EP3765307A1

EP3765307A1 - Document capable of generating a colour image

Info

Publication number: EP3765307A1
Application number: EP19717539.1A
Authority: EP
Inventors: Benoît BERTHE; Coralie VANDROUX
Original assignee: Idemia France SAS
Current assignee: Idemia France SAS
Priority date: 2018-03-16
Filing date: 2019-03-14
Publication date: 2021-01-20
Also published as: FR3079052A1; AU2019235502A1; US20210016593A1; KR20200132967A; WO2019175514A1; JP2021518282A; US11007811B2; AU2019235502B2

Abstract

The invention relates to a document (2) capable of generating a colour image (6), comprising: a set of pixels (20) printed on or in a substrate (2), each pixel (20) forming a pattern comprising an arrangement of sub-pixels (22) of at least two different colours; and an array of lenses (LN) disposed facing the set of pixels so as to generate the colour image (6) by focusing or diverging an incident light through the lenses on at least one part of the sub-pixels (22), each lens (LN) being positioned, relative to an associated pixel (20) located opposite, to focus or diverge the incident light on at least one of the sub-pixels (22) of said associated pixel so as to modify the contribution of the respective colours of the sub-pixels (22) of the associated pixel (20), in a region of the colour image (6) generated through said lens, relative to the pattern intrinsically formed by the associated pixel (20) independently of said lens (LN).

Description

Document capable of generating a color image

Background of the invention

The invention relates to the field of color image formation and relates more particularly to a device or object, such as a document for example, capable of generating a personalized color image.

The invention finds particular applications in the formation of identity images in identity documents such as official documents: identity cards, credit cards, passports, driving licenses, secure entry badges and so on.

Various printing techniques have been developed over time to achieve color printing. In particular, the production of identity documents such as those mentioned above requires color images to be made secure in order to limit the risk of falsification by malicious individuals. The manufacture of such documents, particularly at the level of the identity image of the wearer, needs to be sufficiently complex to make it difficult for reproduction or falsification by an unauthorized individual.

Thus, in a known manner, certain official documents comprise, for example, guilloches representing a pattern by means of a complex set of printed lines, difficult to reproduce without sophisticated equipment and adequate expertise. Various security elements (holograms, secure inks, etc.) have been developed, but these are not always sufficient to prevent fraud, especially in view of the significant resources currently available to certain counterfeiters.

Moreover, the techniques of forming color images used today, especially in secure identity documents, do not always make it possible to obtain a satisfactory quality of visual rendering. Problems arise especially when the imaging techniques used are limited in their ability to saturate certain colors. In other words, the color gamut (ability to reproduce a color range) of known color image forming techniques is sometimes limited. When, for example, an identity image is created on a document, it is generally composed of a face surrounded by a light zone, even white, constituting the background image. It is not always possible to obtain sufficiently saturated colors on the face area or on the background, so that the same face placed on a monochrome background for example, and not sufficiently clear, has a satisfactory contrast between this face and the bottom fully satisfactory for the observer.

There is now a need to form securely personalized color images, for example in identity documents, such as those mentioned above. In particular, there is a need for flexible and secure personalization of color images in documents or the like, so that even if a document is illegally obtained by an individual, the individual can not customize the color image as desired without this is detectable during a proper inspection.

No solution that can offer an appropriate level of security and flexibility also makes it possible today to obtain a gamut of sufficient color, in particular to obtain the color shades necessary for the formation of certain high-quality color images, especially when image areas must have a highly saturated level in a given color, or a very clear identity image background for example, that is to say totally desaturated and bright.

Object and summary of the invention

The invention is intended in particular to overcome the disadvantages and shortcomings of the state of the art mentioned above.

For this purpose, the present invention relates to a document capable of generating a color image, comprising:

a set of pixels printed on or in a substrate, each pixel forming a pattern comprising an arrangement of sub-pixels of at least two different colors; and

a lens array disposed opposite the set of pixels so as to generate the color image by focusing or diverging incident light through the lenses on at least a portion of the sub-pixels,

each lens being positioned, relative to an associated pixel located opposite, to focus or diverge the incident light on at least one of the sub-pixels of said associated pixel so as to modify the contribution of the respective colors of the sub-pixels; pixels of the associated pixel, in a region of the color image generated through said lens, with respect to the pattern intrinsically formed by the associated pixel independently of said lens.

The invention advantageously makes it possible, thanks to the lenses, to create shades of colors so as to form a color image by the interaction between the lens array and the set of pixels. The color image is formed by the combination of the lens array and the set of pixels located vis-à-vis. Without the addition of lenses to judiciously orient the incident light, the set of pixels is only a blank arrangement of color pixels to the extent that this set is devoid of the information characterizing the color image. It is the lens array that is configured, according to the chosen subpixel arrangement, to customize the visual appearance of the pixels and thereby generate, by juxtaposition of the visual appearances of the pixels, the final color image.

In particular, it is possible to configure the lenses (shape, positioning, etc.) so as to select certain colors from among the different colors present in the set of pixels. Conversely, it is possible to mask or reduce the color contribution of certain sub-pixels in the visual rendering of the final color image.

The invention makes it possible in particular to generate a highly saturated color zone in the desired color or even desaturated in the particular case where the target sub-pixel is white in color.

The invention thus makes it possible to form monochrome image areas of good quality, while ensuring a high level of complexity that guarantees the security of the image with respect to fraud. The invention makes it possible, for example, to produce a highly saturated or desaturated background image in a given color, such as white, for example.

By implementing the principle of the invention, it is possible to easily detect fraud when the image has been falsified or illegally reproduced. In addition, this level of complexity and security of the image achieved through the invention is not detrimental to the quality of the visual rendering of the image. This does not prevent in particular the formation of color images comprising areas requiring significant contrast as in the case of a face vis-à-vis a background image. The invention makes it possible to form quality color images from a large gamut of color.

According to a particular embodiment, each pixel of said set of pixels forms an identical pattern of sub-color pixels. According to a particular embodiment, the set of pixels is configured so that the sub-pixels are uniformly distributed on or in the substrate.

According to a particular embodiment, each pixel of said set of pixels is configured such that each sub-pixel has a unique color in said pixel.

According to a particular embodiment, the lens array is formed from a layer comprising surface deformations defining the microlenses, said layer being the substrate or a layer laminated with the substrate.

According to a particular embodiment, the sub-pixels in the set of pixels comprise a reflective surface positioned under the sub-pixels for reflecting the incident light through the lens array.

According to a particular embodiment, at least one lens in the lens array is a convergent lens configured to focus incident light received so as to enhance the color contribution of at least one subpixel of the associated pixel, in the region. corresponding color image generated through said lens, with respect to the respective color contribution of each other sub-pixel of said associated pixel.

According to a particular embodiment, at least one lens in the lens array is a convergent lens configured to focus incident light received on only one of the subpixels of the associated pixel so as to mask the color of each other sub-pixel of said associated pixel in the corresponding region of the color image generated through said lens.

