Proposal of calibration method for 3-D digestive endoscope using grid active stereo

Calibration for calculating the external parameter of camera-projector system is important, to make high-precision 3-D measurement by 3-D endoscope using the grid active stereo. In this paper, we propose a new calibration method with a sphere calibration object in a geometrically flexible camera-projector system, and we examine the validity of the proposed method. As the result of comparing using conventional calibration with a plane calibration object, it is clarified that the proposed method resolves the scaling imprecision, that is a problem of the conventional method. Thus, the proposed method has higher potential of measurement accuracy. In addition, it is the advantage of the proposed method that precision estimation of calibration parameters with a low number of input images is possible.