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 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: An optical system is disclosed for use in sorting apparatus to monitor light at a viewing station thereof to generate signals indicative of the optical properties of selected items in the product stream being sorted. In the system light received from a single line at the viewing station is split into discrete beams, which are filtered into different wavelength ranges to determine the category of the respective product items. The beams are directed onto a slit through which the light beams must pass on their way to respective lines of light sensors.