Facsimile and static presentation processing – Facsimile – Specific signal processing circuitry
Patent
1990-12-21
1993-09-28
Coles, Sr., Edward L.
Facsimile and static presentation processing
Facsimile
Specific signal processing circuitry
358464, 358471, 358475, H04N 140
Patent
active
052490688
ABSTRACT:
An image reading apparatus having a line sensor for supplying an image signal in accordance with a brightness of a specified region of an original document along a main scan line, the line sensor having a plurality of photoelectric conversion elements aligned along a main scan line. The image reading apparatus comprises a sampling part for sampling and holding a level of a reference signal initially outputted by the line sensor when a reference board is scanned, a correction part for calculating a correction quantity according to a level of a signal outputted by the photoelectric conversion elements when the specified region of the original document is scanned, a subtraction part for subtracting the correction quantity from the level of the reference signal when the reference board is scanned, to supply a corrected reference signal according to the brightness of the specified region of the original document, and a normalization part for normalizing a level of an image signal outputted by the photoelectric conversion elements when the original document is scanned, based on a level of the corrected reference signal from the subtraction part.
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Coles Sr. Edward L.
Lee Fan
Ricoh & Company, Ltd.
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