A Correlating Optical Motion Detector

Abstract

Here we describe an optical motion detector that uses integrated light sensors and analog and digital processing on the same chip. An image of an arbitrary scene or working surface is sensed by an array of photodiodes, stored, and correlated with the next image taken on the next cycle. The position of maximum correlation indicates the relative motion of the image during the time between samples. This peak is detected using mutual inhibition and is converted to digital signals that go off chip to indicate motion. This single chip motion detector has application in optical mouse systems. It overcomes certain limitations of present devices which require a special operating surface. Other potential uses are in automated vision systems and robotics. This motion detector could be used, for example, to track parts moving down an assembly line. We have built a one-dimensional motion detector and shown it to work in the laboratory. The design of a two-dimensional version is in progress.

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