A Modified pBRDF Model Considering the Influence of Relative Azimuth Angle for Coating Targets

The key to the researches on the polarization characteristics of targets lies in the precise establishment of the polarization model—the polarized bidirectional reflectance distribution function (pBRDF). Currently, the researches on the pBRDF model for coating targets have the problem of inaccurately describing hemispherical distribution of the degree of linear polarization (DoLP), especially the insufficiency in describing the influence of the azimuth angle on DoLP. In this thesis, firstly, with the aim of minimizing the error in linear polarization degree, through simulation comparative experiments on common microfacet distribution function (NDF), geometric attenuation factor (GAF) and multiple reflection function, it is determined that the Gaussian NDF, the modified integral GAF and the Minnaert model considering roughness are more suitable for coating targets. Secondly, the combined model for coating targets was established by combining the three functions, and it is found that the combined model was insensitive to the azimuth angle. Finally, a pBRDF model incorporating a high-order polynomial of relative azimuth angle is proposed, which improved the problem of excessive error caused by the insensitivity to the azimuth angle. The results of experiments show that the relative errors when adopting the modified model have decreased by 45.8%, 66.7%, 10.5%, and 32.1% respectively. The determination coefficient has reached 0.948, 0.953, 0.917 and 0.930, and the performance indicators are superior to those of the existing models. The research results provide a reference for describing the hemispherical spatial distribution of DoLP for coating targets.