Patent ID: 8724180

Claim:
An image reader comprising: a first image reading unit comprising a plurality of first light receiving elements each of which is assigned to one of at least one channel, the first image reading unit being configured to read an image on a first side of a first document sheet being conveyed along a feeding path with the first light receiving elements, and output an analog signal output from each of the first light receiving elements, via a corresponding one of the at least one channel to which each of the first light receiving elements is assigned; a second image reading unit comprising a plurality of second light receiving elements each of which is assigned to one of channels which are at least two more than the at least one channel for the first image reading unit, the second image reading unit being configured to read an image on a second side of the first document sheet being conveyed along the feeding path with the second light receiving elements, and output an analog signal output from each of the second light receiving elements, via a corresponding one of the channels to which each of the second light receiving elements is assigned; a first analog front end unit configured to perform A/D conversion for analog signals that are output via a first group of channels of a number resulting from rounding up, to a closest whole number, an average value between a number of the at least one channel for the first image reading unit and a number of the channels for the second image reading unit, among the analog signals output from the first image reading unit and the second image reading unit; and a second analog front end unit configured to perform A/D conversion for analog signals that are output via a second group of channels other than the channels in the first group, among the analog signals output from the first image reading unit and the second image reading unit.