Calibration Of The Rotation Axis Of Three-Dimensional Scanning System For Line-structure Light

In the existing three dimensional scanning methods, light-stripe three-dimensional laser scanning has the advantages of high speed, high efficiency and high precision. But to get the complete contour information of the object surface, it is needed to add translational scanning or rotational scanning on the basis of the light-stripe three-dimensional laser scanning. And rotational scanning is more convenient, accurate calibration of the rotation axis can improve the accuracy of the scanning results and the effect of three-dimensional reconstruction of objects. A flexible calibration method is proposed in this paper. A plane calibration board with tessellated pattern is placed on the rotating stage, the calibration board was recorded at every point when the stage was rotated. Then the coordinates in the camera coordinate system of these character points on the target are calculated by processing these pictures. At last, the axis equation of the working stage is acquired by linear fitting with the circle centers which were gotten by circle fitting with the character points. The main study content and conclusions are as follows:(1) Camera calibration: This paper applies checkerboard plane calibration method to calibrate the internal and external parameters of camera. Shooting multiple images from different perspectives of the checkerboard, and according to the relationship between the point of the object in the three-dimensional space and the image plane, we can get a number of expressions, and then the internal and external parameters of the camera can be obtained.(2) The rotation axis calibration: After the camera calibration, according to the internal as well as external parameters of camera obtained by camera calibration and the transformational relation of coordinate system, we can get the three-dimensional coordinates of each corner point in the camera coordinate system. For each corner point, when they are in different positions, the three-dimensional coordinates can be got, and fitting the spatial circle to get the center coordinates, then fitting the spatial linear. This linear equation is the rotation axis we want to get.In this paper, the calibration of camera and the rotation axis of three-dimensional scanning system for line-structure light are completed. We used the re-projection method to evaluate the camera calibration results. The results show that the average error between detected coordinates and the coordinates got by re-projection is 0.273841 pixels, and more than 60% of the points are coincided, the accuracy can satisfy experimental request. The calibration of the rotation axis includes two parts, the spatial circle fitting and the spatial line fitting. The mean square deviation of the spatial circle fitting results is 0.0357, and the mean square deviation of the spatial line fitting results is 0.0293. The results can be used in the following experiments, and lay a good foundation for the high accuracy of three-dimensional scanning.