Interferometric measurements of mid-spatial scale surface irregularities

Abstract

A simple method which can be used to map mid-spatial scale surface irregularities with high signal noise ratio is described. Two major sources of errors are analyzed and removed. One is the contributions of small-scale irregularities of the reference surface, which are subtracted by shifting the test surface laterally by a distance.The other is the spurious response of CCD, which is removed by interpolation function. The presented method is verified by simulations and experiments. It shows that it can measure mid-spatial scale surface irregularities exactly and smaller scale surface irregularities can be obtained by making measurement for a series of the lateral shifting values corresponding to one-half of the pixel space on CCD.