Method for authenticating a predetermined product and device for authenticating a predetermined product

Abstract

The invention relates to a method for authenticating a predetermined product comprising predetermined phosphorescent compounds, the method comprising the following steps: A. acquiring a first image (I1) of phosphorescence radiation (RP) induced by an excitation beam (FE) illuminating phosphorescent compounds of the product; B. performing a colorimetric analysis of the first image (I1) so as to determine a first measurement of a colour of the phosphorescence radiation; and C. comparing the first measurement of the colour of the phosphorescence radiation and a so-called reference datum determined prior to the implementation of the method on the basis of the phosphorescent compounds and a colour of the product.

Description

DESCRIPTION Title of the invention: Method for authenticating a predetermined product and Device for authenticating a predetermined product Technical field:

[0001] The present invention relates to the field of product authentication and more particularly the authentication of a product by colorimetric method. Prior art:

[0002] In many applications, it is crucial to identify fraudulent reproductions. Among the sectors most prone to these counterfeits are the luxury goods industry, the pharmaceutical industry, the production of certified documents, and the alcohol industry.

[0003] To detect imitations, fluorescent inks, known as "security inks," are increasingly used. Their presence helps prove the authenticity of a product. Products marked with these inks can be, for example, banknotes, identity cards, official documents (stamps, driving licenses, etc.).

[0004] Documents WO 97 / 10307 and FR 2909095 describe such security inks. These inks are colorless, invisible to the naked eye, and visible only under light excitation (under ultraviolet light for example).

[0005] The luminescent properties of these inks are obtained by chelates or complexes of rare earths. The composition of the ink generally includes, in addition, a solvent and a binder, obtained from a resin (polymer).

[0006] US Patent 5,135,569 describes a fluorescent ink visible to the naked eye that can mark porous substrates. The ink is formed from a black pigment, a fluorophore, and a solvent. The solvent allows the porous substrate to be impregnated with the fluorophore. Once the ink is deposited on the substrate, the fluorophore is located, at the level of the pores of the substrate, under the colored pigment. To authenticate the article, it is necessary to at least partially remove the top layer of black pigment to check whether the marking has a fluorescent underlying layer. More complex inks may contain two types of dyes, the first being fluorescent and the second having an absorption band overlapping the emission band of the first dye, or being located at longer wavelengths, so as to give a dark coloration to the ink. The ink contains a rare earth compound (US 2005 / 0279248). The ink, once deposited on the substrate, allows visible patterns to be formed which produce a particular luminescent signal: the luminescent signal is composed of a broad fluorescence band, due to the first dye, and a narrow fluorescence band due to the presence of the rare earth compound.However, such inks exhibit fluorescence inhibition phenomena (or "quenching") which can significantly reduce the fluorescence of the patterns printed on the substrate and therefore the intensity of the signal to be authenticated.

[0007] Application FR3025206A1 describes an easy-to-produce luminous ink composition for marking different substrates, the marking having to be very bright, difficult to copy and, at the same time, easily identifiable. This objective is achieved by a colored and fluorescent ink, comprising in particular fluorescent elements which are organo-lanthanide complexes.

[0008] The fluorescent ink described in this application FR3025206A1 is satisfactory for carrying out the authentication of a product. However, the authentication methods associated with this ink require a spectrophotometer which is a relatively expensive and complex device to use.

[0009] Also, an object of the invention and a method (and an associated device) for authenticating a predetermined product comprising predetermined phosphorescent compounds that can be implemented by any person, without a complex and expensive device. In particular, the method of the invention is particularly suitable for being implemented by a smartphone. Summary of the invention:

[0010] For this purpose, an object of the invention is a method for colorimetric authentication of a predetermined product comprising predetermined phosphorescent compounds, said method comprising the following steps: A- Acquiring a first image of phosphorescence radiation induced by an excitation beam illuminating phosphorescent compounds of said product B- Carrying out a colorimetric analysis of the first image so as to determine a first measurement of a color of the phosphorescence radiation C- Comparing the first measurement of the color of the phosphorescence radiation and a so-called reference data determined prior to the implementation of the method as a function of the phosphorescent compounds and a color of said product.

[0011] According to one embodiment, the method comprises a subsequent step D consisting of determining an authenticity of the product as a function of said step C of comparison between the first measurement and the reference data.

[0012] Preferably, the first measurement is a first triplet in a first color space and the reference data is a second triplet in said first color space, said step C consisting of calculating a color difference between the first and second triplet or a color difference between the first and second triplet relative to the second triplet. Even more preferably, step D consists of determining that the product is authentic when the color difference relative to the second triplet is less than or equal to 5%.

