Secure item comprising a combined image and/or a revealing screen

Abstract

A secure item including a first optical structure and a second optical structure, or an assembly comprising a secure item and another object. The first optical structure including a plurality of blocks and being one of a revealing screen and a combined image. The second optical structure being the other one. Each of the combined image blocks being made up of a plurality of interlaced images. The combined image or each combined image block including a periodic alternation of interlaced image elements. The elements of the interlaced images of a single interlaced image being the same color, but a different color from that of the other interlaced images. At least two blocks of the first optical structure each allowing the observation of a revealed image in each block of a first optical structure, showing different proportions of the interlaced images.

Claims

1. A secure item comprising a first optical structure and a second optical structure, or assembly comprising a secure item and another object, the secure item comprising one of the first optical structure and of the second optical structure and the object comprising or forming the other of the first optical structure and of the second optical structure, the first optical structure comprising at least two blocks of first optical structure arranged in different regions of the first optical structure and the second optical structure comprising a single block of second optical structure, a.) the first optical structure being a revealing raster, the blocks of revealing raster each comprising a periodic alternation of occulting raster elements and of non-occulting raster elements in one or more directions and being of the same period in the or in each of the directions, the at least two blocks of first optical structure comprising raster elements of different dimensions according to the or to at least one of the directions, or raster elements that are mutually phase-shifted along an axis perpendicular to the or to one of the directions by a distance d.sub.ij which is less than the period in this direction of the blocks of first optical structure, the distance d.sub.ij being the remainder of the division of the distance c.sub.ij between the axis of an occulting element of one of the two raster blocks and the axis of an occulting element of one of the other of the two raster blocks, by the period of the revealing raster the second optical structure being the combined image being composed of a plurality of interlaced images, the combined image comprising a periodic alternation of elements of interlaced images in one or more directions, or b.) the first optical structure being a combined image, the blocks of combined image being each composed of a plurality of interlaced images, each blocks of combined image comprising a periodic alternation of elements of interlaced images in one or more directions and being of the same period in the or in each of the directions, the at least two blocks of the first optical structure comprising elements of corresponding combined images of different dimensions according to the or to at least one of the directions, or combined-image elements that are mutually phase-shifted along an axis perpendicular to the or to one of their directions by a distance d.sub.ij which is less than the period in this direction of the blocks of first optical structure, the distance d.sub.ij being the remainder of the division of the distance c.sub.ij between the axis of an element of interlaced images of one of the two combined-image blocks and the axis of an interlaced-image element of the same interlaced image of the other of the two combined-image blocks, by the period of the combined image, the second optical structure being the revealing raster comprising a periodic alternation of occulting raster elements and of non-occulting raster elements in one or more directions, the elements of the interlaced images of one and the same interlaced image being of the same color but of a different color from that of the other interlaced images, at least two blocks of first optical structure each allowing, when the revealing raster and the combined image are superposed, such that the revealing raster and the combined image have the same one or more direction, at a given position and orientation of the revealing raster with respect to the combined image and at a given angle of observation , the observation of a revealed image at the level of each block of first optical structure, the revealed images at the level of the two blocks of first optical structure unveiling different proportions of the interlaced images, the period of the combined image or of each of the blocks of the combined images in the or one of the directions being equal to the period in this direction of the revealing raster or of each of the blocks of revealing raster and the elements of interlaced images and the raster elements being of the same general shape.

2. The item or assembly as claimed in claim 1, the elements of interlaced images being interlaced image lines of mutually parallel longitudinal axes.

3. The item or assembly as claimed in claim 1, the first optical structure being the revealing raster, the at least two blocks of the revealing raster being arranged in regions of the revealing raster that are partially superposed and defining a sub-block exhibiting a periodic alternation in the or in a direction of two different aspect raster elements, the occulting raster element having a dimension in this direction that is greater than or equal to that of each of the superposed blocks, and/or a periodic alternation in the or in a direction of four raster elements, the raster elements of the two blocks being mutually interleaved, each raster element exhibiting a different aspect from the directly adjacent raster elements.

4. The item or assembly as claimed in claim 1, the at least two blocks of the first optical structure being arranged in distinct regions of the first optical structure.

5. The item or assembly as claimed in claim 1, the combined image exhibiting a resolution of greater than or equal to 800 dpi.

6. The item or assembly as claimed in claim 1, the revealed images exhibiting an aspect, especially a color, which is homogeneous to the naked eye and at a normal observation distance.

7. The item or assembly as claimed in claim 1, the at least two blocks each allowing, when the revealing raster and the combined image are superposed, at a given position and orientation of the revealing raster with respect to the combined image and at a given angle of observation , the observation of revealed images consisting of two adjacent interlaced images, the revealed images comprising at least one different interlaced image.

8. The item or assembly as claimed in claim 1, the at least two blocks each allowing, when the revealing raster and the combined image are superposed, at a given position and orientation of the revealing raster with respect to the combined image and at a given angle of observation , the observation of an interlaced image.

9. The item or assembly as claimed in claim 1, the revealed images forming a macropattern when the revealing raster is superposed with the combined image, at a given position and orientation of the revealing raster with respect to the combined image and at a given angle of observation .

10. The item or assembly as claimed in claim 1, the combined image and/or the revealing raster comprising metallizations and/or demetallizations.

11. The item or assembly as claimed in claim 1, the revealed images being visible by observation under reflected light and/or under transmitted light.

12. The item or assembly as claimed in claim 1, one at least of the combined image and of the revealing raster featuring on a region of the secure item or of the at least partially transparent object, the superposition of the revealing raster and of the combined image being performed by folding of the secure item or by superposition of the secure item with the other object.

13. The item or assembly as claimed in claim 1, the revealing raster and the combined image being superposed by being separated from one another by a gap of constant thickness.

14. The item or assembly as claimed in claim 1, the other object being an electronic imager making it possible to form a first image, the first image being the revealing raster or the combined image, so as to be able to superpose it with a second image of the secure item, the second image being the other of the revealing raster and of the combined image.

15. A secure item or assembly as claimed in claim 1 comprising two first optical structures on the secure item or on the object, the first optical structures being revealing rasters and the second optical structure being a combined image or the two first optical structures being combined images and the second optical structure being a revealing raster, when the two first optical structure and the second optical structure are superposed, at a position of the two first optical structure with respect to the second given optical structure and at a given angle of observation , at least two blocks of one of the first optical structure or of the second optical structure each allowing, at a first orientation of said one of the first optical structures with respect to the second optical structure, such that the blocks of said one of the first optical structures and the combined image have the same one or more direction, the observation of a first revealed image at the level of each block of said one of the first optical structures, the first revealed images at the level of the two blocks of said one of the first optical structures or of the second optical structure unveiling different proportions of the interlaced images, at least two blocks of the other of the first optical structures each allowing, at a second orientation of said one of the first optical structures with respect to the second optical structure, such that the blocks of said other of the first optical structures and the combined image have the same one or more directions, the observation of a second revealed image at the level of each block of said other of the first optical structures or of the second optical structure, the second revealed images at the level of the two blocks of said other of the first optical structure or of the second optical structure unveiling different proportions of the interlaced images, the first and the second orientation being different.

16. A method for authenticating a secure item as claimed in claim 1, in which one observes the revealed images by the blocks of the first optical structure(s) and one concludes at least on the basis of this observation as to the authenticity of the item.

17. The item or assembly as claimed in claim 2, the elements belonging to different interlaced images being different by their aspects, especially their hues, opacities, saturations, luminescences, or brightnesses.

18. The item or assembly as claimed in claim 2, the interlaced-image lines being of dimension in the or each of the directions which is less than or equal to 1 mm.

19. The item or assembly as claimed in claim 4, the at least two blocks exhibiting a part of their contours in common.

20. The item or assembly as claimed in claim 9, the macropattern changing aspect upon a change of the position of the revealing raster with respect to the combined image and/or a change of the angle of observation .

21. The item or assembly as claimed in claim 9, the macropattern disappearing upon a change of the orientation of the revealing raster with respect to the combined image.

22. The item or assembly as claimed in claim 12, each block making it possible when superposed at least partially with the combined image of the same secure item or of the other object to observe different revealed images by a relative displacement of the revealing raster with respect to the combined image.

23. The item or assembly as claimed in claim 13, each block making it possible to observe different revealed images upon a change of the angle of observation a of the security document.

24. The item or assembly as claimed in claim 15, the first revealed images forming a first pattern in the first orientation and the second revealed images forming a second pattern in the second orientation, the first pattern not being visible in the second orientation and the second pattern not being visible in the first orientation.

25. The authentication method as claimed in claim 16, in which the angle of observation and/or the position of the revealing raster or rasters with respect to the combined image is changed so as to observe a change of the revealed image for each block of the first optical structure(s).

