Patent ID: 7286240
Filing Date: 2007-10-23
Classification: G01B,G03F

Abstract:
1. A method, comprising: using an interferometer in an interferometry system to produce an output beam comprising a phase related to an optical path difference between a path of a first beam and a path of a second beam, wherein the first beam contacts a measurement object at a first location and the first or second beam contacts the measurement object at a second location, and wherein the first and second locations are different; providing precalibrated information that accounts for contributions to the optical path difference caused by a deviation of the path of the first or second beam from a nominal beam path due to an imperfection of the measurement object at the first location and due to an imperfection of the measurement object at the second location; and determining a position of the measurement object with respect to at least one degree of freedom based on information derived from the output beam and the precalibrated information.