Patent Grant
11007811
The invention relates to the field of the formation of color images and relates more particularly to a device or an object, such as a document for example, able to generate a customized 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, etc.
Various printing techniques have been developed over time to perform color prints. The production particularly of identity documents such as those mentioned above require the production of color images in a secure manner in order to limit the risks of tampering by malicious individuals. The manufacture of such documents, particularly at the identity image of the bearer, needs to be sufficiently complex to make reproduction or tampering by an unauthorized individual difficult.
Thus, in a known manner, some official documents for example include 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 (hologram, secure inks, etc.) have been developed but these are not always sufficient to prevent fraud, in particular in relation to the significant resources available to some counterfeiters today.
Furthermore, the color image formation techniques used today, in particular in secure identity documents, do not always allow obtaining a satisfactory visual rendering quality. Problems arise in particular when the image formation techniques used are limited in their ability to saturate some colors. In other words, the color gamut (ability to reproduce a range of colors) of the known color image formation 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, even white, area constituting the image background. It is not always possible to obtain sufficiently saturated colors on the facial area or on the background, so that this same face placed on a monochrome background for example, and not sufficiently clear, has a satisfactory contrast between this face and the background fully satisfactory for the observer.
There is now a need to securely form customized color images, for example in identity documents, such as those mentioned above in particular. A need exists particularly to allow flexible and secure customization of color images in documents or the like, so that, even if a document is illicitly obtained by an individual, the latter cannot customize the color image as he wishes without being detectable during a proper inspection.
Furthermore, no solution capable of offering an appropriate level of security and flexibility today allows obtaining a sufficient color gamut, particularly to obtain the shades of color necessary for the formation of some high-quality color images, in particular when image areas must have a highly saturated level in a given color or for example a very light identity image background, that is to say totally desaturated and bright.
The invention aims in particular at overcoming the drawbacks and shortcomings of the state of the art mentioned above.
To this end, the present invention relates to a document suitable to generate a color image, comprising:
each lens being positioned, relative to a facing associated pixel, 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.
The invention advantageously allows, thanks to the lenses, creating shades of colors so as to form a color image by the interaction between the array of lenses and the set of pixels. The color image is therefore formed by the combination of the array of lenses and the facing set of pixels. Without the addition of the lenses to judiciously orient the incident light, the set of pixels is only a blank arrangement of color pixels insofar as this set lacks the information characterizing the color image. It is the array of lenses that is configured, according to the chosen arrangement of sub-pixels, to customize the visual appearance of the pixels and thus generate, by juxtaposition of the visual appearances of the pixels, the final color image.
It is particularly possible to configure the lenses (shape, positioning, etc.) so as to select some colors among the different colors present in the set of pixels. Conversely, it is possible to mask or reduce the color contribution of some sub-pixels in the visual rendering of the final color image 6.
The invention in particular allows generating a color area highly saturated in the desired color or even desaturated in the particular case where the targeted sub-pixel is white in color.
The invention thus allows forming monochrome image areas of good quality, while ensuring a high level of complexity guaranteeing the security of the image against fraud. The invention allows, for example, producing a highly saturated or desaturated image background 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 tampered or illicitly reproduced. Furthermore, this level of complexity and security of the image achieved by the invention does not come at the expense of the quality of the visual rendering of the image. This does not prevent particularly the formation of color images comprising areas that require high contrast as in the case of a face facing an image background. The invention allows forming quality color images from a wide color gamut.
According to a particular embodiment, each pixel of said set of pixels forms an identical pattern of color sub-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 so that each sub-pixel has a single color in said pixel.
According to a particular embodiment, the array of lenses is formed from a layer including surface deformations defining the micro-lenses, 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 include a reflecting surface positioned under the sub-pixels to reflect the incident light through the array of lenses.
According to a particular embodiment, at least one lens in the array of lenses is a converging lens configured to focus the received incident light so as to enhance the color contribution of at least one 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.
