AOTF Based Spectro-Polarimetric Imaging System For Stand Off Chemical Detection

We propose an Acousto-Optic Tunable Filter (AOTF) Spectropolarimetric Imaging System for Enhanced Standoff Chemical Detection at Long Wave Infrared (LWIR) wavelengths. This work entails development of suitable LWIR material, design of the LWIR AOTF, and design of the hyperspectral imaging sensor using a focal plane array. Currently, there is no technologically mature, commercially available material at reasonable price for AOTF imaging in the LWIR wavelength range. We have been actively researching suitable materials for LWIR AOTF imaging systems for some time, and we also develop AOTF products commercially. We propose using mercurous halide crystals to fabricate the AOTF. The AOTF component has no moving parts, making it a rugged and reliable device, and it provides polarimetric imaging capabilities. Polarization analysis adds a valuable signature feature to imaging data, allowing a wide variety of targets to be detected with greatly enhanced contrast. The proposed hyperspectral polarimetric imaging system will have discrimination capabilities comparable to existing hyperspectral imaging chemical/biological sensors. The sensor will be able to passively detect small chemical plumes (25 meters or smaller) of a chemical agent such as sarin at relevant concentrations (less than 10 ppmv) at a distance of 5 kilometers or more under ambient conditions.