Optical correlator using photorefractive polymers for credit card validation

Using optical phase masks is a promising solution for validation of a credit cards and other documents authenticity. 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 demonstrated in this paper. The entire system employs plastics and laser diodes for its operation and thus can be very compact and inexpensive to implement. The experimental demonstration using this method is presented and discussed.