WO2020128345A1

WO2020128345A1 - Document equipped with lenses for detecting fraud

Info

Publication number: WO2020128345A1
Application number: PCT/FR2019/053180
Authority: WO
Inventors: Benoit Berthe; Alban Feraud
Original assignee: Idemia France
Priority date: 2018-12-20
Filing date: 2019-12-19
Publication date: 2020-06-25
Also published as: FR3090472B1; EP3898249A1; FR3090472A1; EP3898249B1

Abstract

The invention relates to a document (DC1) comprising a stack (14) of layers including a top layer (LY1) and a bottom layer (LY3), and an internal layer (LY2) interposed between the top and bottom layers, the internal layer (LY2) being transparent or translucent so as to form a waveguide for guiding light (LG1) belonging to a first wavelength spectrum (SRI), the internal layer forming together with the top layer and the bottom layer an edge face (16) that delineates an outline of the stack, the document further comprising an array (20) of lenses (18) formed on the edge face (16) of the stack (14), the lenses being positioned along the edge face so as to make light (LG1) belonging to the first wavelength spectrum (SRI) converge or diverge when it propagates through the internal layer (LY2) so as to emerge from the document via the edge face (16), thus causing there to appear, on the edge face, a series of colour regions of at least two separate colours.

Description

Title of the invention: Document equipped with lenses for fraud detection

Technical area

The invention is in the field of document security and relates more particularly to anti-fraud mechanisms designed to reveal fraudulent manipulations carried out on documents, in particular manipulations aimed at separating layers or elements of a document for the purposes of, for example, illegal forgery or alteration.

Prior art

Many documents used frequently in everyday life are subject, because of their value or their more or less sensitive nature, to the risk of fraudulent manipulation. Identity documents such as identity cards, passports, badges, driver's licenses, bank cards, loyalty cards and others are therefore frequently the subject of unlawful copies, alterations or falsifications. Likewise, risks of fraud weigh on banknotes, fiduciary or notarial documents, certificates and all other documents of certain value.

Also, various anti-fraud devices have been developed over time to best secure such documents, the complexity of these devices increasing to deal with the threat of fraud.

Fraudulent manipulation consists in separating the constituent layers of a document in order to falsify it. Another fraudulent manipulation consists of sanding one or more documents so as to eliminate the personalized elements and recovering security devices to recompose a document and repersonalize it. Such techniques make it possible to falsify various documents, such as passports or cards for example. Once the document's constituent layers are separated or recovered after sanding, the fraudster can carry out various illegal manipulations such as replacing at least one of the original layers with a falsified layer or even manipulating an electronic chip or any other device contained in the document.

To avoid any fraudulent delamination of a document, it is known to use adhesives having good mechanical strength to securely fix the layers of the document together. However, such adhesives do not always satisfactorily prevent such adulteration by delamination of the layers.

To fight against this type of fraud, a known solution consists in using polycarbonate layers and laminating them so as to form only one inseparable block. However, this block remains vulnerable to sanding attacks otherwise known as abrasion attacks.

Document W02008 / 110892 A2 discloses a technique consisting in marking inscriptions on the edge of a document in order to prevent a fraudster from separating the layers of the document and from reforming a credible assembly. However, the means available to fraudsters are sometimes very important and such registrations do not always make it possible to detect fraudulent delamination. For example, we can recover layers containing the security elements, replace the personalized laser layers, sand the edge of the new document and then proceed to personalize the edge again with a simple marking laser, which is now easily accessible.

[0008] There is therefore a need today for a solution which makes it possible to effectively protect documents against fraudulent manipulation, notably consisting in delaminating layers of the document, reassembling them with certain blank layers and re-personalizing them with a marking laser. . In particular, it is necessary to reliably detect any manipulation resulting from an at least partial delamination of the constituent layers of a document, such as one of those mentioned above for example.

Statement of the invention

To this end, the present invention relates to a document comprising:

a stack of layers comprising at least: an upper layer, a lower layer and an inner layer interposed between the upper layer and the lower layer, the inner layer being transparent or translucent so as to form a waveguide for guiding light at a first spectrum of wavelengths through the layer internal,

the internal layer collectively forming with the upper layer and the lower layer a wafer which delimits an outline of the stack; and

an array of lenses formed on at least part of the wafer

stacking, said lenses being positioned along the edge to converge or diverge light at the first spectrum of wavelengths when it propagates in the inner layer until it emerges outside the document through said edge , so as to show on the edge a series of color zones of at least two distinct colors.

The invention makes it possible to secure the document by means of a lens arrangement intended to detect when the constituent layers of this document are separated, so as to prevent fraudulent manipulation.

According to a particular embodiment, the upper layer and the lower layer are configured to optically confine light to a first spectrum of wavelengths in the inner layer.

According to a particular embodiment, the stack is such that:

- the upper layer and the lower layer are opaque; or

- The upper layer and the lower layer have a refractive index less than or equal to that of the inner layer.

According to a particular embodiment, the lens array constitutes a safety device covering at least part of the wafer to visually testify to the integrity of the stack as long as said layers are not separated from each other .

According to a particular embodiment, the lenses are each positioned to generate, in a corresponding zone of the wafer, an overall color from the colorimetric contribution of at least one of the upper layer, the inner layer and the lower layer, said color being dependent on the direction of observation. According to a particular embodiment, the lens array is configured so as to cause a change in color which can be seen in the areas of the wafer which are covered by the lenses by varying the direction of observation with respect to of said lenses.

