| 摘要 |
The tilted relationship between the reference and test mirrors ( 24,26 ) of a Fizeau interferometer is used to spatially separate the reflections (R,T) from the two surfaces. The separate beams (R,T) are filtered through a spatial polarization element ( 32 ) that provides different states of polarization to the beams. The beams (R,T) are subsequently recombined to form a substantially collinear beam that is processed using a spatial-phase-shift interferometer ( 44 ) that permits quantitative phase measurement in a single video frame. Alternatively, two beams ( 104,106 ) with orthogonal polarization are injected into the Fizeau cavity ( 20 ) at different angles, such that after reflection from the reference and test optics ( 24,26 ) they are substantially collinear. Unwanted reflections are blocked at the focal plane through the use of a circular aperture ( 112 ). Short coherence length light and a delay line ( 84 ) may be used to mitigate stray reflections, reduce measurement integration times, and implement temporal phase averaging.
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