Patent ID: 7408683

Claim:
An image reading apparatus comprising: an image sensor that includes: a plurality of photoelectric conversion elements arranged in a main scanning direction, each of the plurality of photoelectric conversion elements generating an analog image signal corresponding to an amount of incident light thereon, the plurality of photoelectric conversion elements being divided into plural groups, each of the plural groups including a predetermined number (N) of the photoelectric conversion elements; a plurality of switching elements connected to respective ones of the plurality of photoelectric conversion elements, individually; a control unit that controls the plurality of switching elements in response to an external clock signal to simultaneously output the image signals from the predetermined number of photoelectric conversion elements in one of the plural groups; and signal output lines with a number of N, wherein the predetermined number of photoelectric conversion elements in each of the plural groups are connectable with the respective ones of the signal output lines through the switching elements, individually, to output the image signals from the predetermined number of photoelectric conversion elements to the signal output lines; a multiplexer connected to the image sensor for multiplexing the image signal transferred from one of the photoelectric conversion elements through the corresponding one of the signal output lines; and a sample-and-hold circuit connected to the image sensor for temporarily storing the image signals transferred from the photoelectric conversion elements in one group though the corresponding ones of the switching elements and the signal output lines; wherein the multiplexer is configured to connect with the image sensor so that one signal output line connects the image sensor to the multiplexer directly and the other signal output lines connect the image sensor to the multiplexer through the sample-and-hold circuit.