Marking comprising two patterns on a surface

Abstract

Marking comprising on a surface: a first pattern for coding a first numerical information item on said surface, the first pattern comprising a specific arrangement of a plurality of symbols belonging to a set of symbols, each symbol in the arrangement being intended for the coding of a portion of said numerical information item, each symbol including at least one differential pair of elements positioned in a specific way, each element having a parameter, the parameter of the first element of each differential pair having a first value and the parameter of the second element of each differential pair having a second value different from the first value, a second pattern for coding a second numerical information item on said surface, wherein the first and second pattern are adapted to be read under corresponding distinct first and second reading conditions.

Claims

1. Marking comprising on a surface: a first pattern for coding a first numerical information item on said surface, the first pattern comprising a specific arrangement of a plurality of symbols belonging to a set of symbols, each symbol in the arrangement being intended for the coding of a portion of said numerical information item, each symbol including at least one differential pair of elements positioned in a specific way, each element having a parameter, the parameter of a first element of each differential pair having a first value and the parameter of a second element of each differential pair having a second value different from the first value and a difference between said first value and said second value cannot be detected by the naked eye, a second pattern for coding a second numerical information item on said surface, said second pattern being a one-dimensional barcode or a two-dimensional barcode, wherein the first pattern, including each element thereof, and second pattern are adapted to be read under corresponding distinct first and second reading conditions, and the first pattern is embedded either in at least one black portion of the barcode or in at least one white portion of the barcode.

2. The marking as claimed in claim 1, wherein the first pattern is associated with a first resolution so that it can be read under the first reading condition and the second pattern is associated with a second resolution so that it can be read under the second reading conditions, the first resolution being distinct from the second resolution.

3. The marking as claimed in claim 2, wherein the first resolution is at least five times finer than the second resolution or at least five times coarser than the second resolution.

4. The marking as claimed in claim 1, wherein the first pattern is marked using a first ink so that it can be read under the first reading condition and the second pattern is marked using a second ink so that it can be read under the second condition, the first ink being distinct from the second ink.

5. The marking as claimed in claim 4, wherein the first ink is chosen in the group formed by black or colored ink and the second ink is chosen in the group formed by black or colored IR transparent ink.

6. The marking as claimed in claim 1, wherein the first pattern and second pattern overlap fully or partially.

7. A system for applying a marking according to claim 1 on a surface, comprising: a processor configured for defining a first and a second pattern, an applicator for applying on a surface said first pattern and said second pattern adapted to be read under corresponding distinct first and second reading conditions.

8. Method for reading a marking according to claim 1 on a surface, comprising: reading said marking using a first reading process adapted for first reading conditions for reading the first pattern, reading said marking using a second reading process adapted for second reading conditions for reading the second pattern.

9. System for reading a marking according to claim 1 on a surface, comprising: a first reader adapted for first reading conditions, a second reader adapted for second reading conditions.

10. A method for applying a marking on a surface, comprising the following steps: defining first reading conditions, defining a first pattern to be applied for coding a first numerical information item, the first pattern comprising a specific arrangement of a plurality of symbols belonging to a set of symbols, each symbol in the arrangement being intended for the coding of a portion of said numerical information item, each symbol including at least one differential pair of elements positioned in a specific way, each element having a parameter, the parameter of the a first element of each differential pair having a first value and the parameter of the a second element of each differential pair having a second value different from the first value and a difference between said first value and said second value cannot be detected by the naked eye, defining second reading conditions distinct from the first reading conditions, defining a second pattern to be applied for coding a second numerical information item, said second pattern being a one-dimensional barcode or a two-dimensional barcode, providing a surface, applying said first pattern on said surface using a first application process so that the first pattern, including each element thereof, can be read under the first reading conditions, applying said second pattern on said surface using a second application process so that the second pattern can be read under the second reading conditions, wherein the first pattern is embedded either in at least one black portion of the barcode or in at least one white portion of the barcode.

11. The method according to claim 10, wherein the first application process applies the first pattern with a first resolution and the second application process applies the second pattern with a second resolution, the first resolution being distinct from the second resolution.

12. The method according to claim 11, wherein the first resolution is at least five times finer than the second resolution or at least five times coarser than the second resolution.

13. The method as claimed in claim 10, wherein the first application process uses a first ink and the second application process uses a second ink, the first ink being distinct from the second ink.

14. The method as claimed in claim 13, wherein the first ink is chosen in the group consisting of black or colored ink and the second ink is chosen in the group formed by consisting of black or colored IR transparent ink.

