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

Abstract

The invention essentially relates to a method for manufacturing a two-dimensional color barcode comprising an arrangement of colored basic structural elements encoding at least one piece of information, said manufacturing method comprising the following steps: - determination (E304), 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 - formation (E308) of said at least one structural element of the set on a support, in order to create the arrangement, in which: - the support comprises a matrix comprising a plurality of pixels (226), each pixel (226) comprising at least two sub-pixels (228) of different colors,the color being formed by a light diffraction device and - the formation of said at least one colored basic structural element comprises a modification of the medium at the level of at least a part of at least one sub-pixel of at least one pixel of the matrix, said modification enabling the color and pattern of said at least one basic structural element to be obtained.

Description

Technical Field

[0001] The present invention relates to the field of two-dimensional bar codes, and more particularly concerns the manufacture of a two-dimensional color bar code.

[0002] The invention applies non-exclusively to security devices of the identity document type, such as passports, identity cards, driving licenses, etc. Prior art

[0003] WO2011 / 124774 A1 describes laser carbonization of pixels of different colors to obtain an image. FR 2 971 972 A describes laser carbonization of a layer above pixels of different colors to obtain an image. US 2005 / 001419 A1 describes laser revelation of pixels of different colors, either by making holes in a layer above the pixels or by ablation of parts of pixels when the pixels are in different layers, to obtain an image. DE 10 2012 211767 A1 describes similar techniques to the three previous documents, specifically selective demetallization to laser reveal pixels of different colors (some sub-pixels being deactivated by the laser), the color of the pixels can be formed by light diffraction devices.None of these four documents describes that the resulting image is a two-dimensional color barcode.

[0004] As is known, authentication of a security document holder can be achieved by comparing reference biometric characteristics stored in the security document with candidate biometric characteristics of the holder, obtained by means of a biometric data sensor.

[0005] Due to their large size and security issues, the reference characteristics are stored in a memory of an electronic chip in the security document.

[0006] 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 costly.

[0007] The invention aims to overcome this problem and more generally aims to store, in a secure and environmentally friendly manner, a large quantity of data, such as biometric characteristics, in a security device. Statement of the invention

[0008] The present invention relates to a method of manufacturing a two-dimensional color barcode comprising an arrangement of colored basic structural elements encoding at least one information element, said manufacturing method comprising the following steps: determining, by data processing means, 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 said at least one structural element of the set on a support, in order to create the arrangement of colored basic structural elements, wherein: the support comprises a matrix comprising a plurality of pixels, each pixel comprising at least two sub-pixels of different colors, the color being formed by a light diffraction device and forming said at least one colored basic structural element comprises modifying the support at least a portion 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.

[0009] The invention makes it possible to encode and therefore store in the barcode a large quantity of information on a limited surface, for example part of the surface of a security document.

[0010] Indeed, the use of colors in the barcode allows much more data to be encoded than a two-dimensional black and white barcode of the same size, i.e. a two-dimensional barcode in which each basic structural element is either entirely black or entirely white. The data density, i.e. the amount of data (in bytes) stored per unit area (in square millimeter) of such a two-dimensional black and white barcode is indeed less than 1 byte per square millimeter, while the invention allows a higher data density, typically at least 4 bytes per square millimeter.

[0011] In addition, the technique of creating the layout allows for secure storage of the information element in the barcode. Indeed, the layout cannot be modified without altering the barcode support, unlike traditional barcode printing techniques (inkjet, screen printing or offset for example), making it possible to print another barcode over the initially formed barcode.

[0012] Furthermore, since the basic structural element encodes a piece of information by its color and pattern, it is possible to read the barcode using several different types of sensors, such as a standard color sensor or a grayscale sensor.

[0013] 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 information element.

[0014] Thanks to the increased data density that the color barcode offers, it is possible to store a sufficient quantity of reference biometric characteristics to allow reliable authentication of the bearer of a security document comprising the barcode, i.e. a sufficient quantity of biometric characteristics to allow a comparison between the reference biometric characteristics and the candidate biometric characteristics verifying the compromise between acceptable false rejection rates (FRR) and false acceptance rates (FAR).

[0015] The invention makes it possible, for example, to encode an identity photo of at least 10 kilobytes, which allows facial comparison algorithms to function correctly.

[0016] In a particular embodiment, the support comprises a transparent layer, the matrix being printed opposite the transparent layer, the modification being an opacification of the transparent layer opposite said at least one part of at least one sub-pixel of at least one pixel of the matrix or alternatively an erasure by ablation of at least one part of at least one sub-pixel, or a combination of opacification and erasure by ablation.

