| 摘要 |
PROBLEM TO BE SOLVED: To improve position detection precision of a scanning part of an image reader, which detects a reference position in a sub-scanning direction by detecting an image pattern for position detection irradiated with light by a light source, while reducing an increase in processing time. SOLUTION: The image reader comprises: a cold-cathode tube 531 which irradiates a document with light; the scanning unit 53 which acquires reflected light from the document while moving it in the sub-scanning direction; a reference display plate 57 where a black pattern 571 and a white pattern 572 whose positions in the sub-scanning direction are uniquely determined for an image in a main-scanning direction are formed; a main-scanning image acquisition control unit 812 which makes an imaging element acquire the image in the main-scanning direction from the reference display pale 57 by making a storage time longer than time when a document image is read; and a current position acquiring unit 813 which acquires current position information indicating the position of the scanning unit 53 in the sub-scanning direction from the image in the main-scanning direction based upon the correspondence relation to the sub-scanning-directional position of the image in the main scanning direction. COPYRIGHT: (C)2008,JPO&INPIT
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