Patent ID: 8345258

Claim:
An optical device for characterizing a test object opposite to a reference surface in a Fizeau optical cavity, comprising: a polarization frequency-shifting element operating on an input beam to generate two orthogonally polarized beams having respective frequencies differing by a first frequency shift; means for projecting said two beams toward said Fizeau optical cavity to produce a pair of test beams and a pair of reference beams, wherein said beams in each pair have orthogonal polarization states and have frequencies differing by said first frequency shift; means for producing a second frequency shift on either one of said pairs of test and reference beams; means for combining said pairs of test and reference beams to produce an interferogram after said second frequency shift has been introduced; and means for detecting and spatially sampling said interferogram; wherein said first frequency shift and said second frequency shift are substantially equal in magnitude and are produced by a transducer component operating simultaneously on both the Fizeau optical cavity and the polarization frequency-shifting element.