According to a particular embodiment, the series of color zones form an alternation of at least two distinct colors on the edge, regardless of the direction of observation.

According to a particular embodiment, the upper and lower layers are reflective, white for example, so as to confine the light to the first spectrum of wavelengths in the inner layer.

According to a particular embodiment, each lens of the lens array is positioned on the wafer so as to converge incident light received on the wafer from outside the document, essentially on the section of one among the lower layer, the upper layer and the inner layer.

According to a particular embodiment, the lenses are formed:

- by a laser ablation technique on the edge of the stack; or

- By a laser melting and discharge technique of the material of the stack so as to form the lenses on the edge of said stack.

According to a particular embodiment, the lower layer or the upper layer comprises an opening through which the internal layer is capable of receiving excitation light at a second spectrum of wavelengths different from the first spectrum. wavelengths, the inner layer comprising an additive, a dye for example, which emits light at the first spectrum of wavelengths when said dye is exposed to excitation light, UV light for example.

According to a particular embodiment, the stack comprises an intrinsic light source configured to emit in the internal layer an excitation light with a second spectrum of wavelengths different from the first spectrum of wavelengths, the internal layer comprising an additive (a coloring agent for example) which emits light at the first spectrum of wavelengths when said dye is exposed to excitation light. According to a particular embodiment, the document comprises an intrinsic light source configured to emit light at the first spectrum of wavelengths in the internal layer.

According to a particular embodiment, the document comprises in or on the stack at least one LED serving as an intrinsic light source for emitting light at the first spectrum of wavelengths in the inner layer,

the document further comprising an RF antenna in or on said stack for electrically supplying said at least one LED by means of an induced current under excitation of an electromagnetic field.

According to a particular embodiment, a series of symbols is formed on an upper face of the stack or on a lower face of

the stack, near the edge,

the lens array comprising at least one said lens on the edge in alignment with each symbol so as to cause a visual pattern associated with each symbol to appear from light at the first wavelength spectrum when it propagates in the internal layer until it emerges outside the document through said edge.

According to a particular embodiment, each visual pattern generated by the lens array conforms to a correspondence code which associates a visual pattern with at least one respective physical characteristic of a symbol or with a respective type of symbol.

According to a particular embodiment, the lenses of the lens array are arranged in notches formed on the edge of the stack, the thickness of each lens being less than the depth of the respective notch so as to protect mechanically said lenses.

Brief description of the drawings

Other characteristics and advantages of the present invention will emerge from the description given below, with reference to the accompanying drawings which illustrate examples of embodiment devoid of any limiting nature. In the figures:

[Fig. 1] Figure 1 is a perspective view of a document according to a particular embodiment of the invention; [Fig. 2] Figure 2 is a sectional view of the document shown in Figure 1, according to a particular embodiment of the invention;

[Fig. 3] Figure 3 is a sectional view of the document shown in Figure 1, according to a particular embodiment of the invention;

[Fig. 4A-4B-4C] FIGS. 4A, 4B and 4C are detailed views of the section of a document conforming to a particular embodiment of the invention;

[Fig. 5] Figure 5 is a perspective view of a document according to a particular embodiment of the invention;

[Fig. 6] Figure 6 is a sectional view of the document shown in Figure 5, according to a particular embodiment;

[Fig. 7] Figure 7 is a perspective view of a document according to a particular embodiment of the invention;

[Fig. 8A-8B-8C] Figures 8A, 8B and 8C are views of a document according to a particular embodiment of the invention;

[Fig. 9] Figure 9 is a perspective view of a document according to a particular embodiment of the invention; and

[Fig. 10] FIG. 10 schematically represents, in the form of a diagram, the steps of a process for manufacturing a document, according to a particular embodiment of the invention.

Description of the embodiments

The present invention proposes to secure documents by equipping them with a lens-based device intended in particular to detect when the constituent layers of these documents have been separated, so as to prevent fraudulent manipulation.

To do this, the invention proposes in particular to have a network of lenses on the edge of a document comprising a transparent or translucent layer interposed between an upper layer and a lower layer. The lenses are arranged on all or part of the wafer so that a light which propagates in the transparent or translucent layer emerges more or less depending on the position of the lenses, outside the document through the lenses, thus producing a visual (or optical) effect on the edge which is difficult for a forger to reproduce. The visual effects generated on the edge of the document may in particular comprise a series of zones of two or more distinct colors, according to any suitable pattern. The separation of at least two layers of the document then necessarily causes the alteration of the anti-fraud device because at least part of the lenses will be damaged by the separation of the layers. After delamination, it is therefore technically difficult to reproduce a stack of layers with the same visual effect as that produced by the anti-fraud device of the invention, in particular since it is difficult to reproduce the same lenticular network as that of the invention .

According to a particular embodiment, the invention thus relates to a stack of layers comprising at least:

- an upper layer and a lower layer;

an internal layer interposed between the upper layer and the lower layer, the internal layer being transparent or translucent so as to form a waveguide for guiding light at a first spectrum of wavelengths through the internal layer,

- the internal layer collectively forming with the upper layer and the lower layer a slice which delimits an outline of the stack; and

- an array of lenses formed on at least part of the edge of the stack, the lenses being positioned along the edge to converge or diverge light at the first spectrum of wavelengths when it propagates in the internal layer until emerging outside the document by said slice, so as to make the slice appear a series of color zones of at least two distinct colors.

