WO1992016880A1 - Holograms - Google Patents

Holograms Download PDF

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Publication number
WO1992016880A1
WO1992016880A1 PCT/GB1992/000453 GB9200453W WO9216880A1 WO 1992016880 A1 WO1992016880 A1 WO 1992016880A1 GB 9200453 W GB9200453 W GB 9200453W WO 9216880 A1 WO9216880 A1 WO 9216880A1
Authority
WO
WIPO (PCT)
Prior art keywords
photosensitive material
image
light beam
region
hologram
Prior art date
Application number
PCT/GB1992/000453
Other languages
French (fr)
Inventor
Simon Charles Webster
Original Assignee
Gec-Marconi Limited
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Gec-Marconi Limited filed Critical Gec-Marconi Limited
Publication of WO1992016880A1 publication Critical patent/WO1992016880A1/en

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Classifications

    • GPHYSICS
    • G03PHOTOGRAPHY; CINEMATOGRAPHY; ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ELECTROGRAPHY; HOLOGRAPHY
    • G03HHOLOGRAPHIC PROCESSES OR APPARATUS
    • G03H1/00Holographic processes or apparatus using light, infrared or ultraviolet waves for obtaining holograms or for obtaining an image from them; Details peculiar thereto
    • G03H1/04Processes or apparatus for producing holograms
    • G03H1/0402Recording geometries or arrangements
    • GPHYSICS
    • G03PHOTOGRAPHY; CINEMATOGRAPHY; ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ELECTROGRAPHY; HOLOGRAPHY
    • G03HHOLOGRAPHIC PROCESSES OR APPARATUS
    • G03H1/00Holographic processes or apparatus using light, infrared or ultraviolet waves for obtaining holograms or for obtaining an image from them; Details peculiar thereto
    • G03H1/0005Adaptation of holography to specific applications
    • G03H1/0011Adaptation of holography to specific applications for security or authentication
    • GPHYSICS
    • G03PHOTOGRAPHY; CINEMATOGRAPHY; ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ELECTROGRAPHY; HOLOGRAPHY
    • G03HHOLOGRAPHIC PROCESSES OR APPARATUS
    • G03H1/00Holographic processes or apparatus using light, infrared or ultraviolet waves for obtaining holograms or for obtaining an image from them; Details peculiar thereto
    • G03H1/04Processes or apparatus for producing holograms
    • G03H1/0402Recording geometries or arrangements
    • G03H1/0406Image plane or focused image holograms, i.e. an image of the object or holobject is formed on, in or across the recording plane
    • GPHYSICS
    • G03PHOTOGRAPHY; CINEMATOGRAPHY; ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ELECTROGRAPHY; HOLOGRAPHY
    • G03HHOLOGRAPHIC PROCESSES OR APPARATUS
    • G03H1/00Holographic processes or apparatus using light, infrared or ultraviolet waves for obtaining holograms or for obtaining an image from them; Details peculiar thereto
    • G03H1/02Details of features involved during the holographic process; Replication of holograms without interference recording
    • G03H2001/0204Object characteristics
    • GPHYSICS
    • G03PHOTOGRAPHY; CINEMATOGRAPHY; ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ELECTROGRAPHY; HOLOGRAPHY
    • G03HHOLOGRAPHIC PROCESSES OR APPARATUS
    • G03H1/00Holographic processes or apparatus using light, infrared or ultraviolet waves for obtaining holograms or for obtaining an image from them; Details peculiar thereto
    • G03H1/02Details of features involved during the holographic process; Replication of holograms without interference recording
    • G03H2001/0208Individual components other than the hologram
    • G03H2001/0224Active addressable light modulator, i.e. Spatial Light Modulator [SLM]
    • GPHYSICS
    • G03PHOTOGRAPHY; CINEMATOGRAPHY; ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ELECTROGRAPHY; HOLOGRAPHY
    • G03HHOLOGRAPHIC PROCESSES OR APPARATUS
    • G03H1/00Holographic processes or apparatus using light, infrared or ultraviolet waves for obtaining holograms or for obtaining an image from them; Details peculiar thereto
    • G03H1/04Processes or apparatus for producing holograms
    • G03H1/0402Recording geometries or arrangements
    • G03H2001/0413Recording geometries or arrangements for recording transmission holograms
    • GPHYSICS
    • G03PHOTOGRAPHY; CINEMATOGRAPHY; ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ELECTROGRAPHY; HOLOGRAPHY
    • G03HHOLOGRAPHIC PROCESSES OR APPARATUS
    • G03H1/00Holographic processes or apparatus using light, infrared or ultraviolet waves for obtaining holograms or for obtaining an image from them; Details peculiar thereto
    • G03H1/04Processes or apparatus for producing holograms
    • G03H1/0402Recording geometries or arrangements
    • G03H2001/0415Recording geometries or arrangements for recording reflection holograms
    • GPHYSICS
    • G03PHOTOGRAPHY; CINEMATOGRAPHY; ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ELECTROGRAPHY; HOLOGRAPHY
    • G03HHOLOGRAPHIC PROCESSES OR APPARATUS
    • G03H1/00Holographic processes or apparatus using light, infrared or ultraviolet waves for obtaining holograms or for obtaining an image from them; Details peculiar thereto
