Patent ID: 8861041

Claim:
An image reading device, comprising: an oscillating circuit to generate a reference clock signal; a timing generator circuit to modulate a frequency of the reference clock signal to generate a second clock signal in which frequency spectrum is spread, and to generate a drive signal and a reading clock signal, the drive signal and the reading clock signal being based on the second clock signal; an image sensor, driven by the drive signal output from the timing generator circuit, to convert an optical image of an original image to an analog image signal; an image signal processing circuit including an analog-to-digital converter to convert the analog image signal output from the image sensor to a first digital image signal; a waveform memory to store correction waveform data, the correction waveform data being a second digital image signal that is output from the analog-to-digital converter when the image sensor is driven by the drive signal with a light source of the image reading device being turned off; and an image signal correcting circuit to obtain the correction waveform data read out from the waveform memory based on the reading clock signal, which is supplied to the waveform memory, when the original image is being read, to adjust an amplitude and a phase of the correction waveform data to generate an adjusted correction waveform data, and to add the adjusted correction waveform data to the first digital image signal to output a corrected image signal from which noises due to the frequency modulation of the reference clock signal are removed.