According to a particular embodiment, at least one lens in the array of lenses is a converging lens configured to focus the received incident light on only one of the sub-pixels 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 array of lenses is a converging lens configured to focus the received incident light on a single sub-pixel of the same predetermined color in the associated pixel, so as to make appear as a single color the predetermined color in said monochrome region of the color image.
According to a particular embodiment, at least a first lens of the array of lenses is a converging lens configured to focus the received incident light on at least two sub-pixels of the associated pixel so as to make appear 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 has, in its smallest dimension, a smaller maximum dimension of 150 μm.
According to a particular embodiment, at least one lens of the array of lenses is a diverging lens configured to diverge a received incident light by the lens so as to reduce the color contribution of at least one 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.
According to a particular embodiment, the document further comprises:
a transparent laserable layer disposed opposite the set of pixels, said transparent laserable layer being at least partially carbonized by laser radiation so as to comprise locally opacified regions 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 relates to a method for generating a color image, comprising:
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 in a similar manner to the generation method of the invention.
According to a particular embodiment, the method comprises:
According to a particular embodiment, the method comprises:
According to a particular embodiment, during the formation step, each lens is positioned relative to the facing associated pixel independently of the positioning of the other lenses of said array of lenses.
According to a particular embodiment, at least a first lens of the array of lenses is a converging lens configured to focus the received incident light on at least two sub-pixels of the associated pixel so as to make appear 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 such that it has, in its smallest dimension, a smaller maximum dimension of 150 μm.
According to a particular embodiment, the method comprises determining respective weights assigned to each of said at least two sub-pixels, said weights representing respective contributions of each sub-pixel in the combination of the colors 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.
Other characteristics and advantages of the present invention will emerge from the description given below with reference to the appended drawings which illustrate exemplary embodiments thereof without limitation. In the figures:
As indicated above, the invention relates to the formation of color images and particularly relates to a device or an object, such as a document for example, able to generate a customized color image from color pixels.
The device within the meaning of the invention can take various forms and have various functions, one characteristic being that it is able to generate a color image according to the principle of the invention as disclosed in this document.
In the remainder of this document, exemplary implementations of the invention are described in the case of a document able to generate a color image according to the principle of the invention. This document can be any document, of the booklet or card type or the same, in particular an identity document such as for example: an identity card, a credit card, a passport, a driving license, a secure entry badge, etc.
It is however understood that the invention is not limited to the documents, but also applies to other objects configured to generate a color image according to the principle of the invention.
Likewise, the examples described below aim at generating an identity image. It is however understood that the considered image can be any image. Particularly, the image may be monochrome or multicolored (or include a monochrome or multicolored region).
The invention proposes to manufacture customized color images which are highly secure and which have good image quality. To do so, the invention, according to various embodiments, implements a device able to generate a color image, comprising: a set of pixels printed on or in a substrate, each pixel forming a pattern including an arrangement of sub-pixels of at least two different colors; and a array of lenses disposed opposite the set of pixels so as to generate the color image by focusing or diverging an incident light through the lenses on at least part of the sub-pixels.
Each lens can be positioned (or configured), relative to a facing pixel (called “associated pixel”), 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 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 a facing associated pixel, 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 allow creating shades of color so as to form (or generate) a color image by the interaction between the array of lenses and the set of pixels. More particularly, each array of lenses allows creating shades of color, so as to form a single color image, specific to each array and distinct from the pattern of the pixels. The invention also relates to a corresponding method for manufacturing (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.
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.
A set of pixels 20, also called tiling (or tiling of pixels), is printed in the substrate 12, each pixel 20 forming a pattern including an arrangement of sub-pixels 22 of at least two different colors. Examples of patterns of sub-pixels, whose possible configurations are multiple, are described later in particular with reference to
The substrate 12 is here transparent in order to allow an incident light to pass at least partially through the lenses LN so as to reach the color pixels 20. The pixels 20, and more particularly their sub-pixels 22, include in this example a reflecting surface 23 located under the sub-pixels to reflect (at least partially) the received incident light through the array of lenses LN. This reflecting surface is for example a white surface.
