Construction and evaluation of multi-touch screens using multiple cameras located on the side of the display

We applied a computer vision based method and developed multi-touch technology to be adopted in various display types. In the selected design, multiple cameras are placed on the side of the display with their optical axis parallel to the screen. The display edges opposite the cameras are illuminated and fingers are detected since they block the light in the camera images. The approach is scalable and can be used in a wide variety of displays. Due to self-occlusion of the touchpoints, it is challenging to relate camera measurements to tracked points. In this paper, we present our approach for tracking and managing multiple touchpoints in such camera set-ups. We describe the mathematical background for modeling and calibrating the cameras, the design of the extended Kalman filter for point tracking, and the logic for adding, updating and removing the touchpoints. We analyze the potential accuracy and robustness of the system using several simulations and present two different real-life implementations of the approach.