26. Item or assembly, as claimed in claim 17, the elements belonging to different interlaced images being of different hues.

Description

(1) The invention will be able to be better understood on reading the detailed description which will follow, of nonlimiting exemplary implementations of the latter, and on examining the appended drawing in which:

(2) FIG. 1 illustrates the formation of a combined image,

(3) FIGS. 2A to 2C represent a succession of revealed images such as it may be observed when the observation conditions vary,

(4) FIGS. 3A to 3C represent a variant succession of revealed images such as it may be observed when the observation conditions vary,

(5) FIGS. 4A and 4B illustrate a revealing raster,

(6) FIGS. 4C to 4E represent a succession of revealed images such as it may be observed with the aid of the combined image of FIG. 1 and of the revealing raster of FIG. 4A, when the observation conditions vary,

(7) FIG. 4F illustrates a detail of FIG. 4A,

(8) FIGS. 5A to 5C represent junction variants for joining between two adjacent blocks,

(9) FIG. 6A illustrates a variant revealing raster,

(10) FIGS. 6B to 6D represent a variant succession of revealed images such as it may be observed with the aid of the combined image of FIG. 1 and of the revealing raster of FIG. 6A when the observation conditions vary,

(11) FIG. 7A illustrates a variant revealing raster,

(12) FIGS. 7B to 7C represent a succession of revealed images such as it may be observed with the aid of the combined image of FIG. 1 and of the revealing raster of FIG. 7A when the observation conditions vary,

(13) FIGS. 8A and 8B represent variants of combined images,

(14) FIGS. 9A to 9H represent variants of revealing rasters,

(15) FIG. 10 illustrates revealed images such as they may be observed with the aid of the combined image of FIG. 1 and of a revealing raster,

(16) FIGS. 11A and 11B illustrate revealed images such as they may be observed with the aid of the combined image of FIG. 1 and of variants of revealing rasters,

(17) FIG. 12A illustrates the decomposition into interlaced images of a pattern of the combined image,

(18) FIG. 12B illustrates revealed images such as they may be observed with the aid of the combined image formed by the pattern of FIG. 12A and of a revealing raster,

(19) FIG. 13 represents in cross-section, in a schematic and partial manner, an exemplary secure item produced in accordance with an exemplary implementation of the invention,

(20) FIG. 14 illustrates the possibility of varying the inclination by deforming the secure item,

(21) FIGS. 15 and 16 represent two examples of secure items according to the invention,

(22) FIGS. 17A to 17D represent other examples of secure items according to the invention, in transverse section, in a schematic manner,

(23) FIGS. 18 and 19 illustrate variant embodiments of secure items according to the invention, in transverse section, in a schematic manner,

(24) FIG. 20 represents an exemplary embodiment of secure item according to the invention, the combined image or the revealing raster being carried by a window of the item,

(25) FIG. 21 represents the secure item folded,

(26) FIGS. 22 and 23 represent exemplary embodiments of secure item according to the invention,

(27) FIGS. 24 to 28 represent other exemplary embodiments of secure items according to the invention, the combined image and/or the revealing raster being carried by at least one security thread or a foil.

(28) FIG. 29A represents another exemplary combined image,

(29) FIG. 29B represents a variant with two revealing rasters,

(30) FIGS. 29C, 29D, 29F and 29G represent a succession of revealed images such as it may be observed with the aid of the combined image of FIG. 29A and of the revealing rasters of FIG. 29B when the observation conditions vary and the orientation of the rasters and of the combined image varies between a position illustrated in FIG. 29E and another position,

(31) FIGS. 30 to 32 represent variant assemblies comprising an electronic imager and an item,

(32) FIG. 33 represents a variant of first images formed by an electronic imager,

(33) FIG. 34 represents a variant item comprising an integrated microcircuit,

(34) FIG. 35 represents a variant assembly, the item comprising a second image in the form of a revealing raster and the electronic imager producing a first image in the form of a combined image,

(35) FIG. 36A represents another exemplary combined image,

(36) FIG. 36B represents a variant with a revealing raster in the form of pixels,

(37) FIGS. 36C to 36E represent a succession of revealed images such as it may be observed with the aid of the combined image of FIG. 36A and revealing rasters of FIG. 36B when the observation conditions vary and/or the relative position of the rasters and of the combined image varies,

(38) FIG. 37A illustrates a variant combined image, and

(39) FIGS. 37B to 37D represent a variant succession of revealed images such as it may be observed with the aid of the combined image of FIG. 37A and of a revealing raster when the observation conditions vary.

(40) Combined Image

(41) Illustrated in FIG. 1 is an example of forming a combined image I by adding together a plurality of interlaced images I.sub.1, I.sub.2, . . . , I.sub.n. Each interlaced image I.sub.i is formed of interlaced image lines i.sub.i arranged in a periodic manner in the direction X.sub.I and of like width l.sub.i constant over their entire length. The interlaced images are of like period S.

(42) The interlaced image lines i.sub.i have parallel longitudinal axes defining a general orientation O.sub.i of the image combined by their general direction. The periodicity is observed along an axis X.sub.I perpendicular to the longitudinal axis of the interlaced image lines.

(43) The lines of an interlaced image are continuous and of like length, but it may be otherwise.

(44) The combined image I corresponds to the superposition of these interlaced images I.sub.1 to I.sub.n while shifting them with respect to one another along the axis X.sub.I so that the interlaced image lines i.sub.1 to i.sub.n are not superposed between the various images.

(45) The widths l.sub.1 to l.sub.n of the lines of the interlaced images i.sub.1 to i.sub.n are such that the sum of the widths l.sub.1 to l.sub.n of these lines l.sub.1 to i.sub.n is less than or equal to the period S, and preferably, equal to the period S:

(46) $\underset{j=1}{\overset{n}{.Math.}}\mathrm{lj}=S$

(47) In the example illustrated, the lines of an interlaced image i.sub.1 to i.sub.3 are of like width l.sub.1 to l.sub.3 equal to S/3.

(48) As a variant, the lines i.sub.1 to i.sub.n of the interlaced images may be of widths l.sub.1 to l.sub.n that differ with respect to one another, such as represented in FIG. 8A.

(49) In the example of FIG. 1, the combined image I is formed of three interlaced images I.sub.1 to I.sub.3. The first interlaced image I.sub.1 is formed of a periodic red line i.sub.1, the second interlaced image I.sub.2 is formed of a periodic green line i.sub.2 and the third interlaced image I.sub.3 is formed of a periodic blue line i.sub.3. The three lines of the interlaced images i.sub.1 to i.sub.3 are of like width l. The lines of the interlaced images i.sub.1 to i.sub.3 are rectilinear. The resulting combined image I is a rasterized image exhibiting a periodic alternation of lines i.sub.1 to i.sub.3 of various colors.

(50) The period S is between 10 m and 1 mm, preferably between 50 and 200 m.

(51) The width l of the lines of the interlaced images i.sub.1 to i.sub.n is less than or equal to 50 m, being for example substantially equal to 33 m. This value corresponds to a resolution of the combined image I of about 800 dpi, this representing a limit for conventional printers which generally have a maximum definition of 600 dpi, and which constitutes a security factor.

(52) Moreover, the human eye not perceiving, at an observation distance of greater than or equal to 30 cm, details of less than approximately 100 m, a sufficiently fine combined image appears of homogeneous aspect, for example substantially white here in transmitted light.

(53) Hence, whatever the color or colors used for the combined image, the printing definition may be precise enough for the mixture of the colors to appear as homogeneous.

(54) As a further variant illustrated in FIG. 8B, the lines of the interlaced images i.sub.1 to i.sub.n comprise micropatterns 7, and better are formed by micropatterns 7. The micropatterns 7 of the lines i.sub.i of an interlaced image may be colored in a single color so that the lines i.sub.i appear colored, or not. Preferably, the micropatterns 7 are of the width l of the lines i.sub.i of the interlaced image and of a height of the same order of magnitude so that, in view of the resolution, the lines i.sub.i appear a homogeneous color to the eye, the micropatterns 7 not being distinguishable with the naked eye at 15 cm distance. The user must for example use a magnifying glass to view the micropatterns 7, thus strengthening the security of the item. The micropatterns 7 may be write-positive or write-negative.

(55) In the example illustrated in FIG. 8B, the combined image I is formed of three interlaced images I.sub.1, I.sub.2 and I.sub.3 such as described previously, except that the interlaced-image lines i.sub.1, i.sub.2 and i.sub.3 are not lines of homogeneous color but lines of micropatterns 7 colored in write-positive. The lines w are formed of a repetition of the number 100 colored red, the lines i.sub.2 are formed of a repetition of the word AWS colored green and the lines i.sub.3 are formed of a repetition of the word BUTTERFLY colored blue.

