Contrast modulation interferometry

A contrast modulating technique for interferometric fringe analysis is introduced. The basic idea of the interferometry is employing an amplitude-stepped reference wavefront in an interferometer to generate contrast-modulated interferograms and evaluating the phase of a test wavefront based on intensities of the interferograms. A general phase evaluation algorithm for the interferometry is derived. As an example of the phase measuring technique, we describe a three-step algorithm and an interferometer used to realize a three-step measurement.