The Optics of Fingerprint Sensors

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The Optics of Fingerprint Sensors
By Courtney Krafczyk, Rebecca Holmes, Michelle Victora, Jia Jun Wong, and Sheldon Scot Schlie, University of Illinois at Urbana Champaign, Illinois, USA 



Optical fingerprint sensors use frustrated total internal reflection to distinguish the ridges and valleys in a fingerprint. A source illuminates a high refractive index material at a steep angle. When a finger is pressed against the material, the resulting bright and dark regions are captured with a camera and used to identify a person.