Determination of surface roughness from scattered light

The authors describe the determination of the root-mean-square (RMS) roughness of hand-lapped stainless steel specimens using the scattered intensity measured by a set of detectors spaced along a circular arc. The ratio between the specular beam and the total scattered light intensity is used to determine the RMS roughness. The authors explain what information is obtained from surface profiles taken with a stylus instrument and from light scattering data taken by the DALLAS instrument. Using an approximate scalar theory of electromagnetic scattering by random rough surfaces they compute the intensity of the scattered beam as a function of angle. They discuss the choice of autocorrelation function for the surface and do a least-squares fit for the parameters that characterize the surface. Results of the calculations are given.<
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