| 摘要 |
A transitory image structure comprises linear markings (1-10) on a substrate. The linear markings define image (31, 32) and background (30) portions respectively, the markings cooperating together such that an image generated by the image portion is not visible from all viewing angles. At least some of the lines of the markings of at least one of the portions have a physical characteristic, such as thickness, which varies in a substantially random manner along their lengths. |
