AOTF Based Imaging Sensor for Enhanced Stand-off Chemical Detection

In this proposal, Physical Sciences Inc. (PSI) outlines the development of an acoustic-optic tunable filter (AOTF) for imaging spectroscopy in the 8 to 11 micron thermal infrared spectral region. In this region, where strong emission from field stops andvignetting can significantly increase the background radiance, a careful design of the system is needed in order to maintain good spectral and spatial resolution. The approach proposed by PSI to optimize the system performance will include the restrictionof the detector full field of view to force all rays through the crystal and provide spectral resolution, as well as building and designing proper field stop for reduction of radiation from out-of-band wavelengths. The design couples the AOTF instrumentto a cryogenically cooled HgCdTe infrared detector with high responsivity and low noise performance. The technical objective is to demonstrate that the AOTF instrument is a feasible chemical and biological imaging sensor in the thermal infrared regionable of achieving a spectral resolution of 8 to 10 cm^-1, an NESR of 2 to 5 ¿W cm-2 sr^-1 um^-1 and a data cube rate of one data cube for every 2 to 3 seconds. The resulting imaging system will be capable of detecting changes in the infrared signature ofa scene, where biological and chemical agents have unique spectral features. The system would be inexpensive and precise, with an agile response time only limited by the acoustic transit time across the optical aperture. It will also be capable of highspectral throughput while having a large dynamic range.