视觉引导激光跟踪测量系统的Cayley变换校准方法

对于一台激光跟踪仪对多个测量点进行测量的问题,提出了一种视觉引导激光跟踪测量方法。摄像机固定于激光跟踪仪顶部,随之旋转对测量范围内激光跟踪仪反射器进行定位,引导激光跟踪仪激光投射到反射器上。标定摄像机与激光跟踪仪相对姿态,用平面圆孔靶标。激光跟踪仪和摄像机同时测量圆孔靶标,将两个坐标系下对应三维点数组进行均值化处理,变为两个坐标系下对应的向量组,向量组之间的转换关系,即激光跟踪仪与摄像机之间的旋转矩阵。再根据两坐标系下对应的任一点的三维坐标,求解两坐标系的平移矢量。此标定算法把对两个坐标系之间的旋转矩阵的求解,通过Cayley变换,转换为对与转换矩阵相对应的三维向量的求解,求解过程简单稳定。实验结果表明,靶标摆放50次,测量误差小于1 mm。把校准结果应用到实际测量中,激光跟踪仪可快速准确地将激光束投射到反射球中。此方法操作简单,稳定性强,具有很高的实用价值。

Calibration method for visual-guided laser tracker measurement system based on the Cayley transformation

As for using just one laser tracker to measure several points, a new method of visual-guided laser tracking was presented. A camera was set on the top of the laser tracker, and rotates around the laser tracker's Z axis. When measuring, the camera rotated a single revolution with the laser tracker, and captured the positions of all the laser interferometers. The coordinates of the positions in the camera frame can be converted to the laser tracker frame, and then the laser designator projected a laser sheet to the laser interferometers. A planar round hole target was used, and the center of the holes were measured simultaneously by the camera and the laser tracker. The corresponding coordinates in the two frames which were processed using mean method becomes the corresponding vectors in the two frames. The translation of the two group vectors is the rotation matrix of the two frames. Using Cayley transformation, the rotation matrix of the two frames can be calculated, and then the whole relationship between the two frames can be obtained by using any two corresponding coordinates. The advances of the algorithm are the solving process is simple and the results are stable. Simulation is shown that, when the number of the target placing is more than 50, the influence of the image noise is stable, and the measuring error is less than 1 mm. The proposed method is simple, has strong stability, and has very high practical value.