Patent ID: 8902429

Claim:
An interferometry system, comprising: at least two reference flats configured to receive a sample in a cavity formed by a first reference flat and a second reference flat of the at least two reference flats; at least one illumination source configured to illuminate at least one surface of the sample and at least one surface of the at least two reference flats; at least one detector configured to receive one or more interferograms produced by illumination reflected from at least one of: the at least one surface of the sample and the at least one surface of the at least two reference flats; and at least one computing system, the at least one computing system configured to: determine an initial focus position of the at least one detector utilizing a first set of interferograms; collect data associated with an inner edge of a ring of the cavity utilizing one or more additional sets of interferograms received by the at least one detector at one or more additional positions near the initial focus position; and determine a selected focus position of the at least one detector utilizing the collected data.