Abstract
The present invention relates to a labeling element for items, which on a surface thereof is formed with a plurality of pixels with periodic lattice structures, in particular linear lattice structures. Lattice structures with in each case one structural period A and an alignment of the structural elements, which are aligned to one another in particular in a linear parallel manner, at an angle φ with respect to an axis of reference are formed in individual pixels such that when the pixels constituting the labeling element are irradiated with electromagnetic radiation, preferably monochromatic electromagnetic radiation, an image of the labeling element is created on an detector array or a surface, by means of images of at least one order of diffraction of the electromagnetic radiation diffracted by pixels which can be used for identification of the respective labeling element.
Claims
1. Labeling element for items, which on a surface thereof is formed with a plurality of pixels (1.1 to 1.x) with periodic lattice structures, in particular linear lattice structures, and wherein lattice structures with in each case one structural period Λ and an alignment of the structural elements, which are aligned to one another in particular in a linear parallel manner, at an angle φ with respect to an axis of reference are formed in individual pixels (1.1 to 1.x) such that when the pixels (1.1 to 1.x) constituting the labeling element (2) are irradiated with electromagnetic radiation (3), preferably monochromatic electromagnetic radiation, an image (6) of the labeling element is created on an detector array (4) or a surface, by means of images of at least one order of diffraction of the electromagnetic radiation (3) diffracted by pixels (1.1 to 1.x) which can be used for identification of the respective labeling element (2).
2. Labeling element according to claim 1, characterized in that pixels (1.1 to 1.x) are present, which in each case additionally comprise a varying structural depth of the linear structural elements.
3. Labeling element according to claim 1, characterized in that the pixels (1.1 to 1.x) of one labeling element (2) are formed such that the labeling element (2) as such is not discernible on the surface of the item without using optical aids.
4. Labeling element according to claim 1, characterized in that the pixels (1.1 to 1.x) are embodied with a circular or polygonal shape.
5. Labeling element according to claim 1, wherein the individual pixels (1.1 to 1.x) each occupy a surface of 1 mm.sup.2 at a maximum, wherein the structured total area (i.e. the sum of all individual pixels) can be of an arbitrary size.
6. Labeling element according to claim 1, characterized in that at least a radiation source (5), in particular a laser diode for the electromagnetic radiation (3), a detector array (4) and/or a display for displaying the image (6) of the pixels (1.1 to 1.x) form a unit with the respective order of diffraction.
7. Labeling element according to claim 1, characterized in that the pixels (1.1 to 1.x) have a structural period Λ in the range of 0.01 μm to 50 μm and/or structural depths in the range of 0.001 μm to 10 μm.
8. Labeling element according to claim 1, characterized in that when the image (6) of diffracted electromagnetic radiation is created at least electromagnetic radiation of one order of diffraction is used.
9. Labeling element according to claim 1, characterized in that the pixels (1.1 to 1.x) are formed in at least one surface of the material (M2), which is covered by at least one other material (M1), or are formed within a boundary between the materials (M1 and M2), wherein the other material has a smaller absorption capacity, in particular an absorption capacity being smaller by at least 50%, for the laser radiation used for forming the pattern, compared to that of the material (M2) which is covered by the other material (M1).
10. Labeling element according to claim 9, characterized in that the at least one other material (M1) is a polymer, in particular a polymer film.
11. Labeling element according to claim 9, characterized in that the materials (M1 and M2) are integrally joined to one another, preferably with the aid of an organic binder.
Description
[0030] Hereinafter, the invention will be described exemplarily in greater detail.
[0031] In the drawings,
[0032] FIG. 1 schematically shows an example formed with pixels of a labeling element and a structure for verification of the identity of the labeling element;
[0033] FIGS. 2a-c schematically show the influence of different structural periods Λ and angles φ of the structural orientation at a position of an image of the respective pixel, which is diffracted at a pixel;
[0034] FIG. 3 shows the image of 10 pixels constituting a T-shaped labeling element in the first order of diffraction;
[0035] FIG. 4 shows examples in which a material is covered by another material at one or at both oppositely arranged surfaces;
[0036] FIG. 5 shows a diagram reflecting the optical transparency and thus conversely the absorption behavior as a function of the respective wavelength for a material M1 and another material M2;
[0037] FIGS. 6a+b are a schematic view of how two partial beams for creating pixels of a labeling element are directed onto the surface of a material M1 through another material M2;
[0038] FIGS. 7a+b schematically show the creation of structural elements at two opposite surfaces of a material which at both oppositely arranged surfaces is covered by another material;
[0039] FIG. 8 is a schematic view of structural elements for a labeling element with suitable dimensioning, which can be formed with the aid of direct laser interference structuring (DLIP), and
[0040] FIG. 9 is a schematic view of possibilities for arranging individual structural elements with pixels which can be employed using DLIP for the creation of a labeling element.
[0041] FIG. 1 shows an example of a labeling element 2 with nine pixels 1.1 to 1.9 in a plan view and in a side view. The pixels 1.1 to 1.9 each have been formed as a structured circular surface with respectively one linear lattice shape using DLIP. It can be seen from the plan view that the alignment of the lattice structures has been selected in different angles/orientations. Above the plan view as shown in FIG. 1, a correspondingly structured surface of an item is shown. Monochromatic electromagnetic radiation 3 from a laser diode serving as a radiation source 5 is directed onto said structured surface. The electromagnetic radiation diffracted and reflected at the structured surface of the pixels 1.1 to 1.9 constituting the labeling element 2 impinges on a detector array 4, with which the intensities can be detected in a spatially resolved manner. As is apparent from the upper representation in FIG. 1, images 6 can be detected in this way in several orders of diffraction. For the purpose of verification, it can be sufficient to consider merely one order of diffraction, preferably the 1.sup.st order.
