Proposed Interferometric Method of Measurement of Roughness and Autocorrelation Function in Smooth-Finished Surfaces

The proposed interferometric method allows measurement of rms roughness and autocorrelation function in smooth-finished surfaces. In a Jamin interferometer, pairs of coherent beams with variable magnitudes of small lateral shear are produced that are reflected from the test surface and intefere. The intensity of interference fringes is recorded in dependence on the shear of the beams. The differences between maximal and minimal intensities (or visibility) decrease in dependence on the shear, and the course of the decrease corresponds to that of the autocorrelation function. At a fairly great shear the visibility stabilizes at a certain value from which the surface roughness is derived. The theoretical basis of the method is presented, the accuracy is discussed, and the measuring device is proposed.