EP3999357A1

EP3999357A1 - Method for manufacturing a two-dimensional coloured bar code and associated security device

Info

Publication number: EP3999357A1
Application number: EP20753399.3A
Authority: EP
Inventors: Benoît BERTHE; Paul AZUELOS
Original assignee: Idemia France SAS
Current assignee: Idemia France SAS
Priority date: 2019-07-17
Filing date: 2020-07-15
Publication date: 2022-05-25
Anticipated expiration: 2040-07-15
Also published as: CL2022000070A1; WO2021009461A1; MX2022000650A; ZA202200742B; FR3098757B1; JP2022542821A; US20220355610A1; AU2020313389A1; FR3098757A1; EP3999357B1; CO2022001165A2; EP4234263A3; EP4234263A2

Abstract

The invention substantially relates to a method for manufacturing a two-dimensional coloured bar code comprising an arrangement of coloured basic structural elements which encode at least one information element, the manufacturing method comprising the following steps: determining (E304) by data-processing means a group of coloured basic structural elements corresponding to the at least one information element, at least one structural element of the group comprising a pattern, and forming (E308) the at least one structural element of the group on a support in order to create the arrangement, wherein: the support comprises a printed matrix comprising a plurality of pixels, and the formation of the at least one coloured basic structural element comprises modification of the support in at least a portion of at least one sub-pixel of at least one pixel of the matric, the modification making it possible to obtain the colour and pattern of the at least one basic structural element.

Description

Title of the invention: Method of manufacturing a color bar code

two-dimensional and associated safety device

Technical area

The present invention relates to the field of bar codes

two-dimensional, and more particularly relates to the manufacture of a two-dimensional color bar code.

[0002] The invention applies in a non-exclusive manner to security devices such as identity documents, such as passports, identity cards, driving licenses, etc.

Prior art

[0003] In known manner, the authentication of a security document holder can be performed by comparing reference biometric characteristics stored in the security document with candidate biometric characteristics of the holder, obtained by means of a sensor of data

biometric.

[0004] Due to their large size and security issues,

Reference characteristics are stored in an electronic chip memory of the security document.

[0005] However, the use of an electronic chip in a security document makes the initial production of the security document and its recycling particularly tedious and expensive.

[0006] The invention aims to overcome this problem and more generally aims to store, in a secure and environmentally friendly manner, a large amount of data, such as biometric characteristics, in a security device.

Disclosure of the invention The present invention relates to a method of manufacturing a two-dimensional color bar code comprising an arrangement of colored basic structural elements encoding at least one information element,

said manufacturing process comprising the following steps:

- determination, by data processing means, of a set of colored basic structural elements corresponding to said at least one piece of information, at least one structural element of the set comprising a pattern, and

- forming said at least one structural element of the assembly on a support, in order to create the arrangement of colored basic structural elements,

in which :

- the support comprises a printed matrix comprising a plurality of pixels, each pixel comprising at least two sub-pixels of different colors, and

the formation of said at least one colored basic structural element comprises a modification of the support at the level of at least part of at least one sub-pixel of at least one pixel of the matrix, said modification making it possible to obtain the color and the pattern of said at least one basic structural element.

[0008] The invention makes it possible to encode and therefore store in the bar code a

large amount of information over a limited area, such as part of the area of a security document.

[0009] Indeed, the use of colors in the bar code allows to encode

much more data than a two-dimensional black-and-white barcode of the same size, that is, a two-dimensional barcode in which each basic structural element is either all black or all white. The data density, i.e. the amount of data (in bytes) stored per unit area (in square millimeters) of such a two-dimensional barcode in black and white and indeed less than 1 byte per square millimeter, while the invention allows a higher data density, typically at least 4 bytes per square millimeter.

[0010] In addition, the technique for creating the arrangement allows storage

secure the piece of information in the barcode. Indeed, the arrangement cannot be modified without altering the barcode support, unlike traditional bar code printing techniques (inkjet, screen printing or offset, for example), making it possible to print another bar code on top of the bar code initially formed.

In addition, the basic structural element encoding an information element by its color and its pattern, it is possible to read the bar code by means of several different types of sensors, such as a standard color sensor or a grayscale sensor.

[0012] In a particular embodiment, said information element is a reference biometric characteristic, the method further comprising a step of obtaining said at least one information element from a digital representation of said element d 'information.

Thanks to the increase in data density that the color bar code offers, it is possible to store a quantity of reference biometric characteristics sufficient to allow reliable authentication of the bearer of a security document comprising the code to bars, i.e. a quantity of biometric characteristics sufficient to allow a comparison between the reference biometric characteristics and the characteristics

biometric candidates verifying the compromise between acceptable false rejection rates ("FRR" for "False Rejection Rate") and false acceptances ("FAR" for "False Acceptance Rate") .

[0014] The invention makes it possible, for example, to encode an identity photo of at least 10 kilobytes, which allows the correct functioning of the facial comparison algorithms.

In a particular embodiment, the support comprises a transparent layer, the matrix being printed vis-à-vis the transparent layer, the modification being an opacification of the transparent layer opposite said at least part of 'at least one sub-pixel of at least one pixel of the matrix or alternatively of an erasure by ablation of at least part of at least one sub-pixel, or of a combination of opacification and erasure by ablation. The formation of the structural element thus calls for a precise technology, making it possible to form the arrangement of colored basic structural elements without risk of smearing, unlike conventional bar code printing technologies.

