Method for manufacturing two-dimensional color barcodes and related security devices

Abstract

The present invention essentially relates to a method for producing a two-dimensional color barcode comprising an array of colored basic structural elements encoding at least one information element, said method comprising: a step (E304) of identifying by data processing means a group of colored basic structural elements corresponding to at least one information element, wherein at least one structural element of said group comprises a pattern; and a step (E308) of forming at least one structural element of said group on a support to generate an array, said support comprising a printed matrix comprising a plurality of pixels, said forming of said at least one colored basic structural element comprising a step of modifying said support in at least a portion of at least one sub-pixel of at least one pixel of said matrix, said modification making it possible to obtain the color and pattern of said at least one basic structural element. [Selected drawing] Figure 3

Description

[Technical field]

[0001] The present invention relates to the field of two-dimensional barcodes, and more particularly to producing two-dimensional color barcodes.

[0002] The present invention is non-exclusively applicable to identification type security devices such as passports, ID cards, driver's licenses, and the like. [Background technology]

[0003] As is known, authentication of the holder of a security document can be performed by comparing a reference biometric characteristic stored in the security document with an authenticating biometric characteristic of the holder acquired by a biometric data sensor.

[0004] The reference features, due to their size and security importance, are stored in the memory of an electronic chip in the security document.

[0005] However, the use of electronic chips within security documents makes the initial manufacture of security documents and their recycling particularly cumbersome and costly. Summary of the Invention [Problem to be solved by the invention]

[0006] The object of the present invention is to alleviate this problem and more generally relates to storing large amounts of data, such as biometric characteristics, in a secure and ecologically sound manner within a security device. [Means for solving the problem]

[0007] The present invention relates to a method for producing a two-dimensional color barcode comprising an array of colored basic structure elements encoding at least one information element, The method includes: - identifying by data processing means a group of coloured basic structure elements corresponding to said at least one information element, at least one structure element of the group comprising a pattern; - forming said at least one structural element of the group on a substrate to produce an array of colored basic structural elements; Including, - the substrate includes a print matrix including a plurality of pixels, each pixel including at least two differently colored sub-pixels; - the step of forming the at least one colored basic structural element comprises a step of modifying a substrate at the level of at least a 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 pattern of the at least one basic structural element.

[0008] The invention makes it possible to encode and thus store a large amount of information in a barcode on a limited surface, for example a portion of the surface of a security document.

[0009] In particular, the use of color in a barcode makes it possible to encode much more data than a black and white two-dimensional barcode of the same size, i.e., a barcode in which each basic structural element is all black or all white. Whereas the data density of such black and white two-dimensional barcodes, i.e., the amount of data (octets) stored per unit surface (millimeter squared), is typically less than one octet per millimeter squared, the present invention allows a much higher data density to be achieved, typically at least four octets per millimeter squared.

[0010] In addition, this technique for creating the array allows for secure storage of the information elements within the barcode, and in particular, unlike traditional printing techniques (e.g., inkjet, screen printing, or offset), the array cannot be altered without changing the barcode substrate, thereby making it possible to print other barcodes on top of the originally formed barcode.

[0011] Furthermore, the basic structure elements encode the information elements by their color and their pattern, allowing the barcode to be read by several types of sensors, for example standard color sensors or grayscale sensors.

[0012] In a particular embodiment, the information element is a reference biometric feature, and the method further comprises obtaining the at least one information element based on a digital representation of the information element.

[0013] The increased data density offered by barcodes makes it possible to store a sufficient number of reference biometric features to enable reliable authentication of the bearer of a security document containing the barcode, i.e. to compare the reference biometric features with the biometric features to be authenticated and verify the trade-off between False Rejection Rates (FRR) and False Acceptance Rates (FAR).

[0014] The present invention makes it possible, for example, to encode passport photographs of at least 10 kilooctets, so that face comparison algorithms can operate properly.

[0015] In certain embodiments, the substrate comprises a transparent layer, the matrix is ​​printed facing the transparent layer, and the modification is an opacification of the transparent layer facing said at least a portion of at least one subpixel of at least one pixel of the matrix, or alternatively an ablation of at least a portion of at least one subpixel, or a combination of an opacification and an ablation of the transparent layer.

[0016] Therefore, the formation of the structuring elements utilizes a precise technique whereby an array of colored basic structuring elements can be formed without any risk of smudging, which is different from conventional bar code printing techniques.

[0017] In addition, this technique for creating the array allows the secure storage of information elements in the barcode, in particular by making the array at two different layer levels or at different thickness levels of one same layer, which cannot be altered without changing the substrate of the barcode.

[0018] In a particular embodiment, the opacification is performed by a laser beam, which intermittently carbonizes the transparent layer to form, for example, a series of dots facing said at least a portion of at least one sub-pixel.

