Scattering from unidirectional ground steel surfaces in the specular direction

Scattering in the specular direction from unidirectional ground steel surfaces having random roughness is studied theoretically and experimentally. The grooves were oriented perpendicular and parallel to the plane of incidence and were illuminated by a light beam that was smaller than the sample size. Expressions for scattering from a one-dimensional rough surface in the specular direction were derived for the both orientations of the grooves. For the same groove orientations, scattering (lambda = 0.633 mu m) from the ground surfaces was measured in the specular direction at angles of incidence from 6 degrees to 82 degrees. The measured rms roughnesses of the surfaces were 0.096 mu m, 0.143 mu m, 0.311 mu m, and 0.501 mu m, respectively. The measured scattering was independent of the orientation of the grooves for the two smoother surfaces and depended on the groove orientation for the other surfaces. Calculations using the derived expressions taking into account the experimental results show that the scattering is independent of the orientation of the grooves if the rms roughness is no larger than similar to 0.16 mu m. (c) 2006 Elsevier B.V. All rights reserved.