Improvement in accuracy of a digital image correlation method by a coarse-to-fine approach

A digital image correlation (DIC) method has sufficient high accuracy at the time of infinitesimal deformation. However, mismatching may arise depending on the texture of an image and the right result may be unable to be obtained. Although accuracy improved more to enlarge subset size, the demerit of which the computation time increases and it cannot respond to a small image existed. Therefore, when subset size was set small, improvement in the accuracy of the digital image correlation method was investigated by aiming to reduce mismatching. The accuracy by the coarse-to-fine approach of performing coarse search by the image on which resolution was dropped first, and performing fine search by a high-resolution image after that was examined. In the digital image correlation method using coarse-to-fine approach, the result checked that an accurate result was obtained, without mismatching occurring, even when subset size was set up small. Moreover, in the digital image correlation method using the sum of absolute difference (SAD) method, it was possible to have analyzed with accuracy almost equivalent to the digital image correlation method by a correlation coefficient, and it succeeded also in reduction of mismatching at the time of setting up subset size small.