High-precision thickness measurement via dual-path oblique laser triangulation and spatial-topological constraints

Laser triangulation is essential for industrial thickness measurement but faces challenges such as high noise sensitivity and non-uniform reflectivity. To address these issues, this paper presents a high-precision dual-path method based on a complementary optics-algorithm design that combines an oblique-incidence optical configuration with a spatial-topological constrained grayscale centroid method (STC-GCM). The dual-path configuration satisfies the Scheimpflug condition and is designed to enhance signal intensity, imaging quality, and stripe continuity. The STC-GCM integrates Otsu thresholding and morphological denoising with a constraint mechanism based on topological connectivity and geometric validity, thereby converting improved optical observability into robust valid-stripe selection. Comparisons show that the algorithm improves center-extraction accuracy by approximately 34% relative to the conventional GCM and achieves approximately 4× the computational efficiency of the Steger algorithm. Experiments over a 1.0-5.0 mm range yielded a maximum absolute error of 2.3 µm, a linearity of 0.058% FS, and a mean repeatability standard deviation of 0.90 µm. This technique provides a practical approach for high-precision industrial thickness monitoring under the evaluated conditions.