The patent badge is an abbreviated version of the USPTO patent document. The patent badge does contain a link to the full patent document.
The patent badge is an abbreviated version of the USPTO patent document. The patent badge covers the following: Patent number, Date patent was issued, Date patent was filed, Title of the patent, Applicant, Inventor, Assignee, Attorney firm, Primary examiner, Assistant examiner, CPCs, and Abstract. The patent badge does contain a link to the full patent document (in Adobe Acrobat format, aka pdf). To download or print any patent click here.
Patent No.:
Date of Patent:
Sep. 28, 1993
Filed:
Dec. 21, 1990
Osamu Takase, Yokohama, JP;
Ricoh Company, Ltd., Tokyo, JP;
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.