Multiple-Slit Streak Tube Imaging LIDAR (MS-STIL) represents a new method for using streak tubes in a laser radar configuration. The MS-STIL approach uses several slits instead of the usual single slit to provide a number of additional capabilities over the conventional STIL system. Areté Associates has developed several MS-STIL configurations for providing 3-D, single laser pulse, scannerless imaging (Flash mode); 3-D polarimetry; and multispectral 3-D fluorescence imaging.
Flash Ladar
Areté Associates has developed and demonstrated a 3-D Flash ladar sensor. The Flash sensor utilizes fiber-optics to map a 2-D image plane onto a multiple slit streak-tube. The readout from the image of the streak-tube output is electronically unscrambled to produce a 3-D volume image cube in a single laser pulse. The Flash ladar sensor was used in the DARPA Jigsaw program to detect targets under trees. The fundamental concept of Jigsaw is to exploit the randomly placed voids in canopy and/or camouflage to peer through at an unoccluded segment of the target. The ladar system effectively "sees" through these voids unveiling segments of the target. When the sensor platform is moved, a new void distribution is presented to the sensor system that reveals additional segments of the target. Provided a sufficient number of sensor-to-target aspects, the target shape emerges when individual frames are fused into one composite image. This 3-D image is used to form an identification of the target. Areté's Flash sensor has also been used in the AIMSMART program to generate 3-D images of mines in the surf-zone. Areté Associates is investing in new all-solid-state methods to reduce the size, power, and weight of the Flash sensor.
Polarization Imaging Streak Tube LIDAR (PISTL)
Areté Associates has developed an imaging polarimetric ladar system for enhanced detection of landmines and obscuration- camouflaged vehicles. The polarimetric imaging streak tube ladar (PISTL) system operates on a two-measurement Mueller-matrix imaging approach. Two orthogonally- polarized co- registered line-images are formed on the photocathode of a streak tube imaging system that captures range-resolved data for 512 azimuthal (cross-track) pixels with every laser pulse. Push-broom operation of the sensor from an airborne platform generates 3D polarimetric imagery from which targets are discriminated both by shape and depolarization signature. Areté performed airborne field tests that demonstrate target depolarization imagery that enables detection of four different types of surface-laid anti-tank mines. In addition, the PISTL sensor demonstrated detection of military vehicles obscured by foliage, camouflage netting, and smoke from altitudes up to 1000 m above ground level.
Fluorescence Imaging Streak Tube LIDAR (FISTL)
Areté Associates has developed and tested an active 3-D imaging multi-spectral sensor. The sensor utilizes a multi-slit streak-tube coupled to an imaging spectrograph to simultaneously measure the time resolved fluorescence return of multiple spectral channels.
The examples given show 3-D images of a plant with a resolution target in the background. These results demonstrate the effectiveness of 3-D spectral imaging in discriminating between target and background in highly cluttered environments.
Anti-Invasion Mine Signature Measurement and Assessment for Remote Targeting (AIMSMART)
Areté Associates participated in the Anti-Invasion Mine Signature Measurement and Assessment for Remote Targeting (AIMSMART) program sponsored by the Office of Naval Research (ONR). Areté provided instruments and test field support for this effort. Several tests were performed at the Field Research Facility (FRF) at Duck, NC to provide 3-D flash LIDAR and 3-D polarimetric data on sea and land mines scattered throughout the surf and beach zones.
