Abstract: We describe methods of mass-producing full color, 3D holograms, potentially incorporating a personalized image, which are particularly suitable for security purposes. Broadly speaking in embodiments a method generates, electronically, an interlaced image comprising a set of different views of a 3D object from different angles. This is projected onto a diffusing screen using coherent light and mapped from the screen into an angularly encoded object beam using a lenticular array. The different views in the angularly encoded object beam are then recorded simultaneously into holographic film using a reference beam.

Abstract: Various holographic films for recording multicolor volume holograms, especially full color volume reflection holograms, and to manufacturing techniques for such film, and to corresponding methods of recording multicolor and full-color volume, in particular volume reflection holograms. We describe a holographic film for recording a multicolor volume hologram, the film including: a carrier; a first photosensitive recording layer sensitive to one or both of red and green laser light; and a second photosensitive recording layer sensitive to blue laser light. Both the first and second photosensitive recording layers include silver halide and have a grain size of less than 30 nm, and at least one of the photosensitive recording layers has a thickness of greater than 3 ?m and less than 5 ?m.

Abstract: We describe a window assembly comprising: a window pane comprising a glass or plastic sheet; and a layer of holographic recording medium attached to said glass or plastic sheet; wherein said layer of holographic recording medium has recorded within the medium a volume hologram configured to direct light incident onto said glass or plastic sheet to propagate within a thickness of said glass or plastic sheet. In embodiments the volume hologram is fabricated by recording a transmission hologram and shrinking the recorded hologram to convert the transmission hologram to an edge-directing hologram configured to direct light in a direction to be totally internally reflected within the window pane, for example at greater than 40°, 50°, 60°, 70°, 75° or 80° to a normal to the surface of the hologram.

Abstract: We fabricate a stereoscopic hologram of an object by capturing a sequence of 2D images of the object, moving camera along a linear axis past the object and keeping the optical axis of the camera perpendicular at each of the positions. The camera lens and image recording surface are translated along the axis such that a fiducial part of the image does not move. The sequence is replayed and a first volume hologram is recorded by recording holograms of the captured images on a diffusing screen in different spatial locations on a surface of the first volume hologram. This is then replayed to form a stereoscopic image of the object and a second, volume reflection hologram of the replayed image is recorded to provide the stereoscopic hologram. A central image of the sequence is aligned to the fiducial part of the holographic image to make the resulting hologram “user-friendly”.

Abstract: This invention relates to holographic film for recording multicolor volume holograms, especially full color volume reflection holograms, and to manufacturing techniques for such film, and to corresponding methods of recording multicolor and full-color volume, in particular volume reflection holograms. We describe a holographic film for recording a multicolor volume hologram, the film comprising: a carrier; a first photosensitive recording layer sensitive to one or both of red and green laser light; and a second photosensitive recording layer sensitive to blue laser light. Both the first and second photosensitive recording layers comprise silver halide and have a grain size of less than 30 nm, and at least one of the photosensitive recording layers has a thickness of greater than 3 ?m and less than 5 ?m.

Abstract: A holographic film for recording multicolor volume holograms, especially full color volume reflection holograms, and/or manufacturing techniques for such film, and/or corresponding methods of recording multicolor and full-color volume, in particular volume reflection holograms. In one case, a holographic film for recording a multicolor volume hologram is set forth that includes: a carrier; a first photosensitive recording layer sensitive to one or both of red and green laser light; and a second photosensitive recording layer sensitive to blue laser light.

Abstract: We describe methods of mass-producing full colour, 3D holograms, potentially incorporating a personalised image, which are particularly suitable for security purposes. Broadly speaking in embodiments a method generates, electronically, an interlaced image comprising a set of different views of a 3D object from different angles. This is projected onto a diffusing screen using coherent light and mapped from the screen into an angularly encoded object beam using a lenticular array. The different views in the angularly encoded object beam are then recorded simultaneously into holographic film using a reference beam.

Abstract: We fabricate a stereoscopic hologram of an object by capturing a sequence of 2D images of the object, moving camera along a linear axis past the object and keeping the optical axis of the camera perpendicular at each of the positions. The camera lens and image recording surface are translated along the axis such that a fiducial part of the image does not move. The sequence is replayed and a first volume hologram is recorded by recording holograms of the captured images on a diffusing screen in different spatial locations on a surface of the first volume hologram. This is then replayed to form a stereoscopic image of the object and a second, volume reflection hologram of the replayed image is recorded to provide the stereoscopic hologram. A central image of the sequence is aligned to the fiducial part of the holographic image to make the resulting hologram “user-friendly”.

Abstract: We describe techniques for recording a holographic image onto holographic recording film, in particular for security holograms. We thus describe a structure having a stack comprising the holographic recording film and a multichannel image generation device under the film. A three-dimensional object (or hologram of a 3D object) is provided, located under the multichannel image generation device. At least a portion of the multichannel image generation device is substantially transparent or absent in a region above the object. A holographic image is recorded in the film by illuminating the stack with laser light. The multichannel image generation device under the film may comprise a volume reflection hologram of a lenticularly generated image. The structure records a hologram of the 3D object in conjunction with a multi-channel holographic image.

