A scatterometer for measuring the polarized bidirectional reflectance distribution function of painted surfaces in the infrared

A new three-axis automated scatterometer has been developed to measure the polarized scattering properties of painted surfaces. A configuration which is more convenient for far-field measurement is presented. The emitting parts of the new devices are mounted on a rotating stage, and the receiving part is fixed in the lab stationary platform. It can measure the polarized bidirectional reflectance distribution function throughout almost all of the hemisphere surrounding the sample. The coordinate transformation required for the scatterometer is described in detail. The dual-rotating retarders method is used to modulate polarizing and analyzing optics. Discrete Fourier transform (DFT) method is used to retrieve the Mueller matrix of the sample. A new hybrid model based on micro-facet theory is presented to validate the in-plane data, and the comparison between the experimental data and model calculation are given. The results of in-plane and out-plane polarized bidirectional reflectance distribution function for samples coated with different paints are presented.