In a fingerprint input apparatus used to detect an image of a fingerprint, light is emitted towards a finger which is placed on an image detecting surface of a prism. An incident angle of light on the image detecting surface is less than a critical angle. An image sensor detects light which has been...http://www.google.fr/patents/US5623553?utm_source=gb-gplus-shareBrevet US5623553 - High contrast fingerprint image detector
