Synchronous frequency-shift mechanism in fizeau interferometer

An optical device for characterizing a test object opposite to a reference surface in a Fizeau optical cavity, comprising, in combination:

• a light source projecting a light beam into said Fizeau optical cavity to produce a test beam and a reference beam;
• means for producing a first frequency shift between said test and reference beams;
• a polarization frequency-shifting element operating on said test and reference beams to generate two pairs of beams, said pairs being orthogonally polarized, and to produce a second frequency shift on either one of said pairs of beams;
• means for combining said two pairs of 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.

An optical device for characterizing a test object opposite to a reference surface in a Fizeau optical cavity, comprising:

• a combination including
• a Fizeau optical cavity comprising means for producing a frequency shift in a beam emitted by the cavity;
• and
• a polarization frequency-shifting element capable of generating orthogonally polarized beams having respective frequencies differing substantially by said frequency shift;
• said optical cavity and polarization frequency-shifting element being optically aligned so as to convert an input beam into a first pair of orthogonally polarized beams with substantially no relative frequency shift and into a second pair of orthogonally polarized beams with a relative frequency shift substantially equal to twice said frequency shift, thereby producing an output including four beams;
• means for combining said output to produce an interferogram;
• and
• means for detecting and spatially sampling said interferogram;
• wherein said frequency shift is produced in the Fizeau optical cavity and the polarization frequency-shifting element by a transducer component operating simultaneously on both the Fizeau optical cavity and the polarization frequency-shifting element.

A method of characterizing a test object with a Fizeau interferometer comprising the following steps:

• combining a Fizeau optical cavity that includes means for producing a frequency shift in a beam emitted by the cavity with a polarization frequency-shifting element capable of generating orthogonally polarized beams having respective frequencies differing by substantially said frequency shift;
• aligning said optical cavity and polarization frequency-shifting element so as to convert an input beam into a first pair of orthogonally polarized beams with substantially no relative frequency shift and into a second pair of orthogonally polarized beams with a relative frequency shift substantially equal to twice said frequency shift, thereby producing an output including four beams;
• combining said output to produce an interferogram;
• and
• detecting and spatially sampling said interferogram;
• wherein said frequency shift is produced in the Fizeau optical cavity and the polarization frequency-shifting element by a transducer component operating simultaneously on both the Fizeau optical cavity and the polarization frequency-shifting element.