    • G03H1/04Processes or apparatus for producing holograms
    • G03H1/0402Recording geometries or arrangements
    • G03H2001/0415Recording geometries or arrangements for recording reflection holograms
    • G03H2001/0417Recording geometries or arrangements for recording reflection holograms for recording single beam Lippmann hologram wherein the object is illuminated by reference beam passing through the recording material
    • GPHYSICS
    • G03PHOTOGRAPHY; CINEMATOGRAPHY; ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ELECTROGRAPHY; HOLOGRAPHY
    • G03HHOLOGRAPHIC PROCESSES OR APPARATUS
    • G03H1/00Holographic processes or apparatus using light, infrared or ultraviolet waves for obtaining holograms or for obtaining an image from them; Details peculiar thereto
    • G03H1/04Processes or apparatus for producing holograms
    • G03H1/0402Recording geometries or arrangements
    • G03H2001/0419Recording geometries or arrangements for recording combined transmission and reflection holograms
    • GPHYSICS
    • G03PHOTOGRAPHY; CINEMATOGRAPHY; ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ELECTROGRAPHY; HOLOGRAPHY
    • G03HHOLOGRAPHIC PROCESSES OR APPARATUS
    • G03H1/00Holographic processes or apparatus using light, infrared or ultraviolet waves for obtaining holograms or for obtaining an image from them; Details peculiar thereto
    • G03H1/22Processes or apparatus for obtaining an optical image from holograms
    • G03H1/2202Reconstruction geometries or arrangements
    • G03H2001/2223Particular relationship between light source, hologram and observer
    • G03H2001/2228Particular relationship between light source, hologram and observer adapted for reflection and transmission reconstruction
    • GPHYSICS
    • G03PHOTOGRAPHY; CINEMATOGRAPHY; ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ELECTROGRAPHY; HOLOGRAPHY
    • G03HHOLOGRAPHIC PROCESSES OR APPARATUS
    • G03H2210/00Object characteristics
    • G03H2210/202D object
    • GPHYSICS
    • G03PHOTOGRAPHY; CINEMATOGRAPHY; ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ELECTROGRAPHY; HOLOGRAPHY
    • G03HHOLOGRAPHIC PROCESSES OR APPARATUS
    • G03H2210/00Object characteristics
    • G03H2210/202D object
    • G03H2210/222D SLM object wherein the object beam is formed of the light modulated by the SLM
    • GPHYSICS
    • G03PHOTOGRAPHY; CINEMATOGRAPHY; ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ELECTROGRAPHY; HOLOGRAPHY
    • G03HHOLOGRAPHIC PROCESSES OR APPARATUS
    • G03H2210/00Object characteristics
    • G03H2210/303D object
    • GPHYSICS
    • G03PHOTOGRAPHY; CINEMATOGRAPHY; ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ELECTROGRAPHY; HOLOGRAPHY
    • G03HHOLOGRAPHIC PROCESSES OR APPARATUS
    • G03H2210/00Object characteristics
    • G03H2210/303D object
    • G03H2210/323D+2D, i.e. composition of 3D and 2D sub-objects, e.g. scene in front of planar background
    • GPHYSICS
    • G03PHOTOGRAPHY; CINEMATOGRAPHY; ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ELECTROGRAPHY; HOLOGRAPHY
    • G03HHOLOGRAPHIC PROCESSES OR APPARATUS
    • G03H2210/00Object characteristics
    • G03H2210/303D object
    • G03H2210/333D/2D, i.e. the object is formed of stratified 2D planes, e.g. tomographic data
    • GPHYSICS
    • G03PHOTOGRAPHY; CINEMATOGRAPHY; ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ELECTROGRAPHY; HOLOGRAPHY
    • G03HHOLOGRAPHIC PROCESSES OR APPARATUS
    • G03H2210/00Object characteristics
    • G03H2210/50Nature of the object
    • G03H2210/54For individualisation of product
    • GPHYSICS
    • G03PHOTOGRAPHY; CINEMATOGRAPHY; ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ELECTROGRAPHY; HOLOGRAPHY
    • G03HHOLOGRAPHIC PROCESSES OR APPARATUS
    • G03H2210/00Object characteristics
    • G03H2210/50Nature of the object
    • G03H2210/56Multiple objects, e.g. each in different environment
    • G03H2210/562Holographic object, i.e. a combination of an object and holobject
    • GPHYSICS
    • G03PHOTOGRAPHY; CINEMATOGRAPHY; ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ELECTROGRAPHY; HOLOGRAPHY
    • G03HHOLOGRAPHIC PROCESSES OR APPARATUS
    • G03H2223/00Optical components
    • G03H2223/14Diffuser, e.g. lens array, random phase mask
    • GPHYSICS
    • G03PHOTOGRAPHY; CINEMATOGRAPHY; ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ELECTROGRAPHY; HOLOGRAPHY
    • G03HHOLOGRAPHIC PROCESSES OR APPARATUS
    • G03H2227/00Mechanical components or mechanical aspects not otherwise provided for
    • G03H2227/04Production line for mass production
    • GPHYSICS
    • G03PHOTOGRAPHY; CINEMATOGRAPHY; ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ELECTROGRAPHY; HOLOGRAPHY
    • G03HHOLOGRAPHIC PROCESSES OR APPARATUS
    • G03H2250/00Laminate comprising a hologram layer
    • G03H2250/42Reflective layer
    • GPHYSICS
    • G03PHOTOGRAPHY; CINEMATOGRAPHY; ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ELECTROGRAPHY; HOLOGRAPHY
    • G03HHOLOGRAPHIC PROCESSES OR APPARATUS
    • G03H2270/00Substrate bearing the hologram
    • G03H2270/20Shape
    • G03H2270/23Ribbon shaped, e.g. holographic foil