15. A process for marking objects by inkjet printing, wherein projected ink forms the patterns according to claim 10.

Description

(1) Other advantages and features of the invention will become apparent from studying the detailed description of a few exemplary implementations and embodiments, which are in no way limiting, and the appended drawings, in which:

(2) FIG. 1 schematically illustrates an implementation of a creation of a pattern according to the invention,

(3) FIG. 2 schematically illustrates another implementation of a creation of a pattern according to the invention,

(4) FIG. 3 schematically illustrates an implementation of a method for marking the pattern of FIG. 1 on an article or security device,

(5) FIG. 4 schematically illustrates an implementation of a method for reading an identification pattern applied to an article,

(6) FIG. 5 schematically illustrates an embodiment of a pattern according to the invention,

(7) FIG. 6 illustrates another implementation and embodiment according to the invention,

(8) FIG. 7 illustrates a marking according to an embodiment of the invention, and

(9) FIG. 8 illustrates a marking according to another embodiment of the invention.

(10) In the figures, the same references correspond to the same elements. The elements of the figures are not drawn to scale.

(11) FIG. 1 schematically shows an implementation of a creation S1 of an arrangement P1 of symbols according to an embodiment of the invention so that a first or second pattern may be formed.

(12) The symbols of the arrangement P1, denoted A, B, C and D, belong to a set of symbols ENS1.

(13) The symbols A, B, C and D, four of them in this example (but there could obviously be more), comprise a differential pair of elements referenced E1 and E2 in the figure. The elements E1 and E2 are represented in the figure, by way of example and in order to give a better understanding of the invention through cross-ruled or shaded spots illustrating different values of a parameter, the parameter being, for example, the grey level. The cross-ruled spots E1 have, in the example illustrated, a parameter value greater than that of the shaded spots E2. In other words, the spots forming the elements E1 are darker than those forming the elements E2. The elements E1 and E2 thus form a differential pair according to the invention.

(14) The respective position of the elements of a differential pair E1 and E2 defines the symbol (A to D).

(15) In the example illustrated, the elements E1 and E2 of a differential pair are separated from one another by the approximate size of an element. Other positionings are possible. The two elements of a differential pair of a symbol may be close, and even in contact, or, on the other hand, further apart. The shape of the elements, in this case circular spot form, may also be different, for example rectangular, triangular or elliptical, in variants of the invention.

(16) Furthermore, in the set of symbols ENS1, the symbols are all different and each of these symbols comprises two possible representations. The relative position of the elements of the differential pair is here unchanged for the two representations of a differential pair. Between two representations, the parameter values of the elements may change, or else the elements may be reversed, but their positioning in the differential pair and in the symbol will remain the same.

(17) Thus, the symbol A comprises a differential pair of elements E1 and E2 positioned in a vertical arrangement in the two representations A1 and A2. In the first representation A1 of the symbol A, the element E1 which is a cross-ruled spot, is positioned above the element E2, which is a shaded spot. In the second representation A2, it is the element E2 which is above the element E1. Thus, the symbol A comprises a differential pair of elements positioned vertically and two representations in which the elements E1 and E2 have been reversed.

(18) The symbol B also comprises a differential pair of elements E1 and E2, but positioned horizontally. In a first representation B1, the element E1 is to the left of the element E2, in a second representation B2, the element E1 is to the right of the element E2.

(19) The symbol C comprises a differential pair of elements E1 and E2 positioned in a first diagonal direction. In a first representation C1, the element E1 is positioned above and to the left of the element E2, and in a second representation C2, the element E1 is positioned below and to the right of the element E2.

(20) Finally, the symbol D comprises a differential pair of elements E1 and E2 positioned in a second diagonal direction opposite to said first diagonal direction of the symbol C. In a first representation D1, the element E1 is positioned above and to the right of the element E2, and in a second representation D2, the element E1 is positioned below and to the left of the element E2.

(21) The four symbols A, B, C and D thus defined each with two representations define the set ENS1 with which the reference pattern P1 is created (S1).

(22) It will be noted that the two representations of each symbol of the set ENS1 may define a bit of a binary value. As an example, the representations A1, B1, C1 and D1 correspond to the value 1, and the representations A2, B2, C2 and D2 correspond to the value 0.

(23) The arrangement of symbols forming the reference pattern P1 may be created by arranging symbols of the set ENS1, without defining the representation of these symbols. In the example illustrated, the symbols are arranged in a rectangular area in which the space is used so as to include a maximum number of symbols in this area. The symbols are, for examples, nested one inside the other and the elements of these symbols are aligned vertically and horizontally within the arrangement P1. It will be understood that, in the arrangement of symbols forming the reference pattern P1, the symbols could be arranged in an area with a different geometrical shape, for example square, circular, elliptical, triangular or other.