As represented in
More particularly, each lens LN is positioned, relative to a facing pixel 20, called “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 sub-pixels 22 of the associated pixel 20, in a region of the corresponding color image 6 (that is to say generated through this lens LN), with respect to the pattern intrinsically formed by the associated pixel 20 independently of said lens LN.
In other words, the lenses LN are configured so as to converge or diverge the incident light on some sub-pixels 22 so as to the make the color image 6 appear (reveal it), from the set of pixels 20, while favoring the color contribution of some sub-pixels over others.
The LN lenses thus allow creating shades of colors so as to form a color image 6 by the optical interaction between the array of lenses LN and the set of pixels 20. The color image 6 is therefore formed by the combination of the array of lenses LN and the facing set of pixels 20. Without the addition of the lenses LN to judiciously orient the incident light, the set of pixels 20 is only a blank arrangement of color pixels insofar as this set lacks the information characterizing the color image 6. It is the array of lenses LN that is configured, according to the chosen arrangement of sub-pixels 22, to customize the visual appearance of the pixels 20 and thus generate, by juxtaposition of the visual appearances of the pixels, the final color image 6.
How the lenses can guide the incident light to modify the color contribution of some sub-pixels 22 with respect to other sub-pixels in the final color image 6 is described in more detail later.
It is particularly possible to configure the lenses LN (shape, positioning, etc.) so as to select some colors among the various colors present in the set of pixels 20. Conversely, it is possible to mask or reduce the color contribution of some sub-pixels 22 in the visual rendering of the final color image 6.
As described below, it is possible to further add opacifying elements (black or dark, for example) opposite some sub-pixels 22 in order to create levels of gray of the resulting color image 6, and thus generate contrast in the color image after the alignment of the lenses on the appropriate sub-pixels has selected an appropriate tint.
The lenses LN disposed opposite the set of pixels 20 can have various shapes, dimensions and configurations (magnifying power, converging or diverging . . . ). Depending on the case, lenses LN can for example be spheroidal or cylindrical, for example.
Furthermore, the set of pixels 20 within the meaning of the invention can be in different shapes, configurations, dimensions, etc. Particularly, each pixel of the set of pixels 20 may form an identical pattern of color sub-pixels 22. In this case, the set of pixels consists of a single pattern of sub-pixels which is repeated a plurality of times. This arrangement of sub-pixels is said to be “blank” arrangement in the sense that it does not intrinsically form (that is to say without the addition of the lenses LN and/or of the opacifying elements) the color image 6.
According to a particular example, each pixel 20 has an identical pattern of sub-pixels 22 in the same orientation through the set of pixels 20. It is thus possible to evenly distribute the color sub-pixels in the set of pixels (as illustrated for example in
According to a particular example, each pixel 20 has an identical pattern of sub-pixels 22, variations in orientation of this pattern being however made between some pixels with respect to each other, through the set of pixels 20. In other words, the same pattern of color sub-pixels 22 is then in all the pixels 20 of said set but following at least two different orientations (by applying for example rotations of 90° and/or 180° on the same pattern which is repeated through the set of pixels 20).
The set of pixels 20 can be configured so that the sub-pixels are uniformly distributed on or in the substrate 12. In other words, the set of pixels can form a regular or periodic arrangement of pixels 22, forming identical or non-identical patterns of sub-pixels depending on the case.
The set of pixels 20 can form a matrix of pixels, consisting of rows and columns of sub-pixels 22. These rows and columns can be rectilinear and optionally orthogonal to each other.
According to a particular example, each pixel 20 forms a pattern composing an arrangement of sub-pixels 22 of at least two different colors, the probability density of the presence of each sub-pixel color being constant in the pixels 20 of the arrangement of pixels. In other words, if pixels 20 of n color sub-pixels are considered (n being an integer), the surface proportion of each color (formed by one or several sub-pixel(s)) is identical in each pixel 20 of the set of pixels. By way of example, the following densities can be found in each pixel 20: 30% yellow, 20% magenta, 40% cyan and 10% white). In this particular example, each pixel 20 can thus have an identical pattern of color sub-pixels 22 in the same orientation through the arrangement of pixels 20 or, optionally, in an orientation that varies in the arrangement of pixels 20 (according to random variations or according to regular variations or other variations).
