Marking method and system

Patent metadata

Field	Value
Publication number	US-2020233377-A1
Application number	US-201816652081-A
Country	US
Kind code	A1
Filing date	Oct 16, 2018
Priority date	Oct 17, 2017
Publication date	Jul 23, 2020
Grant date	—

Abstract

A method and system for forming a holographic structure in a material. The holographic structure is configured to project a selected target image in the far field under illumination of the holographic structure by a laser. The method calculates a modified design for the holographic structure that encodes a unique identifier within the holographic structure for projecting the target image. The method modifies the material by mapping features corresponding to the modified design into the material so as to form the holographic structure. A basic check of the authenticity of the material is performed by checking whether a projected replica of the target image is as expected. A more detailed check of the authenticity of the material is performed by directly inspecting the features in the holographic structure.

First claim

1 - 42 . (canceled)

43 . A method for forming a holographic structure in a material, the holographic structure being configured to project a target image in the far field under illumination of the holographic structure, the method comprising:
calculating a design for the holographic structure for projecting the target image; modifying the design to encode an identifier within the holographic structure for projecting the target image; and modifying the material by mapping features corresponding to the modified design into the material.

44 . The method of claim 43 , wherein the identifier encoded by the modified design is such that the identifier is substantially hidden, masked or otherwise substantially unidentifiable in the projected target image.

45 . The method of claim 43 , wherein at least one of calculating and/or modifying the design comprises using the identifier as part of an algorithm to calculate the modified design.

46 . The method of claim 43 , wherein calculating the design comprises calculating a map of phase and/or amplitude values for projecting the target image, wherein each feature of the design corresponds to one of the phase and/or amplitude values.

47 . The method of claim 46 , wherein modifying the design comprises calculating a map comprising at least one different phase and/or amplitude value such that the target image projected by the holographic structure based on the modified design is indistinguishable from the target image projected before modification of the design.

48 . The method of claim 46 , wherein calculating the map of phase and/or amplitude values for projecting the target image comprises: calculating a set or array of features that have associated phase and/or amplitude values for projecting the target image, wherein each feature is at a different position in the map, and each position in the map has one of at least two phase and/or amplitude values.

49 . The method of claim 43 , wherein at least one of: calculating; and modifying the design comprises:
obtaining an initial design of the holographic structure for projecting the target image; and selecting a different phase and/or amplitude value for at least one of the features to modify the design, the modified design projecting a target image that is indistinguishable from, or at least similar to, the target image projectable by the holographic structure corresponding to the initial design.

50 . The method of claim 49 , wherein the initial design (a) comprises a map of phase and/or amplitude values comprising at least one feature corresponding to the identifier; or (b) is a map of phase and/or amplitude values comprising at least one of: constant phase and/or amplitude values across at least part of the map; random phase and/or amplitude values across at least part of the map; and a defined pattern of phase and/or amplitude values across at least part of the map.

51 . The method of claim 43 , wherein the identifier comprises an initial seed for deterministically generating a map of the features for the design.

52 . The method of claim 43 , comprising selecting at least one portion of the design and swapping the selected portion(s) with at least one other portion of the design.

53 . The method of claim 52 , comprising verifying whether the modified design of the holographic structure is configured to project a target image that is indistinguishable from, or at least similar to, the target image projected by a holographic structure corresponding to the unmodified design.

54 . The method of claim 52 , wherein the selected portion and the at least one other portion are portions that, individually project substantially the same or similar target image but that comprise or represent maps that are at least partially different.

55 . The method of claim 54 , comprising generating the map comprised in or represented by the selected portion using a first seed and/or first number of iterations and generating the map comprised in or represented by said at least one other portion using a second, different seed and/or a second, different number of iterations.

56 . The method of claim 43 , comprising modifying the material by at least one of: (a) changing a level of a surface of the material; (b) modifying a refractive index of the material; and (c) using radiation to at least one of: melt, ablate, move, deposit, or otherwise distribute the material; and change a chemical property of the material.

57 . A product comprising a holographic structure for projecting a target image in the far field under illumination of the holographic structure, the holographic structure comprising:
features based on a modified design that encodes an identifier within the holographic structure for projecting the target image, wherein the identifier encoded by the modified design is preferably such that the identifier is hidden, masked or otherwise unidentifiable in the projected target image.

58 . A computer program product that when executed by a processing system or control unit causes the processing system or control unit to at least partially implement the method of claim 43 .

59 . A system for forming a holographic structure in a material, comprising:
a control system for carrying out the method of claim 43 to modify a design for the holographic structure; and a laser system for modifying the material according to the design.

60 . A method for determining an authenticity of a material comprising a holographic structure formed by the method of claim 43 , the method comprising:
inspecting at least part of the holographic structure to determine a design of the holographic structure; and comparing the inspected design with an expected design.

61 . A computer program product that when executed by a processing system or control unit causes the processing system or control unit to at least partially implement the method of claim 60 .

62 . A system for determining an authenticity of a material comprising a holographic structure formed by the method of claim 43 , comprising:
an inspection system for inspecting a design of the holographic structure; and a comparison system for comparing the inspected design with an expected design.

Assignees

• Renishaw Plc

Inventors

• Weston Nicholas John
• Hand Duncan Paul
• Wlodarczyk Krystian Lukasz

Classifications

• G06K19/06065

  the marking being at least partially represented by holographic means (holographic marking in general, see G06K19/16) · CPC title

• G03H1/0236

  Form or shape of the hologram when not registered to the substrate, e.g. trimming the hologram to alphanumerical shape (substrates bearing a hologram G03H1/0272) · CPC title

• G03H2240/11

  Phase only modulation (G03H1/0244 takes precedence) · CPC title

• G03H1/0808

  Methods of numerical synthesis, e.g. coherent ray tracing [CRT], diffraction specific · CPC title

• G03H1/0891

  Processes or apparatus adapted to convert digital holographic data into a hologram (G03H1/2294 takes precedence) · CPC title