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AssigneeDe La Rue International Limited
InventorsLawrence George Commander, Christopher John Eastell, Roland Isherwood, Brian William Holmes
Estimating the term…
A security device comprises a substrate having an array of microlenses on one side and one or more corresponding arrays of microimages on the other side. The microimages are located at a distance from the microlenses substantially equal to the focal length of the microlenses. The substrate is sufficiently transparent to enable light to pass through the microlenses so as to reach the microimages. Each microimage is defined by an anti-reflection structure on the substrate formed by a periodic array of identical structural elements, light passing through a substrate and impinging on the microimages being reflected to a different extent than light which does not impinge on the microimages thereby rendering the microimages visible.
A method of manufacturing a security device comprises providing an array of microlenses on one side of a substrate and one or more corresponding arrays of microimages on the other side, the microimages being located at a distance from the microlenses substantially equal to the focal length of the microlenses, the substrate being sufficiently transparent to enable light to pass through the microlenses so as to reach the microimages characterized in that each microimage is defined by an anti-reflection structure on the substrate formed by a periodic array of identical structural elements, and an at least partially reflecting layer on the same side of the substrate as the anti-reflection structure, the anti-reflection structure reducing the reflective property of the reflecting layer, wherein one or both of the anti-reflection structure and the at least partially reflecting layer is in the shape of a microimage, whereby light passing through the substrate and impinging on the microimages is reflected to a different extent than light which does not impinge on the microimages thereby rendering the microimages visible.
A security device comprising a substrate having an array of microlenses on one side and at least two corresponding arrays of microimages on the other side, the images being located at a distance from the microlenses substantially equal to the focal length of the microlenses, the substrate being sufficiently transparent to enable light to pass through the microlenses so as to reach the microimages, wherein the images within each array are the same, but differ from the images in the or each other array, and wherein at least one microimage array is in imperfect registration with the microlens array, the arrangement being such that when the microimages are viewed through the microlens array, moire magnified versions of the images are visible and, when the substrate is tilted, the magnified images of one array move relative to the magnified images of the or each other array.
Dependencies are inferred from the claim text.