According to a particular embodiment, in a monochrome region of the color image, each lens of the lens array is a convergent lens configured to focus incident light received on a single subpixel of the same predetermined color in the associated pixel. so as to display as a single color the predetermined color in said monochrome region of the color image.

According to a particular embodiment, at least one first lens of the lens array is a convergent lens configured to focus incident light received on at least two sub-pixels of the associated pixel so as to appear in a corresponding region of the image color a hybrid color resulting from a combination of the colors of said at least two sub-pixels, wherein said first lens has, in its smallest dimension, a smaller maximum dimension of 150 μm.

According to a particular embodiment, at least one lens of the lens array is a diverging lens configured to diverge incident light received by the lens so as to reduce the color contribution of at least one subpixel of the associated pixel, in the corresponding region of the color image generated through said lens, with respect to the respective color contribution of each other sub-pixel of said associated pixel.

According to a particular embodiment, the document furthermore comprises:

a laserizable transparent layer arranged facing the set of pixels, said laserizable transparent layer being at least partially carbonized by laser radiation so as to include opacified regions locally opposite sub-pixels to produce gray levels in the color image generated through the lenses.

According to a particular embodiment, the probability density of the presence of each sub-pixel color is constant in the set of pixels.

The invention also relates to a method for generating an image in a document as defined above.

More particularly, the invention provides a method for generating a color image, comprising:

an impression of a set of pixels on or in a substrate, each pixel forming a pattern comprising an arrangement of sub-pixels of at least two different colors; and

a formation of a lens array arranged opposite the set of pixels so as to generate the color image by focusing or diverging incident light through the lenses on at least a portion of the sub-pixels, each lens being positioned, relative to an associated pixel located opposite, to focus or diverge the incident light on at least one of the sub-pixels of said associated pixel so as to modify the contribution of the respective colors of the sub-pixels of the associated pixel, in a region of the color image generated through said lens, with respect to the pattern intrinsically formed by the associated pixel independently of said lens. It will be noted that the various embodiments mentioned above in relation to the document of the invention as well as the associated advantages apply analogously to the generation method of the invention.

According to a particular embodiment, the method comprises:

a supply of a first transparent layer; and

a projection on the first transparent layer of a first laser radiation so as to form the lenses by deformation on the surface of said first transparent layer.

According to a particular embodiment, the method comprises:

a supply of a first transparent layer; and

an embodiment on the first transparent layer of a projection of transparent material by using a 3D printer head so as to form lenses on the surface of the first transparent layer.

According to a particular embodiment, during the forming step, each lens is positioned relative to the associated pixel located vis-à-vis independently of the positioning of the other lenses of said lens array.

According to a particular embodiment, at least one first lens of the lens array is a convergent lens configured to focus incident light received on at least two sub-pixels of the associated pixel so as to appear in a corresponding region of the image color a hybrid color resulting from a combination of the colors of said at least two sub-pixels,

wherein said first lens is formed so that it has, in its smallest dimension, a smaller maximum dimension of 150 μm.

According to a particular embodiment, the method comprises a determination of respective weights assigned to each of said at least two subpixels, said weights representing respective contributions of each subpixel in the color combination producing the hybrid color;

said first lens being configured relative to the associated pixel in accordance with said respective weights assigned to at least two subpixels.

Brief description of the drawings Other features and advantages of the present invention will emerge from the description given below, with reference to the accompanying drawings which illustrate embodiments having no limiting character. In the figures:

- Figure 1 shows schematically a document according to a particular embodiment of the invention;

- Figure 2 is a sectional view schematically showing a document according to a particular embodiment of the invention;

FIGS. 3A to 3D diagrammatically represent sets of pixels according to particular embodiments of the invention;

- Figure 4 is a sectional view along IV showing schematically a document according to a particular embodiment of the invention;

- Figure 5 is a perspective view schematically showing the document of Figure 4, according to a particular embodiment of the invention;

FIGS. 6 and 7 are diagrammatic views of the set of pixels of the document of FIG. 4, according to a particular embodiment of the invention;

FIG. 8 is a top view diagrammatically representing the visual appearance of an image generated by the document of FIG. 4, according to a particular embodiment of the invention;

- Figure 9 is a sectional view along IX schematically showing a document according to a particular embodiment of the invention;

- Figure 10 is a perspective view schematically showing the document of Figure 9, according to a particular embodiment of the invention;

- Figure 11 is a top view schematically showing the set of pixels of the document of Figure 9, according to a particular embodiment of the invention;

FIG. 12 is a top view diagrammatically representing the visual appearance of an image generated by the document of FIG. 9, according to a particular embodiment of the invention;

- Figure 13 is a sectional view schematically showing a document according to a particular embodiment of the invention;

- Figure 14 is a sectional view schematically showing a document according to a particular embodiment of the invention; - Figure 15 is a sectional view schematically showing a document according to a particular embodiment of the invention;

FIG. 16 represents, in the form of a diagram, the steps of a method for generating a color image, according to a particular embodiment of the invention; and

FIG. 17 represents, in the form of a diagram, the steps of a method for generating a color image, according to a particular embodiment of the invention.

Detailed description of several embodiments

As indicated above, the invention relates to the formation of color images and aims in particular a device or object, such as a document for example, capable of generating a personalized color image from color pixels.

The device in the sense of the invention can take various forms and have various functions, a characteristic being that it is capable of generating a color image according to the principle of the invention as disclosed in this document.

In the remainder of this document, examples of implementations of the invention are described in the case of a document capable of generating a color image according to the principle of the invention. This document can be any document, such as booklet, card or other, including an identity document such as for example: an identity card, a credit card, a passport, a driver's license, a badge of secure entry, etc.

However, it is understood that the invention is not limited to documents, but also applies to other objects configured to generate a color image according to the principle of the invention.

Similarly, the examples described below aim to generate an identity image. However, it is understood that the image considered can be any. In particular, the image can be (or include a region) monochrome or multicolor.

The invention proposes to produce customized color images that are highly secure and have good image quality. To this end, the invention, according to various embodiments, implements a device capable of generating a color image, comprising: a set of pixels printed on or in a substrate, each pixel forming a pattern comprising a sub-arrangement of pixels of at least two different colors; and a lens array arranged next to the set of pixels so as to generate the color image by focusing or diverging incident light through the lenses on at least a portion of the sub-pixels.

Each lens can be positioned (or configured), relative to a pixel (called "associated pixel") situated opposite, to focus or diverge the incident light on at least one of the sub-pixels of said associated pixel of so as to modify the contribution of the respective colors of the subpixels of the associated pixel, in a region of the color image generated through the lens, with respect to the pattern intrinsically formed by the associated pixel independently of (or without) said lens.

In other words, each lens can be positioned (or configured), relative to an associated pixel located opposite, to focus or diverge the incident light on at least one of the sub-pixels of said associated pixel so as to modify the contribution of the respective color of at least one sub-pixel of the associated pixel, in a region of the color image corresponding to said pixel, with respect to the respective color contribution of each other sub-pixel of said associated pixel.

The lenses thus make it possible to create shades of color so as to form (or generate) a color image by the interaction between the lens array and the set of pixels. More particularly, each lens array allows color shades to be created so as to form a unique color image specific to each array and distinct from the pixel pattern. The invention also relates to a corresponding method for producing (or generating) a color image.