[0013] According to one embodiment, the phosphorescent compounds are incorporated into said product in a solid, liquid, gel, polymer, or biocompatible matrix, the method comprising a subsequent step E, implemented only when it is determined in step D that the product is not authentic, consisting of calculating a concentration of the phosphorescent compounds from said color difference Δ and a table or a correspondence function determining a concentration of the phosphorescent compounds in said product as a function of the color difference, said correspondence table being determined prior to the implementation of the process.

[0014] According to one embodiment, the method is implemented by a processing unit of a smartphone and comprising a step 00, implemented prior to step A and consisting of acquiring a second image of the product and then determining in the second image a region of said product comprising the phosphorescent compounds, and comprising a step 01, implemented prior to step A, consisting of turning on a flash lamp of the smartphone so as to generate the excitation beam, the first image then being acquired in step B so as to acquire said region, and said first measurement of step B being carried out by an average of a colorimetric measurement of pixels of the first image detecting said region.

[0015] Another subject of the invention is a computer program product comprising code instructions making it possible to carry out the steps of the method of the invention, when said program is executed on a computer.

[0016] Another subject of the invention is a device for colorimetric authentication of a predetermined product comprising predetermined phosphorescent compounds, the device comprising a matrix sensor and a processing unit configured to implement the following steps: A- acquiring, via the matrix sensor, a first image of phosphorescence radiation induced by an excitation beam illuminating phosphorescent compounds of said product B- performing a colorimetric analysis of the first image so as to determine a first measurement of a color of the phosphorescence radiation C- comparing the first measurement of the color of the phosphorescence radiation and a so-called reference data stored in the processing unit and determined as a function of the phosphorescent compounds and a color of said product.

[0017] According to one embodiment, the processing unit is configured to implement a subsequent step D consisting of determining an authenticity of the product as a function of said step C of comparison between the first measurement and the reference data. Preferably, the device is a smartphone comprising a screen, said matrix sensor being the matrix sensor of a camera of the smartphone, the processing unit being configured to display on the screen a graphic message representative of the authenticity of the product following step D.

[0018] A final object of the invention is a system for colorimetric authentication of a predetermined product comprising predetermined phosphorescent compounds, said system comprising an authentication device according to the invention and comprising a light source adapted to generate said excitation beam illuminating the phosphorescent compounds of said product so as to induce phosphorescence radiation.

[0019] Preferably, the light source is adapted so that the excitation beam has wavelengths in a spectral range from 200 nm to 900 nm.

[0020] According to one embodiment of the authentication system, the processing unit is configured to acquire the first image between 0.1 and 10 seconds after the generation of the excitation beam.

[0021] According to one embodiment of the authentication system, the system is a smartphone, said matrix sensor being the matrix sensor of a camera of the smartphone, and the light source being a flash lamp of the smartphone. Brief description of the figures:

[0022] Other characteristics, details and advantages of the invention will emerge from reading the description given with reference to the appended drawings given by way of example and which represent, respectively:

[0023] [Fig.1A], a schematic view of a system according to the invention for colorimetric authentication of a predetermined product,

[0024] [Fig.1B], the steps of the colorimetric authentication method according to the invention,

[0025] [Fig.2], the steps of the method according to a variant of the preferred embodiment,

[0026] [Fig.3] the steps of a method according to an embodiment of the authentication method of Figure 1B,

[0027] [Fig.4], an example of the second image (left) and the first image (right) according to an embodiment in which the labeling of the product by the compounds is carried out in the form of a patch defining a region,

[0028] In the figures, unless otherwise indicated, the elements are not to scale and identical references designate identical elements. Detailed description:

[0029] Figure 1A schematically illustrates a system SA according to the invention for colorimetric authentication of a predetermined product P. The system SA comprises a colorimetric authentication device DA according to the invention and a light source SL. According to a preferred embodiment which will be detailed later, the system SA is a smartphone comprising in particular a camera and a flash lamp.

[0030] Figure 1B illustrates the steps of the colorimetric authentication method according to the invention, which is particularly suitable for being implemented by a processing unit UT of the DA device of the invention. More generally, all the steps of the method of the invention are particularly suitable for being implemented by computer.

