| 摘要 |
A security device comprising a surface relief microstructure which, in response to incident radiation, replays a hologram viewable within a viewing zone, the hologram comprising at least a first, holographic image element (5 0, 52) in an image plane spaced from the surface of the microstructure. The device exhibits at least one further image (54) in a plane spaced from said image plane of the first holographic element (50, 52). The spacing between t he first holographic element image plane and the plane of the further image is such that, on tilting the device, the first holographic image element (50, 5 2) exhibits apparent movement relative to the further image (54), the rate of movement being at least 6mm per radian of tilt, wherein, when expressed in radions, said rate of parallexe movement per radion equals the spacing betwe en said phones and the product of the rate of movement and the included angle o f the viewing zone defining a distance at least 20 % of the dimension of the device in the direction of movement of the first holographic image element.< /SDOAB> |