Definitions

  • This invention relates to the mass production of holograms for security purposes.
  • holograms are used for authentication purposes and to discourage counterfeiting of, and/or unauthorised tampering with, the cards, labels, etc.
  • the holograms for such purposes are generally mass-produced by a process wherein, for example, a master surface-relief hologram of an object is produced, and this master is used to emboss reflection holograms into metal foil forming at least part of, or to be affixed to, the card, label etc.
  • the production of the die bearing the master hologram can be time-consuming and expensive.
  • all of the copy holograms produced by such a die are identical.
  • a process for producing security holograms wherein regions of photosensitive material are fed in turn through an exposure station; and wherein at said station a respective unique hologram is formed in each region by interference between a reference coherent light beam and a coherent light beam bearing an image.
  • Figures 1-8 are schematic side views illustrating respective different methods of mass-producing security holograms in accordance with the invention.
  • a coherent light beam 6 is passed through a photographic slide 7, or other transparency, which carries an image from which the hologram is to be formed, so that an object beam 8 bearing the image impinges on the photosensitive medium 1.
  • a reference coherent beam 9 is directed upwards through the conveyor 4 and through the photosensitive medium and interferes with the object beam 8, producing a holographic record on the medium.
  • One or more additional reference coherent beams 10 may also be used, if required.
  • the piece 1 of photosensitive medium is then moved onward from the exposure station 5 to a developing and fixing station (not shown) and the piece 2 is moved to the exposure station.
  • the transparency 7 is then changed, so that the hologram produced on the piece 2 is different from that on piece 1.
  • Figure 2 shows an alternative method in which the coherent light 6 is passed through a diffuser 11 and then through an updatable transmissive display 12, such as liquid crystal display. Due to the ability to update the display, the hologram is of an arbitrary nature. It is changed, from piece to piece of the photosensitive medium, by addressing the cells of the display 12 differently for each exposure so that each hologram is unique. As in Figure 1, the reference coherent beam 9, and the beam 10 if required, are directed upwards through the conveyor 4 and on to the photosensitive material.
  • a lens 13 is located between the display 12 (or a transparency in place of the display) and the photosensitive material, so that data items on the display or transparency are focused on to, or near, the plane of the material, and a clear holographic record of the Items is thereby produced.
  • the items are changed from piece to piece of photosensitive material by changing the addressing of the display cells or by using a different transparency for each piece.
  • the photosensitive material 14,15,16 is associated with a reflective backing layer 17.
  • the layer 17 may be attached to the material or may form part of the conveyor 4.
  • the reference beam 9 is directed on to the material from above, passes through the material a first time, is reflected by the backing layer 17, passes a second time through the photosensitive material and emerges therefrom.
  • the object beam 8 interferes with the reference beam during its first pass through the material, thereby forming a transmission hologram. It also interferes during the second pass, and a second interference grating is superimposed on the first and is viewable as a reflection hologram.
  • the method of the present embodiment can be effected entirely from the front side of the material.
  • An opaque conveyer 4 can therefore be used, and the production of the hologram can, if required, be carried out after the photosensitive material has been affixed to a product, if the reflective backing layer 17 is attached to the photosensitive material.
  • the object beam 8 can be produced by any of the previously-described methods.
  • a single coherent beam 18 passes upwards through the transparent conveyor 4 and through the photosensitive material 1.
  • the beam is reflected from a reflective diffusing updatable display 19, such as a reflective liquid crystal display, and returns to the photosensitive material as the object beam 20.
