Image reading apparatus

摘要

This invention provides an image reading method and apparatus which can prevent a large difference from being produced between the color tones of the read image and the original image. A plurality of signals output from an image sensor (101) are A/D-converted into a plurality of digital signals by A/D conversion circuits (105), a predetermined one of the A/D-converted digital signals is compared with a predetermined reference level by a comparator (108), a low-pass filter (109) removes any high-frequency component from the comparison result, and the output from the low-pass filter (109) is controlled to be input to the A/D conversion circuits (105) as a reference voltage for determining the input range of each A/D conversion circuit (105). <IMAGE>