BILDLESEVORRICHTUNG

摘要

An image reading apparatus in which automatic gain control is performed comprises a reading unit, integrated with an optical system having a light source (12) for irradiating an original, a rod lens array (13) for focusing an image, a line image sensor (11) for reading the image, and a white reference plate (17) attached on one end of reading unit so as to move together therewith. There is effect in that one and the same portion of the white reference plate is read by the line image sensor as it scans across a document so that gain control of the output of the line image sensor is based on a constant reference white. Further even if a part of the white reference plate becomes dirty, an even output can be obtained throughout the whole surface of the original to thereby make it possible to prevent deterioration, such as generation of transversal stripes, from occurring in the output picture. <IMAGE>