Patent ID: 6556316
Filing Date: 2003-04-29
Classification: H04N

Abstract:
An image reading device comprising:a lens; a solid-state image sensor which reads an original image via said lens; a variable aperture mechanism having an aperture which is adjustable over an aperture range which is operative to change an amount of light transmitted to said solid-state image sensor from the original; and a light reducing means which reduces light transmitted to the solid-state image sensor from the original, wherein the magnitude of said aperture range is dependent on the light reducing level of said light reducing means and on said lens such that an amount of light reduced by diffraction of the light passing through said aperture is below a predetermined value, the size of the aperture being increased as the light reducing level increases, wherein said aperture range is defined by a characteristic of said lens, said characteristic of said lens being a ratio of incident light to said lens and irradiated light from said lens.