[0017] In addition, the technique for creating the arrangement allows storage

secure information element in the barcode. Indeed, the arrangement being made at the level of two different layers or in different levels of thickness of the same layer, it cannot be modified without altering the support of the bar code.

In a particular embodiment, the opacification is carried out by means of a laser beam, the laser beam punctually charring the transparent layer so as to form a series of points facing said at least part of minus one subpixel.

[0019] In a particular embodiment, the modification is an erasure by ablation of said at least part of at least one sub-pixel of a pixel of the matrix, produced by means of a laser beam, so at least partially erasing the color of said at least part of at least one sub-pixel.

[0020] The formation of the structural element thus requires precise technology, allowing the arrangement of colored basic structural elements to be formed without risk of smearing unlike conventional bar code printing technologies.

[0021] In addition, the technique for creating the arrangement allows storage

secure information element in the barcode. Indeed, the layout cannot be changed without altering the barcode support.

[0022] In a particular embodiment:

said at least one piece of information takes the form of a group of digital data comprising a plurality of subgroups of digital data, determining a set of colored basic structural elements corresponding to said at least one element of information is produced by means of a correspondence table, associating each subgroup of data different to a different structural element of a single color and / or comprising a single pattern.

In a particular embodiment, the color of each element

structural different from the correspondence table is selected so that it can be distinguished from other colors by an image sensor

digital whose resolution is lower than the resolution necessary for the unit display of a sub-pixel, after the training step.

[0024] The invention further relates to a security device comprising a two-dimensional color bar code produced according to the manufacturing process as described above.

[0025] The invention further relates to a method for obtaining at least one piece of information encoded in a two-dimensional color bar code produced according to the manufacturing method as described above, said obtaining method comprising the following steps:

- reading of said bar code by means of a digital image sensor, and

- extraction, by data processing means, of said information element from the arrangement of colored basic structural elements, the extraction being carried out according to the positioning of each structural element in the arrangement, as well as 'depending on the color and / or pattern of each structural element of the arrangement.

[0026] In a particular embodiment, the arrangement of structural elements comprises a reference sequence comprising a plurality of basic structural elements of different colors, the reading step comprising a color calibration of the digital image sensor , based on said reference sequence.

[0027] The invention also relates to a method for authenticating a bearer of a security device as described above, comprising a color bar code comprising an arrangement of colored basic structural elements encoding at least one biometric reference characteristic,

said method comprising the following steps:

- obtaining said at least one reference biometric characteristic according to the method of obtaining as described above,

- obtaining at least one candidate biometric characteristic,

representative of the wearer by means of a biometric sensor,

- comparison, by data processing means, of said at least one candidate biometric characteristic with said at least one reference biometric characteristic, a correspondence between said at least one candidate biometric characteristic and said at least one reference biometric characteristic being a condition for successful authentication of the bearer.

In a particular embodiment, said at least one candidate biometric characteristic corresponds to said at least one reference biometric characteristic if their distance according to a predefined comparison function is less than a predefined threshold.

[0029] In a particular embodiment, the arrangement of structural elements of the two-dimensional color bar code further encodes at least one piece of information relating to the physical uniqueness of the document,

the method further comprising the following steps:

- extraction of said at least one piece of information concerning the physical uniqueness of the document,

- detection of at least one element of physical uniqueness of the document,

comparison of said at least one item of information relating to the physical uniqueness of the document and said at least one item of physical uniqueness of the document, a correspondence between said at least one item of information relating to the physical uniqueness of the document and said at least one element of physical uniqueness of the document being a condition for successful authentication of the bearer.

[0030] In a particular embodiment, the various steps of the obtaining method and / or the authentication method as described above are determined by computer program instructions.

Consequently, the invention also relates to a computer program on an information medium (or recording medium), this program being capable of being implemented by a server or more generally in a computer, this program comprising instructions adapted to the implementation of the steps of the obtaining method and / or of the authentication method as described above.

This program can use any programming language, and be in the form of source code, object code, or intermediate code between source code and object code, such as in a particularly compiled form, or in n ' any other desirable shape.

In a particular embodiment, when the computer program includes instructions adapted to the implementation of the steps of the obtaining method, the instructions of the computer program make it possible in particular to control the digital image sensor so that it reads the bar code, thereby obtaining a digital image of the bar code or at least part of the bar code.

[0034] The invention also relates to an information medium (or recording medium) readable by a server or more generally by a computer, and comprising instructions from a computer program as mentioned above.

[0035] The information medium can be any entity or device

able to store the program. For example, the medium can comprise a storage means, such as a rewritable non-volatile memory (of the “EEPROM” or “Flash NAND” type for example), or such as a “ROM”, for example a “CD ROM”. ”Or a“ ROM ”of a microelectronic circuit, or else a magnetic recording means, for example a diskette (“ floppy disk ”) or a hard disk.

[0036] On the other hand, the information medium can be a transmissible medium such as an electrical or optical signal, which can be conveyed via an electrical or optical cable, by radio or by other means. The program according to the invention can in particular be downloaded over an Internet-type network.

