Abstract
A new measuring method which can estimate quantitatively the periodical fine surface roughness, for example the surface of magnetic memory disk and laser mirror finished by ultraprecision diamond tool machining is presented in this paper. This principle of measurement is based on Fraunhofer diffraction. Relations between the surface roughness and Fraunhofer diffraction patterns of diamond turning surfaces are discussed theoretically and experimentally. The results obtained are summarized as follows: A conventional equation which can accurately estimate the surface roughness of less than 200nm Rmax by measuring the intensity values of 0-3 order diffractions is derived from theoretical analysis based on Fraunhofer diffraction. From the measurements of surface roughness of various workpieces including a magnetic memory disk, it is found that this Fraunhofer diffraction method makes it possible to measure the surface roughness within 10% errors from 1nm to the maximum 200nm.