The upper and lower layers are configured to optically confine light to the first spectrum of wavelengths in the inner layer. Thus, according to a particular example, the upper layer and the lower layer are opaque. According to another example, the upper layer and the lower layer have a refractive index less than or equal to that of the internal layer. The invention also relates to a corresponding manufacturing process for manufacturing the document of the invention.

Other aspects and advantages of the present invention will emerge from the exemplary embodiments described below with reference to the drawings mentioned above.

In the present description, examples of implementation of the invention are described in the context of an identity card or a passport. Note however that other embodiments are possible. The invention does not apply exclusively to cards or passports but more generally applies to any document whose edge can be secured in accordance with the principle of the invention.

Thus, in the present description, the term “document” generally designates all types of document comprising constituent layers together defining two opposite faces and a wafer (or edge). It can be, for example, an identity document or a security document.

A document within the meaning of the invention can be a card, such as an identity card, a driving license, a smart card, a bank card, a magnetic card, a loyalty card, a card access, badge, etc. A document within the meaning of the invention may also take the form of a sheet or of a booklet comprising a plurality of sheets. It can be for example a more or less flexible ticket, a passport or any other appropriate document.

Unless otherwise indicated, the elements common or similar to several figures bear the same reference signs and have identical or similar characteristics, so that these common elements are generally not described again for the sake of simplicity.

Figure 1 is a perspective view of a DC1 document according to a particular embodiment of the invention.

Consider document DC1 which takes the form of a card, such as a standard card (without a chip) or a smart card. According to a particular example, it is a bank card, such as an ISO / IEC 7816 or ISO / IEC 7810 compliant card for example. It can also be a page (or sheet) or the cover of a booklet, such as a passport for example. As already indicated, other example documents within the meaning of the invention are however possible.

As shown in FIG. 1, the document DC1 comprises a stack 14 of layers comprising at least:

- an upper layer LY1 and a lower layer LY3; and

- an internal layer LY2 interposed between the upper layer LY1 and the lower layer LY3.

The internal layer LY2 collectively forms with the upper layer LY1 and the lower layer LY3 a wafer (or edge) 16 which delimits an outline of the stack 14. Thus, the stack 14 forms two external faces (the upper face S1 and the lower face S2), opposite one another, as well as the edge 18 on the periphery of these faces S1 and S2.

The internal layer LY2 is transparent or translucent so as to form a waveguide for guiding a light LG1 to a first spectrum of wavelengths SP1 through the internal layer LY1. In other words, the upper layer LY1 and the lower layer LY3 confine the light LG1 in the inner layer LY2 which serves as a waveguide to conduct this light in the first wave spectrum SP1. The internal layer LG1 thus makes it possible to guide this light LG1 so that it propagates in the internal layer LY1 until it emerges via at least part of the wafer 18.

To do this, the upper layer LY1 and the lower layer LY3 are configured to optically confine the light LG1 to the first spectrum of wavelengths SP1 inside the inner layer LY2. To do this, the layers LY1 and LY3 are therefore of an optical nature different from that of the internal layer LY2. According to a first particular example, the upper layer LY1 and the lower layer LY3 are opaque. According to a second particular example, the upper layer LY1 and the lower layer LY3 have a refractive index less than or equal to that of the internal layer LY2.

In a particular example, the layers LY1 and LY3 are reflective, white or metallic, or have a lower refractive index (or possibly equal) than that of the inner layer LY2, so as to confine the light LG1 to the inside the inner layer LY2. In a particular case, the layers LY1, LY2 and LY3 can be made of plastic, polycarbonate for example, other materials being however possible, such as for example polyurethane.

By first spectrum of wavelength SP1, we mean a particular range of wavelengths. This range can be more or less narrow or concentrated essentially on one wavelength, depending on the case considered. This first spectrum of wavelength SP1 is for example included in (or corresponds to) the visible spectrum, other embodiments being however possible.

As explained below, various light sources can be used to project light LG1 to the first spectrum of wavelengths SP1 into the inner layer LY2 of the stack 14. Specific examples are described later.

In addition, document DC1 comprises an array 20 of lenses 18 formed on at least part of the edge 16 of the stack 14. These lenses 18 are positioned along the edge 16 to make the light converge or diverge LG1 (at the first spectrum of wavelengths SP1) when this light propagates in the internal layer LY2 until it emerges outside the document DC1 by section 16, so as to cause an effect to appear on section 16 ( or pattern) predefined visual which depends on the relative position of the lenses vis-à-vis the LY2 layer.

In the example considered here, the array 20 of lenses 18 is arranged to produce, by convergence or divergence of the light LG1 exiting from the internal layer LY2 through the wafer 16, a series of color zones of at least two distinct colors, as described in more detail later.

The lens array 20 constitutes a safety device covering at least part of the wafer 16 to visually testify to the integrity of the stack 14 as long as said layers are not separated from each other. In other words, the network 20 of lenses forms an anti-fraud device making it possible to detect whether at least two of the layers LY1, LY2 and LY3 of the document DC1 are separated after the production of the document DC1. Delamination (or separation) of at least two of the LY1 layers - LY3 at the level of wafer 16 leads in fact to an at least partial alteration or rupture of the network of lenses 20 which results in a modification of the visual (or optical) effect produced by the propagation of the light LG1 emerging through section 16. Such a modification of the visual effect thus indicates manipulation or alteration of the document DC1 by delamination.

Figures 2 and 3 are sectional views at two different positions of the stack 16 of document DC1.

