An improved infrared polarization model considering the volume scattering effect for coating materials

The conventional infrared polarization models ignore the absorption and scattering of infrared light within the coating materials, as well as directional diffuse reflection effect of infrared radiation on the coating surface, which have the limitation for the description of infrared polarization characteristic of coating materials. An improved infrared polarized bidirectional reflectance distribution function (pBRDF) model is proposed based on the microfacet theory, which integrates a volume scattering component developed from the Kubelka-Munk theory, a multiple reflection component and a specular reflection component. This model is more consistent with the infrared polarization characteristics within the actual coating materials. The expression of degree of linear polarization (DoLP) of the infrared radiation is derived. The infrared polarization data of the silver and brown coatings at different measuring angles are acquired by the infrared polarization imaging system, and the model parameters are inverted using the least squares inverse performance method. The simulated and measured results for our coating samples show that the DoLP values simulated by the improved infrared pBRDF model are found in a good agreement with the measurements. The infrared DoLP does not change with the azimuth angle, and mainly influenced by the detection zenith angle, which has a great potential for material classification, polarization remote sensing and infrared scene modeling.