OPTICAL FINGERPRINT ACQUISITION APPARATUS

摘要

PURPOSE: An optical fingerprint image obtaining device obtains a square image of a fingerprint as a photorefractor corrects the distortion of the fingerprint image. CONSTITUTION: A first lens (G1) is a plain cylindrical lens and receives the light emitted by a photorefractor (10). A second lens (G2) is also a plain cylindrical lens and receives the light passing through the first lens with the centers of the two lenses aligned on a virtual axis. A third lens (G3) directs the light from the second lens to an image sensor (230). An aperture diaphragm is placed either between the first and second lenses or beside the second lens. The first and second lenses are decentered in a way where the optic axis of the light from the photorefractor is not overlapped with the virtual axis of the two lenses so that the two lenses can correct an image with distortion caused by the photorefractor.