Comparison of retro-reflectance and total integrated scatter as a function of angle of incidence based on reflectometer measurements

A laboratory prototype reflectometer with applications in scene content characterization is available at the Arnold Engineering Development Center (AEDC), Arnold AFB. The SCAT/R measures specular, total, and retro-reflectance at five angles of incidence (AOI) scanning from 2.5 to 15 micrometers . Diffuse reflectance, total integrated scatter (TIS), and thermal emittance are calculated from the measurements. Conventional TIS measurements provide a good measure of a surface finish deviation from specularity, but the scatter distribution is not obtainable from a single measurement. By making TIS measurements over a series of AOI, information on the distribution is obtained. For example, a diffuse surface can be evaluated to determine whether the scattering is characterized by a Lambertian distribution. It has been observed that a series of retro-reflectance measurements at various AOI yields similar angle resolved information. In this paper, the relationship between retro-reflectance and TIS as a function of AOI is investigated for various materials using data from SCAT/R scans. The presentation and analysis of the data follow a brief description of the instrument. The SCAT/R thermal infrared data is useful in identifying/cataloging polarization and hyperspectral characteristics of materials and coatings used for camouflage and for other target and background applications.