EP3003730B1 - Arrangement and method for producing a colour image - Google Patents

Description

The present invention relates to an arrangement for producing a color image and a method for producing a color image. Said arrangement and said method are particularly adapted to the realization of a security device, allowing for example to personalize an identity document by affixing a photo ID of the wearer.

In the field of security devices, it is known to place a security device on an identity document in order to authenticate, personalize or make it more difficult to modify or reproduce the latter. A photo ID of the holder of the identity document is a typical example of such personalization.

It is known to make such a safety device, comprising an image, by laser carbonization. Laser carbonization selectively blackens a material provided for this purpose, including under at least one layer of transparent material. The carbonization laser, performing a carbonization, thus makes possible the realization of a monochrome image. The modulation of the laser amplitude makes it possible to reach a good resolution of gray levels.

It is still known to produce a color image by means of a laser carbonization process. The principle consists in arranging a matrix of pixels, each pixel comprising sub-pixels, advantageously a sub-pixel per elementary color chosen from a set of basic elementary colors such as red, green, blue, under a layer that can be carbonized by laser. It is then possible to carry out a color image by selectively masking by blackening obtained by laser carbonization, for each pixel, all or part of one or more sub-pixels, so as to express for said pixel a residual color, resulting from elementary colors of unmasked subpixels.

The document WO 2011/124774 describes a method of personalization of embedded latent images and the document produced. The document EP 1 918 123 discloses a data carrier in the form of a card and its method of manufacture.

The present invention provides an alternative method, using a different technology from laser carbonization.

The subject of the invention is a method for producing a color image in a substantially surface-dominant main support medium, said support comprising an arrangement of pixels, each pixel comprising sub-pixels of elementary color, said method comprising a step perforation of certain sub-pixels performing a selective destruction, partial or total, of said sub-pixels.

According to another characteristic, pixels comprise at least one black subpixel.

According to another characteristic, pixels comprise at least one sub-pixel of an elementary color chosen from cyan, magenta and yellow.

According to another characteristic, pixels comprise at least one sub-pixel of an elementary color chosen from red, green and blue.

According to another characteristic, pixels comprise at least one white sub-pixel.

According to another characteristic, the perforation step produces a hole whose depth is such that the hole passes through the arrangement of pixels throughout its thickness.

According to another feature, the perforation step makes a hole through the support over its entire thickness.

According to another characteristic, a sub-pixel has a dimension according to the extension of the support between 30μ and 150μ and a hole has a dimension according to the extension of the support between 50μ and 500μ.

According to another characteristic, the perforation step is performed by means of a laser beam.

The invention further relates to an arrangement of pixels, each pixel comprising elementary color sub pixels, wherein pixels comprise at least one black subpixel, wherein some subpixels are perforated to effect selective destruction, partial or total, of said sub-pixels to produce a color image.

The invention further relates to a security device comprising such an arrangement.

• la figure 1 présente un premier mode de réalisation d'un arrangement selon l'invention, vue de face,
• la figure 2 présente un deuxième mode de réalisation d'un arrangement selon l'invention, vue de face,
• la figure 3 présente un premier mode de réalisation d'un dispositif de sécurité selon l'invention en vue de profil,
• la figure 4 présente un deuxième mode de réalisation d'un dispositif de sécurité selon l'invention en vue de profil.

Other features, details and benefits of the invention will emerge more clearly from the detailed description given below as an indication in relation to drawings in which:

• the figure 1 presents a first embodiment of an arrangement according to the invention, seen from the front,
• the figure 2 presents a second embodiment of an arrangement according to the invention, seen from the front,
• the figure 3 presents a first embodiment of a security device according to the invention in view of profile,
• the figure 4 presents a second embodiment of a security device according to the invention in profile view.

In order to be able to realize a color image, the invention comprises an arrangement 2 of pixels, a possible embodiment of which is illustrated in FIG. figure 1 in front view. Such an arrangement 2 is able to receive an image. For this it has a main extension substantially surface. The figure 1 , respectively 2, shows an arrangement 2 seen substantially normal to said surface.

Such an arrangement 2 comprises a plurality of pixels 3, each pixel 3 being intended to become an elementary part of the image produced. In such an arrangement 2, the pixels can be arranged in a regular and periodic manner. However this is not necessary. A different map can be used as long as it is known to the process making the perforations.

Each pixel 3 comprises sub-pixels 4c, 4m, 4j, 4n, 4b. Each sub-pixel 4c, 4m, 4j, 4n, 4b typically comprises an elementary color. The pixels 3 of an arrangement 2 may be identical in terms of choice of colors and / or number of sub-pixels per pixel 3. However, this is not necessary. A different map can be used as long as it is known to the process making the perforations.