[0019] In a particular embodiment, the modification is the erasure of at least a portion of at least one subpixel of a pixel of the matrix by ablation performed by a laser beam, for example at least partially erasing the color of at least a portion of at least one subpixel.

[0020] Therefore, the step of forming the structuring elements utilizes a specific technique, which makes it possible to form an array of colored basic structuring elements without any risk of smudging, which is different from conventional barcode printing techniques.

[0021] In addition, this technique for creating sequences allows for secure storage of information elements within the barcode: in particular, the sequence cannot be altered without changing the substrate of the barcode.

[0022] In certain embodiments, said at least one information element being in the form of a digital data group comprising a plurality of digital data subgroups; The step of identifying a group of colored basic structure elements corresponding to said at least one information element is performed by means of a correspondence table that associates each different data subgroup with a different structure element of a unique color and / or comprising a unique pattern.

[0023] In a particular embodiment, the color of each different structural element of the correspondence table is selected such that after the forming step, it can be distinguished from other colors by a digital image sensor having a resolution lower than that required for the unit representation of a sub-pixel.

[0024] The present invention also relates to a security device including a two-dimensional color barcode produced by the above-mentioned production method.

[0025] The present invention further relates to a method for obtaining at least one information element encoded in a two-dimensional color barcode produced by the above-mentioned production method, said method comprising: - reading said barcode by a digital image sensor; - extracting, by data processing means, said information elements based on an arrangement of colored basic structure elements; Including, The extraction is performed according to the position of each structuring element within the array and according to the color and / or pattern of each structuring element of the array.

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

[0027] The present invention also relates to a method for authenticating a holder of a security device as described above, comprising a color barcode comprising an array of colored basic structure elements encoding at least one reference biometric feature, said method comprising: - acquiring said at least one reference biometric feature according to the acquisition method described above; - acquiring, by a biometric sensor, at least one target biometric feature representative of a bearer; - comparing, by data processing means, said at least one subject biometric feature with said at least one reference biometric feature, a correspondence between said at least one subject biometric feature and said at least one reference biometric feature being a condition for successful authentication of the bearer; Includes.

[0028] In a particular embodiment, the at least one target biometric feature corresponds to the at least one reference biometric feature if their distance according to a predefined comparison function is less than a predefined threshold.

[0029] In certain embodiments, the arrangement of structural elements of the two-dimensional barcode further encodes at least one piece of information regarding the physical uniqueness of the document; Here's how: - extracting said at least one information element relating to the physical uniqueness of the document; - detecting at least one physical unique element of the document; - comparing said at least one information element related to the physical uniqueness of the document with said at least one physical uniqueness element of the document, whereby a correspondence between said at least one information element related to the physical uniqueness of the document and said at least one physical uniqueness element of the document is a condition for successful authentication of the holder; Includes.

[0030] In certain embodiments, the different steps of the acquisition and / or authentication methods described above are specified by computer program instructions.

[0031] Consequently, the invention also relates to a computer program on an information medium (or recording medium), which is liable to be implemented by a server or, more generally, in a computer, which program comprises instructions suitable for carrying out the steps of the acquisition method and / or the authentication method described above.

[0032] This program may use any programming language and may be in the form of source code, object code or an intermediate code, particularly in compiled form, or in any other desired form.

[0033] In a particular embodiment, when a computer program comprises instructions suitable for carrying out the steps of the acquisition method, the instructions of the computer program may in particular control the digital image sensor so that it reads the barcode, thus enabling a digital barcode image or at least a part of the barcode to be acquired.

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

[0035] The information medium can be any type of device capable of storing a program. For example, the medium can include a rewritable non-volatile memory (such as an EEPROM or Flash NAND type), or a storage means such as a ROM, for example a CD-ROM or a microelectronic circuit ROM, or a magnetic recording means, for example a diskette (floppy disk) or a hard disk.

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

[0037] Alternatively, the information medium may be an integrated circuit in which the program is embedded, the circuit being suitable for performing or for use in the performance of the method.

[0038] Other characteristics and advantages of the present invention will become apparent from the following description, taken in conjunction with the attached drawings, which illustrate exemplary embodiments thereof without any limitation, in which: FIG. [Brief description of the drawings]

