Abstract

Rapid technological progress makes the reproduction of current optical security features on value documents (such as the embossed dove hologram on credit cards) increasingly simple [1]. The alarming increase of counterfeiting has generated a need for new optical security technologies. The use of phase-only features can greatly complicate forgery as it requires interferometric techniques for copying [2]. We demonstrate how important documents, such as credit cards, can be encoded with 2D phase-only pseudo-random masks and verified automatically with a compact low cost optical correlator employing photorefractive polymers.

© 1997 Optical Society of America