Vision-based3D Reconstruction Theory And Application Of The Spatial Circle

The spatial circle widely exists among many kinds of objects and the3Dreconstruction theory of the spatial circle is a hot spot of computer vision research whichis adopted in camera calibration, object pose estimation and geometric measurement, etc.Generally, this reconstruction research is divided into two problems, one uses a singleimage of a radius-known circle to recover its normal vector and center position; the otherone uses two images of a radius-unknown circle to recover its normal vector, centerposition and radius.These two problems are studied in this thesis, regarding the radius-known problem,the normal vector of the spatial circle is obtained by applying an algebraic approach, it isdeduced that a diameter of the projected ellipse is the projection of a diameter of thespatial circle. With a calculation of this special diameter, the center position of the spatialcircle is given by the midpoint of this diameter and the mode long is the diameter.Meanwhile, the viewpoint-center line intersects the image plane at the projected center ofthe center of the spatial circle. Regarding the radius-unknown problem, the normal vectorsin the left and right camera coordinate system are calculated and a match between them isadopted to get the real normal vector and the real projected centers also. Thus, the line ofleft viewpoint-left projected center intersects the line of right viewpoint-right projectedcenter at the center of the spatial circle. Finally, the radius is calculated.By adopting the3D reconstruction theory of the spatial circle into the object poseestimation, a monocular vision-based object pose estimation method is proposed byreconstructing two radius-known coplanar circles which are attached to the object. Byadopting this object pose estimation method to tool setting of machine tool, a calibrationmethod of the pose between the machine coordinate system and the camera coordinatesystem is established. Then, the machine coordinate of some feature points can beobtained in a convenient way. Finally, the workpiece-machine tool pose matrix is alsocalculated.Experiments on the3D reconstruction of the spatial circle and tool setting of machinetool show the validity of these established theories.