The lenses 18 can have various shapes, dimensions and gradients of refractive index depending on the use case. As shown in the figures, we consider below cases where each lens 18 of the array 20 has a semi-cylindrical shape, although other shapes are possible. Alternatively, the lenses 18 may have a parabolic shape, a sinus shape, etc. Each lens 18 may have a density gradient causing a gradient of refractive index inside the lens and leading to the light converging or diverging.

As shown in the figures, we consider cases where the lenses 18 are convergent with respect to an incident light external to the document DC1. Thus, each lens 18 is positioned on the edge 16 so as to cause incident light received on the edge 16 to converge from outside the document. As shown in FIGS. 2 and 3, this means that each lens 18 causes the light LG1 propagating in the internal layer LY2 to diverge until it emerges outside the document DC1 through the lenses 18 located along the edge 16. As illustrated below, the visual patterns generated by the lenses are a function in particular of the relative position of the lenses with respect to the internal layer LY2.

Generally, each lens 18 is arranged on the edge 16 so as to cover the thickness of at least one of the layers LY1-LY3 of the stack 14.

More particularly, it is assumed here that each lens 18 converges incident light (received from outside the document DC1) essentially on the edge (the section, or the thickness) of only one of the layer lower LY3, the upper layer LY1 and the inner layer LY2. As shown in Figures 1-3, each lens 18 of the array 20 is positioned essentially opposite the thickness of one of the layers LY1, LY2 and LY3.

In a particular example, the useful surface on which each lens 18 converges incident light received from outside the document DC1 is located at least 90% on the edge (section) of only one of the three layers LY1, LY2 and LY3.

For example, Figure 2 shows the lenses 18a and 18b of the array 20 which are positioned in an area Z1 of the document DC1 (Figure 1), in alignment with the edge of the lower layer LY3 and the layer higher LY1, respectively. In this example, the lenses 18a and 18b are thus positioned adjacent to each other, according to the thickness of the wafer 16 (direction x).

Similarly, by way of example, FIG. 3 represents the lens 18c which is positioned in an area Z2 of the document DC1 (FIG. 1), in alignment with the edge of the inner layer LY2.

As shown in Figures 1-3, the light LG1 in the first spectrum SP1 is reflected on the internal faces of the layers LY1 and LY3 so as to remain confined in the internal layer LG2 acting as transparent or translucent waveguide . The light LG1 thus emerges on the edge 16 and is guided by the lenses 18 towards the outside of the document DC1. Depending on the configuration of the lenses (position, shape, etc.) which is chosen, the light LG1 thus propagates in various ways producing a particular visual effect (or pattern) that an observer or control system can visualize, this visual effect being depending on the direction of observation adopted with respect to the array 20 of lenses 18.

According to a particular example, the layers LY1, LY2 and LY3 of the stack 14 have colors C1, C2 and C3 respectively. These colors C1 -C3 are more or less viewable from outside the document DC1 when the light LG1 emerges through the array 20 towards an observer, as explained below.

It is understood that the layers LY1, LY2 and LY3 are here essentially monochrome although other more complex examples are possible. By for the sake of simplicity, it is also assumed that the colors C1 and C3 are identical, although other examples of implementation are possible.

As shown in the example of Figures 1-3, the lenses 18 are each positioned to generate, in a corresponding area of the wafer 16, an overall color from the colorimetric contribution of at least one of the upper layer LY1, the inner layer LY2 and the lower layer LY3, this overall color being dependent on the direction of observation DI. Specific examples are described in more detail below.

As indicated above, it is considered in this example that each lens 18 diverts the light LG1 propagating in the internal layer LY2 until emerging outside the document DC1 through lenses 18 located along section 16. In general, in the case of zone Z1 represented in FIG. 2, the light LG1 emerging outside the document DC1 through section 16 is thus less visible to an observer of section 16 than in the absence of the lenses 18. On the contrary, in the case of the zone Z2 represented in FIG. 3, the light LG1 emerging outside the document DC1 through the lens 18 is more visible to an observer of the section 16 that in the absence of the lens 18. The alternation of zones of type Z1 (FIG. 2) and Z2 (FIG. 3) thus produces on the edge 16 an alternation of color which constitutes a visual pattern characteristic of this anti- fraud.

More specifically, Figures 4A, 4B and 4C are views of section 16 of document DC1. These figures illustrate in particular the visual effect, from the point of view of an outside observer, resulting from the propagation of light LG1 (in the first spectrum of wavelengths SP1) in the inner layer LY2 until emerging at outside document DC1 through the array 20 of lenses 18.

It is assumed in the examples considered here that the light LG1 emanates from any light source, intrinsic to the document DC1 or extrinsic to the document DC1.

Depending on the zone considered of the wafer 16, and therefore of the corresponding arrangement of the lens or lenses 18 of the array 20, the light LG1 emerging towards the outside produces an associated visual pattern. This visual motif (or effect) depends on the direction of observation DI adopted and results from the contribution more or less important colorimetric of each of the layers LY1 -LY3 imposed by the network 20 of lenses.

Thus, FIG. 4A represents the visual pattern obtained in the direction of normal DI observation with respect to wafer 16. In zone Z1 (FIGS. 1 and 2) of wafer 16, the propagation of light LG1 through lenses 18a and 18b produce the overall color C1 because it is the edges of the layers LY1 and LY3 which essentially contribute to producing the overall color visible to an observer. On the other hand, in the zone Z2 (FIGS. 1 and 3) of the slice 16, the propagation of the light LG1 through the lens 18c produces the overall color C2 because it is essentially the slice of the internal layer LY2 which contributes to producing the overall color C2 visible to an observer.

