Study Of In-plane Micro-displacement Measurement Based On Digital Speckle Correlation Method

Digital speckle correlation method, also known as digital image correlation method, which is a non-contact, high-precision, no damage, overall measurement computer-aided displacement measurement method, it have been widely applied to experimental mechanics and other fields of scientific research, we are now moving towards high temperature, biological, micro, new materials and other fields going. But the entire pixel positioning speed and the subpixel precision of the current digital speckle correlation method is still exist certain deficiencies. This paper studies how to further improve the positioning speed of the entire pixel, and discussed the advantages and disadvantages of subpixel displacement localization algorithm, for better meet the needs of scientific research and practical engineering survey.Firstly, briefly introduces the forming principle of speckle, explains the reasons of speckle pattern can be micro-displacement measurement, discuss the characteristics of correlation coefficient, and establishes the mathematical model of digital speckle correlation method.Then, introduces a novel based on swarm intelligence Cuckoo Search algorithm and analyses of its efficiency; for its shortcomings introduces a non-uniform mutation operator, particle swarm optimization, gaussian disturbance to improve the random step and location update strategy of cuckoo search algorithm, and with four different standard test function checks the performance of the improved algorithm; in view the efficiency of the improved cuckoo search algorithm, this article introduces it into the field of digital speckle correlation method, describes the principles of the algorithm when measuring the displacement, discusses the influence of different parameters on the computational efficiency, fully compares the performance of this improved algorithm and the commonly used integer pixel algorithm.Finally, a body of rigid body translation, rigid-way stretch and rotate three different micro-strain state was simulated, while the four common subpixel displacement algorithm accuracy and stability under different strain state were compared found that Newton-Raphson method accuracy and stability is best under complex environment, and make a combines with improved relevant search algorithm and Newton-Raphson method to measure the micro displacement of frosted glass, the results show that the proposed algorithm is feasible and efficient in the particular experiment.