Patent ID: 6700683
Filing Date: 2004-03-02
Classification: H04N

Abstract:
An image reading apparatus for reading an image of a document placed on a document table by scanning said document using light irradiation means, comprising:a white reference plate located outside a document reading area near said document table and at a position of a second optical path length between said light irradiation means and said white reference plate, which is different from a first optical path length between said light irradiation means and said document table at a time of scanning said document; photoelectric conversion means for converting an amount of reflected light at a time of irradiating said white reference plate with said light irradiation means and an amount of reflected light at a time of irradiating said document table with said light irradiation means into electric signals; setting means for setting a ratio of the electric signal which is acquired by said photoelectric conversion means when said white reference plate is irradiated by said light irradiation means while a white chart having a reflectance corresponding to said white reference plate is placed on said document table, to the electric signal which is acquired by said photoelectric conversion means when said white chart on said document table is irradiated by said light irradiation means; change means for changing an amount of light at a time of scanning each of said white reference plate and said document table with said light irradiation means, based on said ratio set by said setting means; and correction means for, with said amount of light changed by said change means, correcting said read image at a time of scanning said document table, based on a reference signal at a time of scanning said white reference plate.