Optical Method for Two-Dimensional Surface Roughness Measurement.

Abstract

Scattered light from the surface of a specimen illuminated with a beam of light will broaden as the surface roughness increases. The scattered light intensity distribution measured with a CCD camera was approximated with a two-dimensional (2-D) Gaussian function, and the surface roughness in two orthogonal directions was evaluated using the standard deviations σx and σy With respect to the x and y axes of the function. The half-width B and integral width C can be expressed with the standard deviation of the function and they can also be used for evaluating the surface roughness. Two kinds of specimens were used ; ground specimens and wet-blasted specimens with and without directionality of the surface roughness. For ground specimens, the integral width Cy of the cross section perpendicular to the grinding direction increased rapidly with increasing surface roughness Rq, while Cx of the cross section parallel to the grinding direction remained almost unchanged. For the wet-blasted specimens, on the other hand, no difference was observed between Cx and Cy.