[0031] In order to enable its authentication, the product P comprises a marking in at least one region R of the product P via one or more predetermined phosphorescent compounds CP. Here, a phosphorescent compound is distinguished from a fluorescent compound. Fluorescence is characterized by the emission of a photon very rapidly (lifetime typically ranging from picoseconds to a few nanoseconds). This rapidity is explained by the fact that fluorescent emission is characterized by an emission in which the molecule remains in the same spin state between its electronically excited state, denoted "S1", and its ground state denoted "S0". Phosphorescence, on the other hand, is a radiative transition between two different spin states with a significantly longer lifetime (of the order of a microsecond or more). After absorption of the photon, the molecule is in a spin state identical to that of the ground state. An inter-system conversion can take place and The electron moves from the S1 state to another higher spin state that is lower in energy than this S1 state. The radiative transition is normally forbidden between two different spin states but it still takes place but at a longer time than fluorescence. Thermal excitation towards the S0 state makes it emit light in a delayed manner, dependent on the temperature. The higher it is, the more quickly the light will be re-emitted.

[0032] The marking techniques, the phosphorescent compounds CP or the way in which they are formulated are not specific to the invention and an exhaustive description of these elements would go beyond the scope of the invention. By way of non-limiting example, the marking is carried out in the form of a patch, an ink, a strip or more generally on any substrate allowing the CP compounds to be supported in a durable manner on or in the product P. Thus, according to one embodiment, the CP compounds are formulated in printable ink and printed on substrates of various colors or directly on the product P.

[0033] Alternatively, according to another embodiment, the CP compounds are incorporated into a solid, liquid, gel, polymer, or even biological matrix (potentially biodegradable, biocompatible). Thus, according to one embodiment, the CP compounds are incorporated directly into the product P. This embodiment is particularly interesting when the product P is a cream, a capsule or lozenge, a liquid or even a gel.

[0034] The light source SL is not specific to the invention and can be any source capable of inducing the generation of phosphorescence radiation RP by illuminating the phosphorescent compounds CP with an excitation beam FE.

[0035] Preferably, the SL light source is adapted so that the FE excitation beam has wavelengths in a spectral range from 200 nm to 900 nm, preferably from 350 to 780 nm. This makes it possible to excite phosphorescence with a SL laser source that is very accessible to the general public. For example, the SL light source is the flash lamp of a smartphone emitting white light typically covering a spectral range from 400 to 780 nm.

[0036] The authentication device DA comprises the processing unit UT and a matrix sensor CM. The processing unit UT is a generic computer and is configured to implement the steps of the method of Figure 1B.

[0037] In a step A, the processing unit UT, by means of the matrix sensor CM, acquires a first image I1 of the phosphorescence radiation RP induced by the excitation beam FE illuminating phosphorescent compounds CP of the product P.

[0038] Following step A, the first image I1 is digitized by the processing unit UT in order to perform a colorimetric analysis in a step B. More precisely, in step B, the processing unit UT performs a colorimetric analysis of the first image I1 in order to determine a first measurement of the color of the phosphorescence radiation RP. Indeed, just like the central emission wavelength, the color of the phosphorescence radiation RP is a signature specific to the compounds to be detected CP. The colorimetric analysis of the image I1 is therefore an elegant and simple way to determine whether the detected radiation RP actually comes from the compounds to be detected CP. Thus, it is possible to determine whether the product P is authentic. Compared to spectrophotometry, this colorimetric analysis can be performed entirely by computer, without requiring complex or expensive equipment and without requiring advanced technical knowledge.

[0039] This colorimetric analysis step B is a step known in itself aimed at precisely determining the coordinates of the color of the phosphorescence radiation RP in a first colorimetric space. As a non-limiting example, the first colorimetric space is the RGB, CIELAB or CIELUV space. These different colorimetric spaces are linked by matrices or equation systems allowing the passage from one space to another space. Step B therefore allows the determination of a first triplet of values ​​which are the coordinates of the color of the phosphorescence radiation RE in the first colorimetric space.

[0040] It is noted that, in order to carry out this colorimetric analysis, it is essential that the CM matrix sensor is a wideband sensor, or comprises a plurality of mono-spectral sensors detecting the same field of view. The CP compounds being predetermined, the matrix sensor will be adapted to the spectral range of phosphorescence emission of the CP compounds in order to allow the detection and then the colorimetric analysis of the phosphorescence radiation RP. Thus, according to one embodiment, the matrix sensor CM is capable of detecting at least one spectral range centered on the central wavelength of the phosphorescence radiation RP and of spectral width greater than or equal to the width at half-maximum of the phosphorescence emission of the CP compounds.