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

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 schematically shows a device 2 according to an exemplary embodiment of the invention. In this example, the device 2 is a document comprising an identity image 6 formed in or on a device body (or substrate) 4. In this example, the document 2 takes the form of a card although other embodiments are possible.

The color image 6 represents in this example a face 8 surrounded by an image background 6 which is monochrome, white or pale blue, for example. Figure 2 is a sectional view schematically showing the color image 6 formed in the document 2 shown in Figure 1, according to a particular embodiment. More particularly, the document 2 comprises a substrate 12 in or on which is disposed a network (or arrangement) of LN lenses.

A set of pixels 20, also called tiling (or tiling of pixels), is printed in the substrate 12, each pixel forming a pattern having a subpixel arrangement 22 of at least two different colors. Examples of subpixel patterns, the possible configurations of which are multiple, are described later with reference in particular to FIGS. 3A-3D.

The substrate 12 is here transparent in order to let at least part of the incident light pass through the lenses LN so as to reach the color pixels 20. The pixels 20, and more particularly their sub-pixels 22, comprise in this example a surface reflective 23 located below the sub-pixels to reflect (at least partially) the incident light received through the lens array LN. This reflecting surface is for example a white surface.

As shown in FIG. 2, the LN lens array is arranged facing the set of pixels 20 so as to generate the color image 6 (FIG. 1) by focusing or diverging an incident light through the lenses LN on at least a part of the sub-pixels 22. As described below, the lenses can be configured in different ways and, in particular, can be convergent and / or divergent depending on the particular case. In the example under consideration, the lenses LN converge to converge the incident light on at least one of the subpixels 22 of the associated pixels 20 facing each other.

More particularly, each lens LN is positioned, relative to a pixel 20 facing said "associated" pixel, to focus or diverge the incident light on at least one of the sub-pixels 22 of the associated pixel 20 so as to modify the contribution of the respective colors of the subpixels 22 of the associated pixel 20, in a region of the corresponding color image 6 (i.e., generated through this lens LN), with respect to the pattern intrinsically formed by the associated pixel 20 independently of said LN lens.

In other words, the lenses LN are configured so as to converge or diverge the incident light on certain sub-pixels 22 so as to reveal (reveal) the image color 6, from the set of pixels 20, giving priority to the color contribution of certain sub-pixels relative to others.

LN lenses thus make it possible to create color shades so as to form a color image 6 by the optical interaction between the LN lens array and the set of pixels 20. The color image 6 is thus formed by the combination of LN lens array and the set of pixels 20 located vis-à-vis. Without the addition of LN lenses to judiciously orient the incident light, the set of pixels 20 is only a blank arrangement of color pixels to the extent that this set is devoid of the information characterizing the color image 6. It is the LN lens array that is configured, according to the chosen subpixel arrangement 22, to customize the visual appearance of the pixels 20 and thereby generate, by juxtaposition of the visual appearances of the pixels, the color image. final 6.

The manner in which the lenses can guide the incident light to change the color contribution of some subpixels 22 to other subpixels in the final color image 6 is described in more detail later.

In particular, it is possible to configure the lenses LN (shape, positioning, etc.) so as to select certain colors from among the different colors present in the set of pixels 20. Conversely, it is possible to mask or reduce the contribution in color of some subpixels 22 in the visual rendering of the final color image 6.

As described later, it is possible to further add opacifying elements (black or dark, for example) opposite some subpixels 22 to create gray levels of the resulting color image 6, and so on. generate contrast in the color image after the alignment of the lenses on the appropriate subpixels has selected an appropriate hue.

The LN lenses arranged opposite the set of pixels 20 may have various shapes, sizes and configurations (magnification, converging or diverging power ...). Depending on the particular case, LN lenses may for example be spheroidal or cylindrical, for example.

Furthermore, the set of pixels 20 in the sense of the invention can be in various forms, configurations, dimensions, etc. In particular, each pixel of the set of pixels 20 may form an identical pattern of subpixels 22 of color. In this case, the set of pixels consists of a single subpixel pattern which repeats one plurality of times. This arrangement of subpixels is said to be "virgin" in the sense that it does not intrinsically form (that is to say without the addition of LN lenses and / or opacifying elements) the color image 6.

According to a particular example, each pixel 20 has an identical pattern of subpixels 22 in the same orientation through the set of pixels 20. It is thus possible to distribute in an identical manner the color sub-pixels in the set pixels (as illustrated for example in Figure 3A), which facilitates the formation of the lenses to the extent that the same frame (or the same layout) is used in each pixel.

According to a particular example, each pixel 20 has an identical pattern of sub-pixels 22, variations of orientation of this pattern being however made between certain pixels relative to each other, through the set of pixels 20. Otherwise said, the same pattern of sub-pixels 22 of color is then found in all the pixels 20 of said set but according to at least two different orientations (for example by applying rotations of 90 ° and / or 180 ° on the same pattern which is repeats through the set of pixels 20). FIG. 3C thus illustrates an example in which the same pattern of color sub-pixels 22a-22d is found in two different orientations (rotation of 180 °) in the set of pixels 20. This variant thus makes it possible to form a blank set color subpixels providing the flexibility necessary to generate any image through the lenses LN, while allowing to incorporate the same pattern in variable orientations to form for example a signature or a secure element, specific to each color image which is difficult to reproduce and easily detectable in case of fraud.

The set of pixels 20 may be configured so that the sub-pixels are uniformly distributed on or in the substrate 12. In other words, the set of pixels may form a regular or periodic arrangement of pixels 22, forming sub-patterns. -pixels identical or not depending on the case.

The set of pixels 20 may form a matrix of pixels consisting of rows and columns of sub-pixels 22. These rows and columns may be rectilinear and optionally orthogonal to each other.

In a particular example, each pixel 20 forms a pattern composing a subpixel arrangement 22 of at least two different colors, the probability density of the presence of each subpixel color being constant in the pixels 20 of the pixel arrangement. In other words, if we consider pixels 20 of n color subpixels (where n is an integer), the surface proportion of each color (formed by one or more subpixels) is identical in each pixel 20. the set of pixels. By way of example, the following densities can be found in each pixel: 30% yellow, 20% magenta, 40% cyan and 10% white). In this particular example, each pixel 20 can thus have an identical pattern of subpixels 22 of color in the same orientation across the pixel array 20 or, optionally, in an orientation that varies in the pixel array 20 (according to random variations or according to regular or other variations).

In particular, in more complex examples, a random arrangement of pixels 20 is possible. In particular, it is possible to organize the distribution of the sub-pixels 22 randomly, but in such a way that the probability density of the presence of each sub-pixel color is constant in the pixels of the set of pixels. In this case, it is necessary that, in a given zone of the pixel array 20, the desired color (s) can be selected using the LN lenses even if the corresponding subpixels are not exactly at their desired color. theoretical coordinates supposed.

