Research On 3D Measuring System Of Denture Profile Based On Line Structured Light

3D reconstruction technology is an important research content in the field of computer image visualization.It has been widely used in reverse engineering,cultural relic protection,medical assistance,virtual reality,robot applications and other fields.The 3D reconstruction based on line structured light is a cross-cutting research area of computer graphics,image processing,optics and other technologies.Through the observation of the same object from the left and right two different perspectives at the same time and data complement,the purpose of restoring the 3D contour of the measured object.This thesis is a three-dimensional denture profile measurement system based on linear structured light.The tooth is placed on a rotating platform,which is rotated clockwise.The left and right cameras collect tooth pictures every two degrees.After computer processing,the three-dimensional reconstruction of the teeth is completed.The main research contents of this thesis are data acquisition and processing,calibration of rotating platforms and point cloud stitching.1)The data collection and processing section mainly introduces the process of data collection and the processing of data.The resolution of the camera used for data acquisition in this article is 10241280?dpi,and the effective field of view is 1820?mm.First,the noise collected in the image by the camera is removed by Gaussian filtering to ensure the accuracy of the reconstruction.Second,the filtered picture is thresholded by the maximum inter-class variance method to separate the foreground part from the background part of the picture.Last,the center of the fringe of the foreground part of the picture is extracted by the gray barycentric method as the pixel coordinates of the model.2)The rotation platform calibration is to calibrate the rotation center and tilt angle of the rotation platform.In this thesis,a rotation hybrid calibration method is proposed to calibrate the center of rotation.The points that meet the requirements are selected by the symmetrical method.And,it is used to fit the center of the circle by least squares.This method guarantees accurate circle center.The experimental comparative analysis proves that the calibration result of this method is stable and the calibration accuracy is 3.8%.The calibration process of the tilt angle of the rotating platform is to fit the calibration block data as a straight line,find the slope of the straight line,and obtain the tilt angle of the rotating platform by the slope.After calibrating the rotation center and tilt angle,it is necessary to perform de-tilt and rotation stitching on the collected point cloud data.De-tilt is to move the coordinate origin to the center of rotation and restore the point cloud to a state without tilt angle.Rotating stitching is mainly to unify the point clouds of each rotation angle into the same coordinate system and stitch the laser stripes from the world's three-dimensional coordinates into a tooth model.3)Point cloud stitching is the fusion of the point clouds obtained by the left and right cameras,so that the data of the left and right cameras compensate each other.It ensures the accuracy of reconstruction.Before point cloud stitching,in the case of ensuring the accuracy of the reconstruction model,the irrelevant points in the point cloud should be removed to speed up reconstruction.Then,the point cloud is rendered by Open GL,so that the 3D point cloud after stitching conforms to the real 3D scene.After completing this series of operations,the rendered model is evaluated to prove the stability and accuracy of the system in this thesis.