US Patent 7321725 Light-amount control device for photographing

A light-amount control device includes a plurality of lighting units each of which emits light for illuminating a photographing area of a photographing optical system. Further, the light-amount control device includes a peripheral light amount data calculator and a lighting unit controller. The peripheral light amount data calculator calculates a peripheral light amount data defining ratios of light emission intensities for the lighting units, to make the illuminance of an image plane of a standard object that has a flat surface being perpendicular to the optical axis of the photographing optical system and having a constant reflecting light ratio, constant when the standard object is illuminated by the lighting units. The image plane is formed by reflected light from the surface of the standard object that enters the photographing optical system. The lighting unit controller controls the lighting units so that the intensity of light at a wider illuminating angle to an optical axis of the photographing optical system becomes higher, based on the peripheral light amount data.