Method and apparatus for self-biasing a light beam obstacle detector with a bias light
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United States of America Patent
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Feb 15, 1994
Grant Date -
N/A
app pub date -
Dec 4, 1992
filing date -
Dec 4, 1992
priority date (Note) -
Expired
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Abstract
A modulated light beam obstacle detector for use as a safety mechanism in an automatic closure operator which must operate in varying ambient light conditions. If the obstacle detector senses the interruption of the light beam, the motion of the door is arrested or reversed. The obstacle detector uses an auxiliary light source connected in a feedback circuit to maintain a constant background illumination on the light detector and thereby hold the light detector in conduction at all times. In this manner, the presence of the light beam can be sensed regardless of the ambient light conditions.
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