[0037] Alternatively, the information medium can be an integrated circuit in which the program is incorporated, the circuit being adapted to execute or to be used in the execution of the method in question. Brief description of the drawings

[0038] Other characteristics and advantages of the present invention will emerge from the description given below, with reference to the accompanying drawings which illustrate an exemplary embodiment thereof without any limiting nature. In the figures:

[0039] [Fig. 1] FIG. 1 schematically shows an example of a bar code which can be produced according to the method of FIG. 3;

[0040] [Fig. 2A] Figure 2A shows, schematically, a view of

above an example of a support that can be used during the implementation of the method of Figure 3;

[0041] [Fig. 2B] Figure 2B shows, schematically, a section of the support of Figure 2A;

[0042] [Fig. 3] Figure 3 shows, in the form of a flowchart, the main steps of a manufacturing process according to an exemplary embodiment of the invention;

[0043] [Fig. 4] FIG. 4 schematically represents an example of a correspondence table that can be used during the implementation of the method of FIG. 3,

[0044] [Fig. 5A] FIG. 5A schematically represents a step of selecting the colors of the correspondence table of FIG. 4;

[0045] [Fig. 5B] FIG. 5B schematically represents a step of selecting the colors of the correspondence table of FIG. 4;

[0046] [Fig. 5C] FIG. 5C diagrammatically represents a step of selecting the colors of the correspondence table of FIG. 4;

[0047] [Fig. 5D] FIG. 5D schematically represents a step of selecting the colors of the correspondence table of FIG. 4;

[0048] [Fig. 6A] Figure 6A shows, schematically, an example

arrangement of structural elements created on the support of Figure 2A;

[0049] [Fig. 6B] Figure 6B shows, schematically, a section along AA of the arrangement of structural elements of Figure 6A; [0050] [Fig. 7] FIG. 7 diagrammatically represents an example of a modification sequence that can be used during the implementation of the method of FIG. 3;

[0051] [Fig. 8] Figure 8 shows, schematically, an example of

bar code reader capable of implementing the method of obtaining of Figure 9;

[0052] [Fig. 9] FIG. 9 represents, in the form of a flowchart, the main steps of an obtaining method according to an exemplary embodiment of the invention;

[0053] [Fig. 10A] FIG. 10A represents, schematically, an example of a comparison table that can be used during the implementation of the method of FIG. 9;

[0054] [Fig. 10B] Figure 10B shows, schematically, another

example of a comparison table that can be used during the implementation of the method of FIG. 9;

[0055] [Fig. 1 1] Figure 11 shows, schematically, an example of a safety device according to an exemplary embodiment of the invention;

[0056] [Fig. 12] Figure 12 shows, in the form of a flowchart, the

main steps of an authentication method according to an exemplary embodiment of the invention.

Description of embodiments

The present invention relates to the manufacture of a two-dimensional color bar code 110, also referred to as high density color bar code 110, which can typically take the form of a "datamatrix" type code.

As shown in Figure 1 which shows, schematically, an example of color bar code 1 10, the color bar code 1 10 comprises an arrangement 112 of structural elements 1 14 colored base, this arrangement 1 12 encoding at least one piece of information, typically in a coding part 1 18 of the arrangement, said part possibly being discontinuous. Each piece of information can be digital data relating to the security device on which the bar code 110 is formed, digital data relating to the authorized wearer of the security device (such as a reference biometric characteristic) , or digital data relating to the organization that manufactured (or issued) the security device.

Each basic structural element 1 14 corresponds to an elementary entity of the arrangement 1 12. All the basic structural elements typically have the same geometric shape, for example a triangular, rectangular, hexagonal or square shape.

The arrangement 1 12 of structural elements 1 14 may include one or

several reference sequences 115, each reference sequence 115 being positioned at a different location from the arrangement 112.

Each reference sequence 115 typically comprises an element

basic structural 114 of each different color that may be present on barcode 1 10. Each reference sequence 115 can thus be used by a reader for calibration purposes, as explained below with reference to Figure 9.

In addition, the bar code 1 10 may include marks 116 of

barcode detection and 117 zone detection marks

information, these marks 1 16, 1 17 can also be used when reading the bar code 1 10.

In addition, the bar code 1 10 can include a correction part

of errors 1 19, this part may be discontinuous.

The bar code 1 10 is formed on a support 220 such as for example the support 220 shown in Figures 2A and 2B. The support 220 is typically a substrate comprising a transparent layer 222 and a matrix 224 printed opposite the transparent layer 222, that is to say on one of the faces of the transparent layer 222 or on another layer. 220 positioned opposite the transparent layer 222. The matrix 224 comprises a plurality of pixels 226, each pixel 226 comprising at least two sub-pixels 228 of different colors. Each pixel 226 typically comprises three sub-pixels 228 of different colors, for example the primary colors red, green and blue or yellow, magenta and cyan. Alternatively, each pixel may include four subpixels 228 of different colors, for example yellow, magenta, cyan and white.

[0066] In the example of Figures 2A and 2B, each pixel 226 is square in shape and each sub-pixel 228 is rectangular. Alternatively, the pixels 226 of the array 224 can take the form of another geometric figure, such as a rectangle or a triangle (the subpixels 228 can then also take the form of a triangle).

[0067] In the example of Figures 2A and 2B, the array 224 includes nine pixels.

However, the array 224 can of course include more than nine pixels.

For example, for a matrix 224 of 85.6 mm ^* 26.99 mm which can

typically be used for a security document, the size of a pixel can be (4 ^* 70pm) ² . The maximum number of pixels is then close to 3.10 pixels.

The matrix 224 can be printed on the transparent layer 222 or on an opaque layer 229 of the support 220. The opaque layer 229 is typically white in color.