(24) In the example illustrated, a symbol A is positioned at the top right of the arrangement P1, an element of this symbol is positioned at the intersection of a horizontal axis X-X and of a vertical axis Z-Z, and an element is positioned at the intersection of a horizontal axis Y Y, offset by approximately the dimension of an element E1 or E2 relative to the horizontal axis X-X and the vertical axis Z-Z. A symbol B may be positioned under this symbol A by aligning a right-hand element of this symbol B with the axis Z-Z. It is also possible to position a symbol B to the right of the symbol A whose two elements are then aligned with the axis X-X.

(25) The reference pattern P1 comprises, in the example illustrated, 32 symbols of the set of symbols ENS1. Since each of these symbols has two representations, it is possible to create, in this example, 232=4 294 967 296 different reference patterns P1. Furthermore, by associating a bit with each symbol, 232 binary values can be coded by means of this arrangement of symbols P1.

(26) It will be noted that, by increasing the number of symbols of the reference pattern P1, the number of possible representations of the same pattern and the number of numerical values which can be coded by means of this pattern are increased. Generally, for a set of symbols each comprising a differential pair and having two representations, it will be possible to obtain, for a “pattern” having n symbols, 2n different representations and values.

(27) In order to use the “pattern” to coder a numerical value, it is necessary to assign a reading order to the symbols which make up the “pattern”.

(28) Thus, for a binary value comprising 32 bits, the so-called most significant bit (MSB) may be assigned to the symbol MSB1 of the pattern P1, here a symbol A positioned top left of the “pattern” P1. The so-called least significant bit (LSB) may be assigned to the symbol LSB1, here a symbol A arranged bottom right of the “pattern” P1. The order in which the other bits are assigned may be, for example, from left to right and from top to bottom of the “pattern” P1. According to one aspect, it is also possible to assign a random order of the bits in which the successive bits are not adjacent.

(29) An operation denoted S2 in the figure is used to create a pattern for coding numerical information comprising symbols belonging to the set ENS1 and arranged according to the reference pattern P1. Two possible examples of patterns M1 and M2 obtained by the operation S2 are represented. The patterns M1 and M2 correspond to two different numerical values. Obviously, the number of patterns Mn that it is possible to obtain by the operation S2 is not limited.

(30) In the example illustrated, the most significant bit MSB1 of the value coded in the pattern M1 is equal to that of the value coded in the pattern M2 and here corresponds to a representation A1: 1. The second bit of these values, corresponding to the symbol SB2, a symbol B, is represented in the representation B1 within the pattern M1, and in the representation B2 within the pattern M2. Thus, the second bit of the value coded in the pattern M1 corresponds to a 1 and in the pattern M2 to a 0. Other symbols are represented in different representations for the two patterns M1 and M2, for example the symbols SB3 and SB4. The same may also apply for all the symbols of the different coding patterns obtained by the operation S2.

(31) It should be noted that M1 and M2 may be used as first and second pattern, with corresponding reading conditions.

(32) FIG. 2 schematically shows another implementation of a creation S′1 of an arrangement of symbols or reference pattern P′1. In this example, the set of symbols ENS′1 comprises only a single symbol, but it could also comprise a number of different symbols.

(33) The set of symbols ENS′1 here comprises a single symbol A′ comprising two differential pairs of elements. The symbol A′ comprises two differential pairs whose elements are aligned horizontally and the differential pairs are positioned vertically.

(34) The use of two differential pairs makes it possible notably to define four representations. A representation A′1 is obtained in which a differential pair PA′1 is positioned above a differential pair PA′2. In the representation A′1, the differential pair PA′1 and the differential pair PA′2 both comprise an element E1 to the right, an element E2 to the left. By modifying the respective positions of the elements E1 and E2 within the differential pairs PA′1 and PA′2 in the representations A′2, A′3 and A′4, the other representations of the symbol A′ are obtained.

(35) It will be noted that a reversal of the positioning of the elements of one of the differential pairs in a representation makes it possible to obtain another representation of the symbol A′ of the set ENS′1.

(36) It will be noted that binary values can be assigned to these representations. For example, the value 00 to the representation A′1, the value 01 to the representation A′2, the value 11 to the representation A′3 and the value 10 to the representation A′4.

(37) In this example, the set ENS′1 comprises only one symbol. Obviously, in practice, it will be possible to provide a greater number of symbols similar to the symbol A′ and having one or more differential pairs that can be arranged in different ways.

(38) In the operation S′1, it is possible to arrange a number of symbols A′ to form a reference pattern P′1. This “pattern” comprises, in the example illustrated, 9 symbols, each capable of coding two bits. It is therefore possible to code 22×9=262 144 different values. These values can be coded by using the following order of the symbols: VB1 (most significant), VB2, VB3, VB4, VB5, VB6, VB7, VB8 then VB9 (least significant).

