Material identification from remote sensing of polarized self-emission

An important application for remote sensing is the detection and discrimination of targets of interest. Polarimetry can be used by remote sensing systems to identify the materials from which targets are made. If an imaging polarimeter is used, the target can also be resolved spatially. A fundamental material property is its complex index of refraction, which can be calculated from polarimetric measurements of the material. Previous work has shown the feasibility of estimating a material’s complex index of refraction from measurements of the polarized reflected radiance in the visible and nearinfrared spectral regions. A new technique is being developed for estimation of the complex index of refraction using measurements of the polarized radiance from a material’s self-emission. Measurements are made in the mid-wave infrared and spectral regions and are used to calculate the Stokes vector, which is then used to calculate the degree of linear polarization (DoLP). An equation is derived for the DoLP as a function of the Fresnel coefficients, which are themselves a function of the complex index of refraction and the angle of emission. Complex index of refraction values calculated from measured material DoLP values are presented. An initial goal of this work is to use the technique to discriminate between metals and dielectrics.