[0017] The formation of the structural element thus uses precise technology, making it possible to form the arrangement of colored basic structural elements without the risk of smudging, unlike conventional barcode printing technologies.

[0018] In addition, the arrangement creation technique allows for secure storage of the information element in the barcode. Indeed, since the arrangement is made at the level of two different layers or in different thickness levels of the same layer, it cannot be modified without altering the barcode support.

[0019] In a particular embodiment, the opacification is carried out by means of a laser beam, the laser beam punctually carbonizing the transparent layer so as to form a series of points opposite said at least one part of at least one sub-pixel.

[0020] In a particular embodiment, the modification is an erasure by ablation of said at least one part of at least one sub-pixel of a pixel of the matrix, carried out by means of a laser beam, so as to at least partially erase the color of said at least one part of at least one sub-pixel.

[0021] The formation of the structural element thus uses precise technology, making it possible to form the arrangement of colored basic structural elements without the risk of smudging, unlike conventional barcode printing technologies.

[0022] Additionally, the layout creation technique allows for secure storage of the information element in the barcode. Indeed, the layout cannot be changed without altering the barcode medium.

[0023] In a particular embodiment: said at least one information element takes the form of a group of digital data comprising a plurality of subgroups of digital data, the determination of a set of colored basic structural elements corresponding to said at least one information element is carried out by means of a correspondence table, associating each different subgroup of data with a different structural element of unique color and / or comprising a unique pattern.

[0024] In a particular embodiment, the color of each different structural element of the look-up table is selected so as to be able to be differentiated from the other colors by a digital image sensor whose resolution is lower than the resolution necessary for the unitary visualization of a sub-pixel, after the training step.

[0025] The invention further relates to a security device comprising a two-dimensional color bar code manufactured according to the manufacturing method as described above.

[0026] The invention further relates to a method for obtaining at least one information element encoded in a two-dimensional color barcode manufactured according to the manufacturing method as described above, said obtaining method comprising the following steps: reading said barcode by means of a digital image sensor, and extracting, by data processing means, said information element from the arrangement of colored basic structural elements, the extraction being carried out as a function of the positioning of each structural element in the arrangement, as well as as a function of the color and / or pattern of each structural element of the arrangement.

[0027] 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.

[0028] The invention also relates to a method for authenticating a wearer of a security device as described above, comprising a color barcode comprising an arrangement of colored basic structural elements encoding 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 as described above, obtaining at least one candidate biometric characteristic, representative of the carrier 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 carrier.

[0029] 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.

[0030] In a particular embodiment, the arrangement of structural elements of the two-dimensional color barcode further encodes at least one piece of information regarding the physical uniqueness of the document, the method further comprising the following steps: extraction of said at least one element 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 element of information concerning the physical uniqueness of the document and of said at least one element of physical uniqueness of the document, a correspondence between said at least one element of information concerning 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.

[0031] In a particular embodiment, the different steps of the obtaining method and / or the authentication method as described above are determined by computer program instructions.

[0032] 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 the authentication method as described above.

[0033] This program may use any programming language, and may be in the form of source code, object code, or code intermediate between source code and object code, such as in a specially compiled form, or in any other desirable form.

[0034] In a particular embodiment, when the computer program comprises 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, and thus make it possible to obtain a digital image of the bar code or of at least part of the bar code.

[0035] The invention also relates to an information medium (or recording medium) readable by a server or more generally by a computer, and comprising instructions of a computer program as mentioned above.

[0036] The information medium may be any entity or device capable of storing the program. For example, the medium may include a storage medium, such as a rewritable non-volatile memory (such as "EEPROM" or "NAND Flash" for example), or such as a "ROM", for example a "CD ROM" or a microelectronic circuit "ROM", or a magnetic recording medium, for example a floppy disk or a hard disk.

[0037] On the other hand, the information carrier may be a transmissible carrier such as an electrical or optical signal, which may be conveyed via an electrical or optical cable, by radio or by other means. The program according to the invention may in particular be downloaded from a network such as the Internet.

