Abstract: There is disclosed a tamper-free identification system, such as an ID card, comprising an information-bearing substrate made of a flexible but substantially rigid material, a partial light reflector superposed over said substrate which produces a substantially nondepolarizing light reflection, and a substantially transparent 90.degree. retarder superposed over said reflector. Said identification card can be manufactured at low cost using techniques known in the art, and with the aid of a simple and inexpensive analyzer such as a linear light polarizer, fraudulent alternations of the identification card can readily be detected.
Type:
Grant
Filed:
December 3, 1984
Date of Patent:
April 21, 1987
Assignee:
Optical Devices, Incorporated
Inventors:
Daniel T. Reiner, Lawrence Bolt, Philip W. Morlan, Jr., Ali Tavasolian