Characterisation of surface roughness by laser light scattering: specularly scattered intensity measurement

The evolution of the surface topography is an indication of the surface wear. This paper aims to describe a 3D method for characterising the surface topography by light scattering. In a first stage, we give the relationship between the light specularly reflected at a rough surface illuminated with a s-polarised laser beam and the surface roughness. In contrast to previous studies, no particular assumptions about the roughness statistics are made. However, the surface roughness is assumed to be small at the scale of the light wavelength. In a second stage, we propose a method for determining some statistical parameters characterising the rough surface from the specular intensity measurements at different incidence angles. This method, applied to the case of different steel surfaces, allows one to determine the root mean square and the kurtosis of the height distribution function, and another parameter depending on its higher-order moments. These results are not in serious disagreement with those obtained from 3D surface profiles measured with optical heterodyne, stylus profilometries and confocal microscopy. (C) 1997 Elsevier Science S.A.