In a particular example, each pixel of the set of pixels is configured such that each of the subpixels 22 has a unique color in said pixel 20. A pixel 20 may thus be composed of a plurality of subpixels 22 , all of distinct color. As a variant, it is possible to define the pixels 20 so that they comprise at least two sub-pixels 22 of the same color out of all their sub-pixels (for example, 2 sub-pixels in each primary color), under reserve that each pixel comprises at least two subpixels 22 of different color.

The colors of the sub-pixels 22 may vary according to the case and may be primary colors from which the color image 6 is generated in combination with the LN lens array. In a particular example, each pixel 20 comprises sub-pixels 22 in the primary colors red / green / blue (RGB), possibly with white, or in primary colors yellow / magenta / cyan, possibly with white. A white area may optionally be provided in the pixel array 22 between subpixel rows and columns 22 to avoid color overlap. Particular examples of tiling (arrangement) of pixels 20, which can be implemented in a device of the invention such as document 2 shown in FIGS. 1-2, are now described with reference to FIGS. 3A, 3B, 3C and 3D. It should be noted that these implementations are presented only as non-limiting examples, many variants being possible in terms in particular of the arrangement and shape of the pixels and sub-pixels, as well as the colors assigned to these subpixels.

Fig. 3A is a top view showing a set of pixels 20 according to a particular embodiment. In this example, the tiling forms an array of rows and columns of pixels, orthogonal to each other. Each pixel 20, of square shape, forms a pattern composed of 4 sub-pixels 22, denoted 22a to 22d, also of square shape. In this example, the subpixels 22 all have a unique color in the pixel 20 considered. The pixels 20 are uniformly distributed so that the same subpixel pattern 22 repeats periodically in a region of the substrate 12.

Fig. 3B is a top view showing another example of regular paving in which each pixel 20 is composed of 3 subpixels 22, denoted 22a to 22c, each of a distinct color. The sub-pixels 22 are here hexagonal.

Fig. 3C is a top view showing another example of regular paving in which each pixel 20 is composed of 4 subpixels 22, denoted 22a to 22d, each of a distinct color. The sub-pixels 22 are here of triangular shape.

FIG. 3D is a top view showing another example of regular paving in which each pixel 20 is composed of 4 subpixels 22, denoted 22a to 22d, each of a distinct color. The sub-pixels 22 are here of rectangular shape and are arranged in line, that is to say arranged parallel to each other to form rectilinear columns of sub-pixels.

Examples of particular implementation of the device 2 described above with reference to FIGS. 1, 2 and 3A-3D are now described below. More particularly, a first particular implementation of document 2 (FIG. 1) is described with reference to FIGS. 4 to 8.

The device 2 comprises in this example a substrate 12 in which is disposed a set of pixels 20, each pixel comprising a plurality of sub-pixels 22. A lens array, denoted here LN1, is arranged opposite the set of pixels 20 from so as to generate the color image 6 (FIG. 1) by focusing an incident light 30 on certain sub-pixels 22.

More particularly, as illustrated in FIGS. 4 and 5, the substrate 12 comprises in this example a transparent top layer 12a disposed on a white lower layer 12b. The set of pixels 20 is printed on the upper face of the lower layer 12b or on the lower face of the upper layer 12a, so as to be at the interface between the layers 12a and 12b, inside the substrate According to one variant, the set of pixels 20 is printed on the upper face of the substrate 12.

As already indicated, each pixel 20 forms a pattern having an arrangement of subpixels 22 of at least two different colors. The sub-pixels 22 may be made according to any color printing technique that the skilled person can choose according to the particular case. The set of pixels used in this example is described later with reference to FIG.

In this example, lenses LN1 are formed in a layer 14 having surface deformations defining the lenses. This layer 14 covers the substrate 12, the layer 14 and the substrate 12 being for example laminated together. The layer 14 may be for example silica glass or polycarbonate, or any transparent material of a density different from that of the air so that there is refraction of light and thus lens effect. According to a variant, the LN1 lens array is formed directly in the substrate 12 which then comprises surface deformations defining the lenses, no additional layer 14 being then necessary.

As illustrated in FIGS. 5-6, the lenses LN1 here are of cylindrical shape and extending parallel to each other.

The lenses LN1 are in this example convergent lenses. The array (or arrangement) of LN1 lenses is arranged facing the set of pixels 20 so as to generate the color image 6 by focusing an incident light 30 through the lenses on at least a portion of the sub-pixels 22. Each lens LN1 is positioned, relative to an associated pixel 20 facing each other, to focus the incident light 30 on at least one of the sub-pixels 22 of the associated pixel 20 so as to modify (or modulate ) the contribution of the respective colors of the subpixels 22 of the associated pixel 20, in a region of the color image 6 generated through said lens LN1, with respect to the pattern inherently formed by the associated pixel 20 independently of said lens LN1. In this document is meant by a pattern formed intrinsically by a pixel, a pattern formed by the colors of the sub-pixels of said pixel, this pattern being considered as such, without taking into account the modulation effect resulting from the positioning of a pixel. lens in vis-à-vis.

As already explained, the substrate 12 and the layer 14 are transparent so as to let the incident light pass at least partially through the lenses LN1 until reaching the color pixels 20. The pixels 20, and more particularly their sub-pixels 22 , in this example, comprise a reflective surface 23, located under the sub-pixels, for reflecting (at least partially) the incident light 30 received through the LN1 lens array. The layers 12 and 14 are for example polycarbonate. The reflective layer 23 may be a white surface beneath the pixels.

As shown in FIG. 4, each LN1 lens has an incidence surface (or lens surface) SI, adapted to receive incident light 30, and further defines, on the surface of the pixel array 20, a useful surface area S2 on which the LN1 lens converges (guides) the incident light 30. Each LN1 lens is positioned opposite a pixel 20 associated thereto, the lens LN1 being arranged so that its useful surface S2 is positioned on at least a portion of one or more of the sub-pixels 22 of the associated pixel.

The LN1 lenses thus focus the incident light 30 received so as to enhance the color contribution of at least one sub-pixel 22 of the associated pixel 20, in the corresponding region of the color image generated through said lens, relative to the respective color contribution of each other sub-pixel 22 of the associated pixel. This modulation of the colorimetric contributions of the sub-pixels is described in more detail below with reference to FIGS. 6, 7 and 8.

The set of pixels 20 used in the example considered here is illustrated in FIG. 6. The pixels 20 are rectangular and composed of 4 sub-pixels 22a-22d themselves of rectangular shape. Each sub-pixel 22a-22d of the same pixel 20 has a unique color denoted respectively CLa-CLd. The sub-pixels 22 are uniformly distributed so that the colors CLa to CLd repeat periodically in the substrate 12. This rectangular configuration has the advantage of being relatively simple to achieve by color printing. According to one variant, thin white lines, for example less than 30 μm wide, are formed between the different color sub-pixels CLa, CLb, CLc and CLd.

According to one variant, one of the colors CLa, CLb, CLc and CLd is white.

Figure 7 shows in dotted line the useful area S2 defined by each lens LN1 on an associated pixel 20. In this example, the outline of the useful surfaces S2 corresponds to the sub-pixels 22c of color CLc. In a variant, the useful surface S2 is smaller than the corresponding sub-pixel so that the observed color does not vary when the observer looks at the surface of the lenses with a not exactly perpendicular angle (oblique observation).

