Patent ID: 8488219

Claim:
An image reading apparatus, comprising: a light source configured to illuminate an original; a color sensor and a monochrome sensor configured to receive light reflected from the original illuminated by the light source to output an image signal, the color sensor being a sensor configured to output a color image signal, and the monochrome sensor being a sensor configured to output a monochrome image signal; an amplifier configured to amplify the image signal from the color sensor and the monochrome sensor; a reflective reference member; a storage device configured to store a ratio of a gain setting value for the monochrome sensor to a gain setting value for the color sensor; and a control circuit configured to adjust a color gain setting value for the color sensor based on a color image from the color sensor that receives light reflected from the reflective reference member illuminated by the light source, and to calculate a monochrome gain setting value for the monochrome sensor based on an adjusted color gain setting value and the ratio stored in the storage device.