Abstract: A security device is disclosed having a region of piezochromic material and an integrated relief structure. The security device is arranged such that when a stress is generated in the piezochromic material and relief structure, an optical effect is generated in the piezochromic material.

Abstract: A security device is disclosed having a region of piezochromic material and an integrated relief structure. The security device is arranged such that when a stress is generated in the piezochromic material and relief structure, an optical effect is generated in the piezochromic material.

Abstract: 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.

Abstract: 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.

Abstract: A security device comprises at least two regions, each region comprising a prismatic surface structure defining an array of substantially planar facets. Each region forms a reflector due to total internal reflection when viewed at least one first viewing angle and is transparent when viewed at at least one second viewing angle. The said at least one first viewing angle of one region is different from the at least one first viewing angle of the other region.

Abstract: A security device comprises a substrate (1) having an array of microlenses (3) on one side and one or more corresponding arrays of microimages (4) on the other side. The microimages (4) are located at a distance from the microlenses (3) substantially equal to the focal length of the microlenses. The substrate (1) is sufficiently transparent to enable light to pass through the microlenses (3) so as to reach the microimages (4). Each microimage (4) is defined by an anti-reflection structure on the substrate (1) formed by a periodic array of identical structural elements, light passing through the 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.

Abstract: A security device comprises a substrate (1) having an array of microlenses (3) on one side and one or more corresponding arrays of microimages (4) on the other side. The microimages (4) are located at a distance from the microlenses (3) substantially equal to the focal length of the microlenses. The substrate (1) is sufficiently transparent to enable light to pass through the microlenses (3) so as to reach the microimages (4). Each microimage (4) is defined by an anti-reflection structure on the substrate (1) formed by a periodic array of identical structural elements, light passing through the 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.

Abstract: A security device comprises at least two regions, each region comprising a prismatic surface structure defining an array of substantially planar facets. Each region forms a reflector due to total internal reflection when viewed at least one first viewing angle and is transparent when viewed at least one second viewing angle. The said at least one first viewing angle of one region is different from the at least one first viewing angle of the other region. Furthermore, a security device comprising an asymmetrical or truncated prismatic surface structure is located in a transparent area of an article.