US Patent 7609864 Finger identification method and apparatus

An image pickup scheme capable of always providing an optimum quality of a blood vessel pattern, in image pickup of a blood vessel pattern of a finger using transmitted light, without being affected by a difference, if any, in an external environment. A personal identification apparatus includes light sources for irradiating light to be transmitted by a finger, an image pickup unit for picking up an image using light transmitted by the finger, finger detection unit for detecting that the finger exists in a predetermined position, finger region extraction unit for extracting a region occupied by the finger from an image picked up by the image pickup unit, and gain changing unit for changing an amplification factor of image pickup elements in the image pickup unit on the basis of a picture quality of a specific region within the extracted region.