[0039] [Figure 1] 4 shows a schematic representation of an example of a barcode that can be produced by the method of FIG. [Figure 2A] 4A-4C are schematic top views of example substrates that can be used during the method of FIG. 3; [Figure 2B] 2B is a schematic representation of a portion of the substrate of FIG. 2A. [Diagram 3] The major steps of a manufacturing method according to an example embodiment of the present invention are depicted in flow chart form. [Figure 4] 4 shows a schematic representation of an example of a correspondence table that can be used during the execution of the method of FIG. 3; [Figure 5A] 5 illustrates a schematic diagram of the steps for selecting a color from the correspondence table of FIG. 4; [Figure 5B] 5 illustrates a schematic diagram of the steps for selecting a color from the correspondence table of FIG. 4; [Figure 5C] 5 illustrates a schematic diagram of the steps for selecting a color from the correspondence table of FIG. 4; [Figure 5D] 5 illustrates a schematic diagram of the steps for selecting a color from the correspondence table of FIG. 4; [Figure 6A] 2B illustrates a schematic representation of an example of an arrangement of structural elements on the substrate of FIG. 2A. [Figure 6B] 6B is a schematic representation of a cross-sectional view along line AA of the arrangement of structural elements of FIG. 6A. [Figure 7] 4A-4C are schematic representations of examples of modification sequences that can be used during the execution of the method of FIG. [Figure 8] 10 shows a schematic representation of an example of a barcode reader capable of carrying out the acquisition method of FIG. 9; [Figure 9] 1 illustrates, in flow chart form, the main steps of an acquisition method according to an exemplary embodiment of the present invention. [Figure 10A] 10 shows a schematic representation of an example of a comparison table that can be used during the execution of the method of FIG. 9; [Figure 10B]10 illustrates a schematic representation of another example of a comparison table that can be used during the execution of the method of FIG. 9; [Figure 11] 1 illustrates a schematic representation of an example security device according to an exemplary embodiment of the present invention; [Figure 12] 1 illustrates, in flow chart form, the main steps of an authentication method according to an exemplary embodiment of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0040] The present invention relates to the production of a two-dimensional color barcode 110, also known as a high density color barcode 110, which may typically take the form of a "Data Matrix" type code.

[0041] As shown in FIG. 1, which diagrammatically illustrates an example of a color barcode 110, the color barcode 110 includes an array 112 of colored basic structure elements 114 that encode at least one information element, typically in an encoding portion 118 of the array, which portion may be discontinuous.

[0042] Each information element may be a digital data item relating to the security device on which the barcode 110 is formed, digital data relating to the authorized holder of the security device (e.g., a reference biometric characteristic), or digital data relating to the organization that manufactured (or issued) the security device.

[0043] Each basic structuring element 114 corresponds to a basic entity in the array 112. All basic structuring elements typically have the same geometric shape, for example a triangle, a rectangle, a hexagon, or a square.

[0044] The array 112 of structural elements 114 may include one or more reference sequences 115 , each of which is located at a different location in the array 112 .

[0045] Each reference sequence 115 typically includes a different colored basic structure element 114 that may be present on the barcode 110. Each reference sequence 115 can therefore be used by the reader for calibration purposes, which will be explained later with respect to FIG.

[0046] Furthermore, the barcode 110 may include marks 116 for barcode detection and marks 117 for information area detection, which marks 116, 117 can also be used during reading of the barcode 110.

[0047] In addition, the barcode 110 may include an error correction portion 119, which may be discontinuous.

[0048] The barcode 110 is formed on a substrate 220, such as the substrate 220 shown in Figures 2A and 2B. The substrate 220 is typically a substrate including a transparent layer 222 and a matrix 224 printed facing the transparent layer 222, i.e. on one of the faces of the transparent layer 222 or on the other layer 220 positioned facing the transparent layer 222. The matrix 224 includes a plurality of pixels 226, each pixel 226 including at least two sub-pixels 228 of different colors. Each pixel 226 typically includes three sub-pixels 228 of different colors, for example the primary colors red, green, and blue or yellow, magenta, and cyan. As a variant, each pixel may include four sub-pixels 228 of different colors, for example yellow, magenta, cyan, and white.

[0049] 2A and 2B, each pixel 226 is a square and each sub-pixel 228 is a rectangle. In variants, the pixels 226 of the matrix 224 can have other geometric shapes, for example rectangular or triangular (so that the sub-pixels 228 can also have a triangular shape).

[0050] 2A and 2B, the matrix 224 includes 9 pixels, however, the matrix 224 can of course include 10 or more pixels.

[0051] For example, for a matrix 224 of 85.6 mm x 26.99 mm typically available for security documents, the pixel size is (4 x 70 μm) 2 Then the maximum number of pixels is 3.10 ∧ It's closer to 4 pixels.

[0052] The matrix 224 can be printed onto the transparent layer 222 or the opaque layer 229 of the substrate 220. The opaque layer 229 is typically white.

[0053] 2A and 2B, the matrix 224 is positioned between the transparent layer 222 and the opaque layer 229 of the substrate 220. As a variant, a transparent layer can be positioned between the matrix 224 and the opaque layer 229.

[0054] In a variant, the substrate 220 does not include any transparent layer 222 .

[0055] In a variation, the substrate 220 includes a blank layer over which a first transparent layer is positioned, a matrix is ​​positioned over the first transparent layer, and a second transparent layer is positioned over the matrix.

