Self-tracker: a Smart Optica.i Sensor on Silicon /lt~l- Thomas Gary Bishop. Self-tracker: a Smart Optical Sensor on Silicon

Ill A new system for real-time, three-dimensional computer input is described. The system will use a cluster of identical custom integrated circuits with outward looking lenses as an optical sensing device. Each custom integrated sensor chip measures and reports the shift in its one-dimensional imo.ge of the stationary room environment. These shifts will be processed by a separate general-purpose computer to extract the three-dimensional motion of the cluster. The expected advantages of this new approach are unrestricted user motion, large operating environments, capability for simultaneous tracking of several users, passive tracking with no moving parts, and freedom from electromagnetic interference. The fundamental concept for the design of the sensor chips relies on a cyclic relationship between speed and simplicity. If the frame rate is fast, the changes from image to image will be small. Small changes can be tracked with a simple algorithm. This simple algorithm can be implemented with small circuitry. The small circuitry lets a single chip hold the complete sensor, both imaging and image processing. Such implementation allows each sensor to be fast because all high-bandwidth communication is done on-chip. This cyclic relationship can spiral up as the design is iterated, with faster and simpler operation, or down, with slower and more complex operation. The system design sequence described here has been spiraling up. System, sensor, algorithm, and processor designs have each had several iterations. Most recently, a prototype sensor chip has been designed, fabricated, and tested. The prototype includes a one-dimensional camera and circuitry for image tracking that operates at 1000 to 4000 frames per second in ordinary room light. As part of this research, photosensors that operate at millisecond rates in ordinary room light with modest lenses have been designed, tested and fabricated on standard digital nMOS lines. They may be useful for designers of other integrated optical sensors.

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