Data Storage in a Diffractive Optical Element

• US 20100195174A1
• Filed: 01/16/2007
• Published: 08/05/2010
• Est. Priority Date: 01/16/2006
• Status: Abandoned Application

• Current Assignee: Securency International Pty., Ltd.
• Original Assignee: Securency International Pty., Ltd.
• Inventors: Power, Gary Fairless, Nemeth, Joshua Robert, Stewart, Robert
• Application Number:
  US12/161,036
• Publication Number:
  US 20100195174A1
• Time in Patent Office: Days
• US Class Current: 359/2
• CPC Class Codes: B42D 2033/04 Transparent material
• CPC Class Codes: B42D 25/00 Information-bearing cards or sheet-like structures characterised by identification or security features; Manufacture thereof printing processes to produce identification or security features B41M3/14
• CPC Class Codes: B42D 25/324 Reliefs
• CPC Class Codes: B42D 25/328 Diffraction gratings; Holograms
• CPC Class Codes: B42D 25/351 Translucent or partly translucent parts, e.g. windows
• CPC Class Codes: B42D 25/41 using electromagnetic radiation B42D25/435 takes precedence
• CPC Class Codes: B42D 25/435 using electromagnetic radiation, e.g. laser

Abstract

A diffractive optical element (DOE) and various methods of producing such a DOE are provided in which a diffractive optical microstructure is formed with encrypted data on at least one side of a transparent substrate or in a layer applied to the substrate. The diffractive optical microstructure when illuminated with collimated light, generates a far field interference pattern corresponding to the encrypted data which may be decrypted with suitable optical detectors and processing equipment.

Claims

1-41. -41. (canceled)

42. A diffractive optical element (DOE) comprising a diffractive microstructure which includes encrypted data stored within the microstructure of the DOE, wherein when the DOE is illuminated with substantially collimated light, the diffractive microstructure generates a far field interference pattern corresponding to the stored data that is reconstructed in a reconstruction plane remote from the DOE.

43. A security document or article which includes a diffractive optical element (DOE) in accordance with claim 42.

44. A security document or article according to claim 43 wherein the document is an identification document, and the encrypted data includes personalised data relating to the holder of the identification document.

45. A DOE, according to claim 42 wherein the encrypted data stored in the microstructure of the DOE is readable by apparatus including a detector located in the reconstruction plane and decryption means for decrypting the encrypted data.

46. A DOE, according to claim 45 wherein the DOE is also arranged to generate a projected visual image in the reconstruction plane when the DOE is illuminated with substantially collimated light.

47. A DOE, according to claim 46 wherein the projected visual image is generated by a first set of pixels or vector elements in the DOE and the encrypted data is stored in a second set of pixels or vector elements intertwined with the first set.

48. A method of storing and reading data in a document including the steps of:

providing a diffractive optical microstructure in the document wherein encrypted data is stored in the microstructure;

illuminating the diffractive optical microstructure with substantially collimated light whereby a far field interference pattern is generated corresponding to the encrypted data that is reconstructed in a reconstruction plane remote from the diffractive optical microstructure;

detecting the far field interference pattern in the reconstruction plane; and

decrypting the encrypted data detected in the reconstruction plane.

49. A method of storing and reading data according to claim 48 wherein the far field interference pattern is detected by detecting the light intensity of the interference pattern in the reconstruction plane.

50. A method according to claim 49 wherein encrypted data in the light intensity pattern is decrypted by a computer program which transforms the detected light intensity pattern into machine readable data.

51. Apparatus for reading encrypted data stored in a diffractive optical microstructure in a document wherein encrypted data is stored in the microstructure, the apparatus including:

means for directing a substantially collimated beam of light onto the diffractive optical microstructure such that the beam is transformed into a far field interference pattern corresponding to the stored encrypted data that is reconstructed in a reconstruction plane remote from the microstructure;

optical detection means located in the reconstruction plane for detecting the far field interference pattern and for generating signals representing the stored encrypted data; and

processing means for receiving and processing the signals from the optical detection means, wherein the processing means includes decryption means for decrypting the encrypted data represented by the signals from the detection means.

52. A method of producing a diffractive optical element (DOE) with encrypted data stored therein including the steps of:

providing a substrate which is transparent at least to visible light;

forming a diffractive optical microstructure on at least one side of the substrate or in a layer applied thereto;

whereas the diffractive optical microstructure is formed with encrypted data such that when the diffractive optical microstructure is illuminated with substantially collimated light a far field interference pattern representing the stored data is generated that is reconstructed in a reconstruction plane remote from the diffractive optical microstructure.

53. The method of claim 52 including the further steps of:

representing the diffractive optical microstructure as a two-dimensional field having predetermined dimensions;

subdividing the two-dimensional field into an array of discrete elements; and

determining the content of discrete elements of the field in order to form the encrypted data of the diffractive optical microstructure.

54. The method of claim 53 wherein each said discrete element is a pixel, whereby the data stored in the diffractive optical microstructure is a bitmap.

55. The method of claim 52 wherein the stored data is encrypted during a Fourier transform calculation for the creation of the diffractive optical microstructure.

56. The method of claim 52 further including the step of forming the diffractive optical microstructure such that when suitably illuminated a projected visual image is generated which is viewable in the reconstruction plane.

57. The method of claim 56 wherein the parts of the diffractive optical microstructure representing the encrypted data are intertwined with parts of the diffractive optical microstructure representing the visual image.

58. A diffractive optical element (DOE) comprising a diffractive microstructure which comprises a plurality of apertures formed in a substantially opaque layer disposed on a substrate which is transparent at least to visible light, wherein encrypted data is stored within the microstructure of the DOE, and wherein when the DOE is illuminated with substantially collimated light, the diffractive microstructure generates a far field interference pattern corresponding to the stored data that is reconstructed in a reconstruction plane remote from the DOE.

59. A method of producing a diffractive optical element (DOE) with encrypted data stored therein including the steps of:

providing a substrate which is transparent at least to visible light;

forming a diffractive optical microstructure comprising a plurality of apertures formed in a substantially opaque layer disposed on at least one side of the substrate;

whereas the diffractive optical microstructure is formed with encrypted data such that when the diffractive optical microstructure is illuminated with substantially collimated light a far field interference pattern representing the stored data is generated that is reconstructed in a reconstruction plane remote from the diffractive optical microstructure.

60. A method of storing and reading data in a document including the steps of:

providing a diffractive optical microstructure in the document, wherein the diffractive optical microstructure comprises a plurality of apertures formed in the document, or in a substantially opaque layer thereof; and

wherein encrypted data is stored in the microstructure;

illuminating the diffractive optical microstructure with substantially collimated light whereby a far field interference pattern is generated corresponding to the encrypted data that is reconstructed in a reconstruction plane remote from the diffractive optical microstructure;

detecting the far field interference pattern in the reconstruction plane; and

decrypting the encrypted data detected in the reconstruction plane.

61. Apparatus for reading encrypted data stored in a diffractive optical microstructure in a document, wherein the diffractive optical microstructure comprises a plurality of apertures formed in the document or in a substantially opaque layer thereof, and wherein encrypted data is stored in the microstructure, the apparatus including:

means for directing a substantially collimated beam of light onto the diffractive optical microstructure such that the beam is transformed into a far field interference pattern corresponding to the stored encrypted data that is reconstructed in a reconstruction plane remote from the microstructure;

optical detection means located in the reconstruction plane for detecting the far field interference pattern and for generating signals representing the stored encrypted data; and

processing means for receiving and processing the signals from the optical detection means, wherein the processing means includes decryption means for decrypting the encrypted data represented by the signals from the detection means.