Security feature based on a single axis alignment of mirrors in a structured surface that forms a micro mirror array
The disclosure relates to an optical security feature that is based on a single axis alignment of mirrors or facets in a structured surface that forms a micro mirror array. In an aspect, a device is described that includes a reflecting structure on a first layer, where the reflecting structure has a top surface with multiple embossed facets arranged in a spatial orientation that produces a flat ring optical effect upon incidence of light. In another aspect, a method for making the device is described that provides a reflecting layer and produces the reflecting structure on the reflecting layer with multiple facets arranged in the spatial orientation to produce the flat ring optical effect. In yet another aspect, an apparatus for making the device is described that includes a pressing device and a stamping device to transfer a pattern of the reflecting structure to a reflecting material.
1. An optically variable device, comprising:
a first layer; and
a reflecting structure disposed on the first layer,
the reflecting structure having a top surface including multiple embossed facets,
the facets being arranged in a spatial orientation that produces a flat ring optical effect upon incidence of light,
a facet, of the facets, being ordered along a first axis and tilted about a second axis perpendicular to the first axis, and
the facet being configured to produce a reflection from the incidence of light that is one or more of:
at least partially diffuse for the first axis, or
at least partially specular for the second axis.
2. The optically variable device of claim 1 , wherein in the spatial orientation each facet is ordered along the first axis and tilted at pseudo-random angles about the second axis.
3. The optically variable device of claim 1 , wherein, for the facet, the first axis corresponds to an axis along a longest dimension of the facet and the second axis corresponds to an axis along a shortest dimensions of the facet.
4. The optically variable device of claim 2 , wherein the pseudo-random angles for each facet range from O to ±90°.
5. The optically variable device of claim 1 , wherein the facet is configured to produce the reflection from the incidence of light that is at least partially diffuse for the first axis and at least partially specular for the second axis.
6. The optically variable device of claim 1 , wherein in the spatial orientation the facets are ordered along radial lines from a center of the reflecting structure.
7. The optically variable device of claim 1 , wherein the facets are of the same size.
8. The optically variable device of claim 1 , wherein the facets vary in size along radial lines from a center of the reflecting structure.
9. The optically variable device of claim 1 , wherein the reflecting structure includes a reflecting material and is integrated with the first layer.
10. The optically variable device of claim 1 , wherein the first layer is made of one of a polymeric material, a plastic material, or a metallic material.
11. The optically variable device of claim 1 , wherein a top surface of at least a subset of the facets is planar.
12. The optically variable device of claim 1 , wherein a top surface of at least a subset of the facets includes microstructures.
13. The optically variable device of claim 1 , wherein the reflecting structure with the facets corresponds to a micro-mirror array.
14. The optically variable device of claim 1 , wherein, in the spatial orientation, the facets are configured to emulate an outside surface of a reflecting half sphere.
15. A method for making an optically variable device, comprising:
providing a reflecting layer; and
producing a reflecting structure on the reflecting layer having multiple facets,
the facets being arranged in a spatial orientation that produces a flat ring optical effect upon incidence of light,
a facet, of the facets, being ordered along a first axis and tilted about a second axis perpendicular to the first axis, and
the facet being configured to produce a reflection from the incidence of light that is one or more of:
at least partially diffuse for the first axis, or
at least partially specular for the second axis.
16. The method of claim 15 , wherein providing the reflecting layer includes providing the reflecting layer that is a top portion of a first layer or that is disposed on a top surface of the first layer.
17. The method of claim 15 , wherein producing the reflecting structure on the reflecting layer includes applying a cast for embossing the facets on a top surface of the reflecting layer.
18. The method of claim 15 , wherein in the spatial orientation each facet is ordered along the first axis and tilted at pseudo-random angles about the second axis.
19. The method of claim 15 , wherein, for the facet, the first axis corresponds to an axis along a longest dimension of the facet and the second axis corresponds to an axis along a shortest dimensions of the facet.
20. The method of claim 18 , wherein the pseudo-random angles for each facet range from O to ±90°.
21. The method of claim 18 , wherein the facet is configured to produce the reflection from the incidence of light that is at least partially diffuse for the first axis and at least partially specular for the second axis.
22. The method of claim 15 , wherein in the spatial orientation the facets are ordered along radial lines from a center of the reflecting structure.
23. An apparatus for making an optically variable device, comprising:
a pressing device; and
a stamping device coupled to the pressing device and configured to transfer a pattern to a reflecting material upon an exertion of pressure by the pressing device,
the pattern including a reflecting structure having multiple facets arranged in a spatial orientation that produces a flat ring optical effect upon incidence of light on the patterned reflective material.
24. The apparatus of claim 23 , wherein in the spatial orientation each facet is ordered along a first axis and tilted at pseudo-random angles about a second axis perpendicular to the first axis.
25. The apparatus of claim 24 , wherein, for each facet, the first axis corresponds to an axis along a longest dimension of the facet and the second axis corresponds to an axis along a shortest dimensions of the facet.
26. The apparatus of claim 24 , wherein the pseudo-random angles for each facet range from O to ±90°.