Particularly, in more complex examples, a random arrangement of the pixels 20 is possible. It is in particular possible to organize the distribution of the sub-pixels 22 randomly but so that the probability density of the presence of each sub-pixel color is constant in the pixels 20 of the set of pixels. In this case, it is necessary, in a given area of the arrangement of pixels 20, to be able to select by means of the lenses LN the desired color(s) even if the corresponding sub-pixels are not exactly at their assumed theoretical coordinates.
According to a particular example, each pixel 20 of the set of pixels is configured so that each of the sub-pixels 22 has a single color in said pixel 20. A pixel 20 can thus be composed of a plurality of sub-pixels 22, all of distinct color. Alternatively, it is possible to define the pixels 20 so that they include at least two sub-pixels 22 of the same color among all their sub-pixels (for example, 2 sub-pixels in each primary color), provided that each pixel comprises at least two sub-pixels 22 of different color.
The colors of the sub-pixels 22 may vary depending on the case and may constitute primary colors from which the color image 6 is generated in combination with the array of lenses LN. In a particular example, each pixel 20 comprises sub-pixels 22 in the primary red/green/blue (RGB) colors, optionally with white, or in the primary yellow/magenta/cyan colors, optionally with white. A white area can optionally be arranged in the arrangement of pixels 22 between the rows and columns of sub-pixels 22 to avoid the color overlay.
Particular examples of tiling (arrangement) of pixels 20, which can be implemented in a device of the invention such as document 2 represented in
Examples of particular implementation of the device 2 described above with reference to
The device 2 comprises in this example a substrate 12 in which a set of pixels 20 is disposed, each pixel comprising a plurality of sub-pixels 22. An array of lenses, noted here LN1, is disposed opposite the set of pixels 20 so as to generate the color image 6 (
More particularly, as illustrated in
As already indicated, each pixel 20 forms a pattern including an arrangement of sub-pixels 22 of at least two different colors. The sub-pixels 22 can be made using any color printing technique that those skilled in the art can choose depending on the case. The set of pixels 20 used in this example is described later with reference to
In this example, lenses LN1 are formed in a layer 14 including 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 can be for example made of silica glass or polycarbonate, or even any transparent material with a density different from that of the air so that there is refraction of light and therefore a lens effect. According to one variant, the array of lenses LN1 is formed directly in the substrate 12 which then includes surface deformations defining the lenses, no additional layer 14 then being necessary.
As illustrated in
The lenses LN1 are in this example converging lenses. The array (or arrangement) of lenses LN1 is disposed opposite 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 part of the sub-pixels. 22. Each lens LN1 is positioned, relative to a facing associated pixel 20, 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 sub-pixels 22 of the associated pixel 20, in a region of the color image 6 generated through said lens LN1, with respect to the pattern intrinsically formed by the associated pixel 20 independently of said lens LN1.
In this document, it is meant by “pattern intrinsically formed 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 facing lens.
As already explained, the substrate 12 and the layer 14 are transparent in order to allow the incident light to pass least partially through the lenses LN1 until reaching the color pixels 20. The pixels 20, and more particularly their sub-pixels 22, include in this example a reflecting surface 23, located under the sub-pixels, to reflect (at least partially) the received incident light 30 through the array of lenses LN1. The layers 12 and 14 are for example made of polycarbonate. The reflecting layer 23 can be a white surface located under the pixels.
As represented in
The lenses LN1 thus focus the received incident light 30 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, with respect to the respective color contribution of each other sub-pixel 22 of the associated pixel 20. This modulation of the colorimetric contributions of the sub-pixels is described in more detail below with reference to
The set of pixels 20 used in the example considered here is illustrated in
According to one variant, fine white lines, for example less than 30 μm in width, are arranged between the different color sub-pixels CLa, CLb, CLc and CLd.