  • the beam 20 interferes with the input beam 18 and the required hologram is thereby produced.
  • the single coherent input beam therefore provides both the reference beam and the object beam.
  • This method is based on the so-called Denisyuk (or Lippmann) hologram.
  • Figure 6 shows an embodiment similar to that of Figure 5, but in which the single coherent reference beam 18 passes through the conveyor 4 and the photosensitive material 1 and then through an updatable transmissive (e.g. liquid crystal) display 21. It is then reflected from an object 22, so that the object beam 23 carries both the updatable information from the display 21 and fixed information from the object 22.
  • an updatable transmissive e.g. liquid crystal
  • Figure 7 shows another embodiment in which the reference beam 9 passes through the conveyor 4 and into the photosensitive material 1.
  • a coherent beam 6 passes through a diffuser 11, through a static transmissive display 24 and through an updatable display 25 to produce an object beam 26. This interferes with the beam 9 to produce the required holographic recording on the material 1.
  • a coherent beam 27 is passed through a pre-existing master hologram 28.
  • the resulting beam 29 is passed through an updatable (e.g. liquid crystal) display 30 to produce an object beam 31. This interferes with the reference beam 9 (and the beam 10, if used) to produce the output hologram at the photosensitive material 1.
  • the light source or sources for exposing the photosensitive material may produce continuous light for the whole of the exposure period. If that is the case, the pieces 1,2,3... of photosensitive material.must be moved into place at the exposure station by the conveyor and then held stationary during the exposure period.
  • the light source(s) may be pulsed. If the pulses are sufficiently short, the conveyor may move the photosensitive material continuously during exposure.
  • a continuous web of material might be used, the web being fed to a guillotine (not shown) for cutting it into pieces, each bearing a unique hologram.
  • the photosensitive material may be any of a number of types, including silver halide emulsion, a photopolymer material, a liquid crystal polymer or a photochromic material.
  • the material might be sensitised for recording at the wavelength of the light source(s) by inclusion of, for example, an absorbing dye therein.
  • the material could be deposited directly on the product, credit card, etc., which is to be marked, or might be deposited on a suitable substrate material.
  • Deposition of the photosensitive material may be effected by, for example, dipping the substrate into a liquid form of the photoconductive material, by spin coating the substrate or by screen printing.
  • each image may be provided on a transparency, such as a photographic slide, or an updatable transmissive display, such as a liquid crystal display or a spatial light modulator; in the form of an updatable reflecting two-dimensional device, such as a photographic print, a reflecting display (e.g. a liquid-crystal display) or a reflecting spatial light modulator; in the form of a three-dimensional object; or in the form of one or more pre-existing holograms.
  • a transparency such as a photographic slide, or an updatable transmissive display, such as a liquid crystal display or a spatial light modulator
  • an updatable reflecting two-dimensional device such as a photographic print
  • a reflecting display e.g. a liquid-crystal display
  • a reflecting spatial light modulator in the form of a three-dimensional object
  • pre-existing holograms in the form of one or more pre-existing holograms.
  • each hologram is unique or quasi-unique.
  • the apparatus can be made to effect this changing of the hologram automatically as each hologram is produced.
  • Each product, credit card, etc. bearing such hologram is, therefore, "fingerprinted", which lends authenticity to it and makes counterfeiting more difficult.
  • the holographic nature of the label, etc. would be more discouraging to potential counterfeiters than would a normally-printed image.
  • variable data Items such as batch numbers, incremented serial numbers, owner codes, sell-by dates, etc.
  • This holographic recording will clearly provide added security for the recorded data.
  • Each hologram thus produced is usable by itself on a product, credit card, etc. as a security device, i .e. only one such hologram per article is needed.

