Patent ID: 8305663

Claim:
An image reading device comprising: an optical-to-electrical conversion element that receives an optical signal of an optical image, and outputs an electrical signal of an analog image signal corresponding to the optical image; an analog processing circuit that samples the analog image signal output from the optical-to-electrical conversion element to obtain continuous analog image signals, and amplifies a voltage of the analog image signals to a predetermined voltage; an analog-to-digital conversion circuit that quantizes an output from the analog processing circuit to generate a digital image signal; a clock generating unit that generates temporally-continuous clock signals; a spread-spectrum clock-signal generating unit that generates a spread-spectrum clock signal by modulating a frequency spectrum of a clock signal generated by the clock-signal generating unit; a clock-signal generating unit that generates a plurality of drive clock signals for driving the optical-to-electrical conversion element and the analog processing circuit from the spread-spectrum clock signal generated by the spread-spectrum clock-signal generating unit; and a signal delaying unit that generates, with respect to at least a first drive clock signal from among the drive clock signals, a fixed delay unaffected by a spread spectrum based on an edge timing of a second drive clock signal other than the first drive clock signal, and obtains a desired timing by applying the fixed delay to the first drive clock signal, wherein the signal delaying unit generates a first edge of a clamp signal supplied to the optical-to-electrical conversion element from among the drive clock signals at a same timing as a first edge of a reset signal supplied to the optical-to-electrical conversion element, generates the fixed delay based on a timing of the first edge of the reset signal, and forms a desired clamp signal timing by applying the fixed delay to the clamp signal.