PROBLEM TO BE SOLVED: To provide a biometric authentication device which is an optical type, thin, and compact, which has high authentication accuracy of a fingerprint, so that which can be used and developed in a mobile application, so that market scale thereof can be expanded.SOLUTION: A biometric authentication device comprises: a cover glass 1 with which a part of a fingerprint of a finger is brought into contact； illumination means 7 for making light enter a non-contact part of a finger f which contacts the cover glass 1； and an imaging apparatus 3 for imaging the cover glass 1 to which the finger 1 contacts. Between the cover glass 1 and the imaging apparatus 3, a prism 2 for guiding light from the cover glass 1 to the imaging apparatus 3 is provided. The prism 2 comprises: an incidence surface 21 which the light from the cover glass 1 enters； an emission surface 22 which is separated from the incidence surface 21 in a plane direction of the cover glass 1； and plural reflection surfaces 23-26 for reflecting the light, changing the direction of the light and guiding the light from the incidence surface 21 to the emission surface 22.SELECTED DRAWING: Figure 1COPYRIGHT: (C)2018,JPO&INPIT【課題】指紋の認証精度の高い光学式で薄く小型なことによりモバイル用途で利用可能となり、モバイル用途に展開できることにより市場規模の拡大が見込める生体認証装置を提供する。【解決手段】生体認証装置は、指の指紋の部分が接触させられるカバーガラス１と、カバーガラス１に接触する指ｆの非接触部分に光を入射させる照明手段７と、指ｆが接触したカバーガラス１を撮像する撮像装置３とを有する。カバーガラス１と撮像装置３との間には、カバーガラス１から撮像装置３に光を導くプリズム２を有する。プリズム２は、カバーガラス１からの光が入射する入射面２１と、入射面２１に対してカバーガラス１の面方向に離れる出射面２２と、光を反射して光の方向を変えながら光を入射面２１から出射面２２に導く複数の反射面２３～２６とを備える。【選択図】図１
