Holographic anti-counterfeiting structure

Abstract

This invention provides a holographic anti-counterfeiting structure, comprising a carrier and a phase modulation array. The phase modulation array is disposed on the carrier and includes a plurality of diffraction unit groups distributed in a three-dimensional spatial coordinate system. The phase modulation array controls the phase delay of incident light by modulating these diffraction unit groups. The distribution of some of these diffraction unit groups conforms to a random distribution function and is randomly distributed within the three-dimensional spatial coordinate system. Each diffraction unit group has a plurality of diffraction sub-units, each of which has a three-dimensional physical parameter. This three-dimensional physical parameter is the wavefront phase delay of each point in the three-dimensional coordinate space, calculated by treating a target image as a spatially coherent light source and inversely. This allows the incident light to undergo phase-constructive superposition at a preset focal point, thereby generating a holographic projection of the target image in the viewer's eye.

Claims

1. A holographic anti-counterfeiting structure, comprising: A carrier is a flat plate that can be attached to the surface of various products in the form of a label; And a phase modulation array, which is a microstructure with a three-dimensional phase modulation array, is stacked on the surface of the plane of the carrier, and the phase modulation array includes a plurality of diffraction unit groups distributed in a three-dimensional spatial coordinate system; the phase modulation array controls the phase delay of the incident light by modulating the diffraction unit groups; wherein the distribution of some of the diffraction unit groups conforms to a random distribution function and is randomly distributed in the three-dimensional spatial coordinate system; wherein each diffraction unit group has a plurality of diffraction sub-units, and each diffraction sub-unit has a three-dimensional physical parameter; the three-dimensional physical parameter is the wavefront phase delay of each point in a three-dimensional coordinate space, which is calculated inversely by treating a target pattern as a spatially coherent light source; wherein when the incident light enters the phase modulation array, it is recombined by the phase modulation array according to the phase delay; thereby, the incident light is phase-constructively superimposed at a preset focal point, thereby generating a holographic projection of the target pattern in the viewer's eye.

2. The holographic anti-counterfeiting structure as described in claim 1, wherein the target pattern is a combination of a plurality of sub-pattern arrays, each of which corresponds to a specific viewing angle range; the diffraction unit group performs spatial phase modulation on the incident light according to the three-dimensional physical parameters, so that the diffraction light field corresponding to the sub-pattern arrays is projected onto their respective viewing angle ranges, thereby enabling the complete image of the target pattern to be displayed simultaneously from a plurality of different viewing angles.

3. The holographic anti-counterfeiting structure as described in claim 1, wherein the phase modulation array controls the phase delay of incident light by modulating the refractive index distribution of the material comprising the diffraction subunits or by modulating the shape of the diffraction subunits.

4. The holographic anti-counterfeiting structure as described in claim 1, wherein the phase delay is calculated according to Equation 1, Equation 1: mλ=-D; where D is the physical phase compensation value provided by the diffraction sub-unit; m is a positive integer representing the diffraction order; λ is a preset wavelength; and represent the spatial geometric distance differences between the physical coordinates of any diffraction sub-unit and its focal point in the X-axis, Y-axis and Z-axis directions, respectively.

5. The holographic anti-counterfeiting structure described in any one of claims 1 to 4 is disposed in a matrix encoded information and obscures 7% to 30% of the matrix encoded information.

6. The holographic anti-counterfeiting structure as described in claim 5, wherein the phase modulation array comprises a first region and a second region, wherein the diffraction unit group located in the first region is used to generate a holographic projection having the target pattern, and the diffraction unit group located in the second region is used to form the matrix encoding information.

7. The holographic anti-counterfeiting structure as described in claim 6, wherein the matrix encoding information is composed of a plurality of encoded point elements representing binary logic and distributed in a two-dimensional plane of the three-dimensional spatial coordinate system; each of the encoded point elements has a physical structural variation to disrupt or change the amplitude reflectivity, transmittance or equivalent refractive index of a local region of the diffraction unit.

8. The holographic anti-counterfeiting structure as described in claim 5, wherein the size of a single pixel of the matrix-encoded information is between 5 micrometers and 20 micrometers, and its spatial distribution density is controlled by the random distribution function, so that it is coupled with the optical background noise generated by the phase modulation array.

9. The holographic anti-counterfeiting structure as described in claim 5, wherein the matrix-coded information is invisible to the naked eye under visible light, and the content of the matrix-coded information is only revealed when illuminated by a coherent light source of a specific wavelength and subjected to phase interference imaging.

10. The holographic anti-counterfeiting structure as claimed in claim 5, wherein the phase modulation array guides incident light to a plurality of focal planes of different depths, such that the text is reconstructed on a first focal plane and the pattern is reconstructed on a second focal plane having a different depth from the first focal plane.

11. The holographic anti-counterfeiting structure as described in claim 1, wherein the random number distribution function meets at least one of the following conditions: wherein the amplitude of the random displacement vector of each diffraction sub-unit relative to its preset periodic position does not exceed 25% of the average pitch of the phase modulation array; wherein the random displacement vector conforms to a uniform distribution or a Gaussian distribution; wherein the center distance between any two adjacent diffraction sub-units is greater than the characteristic size of any diffraction sub-unit.

12. The holographic anti-counterfeiting structure as described in claim 1, wherein the plurality of diffraction sub-units are disposed in a third region and a fourth region; wherein the diffraction sub-units disposed in the third region are arranged according to a periodic array, and the diffraction sub-units disposed in the fourth region are randomly distributed in accordance with the random number distribution function.

13. The holographic anti-counterfeiting structure as described in claim 1, wherein the plurality of diffraction sub-units are distinguished into a plurality of first diffraction sub-units having first microstructure features and a plurality of second diffraction sub-units having second microstructure features based on the physical topological differences of their microstructures; the first diffraction sub-units are used to reconstruct a first image with high brightness features, the second diffraction sub-units are used to reconstruct a second image with stereoscopic depth, and the first image and the second image constitute a target image with visual contrast.

14. The holographic anti-counterfeiting structure as described in claim 1, wherein the plurality of diffraction sub-units are distinguished according to the differences in their microstructure into a plurality of first diffraction sub-units having a first microstructure feature and a plurality of second diffraction sub-units having a second microstructure feature; the first diffraction sub-units are arranged in a geometrical arrangement of a rectangular grid or a hexagonal grid to generate discrete characteristic peak signals as optical positioning anchors of an optical reading device.

15. The holographic anti-counterfeiting structure as described in claim 13 or 14, wherein the first diffraction sub-units and the second diffraction sub-units are distributed together in the three-dimensional spatial coordinate system in a spatially staggered or superimposed manner.

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