(39) In the example illustrated, in the operation S′2, two patterns M′1 and M′2 have been created, in which two different numerical values are coded.

(40) More specifically, the binary value 10 00 00 01 00 10 10 00 01=132 257 has been coded in the pattern M′1 by following the order VB1 to VB9 and by using binary values defined above for the representations A′1, A′2, A′3, A′4. In the pattern M′2, the binary value 01 11 10 10 10 10 00 01 00=125572 has been coded. Obviously, conventionally, it is possible to obtain characters by means of these binary values, for example by using the ASCII code system, well known to those skilled in the art.

(41) FIG. 3 schematically shows an implementation of a method for marking an article or security device SUP using two patterns M1 and M2 as illustrated in FIG. 1, in which two different numerical information items are coded.

(42) This method comprises the step S1 for creation of an arrangement of symbols or “pattern” P1 by means of a set of symbols ENS1. The operation S2 is then implemented in order to obtain a pattern M1 in which a numerical information item is coded by means of the “pattern” P1 comprising 32 symbols. Reference can be made to the description above concerning FIG. 1 for more details concerning the operations S1 and S2. The pattern M1 and any other pattern also created by the operation S2 can then be stored on a computing device.

(43) The step S3 comprises a marking of the stored pattern M1, on an article or security device SUP. The expression “marking” can be understood to mean a printing, for example with visible or invisible ink, an etching, a deposition, a stamping, a calendaring, an application of a laser beam or any other operation making it possible to position the coding pattern M1 and any other coding pattern on the article or the security device. The article or security device SUP may be a label, a package, a cartridge, a container containing foodstuffs, nutraceutical products, pharmaceutical products or drinks, a bank slip, a credit card, a stamp, a revenue stamp, a tamper indicator, a secure document, a passport, an identity card, a driving license, an access card, a transport ticket, an admission ticket, a coupon, a printing form, a reflecting film, aluminium paper, a commercial article or, generally, an article or device that is to be furnished with a means of identification or coded data that is difficult to identify without appropriate equipment.

(44) The marking step S3 notably corresponds to a marking of the elements, E1 and E2 in the example illustrated, of the differential pairs of the symbols A, B, C, D. It will be noted that the article or security device SUP has, on its outer surface or its package, a scattering of elements similar to those of the coding pattern M1 but not as a whole forming a coding pattern. There is no marking intended to form an identifier on the article, only the elements of the differential pairs of the reference pattern M1 being marked on the article actually within the scattering of abovementioned undifferentiated elements. Thus, unlike the data matrices used in the prior art, all the marked elements correspond to a coded value information item in a coding pattern. By using a fine resolution, for example of the order of several hundreds of elements per inch (Dots Per Inch, DPI), for example between 150 and 600 DPI or preferably between 300 and 600 DPI, it is possible to mark patterns according to the invention that will not be detectable by a user but that only appropriate equipment comprising an electronic reading system will be able to detect and interpret. Such a resolution also makes it possible to mark a plurality of small patterns: the marking of the information is thus particularly robust because an alteration of one or even several patterns will not render all patterns illegible. The use of such a fine resolution also makes it possible to prevent the reproduction of a pattern, for example by means of a photocopier.

(45) In order to make a pattern according to the invention undetectable to the naked eye, it is also possible to mark patterns with parameter values that are similar (notably the values of the elements of a differential pair). More specifically, it is possible to choose parameter values that a human eye cannot discern but that an appliance can detect. It is also possible to use a coarse resolution, for example wider than 150 DPI, without in any way enabling a user to discern different elements that make up a pattern. Obviously, the pattern as a whole, or a plurality of adjacent patterns, may be visible to a user, who will see only a uniform area, for example uniformly coloured.

(46) It will be noted that the pattern M1 can be marked within a graphic element of the article or security device SUP, this graphic element possibly being an image or a logo, or a coded representation of another numerical information item, for example of one-dimensional, two-dimensional or three-dimensional barcodes, of scatter plots, of networks of lines or of data matrices.

(47) It should be noted that M1 and M2 may be used as first and second pattern, with corresponding reading conditions.

(48) As a non-limiting example, it is possible to mark patterns according to the invention in the bars of a barcode, M1 may thus be marked in the bars of a barcode or in the “white areas” separating the bars.

(49) In the example illustrated, simultaneously with the marking step S3, a certain number of other additional elements EADD of type E1 or E2 were marked outside the pattern M1. In the example illustrated, the additional elements EADD form a row surrounding the pattern M1. The additional elements are here aligned with the elements of the pattern M1, which is a way of making it difficult to read the coding pattern M1. The additional elements may also be more numerous, in numbers very much greater than the number of elements that form the coding pattern M1, and have different positionings.

