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:
May. 26, 1998
Filed:
Aug. 15, 1995
Masaaki Okada, Toda, JP;
Canon Kabushiki Kaisha, Tokyo, JP;
Abstract
An image reading apparatus can perform shading correction with a simple arrangement. Prior to an original read operation, a prescanning operation is performed using a white reference original. Shading data is formed by a shading correction circuit and held in both an internal shading memory and a memory in a shading data confirming unit. The shading data confirming unit compares the data in both the memories to detect whether the data is destroyed. If the data is destroyed, permanent shading data is used. When the image is a halftone image, the prescanning operation is performed again to form shading data. Therefore, a conventionally used prescanning mechanism for the reference white ground can be omitted. At the same time, even when the shading data is destroyed by an abnormal voltage or the like, processing can be normally performed.