Three-dimensional displacement measurement based on the combination of digital image correlation and optical flow

This paper proposes what we believe is a novel simultaneous three-dimensional (3D) displacement measurement technique based on a combination of digital image correlation (DIC) and optical flow (OF). In this method, both the in-plane and out-of-plane displacements can be accurately extracted from only two continuous interferograms. DIC estimates the velocity field between two consecutive frames. According to the optical flow constrained equation, we can then obtain the whole-field out-of-plane displacement map by the estimations of the in-plane displacement components and the local frequency of the original image. The proposed method's operation is simple compared with other phase demodulation methods. Moreover, the new method works perfectly in areas with dense fringes. To verify its effectiveness, we applied a new algorithm to simulated and experimental interferograms. The results of our simulation and experiment show that the new method can demodulate the out-of-plane component of the deformation-phase from the visible in-plane velocity field without an unwrapping process. Further, the proposed algorithm provides a new approach to measure whole-field 3D displacement and dynamic deformation.