Three-dimensional digital image correlation with improved efficiency and accuracy

Three-dimensional (3D) digital image correlation (DIC) is a popular image-based non-contact measurement technique. 3D DIC is generally implemented in a stereo vision system. In this study, we present an epipolar geometry-based searching strategy to enhance the efficiency of 3D DIC in searching the corresponding points between the left and right images. Based on the triangulation principle, a novel method is proposed to compute the 3D position which can minimize the reprojection deviation. Moreover, during measuring the in- and out-of-plane displacement of a loaded object, we present a method to build the world coordinate system on the test surface. In the experiment, the proposed 3D DIC method is employed to measure the profile of a mask model and evaluate the loading response of a tensile specimen made from aluminium (Al) 6061-T6. It is shown that the epipolar geometry-based searching strategy can enhance the searching efficiency. The reprojection deviation of the 3D point derived by the proposed method is less than that of the 3D point obtained from the conventional method. The measured Young's modulus of Al 6061-T6 is close to the standard reference value. The proposed method is also utilized to measure the in- and out-of-plane displacements and strains of the loaded specimen.