In known manner, with at least three sub-pixels per pixel 3, these sub-pixels being each of a basic color of a basic system, it is possible to express a wide variety of colors. Two such basic tri-chromic basic systems are the RGB (or RGB) system, comprising the three colors Red, Green and Blue, and the CMY (or CMY) system, comprising the three colors Cyan, Magenta and Yellow. .

By modulating the respective intensities or amounts of color of each of the sub-pixels 4c, 4m, 4y, 4n, 4b, it is possible to obtain numerous hue variations, covering a large extent of the color spectrum, and to all the less sufficient to produce a color image, such as a reproduction of a photo. A given hue can be broken down into the basic colors of a basic system.

It is assumed, by way of illustration, that a pixel 3 of a hue composed of 100% Red, 50% Green and 0% Blue is desired in a basic RGB system. To obtain such a hue for this pixel, it is advisable to leave the red subpixel (s) visible, to leave visible one half of the subpixel (s) Green, and to make invisible the one or more subpixel (s) Blue.

Depending on the technology used, the means to make visible or invisible all or part of a sub-pixel varies. According to the prior art already mentioned, masking, performed by carbonization by means of a laser in a suitable layer disposed above an arrangement, makes it possible to mask all or part of a determined sub-pixel. A variable size of the laser "point" determines the amount of subpixel area, and thus the amount of color, which is masked and by difference the amount of surface / color that is left visible.

According to an important feature of the invention, a perforation is used. This perforation, made selectively on each sub-pixel, can produce at least one hole 6, 6 'so as to destroy all or part of a sub-pixel 4c, 4m, 4y, 4n, 4b, and thus all or part of the elementary color associated. The number and size of holes 6, 6 'thus produced is a function of the desired hue for the pixel 3. Thus, to express an elementary color at X%, at least one hole 6 totaling a relative area of 100-X% must be made in the slot (s). -pixels associated with said elementary color, so as to leave visible an amount / intensity of X% of said elementary color.

The figure 1 presents a first embodiment of an arrangement 2. This arrangement 2 comprises pixels 3, substantially hexagonal, substantially contiguous and arranged periodically over the entire surface of the arrangement 2. A pixel 3 here comprises seven sub-pixels 4c, 4m , 4j, 4n, whose colors are chosen from four elemental colors. In the present application the same pattern (gray, hatched, squared, ...) is the same color. These seven sub-pixels 4c, 4m, 4j, 4n here comprise, for each pixel 3, two sub-pixels 4c of Cyan color, two sub-pixels 4m of Magenta color, two yellow sub-pixels 4j and a sub-pixel pixel 4n Black color. This organization of the sub-pixels 4c, 4m, 4j, 4n within the pixel 3 can be reproduced identically for all the pixels 3. Alternatively it can be modified at will as much in the choice of colors, as in the number of subpixels assigned to each color, only in the relative position of a color in the pixel 3.

An illustrative hole 6 shows how can be removed, by perforation, here about 80% of the surface of a sub-pixel Cyan, about 40% of the amount of Cyan pixel 3.

The figure 2 presents a second embodiment of an arrangement 2. This arrangement 2 comprises pixels 3, substantially trapezoidal, one of which is shown. Here again the pixels 3 may or may not be arranged substantially contiguous and periodically over the entire surface of the arrangement 2. The periodicity can here be achieved by alternating a pixel as shown and a pixel rotated 180 °. A pixel 3 here comprises five sub-pixels 4c, 4m, 4j, 4n, 4b whose colors are chosen from five elementary colors. These five sub-pixels 4c, 4m, 4j, 4n, 4b comprise here a Cyan sub-pixel 4c, a Magenta 4m sub-pixel, a Yellow 4j sub-pixel, a Black 4n sub-pixel and a White 4b sub-pixel. This organization of the sub-pixels 4c, 4m, 4j, 4n, 4b within the pixel 3 can be reproduced identically for all the pixels 3. Alternatively it can be modified as desired in the choice of colors, as in the number of sub-pixels assigned to each color, only in the relative position of a color in the pixel 3.

It appears, when one wants to realize a color image reproducing the reality, for example an image appearing a photo, such as for example a portrait, that it is necessary to have Black. If we limit ourselves to a tri-chromic basic system, with pixels comprising three color subpixels chosen from a base system RGB or CMY, the image produced will lack contrast, shading.

According to the prior art cited, the black required to render a photo can be provided by the black dots, produced by laser carbonization, made to selectively hide the sub-pixels. This source of black is not available when the expression of the hues is achieved by perforation.

It should however be noted that the use of the black according to the aforementioned prior art is delicate. Indeed black produced by laser carbonization is determined for each pixel by the hue that is desired to express and is therefore quantified and positioned in the image. Also it seems difficult or impossible to modulate the intensity of Black according to the needs of Black imposed by the photo, the two constraints of hue and black are unlikely to be identical.

