| 摘要 |
An optical device for providing a synthetic integral image (25) comprises a polymer foil stack. A first interface of the polymer foil stack comprises optically distinguishable image data bearer structures (16A-C) in a first array. A second interface of the polymer foil stack has focusing elements (1) in a second array. A ratio between distances between neighboring objects in the first array and of focusing elements in the second array in a first direction is different from a ratio between distances between neighboring objects in the first array and of focusing elements in second array in a second direction. This leads to that the synthetic integral image corresponding to the image data bearer structures is perceptible with requested proportions when the polymer foil stack is given a certain curvature. Also polymer foil stacks giving rise to synthetic integral image only when viewed from a very short distance are described. The appearance of the synthetic integral image during bending or moving of the polymer foil stack is used for authentication. A change in apparent image depth during rotation is alternatively used for authentication. |
