Mirror pose calibration for plane mirror-assisted DIC using a double-sided target

In plane mirror-assisted digital image correlation (PMA-DIC) measurements, the calibration accuracy of the plane mirror pose directly affects the accuracy of the coordinate transformation between the real and virtual images. Existing methods, however, suffer from several limitations, such as low transformation accuracy, operational complexity, and contamination of the mirror surface. Therefore, a plane mirror pose calibration method based on joint optimization with multiple constraints is proposed in this study. The method employs a double-sided target (DST) with speckle patterns, whose two surfaces are independently imaged by two plane mirrors. By incorporating the known geometric relationship of the DST, planar constraints on the pose parameters of the plane mirrors are established. The DST is then moved to several different positions, and DIC is used to calculate the displacement fields of the speckle patterns on the DST surfaces, from which displacement-field constraints are further constructed. The pose parameters of the plane mirrors are then estimated by jointly enforcing these multiple constraints. Finally, through dynamic and static experiments as well as comparative analysis, it was found that the surface reconstruction error of the plane mirror was approximately 0.018 mm, and the average relative error in rigid-body displacement was approximately 1.9%, thereby validating the effectiveness and accuracy of the method under study. This study provides an effective plane mirror pose calibration method for multi-view measurements in PMA-DIC.