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US 10,330,463 B2Granted
Spatial phase-shift shearography system for non-destructive testing and strain measurement
AssigneeOakland University
InventorsLianxiang Yang, Xin Xie, Nan Xu, Xu Chen
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Abstract
Embodiments of a shearography system may include light sources configured to produce beams of light to illuminate a test area. Each of the beams of light may include a different wavelength. A camera may be configured to obtain intensity information corresponding to reflections of the lights off of the test area. An optical shearing device may be disposed in an optical path between the light sources and the camera and the optical shearing device may be configured to provide a shearing angle.
Claims14
A shearography system comprising:
- a plurality of light sources each configured to produce a beam of light to illuminate a test area, each of the beams of light having a different wavelength;
- a camera configured to obtain intensity information corresponding to reflections of the plurality of light sources off of the test area in a single testing image and a single reference image;
- an optical shearing device disposed in an optical path between the plurality of light sources and the camera, the optical shearing device including a plurality of mirrors and configured to provide a shearing angle;
- a processor configured to determine a strain measurement corresponding to the test area in two directions entirely from the single reference image and the single testing image via spatial phase-shifting;
- and
- wherein the plurality of light sources comprises a first light source configured to produce a first light having a first wavelength, a second light source configured to produce a second light having a second wavelength, and a third light source configured to produce a third light having a third wavelength;
- wherein the strain measurement includes an in-plane strain measurement and an out-of-plane strain measurement;
- the camera is configured to obtain the testing image while the first light source, the second light source, and the third light source are simultaneously illuminating the test area and spatially overlapping at the test area;
- the single testing image includes a first interferogram corresponding to the first light source, a second interferogram corresponding to the second light source, and a third interferogram corresponding to the third light source;
- the first interferogram, the second interferogram, and the third interferogram overlap spatially in the camera;
- and
- wherein the optical shearing device is configured as a Michelson interferometer.
9 more elements
A method of determining strain, the method comprising:
- illuminating, via a plurality of light sources simultaneously, a test area of a test object;
- capturing, via a single camera, a single reference image;
- capturing, via the camera, a single testing image;
- and
- determining a strain measurement solely from the single reference image and the single testing image via spatial phase-shifting;
- wherein each of the light sources of the plurality of light sources is configured to produce a beam of light;
- the beam of light produced by each light source has a different wavelength than the beam of light produced by each other light source;
- the beam of light produced by each light source spatially overlaps with the beam of light produced by each other light source at the test area;
- the strain measurement includes an in-plane strain measurement and an out-of-plane strain measurement;
- capturing the single reference image includes capturing a plurality of spatially overlapping interferograms, each interferogram corresponding to a respective light source of the plurality of light sources;
- and
- the beam of light produced by each light source propagates from the test area to a Michelson interferometer and then to the single camera.
9 more elements
A method of determining strain, the method comprising:
- illuminating, via a plurality of light sources simultaneously, a test area of a test object such that light from the plurality of light sources spatially overlaps at the test area;
- capturing, via a camera, a single reference image of the test object;
- capturing, via the camera, a single testing image of the test object;
- and
- determining a strain measurement solely from the single reference image and the single testing image via spatial phase-shifting;
- wherein determining the strain measurement includes applying a Fourier transform to the reference image to generate a reference spectrum, and applying a windowed inverse Fourier transform to the reference spectrum to generate a phase map corresponding to the reference image;
- the strain measurement includes an in-plane strain measurement and an out-of-plane strain measurement;
- capturing the single reference image includes capturing a plurality of spatially overlapping interferograms corresponding to the plurality of light sources;
- light from each light source of the plurality of light sources has a different wavelength;
- and a Michelson interferometer is disposed in an optical path of light from the plurality of light sources between the test area and the camera.
7 more elements
Dependencies are inferred from the claim text.