Patent ID: 8638480

Claim:
An image reading apparatus comprising: a light source unit that irradiates a document over an elongated reading area, the light source unit including a plurality of light sources each having an LED; an imaging unit that converges light reflected from the document irradiated by the light source unit; a plurality of color separation units that have different passing wavelength bands from each other; a plurality of photoelectric conversion units each of which converts the reflected light passing through one of the color separation units having a passing wavelength band different from the other passing wavelength bands into an electrical signal; a current amount setting unit that sets an amount of current to be supplied to each light source of the light source unit; a duty setting unit that sets a duty ratio for each light source of the light source unit based on the amount of current set by the current amount setting unit, such that a luminance difference arising due to the amount of current to be supplied to each light source is reduced; and a driving unit that drives the each light source by pulse-width modulation based on the amount of current set by the current amount setting unit and the duty ratio set by the duty setting unit for the corresponding light source, wherein the current amount setting unit sets the amount of current of a light source for irradiating a center of the elongated reading area and the amount of current of light sources for irradiating ends of the elongated reading area, such that a difference between a value of the electrical signal of the center of the elongated reading area and values of the electrical signals of the ends of the elongated reading area is reduced.