Optical coordinate system input device

Details Optical coordinate system input device Optical coordinate system input device

1987-09-29

1989-02-21

Westin, Edward P.

Radiant energy

Photocells; circuits and apparatus

Optical or pre-photocell system

340712, 341 5, 341 13, G01V 904

Patent

active

048067490

ABSTRACT:
An optical coordinate system input device including multiple opposed pairs of light emitting elements and light receptor elements which are sequentially selectively activated via a switching circuit, a variable impedance circuit connected in series with the light receptor elements to form a voltage divider, and an impedance detection circuit for detecting a low impedance of the light receptor elements caused by ambient light, wherein a detection signal from the impedance detection circuit lowers the impedance of the variable impedance circuit to increase the sensitivity of the input device to small changes in impedance of said light receptor elements upon detection of a light signal, emitted by said light emitting elements, by said light receptor elements in presence of strong ambient light.

REFERENCES:
patent: 4243879 (1981-01-01), Carroll et al.
patent: 4313109 (1982-01-01), Funk et al.
patent: 4645920 (1987-02-01), Carroll et al.
patent: 4652741 (1987-03-01), Golborne
patent: 4725726 (1988-02-01), Hasegawa et al.

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