[0042] The representation on the right in FIG. 1 renders apparent how the image 6 of the pixels 1.1 to 1.9 at the detector array 4 may look like. Thereby, after reflection and diffraction, imaging of the pixels 1.1 to 1.9 takes place by the respective selection of the structural period A and the angle φ for the alignment of the linear lattice structure of the individual pixels and at least one image 6 of the entire labeling element 2 can be considered in the 1.sup.st order of diffraction for a verification of authenticity. In this representation, two images 6 of the respectively 1.sup.st order of diffraction of the labeling element are shown.
[0043] The image(s) 6 correspond to the respectively given labeling element 2. The irradiation with electromagnetic radiation 3 can be carried out at different angles. Depending on the selected angle only the position of the entire image 6 changes.
[0044] The influence of a changed structural period Λ on a position of an image of an order is apparent from the representations in FIGS. 2a and 2b. Hence, the structural period Λ.sub.1 was larger than the structural period Λ.sub.2. The distance of the image of a pixel 1 after diffraction at the lattice structure from a zero point of a Cartesian coordinate system hence changes as a function of the respective structural period Λ in an axial direction.
[0045] It is clear from FIG. 2c that the angle φ, with which the linear lattice structure has been formed aligned with respect to an axis of a coordinate system, also has an influence on the position of the image of a pixel 1 after diffraction of electromagnetic radiation at the linear lattice structure. In the representations according to FIGS. 2a to 2c, the angle φ.sub.1 has a value of 90° with respect to an x axis of a coordinate system and the angle φ.sub.2 has a value of 135° with respect to the x axis of a coordinate system. This results in that the images of the orders of diffraction of one pixel 1 with the structural period Λ.sub.1 and an angle φ.sub.2 are not arranged on an axis on which the corresponding images of orders of diffraction with structural periods Λ.sub.1 and Λ.sub.2 and the angle φ.sub.1 are disposed. Hence, the respective positions of images of pixels can be influenced after the optical diffraction by a suitable selection of the structural period Λ and/or the angle φ of the individual pixels 1.
[0046] FIG. 3 shows a coordinate system, in which an image 6 of the 1.sup.st order of diffraction of 10 pixels resulted in a T-shaped labeling element 2. In the individual images of pixels, different values for the structural period Λ and angle φ have been selected in each case, so that each pixel is imaged respectively assigned to the respective labeling element after the diffraction at the desired position, and in this example, the labeling element 2 has the shape of a “T”. As a matter of course, by means of a varying the number of pixels, the arrangement of which on a surface, the respective selection of the structural period Λ and the angle φ of the respective linear lattice structure, labeling elements 2 with most varied configurations can be provided as well.
[0047] Hence, in the shown example, the structural period Λ in the range of 1.2 μm up to 1.6 μm and the angle φ in the range of 24° to 52° can be varied for individual pixels. The structural depth of linear lattice structures can be kept constant in the range of 0.001 μm to 10 μm, and thereby also for all pixels which are assigned to one labeling element 2.
[0048] FIG. 4 on the left shows an arrangement, in which a material M2 is covered by another material M1. The representation on the right shows an arrangement, in which a material M2 is covered by another material M1 at two opposite surfaces. A material can also be covered at two opposite sides by other materials, and the other materials are thereby different. In FIG. 4, the materials M1 and M2 are arranged directly above one another without any gap. However, an arrangement at a distance from one another is also possible. Thereby, materials can be fixed at outer surfaces with the aid of a frame.
[0049] The diagram shown in FIG. 5 reflects the differences of the wavelength-dependent transparency for electromagnetic radiation for different materials M1 and M2. Preferably, it is thus possible to use a wavelength, which is highlighted with the dashed line, for imaging a labeling element in a material M2.
[0050] FIGS. 6a and 6b show how the structural elements can be formed in the surface of a Material M2 using DLIP with individual pixels 1.1 to 1.3, while several partial beams 9 and 9′ can be simultaneously directed in a locally defined manner onto the surface of a material M2 through another material M1 covering this material. Thereby, the material M1 absorbs the electromagnetic laser radiation at the selected wavelength λ by at least 80%, preferably almost 100%, whereas the other material M1 does not absorb the electromagnetic radiation with the respective wavelength at all or by 40% at a maximum.
[0051] FIGS. 7a and 7b show how the pixels 1.1 to 1.6 have been formed at two oppositely arranged surfaces of a material M2 to form a labeling element. In this case, they form a nearly identical pattern, since they have been formed mirrored to the center axis of the material M2. However, an offset arrangement of pixels 1.1 to 1.3, 1.4 to 1.6 and 1.7 to 1.9 is likewise possible. This is indicated by the representations in FIG. 9 (on the left, symmetrical at a surface of a material M2, and at the right, offset to one another in rows at a surface or above one another at two surfaces of a material M2). It can be seen from FIG. 8 that individual pixels 1.1 to 1.3 can appropriately form structural elements 10 with a lateral dimensioning D in an axial direction with 2 μm to 20 mm with a distance A from one another of 0 nm to 20,000 μm, preferably of 100 nm to 50 μm. Individual pixels can be formed with a dimensioning Λ in the range of 100 nm to 50 μm.
