Speckle interferometry methods for displacement and strain measurements using photorefractive crystal
Speckle interferometry methods for displacement and strain measurements using photorefractive crystal
复制标题
使用光折变晶体测量位移和应变的散斑干涉法
DOI：
10.1016/j.ijleo.2006.04.012
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发表时间：
2007
期刊：
影响因子：
3.1
通讯作者：
Rajpal Singh Sirohi
中科院分区：
文献类型：
--
作者：
M. Ara;Rajpal Singh Sirohi
光折变晶体提供了一些有吸引力的特点，如高分辨率和原位处理。由于图像是可擦除的，这些晶体适合读写应用，因此在散斑摄影，图像处理和全息摄影中具有潜在的用途。钛酸钡（BaTiO3）晶体作为记录介质已被广泛用作一种新型滤波器，用于采用双光束耦合配置的实时平面内位移测量。本文介绍了以batio3晶体为记录介质，在散斑剪切照相中实时测量平面位移和应变的新型光学结构。散斑摄影研究使用一个简单的双光束耦合配置。在散斑剪切摄影中，用两个平行的窄激光束照射一个漫射物体在晶体内部成像，并在该平面上添加一个泵浦光束。由于每个光束和泵浦光束的散斑模式产生折射率光栅。当物体变形时，散斑图案随之移位。我们现在有四个散斑场：两个是由泵浦光束与折射率光栅相互作用产生的，两个是由直接通过晶体传输的变形态产生的。因此，来自物体上各自点的场在穿过晶体后会发生干涉，并产生杨氏条纹图案。由于应变的作用，每个图案中的条纹具有不同的宽度和方向，从而产生莫尔条纹。应变是由莫尔条纹的宽度和方向得到的。实验是在一个有缺口的试样上进行的，该试样受拉伸载荷。平面内位移在另一个实验中单独测量。上述研究是在Nd-Yag激光器上进行的。
Photorefractive crystals offer several attractive features such as high resolution and in situ processing. As the images are erasable, these crystals are suitable for read–write applications and hence find potential use in speckle photography, image processing and holography. The barium titanate (BaTiO3) crystal as recording medium has been extensively used as a novelty filter for real-time in-plane displacement measurements employing two-beam coupling configuration. This paper presents new optical configurations in speckle shear photography to measure in-plan displacement and the strain in real time using BaTiO3crystal as recording medium. Speckle photography studies are made using a simple two-beam coupling configuration. In speckle shear photography, a diffused object illuminated with two parallel narrow laser beams is imaged inside the crystal, and a pump beam is added at this plane. The speckle patterns due to each beam and the pump beam produce index gratings. When the object is deformed, the speckle patterns shift consequently. We now have four speckle fields: two generated from the interaction of pump beam with the index gratings and two pertaining to deformed states directly transmitted through the crystal. Thus, the fields from respective points on the object interfere after passage through the crystal and produce the Young's fringe patterns. Due to strain, the fringes in each pattern are of different width and orientation, resulting in the generation of a Moiré pattern. The strain is obtained from the width and orientation of the fringes in the Moiré pattern. The experiments are conducted on a specimen with a notch, which is subjected to tensile loading. The in-plane displacement is measured separately in another experiment. The above studies are carried out at Nd–Yag laser.