Microlens array structures designed to defeat automated photocopying of documents

A microlens array structure that prevents automated photocopying is presented. This copy defeat laminate (CDL) employs a cylindrical lens array structure in conjunction with a mask pattern to prevent at-normal viewing of the document. Image brightness perceived by the human eye is reviewed as well as basic radiometry. Equations for Lambertian and CDL image brightness are derived. The brighter-than-white appearance of a CDL covered document is explained. Designs for the full-page-defeat and full-page-view versions of the CDL are presented.