[0041] Preferably, step B comprises a first sub-step consisting of determining in the first image I1 the region(s) R of the product comprising the phosphorescent compounds CP. This first sub-step is carried out by image processing. For example, according to one embodiment, the region P is a patch (or a strip) fixed on the product P and of a different color from the product P. Thus, the region P is physically delimited and identifiable in the image and the first sub-step can be carried out by edge detection techniques, typically with a Canny filter or a Sobel filter. According to another embodiment, the region P is in no way distinguishable from the native material except that it contains the phosphorescent agents in dispersed mode. In the two embodiments above, the activation of the color resulting from the phosphorescence is done by illumination of the flash of the portable device.The image is captured according to different scenarios, after, during and / or before illumination.

[0042] After this first sub-step, step B comprises a second sub-step consisting of determining the color of each pixel of the region(s) P in the image I1 determined in the first sub-step. In a third sub-step, the processing unit UT determines the first measurement by the average of the color of the pixels of the region(s) P in the image I1. This average corresponds to the average of the colorimetric coordinates of the pixels.

[0043] In a step C, the first measurement of the color of the phosphorescence radiation obtained in step B is compared with a so-called reference data determined prior to the implementation of the method. The reference data corresponds to the expected color of the radiation of RP phosphorescence taking into account the color of the product P and the phosphorescent emission of the compound CP and the illumination used. Indeed, as is known per se, a measurement of color depends on illumination and detection. An example of this principle is metamerism. Two metameric or homochromic colors are two visible lights whose physical spectrum is different, but which human vision does not differentiate. The light that illuminates colored surfaces participates in the formation of the light spectrum that reaches the eye. Two surfaces can appear identical under one illumination and appear to be different colors with illumination of a different spectral distribution.

[0044] Preferably, the first measurement and the reference data are defined in the same color space via respectively a first triplet and a second triplet (after a possible conversion from a second color space) in order to facilitate their comparison.

[0045] As an example, Table 1 below presents a series of ten reference data (“with flash” measurements) which are color measurements in the Lch space of a cosmetic cream comprising a C1 concentration of phosphorescent compounds CP and illuminated by a flash lamp in order to stimulate the emission of the phosphorescent compounds CP. In Table 1, the reference data are compared to color measurements without illumination by flash lamp of the phosphorescent compounds CP (“without flash” measurements).

[0046] Table 1: Concentration C1 series L C1 without c C1 without h C1 without L C1 with c C1 with h C1 with flash flash flash flash flash flash 1 83 4.37 124 83 11.68 140 2 83 3.77 121 83 11.03 139 3 83 3.26 123 83 11.68 140 4 83 3.77 121 83 10.59 141 5 83 3.77 121 83 11.87 141 6 83 3.77 121 83 11.68 140 7 83 4.28 120 83 10.58 141 8 84 3.76 121 83 11.67 140 9 84 3.77 121 83 11.02 139 10 84 4.28 120 83 11.67 140

[0047] By averaging to reduce the variability inherent in these measurements, we calculate the mean values ​​for the reference data taken with flash lamp which are . Table 2, which presents a series of ten data which are color measurements in the Lch space of the same cosmetic cream as for Table 1 but not including phosphorescent compounds CP (concentration C0=0 Mol / g). For comparison, these data are taken with and without flash lamp illumination.

[0049] Table 2: Concentration C0 series L C0 without c C0 without h C0 without L C0 with c C0 with h C0 with flash flash flash flash flash flash 1 83 3.36 129 83 10.04 136 2 82 4.76 110 81 9.6 137 3 83 3.77 121 82 10.22 137 4 82 4.25 115 82 10.06 136 5 79 3.73 110 82 10.71 136 6 83 4.22 110 82 11.49 132 7 82 5.29 110 82 11.66 134 8 83 4.74 110 83 11.63 134 9 83 5.28 106 82 11.98 131 10 83 5.84 102 82 12.61 132

[0050] By averaging to reduce the variability inherent in these measurements, we obtain average values ​​for the flash lamp data which are . -but not necessarily- implemented by the processing unit UT. Indeed, according to one embodiment, the reference data is stored on a medium readable by the processing unit UT, located (removable storage medium or not) or not located (for example the “cloud”) and the comparison step is carried out directly by the processing unit.

[0052] In the embodiment where the method is implemented with the processor of a smartphone, the reference data selected by the processor for the comparison in step C is data acquired with or without the flash lamp of the smartphone lit depending on whether the measurement of the color of the phosphorescence radiation was obtained in step B with or without the flash lamp of the smartphone lit.

[0053] Alternatively, according to another embodiment, the reference data is stored on a physical medium. By way of non-limiting example, the reference data is readable on a paper medium. Thus, the comparison step C is carried out directly by the user by comparing the value of the reference data and the first measurement.

