| 摘要 |
A security device is disclosed, comprising: an array of focusing elements, each focusing element being adapted to focus light in at least a first direction, the focusing elements being arranged on a regular grid in at least one dimension; and an array of image elements overlapping the array of focussing elements. The image elements are arranged based on a repeating unit cell defining image element positions, the periodicity of the unit cells being substantially the same as that of the grid on which the array of focusing elements is arranged. The unit cell defines a set of image element positions therewithin, each image element position within the unit cell being assigned to carry an image element of a respective corresponding image. Depending on the viewing angle, the array of focusing elements directs light from selected image element positions to the viewer, such that as the device is tilted different ones of the respective images are displayed by the image elements at the selected image element positions in combination, sequentially. A centre area of each unit cell, comprising one or more image element positions, is assigned to carry image element(s) of a corresponding centre image, the centre area being larger than each outer area of the unit cell, the outer areas being located outside the centre area and assigned to carry image element(s) of other respective images, such that the range of viewing angles over which the centre image is displayed to a viewer is greater than the range of viewing angles over which each other image is displayed. |
