Importance

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Abstract

A method and device for sensing the presence and location of an object in a reference plane by directing light along a line perpendicular to the plane, defining a ring in that plane encircling said line of light, and sensing, by a change in the condition of the light, the presence of an object on the ring. In a first, non-contacting embodiment, light is directed along a line which is the axis of the ring and directed outwardly and focused at the ring. A circular detector coaxial with the light ring is positioned to sense intrusion onto that ring of an object, and by using a circular diode array detector, one can detect both the presence and location of that object on the ring. According to another contacting embodiment, a disc is placed in the reference plane with the light shining through an opening therein, the disc being movable in any direction in said reference plane. When an object touches the disc at any point and moves it, this changes the location of the aperture through which the light passes. This change is sensed to indicate an object on the ring.

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First Claim