(56) The combined image I may be formed by printing, especially by four-color printing.

(57) As a variant, the combined image I is formed by metallization and/or demetallization, especially by metallization with the aid of metals of different colors for each of the interlaced images I.sub.1 to I.sub.n. For example, the combined image I comprises two interlaced images I.sub.1 and I.sub.2, one being made of copper and the other of aluminum.

(58) The interlaced images I.sub.1 to I.sub.n may be glossy or matt. For example, the interlaced images are at least differentiated partially by their glossiness, some interlaced images being matt and other interlaced images being glossy.

(59) As will be described hereinafter, the combined image I may also be formed by an electronic imager 100.

(60) Revealing Raster

(61) In the example illustrated in FIGS. 2A to 3C, the revealing raster 4 is composed of a periodic alternation of constant period Q of straight and occulting raster lines 5a, especially of black opaque lines, and of non-occulting lines 5b, especially of transparent lines having parallel longitudinal axes. The periodicity is observed along an axis X.sub.T perpendicular to the longitudinal axis of the raster lines 5a and 5b.

(62) The longitudinal axes of the raster lines 5a and 5b define a general orientation of the raster O.sub.t by their general direction.

(63) The opaque raster lines 5a are of a constant width m which is less than the period Q of the raster and the transparent raster lines 5b are of a constant width k which is less than the period Q.

(64) The widths of the opaque raster lines 5a and of the transparent raster lines 5b may or may not be identical.

(65) In the example illustrated, the raster lines 5a and 5b have rectilinear and parallel edges, but it may be otherwise. The revealing raster 4 may comprise other patterns such as crenellations or undulations, such as is illustrated respectively in FIGS. 9A and 9B.

(66) The resolution of the revealing raster 4 is, preferably, greater than or equal to 800 dpi.

(67) The revealing raster 4 may be as such of homogeneous aspect to the naked eye and at a normal observation distance, having regard to its fineness. In particular, the revealing raster may appear to the naked eye at 15 cm distance as having a uniform, gray color, which is darker or lighter according to the width m of the opaque raster line 5a.

(68) A sufficiently fine combined image and a sufficiently fine revealing raster make it possible to afford anti-photocopy security.

(69) The combined image I and/or the revealing raster 4 may be formed by printing, metallization, demetallization, laser marking, lithography or any other technique making it possible to fix or unveil an image.

(70) To improve security, it is possible to use liquid-crystal inks, for example to print the combined image I. Animation, in order to be revealed, may then require in addition to the revealing raster, the use of a polarizer filter, which may or may not be present on the item.

(71) The revealing raster 4 may be formed by printing or metallization and/or demetallization.

(72) The opaque raster lines 5a of the revealing raster 4 may be glossy or matt.

(73) As a variant, the revealing raster 4 is different, especially the raster lines are not opaque and transparent. The occulting raster lines may be formed of a filter not allowing the wavelengths corresponding to the combined image to pass through and the non-occulting raster lines may allow these wavelengths to pass through at least partially.

(74) Revealed Image

(75) The period Q of the revealing raster 4 is equal to the period S of the combined image I.

(76) When the revealing raster 4 and the combined image I are superposed and the general orientation O.sub.t of the revealing raster 4 is substantially the same as the general orientation O.sub.i of the combined image I, a revealed image I.sub.r may be observed. The revealed image I.sub.r then corresponds to the parts of the combined image I that are present under the transparent raster lines 5b for a given angle of observation.

(77) Indeed, when the revealing raster 4 and the combined image I are superposed, under the condition cited previously and when the revealed images are observed on the revealing raster side, the opaque raster lines 5a mask one part of the interlaced image lines i.sub.1 to i.sub.n, the other part of the interlaced image lines i.sub.1 to i.sub.n being visible through the transparent raster lines 5b. The transparent raster lines 5b all allow the viewing of the same proportion (P.sub.1; . . . ; P.sub.n) of the interlaced image lines i.sub.1 to i.sub.n. The proportion P.sub.i corresponds to the proportion of a line i.sub.i of the interlaced image I.sub.i that is visible.

(78) In the case where the superposition is observed on the combined image I side, the opaque raster lines 5a render the interlaced image lines i.sub.1 to i.sub.n on which they are superposed dark and therefore prevent them being viewed. Thus only the interlaced image lines i.sub.1 to i.sub.n superposed on the transparent raster lines 4b are visible to form the revealed image I.sub.r.

(79) Preferably, the revealed images I.sub.r are observable in reflected light and in transmitted light.

(80) In the example of FIGS. 2A to 2C, the interlaced image lines i.sub.1 to i.sub.n are all of the same width l.sub.1 to l.sub.n and the opaque raster lines 5a have a width m equal to twice the width of the interlaced image lines i.sub.1 to i.sub.n. Thus, the opaque raster lines 5a, when they are properly positioned with respect to the interlaced image lines i.sub.1 to i.sub.n, cover two interlaced images, i.e. two colors, and only one interlaced image, i.e. a single color, is visible. In the case of FIG. 2A, all of the blue is visible and all of the red and the green are hidden, the proportion (P.sub.1; . . . ; P.sub.n) of the interlaced image lines i.sub.1 to i.sub.n of the revealed image I.sub.r is (0; 0; 1). Likewise for FIG. 2B, the proportion (P.sub.1; . . . ; P.sub.n) of the interlaced image lines i.sub.1 to i.sub.n of the revealed image I.sub.r is (1; 0; 0) and for FIG. 2C, the proportion (P.sub.1; . . . ; P.sub.n) of the interlaced image lines i.sub.1 to i.sub.n of the revealed image I.sub.r is (0; 1; 0).

(81) As a variant, in the example of FIGS. 3A to 3C, the interlaced image lines i.sub.1 to i.sub.n are all of the same width l.sub.1 to l.sub.n and the opaque raster lines 5a have a width m equal to 0.75 times the width of the interlaced image lines i.sub.1 to i.sub.n. Thus, the opaque raster lines 5a, when they are properly positioned with respect to the interlaced image lines i.sub.1 to i.sub.n, cover three-quarters of one of the interlaced images, i.e. three-quarters of a color, two interlaced images and a quarter of the third interlaced image are therefore visible. In the case of FIG. 3A, all of the blue and the green and a quarter of the red are visible and three-quarters of the red is hidden, the proportion (P.sub.1; P.sub.2; P.sub.3) of the interlaced image lines i.sub.1, i.sub.2 and i.sub.3 of the revealed image I.sub.r is (0.25; 1; 1). Likewise for FIG. 3B, the proportion (P.sub.1; P.sub.2; P.sub.3) of the interlaced image lines i.sub.1, i.sub.2 and i.sub.3 of the revealed image I.sub.r is (1; 0.25; 1) and for FIG. 3C, the proportion (P.sub.1; P.sub.2; P.sub.3) of the interlaced image lines i.sub.1, i.sub.2 and i.sub.3 of the revealed image I.sub.r is (1; 1; 0.25).

(82) The revealed image I.sub.r may appear homogeneous to the naked eye. In the case of a combined image I in the form of a colored raster formed of an alternation of red, green and blue lines of identical widths l and of a revealing raster of width of a transparent raster line k, it is possible to determine the color of the revealed image I.sub.r in RGB coordinates on the basis of the proportion (P.sub.R, P.sub.G, P.sub.B). The RGB coordinates take the form of three numbers lying between 0 and 255 characterizing said color, each number representing the proportion of one of the components red, green and blue making it possible to obtain said color.

(83) The components have coordinates:

(84) R=R.sub.max*P.sub.R,

(85) G=G.sub.max*P.sub.G, and

(86) B=B.sub.max*P.sub.B,

(87) with
R.sub.max=G.sub.max=B.sub.max=255*k/s

(88) It is thus possible to determine the color of the image revealed as a function of the width k of the transparent raster lines 5b and of the proportion (P.sub.R, P.sub.G, P.sub.B) of the interlaced images I.sub.1, I.sub.2 and I.sub.3. The revealed image Ir is observable in transmitted light or in reflected light at one and the same time on the revealing raster 4 side and on the combined image I side when the revealing raster 4 and the combined image I are superposed.

(89) In the variant illustrated in FIG. 36A, the combined image I comprises a periodic alternation of interlaced-image pixels p.sub.1 to p.sub.n in two directions X.sub.I and Y.sub.I. The interlaced-image pixels p.sub.1 to p.sub.n are of rectangular shape but it could be otherwise. For example the pixels could be of another polygonal shape, especially square, hexagon or lozenge.

(90) The pixels of FIG. 36A may also be seen as diagonal interlaced image lines formed of pixels joined together by one of their corners alternating periodically in the direction Z.

