A multi-touch platform based on four corner cameras and methods for accurately locating contact points

This paper presents a low-cost and scalable multi-touch platform which uses four cameras to reduce occlusion. Three methods are provided for locating contact points on this platform, including the lookup table, vanishing point, and 3D reconstruction. With each of these methods, respectively, the contact point is located using the projection center and the reference point, the projection center and the vanishing point, and the back-projected rays of epipolar geometry. If the four directing lines of a contact point intersect, the contact point is considered to be real; if the lines do not intersect, the point is rejected. Experimental results indicate that all three methods are capable of locating contact points even under conditions of occlusion. The lookup table and vanishing point methods are, respectively, best suited to small and large platforms, while the accuracy of 3D reconstruction method has been found to be sensitive to the physical setup. The approach proposed here can be directly installed on existing display platforms and thus should be of practical applicability in the near future.