Compact shearography system with adjustable shear distance
AssigneeNikon Corporation
InventorsEric Peter Goodwin, Daniel Gene Smith
Life of this patent
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Abstract
Shearography systems provide independent setting of fringe frequency and shear magnitude by situating an interferometer with a tiltable reflector proximate a pupil plane of an imaging optical system. Fringe frequency can be selected based on a modified Savart plate. In other examples, a Wollaston prism or a polarization grating is translated with respect to an image sensor to vary shear magnitude while maintaining a substantially fixed fringe frequency.
Claims26
A shearography system, comprising:
- a shearing optic operable to provide a variable shear between a first image and a second image of a test object, wherein the first image and the second image are speckle images;
- a detector;
- and
- an optical system operable to direct the variably sheared first image and second image to the detector at respective angles to establish a substantially fixed fringe frequency associated with interference of the variably sheared first and second images.
A shearography system, comprising:
- a detector;
- and
- an optical system operable to vary a shear between a first image and a second image of a test object independently of a fringe frequency produced by interference of beams associated with the first image and the second image at the detector, wherein the first image and the second image are speckle images.
A shearography method, comprising:
- situating a shear optic at a pupil of an imaging system to variably establish a shear;
- and
- interfering sheared first and second images produced with the imaging system to produce a fringe frequency that is independent of the variably established shear.
A metrology instrument that measures an object based on shearography, comprising:
- a polarizing beam splitter situated to divide an optical beam from an object into a first polarized beam and a second polarized beam, wherein a state of polarization of the second polarized beam is different from a state of polarization of the first polarized beam;
- a shearing optic situated to laterally shift the first polarized beam and the second polarized beam from the polarizing beam splitter with respect to each other;
- an imaging system situated to produce a first image and a second image corresponding to the first polarized beam and the second polarized beam, respectively;
- and
- a detector situated to detect an interference of the first image and the second image, wherein the shearing optic is situated proximate a pupil of the imaging system.
Dependencies are inferred from the claim text.