Patent ID: 7538887

Claim:
A method for analyzing a surface of a test object having surface properties using white light interferometry and a phase-shifting interferometer having a reference surface, the method including: positioning a reflective surface at a location corresponding to a test object location in the interferometer; using a phase shift driving mechanism to change the relative distance between the reflective surface and the reference surface; applying a first input to the phase shift driving mechanism to acquire a first plurality of interferograms from the interferometer; determining a mean phase shift from the plurality of interferograms; generating a second input to the phase shift driving mechanism of the interferometer to acquire a second plurality of interferograms; calibrating non-linear phase shift results from the second plurality of interferograms to change the second input supplied to the phase shift driving mechanism of the interferometer to produce linear phase shift results; replacing the reflective surface with the test object; supplying the changed second input to the phase shift driving mechanism to acquire successive pluralities of interferograms from the interferometer; comparing the successively acquired interferograms with corresponding signals modeled with the properties to be measured to determine an optimal match.