Digital speckle correlation method is widely used in the areas of three-dimensional deformation and morphology measurement. It has the advantages of non-contact, high precision, and strong stability. However, it is very complex to be carried out with low speed software implementation. Here, an improved full pixel search algorithm based on the normalized cross correlation (NCC) method considering hardware implementation is proposed. According to the field programmable gate array (FPGA) simulation results, the speed of hardware design proposed in this paper is 2000 faster than that of software in single point matching, and 600 times faster than software in multi-point matching. The speed of the presented algorithm shows an increasing trend with the increase of the template size when performing multipoint matching.

Digital speckle correlation measurement method is an important way in the areas of three-dimensional deformation and morphology measurement. It carries the advantages of non-contact, high precision and strong stability. The sub-pixel search algorithm which is used to improve the accuracy of displacement measurement is one of the key technologies in digital speckle correlation method. In order to reduce the computational complexity, the sum of absolute differences (SAD) is used as the correlation function. Special fixed-point arithmetic is designed to solve the problem of processing floating-point calculation during the hardware implementation. Experimental results show that the speed of hardware implementation is more than 600 times higher than that of software implementation. The sub-pixel search accuracy is about 0.1 pixel, and the search error is about 0.03 pixel.

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