Surface Roughness Measurement by Optical Pattern Projection

This paper is concerned with the measurement method for surface roughness by optical pattern projection. This method can be classified into two fundamental configurations. The one has one imaging system including the sample surface placed on the way of the optical pathes, which the author calls “OTF method”. The other has two step imaging systems. The first system projects the input image on the sample surface, and the second forms the output image from the reflected image on the sample surface. The author calls the second method “Re-imaging method”. The author examined the contrasts of the output images by the OTF method experimentally, and found the correlation between the contrast data and calculated results of specular component e-g expected from the scattering theory. The OTF method is restricted the range of measurement for the roughness Ra below about 0.1μm. The possibility for larger range measurement by the Re-imaging method is examined experimentally in this paper.