Reflectance and scattering properties of highly absorbing black appliqués over a broadband spectral region

Abstract

I present angle-dependent directional hemispherical reflectance (DHR) and bidirectional reflectance distribution function (BRDF) measurements of three highly absorbing black appliqués in the 250-2000-nm broadband spectral region. DHR measurements of Energy Science Laboratories, Inc. (ESLI), Rippey, and Rodel appliqués were obtained at incidence angles of 8 degrees , 50 degrees , and 70 degrees . For an incidence angle of 8 degrees , the ESLI appliqué exhibited the lowest DHR value of 0.3% across this entire spectral region, whereas the Rippey and Rodel had DHR values of 1.5% and 2.0-2.5%, respectively. In-plane BRDF measurements of the appliqués, obtained at a wavelength of 633 nm and incidence angle of 10 degrees , yielded Lambertian profiles from -80 degrees to +80 degrees with values ranging from ~10(-3) sr(-1) for the ESLI, 6 x 10(-3) sr(-1) for the Rippey, and 9 x 10(-3) sr(-1) for the Rodel appliqué. In addition, rms surface roughness and correlation lengths for the Rippey and the Rodel appliqués were determined. The in-plane BRDF data were used to estimate the reflected specular component from Beckmann's scattering theory, and excellent agreement was found.