(91) The preceding description, given for lines, applies to the pixels. Thus, the pixels p.sub.1 to p.sub.n belonging to different interlaced images exhibit a different aspect, especially a different hue, saturation, glossiness, transparency, luminescence. For example the pixels p.sub.1 to p.sub.n belonging to different interlaced images are of different colors, especially red, green and blue.

(92) The combined image I exhibits a period S.sub.X in the direction X.sub.I and a period S.sub.Y in the direction Y.sub.I. Here, the directions X.sub.I and Y.sub.I are perpendicular but it could be otherwise. The directions X.sub.I and Y.sub.I could form a non-zero angle, different from 90, between themselves.

(93) The interlaced-image pixels p.sub.1 to p.sub.n exhibit a dimension l.sub.X and a dimension l.sub.Y in respectively the directions X.sub.I and Y.sub.I. The dimensions l.sub.X and l.sub.Y are each such as described previously for the interlaced image lines i.sub.1 to i.sub.n.

(94) The revealing raster 4 is according to FIG. 36B. It exhibits a periodic alternation of opaque raster pixels 5a in two directions X.sub.T and Y.sub.T forming between themselves the same angle as the directions X.sub.I and Y.sub.I. The opaque raster pixels 5a are separated from one another by transparent gaps 5b and repeat according to the periods S.sub.X and S.sub.Y of the combined image in the respective directions X.sub.T and Y.sub.T.

(95) The pixels of the revealing raster may be of a dimension m.sub.X and of a dimension m.sub.Y in the respective directions X.sub.T and Y.sub.T which are less than the periods S.sub.X and S.sub.Y respectively.

(96) In the example illustrated, the dimension m.sub.X in the direction X.sub.T is equal to the dimension l.sub.X of the interlaced-image pixels p.sub.1 to p.sub.n and the dimension m.sub.Y in the direction Y.sub.T is equal to the dimension l.sub.Y of the interlaced-image pixels p.sub.1 to p.sub.n.

(97) The dimensions m.sub.X and m.sub.Y may be different respectively from l.sub.X and l.sub.Y on condition that the periods in the directions X and Y are the same.

(98) Upon superposing the revealing raster 4 and the combined image I so that the directions X.sub.T and X.sub.I coincide and that the directions Y.sub.T and Y.sub.I coincide, the revealing raster makes it possible to observe revealed images I.sub.r such as are represented in FIGS. 36C to 36E.

(99) In the example illustrated the opaque raster pixels 5a hide one of the interlaced images I.sub.1 to I.sub.n so that two of the interlaced images are visible. In FIG. 36C, the revealed image I.sub.r is formed of the green and red interlaced images, in FIG. 36D, the revealed image I.sub.r is formed of the blue and red interlaced images and in FIG. 36E, the revealed image I.sub.r is formed of the blue and green interlaced images.

(100) The various revealed images I.sub.r illustrated may be obtained by displacing the revealing raster 4 with respect to the combined image in the direction X.sub.I, the direction Y.sub.I or the direction Z and/or by changing the angle of view around the directions X.sub.I and Y.sub.I or Z.

(101) Observation of a Change of the Revealed Image

(102) It is possible to vary the revealed image I.sub.r observed by changing the conditions of observation of the superposed revealing raster 4 and combined image I, and especially, as is detailed hereinafter, by changing the angle of observation and/or by displacing the revealing raster 4 with respect to the combined image I. Thus, virtually or really, by displacing the combined image I with respect to the revealing raster 4 in a direction X perpendicular to the general orientation of the combined image I and of the revealing raster 4, the revealed image I.sub.r varies.

(103) Thus, by changing the observation conditions, it is possible to pass from FIG. 2A to FIG. 2B and to FIG. 2C. The same holds for FIGS. 3A to 3C.

(104) By varying the observation conditions, the user may then see a change of the revealed image I.sub.r and conclude in view of this observation as to the authenticity of the item.

(105) Blocks

(106) As illustrated in FIGS. 4A, 6A and 7A, the revealing raster 4 may be formed of a plurality g of raster blocks B.sub.1 to B.sub.g. Each raster block B.sub.i is such as described for the revealing raster 4 in conjunction with FIGS. 2A to 3C and makes it possible to reveal, when the revealing raster is superposed with the combined image I such as described previously and its orientation is the same, a revealed image I.sub.r1 to I.sub.rg.

(107) The blocks B.sub.1 to B.sub.g of the revealing raster 4 are superposed with the same combined image I.

(108) Preferably, as illustrated, the blocks B.sub.1 to B.sub.g of one and the same raster are of the same period Q and of the same general orientation O.sub.b. The general orientations O.sub.b of the blocks 10 define a general raster orientation O.sub.t.

(109) The blocks B.sub.1 to B.sub.g exhibit a maximum dimension v of between 1.4 and 42 mm and an area equaling between 0.2 and 90% of the area of the revealing raster.

(110) In the examples illustrated in FIGS. 4A, 6A and 7A, the blocks B.sub.1 to B.sub.g exhibit opaque raster lines 5a of like width m and at least two of the blocks B.sub.1 and B.sub.j are mutually phase-shifted, that is to say exhibit a non-zero phase shift distance d.sub.ij of less than the period Q, the phase shift distance d.sub.ij being defined as the remainder of the division of the distance c.sub.ij between the longitudinal axis of a raster line i.sub.i of the block B.sub.i and the longitudinal axis of the consecutive raster line i.sub.j of the block B.sub.j by the period Q.
d.sub.ij=remainder(c.sub.ij/Q)

(111) When the revealing raster 4 is observed so that its general orientation O.sub.t is vertical, at least one part of the opaque raster lines of a block B.sub.i may be above and/or alongside at least one part of the opaque raster lines of another block B.sub.j.

(112) Thus, when the revealing raster is superposed with the combined image and exhibits the same general orientation, the transparent raster lines 5b of the block B.sub.i do not unveil the same proportion of the interlaced images (P.sub.1; . . . ; P.sub.n) as that of the block B.sub.j and therefore the images revealed I.sub.ri and I.sub.rj respectively by the blocks B.sub.1 and B.sub.j are of different aspects since they do not exhibit the same proportion (P.sub.1; . . . ; P.sub.n) of the interlaced images. In the case illustrated of a rasterized and colored combined image, for example with red, green and blue lines, the revealed images I.sub.r1 to I.sub.rg of the mutually phase-shifted blocks are of different colors.

(113) Preferably, the revealing raster 4 is continuous and each of the blocks B.sub.1 to B.sub.g exhibits a part of its contour in common with another of the blocks B.sub.1 to B.sub.g.

(114) The revealed images I.sub.r1 to I.sub.rg may form a pattern, especially a text, an alphanumeric sign, an ideogram, a geometric shape, an object, a person and/or an animal, for example reproduce a pattern present elsewhere on the secure item.

(115) By changing the conditions of observation of the superposed revealing raster 4 and combined image I, especially, as is detailed hereinafter, by changing the angle of observation and/or by displacing the revealing raster 4 with respect to the combined image I, the images revealed I.sub.r1 to I.sub.rg by the various blocks B.sub.1 to B.sub.g may vary. This change of aspect may give an impression of motion or may vary the color of a pattern.

(116) FIGS. 4C to 4E, 6B to 6D and 7B to 7C illustrate examples of revealing rasters 4 formed of blocks B.sub.1 to B.sub.g superposed with a combined image.

(117) In these examples, the revealing raster 4 is superposed with a combined image I formed of three interlaced images respectively colored red, green and blue, such as described previously.

(118) In the example illustrated in FIGS. 4A to 4E, the revealing raster 4 comprises six rectangular blocks B.sub.1 to B.sub.6 each forming about th of a rectangle, as is visible in FIG. 4B. Each of the blocks B.sub.1 to B.sub.6 exhibits a contour that is common with at least two other blocks B.sub.1 to B.sub.6. The area of each block B.sub.1 to B.sub.6 is substantially between 20% and 15% of the area of the revealing raster 4.

(119) The blocks B.sub.1, B.sub.2 and B.sub.3 are mutually phase-shifted and the block B.sub.4 is not phase-shifted with respect to the block B.sub.1, the block B.sub.5 is not phase-shifted with respect to the block B.sub.2 and the block B.sub.6 is not phase-shifted with respect to the block B.sub.3 so that each of the blocks B.sub.1 to B.sub.6 is phase-shifted with respect to the blocks B.sub.1 to B.sub.6 that are adjacent to it.

(120) As visible in FIG. 4F representing the joining of the blocks B.sub.1, B.sub.2, B.sub.3 and B.sub.4, when the general orientation O.sub.t of the revealing raster is oriented vertically, the blocks B.sub.1 and B.sub.3 are arranged one above the other and have an edge 6.sub.13, represented by dashes, in common whilst the blocks B.sub.1 and B.sub.2 are arranged one alongside the other with an edge 6.sub.12 in common.

