Comparison of calibration methods for the multi-touch system with four collaborative cameras

The multi-touch system with four collaborative cameras resolves the occlusion problem of multiple touch points by fitting the four directional lines of the points. This paper suggests three methods to build the directional line: the look-up table, the vanishing point, and the stereo calibration method. The look-up table method firstly specifies a set of calibration points along the rectangle frame of the interaction region, then finds the relevant calibration point by interpolation, and finally builds the line with the optical center of the camera and the calibration point; the vanishing point method builds the line with the vanishing point of the touch point and the optical center; the stereo calibration method builds the line with the epipolar geometry back projection radial. Experimental results show that the look-up table method is suitable for smaller platforms, while the vanishing point method fits the larger. The stereo calibration method, however, needs to improve its precision.