Evaluation of sub-pixel displacement measurement algorithms in digital image correlation

The accuracy of digital image correlation method is based on the sub-pixel displacement measurement algorithm. In this paper, four kinds of commonly used sub-pixel displacement measurement algorithms, including Newton-Raphson method, curved surface fitting method, gradient-based algorithm and iterative and spatial-gradient algorithm, are introduced. The performances of the four methods are compared using computer-simulated images. The results show that the iterative and spatial-gradient algorithm can obtain the most accurate and stable results of displacement measurement under various conditions. In addition, this algorithm is simple and easy to implement. Therefore, the performances of this algorithm are the best.