(121) The opaque raster lines of the block B.sub.1 have a corner 9 in common with the opaque raster lines of the block B.sub.3. The same holds with the blocks B.sub.3 and B.sub.5, B.sub.2 and B.sub.4, and B.sub.4 and B.sub.6. As illustrated in FIG. 4F, the block B.sub.1 is phase-shifted from the block B.sub.3 by a phase shift distance du equal to the width m of an opaque raster line. The same holds with the blocks B.sub.3 and B.sub.5, B.sub.2 and B.sub.4, and B.sub.4 and B.sub.6. The distance cm between the last opaque raster line of the block B.sub.1 and the consecutive opaque raster line of the block B.sub.2 is equal to five times the width m of an opaque raster line. As the period Q is equal to three times the length m, the block B.sub.1 is phase-shifted from the block B.sub.2 by a phase shift distance d.sub.12 equal to twice the width m of an opaque raster line. The same holds with the blocks B.sub.3 and B.sub.4, and B.sub.5 and B.sub.6. The width m of the opaque raster line 5a is equal to the width l of an interlaced image line so that the transparent raster line may reveal two interlaced images.

(122) The revealed images I.sub.r1, I.sub.r2 and I.sub.r3 are phase-shifted and the respective revealed images I.sub.r1 and I.sub.r4, I.sub.r2 and I.sub.r5 and I.sub.r3 and I.sub.r6 are identical. The revealed images I.sub.r1 to I.sub.r6 form a rectangle composed of 6 squares each formed by a revealed image I.sub.r1 to I.sub.r6, each square neighboring squares of different colors. Thus, as illustrated in FIG. 4B, if the interlaced image I.sub.r1 exhibits interlaced image proportions (1; 1; 0), thus corresponding to an RGB color (170, 170, 0), then the interlaced image I.sub.r2 exhibits proportions (1; 0; 1), thus corresponding to an RGB color (170, 0, 170), and the interlaced image I.sub.r3 exhibits proportions (0; 1; 1), thus corresponding to an RGB color (0, 170, 170).

(123) FIGS. 4C to 4E represent images revealed I.sub.r1 to I.sub.r6 under different observation conditions.

(124) By changing the observation conditions, it is possible to pass from FIG. 4C to FIG. 4D and to FIG. 4E, thus giving the user the impression that the blocks of colors rotate mutually clockwise, especially that I.sub.r1 takes the place of I.sub.r2 which takes the place of I.sub.r4 which takes the place of I.sub.r6 and so on and so forth.

(125) In the example illustrated in FIGS. 4A to 4F, the blocks B.sub.1 to B.sub.g are distinct legions of the revealing raster 4 which do not intersect. It may be otherwise in particular on account of the manufacturing tolerances. The blocks B.sub.1 to B.sub.g may be in regions of the revealing raster 4 that intersect over less than 5% of the area of the revealing raster.

(126) As a variant illustrated in FIG. 5A, the opaque raster lines of the block B.sub.1 have a zone 11 in common with the opaque raster lines of the block B.sub.3. As a further variant illustrated in FIG. 5B, the opaque raster lines of the block B.sub.1 are disjoint from the opaque raster lines of the block B.sub.3.

(127) As a variant illustrated in FIG. 5C, the distance c.sub.12 between the last opaque raster line of the block B.sub.1 and the consecutive opaque raster line of the block B.sub.2 is equal to twice the width m of an opaque raster line.

(128) In the example illustrated in FIGS. 6A to 6D, the revealing raster 4 comprises sixteen blocks B.sub.1 to B.sub.16 each forming a sector of a disk. Each block B.sub.1 to B.sub.16 is adjacent to two blocks and all the blocks B.sub.1 to B.sub.16 join together at the center of the disk.

(129) The blocks B.sub.1, B.sub.2, B.sub.3 and B.sub.4 are mutually phase-shifted and the blocks B.sub.5, B.sub.9 and B.sub.13 are not phase-shifted with respect to the block B.sub.1, the blocks B.sub.6, B.sub.10 and B.sub.14 are not phase-shifted with respect to the block B.sub.2, the blocks B.sub.8, B.sub.12 and B.sub.15 are not phase-shifted with respect to the block B.sub.3 and the blocks B.sub.8, B.sub.12 and B.sub.16 are not phase-shifted with respect to the block B.sub.4 so that each of the blocks B.sub.1 to B.sub.16 is phase-shifted with respect to the three blocks B.sub.1 to B.sub.16 which follow it and which precede it when it is rotated clockwise.

(130) The opaque-raster lines 5a have a width m substantially equal to three-quarters of the width l of the interlaced-image lines.

(131) The block B.sub.1 is phase-shifted from the block B.sub.2 by a distance d.sub.12 equal to three-quarters of the width l of an interlaced image line i.sub.1 to i.sub.4, the block B.sub.1 is phase-shifted from the block B.sub.3 by a distance d.sub.13 equal to three-halves of the width l of an interlaced image line i.sub.1 to i.sub.4 and the block B.sub.1 is phase-shifted from the block B.sub.4 by a distance du equal to nine-quarters of the width l of an interlaced image line i.sub.1 to i.sub.4.

(132) The revealed images I.sub.r1 to I.sub.r16 form a disk composed of 16 sectors each formed by a revealed image I.sub.r1 to I.sub.r16, each sector being situated between sectors of different colors. Thus, as illustrated in FIG. 6B, if the interlaced image I.sub.r1 exhibits interlaced image proportions (1; 0.25; 1), i.e. an RGB color of about (191, 48, 191), then the interlaced image I.sub.r2 exhibits proportions (0.5; 0.75; 1), i.e. an RGB color of about (95, 143, 191), the interlaced image I.sub.r3 exhibits proportions (0.5; 1; 0.75), i.e. an RGB color of about (95, 191, 143) and the interlaced image I.sub.r4 exhibits proportions (1; 1; 0.25), i.e. an RGB color of about (191, 191, 48).

(133) FIGS. 6B to 6D represent images revealed I.sub.r1 to I.sub.r16 under different observation conditions.

(134) Thus, by changing the observation conditions, it is possible to pass from FIG. 6B to FIG. 6C and to FIG. 6D, thus giving the user the impression that the blocks of colors are rotating clockwise.

(135) In the example illustrated in FIGS. 7A to 7C, the revealing raster 4 comprises four blocks B.sub.1 to B.sub.4 of various shapes. The block B.sub.2 represents the digit 1, the blocks B.sub.3 and B.sub.4 represent the digit 0 and the block B.sub.1 is a rectangular block in which the other blocks are inserted. All the blocks B.sub.1 to B.sub.4 are mutually phase-shifted.

(136) The images are schematic for illustration purposes, however during the observation of the revealing raster alone illustrated in FIG. 7A, the pattern 100 is not distinguishable at a normal observation distance, of between 30 cm and 10 cm and preferably 15 cm.

(137) The opaque raster lines 5a have a width m substantially equal to three-quarters of the width l of the interlaced image lines just as in the example of FIGS. 6A to 6D.

(138) The revealed images I.sub.r1 to I.sub.r4 form the number 100 on a colored background, the colors of all the digits being different.

(139) FIGS. 7B to 7C represent images revealed I.sub.r1 to I.sub.r4 under different observation conditions.

(140) Thus, by changing the observation conditions, it is possible to pass from FIG. 7B to FIG. 7C and to observe a change of color of the number 100.

(141) In the variant illustrated in FIG. 10, at least two blocks B.sub.i and B.sub.j have opaque raster lines of different respective widths m.sub.i and m.sub.j. Thus, when the revealing raster is superposed with the combined image so that its general orientation is the same, the transparent raster lines 5b of the block B.sub.i do not unveil the same proportion of the interlaced image lines (P.sub.1; . . . ; P.sub.n) as that of the block B.sub.j and therefore the images revealed I.sub.ri and I.sub.rj respectively by the blocks B.sub.i and B.sub.j do not exhibit the same proportion (P.sub.1; . . . ; P.sub.n) of interlaced images. In the case illustrated of a rasterized and colored combined image, for example with red, green and blue lines, the revealed images I.sub.r1 to I.sub.rg of the blocks of widths m.sub.1 to m.sub.g are of different colors.

(142) In the variant illustrated in FIGS. 11A and 11B, two blocks B.sub.i and B.sub.j of one and the same revealing raster 4 are at least partially superposed. Their superposition defines a sub-block 15 having the form of a raster formed by the interleaving of the raster lines 5a and 5b of the blocks B.sub.i and B.sub.j. The raster of the sub-block 15 may exhibit: (i) as illustrated in FIG. 11A, when the opaque raster lines 5a of the blocks B.sub.i and B.sub.j are superposed or have an edge in common, a periodic alternation of period Q of an opaque raster line 15a and of a transparent raster line 15b, the opaque raster line having a thickness greater than or equal to that of the raster lines of each of the blocks of which it is formed, or (ii) as illustrated in FIG. 11B, when the opaque raster lines 5a of the blocks B.sub.i and B.sub.j are disjoint, a periodic alternation of period Q of four alternately opaque 15a and transparent 15b raster lines.