Abstract

In a process for the mass production of holograms for security purposes, regions (1, 2, 3 ...) of a photosensitive material are fed in turn through an exposure position (5) at which a respective unique hologram is formed in each region by interference between a reference coherent light beam (9) and a coherent light beam (8) bearing an image. The image is partially or wholly changed for each successive region, and may be carried by an updatable display, such as a liquid crystal display.

Description

Holograms
This invention relates to the mass production of holograms for security purposes.
In some known security systems, for example as used on some credit cards and bank cards and for secure labelling of products, holograms are used for authentication purposes and to discourage counterfeiting of, and/or unauthorised tampering with, the cards, labels, etc. The holograms for such purposes are generally mass-produced by a process wherein, for example, a master surface-relief hologram of an object is produced, and this master is used to emboss reflection holograms into metal foil forming at least part of, or to be affixed to, the card, label etc. The production of the die bearing the master hologram can be time-consuming and expensive. Furthermore, all of the copy holograms produced by such a die are identical.
It is an object of the present invention to provide an improved process for producing holograms for security purposes.
According to the invention there is provided a process for producing security holograms, wherein regions of photosensitive material are fed in turn through an exposure station; and wherein at said station a respective unique hologram is formed in each region by interference between a reference coherent light beam and a coherent light beam bearing an image.
Embodiments of the invention will now be described, by way of example, with reference to the accompanying drawings, in which
Figures 1-8 are schematic side views illustrating respective different methods of mass-producing security holograms in accordance with the invention.
Referring to Figure 1 of the drawings, in a first method of mass-producing security holograms, pieces 1,2,3,...of a high-resolution photosensitive medium, which may be applied to a transparent backing film (not shown), are fed in turn by a transparent conveyor 4 through an exposure station 5. At the exposure station a coherent light beam 6 is passed through a photographic slide 7, or other transparency, which carries an image from which the hologram is to be formed, so that an object beam 8 bearing the image impinges on the photosensitive medium 1. A reference coherent beam 9 is directed upwards through the conveyor 4 and through the photosensitive medium and interferes with the object beam 8, producing a holographic record on the medium. One or more additional reference coherent beams 10 may also be used, if required. The piece 1 of photosensitive medium is then moved onward from the exposure station 5 to a developing and fixing station (not shown) and the piece 2 is moved to the exposure station. The transparency 7 is then changed, so that the hologram produced on the piece 2 is different from that on piece 1.
Figure 2 shows an alternative method in which the coherent light 6 is passed through a diffuser 11 and then through an updatable transmissive display 12, such as liquid crystal display. Due to the ability to update the display, the hologram is of an arbitrary nature. It is changed, from piece to piece of the photosensitive medium, by addressing the cells of the display 12 differently for each exposure so that each hologram is unique. As in Figure 1, the reference coherent beam 9, and the beam 10 if required, are directed upwards through the conveyor 4 and on to the photosensitive material.
In Figure 3 a lens 13 is located between the display 12 (or a transparency in place of the display) and the photosensitive material, so that data items on the display or transparency are focused on to, or near, the plane of the material, and a clear holographic record of the Items is thereby produced. Again, the items are changed from piece to piece of photosensitive material by changing the addressing of the display cells or by using a different transparency for each piece.
In the embodiment of Figure 4 the photosensitive material 14,15,16 is associated with a reflective backing layer 17. The layer 17 may be attached to the material or may form part of the conveyor 4. The reference beam 9 is directed on to the material from above, passes through the material a first time, is reflected by the backing layer 17, passes a second time through the photosensitive material and emerges therefrom. The object beam 8 interferes with the reference beam during its first pass through the material, thereby forming a transmission hologram. It also interferes during the second pass, and a second interference grating is superimposed on the first and is viewable as a reflection hologram. Whereas the embodiments of Figures 1-3 require the use of a transparent conveyor to allow access to the underside of the photosensitive material, the method of the present embodiment can be effected entirely from the front side of the material. An opaque conveyer 4 can therefore be used, and the production of the hologram can, if required, be carried out after the photosensitive material has been affixed to a product, if the reflective backing layer 17 is attached to the photosensitive material. The object beam 8 can be produced by any of the previously-described methods.