[0038] Alternatively, the information carrier may be an integrated circuit in which the program is incorporated, the circuit being adapted to perform or to be used in the performance of the method in question. Brief description of the drawings

[0039] Other characteristics and advantages of the present invention will emerge from the description given below, with reference to the appended drawings which illustrate an exemplary embodiment thereof without any limiting character. In the figures: [ Fig. 1 ] There figure 1 schematically represents an example of a bar code that can be manufactured using the process of the figure 3 ; [ Fig. 2A ] There figure 2A schematically represents a top view of an example of a support that can be used when implementing the method of the figure 3 ; [ Fig. 2B ] There figure 2B schematically represents a section of the support of the figure 2A ; [ Fig. 3 ] There figure 3 represents, in the form of a flowchart, the main steps of a manufacturing process in accordance with an exemplary embodiment of the invention; [ Fig. 4 ] There figure 4 schematically represents an example of a correspondence table that can be used when implementing the method of the figure 3 , [ Fig. 5A ] There figure 5A schematically represents a step in the selection of colors from the correspondence table of the figure 4 ; [ Fig. 5B ] There figure 5B schematically represents a step in the selection of colors from the correspondence table of the figure 4 ; [ Fig. 5C ] There figure 5C schematically represents a step in the selection of colors from the correspondence table of the figure 4 ; [ Fig. 5D ] There figure 5D schematically represents a step in the selection of colors from the correspondence table of the figure 4 ; [ Fig. 6A ] There figure 6A schematically represents an example of an arrangement of structural elements created on the support of the figure 2A ; [ Fig. 6B ] There figure 6B schematically represents a section along AA of the arrangement of structural elements of the figure 6A ; [ Fig. 7 ] There figure 7 schematically represents an example of a modification sequence that can be used when implementing the method of the figure 3 ; [ Fig. 8 ] There figure 8 schematically represents an example of a barcode reader capable of implementing the method of obtaining the figure 9 ; [ Fig. 9 ] There figure 9 represents, in the form of a flowchart, the main steps of a production process in accordance with an exemplary embodiment of the invention; [ Fig. 10A ] There figure 10A schematically represents an example of a comparison table that can be used when implementing the method of the figure 9 ; [ Fig. 10B ] There figure 10B schematically represents another example of a comparison table that can be used when implementing the method of the figure 9 ; [ Fig. 11 ] There figure 11 schematically represents an example of a safety device in accordance with an example embodiment of the invention; [ Fig. 12 ] There figure 12 represents, in the form of a flowchart, the main steps of an authentication method in accordance with an exemplary embodiment of the invention. Description of the embodiments

[0040] The present invention relates to the manufacture of a two-dimensional 110 color bar code, also known as a high-density 110 color bar code, which can typically take the form of a "datamatrix" type code.

[0041] As shown in the figure 1 which schematically represents an example of a color barcode 110, the color barcode 110 comprises an arrangement 112 of colored basic structural elements 114, this arrangement 112 encoding at least one information element, typically in a coding part 118 of the arrangement, said part possibly being discontinuous.

[0042] Each piece of information may be digital data relating to the security device on which the barcode 110 is formed, digital data relating to the authorized bearer of the security device (such as a reference biometric characteristic), or digital data relating to the organization that manufactured (or issued) the security device.

[0043] Each basic structural element 114 corresponds to an elementary entity of the arrangement 112. All the basic structural elements typically have the same geometric shape, for example a triangular, rectangular, hexagonal or square shape.

[0044] The arrangement 112 of structural elements 114 may comprise one or more reference sequences 115, each reference sequence 115 being positioned at a different location in the arrangement 112.

[0045] Each reference sequence 115 typically comprises a basic structural element 114 of each different color that may be present on the barcode 110. Each reference sequence 115 can thus be used by a reader for calibration purposes, as explained below with reference to the figure 9 .

[0046] Furthermore, the bar code 110 may include bar code detection marks 116 and information area detection marks 117, these marks 116, 117 may also be used when reading the bar code 110.

[0047] In addition, the bar code 110 may include an error correction portion 119, this portion possibly being discontinuous.

[0048] The bar code 110 is formed on a support 220 such as, for example, the support 220 shown in figures 2A et 2B .The support 220 is typically a substrate comprising a transparent layer 222 and a matrix 224 printed opposite the transparent layer 222, i.e. 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 comprise four sub-pixels 228 of different colors, for example yellow, magenta, cyan and white.

[0049] In the example of the figures 2A et 2B , each pixel 226 is square in shape and each sub-pixel 228 is rectangular in shape. Alternatively, the pixels 226 of the matrix 224 may take the shape of another geometric figure, such as a rectangle or a triangle (the sub-pixels 228 may then also take the shape of a triangle).

[0050] In the example of the figures 2A et 2B , the matrix 224 comprises nine pixels. However, the matrix 224 can of course comprise more than nine pixels.

[0051] For example, for a 224 matrix of 85.6 mm * 26.99 mm that can typically be used for a security document, the size of a pixel can be (4*70µm) 2< . The maximum number of pixels is then close to 3.10^4 pixels.

[0052] The matrix 224 may 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.

