Extraction of surface normal and index of refraction using a pair of passive infrared polarimetric sensors

This paper summarizes a method for extracting 3D information and indices of refraction from a scene by means of a pair of polarimetric passive imaging sensors. Each sensor provides the Stokes vector at each sensor pixel location, from which, degree and angle of linear polarization are computed. Angle of linear polarization provides the azimuth angle of the surface normal vector. Two cases are considered. For the special case when the two sensors have a common azimuth plane the index of refraction can be find analytically in terms of the degrees of polarization and the angle between the lines of sight from the two sensors, from which the depression angle of the surface normal can be computed. For the second and more general case the surface normal is estimated from the cross-product of the azimuth vectors from the two sensors and the inner product of the line of sight vectors and surface normal. Once the de-presion angles are estimated the index of refraction can be computed.