[0056] The substrate 220 may be incorporated into a security device, such as a pass or security document. The security document may be an identity card such as a passport, an ID card, a driver's license, or the like.

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

[0058] Figure 3 illustrates a method for manufacturing a color barcode 110, such as the barcode 110 of Figure 1, which method conforms to an exemplary embodiment of the present invention. The manufacturing method is typically performed by a manufacturing system including digital data processing means and a laser beam, typically having a wavelength of 1064 nm.

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

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

[0061] For simplicity of the remainder of the description, it will be considered from now on that one information element is obtained in step E302. However, for the implementation of the present invention, it will be understood that multiple information elements may be obtained in this step E302 and encoded in the color barcode 110 during the execution of the subsequent steps.

[0062] An information element typically takes the form of a digital data group that contains multiple digital data subgroups.

[0063] An information element is typically obtained based on a digital representation of this information element, for example based on a digital image. Image processing, depending on the nature of the information element, may be performed on the digital image to extract the information element.

[0064] The information element is for example a reference biometric feature, typically derived from a digital image, which can be used for authentication of the holder of the security document.

[0065] The digital image is typically an image or signature of the face, iris or fingerprint of the holder of the security document. The reference biometric feature may therefore be a set of facial, iris or fingerprint feature points (which in the case of fingerprints may be called minutiae), selected to ensure that they represent the legitimate holder of the security document.

[0066] In variants, the information element is digital data relating to the security document on which the barcode 110 is formed, a digital data item relating to the user (or holder) of the security device, or digital data relating to the organization which manufactured (or issued) the security device.

[0067] In step E304, a group of colored basic structure elements corresponding to the information element obtained in step E302 is identified by the data processing means of the manufacturing system. This step therefore makes it possible to convert the information element into a group of colored basic structure elements to be formed on the substrate, thus creating the barcode 110.

[0068] Identification of the group of structuring elements is typically accomplished by a first correspondence table that associates each different data subgroup with a different structuring element of a unique color, which may include a unique pattern.

[0069] Therefore, each data subgroup of information elements can be searched in the first correspondence table to obtain the associated structure element 114 and identify the group of structure elements.

[0070] Each of the searched data subgroups can be obtained after performing a cardinality change at the data group level.

[0071] FIG. 4 shows a schematic example of a first correspondence table 400 that can be used in step E304.

[0072] This first correspondence table associates 16 types of structure elements 114 with 16 types of data subgroups 402, each of the different data subgroups 402 corresponding to a different hexadecimal base symbol. Therefore, if the information element is not coded in hexadecimal, a base change is required to obtain the information element coded in hexadecimal. The information element may thus include a group of hexadecimal base symbols, each symbol being a data subgroup 402 searchable in the first correspondence table 400.

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

[0074] Each color of the structuring elements 114 of the correspondence table available in step E304 is selected so that, during reading of the color barcode 110 after step E308 of forming the structuring elements 114, it can be distinguished from the other colors by a video camera, described below, of a lower resolution than is necessary for the sub-pixel unit display (for example a low-resolution color video camera). This makes it possible to minimize the risk of errors during reading of the barcode 110.

[0075] The selection of the colors of the structure elements 114 of the first correspondence table is performed during a preliminary phase before the use of the first correspondence table, therefore before step E304. Each color can be defined by varying the gray levels of several different primary colors (for example red, green and blue) forming the pixel matrix. Each primary color has a different position in the visible spectrum.

[0076] As shown in Fig. 5A, 27 different colors 501 can be generated with three gray scales (0; 50; 100) for each primary color R, V, B. However, certain colors may be too close to each other and thus cause errors during reading of the barcode. However, by selecting, for example, 16 colors from the 27 different colors, a barcode can be obtained that is 4 times more compact than a black and white 2D barcode. The more colors selected, the higher the data density.

[0077] Colors are selected from a color family (eg, color family 501 in FIG. 5A) by a reference scanner, with only those colors in the family that are readily distinguishable after scanning by the reference scanner.

[0078] More specifically, during a preliminary phase of colour selection, for each colour in the family a different colour region can be defined by the data processing means.

[0079] As shown in FIG. 5B, the colored regions 502 are, for example, rows, and each row 502 is formed by several basic structuring elements 114 of the same color.

[0080] The colored regions 502 are formed on a flat surface, such as a sheet. The colored regions 502 can be printed, for example, by an inkjet or laser printer. As a variant, as shown in Fig. 5C, the colored regions 502 can be formed by modifying a flat substrate, for example having the same structure as the substrate of Figs. 2A and 2B, using a modification sequence 504 based on the defined color regions 502. The modification of the substrate can be performed using the method described below with respect to step E308.

