Abstract: A security device has a lenticular device including an array of lenticular focusing elements; a corresponding array of image strips sets, the sets having substantially the same periodicity as, or an integral multiple of the periodicity of, the array of focusing elements. The strips are formed and the focusing elements located relative to the strips such that at each of a plurality of viewing angles, a respective one strip from each set is viewed in response to incident light falling on a respective focusing element. The strips are constructed such that the device presents a cyclically repeating sequence of images as the device is viewed at successive viewing angles, the image sequence including a change in form of an image between a first and second form and then a reversal of the sequence back to the first form, the combined image sequences presenting a contiguous variation in the image form.

Abstract: A security device includes first and second diffractive structures contained within a surface relief structure. The structures are such that the device responds to illumination at a first, visible wavelength to generate a first, visible pattern while any pattern generated by the second structure is not substantially visible at that wavelength, and the device responds to illumination at a second wavelength substantially different from the first wavelength to generate a second pattern suitable for machine reading while any pattern generated by the first structure is substantially suppressed relative to the machine readable pattern at that wavelength.