Active and passive SWIR imaging polarimetry

Abstract

Efforts to understand the potential for polarization information to improve our target acquisition capability have been extended from the mid and long wave IR regions into the short wave IR. A passive, complete rotating- retarder Stokes imaging polarimeter has been developed, calibrated, and field tested. A review of the calibration and some example phenomenology will be presented, including temporal variation of target polarization signatures. Spectral investigation of targets and backgrounds in the SWIR band have been promising. For daytime use, passive polarization imaging could provide additional information for improved detection or identification. The passive polarization imaging effort in the SWIR forms one half of an active polarization agile 1.54 micrometers imaging system. In this system, the polarization of radiation from an eye-safe 1.54 micrometers laser is controlled so that a target or background can be illuminated with a known polarization. Analysis of the reflected beam allows calculation of the Mueller Matrices will hopefully lead to better target-to-background discrimination. This Active Mueller Imaging Ellipsometer has been calibrated, and initial imagery of targets has been collected.