FIG. 4B represents the visual pattern obtained when the direction of observation DI forms an angle of observation Q1 with respect to the normal to section 16. In zone Z1 (FIGS. 1 and 2) of section 16, the propagation of the light LG1 through the lenses 18a and 18b produces an overall color C4 resulting from the respective contributions of the colors C1 and C2 coming from the edges of the layers LY1, LY3 and LY2. Due to the inclination adopted, the eye of an observer sees not only the color emanating from the inner layer LY2 but also that emanating from the upper layer LY1 and the lower layer LY3 due to the effect of divergence imposed by the lenses 18a and 18b on the light LG1 emerging towards the outside. The overall color C4 is therefore the result of an addition of the colors C1 and C2.

Still with reference to FIG. 4B, in the zone Z2 (FIGS. 1 and 3) of the wafer 16, the propagation of the light LG1 through the lens 18c produces the overall color C1 because it is essentially the slice of the upper layer LY1 and that of the lower layer LY3 which contribute to producing the overall color C1 visible by an observer. Due to the inclination adopted, the eye of an observer essentially perceives the color C1 emanating from the upper layer LY1 and from the lower layer LY3 due to the divergence effect imposed by the lens 18c on the emerging light LG1 outwards. FIG. 4C represents the visual pattern obtained when the direction of observation DI forms an angle of observation Q2, opposite the angle Q1, relative to the normal to section 16. For reasons similar to those described with reference to FIG. 4B, the propagation of the light LG1 through the lenses 18a and 18b produces in the zone Z1 (FIGS. 1 and 2) an overall color C4 resulting from the respective contributions of the colors C1 and C2 coming respectively from the layers of the layers LY1, LY3 and LY2. Similarly, the propagation of light LG1 through the lens 18c produces in the zone Z2 (FIGS. 1 and 3) an overall color C1 because it is essentially the edge of the lower layer LY3 which contributes to producing the color global C1 visible by an observer (since C1 = C3 in this example).

Thus, the array 20 of lenses 18 is arranged to produce, by divergence of the light LG1 exiting from the internal layer LY2 through the wafer 16, a series of color zones of at least two distinct colors. In this particular example, an alternation of colors is thus visible for an observer of section 16.

According to a particular example, this series of color zones forms an alternation of at least two distinct colors on the edge 16, whatever the direction of observation DI adopted.

More specifically, in the example considered above, the network 20 of lenses 18 is further configured so as to cause a change in color that can be seen in the areas of the wafer 16 which are covered by the lenses 18 by making vary the direction of observation DI vis-à-vis the lenses. FIGS. 4A-4C represent a particular implementation where the adjacent zones Z1 and Z2 produce overall colors which vary according to the direction of observation and which, moreover, are always different from each other whatever or the direction of observation DI adopted, other embodiments being however possible.

The configuration of the document DC1 thus makes it possible to generate a flashing of colors, this effect being visible at the level of the section 16 when the angle of observation is varied while causing the light LG1 to propagate at the first wavelength spectrum SP1 in the inner layer LY2 up to emerge outside of document DC1. By varying the direction of observation, it is thus possible to observe a so-called "walrus" visual effect according to which the zones of the edge 16 comprising at least one lens 18 collectively produce a particular blinking of different colors. These visual patterns being difficult to reproduce, the security of the DV1 document is thus reinforced.

In a particular example, the colors C1, C2 and C3 are all different from each other, in order to further complicate the visual effect thus obtained, and therefore make it more difficult for forgery or illicit reproduction of the document DC1.

In general, it is possible to adapt the visual effects generated on the wafer 18 by playing on different parameters including the characteristics of the lenses (shapes, dimensions, refractive index gradient, converging or diverging power ... ), the number and position of the lenses, as well as the colors of each of the layers in the stack.

To verify the integrity of the document DC1, it is therefore possible to propagate light LG1 in the internal layer LY2 in any suitable manner, and it is determined whether the visual effects generated on the wafer 16 through the lenses 18 correspond to a predetermined pattern. To do this, we can vary the direction of observation to check if we obtain a predetermined variation of visual patterns. This verification can possibly be done by an observer with the naked eye or, if necessary, by means of a control system, comprising a shooting device (for example a smartphone or any other device equipped with a camera ), the system being configured to make the optical acquisition of the visual patterns generated on the wafer 16 and to compare the patterns obtained with predetermined reference patterns.

Alternative embodiments are now described below.

Figures 5 and 6 schematically represent the document DC1 according to a particular embodiment. This variant differs from the embodiment shown in Figures 1-4 in that at least one of the upper layer LY1 and the lower layer LY3 comprises an opening 30 through which the internal layer LY2 is capable of receiving light excitement LG2 to a second spectrum of wavelengths SP2 different from the first spectrum of wavelengths SP1 previously mentioned.

We consider here the particular example where such an opening 30 is formed in the upper layer LY1. It is understood that one or multiple openings 30, of variable shape and dimensions, can be provided as required.

Note that the opening 30 may be a hole or orifice in the upper layer LY1 or a window formed of a transparent or translucent material in the excitation light LG2.

In addition, as shown in Figures 5-6, the document DC1 is characterized in this example in that the internal layer LY1 comprises an additive 32, for example a coloring agent, which emits light LG1 at the first spectrum of wavelengths SP1 when this additive is exposed to excitation light LG2.

It is thus possible to use a system comprising the document DC1 as well as an extrinsic light source 34 configured to emit excitation light LG2 at the second spectrum of wavelengths SP2 in the internal layer.