Referring to Figure 5, in another method of forming a hologram a single coherent beam 18 passes upwards through the transparent conveyor 4 and through the photosensitive material 1. The beam is reflected from a reflective diffusing updatable display 19, such as a reflective liquid crystal display, and returns to the photosensitive material as the object beam 20. The beam 20 interferes with the input beam 18 and the required hologram is thereby produced. The single coherent input beam therefore provides both the reference beam and the object beam. This method is based on the so-called Denisyuk (or Lippmann) hologram.
Figure 6 shows an embodiment similar to that of Figure 5, but in which the single coherent reference beam 18 passes through the conveyor 4 and the photosensitive material 1 and then through an updatable transmissive (e.g. liquid crystal) display 21. It is then reflected from an object 22, so that the object beam 23 carries both the updatable information from the display 21 and fixed information from the object 22.
Figure 7 shows another embodiment in which the reference beam 9 passes through the conveyor 4 and into the photosensitive material 1. A coherent beam 6 passes through a diffuser 11, through a static transmissive display 24 and through an updatable display 25 to produce an object beam 26. This interferes with the beam 9 to produce the required holographic recording on the material 1.
In the embodiment of Figure 8 a coherent beam 27 is passed through a pre-existing master hologram 28. The resulting beam 29 is passed through an updatable (e.g. liquid crystal) display 30 to produce an object beam 31. This interferes with the reference beam 9 (and the beam 10, if used) to produce the output hologram at the photosensitive material 1.
A number of modifications can be made to the embodiments described above. For example, in the embodiments of Figures 2 and 3 the positions of the diffuser 11 and the display 12 can be interchanged. Likewise, in Figure 7 the diffuser 11 may alternatively be positioned beneath the displays 24 and 25 or between them. Although the conveyor 4 has been described as transparent, it would alternatively be possible to use an opaque conveyor with apertures therein of substantially the same dimensions as the pieces of photosensitive material.
At the exposure station 5 the light source or sources for exposing the photosensitive material may produce continuous light for the whole of the exposure period. If that is the case, the pieces 1,2,3... of photosensitive material.must be moved into place at the exposure station by the conveyor and then held stationary during the exposure period. Alternatively, the light source(s) may be pulsed. If the pulses are sufficiently short, the conveyor may move the photosensitive material continuously during exposure. Instead of feeding separate pieces of photosensitive material to the exposure station, a continuous web of material might be used, the web being fed to a guillotine (not shown) for cutting it into pieces, each bearing a unique hologram.
The photosensitive material may be any of a number of types, including silver halide emulsion, a photopolymer material, a liquid crystal polymer or a photochromic material. The material might be sensitised for recording at the wavelength of the light source(s) by inclusion of, for example, an absorbing dye therein. The material could be deposited directly on the product, credit card, etc., which is to be marked, or might be deposited on a suitable substrate material. Deposition of the photosensitive material may be effected by, for example, dipping the substrate into a liquid form of the photoconductive material, by spin coating the substrate or by screen printing.
The images to be used in the production of the holograms may be provided in any of a number of forms, some of which are described above. For example, each image may be provided on a transparency, such as a photographic slide, or an updatable transmissive display, such as a liquid crystal display or a spatial light modulator; in the form of an updatable reflecting two-dimensional device, such as a photographic print, a reflecting display (e.g. a liquid-crystal display) or a reflecting spatial light modulator; in the form of a three-dimensional object; or in the form of one or more pre-existing holograms.
It will be apparent that, by use of an updatable display as described above, or by a simple image-changing operation such as substituting a different transparency for each successive exposure, each hologram is unique or quasi-unique. The apparatus can be made to effect this changing of the hologram automatically as each hologram is produced. Each product, credit card, etc. bearing such hologram is, therefore, "fingerprinted", which lends authenticity to it and makes counterfeiting more difficult. The holographic nature of the label, etc., would be more discouraging to potential counterfeiters than would a normally-printed image. Furthermore, by use of a readily updatable display for producing the image, variable data Items, such as batch numbers, incremented serial numbers, owner codes, sell-by dates, etc., can be readily incorporated in the holograms. This holographic recording will clearly provide added security for the recorded data.
Each hologram thus produced is usable by itself on a product, credit card, etc. as a security device, i .e. only one such hologram per article is needed.

