Selection of subset size of sub-pixel displacement registration algorithm in digital speckle correlation measurement

Abstract

A selection method of subset size in sub-pixel displacement registration was proposed in this paper. According to three algorithm principles, including interpolation and fitting of distribution of the correlation coefficients, and gradient-based algorithms of sub-pixel displacement registration in digital speckle correlation measurement, the subset sizes influencing on the precision and efficiency of these algorithms were studied using computer-simulated speckle patterns. The optimal algorithm and subset size were obtained in various measurement ranges. Results show that the subset size becomes bigger while certain algorithm is more accurate. The accuracy and efficiency can be improved as the subset size is appropriate. So, the selection of subset size is an important factor for sub-pixel displacement registration in digital speckle correlation measurement.