autonomously capture and produce the 3D image of hidden targets under trees at high 3D
voxel resolution. With our MIT Lincoln Laboratory team members, the sensor system has been
integrated into a geo-referenced 12-inch gimbal, and used in airborne data collections from a UH-1
manned helicopter, which served as a surrogate platform for the purpose of data collection and
system validation. In this paper, we discuss the results from the ground integration and testing of the
system, and the results from UH-1 flight data collections. We also discuss the performance results
of the system obtained using ladar calibration targets.
A prototype image processing system has recently been developed which generates, displays and analyzes threedimensional ladar data in real time. It is based upon a suite of novel algorithms that transform raw ladar data into cleaned 3D images. These algorithms perform noise reduction, ground plane identification, detector response deconvolution and illumination pattern renormalization. The system also discriminates static from dynamic objects in a scene. In order to achieve real-time throughput, we have parallelized these algorithms on a Linux cluster. We demonstrate that multiprocessor software plus Blade hardware result in a compact, real-time imagery generation adjunct to an operating ladar. Finally, we discuss several directions for future work, including automatic recognition of moving people, real-time reconnaissance from mobile platforms, and fusion of ladar plus video imagery. Such enhancements of our prototype imaging system can lead to multiple military and civilian applications of national importance.
Richard Marino, W. Davis, G. Rich, J. McLaughlin, E. Lee, B. Stanley, J. Burnside, G. Rowe, R. Hatch, T. Square, L. Skelly, M. O'Brien, A. Vasile, R. Heinrichs
Situation awareness and accurate Target Identification (TID) are critical requirements for successful battle management. Ground vehicles can be detected, tracked, and in some cases imaged using airborne or space-borne microwave radar. Obscurants such as camouflage net and/or tree canopy foliage can degrade the performance of such radars. Foliage can be penetrated with long wavelength microwave radar, but generally at the expense of imaging resolution. The goals of the DARPA Jigsaw program include the development and demonstration of high-resolution 3-D imaging laser radar (ladar) ensor technology and systems that can be used from airborne platforms to image and identify military ground vehicles that may be hiding under camouflage or foliage such as tree canopy. With DARPA support, MIT Lincoln Laboratory has developed a rugged and compact 3-D imaging ladar system that has successfully demonstrated the feasibility and utility of this application. The sensor system has been integrated into a UH-1 helicopter for winter and summer flight campaigns. The sensor operates day or night and produces high-resolution 3-D spatial images using short laser pulses and a focal plane array of Geiger-mode avalanche photo-diode (APD) detectors with independent digital time-of-flight counting circuits at each pixel. The sensor technology includes Lincoln Laboratory developments of the microchip laser and novel focal plane arrays. The microchip laser is a passively Q-switched solid-state frequency-doubled Nd:YAG laser transmitting short laser pulses (300 ps FWHM) at 16 kilohertz pulse rate and at 532 nm wavelength. The single photon detection efficiency has been measured to be > 20 % using these 32x32 Silicon Geiger-mode APDs at room temperature. The APD saturates while providing a gain of typically > 106. The pulse out of the detector is used to stop a 500 MHz digital clock register integrated within the focal-plane array at each pixel. Using the detector in this binary response mode simplifies the signal processing by eliminating the need for analog-to-digital converters and non-linearity corrections. With appropriate optics, the 32x32 array of digital time values represents a 3-D spatial image frame of the scene. Successive image frames illuminated with the multi-kilohertz pulse repetition rate laser are accumulated into range histograms to provide 3-D volume and intensity information. In this article, we describe the Jigsaw program goals, our demonstration sensor system, the data collection campaigns, and show examples of 3-D imaging with foliage and camouflage penetration. Other applications for this 3-D imaging direct-detection ladar technology include robotic vision, avigation of autonomous vehicles, manufacturing quality control, industrial security, and topography.
Brian Aull, Andrew Loomis, Douglas Young, Alvin Stern, Bradley Felton, Peter Daniels, Debbie Landers, Larry Retherford, Dennis Rathman, Richard Heinrichs, Richard Marino, Daniel Fouche, Marius Albota, Robert Hatch, Gregory Rowe, David Kocher, James Mooney, Michael O'Brien, Brian Player, Berton Willard, Zong-Long Liau, John Zayhowski
Lincoln Laboratory has developed 32 x 32-pixel ladar focal planes comprising silicon geiger-mode avalanche photodiodes and high-speed all-digital CMOS timing circuitry in each pixel. In Geiger mode operation, the APD can detect as little as a single photon, producing a digital CMOS-compatible voltage pulse. This pulse is used to stop a high-speed counter in the pixel circuit, thus digitizing the time of arrival of the optical pulse. This "photon-to-digital conversion" simultaneously achieves single-photon sensitivity and 0.5-ns timing. We discuss the development of these focal planes and present imagery from ladar systems that use them.
Richard Marino, Timothy Stephens, Robert Hatch, Joseph McLaughlin, James Mooney, Michael O'Brien, Gregory Rowe, Joseph Adams, Luke Skelly, Robert Knowlton, Stephen Forman, W. Davis
MIT Lincoln Laboratory continues the development of novel high-resolution 3D imaging laser radar technology and sensor systems. The sensor system described in detail here uses a passively Q-switched solid-state frequency-doubled Nd:YAG laser to transmit short laser pulses (~ 700 ps FWHM) at 532 nm wavelength and derive the range
to target surface element by measuring the time-of-flight for each pixel. The single photoelectron detection efficiency has been measured to be > 20 % using these Silicon Geiger-mode APDs at room temperature. The pulse out of the detector is used to stop a > 500 MHz digital clock integrated within the focal-plane array. With
appropriate optics, the 32x32 array of digital time values represents a 3D spatial image frame of the scene. Successive image frames from the multi-kilohertz pulse repetition rate laser pulses are accumulated into range histograms to provide 3D volume and intensity information.
In this paper, we report on a prototype sensor system, which has recently been developed using new 32x32
arrays of Geiger-mode APDs with 0.35 μm CMOS digital timing circuits at each pixel. Here we describe the
sensor system development and present recent measurements of laboratory test data and field imagery.
We have constructed a target-board platform to provide adaptive-optics and tracking performance characterization for the Airborne Laser Advanced Concepts Testbed program. The target board comprises 1536 discrete sensors distributed over a 1-meter by 2.5-meter array mounted to the side of a specially modified Cessna Caravan aircraft. The aircraft platform includes multiple beacon sources for adaptive- optics and tracking, a large-capacity data-recording system and a real-time telemetry ground-link for data display. In this paper we provide an overview of the target-board platform. We discuss the results of requirements analysis for target-board detector configuration, and describe the detailed design and capabilities of the various sub-systems.
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