(50) These additional elements EADD may form part, for example, of a graphic area of the security article or of the security device. The additional elements EADD may also serve to embed the coding pattern M1 to make it all the more difficult to detect. Since these additional elements are not arranged in the form of differential pairs in a reference pattern, they will not falsify the reading of the numerical information coded in the coding pattern M1. It will also be understood that these additional elements EADD may preexist on the article, in which case there is no need to proceed with their marking during the step S3.

(51) In all cases, it may be advantageous to choose a representation of the elements E1 and E2 which approximates as closely as possible the representation of the additional elements EADD so as to make the detection and the reading of the coding pattern M1 more difficult. It will be noted that a number of means can be used to make the marked pattern all the more undetectable to the naked eye. For example, it is possible to use an ink whose chemical nature makes it invisible to the naked eye but simply visible under specific lighting, for example using infrared or ultraviolet light. The composition of these inks may comprise one or more pigments and/or dyes which absorb in the visible or invisible of the electromagnetic spectrum and/or may comprise one or more pigments and/or dyes that are luminescent. Nonlimiting examples of appropriate pigments and/or of dyes that absorb in the visible or invisible of the electromagnetic spectrum include, by way of nonlimiting example, the derivatives of phthalocyanine but also the derivatives of perrylene, quaterylene type, substituted or not. Nonlimiting examples of appropriate luminescent pigments and/or dyes comprise the derivatives of lanthanides. The presence of pigment(s) and/or of dye(s) makes it possible to enhance and strengthen the security of the marking against counterfeiting. Some compounds mentioned above make it possible to confer traceability and/or authentication properties on the marking according to the invention. In fact, these particular compounds differ from the conventional inks and their detection, for example by chemical or physical analysis means, may make it possible to determine the origin of the marked product.

(52) It is also possible to mix the marked coding pattern or patterns with a noise, for example by incorporating the coding pattern in an environment of the surface of the article or security device SUP including irregularities or preexisting spots. These irregularities or these spots should preferably have a size and an appearance that are comparable to the size and the appearance of the marked coding patterns.

(53) The coding pattern M1 marked on the article or security device SUP, and any other additional coding pattern created in a similar way, may make it possible to code an information item enabling the security article or the security device SUP to be authenticated or even an information item relating to the use of the security article or of the security device SUP.

(54) It will be noted that using a set of symbols each comprising similar elements, and a reference pattern comprising a high number of symbols makes it possible to obtain a marking that has a uniform appearance, in which it is not possible to read the coded information without knowing the symbols, the representations of the symbols and the reference pattern used. Moreover, the use of differential pairs comprising two element having two possible parameter values such as the elements E1 and E2 illustrated here by way of example, makes it possible to obtain a pattern comprising as many elements E1 as elements E2, and therefore, a uniform appearance of the outer surface of the article or of the security device.

(55) It is possible to mark a number of coding patterns according to the invention on the article or security element SUP. It is possible to mark a number of identical patterns and also a number of different patterns. It is also possible to cover a surface of the article or security element SUP.

(56) As a nonlimiting example, it is possible to mark coding patterns according to the invention over the entire surface of a package, intended to cover an object. The reading of the coding patterns can then be implemented on the basis of any surface portion of the package covering the object. It will be possible for example to mark substantially transparent plastic films, or also opaque films of aluminium foil type. It will also be possible, using appropriate marking means, to mark coding patterns according to the invention on very rough or non-uniform surfaces, for example wine bottle stoppers or even on the corresponding seal.

(57) Moreover, certain articles that are marketed, for aesthetic reasons or constraints associated with their production, have little space available to support a marking. The marking according to the invention makes it possible to overcome these constraints. In practice, the pattern or patterns can be marked on supports having a reduced surface while remaining invisible to the naked eye, while retaining the reading robustness according to a method of the invention.

(58) FIG. 4 shows an implementation of a method for reading numerical information coded in a coding pattern according to the invention, marked on a surface of an article or security device SUP.

(59) Before the reading is implemented, a set of symbols, for example the set ENS1 already mentioned by way of example with reference to FIG. 1 or the set ENS′1 already mentioned by way of example with reference to FIG. 2, and one or more arrangements of symbols or reference patterns, are stored in a memory of a reading system.

(60) Then, in the example illustrated, the method comprises a step D1 in which an image of an area ZO1 of a surface of an article SUP is captured. The system suitable for implementing the step D1 may comprise a reading device such as a fixed or portable reader or scanner, a camera, a telephone equipped with a digital camera, a tablet equipped with a digital camera, and, generally, any means suitable for making the marked elements visible, for example lamps radiating in the infrared or ultraviolet ranges. The image obtained is then stored.

