| 摘要 |
An optical security device 200, has a relief structure 204 provided on a transparent or partially transparent substrate 202, and a coating 206 provided 5 over the relief structure 204, wherein under incident light the relief structure 204 produces a first image 102 and a second image 104, such that when the device 200 is viewed in transmission the first image 102 and second image 104 are visible, and when the device 200 is viewed in reflection the first image 102 is visible and the second image 104 is either weakly visible or not visible. This may 10 be achieved by providing a coating 206 of such a high refractive index that the depth of the portion 210 of the relief structure 204 that produces the second image 104 is insufficient for the second image 104 to be visible in reflection. |
