Security Holograms Readable with an Encoded Key Hologram

Abstract

A simple and cost effective two-step method for making security holograms, which are readable with an encoded key hologram, has been presented. These security holograms contain an additional security feature which can be read only by using an encoded key hologram in the reading process. In the final reading process, the sharp focus spot emerges only when the security hologram is illuminated by the decoding, reconstructing beam generated from the encoded key hologram. Since the verification/identification pattern in these holograms is a sharp focus spot rather than an image pattern, this type of security holograms are suitable for both visual as well as machine inspection. They can also be used as security codes for better protection against counterfeiting in the embossed holograms. Experimental results achieved have been discussed