Patent ID: 9441947
Filing Date: 2016-09-13
CPC Classification: G01B,G01D

Claim Text:
1. An interferometric method of facilitating a measurement of an absolute optical path-length difference, the method comprising the steps of: (a) receiving in memory, a first fringe spectrum, from an interferometer comprising two optical paths having an absolute optical path-length difference therebetween that is to be measured, the first fringe spectrum comprising a plurality of non-quadrature spaced light intensity samples, each sample corresponding to a different wavelength of light from a plurality of monitored wavelengths, and the plurality of samples representing at least one full fringe cycle within the first fringe spectrum; (b) determining based on, at least in part, the first fringe spectrum a base estimate of the absolute optical path-length difference, a fringe number, and a quadrant; (c) selecting by a first processor a set of non-quadrature spaced samples from the plurality of samples; (d) computing by the first processor a first relative-phase measurement of the absolute optical path-length difference using the selected non-quadrature spaced light-intensity samples, by expressing each light intensity sample as a combination comprising: (i) a term based on a relative phase φ that is based on a reference wavelength and is independent of the monitored wavelengths, and (ii) a term based on a phase shift estimate δ (e) computing a first measurement of the absolute optical path-length difference by aggregating the first relative-phase measurement, the fringe number, and the quadrant.