By second spectrum of wavelengths SP2 is meant a particular range of wavelengths. This range can be more or less narrow or concentrated essentially on one wavelength, depending on the case considered.

In the example considered here, the second spectrum of wavelengths SP2 in which the excitation light LG2 is found corresponds to (or includes) ultraviolet (UV) rays, while the first spectrum of lengths of waves SP1 in which the light LG1 is found corresponds to (or includes the) visible spectrum. LG1 light can be yellow for example.

In operation, the excitation light LG2 emanating from the extrinsic light source 34 enters through the opening 30 in the internal layer LY2 thus reaching the additive 32. The opening 30 thus acts as a skylight. Under excitation of the light LG2, the additive 32 in turn emits light LG1 (by luminescence effect), this light LG1 being characterized by the first spectrum of wavelengths SP1. The light LG1 thus emitted then propagates in the internal layer LY2 which acts as a waveguide to conduct the light LG1 to the lenses 18 located on the edge 16 of the document DC1. As already described above, the light LG1 emerging outside the document DC1 through the lenses 18 produces a particular visual effect depending in particular on the configuration of the lenses 18 and on the direction of observation DI.

To verify the integrity of the document DC1, it suffices to project the excitation light LG2 onto the internal layer LY2 through the opening 30 and to check the visual patterns generated on the wafer 16 through the lenses , as already explained previously.

According to an alternative embodiment, a light source of light intrinsic to the document DC1 can be used. Consider for example a variant which differs from the embodiment of Figures 5 and 6 in that the stack 14 comprises an intrinsic light source (not shown) configured to emit the excitation light LG2 already mentioned above, but this time directly inside the inner layer LY2. In this case, the opening 30 shown in Figure 5-6 is not necessary. The intrinsic light source is for example included in at least one of the upper layer LY1, the inner layer LY2 and the lower layer LY3. This intrinsic light source can for example be formed by at least one LED (light-emitting diode). In operation, the excitation light LG2 emanating from the intrinsic light source thus excites the additive 32 (FIG. 6) as described above. In particular, under excitation of the light LG2, the additive 32 included in the internal layer LY2 in turn emits light LG1 (by luminescence effect), this light LG1 being characterized by the first spectrum of wavelengths SP1 . The light LG1 thus emitted then propagates in the inner layer LY2 which acts as a waveguide to conduct the light LG1 to the lenses 18 located on the edge 16 of the document DC1. As already described above, the light LG1 emerging outside the document DC1 through the lenses 18 produces a particular visual effect depending in particular on the configuration of the lenses 18 and the direction of observation DI.

Other embodiments are however possible in the case where an intrinsic light source is used. FIG. 7 schematically represents the document DC1 according to a particular embodiment. This variant differs from the embodiment shown in Figures 1-4 in that the document DC1 comprises in or on the stack 14 at least one LED (light-emitting diode) 38 serving as an intrinsic light source for emitting light LG1 at the first spectrum of wavelengths SP1 in the inner layer LY2.

We consider here an example where a plurality of LEDs 38 are arranged in the stack 14, and more particularly in or in the vicinity of the internal layer LY2.

Document DC1 according to the variant shown in Figure 7 is further characterized in that it also includes an RF antenna 40 in or on the stack 14 for electrically supplying the LEDs 38 by means of a current I induced under excitation of an electromagnetic field FL.

It is thus possible to cause the emission in the internal layer LY2 of light LG1 at the first spectrum of wavelengths SP1 by exposing the document DC1, and more particularly its antenna 40, to an electromagnetic field FL obtained according to a any suitable method. According to a particular example, a control system is used, comprising a shooting device (for example a smartphone or any other device equipped with a camera), the system being configured to emit such an electromagnetic field FL, make the optical acquisition of the visual patterns generated on the wafer 16 and compare the patterns obtained with predetermined reference patterns.

According to a particular example, it is also possible to equip the stack 14 of the document DC1 with an RF antenna 40 as shown in FIG. 7 to electrically supply an intrinsic light source in the particular case where this intrinsic source is configured directly produce light LG1 in the first spectrum of wavelengths SP1 (as described above).

FIGS. 8A, 8B and 8C schematically represent the document DC1 according to a particular embodiment. This variant differs from the embodiment shown in Figures 1-4 in that the document DC1 includes a series of symbols 42 which is formed on the upper face S1 or on the lower face S2 of the stack 14, in the vicinity of the edge (16).

This variant is further characterized in that the array 20 of lenses 18 comprises at least one lens 18 on the edge 16 in alignment with each symbol 42 so as to cause a visual pattern to appear in association with each symbol by means of light LG1 (at the first spectrum of wavelengths SP1) which propagates in the internal layer LY2 until it emerges outside the document DC1 by section 16.

In other words, the network 20 is arranged so as to include a set 18a of at least one lens 18 on the edge 16 in alignment with each symbol 42. Each set 18a of at least one lens 18 thus generates a pattern respective visual in correspondence with the symbol 42 located opposite.

The symbols 42 may be alphanumeric characters or any other symbols adapted to the needs.

It is possible to configure the array 20 of lenses 18 so that it thus generates a respective visual pattern in correspondence with each characteristic, in accordance with a correspondence code (or rule) which associates a visual pattern with at least one respective physical characteristic of a symbol or a respective type of symbol.

