Abstract

Using optical phase masks is a promising solution for validation of a credit cards and other documents authenticity.¹ These masks placed on a document are invisible to the eye and, as such, are impossible to reproduce by any photographic process. They can be manufactured of transparent durable plastics and identified by an optical correlator using efficient photorefractive polymers as nonlinear material, as we demonstrate in this paper. The entire system employs plastics and laser diodes for its operation and thus can be very compact and inexpensive to implement.

© 1996 Optical Society of America