Method for registering a sub-pixel matrix arranged within a security document
Patent Information
- Application Number
- FR2022014344
- Authority / Receiving Office
- FR · FR
- Patent Type
- Patents
- Current Assignee / Owner
- Filing Date
- 2022-12-22
- Publication Date
- 2025-01-03
- Estimated Expiration
- 2042-12-22
Smart Images
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Abstract
Claims
Claims
1. Method for registering a matrix of sub-pixels arranged within a security document, the sub-pixels each being associated with a color and a target position, the document further comprising registration marks arranged around or within the matrix of sub-pixels (SP), each registration mark having a given shape and being associated with at least one color, the method comprising: a - obtaining the position within the document of the registration marks (MR), b - determining an intermediate position (PI) located between at least two positions of registration marks obtained and adjacent, c - determining the position (SPI) of the sub-pixel associated with a color of interest which is closest to the intermediate position, d - determining a set of interpolation curve parameters passing through the positions of the registration marks and through the position of said sub-pixel associated with the color of interest (SPI),e - a resetting of the subpixel matrix using the set of interpolation curve parameters and the target positions of the subpixels.,
2. Method according to claim 1, in which steps a to c are implemented iteratively, and during the repeated step a the position of said sub-pixel associated with the color of interest is considered as a position within the registration mark document obtained in the previous iteration, so that in repeated steps b and c, the positions of the registration marks include positions of said sub-pixel associated with the color of interest as a position within the registration mark document.
3. Method according to claim 1 or 2, in which in step b, several intermediate positions located between several groups of at least two positions of registration marks obtained and adjacent are determined, and in step c, the position of several sub-pixels each associated with a color of interest and closest to one of the intermediate positions is determined.
4. A method according to any one of claims 1 to 3, wherein the interpolation curve parameters are spline parameters.
5. The method of claim 4, wherein the splines are splines with two variables and order n.
6. A method according to any one of claims 1 to 5, wherein during step b, the intermediate position has a position determined relatively to the positions of said at least two obtained and adjacent registration marks.
7. Method according to any one of claims 1 to 6, wherein in step c, it is checked whether a distance between the position of said sub-pixel associated with a color of interest and the intermediate position exceeds a first distance threshold, and, if the first distance threshold is exceeded, the security document is considered invalid.
8. Method according to any one of claims 1 to 7, wherein in step c, it is checked whether a distance between the position of said sub-pixel associated with a color of interest and the intermediate position exceeds a second distance threshold, and, if the second distance threshold is exceeded, step b is re-implemented with a new intermediate position closer to one of the registration marks, and step c is re-implemented with the new intermediate position as the intermediate position.
9. Method according to any one of claims 1 to 8, comprising, after the implementation of step e and before the implementation of step f, a phase comprising: a determination of positions of additional sub-pixels arranged on said interpolation curves and located between registration marks at positions defined relative to the registration marks, a determination of a set of parameters of additional interpolation curves passing through said positions of the additional sub-pixels, and in which in step e, a registration of the matrix of sub-pixels is implemented by means of the set of parameters of interpolation curves, of the set of parameters of additional interpolation curves, and of the set of positions of the additional sub-pixels, of the target positions of the sub-pixels.
10. Method according to claim 9, in which the interpolation curves define finite elements, and, for each finite element, additional interpolation curve parameters specific to each finite element are determined, the positions of the additional sub-pixels being points of the finite element.
11. A method according to any one of claims 1 to 10, wherein the subpixels are arranged, by their target position, in a repeated pattern of subpixels all associated with different colors.
12. The method of claim 11, wherein the subpixels are printed on a layer of the document and the subpixels of a same pattern each have a different color to form a color base, or the subpixels are formed in a diffractive layer of the document and the subpixels of a same pattern each produce a different color effect by diffraction to form a color base.
13. Method according to any one of claims 1 to 12, in which a personalization of the security document is implemented based on the resetting of the sub-pixel matrix.
14. System for registering a matrix of sub-pixels (201) arranged within a security document (200), the sub-pixels each being associated with a color and a target position, the document further comprising registration marks (202) arranged around or within the matrix of sub-pixels, each registration mark having a given shape and being associated with at least one color, the system being configured to implement: a - obtaining the position within the document of the registration marks (MR), b - determining an intermediate position (PI) located between at least two positions of registration marks obtained and adjacent, c - determining the position (SPI) of the sub-pixel associated with a color of interest which is closest to the intermediate position,d - a determination of a set of interpolation curve parameters passing through the positions of the registration marks and through the position of said sub-pixel associated with the color of interest, e - a registration of the sub-pixel matrix by means of the set of interpolation curve parameters and the target positions of the sub-pixels.,
15. A computer program comprising instructions for carrying out the steps of an authentication method according to any one of claims 1 to 13, when said program is executed by a computer.
16. A computer-readable recording medium on which is recorded a computer program comprising instructions for carrying out the steps of an authentication method according to any one of claims 1 to 13.