| 摘要 |
This invention includes a method and apparatus for nondestructive testing of objects. The invention concerns a method of practicing shearography, i.e. forming two laterally-displaced images of the test object and causing these images to interfere. The invention includes the steps of directing a beam of coherent light onto the object and directing the reflected light onto a detector, such as a photographic film. A pair of lenses, laterally-displaced from each other, are placed between the object and the detector. Both lenses produce an image of the object at the plane of the detector, and because the lenses are spaced apart, the images produced are also spaced apart. In other words, the dual lens system causes two images from two different regions on the surface of the object to meet at the image plane. These images interfere with each other to form a speckle pattern. When the object is deformed, the speckle pattern changes. Comparison of the speckle patterns with and without deformation yields information on the relative deformation of the two regions of the object. The method can be used to evaluate nondestructively the integrity of the object.
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