[0081] The flat surface is then scanned by a reference scanner, which obtains a digital image 506 of the flat surface. The color of each pixel of the digital image 506 can typically be measured at the level of the primary colors. Figure 5D represents the colors of the four pixels i, j, k, and m of the digital image 506 in the colorimetric space. The color cj of pixel j is not selected because it is too close to the color ck of pixel k (located within a certain interval l of neighboring colors in the primary color space RGB in the figure), and therefore is not included in the set EC of possible final colors. The selection of colors can be made in a complementary manner using other differentiation parameters, such as the geometry of the colored basic structure elements 114 or the position of the colored basic structure elements 114 in the barcode.

[0082] The number of possible combinations of the first correspondence table and the encoding by the matrix 224 is M N where M is the number of different structuring elements of the table and N is the number of available positions on the matrix 224, i.e. the number of pixels of the matrix 224 that can be used to code an information element, e.g. the number of hixels that can be used to form the structuring elements of the encoding part 118 of the array.

[0083] For example, all pixels of the matrix 224 of Figures 2A and 2B may be considered to be used to form information elements. When using the first correspondence table of Figure 4, the number of possible coding combinations on this matrix 224 is 16. 4 There is a street.

[0084] Additional structuring elements, used to minimize the risk of misreading, can be added to the set of colored basic structuring elements identified in step E304. These additional structuring elements can be obtained, for example, using the Reed-Solomon error correction algorithm. Furthermore, a structuring element of a reference sequence can be added to the set.

[0085] The manufacturing method may further comprise a step E306 of obtaining a substrate 220 on which the barcode 110 can be formed, for example the substrate 220 shown in Figures 2A and 2B. The substrate 220 may for example be manufactured, the manufacturing step of the substrate 220 comprising printing the matrix 224 on the transparent layer 222 or on the opaque layer 229 and, if applicable, laminating the substrate layer 220.

[0086] Next, in step E308, at least one structural element 114 of the group of colored basic structural elements is formed on the substrate 220 to create an array 112 of colored basic structural elements 114.

[0087] In this step E308, an array 112 of construction elements 114 can be created by forming the group of construction elements 114 identified in step E304, for example along a predetermined trajectory.

[0088] The step of forming the group of structural elements 114 comprises a sub-step of modifying the substrate 220 at the level of at least some of the sub-pixels 228 of at least one pixel 226 of the matrix 224, which modification makes it possible to obtain the color of the structural elements 114 and, if applicable, the pattern 404 of the structural elements 114. The modification is typically performed by a laser of the manufacturing system.

[0089] In this way, a pixel 226 of the matrix 224 becomes a structural element 114 of the array 112 after modifying the substrate 220 at the level of at least a portion of at least one of its sub-pixels 228 .

[0090] The modification is, for example, an opacification, performed by a laser beam, of the transparent layer 222 facing at least a portion of at least one subpixel 228. For example, for each structural element 114 of the group, the laser beam intermittently carbonizes the transparent layer 222 to form a series of points, for example two or four points, facing said at least a portion of the transparent layer 222 (i.e. between the two outer faces of the transparent layer 222).

[0091] Carbonization of the transparent layer 222 for at least a portion of a subpixel 228 of the pixel 224 produces a grey level at the level of this subpixel 228 , thereby making it possible to obtain the colour of the structural element 114 on the basis of the pixel 226 .

[0092] In addition, carbonization of the transparent layer 222 facing at least a portion of the sub-pixels 228 of the pixel 226 makes it possible to obtain a pattern 404 of structural elements 114 produced from the pixel 226. For example, a series of dots can be formed to reproduce the pattern 404 of structural elements 114 as shown by the first table 400.

[0093] If the subpixel colors are produced using printing techniques, the modification of substrate 220 is typically an opacification.

[0094] 6A and 6B depict the substrate 220 of FIGS. 2A and 2B upon which the array 112 of colored basic structural elements 114 has been created during the performance of step E308.

[0095] The array 112 of Figures 6A and 6B includes nine structural elements 114 arranged along the trajectory Ta.

[0096] The nine structure elements 114 are obtained in step E304 by the first table 400 of FIG. 4, whereby they encode the information element taking the form 1f59ce6b6.

[0097] 6A and 6B, each subpixel 228 may be, for example, a rectangle that can be divided into three equal portions (typically three squares), and the laser carbonizes the transparent layer 222 to form one or more dots (e.g., two or four dots) facing each portion. Of course, other configurations are also contemplated.

[0098] The modification can be, as a variant, an erasure by ablation performed by a laser beam of said at least a portion of at least one sub-pixel 228. For example, for each structural element 114 of the group, the laser beam at least partially erases the color of at least a portion of at least one sub-pixel.

[0099] When the subpixel colors are formed by an optical diffraction device, for example using a hologram, the modification is typically erasure by ablation.

[0100] All structural elements 114 of the group are formed, for example, on the substrate 220 in step E308.

[0101] As a variant, the step of forming one or more structural elements 114 of the group does not require any modification of the substrate 220. Each of these structural elements then does not have any pattern 404, and the color of the element is defined by the sub-pixels of the associated pixel.

