3D reconstruction and positioning for spheres based on RGBD camera
                                                   FENG Chun, HUA Xing, WANG Shulei, YIN Feihong, JIANG Wei
(Department of Mechanical and Vehicular Engineering, Changzhou Institute of Technology, Changzhou 213032, China)

Abstract: Aiming at single and multiple sphere recognition and localization problems, a method of threedimensional reconstruction using an RGBD camera was employed. The calibration of RGBD camera, the registration of depth image and color image, and the generation of color 3D point cloud were studied. A positioning method based on threshold segmentation combined with random sampling consistency algorithm was proposed. The method of color threshold segmentation and the depth threshold segmentation method was used to realize the background segmentation, and the point cloud data of the whole sphere region was obtained. The Euclidean point cloud segmentation method was applied to divide the whole sphere region into independent sphere point clouds, and the threshold segmentation method based on surface normal was used for separating the point cloud of the contact sphere. The random sampling consistency algorithm was used to calculate the parameters of each sphere separately, and get the spherical coordinates, radius and depth information of the sphere. The results indicate that the method has good realtime and positioning accuracy under different illumination conditions. In the range of 0.5 m～1.5 m depth, the average radius error of the sphere with a radius of 30 mm is 4 mm, and the spherical coordinates error at x, y and z direction is 2.3 mm, 4.5 mm, 3.7 mm in average. Meanwhile single frame image average processing time is about 1 s.

Key words: RGBD camera; 3D reconstruction; recognition; positioning; point cloud segmentation