Patent ID: 7289249

Claim:
An image reading apparatus comprising: an image reading element which converts image information on an object to be read into an image signal; an illumination device which illuminates the object and generates light and shade corresponding to the image information; optical elements which convey the light and shade corresponding to the image information to the image reading element; a moving mechanism which moves the optical elements along the object at a predetermined speed; a driving device which provides the moving mechanism with power; a first reference level generation mechanism which is provided at a predetermined position on the moving mechanism and allows the image reading element to generate a first reference level output without reference to optical intensity of illumination light emitted from the illumination device; and a second reference level generation mechanism which generates reflected light when illuminated by the illumination device, said second reference level generation mechanism being located at a position where the second reference level generation mechanism prevents the reflected light from being transmitted to the image reading element, when the first reference level generation mechanism causes the image reading element to produce the first reference level output, and said second reference level generation mechanism being moved away from said position by a predetermined distance, thereby enabling the reflected light to be transmitted to the image reading element without reference to the first reference level generation mechanism.