Optically variable device with diffraction-based micro-optics, method of creating the same, and article employing the same
A security device includes an optically variable device (OVD) having diffraction-based micro-optics including at least one moiré magnified visual representation of a micro-object. A diffractive structure provides micro-objects with unique optical effects when the OVD is viewed through the micro-object structure from a predetermined relative observation point. In addition to magnifying the micro-objects, the diffractive structure can impart optical effects such as change in observed color, enhanced contrast, animation of the observed visual representation, and change in size or shape of the observed visual representation. The micro-objects and the diffractive structure can be disposed on the same or different portions of a substrate. A method of making OVDs, and an article employing such OVDs are also disclosed.
1. An optically variable device comprising:
a substrate including a first portion and a second portion;
at least one micro-object disposed on the first portion of said substrate; and
a diffractive structure disposed on the second portion of said substrate,
wherein at least one magnified visual representation of said micro-object is observed when said optically variable device is observed from a predetermined relative observation point and said micro-object is disposed between said diffractive structure and said observation point.
2. The optically variable device of claim 1 wherein said substrate comprises a generally planar member including a first side and a second side; wherein the first side is intermediate the second side and said predetermined relative observation point; and wherein the second side is distal from said observation point.
3. The optically variable device of claim 2 wherein the first and second portions of said substrate are both at or about the second side of said substrate.
4. The optically variable device of claim 3 wherein said micro-object is integral with said diffractive structure.
5. The optically variable device of claim 2 wherein the first portion of said substrate is at or about the first side of said substrate; and wherein the second portion of the substrate is at or about the second side of said substrate.
6. The optically variable device of claim 1 wherein said substrate comprises a material selected from the group consisting of a film, a laminate, a thread, a foil, a label, and a casting.
7. The optically variable device of claim 1 wherein said at least one micro-object comprises a plurality of micro-objects selectively organized in an object layer; wherein said object layer is coupled to said substrate by an adhesive; and wherein said object layer is removable from said substrate.
8. The optically variable device of claim 1 further comprising at least one additional layer selected from the group consisting of a metallic layer, a transparent refractive layer, a reflective layer, a protective layer, and an additional substrate.
9. The optically variable device of claim 1 wherein said diffractive structure comprises a plurality of diffractive elements selectively organized into a diffractive layer; and wherein said diffractive elements of said diffractive layer are structured to diffract light at different wavelengths depending upon the predetermined relative observation point from which said optically variable device is viewed.
10. The optically variable device of claim 9 wherein in addition to said at least one magnified visual representation of said micro-object, said diffractive elements are structured to impart at least one additional predetermined optical effect selected from the group consisting of a change in observed color, enhanced contrast between said at least one magnified visual representation of said micro-object and background, a movement or animation of said at least one magnified visual representation, a change in the size or shape of said magnified visual representation, and a transformation of said magnified visual representation into a different object or optical effect.
11. The optically variable device of claim 1 wherein said optically variable device has a thickness; and wherein the thickness of said optically variable device is about 5-250 microns.
12. An article comprising:
a surface; and
at least one security device coupled to said surface in order to resist counterfeiting of said article, said security device including at least one optically variable device with diffraction-based micro-optics, said optically variable device comprising:
a substrate including a first portion and a second portion,
at least one micro-object disposed on the first portion of said substrate, and
a diffractive structure disposed on the second portion of said substrate,
wherein at least one magnified visual representation of said micro-objects is observed when said optically variable device is observed from a predetermined relative observation point from and said micro-object is disposed between said diffractive structure and said observation point.
13. The article of claim 12 wherein said substrate comprises a generally planar member including a first side and a second side; wherein the first side is intermediate the second side and said observation point; and wherein the second side is distal from said observation point.
14. The article of claim 13 wherein the first and second portions of said substrate are both at or about the second side of said substrate.
15. The article of claim 13 wherein the first portion of said substrate is at or about the first side of the substrate; and wherein the second portion of the substrate is at or about the second side of said substrate.
16. The article of claim 12 wherein said at least one micro-object comprises a plurality of micro-objects selectively organized in an object layer; wherein said diffractive structure comprises a plurality of diffractive elements selectively organized into a diffractive layer; and wherein said diffractive elements of said diffractive layer diffract light at different wavelengths depending upon the predetermined relative observation point from which said optically variable device is viewed.
17. The article of claim 12 wherein in addition to said at least one magnified visual representation of said micro-object, said diffractive elements impart at least one additional predetermined optical effect selected from the group consisting of a change in observed color, enhanced contrast between said at least one magnified visual representation of said micro-object and background, a movement or animation of said at least one magnified visual representation of said micro-object, a change in the size or shape of said magnified visual representation, and a transformation of said magnified visual representation into a different object or optical effect.