Patent ID: 7649656

Claim:
An image reading device comprising: a transparent member; a conveyance unit that conveys an original document to the transparent member; a reading unit that reads via the transparent member an image of the original document being conveyed on the transparent member at multiple reading positions that exist with a prescribed distance therebetween along an original document conveyance direction; an output unit that outputs signals for different color components corresponding to each of the reading positions; a transparent member moving unit that moves the transparent member in a prescribed direction such that the original document slides over the transparent member while being conveyed to the reading positions during image reading; and a detector that detects noise components caused by foreign particles on the transparent member based on the output signals from the output unit; wherein said reading unit reads the image of the original document on pixel-by-pixel basis and the detector detects whether or not an edge component is included in a color component signal for each pixel and detects the existence of noise components based on the detection results; wherein when the number of multiple positions is ‘n’ and the number of different colors is ‘n’(‘n’ being an integer that equals or exceeds 2), and when the color component signals for the target pixel and (n−1) reference pixels located within prescribed distances from the target pixel along the secondary scanning direction are analyzed in sequence starting with the target pixel, if the sequence of colors including an edge component matches the sequence of colors corresponding to the reading positions along the direction of movement of the transparent member, said detector determines that a noise component is included in each pixel's color component signal including an edge component.