(143) Each sub-block 15 allows the observation of a revealed image I.sub.r by superposition with the combined image. In the case (i), the revealed image is of the same shape as for a block having an opaque raster line of the same width and in the case of the image (i.sub.i), the revealed image obtained depends on the position and on the width of the raster lines 15a and 15b.

(144) As a further variant, such as illustrated in FIGS. 12A and 12B, each interlaced image I.sub.1, I.sub.2, . . . , I.sub.n forms a periodic, for example such as represented in FIG. 12A, pattern and the transparent raster lines 5b are of width k equal to the width l of an interlaced image line. Thus, the image revealed by each block B.sub.1 to B.sub.g corresponds to one of the interlaced images and may allow, as illustrated in FIG. 12B, the observation of at least one periodic pattern of the revealed interlaced image. At least two of the blocks B.sub.1 to B.sub.g allow the simultaneous observation of two different interlaced images, especially of two different periodic patterns. A change of the observation conditions may make it possible to observe successively the various interlaced images, and this may make it possible to give a motion effect when the interlaced images each represent the decomposition of a motion.

(145) In the example of FIGS. 12A and 12B, the combined image I comprises four interlaced images I.sub.1, I.sub.2, I.sub.3 and I.sub.4 each representing a pattern M.sub.1, M.sub.2, M.sub.3 and M.sub.4, such as represented in FIG. 12A, which repeats periodically along the axis X and along the axes of the interlaced image lines i.sub.1, i.sub.2, i.sub.3 and i.sub.4. The combined image I therefore represents the pattern M, such as represented in FIG. 12A, which repeats periodically along the axis X and along the axes of the interlaced image lines i.sub.1, i.sub.2, i.sub.3 and i.sub.4. The interlaced image lines i.sub.1, i.sub.2, i.sub.3 and i.sub.4 are discontinuous. The revealing raster 4 of a rectangular shape comprises eight rectangular blocks B.sub.1 to B.sub.8, the blocks B.sub.1, B.sub.2, B.sub.3 and B.sub.4 being mutually phase-shifted and the block B.sub.1 not being phase-shifted with respect to the block B.sub.8, the block B.sub.2 not being phase-shifted with respect to the block B.sub.5, the block B.sub.3 not being phase-shifted with respect to the block B.sub.6 and the block B.sub.4 not being phase-shifted with respect to the block B.sub.7. Each of the blocks B.sub.1 to B.sub.8 makes it possible to reveal an interlaced image, the blocks B.sub.1 to B.sub.8 making it possible to each reveal one of the patterns M.sub.1, M.sub.2, M.sub.3 and M.sub.4.

(146) As a variant, the combined image I illustrated in FIG. 37A comprises blocks C.sub.1 to C.sub.3 and the revealing raster 4 is in the form of a single block.

(147) The blocks of the combined image are each such as described in conjunction with FIG. 1.

(148) The combined-image blocks C1 to C3 are rectangular in shape. The blocks C.sub.1 and C.sub.2 are mutually phase-shifted by a width l of an interlaced image line and the blocks C.sub.1 and C.sub.3 are not mutually phase-shifted.

(149) The revealing raster exhibits opaque raster lines 5a exhibiting a width m equal to the width l of a line i.sub.1 to i.sub.3 of interlaced images.

(150) During the superposition of the revealing raster 4 and of the combined image I, such as illustrated in FIG. 37B, the revealed images I.sub.r1 and I.sub.r3 are composed of the totality of the red and blue lines and therefore exhibit a proportion (1; 0; 1) of the interlaced images and the revealed image I.sub.r2 is composed of the totality of the red and green lines and exhibits a proportion (1; 1; 0) of the interlaced images.

(151) By changing the observation conditions, especially by displacing the revealing raster with respect to the combined image in the direction X or by changing the angle of observation, the revealed images I.sub.r1 to I.sub.r3 change by passing for example from FIG. 37B to FIGS. 37C and 37D.

(152) Observation by Superposition on Either Side of a Support

(153) Represented in FIG. 13 is a first embodiment in which a secure item 10 according to the invention comprises a non-opaque, for example perfectly transparent, substrate 20 having a first face 20a carrying the combined image I. The second face 20b of the substrate 2, opposite to the first face, carries the revealing raster 4.

(154) When the secure item 10 is observed from one side or from the other of the substrate, the revealing raster 4 makes it possible to observe one or more revealed images I.sub.r. By changing the angle of observation , the user changes the observation conditions and the revealed image or images I.sub.r are modified as described previously.

(155) To be able to view all the interlaced images up to an angle of inclination of about 45, the thickness e of the substrate is, preferably, greater than or equal to approximately the period Q.

(156) It may be advantageous to have a substrate whose thickness e is less than or equal to 30 m, better 25 m, for example lying between 20 and 30 m, or indeed 20 and 25 m, bounds included or excluded.

(157) Another possibility for varying the direction of observation of the secure item may be to deform the substrate, for example around a fold axis, as illustrated in FIG. 14.

(158) As a function of the pattern of the revealing raster 4, a tagging of the latter with respect to the combined image I may be necessary in the sense parallel to their general orientation. For example, for a linear revealing raster such as illustrated in FIG. 2, no tagging is necessary; on the other hand, for an undulated raster, a more or less precise tagging, as a function of the amplitude and of the frequency of the undulations, may turn out to be desirable. The invention thus offers a possibility of securing that can be modulated as a function of the protection sought and of the difficulty of implementation.

(159) For secure items comprising a thread introduced as window(s), the combined image I may be obtained by micro-photolithography of the thread and the revealing raster 4 may be produced with the help of offset printing with inks crosslinking under UV, performed subsequently when printing the item.

(160) The revealing raster 4 may be associated, if relevant, with a printing pattern of the item.

(161) The pattern of the revealing raster 4 may be printed otherwise than by superposition with the combined image I, on the item, to the same scale or to a different scale.

(162) The printing of the revealing raster 4 may overrun the combined image I and extend over the secure item 10, as illustrated in FIG. 15.

(163) Several revealing rasters and combined images, having for example the form of small squares or rectangles with sides of a few millimeters, may be present in one and the same security thread 30, as illustrated in FIG. 16.

(164) When the revealing raster 4 and the combined image I are on a thread integrated as window(s), as illustrated in FIGS. 17A and 17B, the secure item 10 may comprise at least two windows 31 and 32 making it possible to observe respectively each of the faces of the thread, in reflection.

(165) The item may comprise at the level of the windows 31 and 32 material voids and transparent regions 35 and 36 allowing the observation of the revealed images from both sides of the secure item 10.

(166) The interlaced images are observable through the revealing raster 4 from the window 31 side and with the revealing raster as background, from the window 32 side.

(167) The item 10 may also comprise a through window 31, as represented in FIG. 17D, the revealing raster 4 and the combined image I being situated at least partially in this through window. In this way, it is possible to observe the revealed images at one and the same time from the recto side and from the verso side of the secure item 10.

(168) The revealing raster 4 and the combined image in the form of a security thread may further be incorporated into a secure item 10 which exhibit an alternation of windows 31 and 32 recto side and verso side, as illustrated in FIG. 17C. It is thus possible to observe the revealed images at one and the same time on the recto side and on the verso side of the secure item 10 at the level of the windows 31 and 32, and especially on account of the presence of the material voids and the transparent regions 35 and 36.

(169) Represented in FIG. 18 is an exemplary secure item 10 comprising a perforation 40 in which two sub-elements, especially in the form of foils or patches, 41 and 42, are at least partially placed.

(170) The sub-element 41 comprises for example a revealing raster 4 and the sub-element 42 comprises for example the corresponding combined image I.

(171) The sub-elements 41 and 42 may be at least partially superposed on the boundaries of the perforation 40 with or without a thickness compensation.

(172) The sub-elements 41 and 42 may be at least partially transparent or translucent.

(173) The observation of the revealed images may be done by observation in reflection or in transmission, for example with the aid of a light source situated behind the item 10 during observation.

(174) In the variant illustrated in FIG. 19, the secure item 10 comprises a combined image I produced in the form of prints. The prints are for example produced on the surface of the secure item 10. Moreover, a sub-element 43, especially in the form of a foil or patch, is placed on the prints constituting the combined image I, the sub-element 43 comprising the corresponding revealing raster 4, for example produced on the surface of the sub-element 43.

