The present invention is an authentication device that has a prism body, an imaging unit, a visible-light light source that illuminates a body part with visible light, and an infrared light source that illuminates the body part with infrared light. The prism body is provided with the following: a body-part contact surface that makes contact with the body part a reflecting surface that shares an edge with the body-part contact surface and reflects, via total internal reflection, visible light from concavities in the body part and convexities on the body part and infrared light from inside the body part and an imaging surface that faces the body-part contact surface and shares an edge with the reflecting surface. The imaging surface is provided at an angle whereby direct light from the body-part concavities does not reach the imaging surface but light reflected by the reflecting surface via total internal reflection and light from the body-part convexities can pass through the imaging surface. The imaging unit simultaneously images the light that passes through the imaging surface, namely: the light from the body-part convexities the light, reflected by the reflecting surface, from the body-part concavities and convexities and the light, reflected by the reflecting surface, from inside the body part.Linvention concerne un dispositif dauthentification comprenant un corps de prisme, une unité dimagerie et une source de lumière visible qui éclaire une partie corporelle avec une lumière visible, et une source de lumière infrarouge qui éclaire la partie corporelle avec la lumière infrarouge. Le corps du prisme est pourvu : dune surface de contact de partie corporelle qui est en contact avec la partie corporelle dune surface réfléchissante qui partage un bord avec la surface de contact de la partie corporelle et réfléchit, par réflexion interne totale, la lumière visible des concavités dans la partie corporelle et des convexités sur la partie corporelle et la lumière infra
