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:
Jul. 14, 1992
Filed:
Feb. 20, 1990
Tatsuya Nagata, Ibaraki, JP;
Michihiro Watanabe, Tsuchiura, JP;
Takehiko Yamada, Chigasaki, JP;
Eiichi Hara, Chigasaki, JP;
Hitachi, Ltd., Tokyo, JP;
Abstract
A digital signal is provided by correcting image signal distortions contained in an image signal outputted from an elongated direct contact type image sensor in an image reader such as a facsimile device, which image sensor reads patterns on a document in contact with the document. The image signal distortions of the sensor output are so-called shading distortions due to sensitivity distribution of sensor elements or distribution of light from light sources onto the document. Signal distortions are corrected from both a white signal outputted from the sensor when a white document is read and a black signal outputted when a black document is read. The white signal and the black signal are stored and reproduced to generate a reference signal which is obtained by dividing the voltage range across both the signals at a predetermined ratio. The digital signal is obtained by comparing the sensor output with the reference signal. If necessary, a pseudo-black signal may be produced by dividing the voltage of the white signal.