Measurement Of Displacement In-Plane Based On Digital Speckle Photography

Optical measurement technique is a rapidly developing and relatively new test technology. Digital Speckle Photography (DSP) is an important branch of optical measurement technology, it developed on the basis of laser technology, holographic technology, video technology, electronic technology, information and image processing technology, computer technology and precision measurement technology. Its basic idea is to use the speckle in space formed by the beams from object rough surface reflection or transmission as the carrier of information to achieve the object surface displacement or deformation detection. This method has advantages in non-contact measurement, high precision, full-court and has extensive application in the in-plane displacement and deformation measurements especially.This paper mainly studied the basic theory, principle, methods of measurement and technical characteristics, etc of DSP and digital speckle correlation in frequency domain. DSP based on charge-coupled device CCD and electronic addressed liquid crystal EALCD,computer simulation of DSP based on computer image processing technology and digital speckle correlation in frequency domain were respectively studied. DSP based on CCD and EALCD are carried on the experiment research including designing respectively the subjective and objective speckle record light path and the light path for fringe reconstruction using full-court analysis and point-by-point analysis.In the experiment, we use the software MATLAB to do digital filter enhancement, smooth denoising and fringe thinning for the acquired speckle interference fringes, and do the analysis and research comparatively for speckle interference fringes achieved by the method of DSP based on CCD and EALCD and computer simulation DSP, and do a comparative study of measurement precision of in-plane displacement using the two methods above and digital speckle correlation in frequency domain. Experimental results showed that the three methods all have high application value.