[0054] Finally, the method of Figure 1B includes a step D consisting of determining the authenticity of the product based on the comparison of step C between the first measurement and the reference data.

[0055] Just like step C, step D is preferentially - but not necessarily - implemented by the processing unit UT.

[0056] In the simplest implementation, step D consists of determining that the product is authentic when the comparison step determines that the color of the first measurement is identical to that of the reference data. This is typically the case when the first measurement and the reference data are defined in the same color space via the first triplet and the second triplet respectively and the coordinates of the first triplet are identical to those of the second triplet.

[0057] According to a preferred embodiment noted MP, the first measurement and the reference data are defined in the same color space via respectively the first triplet and the second triplet and step C then consists of calculating a color difference between the first and the second triplet or a difference between the first and the second triplet relative to the second triplet ΔE / E2. Step D then consists of determining that the predetermined product is authentic when the color difference ΔE / E2 relative to the second triplet is less than or equal to 10%, preferably 5% or when the color difference ΔE is less than or equal to 1.

[0058] Indeed, through numerous experiments, the inventors determined that a threshold of 5% was suitable for determining that the product was authentic, taking into account the inherent variability of the measurement, under good measurement conditions (good quality image, high precision of the concentration of the compounds, etc.) while the threshold of 10% was sufficiently wide for degraded measurement conditions.

[0059] For example, the first measurement and the reference data are described in the two-dimensional space called CIE 1976. This space is derived from the CIE 1931 space. In the CIE 1931 space, each color is defined by a triplet (X, Y, Z) or a triplet (x, y, z). In the CIE 1976 space, each color is defined by two coordinates (u', v') defined as follows:

[0060] [Math.1]

[0061] In this CIE 1976 space, a color difference between the first measurement and the reference data is then worth:

[0062] [Math.2] and with

[0063] Here, the triplet (u'w, v'w, Yw) corresponds to the colorimetric coordinates of white. ( ) and ( ) are the first and second triplet and are the clarity of the first measure and the reference data ( ) and ( ) are the parameters characterizing the chrominance and to the reference data respectively.

[0064] The color difference relative to the second triplet is then: √ .

[0065] So when the relative color difference is less than or equal to the predetermined threshold of 10% (or preferably 5%), we determine in step D that the product is authentic.

[0066] The method of the invention (and the associated SA system) thus allows authentication of a predetermined product that can be implemented without requiring advanced technical knowledge and without requiring a complex and relatively expensive device such as a spectrophotometer. Furthermore, as detailed in the method according to the embodiment of Figure 3, the authentication is particularly suitable for implementation on a smartphone via a dedicated application.

[0067] However, it is specified that step D is not necessarily implemented by computer. According to one embodiment, steps A to C are implemented by computer and step D is performed directly by the user. For example, the user is aware of the predetermined threshold and performs the comparison between the color difference between the first and second triplet and the predetermined threshold itself.

[0068] Furthermore, according to a first variant, the method of the invention is implemented by implementing steps A to D and according to a second variant the method of the invention is implemented by implementing only steps A to C. Indeed, the final step D can be entirely separated temporally and spatially from steps A to C. For example, steps A to C can be implemented by a first user via a computer and step D can be implemented by a second user who alone has knowledge of the predetermined threshold.

[0069] In the embodiment where the compounds are formulated in a matrix so as to be fixed on the product P thus defining a region R, it is preferable that this matrix is ​​in a color different from the product P. Thus, the identification by image processing of the region R in the first image I1 is facilitated. By "a color different from the product", it is meant here that the region R comprising the compounds CP and the product P have a color difference greater than or equal to 5, preferably greater than or equal to 10. This embodiment is particularly relevant when the compounds CP are printed or formulated in the form of a patch or a strip.

[0070] Figure 2 schematically illustrates the steps of the method according to a variant of the MP embodiment. In this embodiment, the phosphorescent compounds are incorporated directly into the product P, in a solid, liquid, gel, polymer, or even biocompatible matrix.

[0071] In this embodiment, prior to implementing step A of the method, a table or a correspondence function is determined determining a concentration of the phosphorescent compounds in the product as a function of the color difference Δ.

[0072] According to one embodiment, the table or the correspondence function is physically readable by the user in the form of a table or a graph representing the evolution of the concentration of the phosphorescent compounds as a function of the color difference Δ

[0073] Alternatively, the mapping table or function is digitally readable by the UT processing unit.

