Global calibration of multi-vision sensor based on one dimensional target

Based on the invariance of cross-ratio and the collinear property of all points for one dimensional target, a global calibration method of multi-vision sensor system is proposed. The global coordinate frame is constructed based on the coordinate frame of one of the vision sensors, which is called the base vision sensor. The one dimensional target is positioned arbitrarily for at least twice in front of both the base sensor and the sensor to be calibrated. For each vision sensor, the image coordinates of the target feature points out of the view field are computed utilizing the image coordinates of at least three feature points captured by the vision sensor according to the invariance of cross-ratio. A transformation matrix from the coordinate frame of the sensors to be calibrated to that of the base sensor is solved by considering the distance restraint between target points and optimized solution is obtained by non-linear optimization method. The global calibration of multi-vision sensor system is realized by pair-wise calibration between the base vision sensor and each of the vision sensors to be calibrated. Experiment results show that proposed method can do calibration without anyhigh-accuracy 3D measuring equipment, it is simple, flexible and applicable in various situations. Calibration result shows that the error of global calibration method is 0.041 mm.