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. Under its influence, the complex texture on the object's surface causes significant errors to the wrapped phase, affecting measurement accuracy. To address this issue, this paper analyzes and establishes an error model for them, highlighting their relationship with the texture direction, and proposes a correction method for complex texture errors based on bidirectional fringe projection point cloud fitting. Theoretically, the point clouds obtained in both directions should be identical. Thus, the method corrects the phase by minimizing the distance between the corresponding points in the two point clouds, ultimately yielding the corrected point cloud. To eliminate overall point cloud displacement caused by calibration parameter errors, a pre-correction process is applied. Comparative experiments show that the proposed method can reconstruct objects with complex textures with higher accuracy. Compared to traditional methods, the mean absolute error (MAE) and root mean square error (RMSE) of the proposed method can be reduced by up to 33.6 % and 39.1 %, respectively.