Abstract: Existing methods for calibrating multiple line structured light vision sensors often requires each structured light vision sensor to be locally calibrated before the global calibration of all vision sensors can be carried out. It is not only time consuming, but may also reduce the accuracy of the measurement system due to the structural change of individual vision sensors during the handling or assembling process after individual calibration. A method that can achieve simultaneously the local calibration of individual line structured light vision sensor and the global calibration of all vision sensors is presented. The two non-overlapping vision sensors are linked together through the 1D target, which is positioned in front of the two vision sensors for at least three times. Using the known distances between feature points on the 1D target and the cross-ratio invariance property, the image coordinates of the 1D target feature points and the intersection points of the 1D target and the structured light planes in the image coordinate frame of each vision sensor are computed, and the coordinate transformation between the two vision sensors is solved. Using the coordinate transformation, the spatial coordinates of the target feature points and the intersection points are computed in a global coordinate frame and the plane equation of structured light planes are computed by fitting the intersection points. The light plane equations and the coordinate transformation between the two vision sensors are optimized simultaneously by non-linear optimization. If there are more than two vision sensors, the calibration of multiple vision sensors may be achieved by the pair-ware. Experimental result shows that the RMS error of the proposed calibration is less than 0.14 mm.

Key words: Global calibration, Line structured light, Local calibration, Multiple vision sensor, Simultaneous calibration