Patent ID: 6624893
Filing Date: 2003-09-23
Classification: G01B

Abstract:
A method of correcting scanning errors in an interferometric profilometer adapted to execute vertical-scanning interferometric measurements by illuminating a test surface and a reference surface aligned in an optical path to provide an interference pattern on an irradiance detector as the optical path difference between said test surface and reference surface is varied with a scanner calibrated to produce a sequence of nominal phase steps, the method comprising the following steps:(a) illuminating said test surface and reference surface while effecting a multistep relative translation therebetween to produce a plurality of interference patterns on said detector, wherein each of said interference patterns is detected after a nominal phase step of the scanner; (b) performing an irradiance analysis on said plurality of interference patterns to calculate an approximate phase change between a first pair of consecutive interference patterns produced during said relative translation; (c) performing vertical-scanning interferometry analysis utilizing said approximate phase change calculated in step (b) instead of a nominal phase step corresponding to said first pair of consecutive interference patterns; and (d) repeating steps (a) through (c) for subsequent pairs of consecutive interference patterns produced by the relative translation between the test surface and the reference surface.