2-D Input Device Based on Frustrated Total Internal Reflection


Touch screen systems allow users to interact directly with content displayed on a 2-D surface. However, current systems have severe limitations in usability because they do not preserve the familiar mechanical response of traditional writing and drawing tools. Furthermore, current touch-screen technologies can often require extensive modifications to the drawing/writing substrate, which make them expensive and impractical for large drawing surfaces or entire desktops. We are developing a touch-screen system based on an effect called Frustrated Total Internal Reflection (FTIR). This technique involves coupling light into a pane of glass and then detecting contact to the glass by measuring the absorption of the light by the object in contact, using a linear array of photodetectors adhered to the glass. An LCD screen or other video display can then be fitted behind the glass to produce an appropriate response. All hardware is inside the glass�there is no need to mount anything on the side where the interaction takes place. We believe this system will be a practical and economical way to detect contact with brushes, felt pens, and fingers across large interactive surfaces.