(175) The secure item 10 may or may not be opaque. The secure item 10 may be at least partially transparent or translucent to allow observation of the interlaced images, especially on the combined image I side.

(176) In the examples of FIGS. 18 and 19, the revealing rasters 4 and/or the combined images I could be produced differently, being for example incorporated or situated above or below the sub-elements 41, 42 and 43.

(177) As a variant, the combined image comprises two metallizations of various colors, each corresponding to an interlaced image, especially a copper interlaced image and an aluminum interlaced image.

(178) As a further variant, the combined image comprises at least two metallizations, especially of the same color, of various optical densities and each corresponding to an interlaced image, thus creating a glossiness contrast.

(179) The aluminum interlaced image may be of high optical density, thereby giving it a glossy aspect.

(180) The revealing raster 4 may be of matt aspect.

(181) Superposition of the combined image I and of the revealing raster 4 makes it possible to obtain according to the blocks B.sub.1 to B.sub.g, matt or glossy revealed images I.sub.r1 to I.sub.rg. A displacement of the revealing raster 4 with respect to the combined image I along the axis X may make it possible to invert the aspect of the revealed images I.sub.r1 to I.sub.rg at the level of the various blocks B.sub.1 to B.sub.g, that is to say that the revealed images I.sub.r1 to I.sub.rg which were glossy may become matt and vice versa.

(182) Observation by Folding the Document or Superposing the Document and Another Object

(183) In a second embodiment, illustrated in FIG. 20, the secure item 10 comprises a window 50, preferably at least partially transparent, in which the revealing raster 4 is featured. The item 10 also comprises a combined image I carried on the item 10, for example by printing, especially copper-plate printing, offset printing or metallization and/or demetallization. The region in which the combined image 2 is featured may also be at least partially transparent.

(184) To observe the revealed image, the user must therefore fold the secure item 10, as illustrated in FIG. 21, to bring the revealing raster 4 onto the combined image I so that their general orientation is the same and then observe the revealed image or images I.sub.r. Thus, the revealed images are not visible when the item 10 is not folded and an action by the user, namely folding the secure item 10, is necessary in order to make them appear.

(185) In FIG. 22, the secure item 10 comprises a window 50, preferably at least partially transparent, in which the combined image I is featured. The item 10 also comprises a patch 55 comprising for example holographic prints and in which the revealing raster 3 is featured. The patch 55 may also be at least partially transparent.

(186) The patch 55 may comprise metallizations and/or demetallizations, made for example of aluminum, and the revealing raster 4 may comprise holographic prints and/or metallizations and/or demetallizations.

(187) In FIG. 23, the item 10 comprises a window 50, preferably at least partially transparent, on which the revealing raster 4 is featured. The item 10 also comprises a security thread 60 on which the combined image I is featured. The security thread 60 may also be at least partially transparent or comprise a partially transparent region at the level of the combined image I.

(188) Represented in FIGS. 24 to 28 are other examples of secure items 10 according to the invention comprising a combined image I and a revealing raster 4 in accordance with those of FIGS. 20 to 22, the combined image I and/or the revealing raster 4 being carried by at least one security thread or foil.

(189) In FIG. 24, the item 10 comprises a security thread 60 of a sufficient width to cause combined images I and revealing rasters 4 to be featured in alternation. Advantageously, the security thread 60 is at least partially transparent or exhibits one or more at least partially transparent regions at the level of the combined images I and/or of the revealing rasters 4.

(190) In FIG. 25, the item 10 comprises a security thread 60 on which a revealing raster 4 is featured. The item 10 also comprises a combined image I, for example in the form of an offset print on the item 10.

(191) The security thread 60 may be at least partially transparent or exhibit an at least partially transparent region. The item 10 may also comprise an at least partially transparent region at the level of the combined image I.

(192) In FIG. 26, the item 10 comprises two security threads 60a and 60b. The security thread 60a comprises three combined images I and the security thread 60b comprises three revealing rasters 4.

(193) The security thread 60a and/or the security thread 60b may be at least partially transparent or comprise at least one at least partially transparent region, especially at the level of a combined image I or of a revealing raster 4.

(194) In FIG. 27, the item 10 comprises a foil 70 on which an alternation of combined images I and of revealing rasters 4 is featured.

(195) The foil 70 may be at least partially transparent or comprise at least one at least partially transparent region at the level of a combined image I and/or of a revealing raster 4.

(196) In FIG. 28, the item 10 comprises a security thread 60 on which a combined image I is featured. The item 10 also comprises a patch 55, able to comprise holographic metallizations or otherwise, on which a revealing raster 4 is featured.

(197) The security thread 60 may be at least partially transparent or comprise an at least partially transparent region at the level of the combined image I.

(198) The patch 55 may also be at least partially transparent, especially at the level of the revealing raster 4.

(199) In all the examples described previously, the combined images I and the revealing rasters 4 may be swapped.

(200) The at least partially transparent regions may be situated at the level of the combined images I or of the revelation means 4, or at the level of both at one time.

(201) The security thread or threads 60, 60a and 60b may be introduced into the secure item 10 in a conventional manner, for example at the surface, bulk-wise or as window(s).

(202) The authentication of the items 10 may be done by folding them 10 lengthways or widthways so as to at least partially superpose the combined images I and the revealing rasters 4, and then by displacing relative to one another so as to view for example the illusion of a motion and/or by modifying the angle of observation of the combined images I and of the revealing rasters 4 superposed.

(203) As a further variant, it is also possible to superpose the item 10 at least partially with another similar item, such as described previously.

(204) Two Revealing Rasters Exhibiting Blocks

(205) As illustrated in FIGS. 29A to 29F, the item or the assembly may comprise two revealing rasters 4a and 4b such as described previously, superposed with the same combined image I.

(206) The two revealing rasters are, preferably, of different general orientations O.sub.ta and O.sub.tb forming between them a non-zero angle , preferably lying between 0 and 180 bounds excluded, better between 10 and 30, for example here substantially equal to 20.

(207) The fact that the revealing rasters have different general orientations allows at given observation conditions that: when the combined image I is oriented with the general orientation O.sub.ta, the revealed images I.sub.r1a to I.sub.rga of the first revealing raster 4a at the level of the blocks B.sub.1a to B.sub.ga are visible and the revealed images I.sub.r1b to I.sub.rub of the second revealing raster 4b at the level of the blocks B.sub.1b to B.sub.ub are not visible on account of the presence of a Moir phenomenon, and when the combined image I is oriented with the general orientation O.sub.ta, the revealed images I.sub.r1b to I.sub.rub of the second revealing raster 4b are visible and the revealed images I.sub.r1a to I.sub.rga of the first revealing raster 4a are not visible on account of the presence of a Moir phenomenon.

(208) Thus, according to the orientation of the combined image I with respect to the revealing rasters 4a and 4b, one or the other or none of the revealed images is visible, thereby affording the possibility of increased security.

(209) To observe the images revealed by one or the other of the rasters, the user must therefore superpose the combined image I and the revealing rasters 4a and 4b by folding the item 10 or superposing the item 10 and another object and rotate the combined image I with respect to the revealing rasters 4a and 4b. The user may also displace them with respect to one another along an axis X perpendicular to the general orientation of the combined image to observe a change of the revealed image or images of one of the rasters.

(210) The two revealing rasters 4a and 4b may or may not be separated from one another. Preferably, the revealing raster 4b is an inclusion in the revealing raster 4a.

(211) In the example illustrated in FIG. 29B, the first revealing raster 4a is of square shape and is formed of 17 blocks B.sub.1a to B.sub.17a, in particular a central block B.sub.1a of substantially square shape framed by 16 lateral blocks B.sub.2a to B.sub.17a likewise of square shape. 12 lateral blocks B.sub.2a to B.sub.13a are juxtaposed all around the central block B.sub.1a to form a square of width equal to twice the width of the central block B.sub.1a and 4 lateral blocks B.sub.14a to B.sub.17a are each totally superposed with two of the 12 lateral blocks B.sub.2a to B.sub.13a respectively with the blocks B.sub.3a and B.sub.4a, B.sub.6a and B.sub.7a, B.sub.9a and B.sub.10a, and B.sub.12a and B.sub.13a. The blocks B.sub.1a to B.sub.17a are all of substantially square shape. The lateral blocks B.sub.2a to B.sub.17a are of width substantially equal to half the width of the central block B.sub.1a. Superposition of the lateral blocks B.sub.14a to B.sub.17a with the other lateral blocks B.sub.2a to B.sub.13a allows the formation of 8 sub-blocks such as described previously. Each lateral block B.sub.2a, to B.sub.13a is phase-shifted with respect to the lateral block B.sub.2a to B.sub.13a which precedes it and which follows it. The lateral blocks B.sub.2a, B.sub.5a, B.sub.8a, and B.sub.11a forming the corners of the revealing raster 4 are not mutually phase-shifted and are not phase-shifted with respect to the central block B.sub.1a.

