Concealed moiré pattern encoded security holograms readable by a key hologram

• Published in: Optics and laser technology 2006-03, Vol.38 (2), p.117-121
• Main Authors: Aggarwal, A.K., Kaura, Sushil K., Chhachhia, D.P., Sharma, A.K.
• Format: Article
• Language: English
• Subjects: Concealed coding holograms; Exact sciences and technology; Fundamental areas of phenomenology (including applications); Hologram recording and read-out methods; Holography; Moiré pattern encoded holograms; Optical security; Optics; Physics; Security holograms
• ISSN: 0030-3992; 1879-2545
• DOI: 10.1016/j.optlastec.2004.10.010

This paper describes a novel method of incorporating concealed coding features in security holograms in the form of moiré patterns, which need an encoded key hologram to decode them. These concealed codes in the holograms are in turn recorded with an encoded feature, so that these remain invisible to the counterfeiters thereby enhancing the anti-counterfeiting ability of security holograms. These security features, which are specific kinds of moiré patterns, can only be decoded by using an encoded key hologram in the final reading process. Though these type of security holograms are quite suitable for visual inspection, they possess high degree of anti-counterfeit ability and also do not require expensive reading machines. They can also be used as security codes for better protection against counterfeiting embossed holograms. Two different recording schemes for the formation of such security holograms and typical experimental results have been presented.