[0102] A sequence of modifications can be used to guide the laser during modification of the substrate 220, for example during erasure by carbonization or ablation of the matrix, the sequence including all modifications that must be made on the substrate 220. The sequence may include all patterns of all structural elements 114 that must be formed, which are arranged along a predetermined trajectory of the array. Figure 7 shows an example of a modification sequence 700 that may be used to manufacture the barcode of Figure 1.

[0103] The color barcode 110 produced by the method of FIG. 3 can then be read to obtain the encoded information.

[0104] FIG. 8 illustrates a schematic representation of a color barcode reader 800 capable of performing an acquisition method according to an exemplary embodiment, such as the method described with respect to FIG.

[0105] The reader 800 shows a conventional architecture of a computer and may include, inter alia, a processor 802, a read-only memory 803 (ROM type), a rewriteable non-volatile memory 804 (for example EEPROM or Flash NAND type), a rewriteable volatile memory 805 (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 storage) medium according to a particular embodiment of the invention. A computer program P1 is stored in the read-only memory 804, by means of which the reader 800 can carry out at least a part of the acquisition method according to an exemplary embodiment of the invention. As a variant, the computer program P1 is stored in a rewritable non-volatile memory 805. The reader 800 therefore comprises data processing means.

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

[0108] The reader 800 may be capable of communicating with external electronic devices, such as a server, via a communication interface 806 and a telecommunications network.

[0109] The reader 800 is capable of reading the color barcode 110 according to an exemplary embodiment by means of a sensor 807 .

[0110] FIG. 9 illustrates a method for obtaining at least one information element encoded in a color barcode 110 produced by the method of FIG. 3, such as the barcode 110 of FIG. 1 or FIG. 6A.

[0111] At step E 902 , the barcode 110 is read by the digital image sensor 807 .

[0112] If the barcode 110 includes at least one reference sequence 115, the reading step E902 may include color calibration of the sensor 707. In particular, the reference sequence 115 typically includes each different colored basic structural element 114 that may be present on the color barcode 110, which sequence can be used as a model to dynamically calibrate the sensor 807 and distinguish colors during reading of the color barcode 110.

[0113] This calibration makes it possible to offset color transfer variations that may occur between two sensors of different types or two sensors of the same type but calibrated differently, or the same sensor but under different lighting conditions (e.g., lighting conditions other than white that distort colors).

[0114] This calibration also makes it possible to offset color variations between two different barcodes due to the manufacturing of the barcodes, which are typically due to color variations of the subpixels of the matrix, deformations of the matrix, variations in the power of the laser or in the position of the modifications made by the laser.

[0115] At step E906, the reader 800, or more precisely the data processing means of the reader 800, extracts information elements from the array 112 of coloured basic structure elements 114.

[0116] The extraction is performed depending on the position of each structural element 114 in the array 112, or more precisely, depending on the trajectory of the array, and depending on the color and / or pattern 404 of each structural element 114 encoding an information element of the array 112, e.g., each structural element 114 of the encoding unit 118.

[0117] The colours and patterns 404 of each structural element 114 of the coding portion 118 can therefore be used in combination if the resolution of the sensor 807 allows it. If the resolution of the sensor 807 is lower, then only colours can be used.

[0118] Specifically, reading a color barcode does not require a very high performance camera. However, if the color camera fails, a reading of pattern 404 can always be obtained by the higher performance grayscale camera N. Pattern 404 can be isolated and thus form a "back-up" code in case of failure to read the color barcode.

[0119] More precisely, the second correspondence table can be used to look up each structure element 114 of the array 112 and identify the corresponding data subgroups. The data subgroups are positioned according to the position of each structure element 114 of the array 112 and thus relative to each other along the trajectory of the array.

[0120] Additionally, the structuring element 114 of the error correction unit 119 can also be used to search in the second correspondence table and subsequently identify the data subgroup.

[0121] Each structuring element 114 of the array 112 can be looked up in the second correspondence table using the color of the structuring element 114 and / or the pattern of the structuring element 114, where the color and the pattern of the structuring element 114 encode the same information.

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

[0123] In particular, if the sensor 807 is a sensor capable of distinguishing colors, such as a low-resolution color camera, the color of the structuring element obtained during the reading step E902 is looked up in a second correspondence table.

[0124] If the sensor 807 is a sensor capable of distinguishing between grey levels, such as a grey-scale camera, the pattern of the structuring elements acquired during the reading step E902 is searched for in a second correspondence table.

[0125] Therefore, the steps of manufacturing the barcode 110 according to the method of FIG. 3 can make the barcode 110 readable by several different types of sensors 807.

[0126] The result of step E906, i.e. the error correction code and the information elements extracted by array 112, can be used to define the next reference sequence to be formed, typically if the extraction is performed as part of machine learning, and therefore to refine the detection model.