[0074] After implementing steps A to D previously detailed, the method of Figure 2 includes a subsequent step E, implemented only when it is determined in step D that the product is not authentic, consisting of calculating a concentration of the phosphorescent compounds in the product P from the color difference and the table or the correspondence function.

[0075] Indeed, since the theoretical concentration of phosphorescent compounds CP in the authentic product is known, knowledge of the effective concentration of phosphorescent compounds CP in the non-authentic product P makes it possible to determine a possible dilution of the product P.

[0076] For example, the authentic product P is a cream or capsule comprising a predetermined composition and a theoretical concentration C1 of compounds CP. By implementing the method of the invention, in step D, it is determined that the product CP is not authentic. In step E, it is calculated that the effective concentration of phosphorescent compounds CP in the non-authentic product P is C2 (with C2 <C1). Il est donc possible de déterminer que le produit P a été dilué par un facteur C1 / C2.

[0077] For example, this table can be determined from data such as those in Table 1 presented above and from Table 3 presented below, which presents a series of ten reference data which are color measurements in the Lch space of the same cosmetic cream as for Table 1 but with a concentration of phosphorescent compounds C2=2C1Mol / g. For comparison, these reference data are taken with and without illumination by flash lamp.

[0078] Table 3: C2 concentration L series C2 without c C2 without h C2 without L C2 with c C2 with h C2 with flash flash flash flash flash flash 1 82 3.52 135 82 9.07 144 2 82 3.04 139 82 9.28 146 3 82 2.88 132 81 9.93 146 4 82 2.88 132 82 9.93 146 5 82 2.4 137 82 9.93 146 6 82 3.04 139 82 10.57 146 7 82 2.87 132 83 10.55 146 8 83 3.03 139 83 10.55 146 9 83 3.5 135 83 10.97 144 10 84 3.5 135 83 10.54 146

[0079] With this table 3, we can calculate the average values ​​of the triplet for the reference data taken with flash lamp with concentration C2. We can then calculate the color difference between the triplet associated with concentration C1 and the triplet associated with concentration C2. Thus, we can associate with this color difference value a dilution of a factor C2 / C1=2 for this specific case.

[0080] According to a preferred embodiment of the system SA of the invention, the system SA is a smartphone. In this embodiment, the matrix sensor CM is the detector of a camera of the smartphone, and the light source SL is a flash lamp of the smartphone. Thus, the determination of the authenticity of the product P is obtained very simply by placing the region R of the product P in the field of view of the camera, then triggering the flash of the camera for an illumination duration adapted according to the compounds CP to generate the excitation beam FE in order to produce phosphorescence radiation RP. The processing unit UT acquires and digitizes the first image I1 taken at a distance adapted to allow the camera's autofocus to produce a good quality image and then implements steps B to D (or possibly only steps B and C).

[0081] The flash activation and photo taking are controlled by the smartphone's processing unit, if necessary via a dedicated application. In this embodiment, the advantage provided by the method of the invention is notable. It allows simple and reliable authentication via a smartphone which is an object commonly available to the general public.

[0082] Preferably, the processing unit UT is configured to turn off the flash after a predetermined illumination duration and to acquire the first image between 0.1 and 10 seconds after the generation of the excitation beam FE. Indeed, as mentioned previously, the phosphorescence has a typical lifetime of the order of a millisecond or more. Preferably, the CP compounds are chosen so as to generate phosphorescence radiation having a lifetime greater than one second so as to facilitate the acquisition of the first image.

[0083] Furthermore, when the acquisition of the first image is carried out with the flash lamp on, it is preferable that, for step B, the processor implements a specific processing making it possible to remove the color component due to the flash taking into account the prior knowledge of the flash illumination. This processing is known to those skilled in the art moreover and makes it possible to obtain a first measurement not biased by the flash.

[0084] Preferably, the processing unit is configured to display on the smartphone screen a graphic message representative of the authenticity of the product P following step D. Thus, the user is informed of the result of the authentication.

[0085] Figure 3 schematically illustrates the steps of a method according to an embodiment of the authentication method of Figure 1B. In this embodiment, the system SA is a smartphone and the steps are implemented directly by the processing unit UT of the smartphone. Preferably, the method of Figure 3 is implemented by means of a dedicated application comprising code instructions for carrying out the steps of the method.

[0086] The authentication method of figure 3 comprises a step implemented prior to step A, noted step 00, and consisting of: - acquiring a second image I2 of the product, then - determining in the second image I2 a region R of the product comprising the phosphorescent compounds CP.

[0087] For example, region R is determined by image processing such as edge detection.

