采用虚拟标准平面标定相位测量轮廓术系统

Calibration of PMP system using virtual planes

为了标定相位测量轮廓术系统中相位-高度映射关系,引入了虚拟标准平面。基于投影是摄像的逆过程这一事实,从摄像机模型出发,使用统一的数学模型和平面靶标来标定出摄像机和投影仪的内部、外部参量。再由双目视觉中的立体标定方法得出测量系统的几何结构。最后根据标定得到的参量,在测量体积内设置参考平面并计算得出参考平面及不同高度上平行于参考平面的各标准平面上的相位分布。利用最小二乘法求解相位-高度映射方程系数。实验测量的标准差达到0.046mm。对间距为1.00mm的台阶模型进行测量,实际测得间距为0.99mm。结果表明,该方法可行,简化了相位测量轮廓术系统标定过程。

In order to calibrate the coefficients of phase-height mapping equation in phase measuring profilometry（PMP） systems, virtual planes were introduced. Firstly, the intrinsic and extrinsic parameters of camera and projector were calibrated with uniform mathematics model and processing method, as a projector could be considered as a camera working in reverse. Secondly, geometric construction of the measurement system was calibrated by means of stereovision method. Thirdly, a reference plane was defined in the measuring volume. Phase distribution of reference plan and parallel standard planes at different distances from the reference plan was worked out according to the calibrated parameters. Finally, the coefficients of phase-height mapping equation were obtained with least square method. The standard deviation of measurement reached 0. 046mm. A model consists of four steps with space of 1.00mm was also measured. The measured average height between neighbor steps was 0.99mm. The experiment results reveal that the method is feasible. The procedure of system calibration is simplified.