Optical EngineeringOptical method for spatial noise removal in interferometry
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We present an analysis of the interference of light scattered from different planes in a simple interferometer, to establish a method that will allow the final output fringe contrast to be enhanced through spatial noise removal. The approach developed 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 ? phase shift has been introduced into the reference arm is shown to provide the information necessary to retrieve the fringe pattern with relatively little noise remaining. The approach suggested allows the controlling parameters to be easily varied optically in order to suppress different spatial noise types and scales. The greatest benefits of this method are in cases where large-scale and slowly varying surfaces or index profiles are to be accurately measured. Simulations are presented and the effectiveness of the proposed coherence degradation procedure is evaluated.