Digital Speckle And Its Study Of Application In Deformation Measurement

In recent years, because of the widely use of CCD and computer, speckle measurement, which ever regarded as the nature enemy of holography, has been researched very extensively. Surrounding the technique of digital speckle, many scholars deploy extensive research on it. According the mode of information extraction, digital speckle metrology could be divided into digital speckle pattern interferometry (DSPI) and digital speckle photography (DSP), In the latter, digital speckle correlation method (DSCM), which also been called digital image correlation (DIC) is the method which has been widely used nowadays.Consulting a great deal of literature, on the basis of digital speckle metrology, author introducing the digital speckle correlation theory in space domain and frequency domain, the keystone is computer aided speckle interferometry (CASI). The experimentation of this paper is mainly surrounded the in-plane displacement measurement, on the basis of experiment we program all methods.The paper introduces the speckle and the properties of speckle. Analysis the digital speckle correlation method in space domain and compares three kind of correlation coefficients, choose the best to do correlation measurement. Aiming at its big searched quality and long searched time, we do some improvements on it to improve the measured speed. Introduce the digital speckle correlation method in frequency domain and do some improvement on it to eliminate the blur aspect, then compare four kinds of filters and choose the best. Mainly introduce the method of CASI, contra pose the custom addition CASI, which has a poor signal-noise-radio and bad anti-noise capacity, we propose a subtraction CASI. By analyzing the density addition,subtracting CASI and amplitude addition,subtracting CASI, then find that the amplitude subtracting CASI has the best anti-noise capacity, highest signal-noise-radio and highest measured accuracy, in the end we improve its measured range. Use the MATLAB program all methods and give the obvious analysis results.