An optical imaging device for forming optical images of fingerprints of a finger, the device comprising: an optical plate having a portion at one end of a main face that is provided for illuminating the finger through the plate, the reflected light beam propagating with multiple reflections inside the plate to the other end thereof, which end presents an inclined end face; a focusing lens facing the end face with the lens having its axis situated in the midplane of the plate; and a mirror for directing the light beam leaving the end face onto the axis of the lens.