[0053] Furthermore, in the example of the figures 2A et 2B , the matrix 224 is positioned between the transparent layer 222 and the opaque layer 229 of the support 220. Alternatively, the transparent layer can be positioned between the matrix 224 and the opaque layer 229.

[0054] Alternatively, the support 220 does not include a transparent layer 222.

[0055] Alternatively, the support 220 comprises a white layer on which a first transparent layer is positioned, the matrix being positioned on the first transparent layer and a second transparent layer being positioned on the matrix.

[0056] The holder 220 may be integrated into a security device, for example a badge or a security document. The security document may be an identity document such as a passport, an identity card, a driver's license, etc.

[0057] The support 220 can thus be a card body or a page of a security document, for example a data page of a passport.

[0058] There figure 3 represents a method of manufacturing a color 110 bar code such as the 110 bar code of the figure 1 , the method being in accordance with an exemplary embodiment of the invention. The manufacturing method is typically implemented by a manufacturing system comprising digital data processing means and a laser beam, typically having a wavelength of 1064 nm.

[0059] The data processing means typically take the form of a computer, executing a computer program stored in a computer-readable information medium (or memory).

[0060] In a step E302, one or more pieces of information are obtained by the data processing means of the manufacturing system.

[0061] In order to simplify the remainder of the description, it will be considered subsequently that a single piece of information is obtained at step E302. It will be understood, however, that, for the implementation of the invention, several pieces of information may be obtained at this step E302, then coded in the color barcode 110 during the implementation of the following steps.

[0062] The information element typically takes the form of a group of digital data comprising a plurality of subgroups of digital data.

[0063] The information element is typically obtained from a digital representation of that information element, for example from a digital image. Image processing, which depends on the nature of the information element, may be performed on the digital image in order to extract the information element.

[0064] The information element is for example a reference biometric characteristic, typically obtained from a digital image, the reference biometric characteristic being capable of being used for authentication of a security document holder.

[0065] The digital image is typically an image or signature of the face, iris, or fingerprint of the bearer of the security document. The reference biometric characteristic may thus be a set of particular points on the face, iris, or fingerprint (these particular points may 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.

[0066] 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 wearer) of the security device, or digital data relating to the organization having manufactured (or issued) the security device.

[0067] 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 makes it possible to convert the information element into a set of colored basic structural elements to be formed on a support in order to create the bar code 110.

[0068] 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 unique color and possibly comprising a unique pattern.

[0069] Thus, each subgroup of data of the information element can be searched in the first correspondence table, in order to obtain the associated structural element 114 and thus to determine the set of structural elements.

[0070] Each searched data subgroup can be obtained after performing a numerical base change at the data group level.

[0071] There figure 4 schematically represents an example of a first correspondence table 400 which can be used in step E304.

[0072] This first correspondence table associates sixteen different structural elements 114 with sixteen different data subgroups 402, each different data subgroup 402 corresponding to a different symbol of the hexadecimal base. Also, when the information element is not encoded in hexadecimal, it is necessary to carry out a change of numerical base in order to obtain an information element encoded in hexadecimal. The information element can then comprise a group of symbols of the hexadecimal base, each symbol being a data subgroup 402 which can be searched in the first correspondence table 400.

[0073] The color of each structural element 114 of the first table 400 is unique, i.e. different from the colors of the other structural elements 114 of the first table 400. Furthermore, each structural element 114 of the first table 400 comprises a unique pattern 404, i.e. a pattern 404 different from the patterns 404 of the other structural elements 114 of the first table 400.

[0074] Each structural element color 114 of the correspondence table that can be used in step E304 is selected so as to be able to be differentiated 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 visualization of a sub-pixel, during a reading of the color bar code 110, after a step E308 of forming the structural element 114. This makes it possible to minimize the risk of error when reading the bar code 110.

[0075] The selection of the colors of the structural elements 114 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 (for example the colors red, green and blue) forming the pixel matrix. Each primary color has a different position in the visible spectrum.

[0076] As shown in the 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. Selecting, for example, sixteen colors from the twenty-seven different colors, however, makes it possible to obtain a barcode four times more compact than a two-dimensional black and white barcode. The greater the number of colors selected, the greater the data density.

[0077] Colors can be selected from a color set (e.g. color set 501 of the figure 5A ) using a reference scanner, so that only those colors from the set that can be easily differentiated after being scanned by the reference scanner are selected.

[0078] More specifically, during the preliminary color selection phase, for each color in the set, different color areas can be defined by data processing means.

[0079] As shown in the figure 5B , the color zones 502 are for example lines, each line 502 being formed by several basic structural elements 114 of the same color.

