The 3D scanning of a freeform structure relies on the laser probe and the localization system. The localization system, determining the effect of the point cloud reconstruction, will generate positioning errors when the laser probe works in complex paths with a fast speed. To reduce the errors, in this paper, a linear laser scanning measurement method is proposed based on binocular vision calibration. A simple and effective eight-point positioning marker attached to the scanner is proposed to complete the positioning and tracking procedure. Based on this, the method of marked point detection based on image moment and the principle of global coordinate system calibration are introduced in detail. According to the invariance principle of space distance, the corresponding points matching method between different coordinate systems is designed. The experimental results show that the binocular vision system can complete localization under different light intensities and complex environments, and that the repeated translation error of the binocular vision system is less than 0.22 mm, while the rotation error is less than 0.15°. The repeated error of the measurement system is less than 0.36 mm, which can meet the requirements of the 3D shape measurement of the complex workpiece.
With the continuous development of domestic and foreign manufacturing industries, there are limitations in the omnidirectional three-dimensional measurement of large parts. In order to improve the 3D measurement range, speed, and accuracy of single-line lasers, a combined measurement method based on binocular vision positioning technology is proposed. First, the circular markers are pasted around the line laser sensor, and a virtual intermediate coordinate system is constructed based on the centers of the marked points. Secondly, a feature point energy matching algorithm is used to complete the corresponding points matching of the circular markers, and the position of the circular markers is solved based on the SVD method. Third, the relative pose relationship between the virtual intermediate coordinate system and the line laser sensor coordinate system is completed based on the hand-eye calibration model. Fourth, combined with the circular markers pose and relative pose, the local point cloud data of the line laser is unified into the global coordinate system to realize point cloud splicing. The experimental results show that the average measurement error of the measurement system is less than 0.23 mm, which basically meets the requirements of general shape measurement.
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