1 January 1999 New optical security device based on one-hundred-year-old photographic technique
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Abstract
A new optical security application of an old color photographic technique (Lippmann photography, invented in 1891) is presented. Today, this type of photography can be applied as a unique security device on security documents, such as, e.g., identification cards, passports, credit cards, and other documents where a high degree of security is needed. A Lippmann photograph is very similar to the holograms currently used in this field; however, a unique recording of each document can be made to achieve a degree of security higher than that with mass- produced holograms. The recording of Lippmann photographs requires a special type of photosensitive medium in contact with a reflecting layer. Panchromatic photopolymer materials can be used and, after being recorded and processed, laminated to security documents. A special type of recording equipment is required. Lippmann photographs are virtually impossible to copy and, certainly, cannot be copied by conventional photography or color copying machines.
Hans I. Bjelkhagen, "New optical security device based on one-hundred-year-old photographic technique," Optical Engineering 38(1), (1 January 1999). https://doi.org/10.1117/1.602061
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