Patent ID: 7349134

Claim:
An image reading apparatus that reads an image using a monochrome image sensor, comprising: the monochrome image sensor including: a first sensor having a plurality of light receiving elements arranged in a primary scanning direction, a second sensor having a plurality of light receiving elements which are arranged in the primary scanning direction and at a predetermined distance away from the first sensor in a secondary scanning direction and whose light receiving positions are set between the respective light receiving elements constituting the first sensor, a first shift register for outputting the respective light reception signals obtained from the respective light receiving elements constituting the first sensor according to the order of arrangement of the corresponding light receiving elements, a second shift register for outputting the respective light reception signals obtained from the respective light receiving elements arranged at even-numbered positions among the light receiving elements constituting the second sensor according to the order of arrangement of the corresponding light receiving elements, and a third shift register for outputting the respective light reception signals obtained from the respective light receiving elements arranged at odd-numbered positions among the light receiving elements constituting the second sensor according to the order of arrangement of the corresponding light receiving elements; and an analog frontend IC having at least three channels and provided internally with: analog amplifiers for the respective channels capable of adjusting the gains with respect to analog input signals, an analog/digital converter for converting the analog input signals into digital signals and outputting the digital signals, and a multiplexer for sequentially providing the analog input signals amplified by the respective analog amplifiers to the analog/digital converter, wherein the respective light reception signals output from the first, the second and the third shift registers, respectively, are provided as the analog input signals to the analog amplifiers for the channels corresponding to the respective shift registers.