Abstract: An image reading device is provided with a waveform memory that stores correction waveform data generated based on a digital image signal output from an image signal processing circuit when a light source of the image reading device is turned off, and an image signal correcting circuit that corrects an image signal of an original image using the correction waveform data stored in the waveform memory.

Abstract: An image reading device includes a processing circuit having a clamp unit that matches an offset potential of an inputted analog image signal to a predetermined value, a processing unit that subjects an analog image signal obtained from the clamp unit to analog processing, and a converting unit that converts a processed analog image signal to a digital image signal. A control unit for controlling the processing circuit includes a switching unit that switches a main scanning line period of a charge coupled device and outputs analog image signals using a number of reading speeds, and a changing unit that changes a clamp period depending on the main scanning line period.

Abstract: A reference-signal generating unit generates a reference signal for generating a driving signal to drive each unit of the image reading device. A frequency modulating unit modulates frequency of the reference signal, thereby generating a frequency-modulated reference signal. A driving-signal generating unit generates the driving signal from the frequency-modulated reference signal. A photoelectric converting unit converts an incident light into an analog image signal using the driving signal. An AD converting unit converts the analog image signal into a digital image signal. A correcting unit corrects the digital image signal by generating a correction signal for eliminating a noise superimposed on the digital image signal using the frequency-modulated reference signal and adding the correction signal to the digital image signal.

Abstract: A clock output from a quartz oscillator is input to a timing generator via a spread spectrum clock generator that spreads the spectrum of the clock. The clock is multiplexed by a phase locked loop to generate pixel clocks having the same frequency as a pixel frequency. The pixel clock is input to a delay locked loop, which generates a multi-layer clock by dividing each cycle of the pixel clock by 60. Clock generating units select a required phase from the multi-layer clock, thereby generating a timing signal. The phase, the pulse width, and the output period of the timing signal are controlled as desired by setting appropriate values to a register.

Abstract: A clock-signal generating unit generates temporally-continuous clock signals. A spread-spectrum clock-signal generating unit generates a spread-spectrum clock signal by modulating a frequency spectrum of a clock signal generated by the clock-signal generating unit. A signal delaying unit generates a fixed delay unaffected by a spread spectrum from the spread-spectrum clock signal generated by the spread-spectrum clock-signal generating unit, and delays a phase of the spread-spectrum clock signal based on an amount of the fixed delay.

Abstract: In an image reading device, a sampling-and-holding circuit generates a plurality of analog image signals by sampling an image signal at each sampling-and-holding timing and holding sampled image signals for a predetermined amount of time, an analog-to-digital converting unit converts the analog image signals into a plurality of digital image signals at each sampling-and-holding timing, a phase regulating unit performs phase regulation of each sampling-and-holding timing based on corresponding digital image signals to obtain phase-regulated sampling-and-holding timing. The sampling-and-holding circuit generates the analog image signal at each phase-regulated sampling-and-holding timing.

Abstract: An image reading device includes a processing circuit having a clamp unit that matches an offset potential of an inputted analog image signal to a predetermined value, a processing unit that subjects an analog image signal obtained from the clamp unit to analog processing, and a converting unit that converts a processed analog image signal to a digital image signal. A control unit for controlling the processing circuit includes a switching unit that switches a main scanning line period of a charge coupled device and outputs analog image signals using a number of reading speeds, and a changing unit that changes a clamp period depending on the main scanning line period.