Dynamic appearance-changing optical devices (DACOD) printed in a shaped magnetic field including printable fresnel structures
View Patent ↗A printed image is disclosed wherein the image may be in the form of an array of magnetically aligned platelets or flakes that may by uniform in shape and size and wherein the flakes are arranged in a particularly manner to form optically illusive images useful as security devices, or useful in beam steering applications. In one embodiment of this invention printed array is disclosed a plurality of concentric rings of magnetically aligned platelets disposed upon a substrate in the form of a Fresnel structure, preferably a Fresnel reflector. Advantageously, since the magnetic field can be controlled with respect to strength and direction, one can easily design a field that will correct for spherical aberration that would otherwise be present in a typical Fresnel reflector. In other embodiments of the invention optically illusive images of funnels, domes and cones are printed.
1. A security device comprising an image having a first plurality of at least 1000 magnetically alignable reflective flakes resting upon a surface of a substrate in a first pattern so as to define a ring or curve, wherein the first plurality of magnetically alignable reflective flakes are tilted at a first angle with respect to the surface of the substrate and wherein planes extending from surfaces of the first plurality of magnetically alignable reflective flakes intersect with one another so that the image appears to be a three-dimensional object with a non-planar surface, wherein a bright or dark kinematic spot moves within the image when the security device is tilted thereby providing dynamic shading to the image.
2. The security device as defined in claim 1 comprising a second plurality of magnetically alignable flakes resting upon the substrate in a corresponding pattern to the first pattern and wherein the second plurality of magnetically alignable reflective flakes are tilted at a second angle with respect to the surface of the substrate, wherein the second angle is different than the first angle and wherein planes extending from along surfaces of the second plurality of magnetically alignable reflective flakes intersect with each other.
3. The security device as defined in claim 2 , wherein the first plurality of magnetically alignable reflective flakes and the second plurality of magnetically alignable reflective flakes are distributed throughout the entire closed region and oriented in a predetermined pattern therein, wherein at least more than 50% of the first plurality of magnetically alignable reflective flakes and the second plurality of magnetically alignable reflective flakes are oriented such that lines normal to their reflecting surfaces converge along a line or to a point.
4. The security device as defined in claim 1 further comprising N groups of magnetically alignable reflective flakes resting upon the substrate in N patterns and wherein each group of the N groups of magnetically alignable flakes is tilted at the same angle with respect to the surface of the substrate and wherein each of the N groups of magnetically alignable reflective flakes are tilted at a different angle with respect to each other and with respect to the surface of the substrate, and wherein the planes of each group of the N groups of magnetically alignable reflective flakes intersect with each other.
5. The security device as defined in claim 1 wherein the first plurality of magnetically alignable reflective flakes includes more than 10,000 magnetically alignable reflective flakes.
6. The security device as defined in claim 1 , wherein the image forms a Fresnel structure.
7. The security device as defined in claim 1 , wherein the first plurality of magnetically alignable reflective flakes have a surface area between 100 μm 2 to 1 mm 2 and wherein the first plurality of magnetically alignable reflective flakes are within a range of thickness between 100 nm and 100 μm.
8. The security device as defined in claim 1 , wherein first plurality of the magnetically alignable reflective flakes are aligned with a magnetic field that is present entirely throughout a circular region.
9. The security device as defined in claim 1 , wherein the first plurality of the magnetically alignable reflective flakes blanket an entire circular region.
10. The security device as defined in claim 1 , wherein at least some of the first plurality of the magnetically alignable reflective flakes have gratings therein or thereon, and wherein the frequency and depth of the gratings are low so as to not have diffractive effects that can be seen by the naked human eye, and wherein the flakes having gratings are aligned along lines of the respective grating.
11. The security device as defined in claim 1 , wherein at least some of the first plurality of the magnetically alignable reflective flakes have gratings therein or thereon, and wherein the frequency of the gratings is less than 200 In/mm and wherein the depth of the grating is less than 100 microns.
12. The security device as defined in claim 1 , wherein the image is an image of selected from the group consisting of a cone, a sphere, a hemisphere, and a funnel.
13. The security device as defined in claim 1 , wherein the image forms a printed array of reflecting elements in the form of a Fresnel structure.
14. The security device as defined in claim 1 , wherein the first plurality of the magnetically alignable reflective flakes are uniform in shape.
15. The security device as defined in claim 1 , wherein the first plurality of the magnetically alignable reflective flakes are hexagonal in shape.
16. The security device as defined in claim 1 , wherein the first plurality of the magnetically alignable reflective flakes have a diffractive structure therein or thereon.
17. The security device as defined in claim 4 , wherein the N patterns are rings and form a Fresnel structure.
18. The security device as defined in claim 17 wherein the Fresnel structure is absent spherical aberration.
19. A security device as defined in claim 17 , wherein the Fresnel structure is a Fresnel reflector.
20. The security device as defined in claim 1 wherein the image exhibits a plurality of distinct rings when the security device is simultaneously irradiated with spatially separated light sources.
21. The security device comprising an image having a first plurality of at least 1000 magnetically alignable reflective flakes resting upon a surface of a substrate in a first pattern so as to define a ring or curve, wherein the first plurality magnetically alignable reflective flakes are tilted at a first angle with respect to the surface of the substrate and planes extending from surfaces of the first plurality of magnetically alignable reflective flakes intersect with one another so that the image appears to be a three-dimensional object with a non-planar surface, wherein a bright or dark kinematic spot moves within the image when the security device is tilted thereby providing dynamic shading to the image, wherein the image is a rolling hemisphere.
22. The security device as defined in claim 4 , wherein the N patterns are concentric rings of magnetically alignable reflective flakes, wherein the concentric rings of magnetically alignable reflective flakes populate a circular region and wherein the magnetically alignable reflective flakes defining the concentric rings form an increasing or decreasing angle with respect to the surface of the substrate from the outermost ring to the inner most ring.