[0127] As mentioned above, the substrate 220 on which the color barcode 110 is produced by the method of Fig. 3 can be integrated with a security device such as a security document 1110 (see Fig. 11). The information element encoded by the color barcode can be a reference biometric feature characterizing the bearer of the security document, and this reference biometric sensor can be used to authenticate the legitimate bearer of the security document.

[0128] The reader 800 of Fig. 8 may therefore be a security document reader capable of performing an authentication method according to an exemplary embodiment, such as the method described with respect to Fig. 12. The reader 800 further comprises a biometric sensor 1118 and the computer program P1 enables the reader 800 to perform all or part of the authentication method.

[0129] Biometric sensor 1118 is, for example, typically an optical sensor capable of capturing a digital image of a fingerprint, or a digital camera or digital video camera capable of capturing digital images of a face and / or iris.

[0130] FIG. 12 illustrates a method for authenticating the bearer of a security document that includes a color barcode 110 produced by the method of FIG. 3, for example the color barcode 110 of FIG. 1 or FIG. 6A.

[0131] The color barcode 110 encodes a reference biometric feature that characterizes the bearer of the security document.

[0132] Steps E902 and E906 of the acquisition method described in FIG. 9 are performed by the data processing means of the reader 800 to extract the reference biometric features of the barcode 110.

[0133] At step E1208, at least one subject biometric characteristic representative of the bearer is acquired by the biometric sensor 118.

[0134] For simplicity of the remainder of the description, in the remainder of the text it is considered that one subject biometric feature is obtained in step E1208. However, for purposes of carrying out the present invention, it should be understood that multiple subject biometric features may be obtained in step E1208 and then compared with multiple reference biometric features in step E1210 described below.

[0135] At step E1210, the data processing means of the reader 800 compare the biometric characteristics of the authentication candidate with the reference biometric characteristics, a correspondence between the biometric characteristics of the authentication candidate and the reference biometric characteristics being a condition for successful authentication of the holder.

[0136] A biometric feature to be authenticated typically corresponds to a reference biometric feature if their distance according to a predefined comparison function is less than a predefined threshold.

[0137] If the biometric feature of the subject corresponds to the reference biometric feature, then authentication of the bearer is typically successful. If the biometric feature of the subject does not correspond to the reference biometric feature, then authentication of the bearer is unsuccessful.

[0138] The arrangement of structural elements 114 of the colour barcode can furthermore encode at least one information element relating to the physical uniqueness of the security document.

[0139] This information element can be called the signature of the security document 1110 and is for example the coordinates of a cloud of points relative to a given reference mark, these coordinates representing a PUF (Physical Unclonable Function).

[0140] A physically unclonable function is the result of an easily implemented phenomenon, the result of which cannot be replicated even under the same operating conditions.

[0141] For example, the coordinates represent a thermal deformation of the security document 1110. The manufacturing method of the security document 1110 may include a heat input assembly of a first layer and at least a second layer, where applicable, accompanied by the application of pressure to said layers. The first layer (e.g. the transparent layer 222) may typically be made of a thermoplastic polymer material and includes a reference pattern, e.g. the matrix itself, which includes the identified points. The reference pattern is typically printed in a sensitive area of ​​the security document, i.e. an area that can be modified, e.g. an area that includes information identifying the authorized holder of the security document 1110, e.g. a photo of the authorized holder, a hinge of the security document, etc.

[0142] The assembly of the layers leads to a deformation of the first layer and thus of the pattern of the first layer, which deformation cannot 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 therefore form an unreplicable signature. The differences in amplitude and orientation can then be detected by light and subsequently stored in the form of coordinates in the array 112 of structural elements 114.

[0143] Therefore, steps E902 and E906 of the acquisition method described with reference to FIG. 9 can also be executed by the data processing means of the reader 800 to extract from the barcode 110 information elements relating to the physical uniqueness of the security document.

[0144] In step E1212, at least one physical unique element of the document can be detected by a suitable sensor of the reader 800, or by a higher resolution reader 800 used by the forensic department during criminal investigations. The detected elements are typically the coordinates of a point of the identified point cloud of the pattern.

[0145] Next, in step E1214, the information elements relating to the physical uniqueness of the document are compared with the physical uniqueness elements of the document, and a correspondence between the information elements relating to the physical uniqueness of the document and the physical uniqueness of the document is a condition for successful authentication of the holder.

[0146] If the pattern is altered after the production of the security document 1110, the information elements regarding the physical uniqueness of the document will not correspond to the physical uniqueness of the security document 1110 and authentication of the bearer will fail.

