The biometric authentication device includes a finger installation surface on which a finger to be authenticated is placed, an imaging surface opposed to and in parallel to the finger installation surface, and an image pickup surface which is totally reflected after the irradiation light is reflected by the finger installation surface, And a reflecting surface arranged at a predetermined angle with respect to the finger setting surface and the image pickup surface so as to reach the finger placement surface of the finger installation surface. When the visible light and / or the infrared light is irradiated to the imaging surface of the finger authentication prism, the first optical path that directly reaches the imaging surface and the reflected light from the finger placed on the finger installation surface, And a second optical path that reaches the imaging plane via the reflecting surface. The biometric authentication device photographs the first image based on the reflected light corresponding to the portion in the fingertip direction from the distal interphalangeal joint of the finger out of the reflected light having passed through the first optical path and the second optical path , The second image is photographed based on the reflected light corresponding to the portion in the root direction of the finger from the distal interphalangeal joint of the finger.生体認証装置は、認証対象の指が載置される指設置面と、指設置面に平行に対向配置された撮像面と、照射光が指設置面で反射された後に全反射されて撮像面に到達するように指設置面と撮像面とに対して所定の角度で配置した反射面とを具備した側面視台形形状の指認証プリズムを用いる。指認証プリズムの撮像面に可視光及び/又は赤外光を照射した際に、指設置面上に載置された指による反射光を撮像面に直接到達する第1の光路と、指設置面から反射面を経て撮像面に到達する第2の光路とに分岐させる。生体認証装置は、第1の光路及び第2の光路を経た反射光のうち、指の遠位指節間関節から指先方向の部位に対応する反射光に基づいて第1の画像を撮影するとともに、指の遠位指節間関節から指の付根方向の部位に対応する反射光に基づいて第2の画像を撮影する。
