Patent ID: 7518760
Filing Date: 2009-04-14
Classification: H04N

Abstract:
1. An image reading apparatus comprising: a book platen on which an original is placed; a sheet-through platen onto which a plurality of originals placed on an original table are conveyed sheet by sheet by a conveyor; a scanner disposed beneath said book platen and said sheet-through platen and configured to move in a sub scanning direction, beneath said book platen in order to read an original placed on said book platen, and configured to be positioned beneath said sheet-through platen in order to read an original that is conveyed onto said sheet-through platen; a white reference plate for providing shading correction data; and a dirt detection plate disposed facing said sheet-through platen, which is read by said scanner when no original is present on said sheet-through platen to provide detection data for detecting the presence of dirt on said sheet-through platen; said image reading apparatus performing original reading using either a book system in which an image of the original placed on said book platen is read by having said scanner move to scan said original, or a sheet-through system in which said scanner is moved to a sheet-through reading position beneath said sheet-through platen, and an image of the original that is conveyed onto said sheet-through platen by said original conveying means is read by scanning said original using said scanner positioned in said sheet-through reading position, said white reference plate being read each time an original is read, regardless of the reading system that is used to read the original, whereupon image data obtained upon the reading of said original are subjected to shading correction based on shading correction data obtained when said white reference plate is read, wherein, when an image of an original is to be read using said sheet-through system, upon reception of an image reading request, said scanner is moved to a white reference plate reading position for reading said white reference plate, whereby said white reference plate is read by said scanner to obtain shading correction data, whereupon a sheet-through shading operation is performed to move said scanner to said sheet-through reading position beneath said sheet-through platen, whereupon a dirt detection operation for detecting the presence of dirt on said sheet-through platen is performed by having said scanner, having moved to said sheet-through reading position, read said dirt detection plate, whereupon said conveyor is driven to convey a single original from said original table onto said sheet-through platen in order to perform a sheet-through reading operation whereby an image of the original conveyed onto said sheet-through platen is read using said scanner positioned in said sheet-through reading position, and when an original is to be read using said sheet-through system in accordance with said image reading request, said sheet-through reading operation is begun by said conveyor after the elapse of a standby time T=Ts+Tl−Td, where Ts is a time required for said sheet-through shading operation, Tl is a time required for said dirt detection operation, and Td is a time required to convey the original from the start of said sheet-through reading operation by said conveyor to the time when a tip of the original reaches said sheet-through reading position, following reception of said image reading request.