Patent ID: 6137574
Filing Date: 2000-10-24
Classification: G01B,G03F

Abstract:
An interferometry system comprising:an interferometer which during operation directs a reference beam along a reference path and a measurement beam along a measurement path contacting a measurement object and combines the reference and measurement beams to produce overlapping exit beams, the overlapping exit beams indicative of changes in a relative optical path length to a measurement object, the interferometer comprising a variable phase shifter which during operation produces a phase shift in at least one of the reference and measurement beams;a detection system which during operation mixes polarizations of the overlapping exit beams to produce a mixed beam and measures a time-varying intensity of the mixed beam; andan analyzer coupled to the phase shifter and the detection system and which during operation controls the value of the phase shift produced by the phase shifter, measures a phase corresponding to the time-varying intensity of the mixed beam, and determines a spectral representation of cyclic errors in the interferometry system based on the phase of the mixed beam for each of multiple values of the phase shift.