Photocopying – Projection printing and copying cameras – Illumination systems or details
Patent
1977-02-02
1978-11-07
Griffin, Donald
Photocopying
Projection printing and copying cameras
Illumination systems or details
355 8, G03G 1528, G03B 2774
Patent
active
041242955
ABSTRACT:
An automatic background brightness control for document copiers of the type using automatic feeders for advancing original documents along a transport path to an imaging platen at which the documents are copied. As the feeder advances a document to the imaging platen, one or more light sources disposed at spaced locations across the transport path direct scanning beams onto the indicia-bearing side of the document. Photodetectors sense the light reflected from the scanned portions of the document to provide signals indicating the reflectance of the scanned portions. A signal-processing circuit responsive to the reflectance signals generates a background brightness control signal representing the maximum reflectance sensed by any of the detectors. The background brightness control signal regulates the intensity of the exposure lamp of the copier when the document reaches the imaging platen. In one alternative embodiment, the background brightness control signal regulates the width of an optical slit disposed adjacent to the photosensitive surface. In another alternative embodiment, the background brightness control signal regulates the effective aperture of the focusing lens.
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Griffin Donald
Savin Business Machines Corporation
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