Claims

Claims
1. A process for producing security holograms, characterised in that regions (1,2,3,...) of photosensitive material are fed in turn through an exposure station (5); and at said station a respective unique hologram is formed in each region by interference between a reference coherent light beam (9) and a coherent light beam (8) bearing an image.
2. A process as claimed in Claim 1, characterised in that for each region (1,2,3,...) said image is carried by, or is modified by, an updatable display (21).
3. A process as claimed in Claim 2, characterised in that the updatable display (21) comprises a liquid crystal display.
4. A process as claimed in Claim 2, characterised in that the updatable display (21) comprises a spatial light modulator.
5. A process as claimed in any preceding claim, characterised in that for each region (1,2,3,...) the image is carried by a respective transparency (7).
6. A process as claimed in any one of Claims 1-4, characterised in that for each region (1,2,3,...) the image is carried by a respective photographic print.
7. A process as claimed in any one of Claims 1-4, characterised in that for each region (1,2,3,...) the image is in the form of a respective hologram (28).
8. A process as claimed in any one of Claims 1-4, characterised in that for each region (1,2,3,...) the image is derived from a three-dimensional object (22).
9. A process as claimed in any preceding claim, characterised in that the photosensitive material (1,2,3,...) is light-transmissive; and the image-bearing light beam (8) and the reference light beam (9) are directed at the photosensitive material from opposite faces of the material.
10. A process as claimed 1n any one of Claims 1-8, characterised 1n that the photosensitive material (1,2,3,...) is light-transmissive; and the image-bearing light beam (20) 1s produced by reflection of the reference beam after the reference beam (18) has passed through the photosensitive material.
11. A process as claimed in any one of Claims 1-8, characterised in that the photosensitive material (1,2,3,...) has a reflective backing (17) associated therewith; the reference light beam (9) makes a first pass through the photosensitive material, is reflected by the reflective backing and makes a second pass back through the photosensitive material; and the image-bearing light beam (8) interferes with the reference light beam both on said first pass and on said second pass through the photosensitive material, thereby forming a reflection hologram.
12. A process as claimed in any preceding claim, characterised in that changing of the image is effected automatically as the regions (1,2,3,...) are fed to the exposure station (5).
13. A process as claimed in any preceding claim, wherein the photosensitive material comprises a silver halide emulsion.
14. A process as claimed in any one of Claims 1-12, wherein the photosensitive material comprises a photopolymer material.
15. A process as claimed in any one of Claims 1-12, wherein the photosensitive material comprises a liquid crystal polymer.
16. A process as claimed in any one of Claims 1-12, wherein the photosensitive material comprises a photochromic material.
17. A process as claimed in any one of Claims 13-16, wherein the photosensitive material contains a dye selected for improved operation at the wavelength of the reference and image-bearing light beams.
18. A process for marking a plurality of articles, wherein a respective hologram produced by a process as claimed in any one of Claims 1-17 is attached to each said article.
PCT/GB1992/000453 1991-03-15 1992-03-13 Holograms WO1992016880A1 (en)

