Acousto-optic tunable filter based visible- to near-infrared spectropolarimetric imager

A compact, lightweight, robust, and field-portable spectropo- larimetric imager is developed to acquire spectropolarimetric images both in the laboratory and outdoors. This imager uses a tellurium dioxide (TeO2) acousto-optic tunable filter (AOTF) as an agile spectral selection element and a nematic liquid-crystal variable retardation (LCVR) plate as a tunable polarization selection device with an off-the-shelf charge- coupled device (CCD) camera and optics. The spectral range of opera- tion is from 400 to 800 nm with a 10-nm spectral resolution at 600 nm. Each spectral image is acquired with two retardation values correspond- ing to the horizontal and vertical incident polarizations. The operation of the imager and image acquisition is computer controlled. We describe the instrument and its operation and present results of our measure- ments.