Microscopic printed anti-counterfeiting codes

Among the vast range of anti-counterfeiting methods, connected labels are in high demand. These labels are made up of microscopic dot matrices obtained by printing. They guarantee the authenticity of the products, which can be verified using more or less complex reading instruments, ranging from smartphones for the general public to optical microscopes for the authorities, for example.

The security of the products therefore depends on the ability to measure the printed dots. As part of his thesis at LGP2, Louis Vallat-Evrard, a graduate of Grenoble INP - Pagora, contributed to the development of equipment and methods for measuring printed dots at the microscopic scale. This thesis was a follow-up to the Estampille ANR** project, whose objective was to fight against the falsification of printed documents and the counterfeiting of products of commercial value by printing a secure, non-copyable, non-modifiable "Graphic Code" within the document, packaging or label of the original medium.

After working on the printing process in the laboratory, the young researcher used signal processing methods to analyse certain phenomena, such as optical and physical enlargement of the dot, in order to identify the characteristic variations associated with the use of an ink, a deposition process or even a printer. Two specially-designed algorithms were developed for analysing dot prints, as well as models relating the physical and optical characteristics of the dots to a given printer,. "In addition to reading the codes, the measuring tools will make it possible to determine whether they have been printed with an authorised printer and thus increase the reliability of anti-counterfeiting protection," explains Louis Vallat-Evrard. For the future, the young PhD plans to use his expertise at the Banque de France or the European Central Bank.

CNRS / Grenoble INP / Agefpi
*LGP2: Laboratory of Paper Processes Engineering
**ANR: French National Research Agency