[0147] If the pattern has not been altered after production of the security document, the information elements on the physical uniqueness of the security document 1110 correspond to the physical uniqueness of the security document 1110. Authentication of the bearer is then successful. As a variant, authentication of the bearer is successful if there is a correspondence between the information elements on the physical uniqueness and the physical uniqueness elements of the security document 1110 and if there is a correspondence between the biometric features to be authenticated and the reference biometric features in step E1210.

Claims

1. A method for producing a two-dimensional color barcode (110) comprising an array (112) of colored basic structure elements (114) encoding at least one information element, comprising the steps of: - identifying (E304) by data processing means a group of coloured basic structure elements corresponding to said at least one information element, at least one structure element of said group comprising a pattern; - forming (E308) said at least one structural element of said group on a substrate (220) to produce said array (112) of colored basic structural elements (114); Including, - said substrate (220) comprises a print matrix (224) comprising a plurality of pixels (226), each pixel (226) comprising at least two differently colored sub-pixels (228); A manufacturing method in which the step of forming the at least one colored basic structural element (114) comprises a step of modifying the substrate (220) at the level of at least a portion 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 pattern of the at least one basic structural element (114).

2. The method of claim 1 , wherein the information element is a reference biometric feature, and further comprising a step (E302) of obtaining the at least one information element based on a digital representation of the information element.

3. the substrate (220) includes a transparent layer (222), the matrix (224) is printed facing the transparent layer (222); 3. The method according to claim 1 or 2, wherein the modification is an opacification of the transparent layer (222) facing the at least part of at least one sub-pixel (228) of at least one pixel (226) of the matrix (224).

4. The method of claim 3, wherein the opacifying is performed by a laser beam, the laser beam intermittently carbonizing the transparent layer (222) to form a series of dots facing the at least a portion of at least one subpixel (228).

5. 3. The method according to claim 1 or 2, wherein the modification is erasure by ablation of at least a portion of at least one sub-pixel (228) of a pixel (226) of the matrix (224) performed by a laser beam, for example at least partially erasing the color of at least a portion of the at least one sub-pixel (228).

6. the at least one information element is in the form of a digital data group comprising a plurality of digital data subgroups (402); said step of identifying a group (112) of colored basic structure elements (114) corresponding to said at least one information element is performed by means of a correspondence table (400) that associates each of the different data subgroups (402) with a different structure element (114) of a unique color and / or with a unique pattern (404); The method according to any one of claims 1 to 5.

7. 7. The method of claim 6, wherein the colors of each different structural element (114) of the correspondence table (400) are selected such that after the forming step, the color can be distinguished from other colors by a digital image sensor (807) having a resolution lower than that required for unit representation of a subpixel (228).

8. A security device (1110) comprising a two-dimensional color barcode (110) produced by the method of claim 1-7.

9. A method for obtaining at least one information element encoded in a two-dimensional color barcode (110) produced by the method according to any one of claims 1 to 7, comprising the steps of: - a step (E902) of reading said barcode (110) by a digital image sensor (807); - extracting, by data processing means, said information elements on the basis of said sequence (112) of coloured basic structure elements (114), said extraction being effected as a function of the position of each structure element (114) in said sequence (112) and as a function of said colour and / or said pattern of each structure element (114) of said sequence (112); Including, how to obtain.

10. 10. The acquisition method of claim 9, wherein the array (112) of structural elements (114) includes a reference sequence including a plurality of basic structural elements of different colors, and the reading step (E902) includes color calibration of the digital image sensor (807) based on the reference sequence.

11. 10. A method for authenticating a holder of a security device according to claim 8, comprising a color barcode (110) including an array (112) of colored basic structure elements (114) encoding at least one reference biometric feature, the method comprising: - acquiring said at least one reference biometric feature according to an acquisition method according to claim 9 or 10, - acquiring (E1208) by means of a biometric sensor at least one target biometric feature representative of said bearer; a step (E1210) of comparing, by data processing means, said at least one target biometric feature with said at least one reference biometric feature, a correspondence between said at least one target biometric feature and said at least one reference biometric feature being a condition for successful authentication of said bearer; , an authentication method, including

12. 12. The method of authentication according to claim 11, wherein the at least one target biometric feature corresponds to the at least one reference biometric feature if their distance according to a predetermined comparison function is less than a predetermined threshold.

13. said arrangement (112) of structural elements (114) of said two-dimensional barcode (110) further encodes at least one piece of information relating to the physical uniqueness of said security device (1110); - extracting said at least one information element relating to said physical uniqueness of said security device (1110); - detecting (E1212) at least one physical uniqueness element of said security device (1110); a step (E1214) of comparing said at least one information element related to said physical uniqueness of said security device (1110) with said at least one physical uniqueness element of said security device (1110), wherein a correspondence between said at least one information element related to said physical uniqueness of said security device (1110) and said at least one physical uniqueness element of said security device (1110) is a condition for successful authentication of said holder; Including, 13. The authentication method according to claim 11 or 12.

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