A new extrinsic calibration method of a display-camera system that the display is not in the direct view of the camera is proposed. An annular mirror is used so that the camera can capture the virtual image of the display. The position of the mirror can be obtained after outer circle is detected. The position parameters are determined uniquely by putting two orthogonal lines in the background and optimized by re-projecting the inner circle to the image plane. The display pixels are encoded using gray code and its imaging position in the mirror can be obtained by solving the PnP problem. Finally, the real extrinsic parameters between the camera and the display are obtained according to the mirror imaging principle. Compared with other existing methods, our approach is simple and fully automatic without any manual intervention. The mirror only needs to be fixed at one position and the degenerate case using a common planar mirror is avoided. Both simulation and real experiments validate our approach.

This work was published on JOURNAL OF INFORMATION SCIENCE AND ENGINEERING,2016,32(4):1079-1095.titled  Automatic Display-Camera Extrinsic Calibration Method Using an Annular Mirror.