FIG. 7 further represents, in superposition, the contour of the incidence surfaces (or lens surfaces) S 1 defining the location of the lenses LN 1 located opposite the pixels 20. In this example, each lens LN 1 is positioned in correspondence with the subpixels 22b, 22c and 22d of the associated pixel 20 and further covers a portion of the sub-pixel 22a of the associated pixel 20 (and a portion of the sub-pixel 22a of a neighboring pixel).

Also, in this particular example, each lens LN1 focuses the incident light 30 received (FIG. 4) on the sub-pixel 22c of the associated pixel 20, which has the effect of greatly accentuating the color contribution of the sub-pixel 22c in the corresponding region of the color image 6 (FIG. 1) generated through said LN1 lens, with respect to the respective color contribution of each other sub-pixel 22a, 22b and 22d of the associated pixel.

FIG. 8 represents the visual rendering, in regions R1 and R2, of the color image 6 observable by an observer OB (FIG. 4). As shown, the regions R1 and R2 are observable in the single color CLc due to the focusing of the incident light 30 by the lenses LN1 on the subpixels 22c.

By preferentially converging the incident light 30 onto some appropriately selected subpixels 22, it is thus possible to generate (or reveal) the desired color image 6. The lenses LN1 make it possible to select certain colors so as to form the final color image 6 by the interaction between the lens array LN1 and the set of pixels 20.

The color image 6 is formed by the combination of the LN1 lens array and the set of pixels 20 facing each other. Without the addition of the lenses LN1 to judiciously orient the incident light, the set of pixels 20 constitutes only one blank arrangement of color pixels since this set is devoid of the information characterizing the color image 6. It is the LN1 lens array that is configured, according to the chosen subpixel arrangement 22, to customize the visual appearance of the pixels 20 and thereby generate the final color image 6.

In the example considered here, the LN1 lenses each converge the incident light 30 to a single sub-pixel 22c of the same color CLc predetermined in the associated pixel 20, so as to show as color only the color CLc in a monochrome region (for example the background image 10) of the color image 6 (FIG. 1).

In a particular example, the smallest dimension of the LN1 lenses is less than or equal to 350 × 10 ⁶ m, ie 350 μm. In the case where the lenses LN1 are of cylindrical shape as represented in FIGS. 5-7, the smallest dimension of the lenses corresponds to the smallest side of the rectangle formed by the intersection of the cylinder portion of the lens with the plane on which she rests.

In a particular example, the arrangement of pixels 20 in the document 2 shown in FIGS. 4 to 8 is such that the initial color contribution of a sub-pixel 22 in its pixel 20 (i.e. intrinsic color of this sub-pixel 22, regardless of the lenses) is 25% and its contribution in the corresponding region (corresponding to the incident surface of the associated lens) of the final color image 6 is 100% .

The invention therefore advantageously makes it possible to generate a highly saturated color zone in the desired CLc color or even desaturated in the particular case where the target sub-pixel is white. Each lens LN1 masks the colors CLa, CLb, CLd from the other subpixels 22a, 22b and 22d of the associated pixel 20 in the corresponding region (R1 and R2) of the color image 10 generated through the lens. This masking is preferentially visible when the map is not inclined relative to the observer OB, that is to say, when one places oneself in a normal observation at the plane in which the pixels extend. The observation may not be constrained to an exact normality if the convergence of the lenses makes it possible to have a smaller useful surface centered on the subpixel concerned.

The invention thus makes it possible to form monochrome image areas of good quality, while ensuring a high level of complexity ensuring the security of the image vis-à-vis screw fraud. The invention makes it possible, for example, to produce a highly saturated or desaturated background image 10 (FIG. 1) in a given color, such as white, for example.

By inspecting the color image 6, it is possible thanks to the invention to easily detect a fraud when the image has been forged or reproduced illicitly. The configuration of the lenses is adapted only to the set of pixels 20 that has been printed and is therefore frozen in the image. In addition, this level of complexity and security of the image achieved through the invention is not detrimental to the quality of the visual rendering of the image. This does not prevent in particular the formation of color images comprising areas requiring significant contrast as in the case of a face vis-à-vis a background image. The invention makes it possible to form quality color images from a large gamut of color.

As a variant, it is possible to configure the lenses LN1 so that they each focus the incident light 30 on a single sub-pixel 22 of the associated pixel 20, these sub-pixels 22 not being necessarily always of the same color. Various color combinations are thus possible.

Furthermore, in the example shown in FIGS. 4-8, the lenses LN1 each focus the incident light on a single sub-pixel 22 of an associated pixel 20 facing each other. However, other embodiments are possible in which the lenses focus the incident light on at least two sub-pixels of the same pixel, as described below.

A second particular implementation of the device 2, as described above with reference to FIGS. 1, 2 and 3A-3D, is now described with reference to FIGS. 9 to 13.

The device 2 here comprises a substrate 12 in which is disposed a set of pixels, denoted 40, each pixel comprising a plurality of sub-pixels denoted here 42. A lens array, denoted here LN2, is disposed opposite the set of pixels 40 so as to generate the color image 6 (FIG. 1) by focusing an incident light 30 on some of the sub-pixels 42.

More particularly, the substrate 12 comprises an upper layer 12a disposed on a lower layer 12b, identical to the embodiment of FIGS. 4- 5. The set of pixels 40 is printed on the upper face of the lower layer 12b or on the lower face of the upper layer 12a, so as to be at the interface between the layers 12a and 12b, inside the substrate 12. According to one variant, the set of pixels 40 is printed on the upper face of the substrate 12.

As already described in the preceding examples, each pixel 40 forms a pattern comprising an arrangement of sub-pixels 22 of at least two different colors. The sub-pixels 22 may be made according to any color printing technique that the skilled person can choose according to the particular case. The set of pixels used in this example is described later with reference to FIG. 11.

In this example, lenses LN2 are formed in a layer 14 having surface deformations defining the lenses, in a manner identical to the embodiment of FIGS. 4-5. This layer 14 covers the substrate 12, the layer 14 and the substrate 12 being for example laminated together. The layer 14 may be made of silica glass, polycarbonate or any other transparent material. According to a variant, the LN2 lens array is formed directly in the substrate 12, which then comprises surface deformations defining the lenses, no additional layer 14 being then necessary.

As illustrated in FIG. 9-10, the lenses LN2 here are of spheroidal shape and together form a lens matrix LN2, composed for example of rows and orthogonal columns. It is however possible to arrange LN2 lenses in a non-orthogonal arrangement, or even non-uniformly, depending on the visual effect that is sought.

The LN2 lenses are in this example convergent lenses. The array (or arrangement) of lenses LN2 is arranged facing the set of pixels 40 so as to generate the color image 6 by focusing an incident light 30 through the lenses LN2 on at least a portion of the sub-lenses. pixels 42. Each LN2 lens is positioned, relative to an associated pixel 40 facing each other, to focus the incident light 30 on at least one of the sub-pixels 22 of the associated pixel 20 so as to modify (or modulate) the contribution of the respective colors of subpixels 22 of the associated pixel 20, in a region of the color image 6 generated through said lens LN2, with respect to the pattern intrinsically formed by the associated pixel 40 independently of said LN2 lens (ie without taking into account the modulation effect of said lens).

