The calibration for the optical probe of vision measurement system

In order to reduce the impact of the coordinate precision of measuring tip in the optical probe coordinate system on the accuracy of vision measurement system based on optical probe, the paper presents the calibration method for the optical probe, which subjects to the constraint that the distance from the measuring tip to the origin of the optical probe coordinate system is constant. By minimizing the error of each measurement of the distance, the method calibrates the three-dimensional coordinates of the measuring tip in the optical probe coordinate system. During the process of calibrating, firstly, the coordinates of the feature points on the optical probe in the spatial coordinate system are obtained with the feature point images using the stereo vision reconstruction by minimizing the projection distance based on the common perpendicular constraint. Then, with these coordinates, the transformation between the optical probe coordinate system and the spatial coordinate system can be got using unit quaternion. Finally, based on the transformation, the measuring tip coordinate is calibrated by minimizing the estimated error of the distance from the measuring tip to the coordinate origin. Experiments show that the method can rapidly and effectively on-line calibrate the measuring tip, the calibration precision of xyz directions can reach 0.03 mm, respectively, and the proposed method reduces the impact of the measuring tip coordinate on the vision measurement accuracy.