Polarized light vision pose measurement method by fusing the constraints provided between control points for hand-eye calibration

Abstract

The accuracy of hand-eye calibration is determined by the pose measurement accuracy of the calibration target. In the hand-eye calibration of industrial robots, the pose measurement can be performed based on the polarization information to filter out high-brightness areas of the image, optimize image processing, and increase effective control points. However, it is hard to decide on an adequate polarization angle. An inadequate polarization angle will affect the image contrast and ultimately affect the extraction accuracy of the 2D projections of the control points. In addition, the existing non-iterative pose measurement methods only consider the constraints provided by the single control points. The constraints provided between the control points are not in consideration. This results in reduced pose measurement accuracy in noisy environments. Aiming at the above problems, a polarized light vision pose measurement method by fusing the constraints provided between control points for hand-eye calibration is proposed: the adequate polarization angle was determined based on the cross-ratio invariance, and the target image collected under the adequate polarization angle was used for subsequent pose measurement to reduce the high-brightness areas on the premise of ensuring the image contrast. We introduced the plane created by two control points and the optical center to represent the constraints provided between these two control points. In this way, the constraints provided by any two control points can be fused with the constraints provided by the single control points to solve the pose non-iteratively. Compared to other current methods, there are more significant increases in our method's pose measurement accuracy and stability. The experimental results show that the angle measurement error is less than 0.052° over the measuring range of -60°-+60°, and the displacement measurement error is less than 0.01 mm over the measuring range of 0-20 mm.