<title>Optical methods for spatial noise removal in interferometry</title>

Abstract

The purpose of this paper is to present an analysis of the interference of light scattered from different planes in a simple interferometer, in order to establish techniques for final output fringe contrast enhancement and spatial noise removal, which are simple to implement. The approach developed here involves modifying the spatial coherence of the illuminating wave. By controlling the correlation length of this wave, a time averaged interferogram along with another for which a t phase shift has been introduced into the reference arm, provides the necessary information to retrieve the fringe pattern of interest without noise. The approach suggested allows the controlling parameters to be easily varied optically in order to deal with different spatial noise types and scales. The benefits of this method are to the case for which the long range and slowly varying surface or index profile under test, is to be accurately measured. Simulations are presented and an evaluation of the effectiveness of the proposed coherence degradation procedures is given.