[0080] The color areas 502 are then formed on a flat surface such as a sheet. The color areas 502 may be printed, for example, using an inkjet or laser printer. Alternatively, as shown in figure 5C , the color areas 502 can be formed by modifying a flat support having for example the same structure as the support of the figures 2A et 2B , using a modification sequence 504 based on the defined color areas 502. The modification of the support can be carried out according to the method described below with reference to step E308.

[0081] The planar surface is then scanned by the reference scanner, the reference scanner thereby obtaining a digital image 506 of the planar surface. The color of each pixel of the digital image 506 can then be measured, typically in primary color levels. The figure 5D represents the color of four different pixels i, j, k and m of the digital image 506 in a color space. Since the color cj of pixel j is too close to the color ck of pixel k (in the figure positioned in a predefined interval I of close colors in the RGB primary color space), the color cj of pixel j is not selected and is therefore not part of the set EC of final colors that can be used. The color selection can be carried out in a complementary manner using other differentiation parameters such as the geometry of the colored basic structural element 114 or the position of the colored basic structural element 114 in the barcode.

[0082] The number of possible coding combinations using the first correspondence table and the matrix 224 is MN< 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, i.e. the number of pixels of the matrix 224 that can be used for coding the information element, for example the number of pixels that can be used to form the structural elements of the coding part 118 of the arrangement.

[0083] For example, we consider that all the pixels of the 224 matrix of the figures 2A et 2B are used to form the information element. If we use the first correspondence table of the figure 4 , there are then 16 4< possible coding combinations on this 224 matrix.

[0084] Additional structural elements, used to minimize the risk of reading errors, may be added to the set of colored basic structural elements determined in step E304. These additional structural elements are, for example, obtained using the Reed-Solomon error correction algorithm. In addition, the structural elements of the reference sequences may be added to the set.

[0085] The manufacturing method may further comprise a step E306 of obtaining the support 220 on which the bar code 110 can be formed, such as for example the support 220 shown in figures 2A et 2B The support 220 is for example manufactured, the manufacturing of the support 220 comprising the printing of the matrix 224 on the transparent layer 222 or on the opaque layer 229, and possibly a lamination of the layers of the support 220.

[0086] Then, in a step E308, at least one structural element 114 of the set of colored basic structural elements is formed on the support 220, in order to create the arrangement 112 of colored basic structural elements 114.

[0087] In this step E308, the arrangement 112 of structural elements 114 can be created by forming the structural elements 114 of the assembly determined in step E304, for example according to a predefined trajectory.

[0088] The formation of a structural element 114 of the assembly comprises a sub-step of modifying the support 220 at least a portion of at least one sub-pixel 228 of at least one pixel 226 of the matrix 224, this modification making it possible to obtain the color of the structural element 114, and possibly the pattern 404 of the structural element 114. The modification is typically carried out using the laser of the manufacturing system.

[0089] Thus, a pixel 226 of the matrix 224 becomes, after modification of the support 220 at the level of at least a part of at least one of its sub-pixels 228, a structural element 114 of the arrangement 112.

[0090] The modification is for example an opacification of the transparent layer 222, opposite said at least one part of at least one sub-pixel 228, carried out 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 opposite said at least one part in the transparent layer 222 (i.e. between the two external faces of the transparent layer 222), for example two or four points.

[0091] Carbonization of the transparent layer 222 opposite at least a portion of a sub-pixel 228 of a pixel 224 generates a gray level at this sub-pixel 228, which makes it possible to obtain the color of the structural element 114 created from the pixel 226.

[0092] In addition, carbonizing the transparent layer 222 opposite at least a portion 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 points is formed so as to reproduce the pattern 404 of the structural element 114 as presented by the first table 400.

[0093] The modification of the 220 support is typically an opacification when the color of the subpixels is achieved using printing technology.

[0094] THE figures 6A et 6B represent the support 220 of the figures 2A et 2B on which an arrangement 112 of colored basic structural elements 114 was created during the implementation of step E308.

[0095] The 112 layout of the figures 6A et 6B comprises nine structural elements 114, arranged along a trajectory Ta.

[0096] The nine structural elements 114 were obtained in step E304 by means of the first table 400 of the figure 4 , so that they encode an information element taking the value 1f59ce6b6.

[0097] As visible on these figures 6A et 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 opposite each part (for example two or four points). Of course, other configurations can be envisaged.

[0098] The modification may alternatively be an erasure by ablation of said at least one part of at least one sub-pixel 228, carried out 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 one part of at least one sub-pixel.

[0099] The modification is typically an ablation erasure where the color of the subpixels is formed by a light diffraction device, for example using a hologram.