(61) An element identification step D2 is then implemented. It will notably be possible to identify the elements according to the knowledge of the symbols of a set of symbols, for example the set ENS1. For symbols whose elements are spots of varying shapes (for example, the symbols of the set ENS1 illustrated in FIG. 1), a plurality of elements, for example of type E1, E2, are detected within the image obtained in the step D1. Furthermore, it is possible to measure, for each element, a parameter value and store the measured values.

(62) Then, in the step D3, the symbols can be identified by means of a stored reference pattern, for example the arrangement of symbols P1 illustrated in FIG. 1. Since the area ZO1 may include additional elements, for example additional elements EADD, the identification of the symbols may comprise a number of steps up to the identification of the symbols of the coding pattern or patterns by means of the single reference pattern stored.

(63) There now follows a description of a simplified example of implementation of this identification with reference to the example of FIG. 1, it being understood that the procedure would be similar in the case of the example of FIG. 2. We can begin by matching the arrangement of symbols P1 with a first group of elements GEL through a study window of the reading device which comprises this group of elements GEL (comprising a group of 64 elements positioned in a grid). By matching the arrangement of symbols P1, that is to say the stored reference pattern, with the group of elements GEL, it will be noted that a certain number of pairs of symbols of the group GEL corresponding to the arrangement of symbols P1 are not differential pairs. The pairs ND1 and ND2 comprise pairs of elements arranged as two pairs of symbols of the arrangement P1, but these pairs are not differential pairs. In practice, they respectively comprise two elements E2 and two elements E1. In both cases, there is no parameter difference between the two elements. It will be noted that two different elements do not always form a differential pair. It is in particular a good idea to measure the difference between the two parameter values of the two elements, to compare it to a threshold, or to measure the difference between each parameter value and an average value.

(64) The study window of the reading device may have a size at least equal to that of a marked coding pattern. The study window may notably have dimensions (width and height) which are twice those of a marked coding pattern.

(65) It is therefore possible to use the parameter values obtained in the step D2 to determine whether the pairs of elements are differential pairs. It will also be possible to compare the difference between the values to a stored threshold, or even to check whether the values of each parameter are respectively greater than or less than another value, for example an average value. This average value may be stored previously or be measured and calculated in the step D1 or in the step D2 by observing the surface of the article.

(66) The non-differential pairs ND1 and ND2 obtained by matching the arrangement of symbols P1 with the group of elements GEL shows that the elements of the group of elements GEL do not form a coding pattern comprising symbols arranged according to the arrangement or reference pattern P1.

(67) The reading device or the study window is then displaced relative to the article to match the reference pattern P1 with another group of elements, for example the group of elements IM1 (FIG. 4). All the elements of the group IM1 correspond to differential pairs of elements of symbols arranged according to the reference pattern P1. It will be noted for example that the differential pair PD1 corresponds to the symbol corresponding to the most significant bit MSB1, the differential pair PD2 corresponds to the symbol SB2, the differential pair PD3 corresponds to the symbol SB3, the differential pair PD4 corresponds to the symbol SB4 and the differential pair PD5 corresponds to the symbol corresponding to the least significant bit LSB1.

(68) It is then estimated that the coding pattern has been found within the group of elements IM1. It will be noted that, by browsing over the groups of elements marked on the article or the security device SUP and by matching the reference pattern P1 with groups of elements, a representation of a coding pattern coding a numerical information item has been found, and without using any coordinate system indicating the placement of the coding pattern on the article.

(69) It will be noted that it is possible not to require the recognition of all the symbols of the reference pattern P1. It is possible in this case to calculate the number of symbols identified, and compare this calculated number to a probability threshold. If the calculated number is greater than this threshold, it can be estimated that a coding pattern produced by means of a reference pattern according to the invention is present. The pattern is thus very robust, an alteration of symbols of a pattern not preventing the recognition of the reference pattern and reading of the symbols which have not been damaged.

(70) As a nonlimiting example, for a reference pattern comprising 128 symbols, a probability threshold can be taken that is of the order of 30 symbols identified out of 128, that is to say 24%. Other probability thresholds can be used, it is possible in particular to choose a high threshold in order to determine with certainty that the coding pattern is identified.

(71) Finally, once the symbols have been identified as indicated previously, the information coded by the marked elements forming a coding pattern can be read in a step D4. This reading can be done only with a knowledge of the order of reading of the arrangement of symbols. The order defined hereinabove can be used, in which the reading is conducted from top to bottom and from left to right. The knowledge of the set of symbols and of their respective representations makes it possible to detect the binary values associated with the marked symbols. The parameter values measured in the step D2 are used to determine the representation used. The reading of the binary value of each symbol makes it possible to determine the binary value coded in the marked coding pattern.

