Fizeau interferomenter with simultaneous phase shift

A technology of phase-shifting interference and light beams, applied in interferometers, instruments, scientific instruments, etc., can solve expensive and difficult problems

Active Publication Date: 2008-01-23
4D TECH CORP
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  • Abstract
  • Description
  • Claims
  • Application Information

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Problems solved by technology

[0006] Therefore, the method of Kuchel et al. requires fine-tuning of the length of the delay path, which is difficult and expensive to implement
Additionally, the presence of two incoherent beams creates a noticeable background light that can affect measurements

Method used

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  • Fizeau interferomenter with simultaneous phase shift
  • Fizeau interferomenter with simultaneous phase shift
  • Fizeau interferomenter with simultaneous phase shift

Examples

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Embodiment Construction

[0025] In general, the invention consists in the idea of ​​spatially separating test and reference beams generated by a Fizeau-type interferometer and passing each beam through an encoding filter. By producing orthogonal states of polarization for the test and reference beams, the test and reference beams can be recombined and processed in a spatial phase shifting interferometer to achieve simultaneous phase measurements.

[0026] For the purposes of the present invention, "tilt angle" means the angle between the test and reference surfaces as measured in a Fizeau interferometer relative to ideal parallel conditions. Thus, in the present invention the tilt angle is used to provide fringes of appropriate resolution for the interferometry task at hand.

[0027] The concept of the present invention takes the interferometer device 10 of FIG. 1A as an example. The source 12 of collimated light L is expanded by the expansion lens 14 , reflected off the beam splitter 16 , collimated...

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Abstract

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.

Description

[0001] related application [0002] This application is based upon and claims priority to US Provisional Patent Application No. 60 / 498,522, filed August 28,2003. technical field [0003] The invention relates to the measurement of electromagnetic wavefronts. In particular, the invention relates to the quantitative instantaneous measurement of interfering beams produced by Fizeau interferometers. Background technique [0004] Beam measurement and qualification are important in the manufacture of many optical components such as data storage laser heads. Therefore, many optical interferometry systems have been devised to improve the accuracy and reliability of measurements. Typically, a front-end interferometry setup that generates test and reference beams is combined with back-end optics to account for phase differences between the beams. This can be achieved simultaneously by encoding (or "marking") the beams at the front end, such as by using different polarization states...

Claims

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Application Information

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Patent Type & Authority Applications(China)
IPC IPC(8): G01B9/02
CPCG01B9/02057G01B9/02032G01J2009/0292G01B9/0209G01B9/02G01B2290/45G01B2290/70G01J9/02G01B9/02065
Inventor 詹姆士·E·弥尔勒德詹姆士·C·怀恩特
Owner 4D TECH CORP
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