[0100] All the structural elements 114 of the assembly are for example formed on the support 220 in step E308.

[0101] Alternatively, the formation of one or more structural elements 114 of the assembly does not require modification of the support 220. Each of these structural elements then does not comprise a pattern 404, and the color of the element is defined by the sub-pixels of the associated pixel.

[0102] In order to guide the laser when modifying the support 220, for example when carbonizing or erasing by ablation of the matrix, a sequence of modifications can be used, this sequence comprising all the modifications to be carried out on the support 220. This sequence can comprise all the patterns of all the structural elements 114 to be formed, these patterns being arranged according to the predefined trajectory of the arrangement. figure 7 shows an example of a 700 edit sequence, used to make the barcode of the figure 1 .

[0103] The 110 color barcode created using the process of figure 3 can then be read to obtain the encoded information element.

[0104] There figure 8 schematically represents a color barcode reader 800 according to an exemplary embodiment of the invention, capable of implementing a method of obtaining according to an exemplary embodiment, for example the method described with reference to the figure 9 .

[0105] The reader 800 has the conventional architecture of a computer, and may in particular comprise a processor 802, a read-only memory 803 (of the “ROM” type), a rewritable non-volatile memory 804 (of the “EEPROM” or “NAND Flash” type for example), a rewritable volatile memory 805 (of the “RAM” type), a communication interface 806 and / or a digital image sensor 807.

[0106] 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 implement at least part of a obtaining method in accordance with an exemplary embodiment of the invention. Alternatively, the computer program P1 is stored in the rewritable non-volatile memory 805. The reader 800 thus comprises data processing means.

[0107] The 807 sensor is typically a low-resolution color camera, a high-resolution grayscale camera, for example, or a scanner.

[0108] The reader 800 may be able to communicate, via the communication interface 806 and a telecommunications network, with an external electronic device such as a server.

[0109] The reader 800 is capable of reading, by means of the sensor 807, a color bar code 110 in accordance with an exemplary embodiment.

[0110] There figure 9 represents a method of obtaining at least one piece of information coded in a 110 color bar code manufactured according to the method of the figure 3 , for example barcode 110 of the figure 1 or of the figure 6A .

[0111] In a step E902, the bar code 110 is read by means of the digital image sensor 807.

[0112] When the bar code 110 comprises at least one reference sequence 115, the reading step E902 may comprise a color calibration of the sensor 707. Indeed, the reference sequence 115 typically comprising a basic structural element 114 of each different color that may be present on the color bar code 110, this sequence may be used as a model in order to dynamically calibrate the sensor 807 and differentiate the colors when reading the color bar code 110.

[0113] This calibration makes it possible to compensate for the variation in color transcription that can 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 in different lighting conditions (for example, non-white lighting conditions, which distort the colors.

[0114] This calibration also allows for compensating for color variations between two different barcodes, due to the manufacturing of the barcodes. These color variations are typically due to a variation in the sub-pixel colors of the matrix, a deformation of the matrix, a variation in the laser power or the position of the modifications made by the laser.

[0115] In a step E906, the reader 800 or more precisely the data processing means of the reader 800, extract the information element from the arrangement 112 of colored basic structural elements 114.

[0116] The extraction is carried out as a function of the positioning of each structural element 114 in the arrangement 112, or more precisely as a function of the trajectory of the arrangement, as well as as a function of the color and / or pattern 404 of each structural element 114 of the arrangement 112 encoding the information element, for example each structural element 114 of the coding part 118.

[0117] The color and pattern 404 of each structural element 114 of the coding part 118 can thus be used in combination, when the definition of the sensor 807 allows it. If the definition of the sensor 807 is low, only the color can be used.

[0118] Indeed, reading the color barcode does not require a high-performance camera. However, in the event of a color camera reading failure, it is always possible to obtain a reading of the 404 patterns by a more powerful grayscale N camera. The 404 patterns, isolated, can thus form a "backup" code in the event of a color barcode reading failure.

[0119] More specifically, a second lookup table may be used to search for each structural element 114 of the arrangement 112 and determine the corresponding data subgroup. The data subgroups are positioned relative to each other according to the positioning of each structural element 114 in the arrangement 112, and thus according to the trajectory of the arrangement.

[0120] Furthermore, the structural elements 114 of the error correction part 119 can also be looked up in the second correspondence table and then used to determine the data subgroups.

[0121] Each structural element 114 of the arrangement 112 can be looked up in the second lookup table using the color of the structural element 114 and / or the pattern of the structural element 114, the color and the pattern of the structural element 114 encoding the same information.