In addition, in the example of Figures 2A and 2B, the matrix 224 is positioned between the transparent layer 222 and the opaque layer 229 of the support 220. As a variant, the transparent layer can be positioned between the matrix 224 and the opaque layer 229.

As a variant, the support 220 does not include a transparent layer 222.

As a variant, the support 220 comprises a white layer on which is positioned a first transparent layer, the matrix being positioned on the first transparent layer and a second transparent layer being positioned on the matrix.

The support 220 can be integrated into a security device, for example a badge or a security document. The security document can be an identity document such as passport, identity card, driver's license, etc.

The support 220 can thus be a card body or a page of a security document, for example a page of data from a passport. FIG. 3 represents a method of manufacturing a color bar code 110 such as the bar code 110 of FIG. 1, the method being in accordance with an exemplary embodiment of the invention. The manufacturing process is typically implemented by a manufacturing system comprising digital data processing means and a laser beam, typically having a wavelength of 1064 nm.

The data processing means typically take the form of a computer, executing a computer program stored in a computer readable information medium (or memory).

In a step E302, one or more pieces of information are obtained by the data processing means of the manufacturing system.

In order to simplify the remainder of the description, it will be considered hereinafter that a single piece of information is obtained in step E302. However, it will be understood that, for the implementation of the invention, several pieces of information can be obtained at this step E302, then encoded in the color bar code 110 during the implementation of the following steps.

[0079] The piece of information typically takes the form of a digital data group comprising a plurality of digital data subgroups.

[0080] The piece of information is typically obtained from a digital representation of this piece of information, for example from a digital image. Image processing, which depends on the nature of the piece of information, can be performed on the digital image to extract the piece of information.

The information element is, for example, a reference biometric characteristic, typically obtained from a digital image, the

biometric characteristic of reference being able to be used for an authentication of a holder of security document.

The digital image is typically an image or signature of the face, of an iris or of a fingerprint of the holder of the security document. The reference biometric characteristic can thus be a set of particular points of the face, the iris or the fingerprint (these particular points which can be called minutiae in the case of a fingerprint). This set of particular points is chosen so as to reliably represent the authorized bearer of the security document.

Alternatively, the information element is digital data relating to the security device on which the bar code 110 is formed, digital data relating to the user (or carrier) of the security device, or digital data relating to the organization that manufactured (or issued) the security device.

[0084] In a step E304, a set of colored basic structural elements corresponding to the information element obtained in step E302 is determined, by the data processing means of the manufacturing system. This step thus converts the piece of information into a set of colored basic structural elements to be formed on a support in order to create barcode 1 10.

[0085] The determination of the set of structural elements is typically

carried out by means of a first correspondence table, associating each different subgroup of data with a different structural element, of a single color and which may include a single pattern.

Thus, each data subgroup of the information element can be searched for in the first correspondence table, in order to obtain the associated structural element 1 14 and thus to determine the set of structural elements .

Each desired subgroup of data can be obtained after having made a change of digital base at the level of the group of data.

FIG. 4 schematically represents an example of a first correspondence table 400 that can be used in step E304.

This first correspondence table associates sixteen different structural elements 1 14 with sixteen different data sub-groups 402, each different data sub-group 402 corresponding to a different symbol of the hexadecimal base. Also, when the information element is not coded in hexadecimal, it is necessary to perform a digital base change in order to obtain an information element coded in hexadecimal. Element information can then include a group of symbols from the hexadecimal base, each symbol being a data subgroup 402 that can be searched for in the first correspondence table 400.

The color of each structural element 1 14 of the first table 400 is unique, that is to say different from the colors of the other structural elements 1 14 of the first table 400. In addition, each structural element 1 14 of the first table 400 comprises a single pattern 404, that is to say a pattern 404 different from the patterns 404 of the other structural elements 1 14 of the first table 400.

Each color of structural element 1 14 of the correspondence table

that can be used in step E304 is selected so as to be able to be distinguished from the other colors by a camera described below (for example a low-resolution color camera) whose resolution is lower than the resolution necessary for the unitary display d 'a sub-pixel, when reading the color bar code 110, after a step of forming E308 of the structural element 114. This is to minimize the risk of error when reading barcode 1 10.

The color selection of the structural elements 1 14 of the first correspondence table is carried out during a preliminary phase, preceding the use of the first correspondence table, and therefore before step E304. Each color can be defined by varying the gray levels of a plurality of different primary colors (eg, red, green, and blue) forming the pixel matrix. Each primary color has a different position in the visible spectrum.

As shown in Figure 5A, with three gray levels (0; 50; 100) for each primary color R, G, B, it is possible to generate twenty-seven different colors 501. However, some colors may be too close and thus could be sources of error when reading the barcode. The selection for example of sixteen colors among the twenty-seven different colors makes it possible, however, to obtain a bar code four times more compact than a two-dimensional bar code in black and white. The greater the number of colors selected, the greater the data density. [0094] The colors can be selected from a set of colors (for example the set of colors 501 of FIG. 5A) by means of a reference scanner, so that only the colors of the set can be easily differentiated. after being scanned by the reference scanner are selected.

More specifically, during the preliminary color selection phase, for each color of the set, areas of different colors can be defined by the data processing means.

As shown in FIG. 5B, the color zones 502 are for example lines, each line 502 being formed by several basic structural elements 114 of the same color.