According to one variant, one among the colors CLa, CLb, CLc and CLd is white.
Also, in this particular example, each lens LN1 focuses the received incident light 30 (
By preferentially converging the incident light 30 on some appropriately chosen sub-pixels 22, it is thus possible to generate (or reveal) the desired color image 6. The lenses LN1 allow selecting some colors so as to form the final color image 6 by the interaction between the array of lenses LN1 and the set of pixels 20.
The color image 6 is therefore formed by the combination of the array of lenses LN1 and the facing set of pixels 20. Without the addition of the lenses LN1 to judiciously orient the incident light, the set of pixels 20 is only a blank arrangement of color pixels insofar as this set lacks the information characterizing the color image 6. It is the array of lenses LN1 that is configured, according to the chosen arrangement of sub-pixels 22, to customize the visual appearance of the pixels 20 and thus generate the final color image 6.
In the example considered here, the lenses LN1 each converge the incident light 30 towards a single sub-pixel 22c of the same predetermined color CLc in the associated pixel 20, so as to make appear as a single color the color CLc in a monochrome region (for example image background 10) of the color image 6 (
According to a particular example, the smallest dimension of the lenses LN1 is less than or equal to 350·10−6 m, i.e. 350 μm. In the case where the lenses LN1 are of cylindrical shape as represented in
According to a particular example, the arrangement of pixels 20 in document 2 represented in
The invention therefore allows advantageously generating a color area highly saturated in the desired color CLc or even desaturated in the particular case where the targeted sub-pixel is white in color. Each lens LN1 masks the colors CLa, CLb, CLd of the other sub-pixels 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 tilted relative to the observer OB, that is to say, when we are in an observation normal to the plane in which the pixels extend. The observation may not be constrained to an exact normality if the convergence of the lenses allows having a smaller useful surface and centered on the targeted sub-pixel.
The invention thus allows forming monochrome image areas of good quality, while ensuring a high level of complexity guaranteeing the security of the image against fraud. The invention allows, for example, making an image background 10 (
By inspecting the color image 6, it is possible thanks to the invention to easily detect fraud when the image has been tampered or illegally reproduced. The configuration of the lenses is only adapted to the set of pixels 20 that has been printed and is therefore fixed in the image. Furthermore, this level of complexity and security of the image achieved thanks to the invention does not come at the expense of the quality of the visual rendering of the image. This does not prevent particularly the formation of color images comprising areas requiring high contrast as in the case of a face facing an image background. The invention allows forming quality color images from a large color gamut.
Alternatively, 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 always necessarily of the same color. Various associations of colors are thus possible.
Furthermore, in the example represented in
A second particular implementation of the device 2, as described above with reference to
The device 2 here comprises a substrate 12 in which a set of pixels noted 40 is disposed, each pixel comprising a plurality of sub-pixels noted here 42. An array of lenses, noted here LN2, is disposed opposite the set of pixels 40 so as to generate the color image 6 (
More particularly, the substrate 12 comprises an upper layer 12a disposed on a lower layer 12b, in a manner identical to the embodiment of
As already described in the previous examples, each pixel 40 forms a pattern including an arrangement of sub-pixels 22 of at least two different colors. The sub-pixels 22 can be made based on any color printing technique that those skilled in the art can choose depending on the case. The set of pixels 20 used in this example is described later with reference to
In this example, lenses LN2 are formed in a layer 14 including surface deformations defining the lenses, in an identical manner to the embodiment of
As illustrated in
The LN2 lenses are in this example converging lenses. The array (or arrangement) of lenses LN2 is disposed opposite 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 part of the sub-pixels 42. Each lens LN2 is positioned, relative to a facing associated pixel 40, 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 sub-pixels 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 lens LN2 (that is to say without taking into account the modulation effect of said lens).
