Two-Dimensional Surface Roughness Measurement Using Scattered Light(Optical Method 3)

Abstract

Scattered light from the surface of a specimen will broaden as the surface roughness increases. The surface of ground specimens was illuminated with a halogen light beam. The scattered light intensity distribution was measured with a CCD camera and it was approximated by a two-dimensional Gaussian function; the surface roughness in two orthogonal directions was evaluated using the standard deviations σ_x and σ_y with respect to the x- and y-axes of the function, the y- axis being taken as the grinding direction of the specimen. The half-width B and integrated width C which represent the broadness of the scattered intensity distribution can be expressed in terms of the standard deviations σ_x and σ_y of the function as B_x=2.35σ_x, B_y=235σ_y, C_x=2.51σ_x, C_y=2.51σ_y and they can also be used for evaluating the surface roughness. The standard deviations σ_x, the half-width B_x and the integrated width C_x of the cross section of the intensity distribution perpendicular to the grinding direction increased rapidly with increasing the root-mean-square deviation of the profile R_q, while the values for the cross section parallel to the grinding direction remained almost unchanged. The scattered intensity distribution has a close correlation with the slope angle distribution of the surface roughness profile measured with a stylus profilometer.