Error correction of complex texture objects based on bidirectional fringe projection point cloud fitting

In structured light 3D measurement systems, defocusing of the camera is inevitable. Because of camera defocus, the object’s complex surface texture introduces substantial phase errors, degrading measurement accuracy. To address this issue, this paper analyzes and formulates an error model for phase distortions arising from complex textures, and elucidates how these phase errors quantitatively depend on the relative orientation between fringe patterns and surface texture. Thus, a correction method for complex texture errors based on bidirectional fringe projection point cloud fitting is proposed. Theoretically, the point clouds obtained in both directions should coincide. Thus, the method corrects the phase by minimizing the Euclidean distance between the corresponding points in the two point clouds, ultimately yielding the corrected point cloud. To remove global shifts from calibration parameter errors, a pre-correction process is applied through point cloud matching. In comparative experiments, our method achieves up to 33.6% reduction in the mean absolute error (MAE) and 39.1% reduction in the root mean square error (RMSE) versus conventional approaches. These results demonstrate its superior accuracy for reconstructing objects with complex texture.