[0097] The color zones 502 are then formed on a flat surface such as a sheet. The color areas 502 can be printed, for example by means of an inkjet or laser printer. Alternatively, as shown in Fig. 5C, the color areas 502 can be formed by modifying a flat support having for example the same structure as the support of Figs. 2A and 2B, using a modification sequence 504 based on 502 color areas defined. The modification of the support can be carried out according to the method described below with reference to step E308.

The flat surface is then scanned by the reference scanner, the reference scanner thus obtaining a digital image 506 of the flat surface. The color of each pixel of digital image 506 can then be measured, typically in primary color levels. Figure 5D shows the color of four different pixels i, j, k, and m of digital image 506 in a color space. The color cj of pixel j being too close to the color ck of pixel k (in the figure positioned in a predefined range I of close colors in the RGB primary color space), the color cj of pixel j is not selected and therefore not part of the EC set of final colors that can be used. The selection of the colors can be carried out in a complementary manner using other differentiation parameters such as the geometry of the colored base structural element 1 14 or the position of the colored base structural element 114 in the bar code. . The number of possible combinations of coding by means of the first correspondence table and of the matrix 224 is M ^N combinations where M is the number of different structural elements of the table, and N is the number of locations available on the matrix 224, ie the number of pixels of the matrix 224 which can be used for the encoding of the information element, for example the number of pixels which can be used to form the structural elements of the encoding part 118 of the layout.

[0100] For example, it is considered that all the pixels of the matrix 224 of the

Figures 2A and 2B are used to form the information element. If the first correspondence table of FIG. 4 is used, there are then 16 ⁴ possible coding combinations on this matrix 224.

[0101] Additional structural elements, used to minimize the risk of misreading may be added to the set of colored basic structural elements determined in step E304. These structural elements

additional are for example obtained by using the Reed-Solomon error correction algorithm. In addition, structural elements of the reference sequences can be added to the set.

[0102] The manufacturing process can further include a step E306

obtaining the support 220 on which the bar code 110 can be formed, such as for example the support 220 shown in Figures 2A and 2B. The support 220 is for example manufactured, the manufacture of the support 220 comprising the printing of the matrix 224 on the transparent layer 222 or on the opaque layer 229, and optionally a lamination of the layers of the support 220.

Then, in a step E308, at least one structural element 1 14 of

the set of colored basic structural members is formed on the support 220, to create the arrangement 112 of colored basic structural members 114.

[0104] In this step E308, the arrangement 112 of structural elements 1 14 can be created by forming the structural elements 1 14 of the set determined in step E304, for example according to a predefined path.

The formation of a structural element 114 of the assembly comprises a substep of modifying the support 220 at the level of at least part of at least one sub-pixel 228 of at least one pixel 226. of matrix 224, this modification allowing to obtain the color of the structural element 114, and optionally the pattern 404 of the structural element 114. The modification is typically carried out by means of the laser of the manufacturing system.

Thus, a pixel 226 of the matrix 224 becomes, after modification of the support 220 at the level of at least part of at least one of its subpixels 228, a structural element 1 14 of the arrangement 1 12 .

[0107] The modification is for example an opacification of the transparent layer 222, opposite said at least part of at least one sub-pixel 228, produced by means of the laser beam. For example, for each structural element 114 of the assembly, the laser beam punctually carbonizes the transparent layer 222 so as to form a series of points facing said at least one part in the transparent layer 222 (that is, say between the two external faces of the transparent layer 222), for example two or four points.

The carbonization of the transparent layer 222 facing at least part of a sub-pixel 228 of a pixel 224 generates a gray level at the level of this sub-pixel 228, which makes it possible to obtain the color of structural element 114 created from pixel 226.

[0109] In addition, the carbonization of the transparent layer 222 opposite at least part of a sub-pixel 228 of a pixel 226 makes it possible to obtain the pattern 404 of the structural element 114 created from the pixel 226. For example, the series of dots is formed so as to reproduce the pattern 404 of the structural element 114 as presented by the first table 400.

[0110] The modification of the medium 220 is typically an opacification when the color of the subpixels is achieved by printing technology.

[01 11] Figures 6A and 6B show the support 220 of Figures 2A and 2B on which an arrangement 1 12 of structural elements 1 14 colored base was created during the implementation of step E308.

[01 12] The arrangement 1 12 of Figures 6A and 6B comprises nine structural elements 1 14, arranged along a path Ta. [01 13] The nine structural elements 1 14 were obtained in step E304 by means of the first table 400 of FIG. 4, so that they encode an information element taking the value 1f59ce6b6.

[01 14] As can be seen in these FIGS. 6A and 6B, each sub-pixel 228 can for example be a rectangle which can be divided into three equal parts.

(typically three squares), the laser being able to carbonize the transparent layer 222 so as to form one or more points facing each part (for example two or four points). Of course, other configurations can be considered.

[01 15] The modification may alternatively be an erasure by ablation of said at least part of at least one sub-pixel 228, produced by means of the laser beam. For example, for each structural element 114 of the assembly, the laser beam at least partially erases the color of at least part of at least one subpixel.

[01 16] The modification is typically an erasure by ablation when the color of the sub-pixels is formed by a light diffraction device, for example by means of a hologram.

[01 17] All the structural elements 1 14 of the assembly are for example formed on the support 220 in step E308.