[0122] The second correspondence table may be the first correspondence table used in step E304 of the manufacturing method, or a correspondence table 1002 associating each subgroup of data with the color of each different structural element (see figure 10A ) , or a 1004 correspondence table associating each subgroup of data with the 404 pattern of each different structural element (see figure 10B ).

[0123] 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 reading in step E902 is searched for in the second correspondence table.

[0124] When the sensor 807 is a sensor capable of differentiating gray levels such as a gray-scale camera, the pattern of the structural element obtained during reading in step E902 is searched in the second correspondence table.

[0125] The production of the 110 bar code using the process of figure 3 thus allows the bar code 110 to be readable by several different types of sensors 807.

[0126] The result of step E906, i.e. the information element extracted by means of the error-correcting code and the arrangement 112, can be used to define the next reference sequences to be trained, and thus refine the detection model, typically when the extraction is carried out within the framework of automatic learning (“machine learning”, in English terminology).

[0127] As indicated above, the support 220 on which the color bar code 110 created according to the method of the figure 3 can be integrated into a security device such as a 1110 security document (see figure 11 ). The information element encoded by the color barcode may be a reference biometric characteristic characterizing the bearer of the security document, this reference biometric characteristic being able to be used to authenticate the authorized bearer of the security document.

[0128] The 800 reader of the figure 8 can thus be a security document reader capable of implementing an authentication method in accordance with an exemplary embodiment, for example the method described with reference to the figure 12 The reader 800 then further comprises a biometric sensor 1118, and the computer program P1 can allow the reader 800 to implement all or part of the authentication method.

[0129] The biometric sensor 1118 is for example an optical sensor typically capable of obtaining digital images of fingerprints, or a digital photographic device or a digital camera typically capable of obtaining digital images of faces and / or irises.

[0130] There figure 12 represents a method of authenticating a bearer of a security document comprising a 110 color bar code manufactured according to the method of the figure 3 , for example the 110 color barcode of the figure 1 or of the figure 6A .

[0131] The 110-color barcode encodes a reference biometric characteristic, characterizing the bearer of the security document.

[0132] Steps E902 and E906 of the production process described with reference to the figure 9 are implemented by the data processing means of the reader 800 in order to extract the reference biometric characteristic of the bar code 110.

[0133] In a step E1208, at least one candidate biometric characteristic, representative of the wearer, is obtained by means of the biometric sensor 118.

[0134] In order to simplify the remainder of the description, it will be considered subsequently that a single candidate biometric characteristic is obtained in step E1208. It will however be understood that, for the implementation of the invention, several candidate biometric characteristics can be obtained in this step E1208 and then compared to several reference biometric characteristics in step E1210 described below.

[0135] 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 candidate biometric characteristic and the reference biometric characteristic being a condition for successful authentication of the bearer.

[0136] The candidate biometric feature typically matches the reference biometric feature if their distance according to a predefined comparison function is less than a predefined threshold.

[0137] If the candidate biometric feature matches the reference biometric feature, bearer authentication is typically successful. If the candidate biometric feature does not match the reference biometric feature, bearer authentication fails.

[0138] The arrangement of structural elements 114 of the color barcode may further encode at least one piece of information regarding the physical uniqueness of the security document.

[0139] This information element, which can be called the signature of the security document 1110, is for example the coordinates of a set of points relative to a predetermined reference frame, these coordinates representing a physical unclonable feature or PUF for “Physical unclonable function”, in Anglo-Saxon terminology.

[0140] An unclonable 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.

[0141] For example, the coordinates represent a deformation of the security document 1110 due to heat. The method for manufacturing the security document 1110 may comprise an assembly by thermal input of a first layer with at least one 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) may typically be made of thermoplastic polymer material and comprise 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, i.e. an area likely to be altered, such as an area comprising information identifying the authorized bearer of the security document 1110, for example the photo of the authorized bearer, a hinge of the security document, etc.

[0142] 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 predicted in advance. The differences in amplitude and orientation between the points of the initially printed pattern and those of the pattern obtained after assembly thus form a signature that is impossible to reproduce. The differences in amplitude and orientation can then be detected optically, then stored in the form of coordinates in the arrangement 112 of structural elements 114.

[0143] Thus, steps E902 and E906 of the obtaining process described with reference to the figure 9 can also be implemented by the data processing means of the reader 800 in order to extract from the bar code 110 the information element concerning the physical uniqueness of the security document.

[0144] In a step E1212, at least one element of physical uniqueness of the document may be detected by a suitable sensor of the reader 800, or a higher resolution reader 800 used by forensic science during criminal investigations. The detected element is typically the coordinates of the points of the determined set of points of the pattern.