(72) The step D4 may also comprise conventional error correction steps in order to determine the representations of the symbols that have not been identified.

(73) Furthermore, in the implementation of the reading method, a margin of displacement in height and in width can be tolerated for each marked element. As a nonlimiting example, slight diameter differences in the elements do not affect the reading. Nor do slight positional differences affect the reading.

(74) There now follows a more detailed description, referring more particularly to FIGS. 5 and 6, of a variant of the invention.

(75) FIG. 5 shows a coding pattern PCO in which an information item is coded according to an arrangement of eight symbols in which the elements of the symbols are differential pairs of image pixels. The eight symbols are arranged in a matrix of 4×4 pixels. Each pixel is characterized by a parameter which may be the one of the colorimetric components. The symbols of this pattern PCO thus each comprise differential pairs of elements similar to the symbols of the set ENS1 of FIG. 1, but in which the elements are pixels.

(76) Furthermore, the pairs of pixels are differential pairs whose representation is defined by the values of a colorimetric component, for example the hue, the saturation or the lightness, of each of the pixels of the differential pair. More specifically, one of the pixels of the differential pair has a high value denoted H and the other has a low value denoted L. By reversing the respective position of these levels, different numerical information can be coded.

(77) The coding pattern PCO is intended to be included in an image, as illustrated in FIG. 6. In this figure, an initial image IMGI is represented which conventionally comprises a plurality of pixels and a group of 16 pixels GPI forming a 4×4 matrix of pixels. It is within the group of pixels GPI that the coding pattern PCO will be included. The initial image IMGI may be a digital image, stored in a memory and modifiable by processing means, for example equipped with a microprocessor and/or logic circuits. Once modified to include the coding pattern PCO, this image may be marked on a surface of a security article or element.

(78) Each pixel of the group of pixels GPI has a value of a chosen colorimetric component denoted VIJ, I ranging from 1 to 4 indicating the column of the pixel in the 4×4 matrix, and J ranging from 1 to 4 indicating the row of the pixel in the 4×4 matrix. It is then possible to check whether each pair of pixels in the group of pixels GPI corresponds to a differential pair according to the pattern PCO.

(79) By comparing the value of the pixels V11 and V22 of the pair of pixels PC1, if V11 is greater than V22 and if the difference between the two values is less than a threshold, in the group of pixels GPI, then it is necessary to modify the value of the colorimetric component of these pixels, for example by increasing V11 and by reducing V22 by the same value to obtain the modified pixels V′11 and V′22 of the modified image IMGM.

(80) The increase and the reduction by the same value is particularly advantageous; thus, the average value of the parameter within the pair PC1 is the same for the values V11 and V22 and for the values V′11 and V′22.

(81) Other pairs of pixels can thus be modified. For example, the pixels of the pair PC4 can have values V24 and V34 but V24 may be greater than V34. In other words, V24 corresponds to a high value and V34 to a low value. In order to mark the pair PC4 of the pattern PCO, the values of the pixels can be reversed, and the values V′24 and V′34 are obtained. It is also possible to reverse, increase and reduce as above, the values of the pixels, for example the values of the pixels of the pair PC6, to obtain the values V′42 and V′43.

(82) The values of the pixels of the remaining pairs of the group of pixels GPI have not been modified, because the values of the pixels of the initial image may also already correspond to differential pairs of the coding pattern PCO.

(83) Thus, within the modified image IMGM (here marked on an article or security device SUPC), the pattern PCO has been marked by modifying the values of pixels of the initial image IMGI. The modifications of pixel values are imperceptible to a user, since they are applied at neighbouring pixels in images that may comprise millions of pixels.

(84) It will be noted that it is also possible to use other colorimetric components, for example components of the Red-Green-Blue system.

(85) Moreover, in order to determine whether, in a pair of pixels, one has a high value and the other has a low value, it is possible to compare these values to an average value obtained by a calculation of the value of the component for a number of neighbouring pixels. It is also possible to calculate an average value relating to another component. As a non-limiting example, the red level of the neighbouring pixels of a differential pair may define the average value or a threshold to which the values of the pair are compared.

(86) There is also proposed a system suitable for implementing a marking method, for example the method of FIG. 3. In one embodiment, this system may comprise a memory configured to store a set of symbols, an arrangement of these symbols forming a reference pattern, and numerical information to be coded. The system may comprise means for marking on a surface of an article or a security device, for example means for printing, etching, stamping, calendaring, deposition, application of a laser beam or any other method making it possible to modify portions of the surface concerned. These marking means can make it possible to mark elements invisible to the naked eye.