[01 18] Alternatively, the formation of one or more structural elements 1 14 of

the assembly does not require modification of the support 220. Each of these structural elements then does not include a pattern 404, and the color of the element is defined by the subpixels of the associated pixel.

[01 19] In order to guide the laser during the modification of the support 220, for example during the carbonization or the erasure by ablation of the matrix, a sequence of modifications can be used, this sequence comprising all the modifications to be performed on the support 220. This sequence can include all the patterns of all the structural elements 114 to be formed, these patterns being arranged according to the predefined path of the arrangement. Figure 7 shows an example sequence of modifications 700, used to fabricate the bar code of Figure 1. [0120] The color bar code 1 created according to the method of FIG. 3 can then be read in order to obtain the coded information element.

[0121] FIG. 8 schematically shows a color bar code reader 800 in accordance with an exemplary embodiment of the invention, capable of implementing a method of obtaining in accordance with an exemplary embodiment. embodiment, for example the method described with reference to FIG. 9.

[0122] The reader 800 has the conventional architecture of a computer, and can in particular include a processor 802, a read only memory 803 (of the “ROM” type), a rewritable non-volatile memory 804 (of the “EEPROM” or “EEPROM” type. NAND flash ”for example), a rewritable volatile memory 805 (of the“ RAM ”type), a communication interface 806 and / or a sensor 807 of digital images.

[0123] In this example, the read only memory 804 constitutes an information (or recording) medium in accordance with a particular embodiment of

the invention. In the read only memory 804 is stored a computer program P1 allowing the reader 800 to carry out at least part of an obtaining method according to an exemplary embodiment of the invention. As a variant, the computer program P1 is stored in the rewritable non-volatile memory 805. The reader 800 thus comprises data processing means.

[0124] The sensor 807 is typically a low resolution color camera, a grayscale camera, for example at high resolution, or else a scanner.

[0125] The reader 800 may be able to communicate, via the interface of

806 communication and a telecommunications network, with an external electronic device such as a server.

The reader 800 is able to read, by means of the sensor 807, a color bar code 110 in accordance with an exemplary embodiment.

[0127] FIG. 9 represents a process for obtaining at least one element

information encoded in a color bar code 110 manufactured according to the method of FIG. 3, for example the bar code 110 of FIG. 1 or of FIG. 6A. In a step E902, the bar code 110 is read by means of the digital image sensor 807.

When the bar code 110 comprises at least one reference sequence 115, the reading step E902 may include a color calibration of the sensor 707. Indeed, the reference sequence 115 typically comprising a structural element 114 base of each different color that may be present on the color barcode 1 10, this sequence can be used as a template to dynamically calibrate the sensor 807 and to differentiate the colors when reading the color barcode 1 10 .

[0130] This calibration makes it possible to compensate for the variation in transcription of the

color that may occur between two sensors of different types or two sensors of the same type but calibrated differently, or the variation in color transcription by the same sensor but under different lighting conditions (for example lighting conditions not white, which distort colors.

[0131] This calibration also makes it possible to compensate for variations in colors between two different bar codes, due to the production of the bar codes. These color variations are typically due to a variation in the colors of subpixels of the array, a distortion of the array, a variation in laser power or in the position of the modifications made by the laser.

[0132] In a step E906, the reader 800 or more precisely the means of

drive 800 data processing, extract the piece of information from the arrangement 1 12 of colored basic structural elements 1 14.

The extraction is carried out according to the positioning of each structural element 114 in the arrangement 1 12, or more precisely according to the trajectory of the arrangement, as well as according to the color and / or the pattern. 404 of each structural element 114 of the arrangement 1112 encoding the information element, for example each structural element 114 of the coding part 1118.

The color and the pattern 404 of each structural element 114 of the coding part 1 18 can thus be used in combination, when the definition of the sensor 807 allows it. If the definition of sensor 807 is low, only color can be used.

[0135] In fact, reading the color bar code does not require a very efficient camera. But, in the event of a color camera reading failure, it is still possible to get a reading of the 404 patterns by a higher performance grayscale N camera. The patterns 404, isolated, can thus form a “backup” code in the event of failure to read the color bar code.

[0136] More specifically, a second correspondence table can be used in order to search for each structural element 1 14 of the arrangement 1 12 and to determine the corresponding subgroup of data. The subgroups of data are positioned relative to each other according to the positioning of each structural element 114 in the arrangement 1 12, and therefore according to the trajectory of the arrangement.

[0137] In addition, the structural elements 1 14 of the error correction part 1 19 can also be searched in the second correspondence table and then be used to determine the subgroups of data.

[0138] Each structural element 1 14 of the arrangement 1 12 can be searched

in the second correspondence table using the color of structural member 114 and / or the pattern of structural member 114, the color and pattern of structural member 114 encoding the same information.

[0139] The second correspondence table can be the first table of

correspondence used in step E304 of the manufacturing process, or a correspondence table 1002 associating each subgroup of data with the color of each different structural element (see FIG. 10A), or a correspondence table 1004 associating each sub- group of data at pattern 404 of each different structural element (see Figure 10B).

[0140] Indeed, when the sensor 807 is a sensor capable of differentiating colors such as a low-resolution color camera, the color of the structural element obtained during the reading in step E902 is sought in the second correspondence table. When the sensor 807 is a sensor capable of differentiating gray levels such as a gray level camera, the pattern of the structural element obtained during the reading in step E902 is sought in the second table of

correspondence.