Abstract: Improved techniques for using holograms to provide security for documents and the like. A method of providing a tamper-resistant pattern in association with a hologram on a substrate, the method including: preparing a hologram, the hologram being recorded in a photosensitive recording layer carried by a carrier; printing a pattern onto the photosensitive recording layer; and then attaching the hologram to a substrate by adhesive such that the pattern is between the photosensitive recording layer and the substrate to provide a tamper-resistant pattern in association with the hologram.

Abstract: A holographic recording system (1) includes a transparent or semi-transparent holographic recording medium (6), a source of coherent optical radiation (7), and an optical system (10). The recording medium has a first side (25) presented toward the radiation source, a second side (26) opposite to the first side and presented toward the optical system, and a recording volume (30) between the two sides. The radiation source is arranged to project incident optical radiation (20) onto the first side and through the recording volume towards the optical system, which is arranged to redirect (32) the optical radiation back onto the second side and into the recording volume so that the incident and redirected radiation intersect within the recording volume at an obtuse angle (34) to create an interference pattern (38) from which a holographic recording may be made.

Abstract: This invention relates to holographic film for recording multicolor volume holograms, especially full color volume reflection holograms, and to manufacturing techniques for such film, and to corresponding methods of recording multicolor and full-color volume, in particular volume reflection holograms. We describe a holographic film for recording a multicolor volume hologram, the film comprising: a carrier; a first photosensitive recording layer sensitive to one or both of red and green laser light; and a second photosensitive recording layer sensitive to blue laser light. Both the first and second photosensitive recording layers comprise silver halide and have a grain size of less than 30 nm, and at least one of the photosensitive recording layers has a thickness of greater than 3 ?m and less than 5 ?m.

Abstract: We describe methods of recording a holographic image onto holographic recording film, film bearing recorded holographic images, and apparatus for recording a holographic image onto film, in particular for security holograms.

Abstract: This invention relates to holograms employing colour addition techniques, and to methods and apparatus for the fabrication of such holograms. The holograms are particularly useful for security applications. A volume reflection hologram storing at least two images, the hologram comprising: a first stored image configured to replay at a first wavelength; a second stored image configured to replay at a second wavelength different to said first wavelength; wherein said first and second images at least partially overlap when replayed together; and wherein said first and second wavelengths are selected such that where said first and second images overlap they give the appearance of a colour defined by a third wavelength different to both said first and second wavelengths.

Abstract: This invention relates to improved methods of fabricating hologram systems, in particular holograms on a substrate such as a security document or bank note, to hologram systems fabricated by the described methods, and to starting materials for the methods. A method of preparing a hologram on a substrate, the method comprising: providing a hologram recording medium, the material comprising a carrier bearing a photosensitive hologram recording layer; recording a hologram in said photosensitive hologram recording layer; applying an adhesive to said hologram recording layer; attaching said carrier bearing said hologram recording layer to a substrate using said adhesive; and removing said carrier to leave said hologram recording layer attached to said substrate by said adhesive.

Abstract: This invention relates to improved techniques for reading holograms, in particular volume reflection holograms, and to improved security documents incorporating volume reflection holograms.

Abstract: This invention relates to improved techniques for using holograms to provide security for documents and the like. A method of providing a tamper-resistant pattern in association with a hologram on a substrate, the method comprising: preparing a hologram, said hologram being recorded in a photosensitive recording layer carried by a carrier; printing a pattern onto said photosensitive recording layer; and then attaching said hologram to a substrate by adhesive such that said pattern is between said photosensitive recording layer and said substrate to provide a tamper-resistant pattern in association with said hologram.

Abstract: The present invention relates to a method and apparatus for producing a hologram, in particular a dot matrix volume hologram. A holographic recording system (1) comprises a source of optical radiation (7), a transparent or partially transparent holographic recording medium 6 and an optical system (10). The recording medium (6) has a first side (25), a second side (26) and a recording volume (36), the second side (26) being opposite to said first side (25) and the recording volume (36) being between said sides (25, 26). The recording medium (6) is positioned between the source of optical radiation (7) and the optical system (10) so that the first side (25) is presented towards the source of optical radiation (7) and the second side (26) is presented towards the optical system. The source (7) is arranged to project incident optical radiation (20) onto the first side (25) and through the recording volume (36) towards the optical system (10).

Abstract: This invention relates to improved holographic recording media and to related methods and apparatus for fabricating and reading holograms. A holographic recording medium comprising: a carrier; and a photosensitive recording layer carried by said carrier, and wherein said recording medium further comprises: an optical filter, said filter comprising a bandpass filter defining at least one optical transmission window for recording a hologram in said photosensitive recording layer.

Abstract: This invention relates to improved holograms, in particular suitable for security applications, and to methods and apparatus for their fabrication. A hologram storing a pair of images, the hologram comprising: a first stored image configured to replay at a first wavelength; and a second stored image configured to replay at a second wavelength different to said first wavelength; and wherein said first and second stored images are spatially complementary such that when replayed they appear together, substantially in register, and give the appearance of a single, substantially uninterrupted image.