[0088] Once it is determined that the region R is present in the image I2, the processing unit is configured to implement a step 01 before step A consisting of turning on the flash lamp of the smartphone so as to generate the excitation beam FE.

[0089] Following step 01, the processing unit UT is configured to implement the previously detailed steps A to D of the method of FIG. 1B so that the first image I1 is acquired in step B so as to acquire the region R identified in step 00. Preferably, the first measurement of step B is carried out by an average of a colorimetric measurement of pixels of the first image detecting the region R.

[0090] Preferably, the method of Figure 3 comprises a step 02 implemented after step 01 and before step A consisting of turning off the flash lamp. Indeed, if the flash lamp remains on for the acquisition of the first image I1 it is likely to modify the first measurement of the color of the phosphorescence radiation RP. It would then be possible to induce a difference in color compared to the reference data which would not be due to the compounds CP but solely to the illumination.

[0091] Preferably, the compounds are formulated in a matrix fixed on the product P (for example in the form of a patch or a strip) so as to define a region R such that this region R has a different color before and after excitation by the excitation beam FE. By "a color different from the product", it is meant here that the region R comprising the compounds CP before and after excitation by the excitation beam has a color difference greater than or equal to 5, preferably greater than or equal to 10. Thus, by a colorimetric comparison of the R region in the first and second images, it is possible to verify that the RP phosphorescence radiation is actually detected in the first image.

[0092] Figure 4 illustrates an example of the second image I2 (left) and the first image I1 (right) according to an embodiment in which the labeling of the product P by the compounds CP is carried out in the form of a patch defining a region R.

[0093] As can be seen in Figure 4, the region R is identified from the second image I2. As a non-limiting example, the coordinates in the RGB colorimetric system of the color of the region R before illumination by the excitation beam FE are R=0.82, G=0.85, B=0.73. These coordinates are obtained by averaging the color of the pixels detecting the region R in the second image after step 00. Following the illumination of the patch by the excitation beam FE (step 01), the processing unit acquires the first image I1 (step A) and performs the colorimetric analysis of this first image to determine the first measurement (step B). As a non-limiting example, the excitation beam FE is generated by the flash lamp of a smartphone (step 01) which is turned off (step 02) just before the acquisition of the first image.The coordinates in the RGB color system of the color of the R region when it emits the RP phosphorescence radiation are R=0.56, G=0.85, B=0.64. These coordinates are obtained by averaging the color of the pixels detecting the R region in the first image.

[0094] The color of the R region in the first and second images is different, which makes it possible to verify that the phosphorescence radiation RP is actually detected in the first image I1. By implementing steps C and D, the authenticity of the product P can then be determined.

[0095] As mentioned above, the authentication method according to the invention can be implemented using hardware and / or software elements. The authentication method can in particular be implemented using a computer program product, this computer program comprising code instructions for carrying out the steps of the control method. It is recorded on a computer-readable medium. The medium can be electronic, magnetic, optical, electromagnetic or be an infrared type diffusion medium. Such media are, for example, semiconductor memories (Random Access Memory RAM, Read-Only Memory ROM), tapes, magnetic or optical disks or disks (Compact Disk – Read Only Memory (CD-ROM), Compact Disk – Read / Write (CD-R / W) and DVD).

[0096] As an example of a hardware architecture suitable for implementing the invention, a device may comprise a communication bus to which a central processing unit or microprocessor (CPU, acronym for "Central Processing Unit" in English) is connected, which processor may be "multi-core" or "many-core"; a read-only memory (ROM, acronym for "Read On Memory" in English) which may comprise the programs necessary for implementing the invention; a random access memory or cache memory (RAM, acronym for "Random Access Memory" in English) comprising registers suitable for recording variables and parameters created and modified during the execution of the aforementioned programs; and a communication interface or I / O (I / O acronym for "Input / output" in English) suitable for transmitting and receiving data.In the case where the invention is implemented on a reprogrammable computing machine (for example an FPGA circuit), the corresponding program (i.e. the sequence of instructions) may be stored in or on a removable storage medium (for example an SD card, or a mass storage such as a hard disk e.g. an SSD) or non-removable, volatile or non-volatile, this storage medium being partially or totally readable by a computer or a processor. The reference to a computer program which, when executed, performs any of the functions described above, is not limited to an application program running on a single host computer.Rather, the terms computer program and software are used herein in a general sense to refer to any type of computer code (e.g., application software, firmware, microcode, or any other form of computer instruction, such as web services or SOA or via APIs) that can be used to program one or more processors to implement aspects of the techniques described herein. The computing means or resources may in particular be distributed ("Cloud computing"), possibly with or according to technologies. peer-to-peer and / or virtualization. The software code may be executed on any suitable processor (e.g., a microprocessor) or processor core or a set of processors, whether provided in a single computing device or distributed among multiple computing devices (e.g., as may be accessible in the device environment). Security technologies (cryptoprocessors, possibly biometric authentication, encryption, smart card, etc.) may be used.

