ALarge-shearing block prism in electronic speckle pattern interferometry
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摘要: 设计了一种可实现电子散斑干涉的大错位方棱镜。将普通方棱镜的一个面磨去一个楔角后变为斜面，该斜面和相邻的一个面镀反射膜，其他二个面镀增透膜。垂直入射的光线经过分光后变成二束光，分别经过平面反射和斜面反射，出射的二束光线就分开了。将该大错位方棱镜置于CCD镜头前，一个物体可以成二个错位的像；相邻的二个物体可叠加成像。错位量由楔角决定，错位量足够大，可实现大错位电子散斑干涉。根据试件大小和成像距离，楔角的大小可选择在1到10之间。对中心加载周边固定圆盘进行了电子散斑载频干涉实验，证明了大错位方棱镜能够高质量地实现电子散斑干涉, 实现位移场测量。Abstract: A large-shearing block prism is designed, which can be used in electronic speckle pattern interferometry (ESPI). A wedge is made of a beam splitter cube on one of its surface. The oblique plane and one of its adjacent surfaces of the block are coated by reflection enhancing film. And other two surfaces are coated by anti-reflection films. When a normal incidence beam arrives at one of the reflect-reducing coating surfaces, the beam is split into two after inner beam-splitter. The two outgoing beams can be separated from each other when they are reflected by a parallel reflector and a tilted reflector respectively. If the large-shearing block prism is placed in front of the lens of a CCD camera, an object can be imaged into two shearing images and two adjacent objects can be imaged at same place on image plane. The shearing amount of the image is determined by the angle of the wedge. A large-shearing electronic speckle pattern interferometry (ESPI) can be realized by using the block prism if the shearing amount is sufficient. The angle can be selected from 1 degree to 10 degree based on the size of test specimen and the object distance. Carrier modulation experiments using a centrally loaded clamped circular plate are completed. The experimental results prove that the large-shearing block prism can be used in ESPI and the displacement fields can be obtained effectively.
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