Research on phase unwrapping of cyclic complementary gray code based on gradient correction

In the field of non-contact 3D reconstruction, structured light 3D reconstruction combining phase-shifting and Gray code is a high-precision reconstruction method. To address the problem of phase jumps easily occurring during phase unwrapping with traditional Gray codes, this paper proposes a cyclic complementary Gray code phase unwrapping algorithm based on gradient correction. Firstly, the wrapped phase image is converted based on the cyclic complementary Gray code to obtain the absolute phase image. For fixed-value phase jumps caused by blurred fringe order edges, phase jump points and their directions are determined through the second-order gradient of absolute phase, followed by phase correction to obtain smooth and continuous absolute phases. In the reconstructed 3D point cloud of the gypsum sculpture, the number of discrete points decreased by 96%. The experimental results indicate that the algorithm effectively discriminates phase jump points and corrects phase jumps without relying on pre-calibrated threshold values.