Detection and direct identification of liquid contaminants at standoff distances with an imaging polarimetric spectrometer

We demonstrate a remote sensing method, based on an imaging polarimetric spectrometer, to determine the complex refractive index of materials. The approach represents an adaptation of a technique used in semiconductor ellipsometry. Our experimental demonstration setup comprises a Sagnac-type LWIR spatial interferometer (8 - 12 micron) designed for hyperspectral imaging in emission and reflection. The method facilitates direct measurement of the complex refractive index and the thickness of a layer. Presented work focuses on SF96, a liquid surrogate for toxic chemicals, but the method is generally applicable to solids, including soils, and to any substrate with a general bidirectional reflectance distribution function.