According to an important characteristic of the invention, the black necessary for the rendering of a photograph is provided by the arrangement 2 itself, in that all or part of the pixels 3 of said arrangement 2 comprise at least one black sub-pixel 4n. .

With such pixels 3, comprising at least one sub-pixel 4n Black, it is possible to modulate the amount of Black in the image. Thus, by perforating said black sub-pixel 4n with a hole 6 with an area of X% of the surface of the black sub-pixel 4n, 100-X% of Black is retained.

This embodiment is particularly advantageous in view of the prior art in that the amount of black can be modulated independently of the other colors and thus correspond well to the need for black dictated by the image.

Two examples of arrangements 2 comprising pixels 3 comprising such subpixels 4n Black are illustrated in FIGS. Figures 1 and 2 .

According to an alternative embodiment or complementary to the introduction of black sub-pixels, it is possible to use a laser carbonization step to bring the black. In this case the support 1 further comprises a layer 12 capable of being blackened, typically by means of a laser beam. This layer 12 is preferably arranged above the arrangement 2, so that the observer's eye meets the layer 12 before the arrangement 2. The process then comprises an additional step of creating black by darkening. selective of said layer 12. It may be noted that this step is advantageously not constrained by the desired hue, and that it can freely make the black dictated by the image.

It has been seen that the colors of the basic system could be very varied. However, it has been found empirically that the basic system CMJ (Cyan, Magenta, Yellow) is more efficient in that it brings on average a greater brightness. This allows a better rendering of a color image. Also an arrangement 2 preferably comprises pixels 3 comprise at least one sub-pixel 4c, 4m, 4j of an elemental color selected from Cyan, Magenta, Yellow.

By integrating the preceding characteristic, an arrangement 2 preferably comprises pixels 3 comprise at least one sub-pixel 4c, 4m, 4j, 4n of an elementary color chosen from Cyan, Magenta, Yellow, Black.

In order to still modulate the amount of white in an image, an arrangement 2 advantageously comprises pixels 3 comprising at least one white sub-pixel 4b.

A perforation, removes part of the arrangement 2, and thus produces a hue. This hue depends on the hue of the support 1 and its optical characteristics, including transparency. This hue still depends on the background if the support is transparent and / or the perforation is through. All this produces an eminently variable result. Also it can not be based on a simple perforation to reproduce the White. In addition, such an approach, for an image with a lot of white lead to an overabundance of perforations tending to weaken the support 1.

Also the presence, at least in some pixels 3, of a white subpixel 4b is advantageous in that it makes it possible to express White independently of the support and the background and without perforation, thus without removing material.

Starting from a support 1 comprising such an arrangement 2, according to one of the previously described embodiments, it is possible to carry out a color image in said support 1.

In known manner, the image to be reproduced is cut into pixels in correspondence with the pixels 3 of the arrangement 2. For each such pixel 3, the image determines the hue of the pixel 3. Said hue is decomposed into components according to the colors available in the sub-pixels 4c, 4m, 4j, 4n, 4b of said pixel 3. These components, determine a percentage X% to maintain each elementary color of said pixel 3. It is then proceeded to a perforation step, aimed at removing a complementary portion 100-X% of the surface of the subpixel (s) of said elementary color. It is thus practiced, in each sub-pixel to be reduced, a surface reduction corresponding to 100-X%, by means of at least one hole 6,6 'totaling a surface of 100-X%, relative to the surface total of this elemental color.

Reference is now made to the figure 3 , having a support 1, in profile view, cut according to its thickness. Such a support 1, substantially surface, comprises at least one arrangement 2 comprising pixels 3 comprising sub-pixels 4c, 4m, 4j, 4n. Such a support 1 may also optionally comprise a substrate layer 13, which may be opaque or transparent. The substrate 13 can be any type of material, such as paper, plastic, such as for example a thin plastic bank card type card, on which is affixed a security device comprising an arrangement 2 and in which is, if appropriate, realized a color image. The substrate 13 takes the place of the frame 2. Such a support 1 may optionally further comprise a protective layer 12. This protective layer must necessarily be transparent, so that the image produced in the arrangement 2 is visible. from the outside. This protective layer provides isolation of the arrangement from the outside and can contribute to security of the security device by prohibiting direct access to the arrangement 2. Other layers can still be added at leisure, from on both sides of the arrangement 2.