(87) There is also proposed a system suitable for implementing a reading method, for example the method of FIG. 4. This system may comprise means for storing an arrangement of symbols forming a reference pattern and a set of symbols, and means suitable for capturing an image such as a camera, a fixed or portable reader or scanner, a portable telephone equipped with a camera, a tablet equipped with a camera, means for revealing the marked elements such as a lamp radiating in the ultraviolet or in the infrared, and processing means suitable for identifying the elements and the symbols on the basis of the captured image comprising, for example, a microprocessor and/or logic circuits.

(88) It will be noted that, according to one aspect, the coding patterns obtained may be used to authenticate an article, and thus enhance its traceability and detect counterfeit articles. It is also possible to mark information relating to the use of the article.

(89) A marking of coding patterns according to the invention has a particularly high robustness. It will be possible to mark patterns by using a fine resolution, for example 300 DPI, so as to obtain patterns that individually have a size less than a square millimeter, in order, finally, to cover a surface for example of the order of one or more square centimeters. Obviously, other resolutions and dimensions are possible.

(90) As a non-limiting example, such coding patterns according to the invention can be marked on a surface of the order of a square centimeter. These patterns may be visible overall or invisible for a user. The entire marked surface may have dimensions that are, for example, similar to a data matrix. In the case where the patterns are visible, they may have a uniform appearance for a user, or equally be embedded in an image.

(91) Any alteration of the marked surface will not prevent the detection of the reference pattern used, nor the reading of the numerical information coded in the patterns. The surface may, for example, have been altered by means of a pen or a pencil, it may have been creased, folded, scratched or torn. Such alterations may have been combined without preventing the reading of the numerical information coded in the patterns.

(92) By contrast, such alteration processes applied to conventional markings of barcode or data matrix type would make the reading of the information contained in these markings totally impossible.

(93) In an exemplary embodiment, numerical information items are encoded into an original packaging design during prepress operations. In one variant, a single additional step is required during prepress operations to add the code pattern to the packaging, making it extremely simple to integrate a code pattern in an existing production line. Manufacturers of the packaging or items to be marked with a code pattern do not have to change the design of their products and packaging to accommodate the code pattern. In an exemplary variant, the code pattern can be added to any design and color. In another exemplary variant, the addition of the code pattern to existing packaging can be used with any of the classic printing systems, such as offset, flexo, or inkjet printing.

(94) In another exemplary embodiment, an application installed on a smart phone with a macro camera or an intelligent camera system is used to identify the presence of a numerical information item. In one variant, the presence of a code pattern can be detected, and an authentication provided to the user. In an exemplary embodiment, online authentication checks are made through mobile connections to a secure authentication server.

(95) In another variant, a code pattern which has been detected by the smart phone or intelligent camera system can further be decoded by an application on the smart phone or intelligent camera system, and the numerical information item provided to the user.

(96) Furthermore, the use of an additional pattern associated with different reading conditions makes more complex the reading or the reproduction of the pattern by a counterfeiter.

(97) On FIG. 7, a marking according to an aspect of the invention has been represented. The marking is marked on a surface 100.

(98) The marking comprises a first pattern 101, a pattern as described by reference to FIGS. 1 to 6. This first pattern comprises elements schematically represented as ellipsis 103.

(99) The marking also comprises a second pattern 102 comprising elements schematically represented by squares 104.

(100) In the example of FIG. 7, the first pattern has a first resolution and the second pattern has a second resolution. The resolution of the first pattern is the smallest dimension 105 of an element 103. The resolution of the second pattern is the smallest dimension 106 of an element 104.

(101) The first resolution 105 is chosen in order to be 5 times smaller than the second resolution 106, so that the first pattern 101 may be readable even if it is superposed on the second pattern 102.

(102) On FIG. 8, a marking according to another aspect of the invention has been represented. The marking is marked on a surface 100.

(103) The marking comprises a first pattern 111, a pattern as described by reference to FIGS. 1 to 6, and a second pattern 112, respectively comprising elements 113 and 114.

(104) In this example, different inks are used so that the two patterns may be read under distinct reading conditions. A black or colored ink is used for printing the first pattern and a second ink is chosen in the group formed by black or colored IR transparent ink is used for printing the second pattern. Typical black or colored ink printed by inkjet or laser techniques are already known by the one skilled in the art and sold under the market by know providers such as Hewlett Packard, Olivetti i-jet or Canon. Typical black or colored IR transparent inks are also know by the one skilled in the art and described in EP1789505B1 or WO2007133533 A1.

(105) In this example, the resolution of each pattern may be the same or different.