A closed-form single-pose calibration method for the camera–projector system

To improve the calibration efficiency of the structured light stereo vision system, a closed-form single-pose calibration method is proposed. Previous works calibrate the structured light stereo vision system via the planar-based method since the world coordinates of the projected pixels are easy to find. But the disadvantage of these methods is that multiple poses are required, so that the mechanical movement is necessary in these calibration methods. In this paper, the inherent geometry between the spheres and their image is exploited deeply. Thus, a sphere-based calibration method is proposed. The proposed method first calibrates the camera from the image of the absolute conic through an improved algorithm. Then, the three-dimensional coordinates of the projected pixels are found via the inherent geometrical relation. Next, the projector is calibrated using the direct linear method. Finally, the distortion of the projector is found through the nonlinear optimization method with an improved updating direction. Experiments demonstrate that not only the calibration efficiency is improved, but also the calibration accuracy is improved.