Patent ID: 9163928
Filing Date: 2015-10-20
Classification: G01B

Abstract:
1. A method for calibrating an interferometer system, the interferometer system including a cavity formed between reference flats in a first interferometer channel and a second interferometer channel, said first interferometer channel and said second interferometer channel located on diametrically opposite sides of the cavity, the method comprising: placing a calibration wafer in the cavity, the calibration wafer defining a plurality of holes therein; acquiring a first intensity frame from the first interferometer channel; acquiring a second intensity frame from the second interferometer channel; determining locations of the plurality of holes based on the first intensity frame; determining locations of the plurality of holes based on the second intensity frame; calculating a first distance between a pair of holes of the plurality of holes based on the first intensity frame; calculating a second distance between the same pair of holes based on the second intensity frame; comparing the first calculated distance relative to the second calculated distance; and adjusting at least one of: a first optical magnification of the first interferometer channel and a second optical magnification of the second interferometer channel based on said comparison of the first calculated distance relative to the second calculated distance to reduce a difference between the first calculated distance and the second calculated distance.