In the example considered here, a correspondence code is applied which associates, as a function of the size of the base of each symbol 42, a particular color which must be generated by the assembly 18a of at least one lens corresponding, when a light LG1 with the first spectrum of wavelengths SP1 emerges through the network 20 towards the outside. The term “base” is understood here to mean a lower portion of each symbol 42, this portion being adjacent to the edge 16 of the stack 14.

Thus, as shown in Figure 8B in this example, the visual patterns generated in each area of the wafer 16, that is to say by each set 18a located in correspondence with a respective symbol 42, has an overall color conforms to a specific correspondence code. More specifically, the letters "M", "A", "R" and "N" all have relatively wide bases (lower portions) while the letters "T" and "I" have, in comparison, relatively narrow bases. This is why, in normal observation (observation angle Q = 0 °), the respective sets 18a, of at least one lens 18 each, generate the color C1 opposite the letters "M", "A", " R "and" N "and generate the color C2 next to the letters" T "and" I ", in accordance with the correspondence code applied.

Note that this is only an example of correspondence code, other examples of implementation being possible, taking into account at least any physical characteristic (size of all or part of the symbol, nature of the symbol , form ...) of symbols 42 and / or the type (or meaning) of symbols 42.

Thus, according to a particular example, a correspondence code is applied which defines for each type of symbol a respective visual pattern (or optical pattern). For example, the characters "A", "B", "C", etc. each constitute a distinct type of symbol to which the correspondence code associates a respective visual motif. The visual pattern is characterized for example by a particular color which must be generated by the assembly 18a of at least one corresponding lens, when a light LG1 with the first spectrum of wavelengths SP1 emerges through the network 20 towards l 'outside. In this way, the lens array 20 is configured as a function of the type, and therefore of the meaning of the symbols 42.

To verify the integrity of the document DC1 as represented in FIGS. 8A- 8C, it is therefore possible to propagate light LG1 in the internal layer LY2 in any suitable manner, and it is determined whether the visual effects generated on section 16 in correspondence with each symbol 42 comply with the applicable correspondence code. To do this, the direction of observation DI can be varied in order to check whether a variation in visual patterns is obtained, respecting what is defined by the correspondence code. This verification can possibly be done by an observer with the naked eye or, if necessary, by means of a control system, comprising shooting means (for example a smartphone or any other device equipped with a camera ), the system being configured to make the optical acquisition of the visual patterns generated on the edge 16, to compare the patterns obtained with the symbol 42 located in correspondence, and to check whether each symbol-visual motif association complies with the applicable correspondence code.

In the example considered here, the symbols 42 are adjacent to the contour of the surface S1 and are therefore located near the edge 16, which makes it possible to facilitate the verification of the visual patterns generated by the light LG1 through the lenses 18, in correspondence with symbols 42.

As already indicated, the invention can be applied to various types of documents. FIG. 8C represents the exemplary embodiment of FIGS. 8A and 8B in a particular case where the document DC1 is a passport, other examples of implementation being however possible. In this example, the network 20 of lenses 18 is arranged on the edge of a page (or cover) of the passport, in correspondence with inscriptions 42 which represent, for example, the name of the passport holder.

According to a particular embodiment shown in Figure 9, document DC1 the lenses 18 of the lens array 20 are arranged in notches (or recesses) 45 formed on the edge 16 of the stack 14 (according to z). The thickness e1 of each lens 18 is less than the depth e2 of the respective notch 45 so as to mechanically protect the lenses. These notches 45 can be formed for example by cutting or stamping the stack 14, before the lenses 18 are formed.

The notches 45 thus offer mechanical protection against mechanical degradation due to wear, for example.

FIG. 10 represents, in the form of a diagram, an example of a method for manufacturing a DC1 document as described above.

In a step E2, the stack 14 is formed by stacking together the layers LY1, LY2 and LY3 as already described. These layers can be fixed with an adhesive, plasticized by hot pressing or any other suitable means.

During a step E4, the lenses 18 of the array 20 on formed on the edge 16 of the stack 14 so as to obtain an arrangement as already described above. In a first example, the lenses 18 are formed by a laser ablation technique on the edge 16 of the stack 14.

In a second example, use is made of a laser melting and delivery technique of the material of the stack 14 so as to form the lenses 18 on the edge 16 of the stack 14. The formation of the lenses then results from the interaction between the laser and the material, in particular due to the effects of the plasma on the molten material at the edge 16 of the stack 14.

If appropriate, the notches 45 shown in FIG. 9 are formed (by cutting or stamping) before the formation E4 of the lenses 18.

In general, the invention thus makes it possible to secure documents by equipping them with a device intended in particular for detecting when the constituent layers of these documents are separated, so as to prevent fraudulent manipulation.

The invention provides in particular an arrangement of lenses on the edge of a document so as to generate characteristic visual patterns when appropriate light passes through the transparent or translucent internal layer until it emerges outside the document at through lenses.

The visual patterns (or effects) generated by the light passing through the lenses are a function of several parameters, including in particular the alignment of the lenses with respect to the thickness (or the edge) of each constituent layer of the document.

The arrangement of lenses thus forms an advantageous anti-fraud device making it possible to detect if at least two of the constituent layers of the document are separated after the production of said document (insofar of course where at least part of the network of lenses covers these layers at their respective edges). The delamination (or separation) of at least two constituent layers at the level of the wafer leads in fact to an at least partial alteration or rupture of the lens network which results in a modification of the visual effect produced by the propagation of the light emerging through the edge. Such a modification of the visual effect thus indicates manipulation or alteration of the document by delamination. The invention thus makes it possible to detect when layers of the document have been separated (or delaminated) or recombined (case of falsification or counterfeit documentary) after manufacture of the document equipped with the lens network. In addition, due to the complexity of the anti-fraud device of the invention, and in particular due to the difficulty of obtaining good alignment of the lenses on the thickness of the wafer, it is difficult for a counterfeiter to reproduce the authentic visual effect, whether on an original document after delamination or on a fraudulent copy.