In other words, each lens LN2 is positioned (or configured), relative to a facing associated pixel 40, 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 color of at least one sub-pixel 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 sub-pixel 22 of said associated pixel 20.
As such, each lens can be shifted in a unique way with respect to the position of the pixels 20 according to the perfectly regular organization presented by way of example in
As already explained, the substrate 12 and the layer 14 are transparent in order to allow the incident light 30 to pass at least partially through the lenses LN2 until reaching the color pixels 40. The pixels 40, and more particularly their sub-pixels 42, include in this example a reflecting surface 23, positioned under the sub-pixels 42, to reflect (at least partially) the received incident light 30 through the array of lenses LN2. The layers 12 and 14 are for example made of polycarbonate.
As represented in
The lenses LN2 thus focus the received incident light 30 so as to enhance the color contribution of at least two sub-pixels 42 of the associated pixel 20, in the corresponding region of the color image generated through said lens, with respect to the respective color contribution of each other sub-pixel 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
The set of pixels 40 used in the example considered here is illustrated in
The incidence surfaces S1 define particularly the location of the lenses LN2 located opposite the pixels 40. These incidence surfaces S1 are dependent on the shape, the position, and more generally the configuration of the lenses LN2. In this example, each lens LN2 is positioned in correspondence with a part of some sub-pixels 42 of an associated pixel 40 and can, if necessary, also cover part of one or several neighboring pixel(s) 40.
More particularly, the case of two lenses LN2 defining respectively incidence surfaces S11 and S12, and useful surfaces S21 and S22 are considered here.
Also, in this particular example, each lens LN2 focuses the received incident light 30 (
Thus, in the example represented in
Thus, region R1 presents 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 presents 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 preferably converging the incident light 30 on some sub-pixels 22 chosen appropriately, it is thus possible to generate (or reveal) the desired color image 6. The lenses LN2 allow generating complex colors from the colors of the sub-pixels located opposite the lenses. It is possible to generate a hybrid color from 2, 3 or 4 distinct sub-pixels for example, depending on the tiling used. As already explained, the color image 6 is therefore formed by the combination of the array of lenses LN2 and the facing set of pixels 40. Without the addition of the lenses LN2 to judiciously orient the incident light, the set of pixels 40 is only a blank arrangement of color pixels insofar as this set lacks the information characterizing the color image 6. It is the array of lenses LN2 that is configured, according to the arrangement of sub-pixels 42 chosen, to customize the visual appearance of the pixels 40 and thus generate the final color image 6.
It is noted that different types of visual rendering can be obtained when a lens converges an incident light 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 (
D<tan(αlim/2)·2L
where αlim corresponds to the maximum limit angle of observation beyond which the human eye cannot distinguish two distinct colors, and L is the distance between the point of observation I and the image. Note that the smallest dimension of D is comprised in a plane in which the considered lens LN2 extends.
So that a human eye cannot separately distinguish the different colors of the sub-pixels 40 in an image area defined by a useful surface S1 (
α<αlim
It is considered here that αlim=1′ (minute)=3.10−4 rad.
According to a particular example, assuming that the observation distance L=0.5 m (meter), it is necessary that the smallest dimension D of the lenses LN2 is less than 150.10−6 m, or 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.
It will be noted that in the exemplary embodiments described above, the lenses used are converging, 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 represented in
According to this variant, it is also possible to modify (modulate) the color contribution of some sub-pixels with respect 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 impart contrast to a color image 6 (
The transparent laserable layer 65 is disposed opposite the set of pixels 20, this transparent laserable layer being at least partially carbonized by a laser radiation LR1 so as to comprise regions 60 opacified locally opposite sub-pixels 20 to produce gray levels (or contrast) in the color image 6 generated through the lenses LN.
The opaque regions 60 partially or totally mask some of the sub-pixels 22 (a subset of the sub-pixels 22) thus forming the gray levels of the color image 6. These opaque regions can also partially or totally mask the lenses, thus making it possible to modulate, that is to say vary, the luminosity of compound colors, created by the alignment of the lenses and the sub-pixels.
