Fast Hardware Implementation of Sub-pixel Search Algorithm for Digital Speckle Correlation Method

Abstract

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.

Hardware Implementation for an Improved Full-Pixel Search Algorithm Based on Normalized Cross Correlation Method

“…Combinational Adaptive Look-Up Tables(ALUTs) As shown in the Table 3, the hardware consumption is relatively small while ensuring higher speed. In FPGA verification, the coordinates of the matching points of the full-pixel search and sub-pixel search [21] are input to the serial port debugger through the serial cables and saved as text information. Comparing this result with the results of MATLAB, the two are completely consistent, indicating that the circuit design of the digital speckle correlation method is correct on the FPGA.…”