In other words, each lens LN2 is positioned (or configured), relative to an associated pixel 40 located opposite, to focus the incident light 30 on at least one of the sub-pixels 22 of the associated pixel 20 so to modify (or modulate) the contribution of the respective color of at least one subpixel 22 of the associated pixel 20, in a corresponding region of the color image 6 generated through said lens LN2, with respect to the respective color contribution of each other subpixel 22 of said associated pixel.

As such, each lens can be uniquely shifted with respect to the position of the pixels 20 according to the perfectly regular organization presented by way of example in FIG.

As already explained, the substrate 12 and the layer 14 are transparent in order to allow at least part of the incident light 30 to pass through the lenses LN2 until reaching the color pixels 40. The pixels 40, and more particularly their sub-pixels 42, comprise in this example a reflective surface 23, positioned beneath the sub-pixels 42, to reflect (at least partially) the incident light 30 received through the LN2 lens array. The layers 12 and 14 are for example polycarbonate.

As shown in FIG. 9, and as already explained with reference to FIG. 4, each lens LN2 has an incidence surface SI, able to receive an incident light 30, and further defines, on the surface of the set of pixels 40, a useful surface S2 on which the lens LN2 converges the incident light 30. Each lens LN2 is positioned opposite a pixel 40 associated therewith, the lens LIM2 being arranged so that its useful surface S2 is positioned on at least a portion of two subpixels 42 of the associated pixel 40.

The lenses LN2 thus focus incident light 30 received so as to accentuate the color contribution of at least two subpixels 42 of the associated pixel 20, in the corresponding region of the color image generated through said lens, relative to the respective color contribution of each other subpixel 42 of the associated pixel 40. This modulation of the colorimetric contributions of the sub-pixels is described in more detail below with reference to FIGS. 11 and 12.

The set of pixels 40 used in the example considered here is illustrated in FIG. 11. The pixels 40 are here composed of 4 subpixels 42a-42d of hexagonal shape. Each sub-pixel 42a-42d of the same pixel 40 has a unique color denoted respectively CLa-CLd in the pixel in question. The sub-pixels 42 are uniformly distributed so that the colors CLa to CLd repeat periodically in the substrate 12. This hexagonal configuration offers great flexibility in the range colors that can be produced. Other exemplary embodiments are possible with only 3 subpixels 42 of distinct color in each pixel 40 (see, for example, the variation shown in FIG. 3B).

FIG. 11 represents in dashed lines the useful area S2 defined by each lens LN2 on an associated pixel 40. In this example, the useful area S2 of each lens LN2 defines a zone straddling two sub-pixels 42 of the associated pixel 40 situated opposite. According to other variants, it is possible to configure lenses so that it focuses the incident light on 3 or more subpixels.

The incidence surfaces SI define in particular the location of the lenses LN2 located opposite the pixels 40. These incidence surfaces SI are dependent on the shape, the position, and more generally the configuration of the lenses LN2. In this example, each LN2 lens is positioned in correspondence with a portion of certain sub-pixels 42 of an associated pixel 40 and may, if appropriate, also cover a portion of one or more neighboring pixels 40.

More particularly, here we consider the case of two LN2 lenses respectively defining bearing surfaces S11 and S12, and useful surfaces S21 and S22.

Also, in this particular example, each lens LN2 focuses the incident light 30 received (FIG. 9) on two sub-pixels 42 of the associated pixel 40, which has the effect of greatly accentuating the color contribution of these sub-pixels, in the corresponding region of the color image 6 (FIG. 1), corresponding to the incident surface S11, S12, generated through said lens LN2, with respect to the respective color contribution of each other sub-pixel 42 of the pixel 20 associate.

Thus, in the example shown in FIG. 11, the area defined by the useful area S21 is such that the colors CLc and CLd of the respective sub-pixels 42c and 42d are accentuated with respect to the colors of the other sub-pixels 42 of the pixel 40 considered. Likewise, the area defined by the effective area S22 is such that the colors CLa and CLb of the respective sub-pixels 42a and 42b are accentuated with respect to the colors of the other sub-pixels 42 of the pixel 40 in question. By adapting the configuration of the LN2 lenses, it is possible to control the shape and the dimensions of the useful surfaces and thus to choose which colors are preferred in each region of the image 6, and in what proportions the colorimetric contributions of each sub-pixel 42 are modified.

FIG. 12 represents the visual rendering, in regions R1 and R2, of the color image 6 observable by an observer OB (FIG. 9). As represented, the regions R1 and R2, respectively corresponding to the incidence surfaces SU and S12 of two lenses LN2, are observable in hybrid colors CH and CL2 obtained by color mixtures coming from the sub-pixels on which the incident light 30 is focused.

Thus, the region RI has the hybrid color CL1 resulting from an addition of the weighted contributions of the colors CLc and CLd of sub-pixels 42c and 42d. Likewise, the region R2 has the hybrid color CL2 resulting from an addition of the weighted contributions of the colors CLa and CLb of sub-pixels 42a and 42b.

By preferentially converging the incident light 30 onto some appropriately selected subpixels 22, it is thus possible to generate (or reveal) the desired color image 6. The LN2 lenses make it possible to generate complex colors from the colors of the subpixels located opposite the lenses. It is possible to generate a hybrid color from 2, 3 or 4 distinct sub-pixels for example, according to the tiling used. As already explained, the color image 6 is formed by the combination of the LN2 lens array and the set of pixels 40 facing each other. Without the addition of LN2 lenses to judiciously orient the incident light, the set of pixels 40 is only a blank arrangement of color pixels to the extent that this set is devoid of the information characterizing the color image 6. It is the LN2 lens array that is configured, according to the chosen subpixel arrangement 42, to customize the visual appearance of the pixels 40 and thereby generate the final color image 6.

Note that different types of visual rendering can be obtained when a lens converges a light incident on at least two sub-pixels. In the example considered above, it is assumed that the regions R1 and R2 of the color image 6 (FIG. 12) as they appear to an observer OB are monochrome. In other words, these regions R1 and R2 appear as zones having a single uniformly distributed color, namely the respective hybrid colors CL1 and CL2 in this example. To do this, it is necessary that the dimensions of the lenses LN2 are sufficiently small with respect to the distance between the image and the observer so that the intrinsic separating power of the human eye can not discern the different primary colors constituting the colors. hybrids CL1 and CL2, respectively. When the combination of distinct colors is effected beyond the resolution power of the human eye, only the hybrid color resulting from the additions of the constituent colors is perceived by an observer. FIG. 13 represents an observer OB observing from a point I an image portion projected onto an LN2 lens. According to a particular embodiment, the smallest dimension D of the LN2 lenses is such that:

D <tau ( ^aiim / 2) '2L

where alim corresponds to the maximum limit angle of observation beyond which the human eye can discern two distinct colors, and L is the distance between the observation point I and the image. It should be noted that the smallest dimension of D lies in a plane in which the lens LN2 considered extends.

