Abstract

A holographic optical element gathers light scattered from a planar surface and directs it through a pinhole. The sample is rotated in its own plane, and that part of the pinhole light arising from microscopic roughness disappears. This leaves only specular light associated with the average surface contour. A graph of light power through the pinhole versus sample orientation shows a narrow peak centered on the original sample position, surrounded by a specular-reflection plateau. The ratio of the microscopic-roughness-peak height to the specular-reflection-plateau height gives a measure of the sample roughness. Comparisons of sample roughness determined by this method and by traditional methods show a semilogarithmic relationship between AA roughness and this holographic measure of roughness over a certain roughness range. This method is an extension of the Honda¹ holographic method of rapid surface inspection.

© 1990 Optical Society of America