[0145] 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 physical uniqueness element of the document being a condition for successful authentication of the bearer.

[0146] In the event that the pattern has been altered following the manufacture of the security document 1110, the information element concerning the physical uniqueness of the document does not correspond to the physical uniqueness element of the security document 1110 and the authentication of the bearer fails.

[0147] 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 1110 corresponds to the physical uniqueness element of the security document 1110. The authentication of the bearer is then successful. Alternatively, the authentication of the bearer is successful in the event of correspondence between the information element concerning the physical uniqueness and the physical uniqueness element of the security document 1110, and in the event of correspondence between the candidate biometric characteristic and the reference biometric characteristic in step E1210.

Claims

1. A method for manufacturing a two-dimensional coloured bar code (110) comprising an arrangement (112) of coloured base structural elements (114) encoding at least one information element, said manufacturing method comprising the following steps: - determining (E304), by data processing means, a set of coloured base structural elements corresponding to said at least one information element, at least one structural element of the set comprising a pattern, and - forming (E308) said at least one structural element of the set on a support (220), in order to create the arrangement (112) of coloured base structural elements (114), wherein: - the support (220) comprises an array (224) comprising a plurality of pixels (226), each pixel (226) comprising at least two sub-pixels (228) of different colours, the colour being formed by a light diffraction device and - the formation of said at least one coloured base structural element (114) comprises a modification of the support (220) on at least one part of at least one sub-pixel (228) of at least one pixel (226) of the array (224), said modification making it possible to obtain the colour and pattern of said at least one base structural element (114).

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

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

4. The manufacturing method of claim 2, wherein the support (220) comprises a transparent layer (222), the array (224) facing the transparent layer (222), the modification being an opacification of the transparent layer (222) facing said at least one part of at least one sub-pixel (228) of at least one pixel (226) of the array (224).

5. The manufacturing method according to claim 4, wherein the opacification is carried out by means of a laser beam, the laser beam carbonising the transparent layer (222) in a localised manner so as to form a series of dots facing said at least one part of at least one sub-pixel (228).

6. The manufacturing method according to any one of claims 1 to 5, wherein: said at least one information element takes the form of a digital data group comprising a plurality of digital data subgroups (402), determining a set (112) of coloured base structural elements (114) corresponding to said at least one information element is carried out by means of a correspondence table (400), associating each different data subgroup (402) with a different structural element (114) of a unique colour and / or comprising a unique pattern (404).

7. The manufacturing method according to claim 6, wherein the colour of each different structural element (114) of the correspondence table (400) is selected so as to be able to be differentiated from the other colours by a digital image sensor (807), the resolution of which is lower than the resolution required for the unitary visual display of a sub-pixel (228), after the forming step.

8. A security device (1110) comprising a two-dimensional coloured bar code (110) manufactured according to the manufacturing method according to any one of claims 1 to 7.

9. A method for obtaining at least one information element encoded in a two-dimensional coloured bar code (110) manufactured according to the manufacturing method according to any one of claims 1 to 7, said obtaining method comprising the following steps: - reading (E902) said bar code (110) by means of a digital image sensor (807), and - extracting, by data processing means, said information element from the arrangement (112) of coloured base structural elements (114), the extraction being carried out according to the positioning of each structural element (114) in the arrangement (112), as well as according to the colour and / or pattern of each structural element (114) of the arrangement (112).

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

11. A method for authenticating a bearer of a security device according to claim 8, comprising a coloured bar code (110) comprising an arrangement (112) of coloured base structural elements (114) encoding 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) at least one candidate biometric characteristic, representative of the bearer by means of a biometric sensor, - comparing (E1210), by means of data processing, said at least one candidate biometric characteristic to said at least one reference biometric characteristic, a match 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.

12. The authentication method according to claim 11, wherein said at least one candidate biometric characteristic matches said at least one reference biometric feature if their distance according to a predefined comparison function is less than a predefined threshold.

13. The authentication method according to claim 11 or 12, wherein the arrangement (112) of structural elements (114) of the two-dimensional coloured bar code (110) furthermore encodes at least one information element relating to the physical uniqueness of the document, the method further comprising the following steps: - extracting said at least one information element relating to the physical uniqueness of the document, - detecting (E1212) at least one physical uniqueness element of the document, - comparing (E1214) said at least one information element relating to the physical uniqueness of the document and said at least one physical uniqueness element of the document, a match between said at least one information element relating to the physical uniqueness of the document and said at least one physical uniqueness element of the document being a condition for successful authentication of the bearer.

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