Method to apply an invisible mark on a media
The present application aims to propose a solution for embedding invisible mark suitable for very large production volumes. This is achieved by a method for applying an invisible mark on a media based on a pattern, and comprising the following steps: determining an area to apply this mark, applying a transparent or semi-transparent substance, on the media, said substance being modulated with the active dots to form the pattern by modifying the quantity of the substance at each active dot.
1. A method for authenticating and tracing an industrially printed material, comprising:
applying a mark in a manner that is invisible for the naked eye based on the creation of pseudo-random defects on the surface of said material by the means of an industrial printing technology using a liquid substance capable of solidification upon drying in which the liquid substance is deposited over at least a portion of the material with a regular thickness in areas other than individual locations corresponding to active dots of the mark and having a modulated thickness in areas corresponding to the active dots of the mark, the active dots representing a pseudo-random two dimensional pattern initialized by a key, said substance modifying at least one optical characteristic of said material, said defects having an individual size ranging from 10 to 500 micrometers; and
detecting said mark at a later time by measuring the signal to noise ratio of the two dimensional digital signal obtained by cross-correlating said pattern with a digital two-dimensional digital image of the printed material.
2. The method according to claim 1 , wherein the substance is an ink, a varnish, a plastic or a glue coating.
3. The method to detect a mark applied according to the method of claim 2 , comprising the following steps:
acquiring an image comprising the mark,
auto-correlating the acquired image so as to determine the rotation and the scaling factors,
applying the rotation and scaling factors in a cross-correlation process between a referenced mark and the acquired image,
determining the maximum energy peaks of the cross-correlation process and comparing these energy peaks with a reference.
4. The method according to claim 1 , wherein the quantity of the substance is lowered at each active dot.
5. The method to detect a mark applied according to the method of claim 4 , comprising the following steps:
acquiring an image comprising the mark,
auto-correlating the acquired image so as to determine the rotation and the scaling factors,
applying the rotation and scaling factors in a cross-correlation process between a referenced mark and the acquired image,
determining the maximum energy peaks of the cross-correlation process and comparing these energy peaks with a reference.
6. The method according to claim 1 , wherein the quantity of the substance is increased at each active dot.
7. The method to detect a mark applied according to the method of claim 6 , comprising the following steps:
acquiring an image comprising the mark,
auto-correlating the acquired image so as to determine the rotation and the scaling factors,
applying the rotation and scaling factors in a cross-correlation process between a referenced mark and the acquired image,
determining the maximum energy peaks of the cross-correlation process and comparing these energy peaks with a reference.
8. The method according to claim 1 , wherein the substance is completely removed where active dots are defined.
9. The method to detect a mark applied according to the method of claim 8 , comprising the following steps:
acquiring an image comprising the mark,
auto-correlating the acquired image so as to determine the rotation and the scaling factors,
applying the rotation and scaling factors in a cross-correlation process between a referenced mark and the acquired image,
determining the maximum energy peaks of the cross-correlation process and comparing these energy peaks with a reference.
10. The method according to claim 1 , wherein the mark applied comprises auto-correlation characteristics, in which a first mark is at least one time duplicated and shifted so that the superposition of the first mark and the shifted one form the applied mark.
11. The method according to claim 10 , wherein the first mark is duplicated four times, the first duplication being shifted according to the X axis, the second duplication being shifted according to the Y axis and the third duplication being shifted according to both X and Y axes.
12. The method to detect a mark applied according to the method of claim 11 , comprising the following steps:
acquiring an image comprising the mark,
auto-correlating the acquired image so as to determine the rotation and the scaling factors,
applying the rotation and scaling factors in a cross-correlation process between a referenced mark and the acquired image,
determining the maximum energy peaks of the cross-correlation process and comparing these energy peaks with a reference.
13. The method to detect a mark applied according to the method of claim 10 , comprising the following steps:
acquiring an image comprising the mark, ,
auto-correlating the acquired image so as to determine the rotation and the scaling factors,
applying the rotation and scaling factors in a cross-correlation process between a referenced mark and the acquired image,
determining the maximum energy peaks of the cross-correlation process and comparing these energy peaks with a reference.
14. The method according to claim 1 , wherein the mark comprises active and inactive dots in which the ratio between active and inactive can be as low as 10% and represents the pattern.
15. The method to detect a mark applied according to the method of claim 14 , comprising the following steps:
acquiring an image comprising the mark,
auto-correlating the acquired image so as to determine the rotation and the scaling factors,
applying the rotation and scaling factors in a cross-correlation process between a referenced mark and the acquired image,
determining the maximum energy peaks of the cross-correlation process and comparing these energy peaks with a reference.
16. The method to detect a mark applied according to the method of claim 1 , comprising the following steps:
acquiring an image comprising the mark,
auto-correlating the acquired image so as to determine the rotation and the scaling factors,
applying the rotation and scaling factors in a cross-correlation process between a referenced mark and the acquired image,
determining the maximum energy peaks of the cross-correlation process and comparing these energy peaks with a reference.
17. The method according to claim 16 , wherein the rotation and scaling factors are applied on the referenced mark.
18. The method according to claim 16 , wherein the rotation and scaling factors are applied on the acquired image.
19. The method according to claim 16 , wherein it comprises a further step of removing the underlying image on the acquired image by calculating an average value of the acquired signal over a first surface, and subtracting this average value on a unitary acquired surface, said first surface being larger than the unitary surface.
20. The method according to claim 16 , wherein a particular mark pattern initialized by a key is identified by successively cross-correlating several different pseudo-random patterns from a library of possible mark patterns, each pattern being initialized by a different key, until the matching particular mark pattern is found.
21. A method for authenticating and tracing an industrially printed material comprising:
applying a mark in a manner that is invisible for the naked eye based on the creation of pseudo-random defects on the surface of said material by the means of an industrial printing technology using a liquid substance capable of solidification upon drying in which the liquid substance is deposited over at least a portion of the material with a regular thickness in areas other than individual locations corresponding to active dots of the mark and having a modulated thickness in areas corresponding to the active dots of the mark, the active dots representing a pseudo-random two dimensional pattern initialized by a key, said substance modifying at least one optical characteristic of said material;
wherein said defects having an individual size ranging from 10 to 500 micrometers.