Patent ID: 6922263

Claim:
An image reading apparatus comprising: a CCD sensor 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; a mirror set which conveys the light and shade corresponding to the image information to the CCD sensor; a moving mechanism which moves the mirror set along the object at a predetermined speed; a driving device which provides the moving mechanism with a driving force; a first reference level generation mechanism which is provided at a predetermined position on the moving mechanism and allows the CCD sensor 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 CCD sensor, when the first reference level generation mechanism causes the CCD sensor 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 CCD sensor without reference to the first reference level generation mechanism.