The different embodiments and variants described in this document also propose ways to further complicate the anti-fraud device of the invention further in order to make any illicit manipulation even more difficult. Document security can be further enhanced.

A person skilled in the art will understand that the embodiments and variants described above are only non-limiting examples of implementation of the invention. In particular, a person skilled in the art can envisage any adaptation or combination of the embodiments and variants described above in order to meet a very specific need.

Claims

[Claim 1] Document (DC1) including:

a stack (14) of layers comprising at least one upper layer (LY1), a lower layer (LY3) and an internal layer (LY2) interposed between the upper layer and the lower layer, the internal layer being transparent or translucent so as to forming a waveguide for guiding light (LG1) at a first spectrum of wavelengths (SP1) through the internal layer,

the internal layer collectively forming with the upper layer and the lower layer a wafer (16) which delimits an outline of the stack; and

an array (20) of lenses (18) formed on at least part of the wafer (16) of the stack (14), said lenses being positioned along the wafer to converge or diverge the light (LG1) at the first spectrum of wavelengths when it propagates in the internal layer until it emerges outside the document by said slice (16), so as to show on the slice a series of colored zones (Zl, Z2) of at least two distinct colors (Cl, C2, C4).

[Claim 2] The document of claim 1, wherein:

the upper layer (LY1) and the lower layer (LY3) are opaque; or

the upper layer (LY1) and the lower layer (LY3) have a refractive index less than or equal to that of the internal layer (LY2).

[Claim 3] Document according to claim 1 or 2, in which the lens array (20) constitutes a security device covering at least part of the wafer (16) to visually testify to the integrity of the stack (14 ) as long as said layers are not separated from each other.

[Claim 4] Document according to any one of claims 1 to 3, in which the lenses (18) are each positioned to generate, in a corresponding zone of the edge (16), an overall color from the colorimetric contribution of at least one of the upper layer (LY1), the inner layer (LY2) and the lower layer (LY3), said color being dependent on the direction of observation (DI).

[Claim 5] Document according to any one of claims 1 to

4, in which the array (20) of lenses (18) is configured so as to cause a color change which can be seen in the areas of the wafer (16) which are covered by the lenses by varying the direction of observation (DI ) vis-à-vis said lenses.

[Claim 6] Document according to any one of claims 1 to

5, in which the series of color zones forms an alternation of at least two distinct colors on the edge (16), whatever the direction of observation.

[Claim 7] Document according to any one of claims 1 to

6, in which the upper and lower layers are reflective so as to confine the light (LG1) to the first spectrum of wavelengths (SP1) in the inner layer (LY2).

[Claim 8] Document according to any one of claims 1 to

7, in which each lens (18) of the lens array is positioned on the edge (16) so as to converge an incident light, received on the edge from outside the document, essentially on the section of one among the lower layer (LY3), the upper layer (LY1) and the inner layer (LY2).

[Claim 9] Document according to any one of claims 1 to

8, in which the lenses (18) are formed:

by a laser ablation technique on the edge (16) of the stack; or

by a laser melting and delivery technique of the material of the stack (14) so as to form the lenses on the edge (16) of said stack.

[Claim 10] Document according to any one of claims 1 to

9, in which the lower layer or the upper layer comprises an opening (30) through which the internal layer (LY2) is capable of receiving excitation light (LG 2) at a second wavelength spectrum (SP2) different from the first wavelength spectrum (SP1), the inner layer comprising an additive (32) which emits light ( LG1) to the first spectrum of wavelengths (SP1) when said additive is exposed to excitation light (LG2).

[Claim 11] A document according to any of claims 1 to 10, wherein the document comprises an intrinsic light source (34) configured to emit light at the first spectrum of wavelengths in the inner layer.

[Claim 12] The document of claim 11, wherein the

document (DC1) comprises in or on the stack (14) at least one LED (30) serving as an intrinsic light source for emitting light at the first spectrum of wavelengths in the internal layer,

the document further comprising an RF antenna (40) in or on said stack for electrically supplying said at least one LED by means of a current (I) induced under excitation of an electromagnetic field (FL).

[Claim 13] Document according to any one of claims 1 to 12, in which a series of symbols (42) is formed on one side

upper of the stack (14) or on a lower face (S2) of

the stack, in the vicinity of the edge (16),

the array (20) of lenses comprising at least one said lens (18) on the wafer in alignment with each symbol (42) so as to cause a visual pattern (C1, C2) associated with each symbol to appear from the light ( LG1) to the first spectrum of wavelengths (SI) when the latter propagates in the internal layer (LY2) until it emerges outside the document (DC1) by said slice (16).

[Claim 14] The document of claim 13, wherein each visual pattern generated by the lens array (20) conforms to a match code which associates a visual pattern with at least one respective physical characteristic of a symbol or a respective type of symbol. [Claim 15] Document according to any one of claims 1 to 14, in which the lenses (18) of the array (20) of lenses are arranged in notches (45) formed on the edge (16) of the stack, the thickness (el) of each lens being less than the depth (e2) of the respective notch so as to mechanically protect said lenses.