FR3151119A1 - Method for authenticating a predetermined product and Device for authenticating a predetermined product - Google Patents

Abstract

Method for authenticating a predetermined product comprising predetermined phosphorescent compounds, said method comprising the following steps: Acquiring a first image (I1) of phosphorescence radiation (RP) induced by an excitation beam (FE) illuminating phosphorescent compounds of said product Carrying out a colorimetric analysis of the first image (I1) so as to determine a first measurement of a color of the phosphorescence radiation 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. [Fig.1A]

Description

Method for authenticating a predetermined product and Device for authenticating a predetermined product

The present invention relates to the field of product authentication and more particularly to product authentication by colorimetric method.

In many applications, it is crucial to identify fraudulent reproduction. Among the areas most prone to these counterfeits are the luxury industry, the pharmaceutical industry, the production of certified documents and the alcohol industry.

In order to detect imitations, fluorescent inks known as "security" are increasingly used. Their presence makes it possible to prove the authenticity of a product. Products marked by inks can be, for example, banknotes, identity cards, official documents (stamps, driving licenses, etc.).

Documents WO 97/10307 and FR 2 909 095 describe such security inks. These inks are colorless, invisible to the naked eye, and visible only under light excitation (under ultraviolet light for example).

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).

US Patent 5,135,569 describes an ink visible to the naked eye and fluorescent for marking porous supports. The ink is formed from a black pigment, a fluorophore and a solvent. The solvent is used to impregnate the porous substrate 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 remove at least partially the upper layer of black pigment to check whether the marking includes an underlying fluorescent layer. More complex inks can contain two types of dyes, the first being fluorescent and the second having an absorption band covering the emission band of the first dye, or being located at higher wavelengths, so as to give a dark coloring to the ink. The ink includes 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 wide band of fluorescence, due to the first dye, and a thin band of fluorescence 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.

Application FR3025206A1 describes an easy-to-produce luminous ink composition for marking different substrates, the marking having to be very bright, both 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.

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.

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.

For this purpose, an object of the invention is a method of colorimetric authentication of a predetermined product comprising predetermined phosphorescent compounds, said method comprising the following steps:

A- Acquire a first image of phosphorescence radiation induced by an excitation beam illuminating phosphorescent compounds of said product

B- Carry out a colorimetric analysis of the first image in order to determine a first measurement of a color of the phosphorescence radiation

C- Compare the first measurement of the color of the phosphorescence radiation and a so-called reference data determined prior to the implementation of the process based on the phosphorescent compounds and a color of said product.

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

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%.

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. and a correspondence table or 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 method.

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 lighting 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.

Another subject of the invention is a computer program product comprising code instructions for carrying out the steps of the method of the invention, when said program is executed on a computer.

Another object 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- acquire, via the matrix sensor, a first image of phosphorescence radiation induced by an excitation beam illuminating phosphorescent compounds of said product

B- carry out a colorimetric analysis of the first image so as to determine a first measurement of a color of the phosphorescence radiation

C- compare the first measurement of the color of the phosphorescence radiation and a so-called reference data stored in the processing unit and determined according to the phosphorescent compounds and a color of said product.

According to one embodiment, the processing unit is configured to implement a subsequent step D consisting in 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.

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.

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

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 generation of the excitation beam.

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.

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:

, a schematic view of a system according to the invention for colorimetric authentication of a predetermined product,

, the steps of the colorimetric authentication method according to the invention,

, the steps of the method according to a variant of the preferred embodiment,

the steps of a method according to an embodiment of the method of authenticating the ,

, 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,

In the figures, unless otherwise indicated, the elements are not to scale and identical references designate identical elements.

There 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.

There 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.

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 quickly (lifetime typically ranging from picoseconds to a few nanoseconds). This speed 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 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 passes from the S1 state to another higher spin state which 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.

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. As a 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.

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.

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.

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 the 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.

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 the .

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.

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 so as 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.

This colorimetric analysis step B is a step known per se 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.

It is noted that, in order to perform this colorimetric analysis, it is essential that the matrix sensor CM is a broadband sensor, or comprises a plurality of monospectral 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 RP phosphorescence radiation and spectral width greater than or equal to the half-maximum width of the phosphorescence emission of CP compounds.

Preferably, step B comprises a first sub-step consisting in 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 contour 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.

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.

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 phosphorescence radiation RP taking into account the color of the product P and the phosphorescent emission of the compound CP and the illumination used. Indeed, in a manner known per se, a measurement of the color depends on the illumination and the 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 lighting and appear to be different colors with lighting of a different spectral distribution.

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.

As an example, Table 1 below presents a series of ten reference data (measurements “with flash”) which are color measurements in the Lch space of a cosmetic cream comprising a concentration C1 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 (measurements “without flash”).

Table 1: C1 concentration series L C1 without flash c C1 without flash h C1 without flash L C1 with flash c C1 with flash h C1 with 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

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 1 can be compared to 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 illumination by flash lamp.

Table 2: C0 concentration series L C0 without flash c C0 without flash h C0 without flash L C0 with flash c C0 with flash h C0 with 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

By averaging to reduce the variability inherent in these measurements, we obtain average values for the data taken with flash lamp which are .

