The Optical Mouse: Early Biomimetic Embedded Vision

The 1980 Xerox optical mouse invention, and subsequent product, was a successful deployment of embedded vision, as well as of the Mead–Conway VLSI design methodology that we developed at Xerox PARC in the late 1970s. The design incorporated an interpretation of visual lateral inhibition, essentially mimicking biology to achieve a wide dynamic range, or light-level-independent operation. Conceived in the context of a research group developing VLSI design methodologies, the optical mouse chip represented an approach to self-timed semi-digital design, with the analog image-sensing nodes connecting directly to otherwise digital logic using a switch-network methodology. Using only a few hundred gates and pass transistors in 5-micron nMOS technology, the optical mouse chip tracked the motion of light dots in its field of view, and reported motion with a pair of 2-bit Gray codes for x and y relative position—just like the mechanical mice of the time. Besides the chip, the only other electronic components in the mouse were the LED illuminators. Fig. 1 The Xerox optical mouse chip in its injectionmolded dual-inline package (DIP) of clear plastic, with pins stuck into a conductive packaging foam. The bond wires connecting the chip’s pads to the lead frame are (barely) visible. Richard F. Lyon Google Inc., Mountain View CA, e-mail: [email protected]