3-D Morphology Measurement Method for Constant-Diameter Straight Pipes Based on Face-to-Face Mirror Binocular Vision and External Tracking

Abstract

To address the low accuracy of optical measurements of the complete 3-D morphology of pipelines caused by confined internal spaces, this article proposes a high-precision 3-D measurement method for constant-diameter straight pipes (CDSPs) based on face-to-face mirror binocular vision (F2F-MBV) combined with external marker tracking. The method first constructs a structured-light measurement model using the F2F-MBV system to accurately capture local inner wall point clouds. Subsequently, a pipeline self-contour reconstruction algorithm corrects geometric distortions in external images and extracts the centers of external marker points with high precision. Finally, the trajectories of the external markers, tracked by an external binocular system, are used to perform global registration of inner wall point clouds across all frames, yielding a continuous and complete 3-D morphology of the pipeline inner wall. Experiments on CDSPs demonstrate mean diameter and coaxiality errors of 0.005 and 0.063 mm in simulations and 0.067 and 0.092 mm in a precision stainless-steel pipe, respectively. Further validation experiments achieve a mean absolute height-difference error of 0.041 mm and a surface reconstruction error of 0.110 mm for local geometric variations and defect reconstructions, respectively. The results confirm the capability of the proposed method for the accurate reconstruction and measurement of irregular pipeline inner wall topographies while maintaining a favorable balance between accuracy and system complexity.