Patent ID: 7446299

Claim:
A multi-spectrum illuminating device, comprising: a multi-spectrum illuminating device for irradiating lights of different wavelengths to an irradiated surface; and an image-capturing optical system for forming an image based on lights reflected from the irradiated surface under illumination by the multi-spectrum illuminating device; wherein components of the reflected lights captured via the image-capturing optical system are analyzed to measure color components of the irradiated surface; wherein the multi-spectrum illuminating device comprises: a plurality of light sources for emitting the lights of different wavelengths; optical rods for relaying the lights emitted from the light sources; and a pair of optical diffusion elements, each of which includes a plurality of reflecting surfaces arranged to enclose at least one optical path along which at least one of the lights is transmitted from a corresponding at least one of the optical rods, wherein the reflecting surfaces of the optical diffusion elements reflect the lights from the optical rods, while diffusing the lights, such that the lights diffused by the reflecting surfaces are irradiated to the irradiated surface; wherein the pair of the optical diffusion elements are provided so as to be opposed to the image-capturing optical system and so as to be spaced apart from and opposed to each other; and wherein each of the optical diffusion elements includes an optical sheet through which the lights from the optical rods are transmitted, which is disposed on an exit-end surface side of the optical diffusion element and which has a gradation characteristic that is inverse to a luminance distribution at occurrence of unevenness in illumination on the irradiated surface so as to reduce the unevenness in illumination on the irradiated surface.