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GB919105520A GB9105520D0 (en) 1991-03-15 1991-03-15 Holograms

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EP1278107A3 (en) * 2001-07-18 2006-12-06 Dai Nippon Printing Co., Ltd. Hologram recording film with additional information and recording method therefor
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CN104011606A (en) * 2011-12-30 2014-08-27 拜尔材料科学有限公司 Interferometric Spatial Light Modulator For Production Of Digital Holograms
EP0896260B1 (en) * 1997-08-06 2016-12-07 Bundesdruckerei GmbH Method and apparatus for manufacturing holograms by contact copying
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EP1515199A2 (en) * 1995-07-18 2005-03-16 Dai Nippon Printing Co., Ltd. Subject plate for recording holograms, hologram-making method, and hologram-recorded article
DE19809403B4 (en) * 1997-08-05 2017-07-06 Bundesdruckerei Gmbh Method for producing a hologram with machine-readable information
EP0896260B1 (en) * 1997-08-06 2016-12-07 Bundesdruckerei GmbH Method and apparatus for manufacturing holograms by contact copying
EP1925993A3 (en) * 1999-04-12 2011-03-09 Dai Nippon Printing Co., Ltd. Color hologram display and its fabrication process
EP1045296A3 (en) * 1999-04-12 2006-12-06 Dai Nippon Printing Co., Ltd. Color hologram display and its fabrication process
JP2000356941A (en) * 1999-04-12 2000-12-26 Dainippon Printing Co Ltd Color hologram display and its formation
EP1925993A2 (en) * 1999-04-12 2008-05-28 Dai Nippon Printing Co., Ltd. Color hologram display and its fabrication process
US7710622B2 (en) 1999-04-12 2010-05-04 Dai Nippon Printing Co., Ltd. Color hologram display and its fabrication process
EP1278107A3 (en) * 2001-07-18 2006-12-06 Dai Nippon Printing Co., Ltd. Hologram recording film with additional information and recording method therefor
EP1744228A2 (en) * 2005-07-11 2007-01-17 Dai Nippon Printing Co., Ltd. Volume reflection hologram and corresponding recording process
EP2273321A1 (en) * 2005-07-11 2011-01-12 Dai Nippon Printing Co., Ltd. Volume reflection hologram and corresponding recording process
US8289595B2 (en) 2005-07-11 2012-10-16 Dai Nippon Printing Co., Ltd. Hologram and its holographic process
US7538919B2 (en) 2005-07-11 2009-05-26 Dai Nippon Printing Co., Ltd. Three-dimensional hologram process with overt anti-counterfeit security using first object light, second object light, and reference light
EP1744228A3 (en) * 2005-07-11 2007-03-21 Dai Nippon Printing Co., Ltd. Volume reflection hologram and corresponding recording process
CN104011606A (en) * 2011-12-30 2014-08-27 拜尔材料科学有限公司 Interferometric Spatial Light Modulator For Production Of Digital Holograms
EP2798412A4 (en) * 2011-12-30 2015-10-07 Bayer Materialscience Llc Interferometric spatial light modulator for production of digital holograms
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US11703799B2 (en) 2018-01-08 2023-07-18 Digilens Inc. Systems and methods for high-throughput recording of holographic gratings in waveguide cells

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GB9105520D0 (en) 1991-05-01
GB9205579D0 (en) 1992-04-29
GB2254166A (en) 1992-09-30

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