With reference to the figure 3 another characteristic is described. In order to realize the invention, it is appropriate that the perforation step makes a hole 6, 6 'which vertically destroys entirely the elementary color that we do not wish to appear, and therefore the part of the sub-pixel or sub-pixels. (s) 4c, 4m, 4j, 4b corresponding (s). For this it is appropriate that the depth 7, respectively 7 ', of a hole 6, respectively 6', is such that the hole 6,6 'passes through the arrangement 2 of pixels 3 over its entire thickness 8. Thus a hole 6 pierced from an upper layer 12 must have a depth 7 sufficient to reach or exceed the bottom of the arrangement 2. Similarly a hole 6 'pierced from a lower layer 13 must have a depth 7' sufficient to reach or exceed the top of the arrangement 2.

It appeared in use that 6,6 'non-through holes, because of their small transverse dimensions 11, could fill. This filling can induce a detrimental modification of the optical characteristics and thus the rendering of the color image produced. This filling may still be detrimental to a seat of biological contamination.

Also, according to a preferred embodiment, making it possible to remedy, at least partially, the two aforementioned drawbacks, more particularly illustrated in FIG. figure 4 , the holes 6,6 'made by the perforation operation are made outlets, so as to pass through the support 1 over its entire thickness 9.

According to an alternative embodiment, the holes may be made through or not, and the support 1 thus obtained may be completed by a closure layer closing the openings of the holes 6,6 ', so as not to leave them in the air free.

Returning now to the front view, for example with the figure 2 will be indicated some indicative dimensions.

The transverse dimension of a sub-pixel 4c, 4m, 4j, 4n, 4b, according to the extension of the support 1, for example its diameter in the case of a circular sub-pixel, is typically between 30μ and 600μ.

The transverse dimension 11 of a hole 6, according to the extension of the support 1, for example its diameter in the case of a circular hole 6, is typically between 30μ and 600μ.

The transverse dimension 10 of a sub-pixel should be of the same order of magnitude as the transverse dimension 11 of a hole 6. The limiting factor is today the minimum transverse dimension 11 of a hole 6 that can be made in function perforation technology. The transverse dimension 10 of a sub-pixel and therefore the entire arrangement 2 is dimensioned according to this minimum transverse dimension 11.

The perforation step may be performed by any mechanical, electrical, chemical or other means. Given the relatively small dimensions of the holes to be made, the perforation step is advantageously carried out by means of a laser beam.

Claims (13)

1. A method for producing a colour image in a support (1) of substantially planar main direction, said support (1) comprising an arrangement (2) of pixels (3), each pixel (3) comprising sub-pixels (4c,4m,4j,4n,4b) of elementary colour, characterized in that said method comprises a perforation step of some sub-pixels (4c, 4m, 4j, 4n, 4b) carrying out selective, partial or total destruction of said sub-pixels (4c, 4m, 4j, 4n, 4b).
2. The method according to claim 1, wherein pixels (3) comprise at least one black sub-pixel (4n).
3. The method according to any one of claims 1 or 2, wherein pixels (3) comprise at least one sub-pixel (4c,4m,4j) of elementary colour selected from cyan, magenta, yellow.
4. The method according to any one of claims 1 to 3, wherein pixels (3) comprise at least one sub-pixel (4c,4m,4j) of elementary colour selected from red, green, blue.
5. The method according to any one of claims 1 to 4, wherein pixels (3) comprise at least one white sub-pixel (4b).
6. The method according to any one of claims 1 to 5, wherein the perforation step makes a hole (6) whereof the depth (7) is such that the hole (6) passes through the arrangement (2) of pixels (3) over its entire thickness (8).
7. The method according to claim 6, wherein the perforation step makes a hole (6) passing through the support (1) over its entire thickness (9).
8. The method according to any one of claims 1 to 7, wherein a sub-pixel (4c,4m,4j,4n,4b) has a dimension (10) according to the direction of the support (1) comprised between 30µ and 600µ and wherein a hole (6) has a dimension (11) according to the direction of the support (1)comprised between 30µ and 600µ.
9. The method according to any one of claims 1 to 8, wherein the perforation step is conducted by means of a laser beam.
10. An arrangement (2) of pixels, each pixel (3) comprising sub-pixels (4c,4m,4j,4n,4b) of elementary colour, in which pixels (3) comprise at least one black sub-pixel (4n),
    characterized in that some sub-pixels (4c,4m,4j) are perforated so as to carry out selective, partial or total destruction of said sub-pixels (4c,4m,4j,4n,4b) to produce a colour image.
11. The arrangement (2) according to claim 10, wherein pixels (3) comprise at least one sub-pixel (4c,4m,4j) of elementary colour selected from cyan, magenta, yellow.
12. The arrangement (2) according to any one of claims 10 or 11, wherein pixels (3) comprise at least one white sub-pixel (4b).
13. A security device characterized in that it comprises an arrangement (2) according to any one of claims 10 to 12.

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