Research On Digital Speckle Correlation Method For Displacement Measurement

Because the amplitude and phase of light waves and sound waves are affected by the other objects when they propagate, the light field and sound field are regarded as information carriers. The characteristics of the objects may be studied on a certain extent through detecting the light field and sound field. Apparently, the laser speckles and ultrasonic speckles are a kind of information carriers about the objective characters.Displacement and strain measurement are an important task of mechanical testing. The digital speckle correlation method (DSCM) is an accurate method of measuring displacement field by using computer aid test. Through calculating the variable process of the correlative coefficient along with displacement and strain between two speckle field images gathered before and after movement or distortion of the object, the basic theory of DSCM is to find out the displacement and strain corresponding to the maximum of correlative coefficient which are the displacement and strain corresponding to the fact.According to the laser electronic speckle intervene and stochastic signal correlation theory, the DSCM of the laser speckles and ultrasonic speckles for measuring tiny displacement and strain of rough interface is studied theoretically with combining the computer aid test and digital signal process technology in this paper. Because the movement of a tiny subset around a point inside the scanning area of a deformed body was usually regarded as a rigid body movement, the research of this paper is stressed on establishing mathematic model of the displacement measurement of a rigid body movement. Furthermore, on several kinds of existing arithmetic, a cubic mountain climbing coarse-fine searching method is proposed for finding the maximum of correlation coefficient of three parameters, which is excellent and applied arithmetic. The DSCM for measuring tiny displacement and strain and the cubic mountain climbing coarse-fine searching method are truly validated by program imitating calculation and experimental analysis. Simultaneously, some relevant software programs are worked out and run successfully.