Polarization characterization for target surfaces

Polarization characteristics of reflection and near-specular scattering by target surfaces at oblique incidence are evaluated by polarimetry in both infrared and visible wavelengths. Different materials with surfaces varying from smooth to very rough are investigated. Ellipsometry is used to measure the linear and circular polarizations for smooth to slightly rough surfaces. Polarized reflectance is measured for slightly rough to very rough surfaces. For specular reflection, dielectric surfaces show high linear polarization, and small circular polarization. Metal surfaces show high circular polarization, whereas small linear polarization and dielectric films show large linear and circular polarization. Near-specular scattering for a black anodized aluminum sample also shows polarization characteristics similar to those for specular reflection. Effective medium theory is used to model polarization for specular reflection, which shows agreement with the measured polarization for rough surfaces. Beckmann's scattering theory for random rough surfaces is used to model the near-specular scattering, which also shows agreement with the measured polarized reflectance. These data and the developed computation programs can be used to model polarization for targets of known geometric shapes.