This step C is preferably - 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, localized (removable storage medium or not) or non-localized (for example the “cloud”) and the comparison step is carried out directly by the processing unit.

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.

Alternatively, according to another embodiment, the reference data is stored on a physical medium. As a 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.

Finally, the process of the 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.

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

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.

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 second triplet or a difference between the first and second triplet relative to the second triplet ΔE/E ₂ . Step D then consists of determining that the predetermined product is authentic when the color difference ΔE/E ₂ 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.

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, in 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.

For example, the first measurement and the reference data are described in the two-dimensional space called CIE 1976. This space comes 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:

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

and with

Here, the triplet (u'w, v'w, Yw) corresponds to the colorimetric coordinates of white. And are the first and second triplet respectively. More precisely, And are the clarity of the first measure and the reference data respectively. And are the parameters characterizing the chrominance associated with the first measurement and the reference data respectively.

The color difference relative to the second triplet is then: .

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.

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 the , authentication is particularly suitable for implementation on a smartphone via a dedicated application.

It is however 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.

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 is aware of the predetermined threshold.

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 CP compounds are printed or formulated in the form of a patch or a strip.

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

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. .

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.

Alternatively, the table or correspondence function is digitally readable by the processing unit UT.

After implementing the previously detailed steps A to D, the method of Figure 2 comprises 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 matching function.

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.

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). It is therefore possible to determine that the product P has been diluted by a factor C1/C2.

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.

Table 3: C2 concentration series L C2 without flash c C2 without flash h C2 without flash L C2 with flash c C2 with flash h C2 with 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

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 the C1 concentration and the triplet associated with the C2 concentration. Thus, we can associate this color difference value with a dilution of a factor C2/C1=2 for this specific case.

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 by 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 autofocus of the camera to produce a good quality image and then implements steps B to D (or possibly only steps B and C).

The flash ignition and the taking of photos are controlled by the processing unit of the smartphone, if necessary by means of 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.

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 FE excitation beam. Indeed, as mentioned above, 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.

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 allowing the removal of 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 allows a first measurement to be obtained that is not biased by the flash.

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

There schematically illustrates the steps of a method according to an embodiment of the method of authenticating the . 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 the is implemented through a dedicated application including code instructions to perform the process steps.

• acquérir une deuxième image I2 du produit, puis
• déterminer dans la deuxième image I2 une région R du produit comprenant les composés phosphorescents CP.

The authentication process of the includes a step implemented prior to step A, noted step 00, and consisting of:

• acquire a second I2 image of the product, then
• determine in the second image I2 a region R of the product comprising the phosphorescent compounds CP.

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

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.

Following step 01, the processing unit UT is configured to implement the previously detailed steps A to D of the method of the such 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.

Preferably, the method of FIG. 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 color difference compared to the reference data which would not be due to the CP compounds but only to the illumination.

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 difference in color 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.

There 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.

As observable on the , 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 an average of 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.

The color of the R region in the first and second images is different, which allows us to verify that the phosphorescence radiation RP is actually detected in the first image I1. By implementing steps C and D, we can then determine the authenticity of the product P.

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 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).

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 OnIy 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 (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 executing 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 peer-to-peer and/or virtualization technologies. 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 several computing devices (e.g. as possibly accessible in the environment of the device). Security technologies (crypto-processors, possibly biometric authentication, encryption, smart card, etc.) may be used.

Claims (14)

Method for colorimetric authentication of a predetermined product (P) comprising predetermined phosphorescent compounds (CP), said method comprising the following steps:

1. Acquire a first image (I1) of a phosphorescence radiation (RP) induced by an excitation beam (FE) illuminating phosphorescent compounds (CP) of said product (P)
2. Perform a colorimetric analysis of the first image (I1) in order to determine a first measurement of a color of the phosphorescence radiation (RP)
3. Compare the first measurement of the color of the phosphorescence radiation (Rp) and a so-called reference data determined prior to the implementation of the process according to the phosphorescent compounds and a color of said product.

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. 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 comprising 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. The method of claim 3, wherein step D comprises determining that the product is authentic when the color difference relative to the second triplet is less than or equal to 5%. A method according to 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 in calculating a concentration of the phosphorescent compounds from said color difference. and a correspondence table or 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 method. 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 lighting 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. 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. Authentication device (DA) by colorimetry 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:

1. 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
2. perform a colorimetric analysis of the first image (I1) so as to determine a first measurement of a color of the phosphorescence radiation
3. compare the first measurement of the color of the phosphorescence radiation and a so-called reference data stored in the processing unit and determined according to the phosphorescent compounds and a color of said product.

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. Device according to the preceding claim, in which 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. 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). System according to the preceding claim, in which the light source is adapted so that the excitation beam (FE) has wavelengths in a spectral range from 200 nm to 900 nm. The system of claim 11 or 13, wherein the processing unit is configured to acquire the first image between 0.1 and 10 seconds after generation of the excitation beam (FE). The system of any one of claims 11 to 13, wherein 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.