| 摘要 |
<p>An optical device for authenticating articles of value, the optical device including: a first diffractive structure for generating a first diffractive image; a second diffractive structure for generating a second diffractive image; and a non-diffractive structure; wherein, the first and second diffractive structures, and the non-diffractive structure, are positioned relative to each other such that when viewed from a first angle, both the first and second diffractive images are visible, and when viewed from a second angle, the first diffractive image is visible while the second diffractive image is not visible. Fig. 1 Fig. 2A Fig. 26</p> |
