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A Fast and Robust Detection Algorithm for Extraction of the Centre of a Structured Light Stripe
Q.C. Sun, Y.Q. Hou, Q.C. Tan and Z.Y. Xu

Fast and robust extraction of the centre of a structured light stripe from the image is the key to high precision measurement in laser triangulation measurement. In this paper a new algorithm for extracting light stripe centre is given and the algorithm can be divided into three steps. First, the edge points of light stripe are detected in pixel-level by the Sobel operator. Second, the grey gradient direction of the edge points are calculated as the normal direction of light stripe curve, and the cross-section of light stripe can be obtained along the normal direction. Finally, a closed solution for extracting light stripe centre is given based on spatial moment theory, and the sub-pixel coordinates of light stripe centre can be obtained in all cross-sections.The experimental result demonstrates that this moment-based detection algorithm is more robustness against the noise, and its run time is much faster than the other methods. The above advantages indicate this algorithm is more suitable for on-line accurate detection.

Keywords: Laser triangulation measurement, light stripe, centre, Sobel operator, spatial moment, robustness, sub-pixel detection

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