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Development of a Laser Speckle Interferometer to Measure Two-dimensional In-plane Vibration in Real-time Based on Fourier Transform with Electronic Circuit

基于电子电路傅里叶变换实时测量二维面内振动的激光散斑干涉仪的研制

基本信息

批准号：
13555063
负责人：
IWATSUKI Nobuyuki
金额：
$ 5.89万
依托单位：
TOKYO INSTITUTE OF TECHNOLOGY
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (B)
财政年份：
2001
资助国家：
日本
起止时间：
2001 至 2002
项目状态：
已结题

项目摘要

Aiming to develop a high-performance vibrometer which can measure multi-dimensional displacement with high accuracy in real-time, a new laser speckle interferometer based on the quad aperture method with a phase detector of interference image using two-dimensional Fourier transform was proposed and was theoretically and experimentally examined. Analogue electronic circuit for two-dimensional Fourier transform was then designed. The results obtained are summarized as follows.(1)A prototype of a laser speckle interferometer with the quad aperture method was built. And by detecting a two-dimensional displacement of lattice type interference image with correlation method, a two-dimensional displacement of a target can be measured.(2)Two-dimensional Fourier transform of the lattice type interference image was theoretically derived. It was then revealed that displacement of the target was in proportion to the phase spectrum at the spatial frequency twice as high as the fundamental spatial frequency of interference image and that the calculation cost could be remarkably reduced in compare with that of the correlation method.(3)Experiments to measure the two-dimensional static displacement were carried out and then the factors to cause measuring error were discussed. It was revealed that the measuring error became smaller as the average visibility of the interference image was higher and as the phase variation in the image was smaller.(4)By selecting laser irradiation point so that the average visibility of the interference image is high and that the phase variation in the image is small, and by applying the 25 points median filter to the image, the measuring error becomes reduced.(5)An analogue electronic circuit which can calculate the phase of the fundamental frequency component of the interference image obtained with C-MOS image sensor according to two-dimensional Fourier Transform in real-time was designed.

为了研制一种能够实时、高精度测量多维位移的高性能测振仪，提出了一种基于四孔径法、采用二维傅里叶变换干涉图像相位检测器的新型激光散斑干涉仪，并进行了理论和实验验证。然后设计了二维傅里叶变换的模拟电子电路。主要研究结果如下：(1)搭建了四孔径法激光散斑干涉仪样机。并通过相关法检测点阵型干涉图像的二维位移，从而测量目标的二维位移。(2)从理论上推导了点阵型干涉图像的二维傅里叶变换。结果表明，在干涉图像基空间频率两倍的空间频率下，目标的位移与相位谱成正比，与相关法相比，计算成本可显着降低。(3)进行了二维静态位移测量实验，讨论了引起测量误差的因素。结果表明，干涉图像的平均可见度越高，图像中的相位变化越小，测量误差就越小。(4)通过选择激光照射点，使得干涉图像的平均可见度较高且图像中的相位变化较小，并对图像应用25点中值滤波器，测量误差减小。(5)可以计算基频分量的相位的模拟电子电路设计了利用C-MOS图像传感器根据二维傅里叶变换实时获取干涉图像的方法。