针对手持靶标视觉坐标测量的广泛应用,提出一种平面靶标测头中心现场两步标定的方法。通过两组不同位姿的靶标图像建立靶标坐标系与摄像机坐标系之间的转换关系,利用第一组靶标平行于成像面不同倾角的图像信息,根据位置不变原理建立目标优化函数,通过Levenberg-Marquardt算法求解出靶标坐标系下测头中心在x、y方向最优化的修正值;再依据第二组靶标相对于摄像机成像面不同倾角的图像信息求解出测头中心在z方向的误差。通过仿真和实验验证了方法的正确性,实验结果表明,测头中心坐标在x、y、z方向的重复性精度分别达到0.077,0.035,0.140 mm,有效地解决了手持平面靶标测头中心现场标定的难题。

Aiming at the wide application of the visual coordinate measurement of the handheld target, an on-site two-step calibration method for the probe tip center of the planar target is proposed. The conversion relationship between the target coordinate system and the camera coordinate system is established by two sets of target images in different positions. Based on the position invariant principle, the object optimal function is established according to the image information of the first set target parallel to imaging plane with different angles. The Levenberg-Marquardt algorithm is employed to solve the optimal corrected value of the probe tip center along x and y directions in target coordinate. The error of the probe tip center along z direction is solved by using the image information of the second set target relative to the imaging plane of the camera with different angles. The correctness of the method is verified by simulation and experiment. The experiment results show that the repeatability accuracy of the probe tip center coordinates in x, y and z direction can reach 0.077 mm, 0.035 mm and 0.140 mm, respectively, which can effectively solve the problem of on-site calibration of the probe tip center of the handheld planar target.