By combining this technique of local opacification of a laserable layer with the principle of the invention based on the use of lenses disposed opposite color sub-pixels, it is possible to obtain customized 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 represented in
According to a particular example, one or several opaque region(s) 60 are configured so as to partially (or even totally) mask a respective area of the arrangement of pixels 20 visible through a facing associated lens LN. The set of the opaque regions 60 can form a general pattern such as an inscription (for example characters or symbols, such as a name or the like) or an image. This general pattern is then visible through the lenses LN.
The invention also relates to a method for generating (or forming) a color image according to the principle of the invention. This generation method can be configured to produce a device (or a document) according to any one of the embodiments described in this document.
A method for generating (or forming) the document 2 represented in
The method comprises the following steps:
The formation step E4 is such that each lens LN is positioned, relative to a facing associated pixel 20, to focus (or, alternatively, to diverge) the incident light 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 intrinsically formed by the associated pixel 20 independently of said lens 20.
In a particular example, step E4 of forming the lenses LN comprises:
According to one variant, a projection of transparent material is made on the first transparent layer using a printer head 3D so as to form lenses on the surface of the first transparent layer.
This first transparent layer can correspond, for example, to the layer 14 represented in
For example, CO2-type laser radiation can for example be used to create the surface deformations necessary to form the array of lenses LN.
According to a particular example, during the formation step E4, each lens LN (
The method may further comprise a step E5 of forming opaque areas 60 to create gray levels in the final image, as already explained with reference to
As represented in
During this calculation step E6, carried out by a calculation unit such as a computer for example, the respective weights (or respective proportions or respective weighting coefficients) of each color constituting a hybrid color desired to be obtained are determined and the positioning of the corresponding lens LN (and particularly the position of its useful surface) with respect to the sub-pixels of the associated pixel is determined from these weights.
Thus, in a particular mode, at least one lens LN, called first lens, of the array of lenses is a converging lens configured to focus the received incident light on at least two sub-pixels 42 of the associated pixel 40 (
As already indicated, the method (
As indicated in the various exemplary embodiments envisaged above, many variants and adaptations are possible within the framework of the invention. Particularly, those skilled in the art can envisage many configurations of the lenses. Likewise, many arrangements of pixels are possible depending on the case.
The order in which the steps are carried out in
According to a particular embodiment, each lens of the document of the invention is associated with a single pixel. The image 6 (
Those skilled in the art will understand that the embodiments and variants described above constitute only non-limiting examples of implementation of the invention. Particularly, those skilled in the art will be able to envisage any adaptation or combination among the characteristics and embodiments described above in order to meet a very specific need.
Thus, it is possible to use, for example, diverging lenses in the embodiments of
| Number | Date | Country | Kind |
|---|---|---|---|
| 18 52273 | Mar 2018 | FR | national |
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/FR2019/050569 | 3/14/2019 | WO | 00 |
| Publishing Document | Publishing Date | Country | Kind |
|---|---|---|---|
| WO2019/175514 | 9/19/2019 | WO | A |
| Number | Name | Date | Kind |
|---|---|---|---|
| 20140028775 | Lazzari | Jan 2014 | A1 |
| 20190033608 | Zhang | Jan 2019 | A1 |
| 20190152250 | Berthe et al. | May 2019 | A1 |
| Number | Date | Country |
|---|---|---|
| 2727742 | May 2014 | EP |
| 2553104 | Feb 2018 | GB |
| 2005052650 | Jun 2005 | WO |
| 2005106601 | Nov 2005 | WO |
| 2015178894 | Nov 2015 | WO |
| 2016097608 | Jun 2016 | WO |
| 2017162006 | Sep 2017 | WO |
| Entry |
|---|
| English language abstract of EP2727742. |
| Number | Date | Country | |
|---|---|---|---|
| 20210016593 A1 | Jan 2021 | US |
