Acousto-optic tunable filters for infrared imaging

摘要

Sensing from space requires the development of hyperspectral imagers operating in the two atmospheric window regions (3-5 μm and 8-12 μm) in the infrared region. At the Army Research Laboratory we are developing hyperspectral imagers operating in these two regions based on using acousto-optic tunable filters (AOTFs). Research is going on in the growth of new acousto-optic materials—mercurous halides (Hg_2Cl_2 and Hg_2Br_2) and tellurium (Te) for development of AOTF cells. We have developed a hyperspectral imager using a tellurium dioxide (TeO_2) AOTF with a liquid-nitrogen-cooled indium antimonide (InSb) 256x256 focal plane array (FPA) that covers 2-4.5 μm region and another imager using a thallium arsenic selenide (TAS) AOTF with liquid-nitrogen-cooled mercury cadmium telluride (HgCdTe) 256x256 FPA to cover 7.8-9.8 μm region. Each of these imagers has been integrated on a tripod-mountable platform with an appropriate optical train. Control of RF electronics, and image acquisition and storage operations are carried out under full computer-control with a user-friendly interface. We will discuss the progress in material development and present imaging results.