Generalized Gradient Based Digital Image Correlation Method for Displacement with Subpixel Accuracy

Basic principle of generalized gradient based digital image (DIC) method for subpixel-accuracy displacement measurement is discussed. The proposed method can cope well with lighting illumination variation or grayscale intensity change on the object surface during measurement by adopting a linear intensity change model, which overcomes the limitations in existing linear least squares based spatial gradient method by adopting constant model. To evaluate the proposed methods, both computer simulation and actual experiment have been carried out. The results show that the proposed method can measure displacement accurately even when substantial intensity variations exist in the experimental images.