An acoustic position sensing system for large scale interactive displays

We present a hybrid positioning and communication system for tracking interaction objects called ´pucks´ on the surface of a large LCD or plasma display. Pucks are smart sensor packages consisting of a microcontroller as well as a contact-type acoustic receiving transducer and an infrared or radio data link. A puck may take the form of a standalone interaction object, or the puck circuitry may be integrated into an existing object, such as a digital camera, cellphone, PDA, or other device. In this work we take advantage of the glass surface atop an LCD or plasma display as a communication and sensing medium, and launch 200 kHz Gaussian-shaped acoustic ranging pulses into that medium from transmitting transducers adhered to the corners of the glass. We present experimental results demonstrating millimeter-scale puck positioning accuracy over the entire surface of a 32-inch LCD, at an update rate of 100 Hz. We also demonstrate the scalability of this approach to much larger displays. In our first implementation, power consumption of each puck is 3 V at 12 mA during data transmission, 5 mA during positioning, and 50 muA when idle, yielding 6-8 hours of continuous tracking from a 90 mAH prismatic lithium polymer battery.