Ambient light rejecting quad photodiode sensor
First Claim
1. A photodiode array for detecting a projected image in the presence of ambient light, comprising at least three image sensing photodiodes connected in parallel with like polarity and arranged at right angles, and at least three further photodiodes connected in parallel with and with reverse polarity to respective ones of said image sensing photodiodes for compensating the effects of said ambient light on said image sensing diodes.
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Accused Products
Abstract
An ambient light rejecting quad photodiode sensor having compensation diodes connected with reverse polarity to respective quadrant photodiodes within the sensor, the compensation diodes being located outside of the area of illumination. By direct connection of compensation diodes in reverse polarity to each quadrant of the quad photodiodes, a large boost in signal to noise ratio is achieved for eliminating the effects of ambient room light as well as sensor dark current.
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Citations
13 Claims
- 1. A photodiode array for detecting a projected image in the presence of ambient light, comprising at least three image sensing photodiodes connected in parallel with like polarity and arranged at right angles, and at least three further photodiodes connected in parallel with and with reverse polarity to respective ones of said image sensing photodiodes for compensating the effects of said ambient light on said image sensing diodes.
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7. A circuit for detecting mis-registration of a projected image in a video system, comprising:
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(a) a photodiode sensor divided into four quadrants adapted to be illuminated by said projected image and in response generating four photovoltaic potentials corresponding to respective portions of said projected image incident on respective quadrants of said sensor; (b) each said quadrant of said sensor having a compensation photodiode connected with reverse polarity thereto for cancelling the effects of ambient light on said quadrant; (c) means for converting said four photovoltaic potentials to respective digital values; and (d) means for detecting inequality of said digital values and in response indicating detection of mis-registration of said projected image. - View Dependent Claims (8, 9, 10, 11, 12, 13)
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Specification