COHERENCE SCANNING INTERFEROMETRY USING PHASE SHIFTED INTERFEROMETRTY SIGNALS

摘要

Low-coherence scanning systems and methods for operating the same include simultaneously measuring two phase-shifted interferograms corresponding to intensity patterns produced by interfering test light reflected from a test object with reference light on respective first and second detectors, in which the test light and reference light are derived from a common source. The interferograms measured by the first detector define a first set of scanning interferometry signals, and the interferograms measured by the second detector define a second set of interferometry signals corresponding to substantially the same multiple transverse locations on the test object, in which each interferometry signal in the second set is phase-shifted relative to a corresponding interferometry signal in the first set. An electronic processor processes the first set and second set of interferometry signals either independently from each other or in a combined manner to obtain information about the test object.

主权项

1. A low-coherence scanning interferometry system comprising:
an interferometry apparatus comprising a light source, an interferometer, a first detector, and a second detector, the apparatus configured to simultaneously measure, for each optical path length difference (OPD) of a sequence of OPDs between test light reflected from a test object and reference light, first and second phase-shifted interferograms corresponding to intensity patterns produced by interfering the test light reflected from the test object with the reference light on the first and second detectors, respectively, the test light and the reference light being derived from the light source, each interferogram measured by the first detector defining a first set of interferometry signals corresponding to multiple transverse locations on the test object, each interferogram measured by the second detector defining a second set of interferometry signals corresponding to substantially the same multiple transverse locations on the test object, wherein each interferometry signal in the second set is phase-shifted relative to a corresponding interferometry signal in the first set, every interferometry signal comprising a series of intensity values corresponding to the sequence of OPDs; and an electronic processor coupled to the interferometry apparatus, wherein the electronic processor is configured to perform operations comprising: i) processing the first set of interferometry signals, independently from the second set of interferometry signals, to obtain first processed information about the test object over the multiple transverse locations; ii) processing the second set of interferometry signals, independently from the first set of interferometry signals, to obtain second processed information about the test object over the multiple transverse locations; and iii) combining the first processed information with the second processed information to determine the information about the test object with the reduced sensitivity to errors.