IMAGE READER, METHOD FOR DETECTING FOREIGN MATTER ON IMAGE-READING GLASS FACE THEREOF, AND FOREIGN MATTER DETECTION PROGRAM

摘要

PROBLEM TO BE SOLVED: To provide an image reader capable of accurately determining whether or not a read image is a noise image including a foreign matter, such as dust or dirt, left on an image-reading glass face on the basis of the read image, for detecting the presence of the foreign matter exactly.SOLUTION: A plurality of light-receiving sensors 1 to N are arranged so that at least two or more of them read an identical region of an image-reading glass face 201 and a document-feeding face 202 in a superposing manner. Sizes in a main scanning direction and a sub scanning direction are determined so as to determine a degree of coincidence of a superposing portion of a first image and a second image obtained by adjacent ones of the light-receiving sensors 1 to N. At least one of an image 400 of a first region of the first image in the determined size and an image 500 of a second region of the second image in the determined size is shifted and superposed so as to get close to each other, the degree of coincidence in accordance with an amount of shifting is calculated, and it is determined whether or not images having different focal depths are present. When it is determined that such images are present, each of the images having the different focal depths is continuously detected in a feeding direction so as to detect foreign matters on the image-reading glass face.SELECTED DRAWING: Figure 7