KEYWORDS: LIDAR, Sensors, 3D image processing, 3D acquisition, Global Positioning System, Semiconductor lasers, Night vision, Defense and security, Nd:YAG lasers, Indium gallium arsenide
The Jigsaw program, sponsored by the Defense Advanced Research Projects Agency (DARPA), will demonstrate a multi-observation concept to identify obscured combat vehicles that cannot be discerned from a single aspect angle. Three-dimensional (3-D) laser radar (ladar) images of a nearly hidden target are collected from several observation points. Image pieces of the target taken from all the data sets are then assembled to obtain a more complete image that will allow identification by a human observer. In this effort a test bed ladar, constructed by the Night Vision and Electronic Sensors Directorate (NVESD), is used to provide three-dimensional (3-D) images in which the voxels have dimensions of the order of centimeters on each side. Ultimately a UAV born Jigsaw sensor will fly by a suspect location while collecting the multiple images. This paper will describe a simulated flight in which 800 images were taken of two targets obscured by foliage. The vehicle mounted laser radar used for the collection was moved in 0.076 meter steps along a 61 meter path. Survey data were collected for the sensor and target locations as well as for several unobscured fiducial markers near the targets, to aid in image reconstruction. As part of a separate DARPA contractual effort, target returns were extracted from individual images and assembled to form a final 3-D view of the vehicles for human identification. These results are reported separately. The laser radar employs a diode pumped, passively Q-switched, Nd:YAG, micro-chip laser. The transmitted 1.06 micron radiation was produced in six micro-joule pulses that occurred at a rate of 3 kHz and had a duration of 1.2 nanoseconds at the output of the detector electronics. An InGaAs avalanche photodiode/amplifier with a bandwidth of 0.5 GHz was used as the receiver and the signal was digitized at a rate of 2 GS/s. Details of the laser radar and sample imagery will be discussed and presented.
An eye safe Ho:YAG laser operating cw at 2.09 micrometers was used as the transmitter for this laser radar (ladar) system. The diode pumped Ho:YAG laser provided up to 100 mW of single frequency output power. An InGaAs detector was selected as the off-set homodyne receiver for vibration signatures. This paper describes the design and characteristics of the laser vibration sensor that is based on laser Doppler radar. Initially, the sensor was calibrated using a piezoelectric loudspeaker, then vibrational signatures were obtained for automobiles having four and eight cylinder engines. This two micron laser Doppler radar permitted high- resolution vibrational signatures detection, remotely, at ranges up to 50 meters.
Graded index coatings of silicon oxynitride have been deposited using ion assisted deposition (IAD). During the IAD process the coated surface is bombarded with low energy reactive ions such that the chemical properties of the coating can be changed in a controlled fashion. We have shown that the chemical composition of SiN(x)O(y) can be varied continuously from silicon nitride to silicon oxide. As a result, the index of refraction of the coatings can be varied between 2.1 and 1.45 by varying the gas mixture in the coating system. The process has been used to deposit graded index antireflection coatings and rugate filters. Several diagnostic techniques were employed to examine the optical, mechanical, and chemical properties of the coatings.
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