[0142] The manufacture of the bar code 110 according to the method of FIG. 3 thus allows the bar code 110 to be readable by several different types of sensors 807.

[0143] The result of step E906, that is to say the information element extracted from

means of the error correcting code and of the arrangement 112, can be used in order to define the next reference sequences to be formed, and thus to refine the detection model, typically when the extraction is carried out within the framework of a training automatic (“machine learning”, in English terminology).

As indicated above, the support 220 on which the color bar code 1 10 created according to the method of FIG. 3 can be integrated into a security device such as a security document 1 1 10 (see FIG. 11). The piece of information encoded by the color bar code may be a biometric reference characteristic characterizing the bearer of the security document, this biometric reference characteristic being able to be used to authenticate the authorized bearer of the security document.

[0145] The reader 800 of FIG. 8 can thus be a document reader of

security capable of implementing an authentication method in accordance with an exemplary embodiment, for example the method described with reference to FIG. 12. The reader 800 then further comprises a biometric sensor 1 1 18, and the program d The computer P1 can allow the reader 800 to implement all or part of the authentication method.

[0146] The biometric sensor 1 1 18 is for example an optical sensor typically capable of obtaining digital images of fingerprints, or a digital still camera or a digital camera typically capable of obtaining digital images of faces and / or iris.

[0147] FIG. 12 represents a method for authenticating a holder of a

security document comprising a color bar code 1 10 manufactured according to method of Figure 3, for example the color bar code 110 of Figure 1 or Figure 6A.

[0148] The bar code 1 10 colors encodes a biometric characteristic of

reference, characterizing the bearer of the security document.

[0149] Steps E902 and E906 of the obtaining method described with reference to FIG. 9 are implemented by the data processing means of reader 800 in order to extract the reference biometric characteristic of bar code 110.

In a step E1208, at least one candidate biometric characteristic, representative of the wearer, is obtained by means of the biometric sensor 1 18.

In order to simplify the remainder of the description, it will be considered hereinafter that a single candidate biometric characteristic is obtained in step E1208. It will be understood, however, that, for the implementation of the invention, several candidate biometric characteristics can be obtained at this step E1208 and then compared with several reference biometric characteristics in step E1210 described below.

In a step E1210, the data processing means of the reader 800 compare the candidate biometric characteristic with the reference biometric characteristic, a correspondence between the characteristic

candidate biometric and the reference biometric characteristic being a condition for successful authentication of the bearer.

[0153] The candidate biometric characteristic typically corresponds to the

reference biometric characteristic if their distance according to a predefined comparison function is less than a predefined threshold.

[0154] In the case where the candidate biometric characteristic corresponds to the

biometric characteristic of reference, the authentication of the bearer is typically successful. In the case where the candidate biometric characteristic does not correspond to the reference biometric characteristic, the authentication of the bearer fails. The arrangement of structural elements 1 14 of the color bar code can further encode at least one piece of information relating to the physical uniqueness of the security document.

This piece of information, which can be called the signature of the security document 1 January 10, is for example coordinates of a set of points with respect to a predetermined reference frame, these coordinates representing a non-physical particularity. clonable or PUF for “Physical unclonable function”, in Anglo-Saxon terminology.

[0157] A non-cloning physical feature is the result of a phenomenon that is easy to implement, this result being impossible to reproduce even under the same operating conditions.

[0158] For example, the coordinates represent a deformation of the security document 1 1 10 due to heat. The manufacturing process of the security document 1 1 10 may include an assembly by thermal input of a first layer with at least a second layer, this thermal input possibly being accompanied by the application of pressure on the layers. The first layer (for example the transparent layer 222) can typically be of thermoplastic polymer material and include a reference pattern, for example the matrix itself, comprising a determined set of points. The reference pattern is typically printed at a sensitive area of the security document, that is to say an area liable to be altered, such as an area comprising information identifying the authorized holder of the security document 1 1 10, for example the photo of the authorized bearer, a hinge of the security document, etc.

[0159] The assembly of the layers leads to a deformation of the first layer and therefore a deformation of the pattern of the first layer, this deformation not being able to be foreseen in advance. The amplitude and orientation differences between the points of the pattern initially printed and those of the pattern obtained after assembly thus form a signature that is impossible to reproduce. The amplitude and orientation deviations can then be detected optically, then stored in the form of coordinates in the arrangement 1 12 of structural elements 114. Thus, the steps E902 and E906 of the obtaining method described with reference to FIG. 9 can also be implemented by the data processing means of the reader 800 in order to extract from the bar code 1 10 the. element

information on the physical uniqueness of the security document.

[0161] In a step E1212, at least one element of physical uniqueness of the document can be detected by a suitable sensor of the reader 800, or a higher resolution reader 800 used by forensics during criminal investigations.

The detected element is typically the coordinates of the points of the determined set of points of the pattern.

Then, in a step E1214, the information element concerning the physical uniqueness of the document is compared with the physical uniqueness element of the document, a correspondence between the information element concerning the physical uniqueness of the document and the element of physical uniqueness of the document being a condition for successful authentication of the bearer.

[0163] In the event that the pattern has been altered following the production of the

security 1 1 10 the document's physical uniqueness information element does not match the security document's physical uniqueness element 1 1 10 and cardholder authentication fails.

