| 摘要 |
A holographic security device comprising at least first and second diffractive image generating structures (11,13) recorded in respective sets of substantially non- overlapping regions of a record medium, the regions of one set being interleaved with regions of the other set, whereby both interleaved regions are substantially non- visible to the unaided eye. The holographic security device generates two or more holographic images viewed from separate and/or overlapping viewing directions around the device and seen by tilting the device, and each particular holographic image in a viewing direction is generated by the diffractive image generating structure (11,13) associated with one set of interleaved lines. The first diffractive image generating structure has been formed to have a diffuse diffractive replay and the second diffractive image generating structure has been formed to have a non- diffuse or specular diffractive replay. |
