Patent ID: 7616351

Claim:
An image reading device for reading an image of a document so conveyed as to move in a sub-scanning direction on one principal surface of a transparent plate at the other principal surface side of the transparent plate by a reflected light ray of a light source, comprising: a reference plate provided facing the one principal surface of the transparent plate, and extending in a main scanning direction; an abnormality determining portion for determining whether or not there is an abnormality in an image that is obtained by reading the reference plate without conveying a document; a reading position setting portion for changing a document reading position along the sub-scanning direction within a range allowing reading of the reference plate when the abnormality determining portion determines that there is an abnormality; an adjustment data storing portion for storing an adjustment data to compensate a difference in the reading sensitivity due to a different document image reading position; a sensitivity setting portion for adjusting the reading sensitivity in accordance with the document reading position based on the adjustment data; and a sheet type information reception portion for receiving information concerning a sheet type of a document, wherein: the adjustment data storing portion stores adjustment data respectively concerning a different sheet types, and the sensitivity setting portion adjusts the reading sensitivity based on the adjustment data corresponding to the sheet type specified by the information received by the sheet type information reception portion.