Patent ID: 7522317

Claim:
An image reading apparatus comprising: an image pick-up unit which converts inputted light to an analog electric signal and outputs the analog electric signal; an A/D converting part which converts the analog electric signal outputted from the image pick-up unit to a digital electric signal; an output signal generating unit disposed in an output side of the A/D converting part including a signal converting part, which generates a plurality of digital output signals corresponding to the number of output bits on the basis of the digital electric signal and outputs the digital output signals; a plurality of output wiring parts provided in the output signal generating unit correspondingly to the number of the output bits; a plurality of delay circuit parts respectively disposed in the output wiring parts and delaying the output timing of the digital output signals; a selector for selecting one of the delay circuit parts; a clock signal supply unit which supplies clock signals for specifying output timing of the digital output signals; and an output timing changing unit disposed in an output side of the output signal generating unit, which changes the output timing for each of the digital output signals, wherein the output timing changing unit includes: a random enable signal output part which changes, at random, a change point of the digital output signal outputted from the signal converting part by using a control clock signal having a cycle faster than that of the clock signal supplied by the clock signal supply unit; and a select signal output part which outputs a select signal which indicates, at random, the delay circuit part selected by the selector by using a control clock signal having a cycle faster than that of the clock signal supplied by the clock signal supply unit.