In the case where the pattern has not been altered following the production of the security document, the information element concerning the physical uniqueness of the security document 1 1 10 corresponds to the uniqueness element physical security document 1 1 10. The authentication of the bearer is then successful. As a variant, the authentication of the bearer is successful in the event of a match between the information element concerning the physical uniqueness and the physical uniqueness element of the security document 1 1 10, and in the event of a match between the biometric characteristic candidate and the reference biometric characteristic in step E1210.

Claims

[Claim 1] A method of manufacturing a two-dimensional color bar code (110) comprising an arrangement (112) of colored basic structural elements (114) encoding at least one piece of information,

said manufacturing process comprising the following steps:

determination (E304), by data processing means, of a set of colored basic structural elements corresponding to said at least one information element, at least one structural element of

the set comprising a pattern, and

forming (E308) of said at least one structural element of the assembly on a support (220), in order to create the arrangement (112) of colored basic structural elements (114),

in which :

the medium (220) comprises a printed matrix (224) comprising a plurality of pixels (226), each pixel (226) comprising at least two sub-pixels (228) of different colors, and

forming said at least one colored base structural member (114) comprises modifying the medium (220) at at least part of at least one sub-pixel (228) of at least one pixel (226) of the matrix (224), said modification making it possible to obtain the color and the pattern of said at least one basic structural element (114).

[Claim 2] The manufacturing method according to claim 1, wherein said piece of information is a reference biometric characteristic, the method further comprising a step of obtaining (E302) said at least one piece of information from 'a digital representation of said piece of information.

[Claim 3] The manufacturing method according to claim 1 or 2, wherein the support (220) comprises a transparent layer (222), the matrix (224) being printed opposite the transparent layer (222),

the modification being an opacification of the transparent layer (222) in looking at said at least part of at least one sub-pixel (228) of at least one pixel (226) of the matrix (224).

[Claim 4] The manufacturing method according to claim 3, wherein the opacification is carried out by means of a laser beam, the laser beam punctually carbonizing the transparent layer (222) so as to form a series of points facing said at least part of at least one sub-pixel (228).

[Claim 5] The manufacturing method according to claim 1 or 2, wherein the modification is an ablation erasure of said at least part of at least one sub-pixel (228) of a pixel (226) of the array. (224), produced by means of a laser beam, so as to erase at least

partially the color of said at least part of at least one subpixel (228).

[Claim 6] A manufacturing method according to any one of

claims 1 to 5, wherein:

said at least one piece of information takes the form of a group of digital data comprising a plurality of sub-groups of digital data (402),

the determination of a set (112) of colored basic structural elements (114) corresponding to said at least one information element is carried out by means of a correspondence table (400), associating each subgroup of data ( 402) different to a different structural element (114) having a unique color and / or comprising a unique pattern (404).

[Claim 7] The manufacturing method according to claim 6, wherein the color of each structural member (114) different from the lookup table (400) is selected so that it can be distinguished from other colors by a digital image sensor. (807) whose resolution is lower than the resolution necessary for the unit display of a sub-pixel (228), after the forming step.

[Claim 8] Security device (1110) comprising a code to

Two-dimensional color bars (110) produced according to the manufacturing method according to one of claims 1 to 7.

[Claim 9] A method of obtaining at least one piece of information encoded in a two-dimensional color bar code (110) produced according to the manufacturing method according to any one of claims 1 to 7, said obtaining method comprising the following steps:

reading (E902) of said bar code (110) by means of a digital image sensor (807), and

extracting, by data processing means, said piece of information from the arrangement (112) of colored basic structural elements (114), the extraction being performed according to the positioning of each structural element (114 ) in the arrangement (112), as well as depending on the color and / or pattern of each structural element (114) of the arrangement (112).

[Claim 10] The method of obtaining according to claim 9, wherein the arrangement (112) of structural elements (114) comprises a reference sequence comprising a plurality of basic structural elements of different colors, step ( E902) reading comprising a color calibration of the digital image sensor (807), based on said reference sequence.

[Claim 11] A method of authenticating a holder of a security device according to claim 8, comprising a color bar code (110) comprising an arrangement (112) of colored base structural elements (114) encoding the at least one reference biometric characteristic, said method comprising the following steps:

obtaining said at least one reference biometric characteristic according to the obtaining method according to claim 9 or 10,

obtaining (E1208) of at least one candidate biometric characteristic, representative of the wearer by means of a biometric sensor, comparison (E1210), by data processing means, of said at least one candidate biometric characteristic with said at least one reference biometric characteristic, a correspondence between said at least one candidate biometric characteristic and said at least a reference biometric characteristic being a condition for successful authentication of the bearer.

[Claim 12] An authentication method according to claim 11, wherein said at least one candidate biometric characteristic corresponds to said at least one reference biometric characteristic if their distance according to a predefined comparison function is less than a predefined threshold.

[Claim 13] An authentication method according to claim 11 or 12, wherein the arrangement (112) of structural elements (114) of the two-dimensional color bar code (110) further encodes at least one piece of information relating to the physical uniqueness of the document,

the method further comprising the following steps:

extraction of said at least one piece of information relating to the physical uniqueness of the document,

detection (E1212) of at least one element of physical uniqueness of the document,

comparison (E1214) of said at least one item of information relating to the physical uniqueness of the document and said at least one item of physical uniqueness of the document, a correspondence between said at least one item of information relating to the physical uniqueness of the document and said at least one element of physical uniqueness of the document being a condition for successful authentication of the bearer.