In order for a human eye not to be able to distinguish separately the different colors of the sub-pixels 40 in an image zone defined by a useful surface SI (FIG. 11), it is necessary for the observation angle α to be such that: a <feed

We consider here that alim = the (minute) = 3.10 · ⁴ rad.

In a particular example, assuming that the observation distance L = 0.5 m (meter), it is necessary that the smallest dimension D of the LN2 lenses is less than 150 × 10 ⁶ m, ie 150 μm. In the case where the lenses LN2 are of spheroidal shape, the smallest dimension D corresponds to the diameter of the circle formed by the intersection of the sphere portion of the lens with the plane on which it rests.

Note that in the embodiments described above, the lenses used are convergent, although other embodiments are possible. Thus, it is thus possible to apply the principle of the invention by using diverging lenses. For example, in document 2 shown in FIG. 2, the LN lens array may comprise at least one diverging lens configured to diverge incident light received by the lens so as to reduce the color contribution of at least one subpixel. 22 of the associated pixel 20, in the corresponding region of the color image 6 generated through said lens, with respect to the respective color contribution of each other sub-pixel 22 of said associated pixel.

FIG. 13 is a cross-sectional view of the document 2 according to a variant of the embodiment shown in FIG. 2. The document 2 differs from the implementation of FIG. 2 in that the lenses, here denoted LN3, are divergent so they do diverging the incident light on the sub-pixels 22 located in correspondence. It is thus possible to position the diverging lenses LI \ I3 in correspondence with certain sub-pixels 22 so as to reduce the color contribution of these sub-pixels in the regions of the color image 6 generated through these lenses. With reference to FIG. 11, an exemplary embodiment in which S21 and S22 define the incident lens surfaces LN3 diverging, and S11 and S22 define the useful surfaces of these lenses can be considered.

According to this variant, it is also possible to modify (modulate) the color contribution of certain sub-pixels relative to others in the rendering of the final color image 6, according to the principle of the invention.

Moreover, as already indicated, it is possible to confer contrast to a color image 6 (FIG. 1) generated according to the principle of the invention by adding opacifying elements (black or dark) opposite certain sub-pixels in order to create gray levels of the color image 6, as described below.

FIG. 15 shows a particular embodiment which differs from the embodiment of FIG. 2 in that the document 2 further comprises opaque (or opacifying) or non-reflecting zones (or volumes) 60 which may be dark, gray or black for example, located next to certain sub-pixels 22 so as to create gray levels in the final color image 6. To do this, the substrate 12 comprises for example a lasérisable transparent layer 65 (corresponding for example to the layer 12a shown in Figures 4 and 9). The term "lasérisable" layer is understood to mean a layer sensitive to laser radiation.

The lasérisable transparent layer 65 is arranged facing the set of pixels 20, this laserizable transparent layer being at least partially carbonized by a laser radiation LR1 so as to include regions 60 opacified locally opposite sub-pixels 20 to produce grayscale (or contrast) in the color image 6 generated through the LN lenses.

The opaque regions 60 partially or totally mask some of the subpixels 22 (a subset of the subpixels 22) thus forming the gray levels of the color image 6. These opaque regions may also partially or completely mask the lenses, thus making it possible to modulate, that is to say, vary, the brightness of composite colors created by the alignment of the lenses and the sub-pixels. By combining this technique of local opacification of a laserizable layer with the principle of the invention based on the use of lenses disposed opposite color sub-pixels, it is possible to obtain personalized color images of good quality. , while guaranteeing a high level of security against fraud due to the particularly advanced complexity of the image.

In the example shown in FIG. 15, the opaque zones 60 are formed so as to cover the whole of a corresponding sub-pixel 22, although other embodiments are possible where, for example, at least some of these opaque areas 60 only cover a portion of the corresponding sub-pixel 22. It is thus possible to very precisely adjust the gray levels in the image 6 (Figure 1).

In one particular example, one or more opaque regions 60 are configured to partially (or totally) mask a respective area of the visible pixel array 20 through an associated LN lens facing each other. The set of opaque regions 60 may form a general pattern such as an inscription (characters or symbols for example, such as a name or other) or an image. This general pattern is then visible through LN lenses.

The invention also relates to a method for generating (or forming) a color image according to the principle of the invention. This generation method may be configured to produce a device (or document) according to any of the embodiments described herein.

A method of generating (or forming) the document 2 shown in FIG. 2 is now described with reference to FIG.

The method comprises the following steps:

printing (step E2) a set of pixels 20 on or in the substrate 12, each pixel 20 forming a pattern having a subpixel arrangement 22 of at least two different colors; and

formation (step E4) of a lens array LN arranged facing the set of pixels 20 so as to generate the color image 6 (FIG. 1) by focusing or divergence of an incident light through the lenses on at At least a portion of the sub-pixels 22. In the example shown in FIG. 2, the lenses LN are convergent, so that they focus the incident light on the sub-pixels 22. The formation step E4 is such that each lens LN is positioned, relative to an associated pixel 20 facing each other, to focus (or, alternatively, to diverge) light incident on at least one of the sub-pixels 22 of said associated pixel 20 so as to modify the contribution of the respective colors of the sub-pixels of the associated pixel, in a region of the color image 6 generated through said lens, with respect to the pattern formed intrinsically by the pixel Associated independently of said lens 20.

In a particular example, the LN lens forming step E4 comprises: providing a first transparent layer; and

a projection on this first transparent layer of laser radiation (distinct from the radiation LR1 shown in FIG. 15) so as to form the lenses LN by surface deformation of said first transparent layer.

According to one variant, a projection of transparent material is made on the first transparent layer using a 3D printer head so as to form lenses on the surface of the first transparent layer.

This first transparent layer may correspond for example to the layer 14 shown in FIGS. 4 and 9, or to the substrate 12 itself in the case where the lenses LN are formed directly in the substrate.

For example, a C0 ₂ laser radiation can be used to create the surface deformations necessary to form the LN lens array.

In a particular example, during the training step E4, each lens LN (FIG. 2) is positioned relative to the associated pixel 20 independently of the positioning of the other lenses LN of the lens array. This positioning is for example carried out using a camera capable of identifying, for each lens, the position adapted vis-à-vis the associated pixel 20.

The method may further include a step E5 of forming opaque areas 60 to create gray levels in the final image, as already explained with reference to FIG.

As shown in FIG. 17, the method may further comprise, prior to the training step E4, a calculation step E6 if at least one of the LN lenses has to be configured to focus the incident light on at least two sub-pixels. , as shown for example in Figures 11 and 12, to create a hybrid color.

During this calculation step E6, carried out by a calculation unit such as a computer for example, the respective weights (or respective proportions, or coefficients) are determined. respective weight constituting a hybrid color that is desired to obtain and from these weights the positioning of the corresponding LN lens (and in particular the position of its useful surface) by relative to the subpixels of the associated pixel.

