Quantifying key trade-off between IR polarimetric discriminability versus pixel resolution against complex targets

摘要

The augmentation of passive IR conventional and hyperspectral imaging sensors with polarimetric capability offers enhanced discrimination of man-made and geophysical targets, along with inference of surface shape and orientation. In our efforts to size the design of IR polarimetric hyperspectral imagers to various remote discrimination applications, we have ascertained critical relationships between polarimetric SNR and pixel sizing. This relationship pertains primarily to realms wherein the objects to be sensed will be marginally resolved spatially. The determination of such application- specific relationships is key to the design of effective polarimetric sensors. To quantify this key trade-off relationship, we have employed the latest developmental version of SPIRITS, a detailed physics-based signature code which accounts for the various geometric, environmental illumination, and propagation effects. For complex target shapes, detailed accounting for such effects is especially crucial to accurate prediction of polarimetric signatures, and thus precludes hand calculation for all but simple uniformly planar objects. Key to accurate polarimetric attribute prediction is our augmentation of the Sandford-Robertson BRDF model to a Mueller/Stokes formalism that encompasses representation of fully general elliptically polarized reflections and linearly polarized thermal emissions in strict compliance with Kirchoff's Law. We discuss details of the polarimetric augmentation of the BRDF and present polarimetric discriminability-resolution trade-off results for various viewing aspects against a ground vehicle viewed from overhead.