DEVELOPMENT OF DIGITAL IMAGE CORRELATION TECHNIQUE FOR ENGINEERING MEASUREMENT

Abstract

Digital image correlation (DIC), including two-dimensional (2D) DIC and stereo DIC, is a very popular non-contact optical technique for full-field deformation and shape measurement. Tremendous applications of DIC have led to remarkable research efforts in this technique and it is becoming mature. Nevertheless, there are still some aspects deserve more investigations. The studies in this thesis are focused on the large rotation issue in 2D DIC, stereo matching, 3D point reconstruction by triangulation, and stereo DIC along with speckle projection for 3D profile reconstruction. To solve the large rotation issue in 2D DIC, the gradient orientation error (GOE) between the gradient orientation at the pseudo-POI and that at the searching point is used to estimate the rotation between the reference and the deformed subsets. To enhance the accuracy and efficiency of the stereo matching in stereo DIC, a stereo-rectification-based stereo matching (SRSM) method and a homography-transform-based stereo matching (HTSM) method are presented. To compare the performances of various 3D reconstruction methods in stereo DIC in measurement accuracy and efficiency. Finally, a stereo DIC method using color speckle projection is proposed using two different projectors, a self-designed laser speckle projector and a digital light projector (DLP).