Patent ID: 8310741

Claim:
An image reading device comprising: a light source; an image reading unit including a photoelectric conversion element that reads an image illuminated by the light source; a drive control unit configured to drive the image reading unit; a white reference member arranged at a position which allows the image reading unit to perform image reading; a chromaticity detecting unit configured to detect chromaticity of an image of the white reference member read by the image reading unit; a reference value storage unit configured to store a first reference value representing chromaticity of the image of the white reference member read by the image reading unit and a second reference value representing luminous intensity of the light source at a predetermined normal temperature; a chromaticity change calculating unit configured to calculate the amount of chromaticity change between the chromaticity represented by the first reference value stored in the reference value storage unit and the chromaticity detected by the chromaticity detecting unit during operation of the image reading unit; and a control unit configured to control an operation of the image reading device according to the amount of chromaticity change calculated by the chromaticity change calculating unit, wherein the control unit comprises: a drive current correcting unit configured to correct, according to the amount of chromaticity change calculated by the chromaticity change calculating unit, a drive current value that the drive control unit uses to drive the light source; a luminous intensity detecting unit configured to detect luminous intensity of the light source driven by the drive control unit at the drive current value corrected by the drive current correcting unit; and a gain correcting unit configured to correct a gain according to the amount of change between the second reference value representing luminous intensity stored in the reference value storage unit and the luminous intensity of the light source driven at the corrected drive current value, the luminous intensity being detected by the luminous intensity detecting unit, and correct an output value from the photoelectric conversion element to a value corresponding to the second reference value representing luminous intensity by performing automatic gain control using the corrected gain.