[LT05b]
Cornell University Program of Computer Graphics 

An experimental study of the correlation between surface roughness and light scattering for rough metallic surfaces.Hongsong Li and Kenneth E. Torrance.In A. Duparre, B. Singh, and ZH Gu, editors, Advanced Characterization Techniques for Optics, Semiconductors, and Nanotechnologies II, volume Proceedings of SPIE Vol. 5878, pages 587832. SPIE, SPIE, Bellingham, WA, July 2005. We present an experimental study of the angular distribution of light scattered from several rough metallic surfaces, which cover a range of roughness conditions. The substrate materials are steel or glass; roughened by beadblasting, grinding, or etching; and aluminumcoated. The measured surfaceroughness statistics are filtered by using a composite roughness model. The raw mechanical roughnesses range from 0.21µm to 2.66µm; the highfrequency smallscale roughnesses range from 0.13µm to 0.86µm. The optical wavelength is 550nm, so that the roughnesstowavelength ratio is of order one. A BRDF model based on the Kirchhoff approximation is used to establish a relationship between surfaceheight statistics and the angular distribution of the scattered light. Angular distributions calculated with the BRDF model are fit to the measurements. The bestfit roughness statistics from the BRDF model agree closely with those measured for the highfrequency smallscale roughness component. The latter roughness component, which has the highest surface slopes, is thus the primary contributor to the angular distribution of the reflected light. We show that the Kirchhoff approximation can be applied to rough metallic surfaces that have multiple scales of roughness and near, but not perfect, Gaussian surfaceheight distributions. This paper is available as a PDF file LT05b.pdf (1.1M).
 
