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:
Mar. 06, 1990
Filed:
Dec. 17, 1987
Ikuo Sobue, Kawasaki, JP;
Canon Kabushiki Kaisha, Tokyo, JP;
Abstract
A document reading apparatus incorporating shading correction features has an illumination device for illuminating a document. Drive components move the document relative to the illumination device. Image pickup circuitry converts the image of the document irradiated by the illumination device into an electrical signal. A first stationary reference member is disposed on a reverse side with respect to the document and provides a first reference light to the image pickup circuitry when irradiated by the illumination device. A second stationary reference member is disposed on a front side with respect to the document and provides a second reference light to the image pickup circuitry when irradiated by the illumination device. Control circuitry corrects the electrical signal of the document image from the pickup circuitry in accordance with one of the first and second reference lights picked up by the pickup circuitry.