Abstract: A tamper-evident security device including a first part comprising an optically transparent layer including an array of separate optical focusing elements. A second part comprises an array of separate image elements collectively defining an image viewable through the first part. Each of the optical focusing elements is positioned to reveal therethrough a view of one or more of said image element(s). An optically transparent adhesive layer between the first part and the second part which retains the optical focusing elements so positioned with respect to the image elements thereby in cooperation to reveal the image. The first part is mechanically separable from the second part by release of the adhesive layer to cease the cooperation.

Abstract: A security device (1) comprising an optically transparent layer (3) including a repeating first array of separate optical focussing elements (3) (e.g. having translational symmetry) wherein a pitch distance between repeated elements in the first array is a first pitch value (A). The device also includes a repeating second array of separate image elements (6) (e.g. having translational symmetry) collectively defining an image viewable through the first part. The device is structured such that a pitch distance between repeated or successive elements in the second array is a second pitch value (B) wherein the ratio (A/B) of the first pitch value and the second pitch value has a value, A/B=n±?, that differs from a positive integer value, n, according to an absolute difference, ?, not exceeding 0.01 and not less than 0.001.

Abstract: A diffusive reflector for a lighting apparatus comprising a backing part upon a surface of which is disposed an interface part(s) wherein the interface part(s) is at least partially diffusively reflective optically and/or the backing part is diffusively reflective optically. The interface part(s) is formed with a plurality of separate protrusions each adapted for making a separate respective contact interface with a surface of a light guide panel of the lighting apparatus to optically couple the backing part to the light guide panel via the interface part(s). The interface part(s) comprises an optically transmissive interface material arranged to form said contact interface such that the interfacial energy thereof is reduced so that air is driven from the contact interface. Consequently, the critical angle for total internal reflection of light guided by the light guide panel is increased at said contact interface.