Image reader, image forming and reproducing apparatus, and image reading method

摘要

An image reader comprises an image sensor configured to receive a light beam reflected from an original to be read and output an analog pixel signal corresponding to a light quantity of the received light beam; a variable-gain amplifier configured to amplify the analog pixel signal to a prescribed level; an analog-to-digital converter configured to convert the amplifier analog pixel signal to digital image data; and correction means for performing correction on the A/D converted digital image data according to a prescribed criterion, using a data value corresponding to an original level of the analog pixel signal before the amplification.