(212) The second revealing raster 4b is of rectangular shape and it is formed of 4 blocks B.sub.1b to B.sub.4b of various shapes. The block B.sub.2b represents the digit 1, the blocks B.sub.3b and B.sub.4b represent the digit 0 and the block B.sub.1b is a rectangular block in which the other blocks are inserted. The blocks B.sub.2b to B.sub.4b are not mutually phase-shifted but are phase-shifted with respect to the block B.sub.1b.

(213) The two revealing rasters 4a and 4b have different respective general orientations O.sub.ta, and O.sub.tb and form between them an angle substantially equal to 20.

(214) The opaque raster lines 5a have a width m substantially equal to three-quarters of the width l of the interlaced image lines just as in the example of FIGS. 6A to 6D.

(215) The revealing rasters 4a and 4b are superposed with the same combined image I, illustrated in FIG. 29A.

(216) As visible in FIGS. 29C and 29D, when the combined image is oriented in the same direction as the first revealing raster 4a, the blocks B.sub.1a to B.sub.17a cause revealed images I.sub.r1a to I.sub.r21a to appear, forming a central square I.sub.r1a surrounded by smaller squares I.sub.r2a to I.sub.r21a of various colors. The color of the small squares I.sub.r2a, I.sub.r5a, I.sub.r8a and I.sub.r11a in the corners is the same as that of the central square I.sub.r1a. The second revealing raster 4b does not form any visible image on account of a Moir phenomenon between the lines of the second revealing raster 4b and the lines of the combined image I.

(217) FIGS. 29C and 29D represent images revealed under different observation conditions but still with the same orientation of the revealing rasters 4a and 4b and of the combined image. The color of the revealed images changes.

(218) As visible in FIGS. 29F and 29G, when the combined image is oriented in the same direction as the second revealing raster 4b, the revealed images I.sub.r1b to I.sub.r4b form the number 100 on a colored background, the colors of all the digits being identical. The first revealing raster 4a does not form any visible image on account of a Moir phenomenon between the lines of the first revealing raster 4a and those of the combined image I.

(219) FIGS. 29D and 29G represent images revealed under different observation conditions from those of the respective FIGS. 29C and 29F but respectively still with the same orientation of the revealing rasters 4a and 4b and of the combined image. The color of the revealed images changes.

(220) As illustrated in FIG. 29E, the superposition of the revealing raster 4 and of the combined image I may be done by folding the secure item 10 and the change of orientation may be done by rotating the part of the secure item 10a carrying the combined image I with respect to the part of the secure item 10b carrying the revealing raster 4.

(221) Imager

(222) Represented in FIGS. 30 to 32 are examples of association between a secure item 10 and an electronic imager 100 making it possible to form the revealing raster 4 or the combined image I.

(223) In FIG. 30, the electronic imager 100 is for example a computer screen on which a first image 110 is displayed, the first image 110 being the revealing raster 4 or the combined image I.

(224) The secure item 10 is for example in the form of a banknote and comprises a second image 120, the second image being the revealing raster 4 if the first image is the combined image and vice versa.

(225) The secure item 10 is placed on the screen of the electronic imager 100 in such a way as to superpose the first image 110 at least partially with the second image 120 so as to observe the revealed image or images I.sub.r and deduce therefrom an authentication and/or identification piece of information in respect of the secure item 10.

(226) The secure item 10 may be displaced relative to the screen of the electronic imager 100 or the observer may change angle of observation to allow the observation of a change of the revealed image or images I.sub.r.

(227) As a variant, the secure item 10 remains immobile with respect to the screen of the electronic imager 100 and the first image 110 is animated with a motion on the screen, for example a translation, for example with the aid of a program activated or not by the user.

(228) In FIG. 31, the electronic imager 100 is for example in the form of a digital projector, projecting a first image 110 onto a background 150, for example the wall of a room.

(229) The secure item 10 comprising the second image 120 may then be at least partially superposed with the first image 110 projected onto the background 150 to allow observation of the revealed image or images I.sub.r.

(230) In FIG. 32, the electronic imager 100 is a projector which projects the first image 110 directly on the secure item 10.

(231) The first image 110 may, as in the example of FIG. 32, be projected, for example in the form of a W, on a region of the secure item 10 where the second image 120 is not present. Next, the secure item 10 is for example folded on itself in such a way as to superpose the second image 120, for example in the form of an A, with the first image 110 projected by the electronic imager 100. The part of the secure item 10 comprising the second image 120 may in particular be folded down onto the part comprising the first image 110, this part remaining immobile, in such a way that the first image 110 is situated between the imager 100 and the second image 120.

(232) In a variant, not represented, the first image 110 is projected directly on the second image 120 of the item 10. In particular, the projection of the first image 110 on the second image 120 of the item 10 may allow an at least partial superposition of the first and second images. Next, the electronic imager 100 may be displaced relative to the item 10 so as to displace the revealing raster 4 with respect to the combined image I.

(233) Represented in FIG. 33 is a variant embodiment in which the electronic imager 100 is a screen displaying several first images 110a, 110b, 110c and 110d.

(234) The first images 110a to 110d may have different properties, for example different shapes, colors, dimensions, raster elements.

(235) Advantageously, the first images 110a to 110d are differentiated in such a way as to allow one of them at least to be associated with at least one second image 120 present on an item 10. In this way, it is for example possible to authenticate and/or identify a greater diversity of items 10 having different respective second images, corresponding to the various first images 110a to 110d.

(236) As a variant, the item 10 comprises several different second images 120, as may be seen for example in FIG. 16, and the electronic imager 100 produces one or more first images 110. In this way, it is possible to authenticate and/or to identify a given security item 1 on a greater diversity of different electronic imagers, and especially with electronic imagers having different resolutions. In this way, the two aforementioned advantages may be brought together.

(237) The electronic imager 100 may display one or more indicators 140a, 140b, 140c and 140d making it possible to advise the user on the way to position the item 10 represented in FIG. 34 with respect to the imager.

(238) In particular, the indicators 140a to 140d may make it possible to know where to position the top right corner of the item 10, so as to correctly superpose a second image 120 of an item 10 with a first image 110a, 110b, 110c or 110d displayed on the screen of the electronic imager 100.

(239) The item 10 may comprise an integrated microcircuit 152, for example an RFID or optical chip, making it possible to communicate with the electronic imager 100 so as to control the display of an indicator such as described previously or to disseminate a piece of information on the way to position the first and second images.

(240) As a variant, the chip 152 is able to communicate with the electronic imager 100 so as to make it possible to produce the first image 110 associated with the second image 120.

(241) In particular, during the method for authenticating and/or identifying the item 10, the second image 120 is illuminated with the electronic imager 100. The chip 152 comprises a piece of information transmitted to the electronic imager 100 which then projects or displays the first image 110 as a function of this piece of information.

(242) The item 10, especially the second image 120, may be photographed and/or filmed by a digital camera belonging or linked to the electronic imager 100. A recognition program may then make it possible to recognize the second image 120 and to acquire from a database a first image 110 associated with the second image 120. The database is for example stored on a secure server. The first image 110 thus obtained is displayed and/or projected by the electronic imager 110 so as to make it possible to authenticate and/or to identify the item 10.

(243) In the variant illustrated in FIG. 35, the electronic imager 100 takes the form of a mobile telephone on which is displayed a first image 110 in the form of a combined image I. The item 10 comprises a polarizing filter on which the second image 120 has been formed in the form of a revealing raster 4. The item 10 comprising the second image 120 in the form of a revealing raster 4 is superposed with the first image 110 in the form of a combined image I produced by the electronic imager 100, the latter emitting polarized light.

(244) The item 10 comprising the revealing raster 4 may be displaced by a translation motion along the axis X with respect to the combined image I displayed by the screen of the electronic imager 100, in such a way as to change the revealed image or images I.sub.r.

(245) Such a method makes it possible to authenticate and/or to identify the security item 1 according to several security levels.

(246) The positioning of the revealing raster 4 comprising the polarizing filter according to the orientation making it possible to observe the opacity of the polarizing filter, this observation being visible only on a screen emitting a polarized light, for example a screen of the LCD type, affords a first level of security.

(247) The revealing of the animation of the revealed images by displacement of the revealing raster 4 relative to the combined image I affords a second level of security.

(248) As a further variant, the electronic imager 100 is a screen, especially of the LCD type, comprising a plurality of pixels preferably forming a combined image, for example such as described in FIG. 36A.

(249) The invention is not limited to the examples illustrated. The secure item may be produced with other securities of first, second or third level, for example.

(250) The expression comprising a should be understood as being synonymous with comprising at least one.