Patent ID: 6552806
Filing Date: 2003-04-22
Classification: G01B

Abstract:
A method for minimizing the optical path difference between a test beam path and a reference beam path produced in an interference microscope objective having a reference-arm assembly that comprises a reference lens and a reference mirror, and having first scanning means for carrying out interference measurements of a test surface, the method comprising the following steps:(a) providing second scanning means for translating the reference-arm assembly along said reference beam path; (b) translating the reference-arm assembly through a plurality of positions along the reference beam path using said second scanning means; (c) measuring a fringe modulation at predetermined locations corresponding to said plurality of positions along the reference beam path; (d) determining a location of the reference-arm assembly along the reference beam path corresponding to an optimal fringe modulation; and (e) fixing said optimal-fringe-modulation location of the reference-arm assembly such that interferometric measurements of the test surface may be carried out by varying the optical path difference therefrom.