Claims

Claims 1. Method for authenticating a product (P) using phosphorescent compounds (CP), said method comprising the following steps: A. inducing phosphorescence radiation (RP) by an excitation beam (FE) illuminating phosphorescent compounds (CP) of authentic copies of said product (P) B. Carrying out an analysis so as to determine a first measurement of the phosphorescence radiation (RP) C. Comparing the first measurement and a so-called reference data characterized in that the authentication is an authentication by colorimetry, the method comprising an acquisition of a first image (I1), the analysis being a colorimetric analysis of said first image (I1), the first measurement being a measurement of a color.

2. Method according to claim 1, comprising a subsequent step D consisting of determining an authenticity of the product as a function of said step C of comparison between the first measurement and the reference data. 3.The method of claim 2, wherein the first measurement is a first triplet in a first color space and the reference data is a second triplet in said first color space, said step C consisting of calculating a color difference between the first and second triplet or a color difference between the first and second triplet relative to the second triplet.

4. The method of claim 3, wherein step D consists of determining that the product is authentic when the color difference relative to the second triplet is less than or equal to 5%.

5. The method of claim 3 or 4, wherein the phosphorescent compounds are incorporated into said product in a solid, liquid, gel, polymer, or biocompatible matrix, the method comprising a subsequent step E, implemented only when it is determined in step D that the product is not authentic, consisting of calculating a. concentration of phosphorescent compounds from said color difference and a correspondence table or function determining a concentration of phosphorescent compounds in said product as a function of the color difference, said correspondence table being determined prior to implementing the method. 6.Method according to any one of the preceding claims implemented by a processing unit of a smartphone, comprising a step 00, implemented prior to step A and consisting of acquiring a second image (I2) of the product then determining in the second image a region (R) of said product comprising the phosphorescent compounds, and comprising a step 01, implemented prior to step A, consisting of turning on a flash lamp of the smartphone so as to generate the excitation beam FE, the first image (I1) then being acquired in step B so as to acquire said region, and said first measurement of step B being carried out by an average of a colorimetric measurement of pixels of the first image detecting said region. 7.Computer program product, said computer program comprising code instructions for carrying out the steps of the method according to any one of claims 1 to 6, when said program is executed on a computer.

8. Device (DA) for colorimetric authentication of a predetermined product (P) comprising predetermined phosphorescent compounds (CP), the device comprising a matrix sensor (CM) and a processing unit (UT) configured to implement the following steps: A. acquiring, via the matrix sensor, a first image (I1) of phosphorescence radiation (RP) induced by an excitation beam (FE) illuminating phosphorescent compounds of said product. B. performing a colorimetric analysis of the first image (I1) so as to determine a first measurement of a color of the phosphorescence radiation C. comparing the first measurement of the color of the phosphorescence radiation and a so-called reference data item stored in the processing unit and determined as a function of the phosphorescent compounds and a color of said product.

9. Device according to the preceding claim, in which the processing unit is configured to implement a subsequent step D consisting of determining an authenticity of the product as a function of said step C of comparison between the first measurement and the reference data item. 10.Device according to the preceding claim, wherein the device is a smartphone comprising a screen, said matrix sensor being the matrix sensor of a camera of the smartphone, the processing unit being configured to display on the screen a graphic message representative of the authenticity of the product following step D.

11. System (SA) for colorimetric authentication of a predetermined product comprising predetermined phosphorescent compounds, said system comprising a device (DA) according to one of claims 8 to 10 and comprising a light source (SL) adapted to generate said excitation beam (FE) illuminating the phosphorescent compounds of said product so as to induce phosphorescence radiation (RP).

12. System according to the preceding claim, wherein the light source is adapted so that the excitation beam (FE) has wavelengths in a spectral range from 200 nm to 900 nm.

13. System according to claim 11 or 13, wherein the processing unit is configured to acquire the first image between 0.1 and 10 seconds after the generation of the excitation beam (FE).

14. System according to any one of claims 11 to 13, wherein the system is a smartphone, said matrix sensor being the matrix sensor. of a smartphone camera, and the light source being a smartphone flash lamp.

Images