ISSN Online: 2379-1748
ISBN Flash Drive: 978-1-56700-483-0
ISBN Online: 978-1-56700-482-3
4th Thermal and Fluids Engineering Conference
DESIGN AND DEMONSTRATION OF AN AUTOMATED BIDIRECTIONAL REFLECTOMETER FOR LOW-REFLECTIVITY OPTICAL COATINGS
While diffuse emission and diffuse-specular reflection are often adequate models in the conceptual design stage of radiation-dominated systems, more accurate bidirectional spectral models may be required for performance evaluation. Described is an effort leading to empirical models for the bidirectional reflectance distribution function (BRDF) of highly specular, low-reflectivity black coatings typical of those frequently used in aerospace and remote sensing applications. An automated goniometer-based reflectometer has been designed, assembled, and used to obtain the needed measurements at both polarizations. The measurement problem is exacerbated by the fact that the BRDF of such materials varies several orders of magnitude over the range of incidence angles of interest. The BRDF is also influenced by coating thickness and wavelength as well as by the method used to apply the coating. The current contribution describes preparation of the samples and the design and use of the reflectometer. New data are presented for the Z302 BRDF for both the p- and s-polarizations at 305 nm.