Depth-of-field extension method for telecentric structured light based on dual-viewpoint stitching

Structured light technique is widely used in three-dimensional (3D) reconstruction and measurement with the advantages of high precision and efficiency. However, traditional telecentric structured light systems are limited by optical configurations and depth-of-field (DOF) constraints, making it difficult to achieve large-scale height reconstruction. To address this challenge, this paper proposes a dual-viewpoint stitching method to extend the DOF of the telecentric system. First, the two camera viewpoints are vertically shifted using a displacement stage while maintaining a common focal region to capture images and point clouds at different height positions. Then, we propose a pre-calibrated point cloud stitching method leveraging the geometric consistency of telecentric lenses, which determines and optimizes the stitching matrix for point clouds within the common focal region of the dual viewpoints using standard components. This pre-calibrated method effectively eliminates the need for object feature point clouds and multiple registrations. Finally, the point clouds obtained at different height positions are stitched together using the stitching matrix, thereby achieving dual-viewpoint stitching and extending the DOF range. Experiments demonstrate that the DOF is extended to 1.7 times the original range, with relative errors of repeated measurements within 0.12%. The proposed method extends the DOF range while preserving high measurement precision and significantly improving stitching efficiency, showing excellent engineering applicability.