Thus, in a particular embodiment, at least one lens LN, called the first lens, of the lens array is a convergent lens configured to focus incident light received on at least two subpixels 42 of the associated pixel 40 (FIGS. so as to display in a corresponding region R1, R2 of the color image 6 a hybrid color CL1, CL2 resulting from a combination of the colors of said at least two sub-pixels, wherein said first lens LN is formed so that it has, in its smallest dimension, a smaller maximum dimension of 150 μm. The generation method then comprises a determination (E6) of respective weights assigned to each of said at least two sub-pixels 42, these weights representing respective contributions of each sub-pixel 42 in the color combination producing the hybrid color; the first lens being positioned relative to the associated pixel 40 in accordance with said respective weights assigned to said at least two sub pixels 42.

As already indicated, the method (FIG. 17) may furthermore comprise a step E5 for forming opaque zones 60 to create gray levels in the final image, as already explained with reference to FIG.

As indicated in the various exemplary embodiments envisaged above, numerous variants and adaptations are possible within the scope of the invention. In particular, those skilled in the art can consider many configurations of lenses. Similarly, many pixel arrangements are possible depending on the case.

The order in which the steps are carried out in FIGS. 16 and 17 can be adapted according to the particular case.

According to a particular embodiment, each lens of the document of the invention is associated with a single pixel. The image 6 (FIG. 1) is thus formed by n pair (s) lens / associated pixel, n being an integer greater than or equal to 1.

Those 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, the person skilled in the art may consider any adaptation or combination of the features and embodiments described above to meet a particular need.

Thus, it is possible to use, for example, diverging lenses in the embodiments of FIGS. 4 and 9 or else spheroidal lenses in the embodiment of FIG. 4 or cylindrical lenses in the embodiment of FIG. 9. Different tilings of pixels are possible in each of the embodiments described in this document. The different variants described with reference to each embodiment can be applied to the other embodiments.

Claims

A document (2) capable of generating a color image (6), comprising:

a set of pixels (20) printed on or in a substrate (2), each pixel forming a pattern comprising an arrangement of sub-pixels (22) of at least two different colors, each pixel (20) of said set of pixels being configured so that each sub-pixel has a unique color in said pixel; and

a lens array (LN) disposed opposite the set of pixels so as to generate the color image by focusing or diverging incident light through the lenses (LN) on at least a portion of the sub-pixels (22)

each lens (LN) being positioned, relative to an associated pixel (20) facing each other, to focus or diverge the incident light on at least one of the subpixels (22) of said associated pixel so as to modifying the contribution of the respective colors of the sub-pixels of the associated pixel, in a region of the color image (6) generated through said lens, with respect to the pattern intrinsically formed by the associated pixel (20) independently of said lens ( LN).

The document of claim 1, wherein each pixel (20) of said set of pixels forms an identical pattern of color subpixels (22).

The document of claim 1 or 2, wherein the set of pixels (20) is configured such that the subpixels are uniformly distributed on or in the substrate.

The document of any one of claims 1 to 3, wherein the probability density of the presence of each subpixel color is constant in the set of pixels.

The document according to any one of claims 1 to 4, wherein the lens array (LN) is formed from a layer having surface deformations defining the microlenses, said layer being the substrate or a layer laminated with the substrate.

The document according to any one of claims 1 to 5, wherein the subpixels (22) in the set of pixels comprise a reflecting surface (23) positioned under the subpixels for reflecting incident light through the network of lenses.

The document according to any one of claims 1 to 6, wherein at least one lens (LN1; LN2) in the lens array is a convergent lens configured to focus incident light received so as to enhance the color contribution of the lens. at least one subpixel (22) of the associated pixel, in the corresponding region of the color image generated through said lens, with respect to the respective color contribution of each other sub-pixel of said associated pixel.

The document of claim 7, wherein at least one lens in the lens array is a converging lens (LN1) configured to focus received incident light onto only one of the associated pixel subpixels so as to mask the color of the each other sub-pixel of said associated pixel in the corresponding region of the color image generated through said lens.

The document of claim 8, wherein, in a monochrome region of the color image, each lens of the lens array is a converging lens (LN1) configured to focus incident light received on a single sub-pixel of a same predetermined color in the associated pixel, so as to display as a single color the predetermined color in said monochrome region of the color image.

The document of claim 7, wherein at least a first lens (LN2) of the lens array is a converging lens configured to focus incident light received on at least two subpixels (22) of the associated pixel so as to cause appearing in a corresponding region of the color image a hybrid color resulting from a combination of the colors of said at least two sub-pixels (CL1, CL2), wherein said first lens has, in its smallest dimension, a smaller maximum dimension 150 pm.

The document according to any one of claims 1 to 10, wherein at least one lens of the lens array is a diverging lens configured to diverge incident light received by the lens so as to reduce the color contribution of at least a sub-pixel of the associated pixel, in the corresponding region of the color image generated through said lens, with respect to the respective color contribution of each other sub-pixel of said associated pixel.

The document of any one of claims 1 to 11, further comprising:

a laserizable transparent layer (65) disposed facing the set of pixels (20), said laserizable transparent layer being at least partially carbonized by laser radiation so as to include opacified regions locally opposite sub-pixels to produce grayscale in the color image generated through the lenses.

A method of generating a color image (6), comprising:

printing (E2) a set of pixels (20) on or in a substrate, each pixel forming a pattern comprising a subpixel arrangement (22) of at least two different colors, each pixel (20) of said set pixels being configured such that each subpixel (22) has a unique color in said pixel; and

- forming (E4) a lens array arranged opposite the set of pixels so as to generate the color image by focusing or diverging incident light through the lenses on at least a portion of the sub-pixels each lens being positioned, relative to an associated pixel located opposite, to focus or diverge the incident light on at least one of the sub pixels of said associated pixel so as to modify the contribution of the respective colors of the subpixels. -pixels of the associated pixel, in a region of the color image generated through said lens, with respect to the pattern intrinsically formed by the associated pixel independently of said lens.

The method of claim 13 comprising:

- providing a first transparent layer; and projecting on the first transparent layer a first laser radiation so as to form the lenses by deformation on the surface of said first transparent layer.

The method of claim 13 comprising:

- providing a first transparent layer; and

- Making on the first transparent layer of a projection of transparent material using a 3D printer head so as to form lenses on the surface of the first transparent layer.

The method according to any of claims 13 to 15, wherein, during the forming step, each lens is positioned relative to the associated pixel located opposite each other independently of the positioning of the other lenses of said lens array. .

The method of any one of claims 13 to 16, wherein at least a first lens of the lens array is a converging lens configured to focus the incident light received on at least two subpixels of the associated pixel so as to cause appearing in a corresponding region of the color image a hybrid color resulting from a combination of the colors of said at least two sub-pixels, wherein said first lens is formed so that it has, in its smallest dimension, a smaller maximum dimension of 150 μm.

The method of claim 17, comprising a determination (E2) of respective weights assigned to each of said at least two subpixels, said weights representing respective contributions of each subpixel in the color combination producing the hybrid color;

said first lens being configured relative to the associated pixel in accordance with said respective weights assigned to said at least two sub pixels.