Optical device having an illusive optical effect and method of fabrication
A method is provided for manufacturing an image on a substrate, wherein the image includes an indicia and a frame. The method includes covering at least a portion the substrate with a carrier comprising magnetically alignable flakes, aligning the magnetically alignable flakes with a magnetic field of a magnetic assembly comprising a metal plate with an opening, and solidifying the carrier. The frame is formed at an edge of the opening and the indicia is visible within the frame. The magnetic assembly includes two magnets disposed so that the North pole of one magnet and the South pole of another magnet are proximate to the metal plate at opposite sides of the opening.
1. An apparatus for aligning magnetically alignable flakes dispersed in a carrier, comprising a metal sheet with an opening, and first and second permanent magnets disposed so that a North pole of the first permanent magnet and a South pole of the second permanent magnet are proximate to the metal sheet at opposite sides of the opening, wherein a magnetic flux density along a surface of the metal sheet is lowest at a half-way point to the opening in a middle of the metal sheet and increases on both sides of the middle towards an end of the metal sheet and towards the opening in the metal sheet.
2. The apparatus as defined in claim 1 , wherein the metal sheet has a thickness in the range of from 0.004 inch to 0.1 inch.
3. The apparatus as defined in claim 1 , wherein the metal sheet comprises a material having permeability in the range of from 0.01 to 0.3 H/m.
4. The apparatus as defined in claim 1 , wherein the opening has a shape of a circle, a square, or a hexagon.
5. The apparatus as defined in claim 1 , further comprising a cylinder, wherein the metal sheet is at the surface of a cylinder.
6. The apparatus as defined in claim 1 , wherein the first permanent magnet and the second permanent magnet are enclosed in a magnetically-soft yoke.
7. The apparatus as defined in claim 1 , wherein the metal sheet is disposed on top of the first and second permanent magnets.
8. The apparatus as defined in claim 1 , wherein the metal sheet is disposed between the North pole of the first permanent magnet and the South pole of the second permanent magnet.
9. The apparatus as defined in claim 1 , wherein the North pole of the first magnet and the South pole of the second magnet lie in a plane of the metal sheet and the opening.
10. The apparatus as defined in claim 1 , wherein the metal sheet is disposed below the top of the first and second permanent magnets.
11. The apparatus as defined in claim 1 , wherein the metal sheet is embedded into a roller.
12. The apparatus as defined in claim 1 , wherein the metal sheet has a planar surface.
13. The apparatus as defined in claim 1 , wherein the metal sheet has a curved surface.
14. The apparatus as defined in claim 1 , wherein the first permanent magnet and the second permanent magnet create a magnetic field that bends at an edge of the opening in the metal sheet.
15. The apparatus as defined in claim 1 , wherein the first permanent magnet and the second permanent magnet create a magnetic field that is parallel to a surface of the metal sheet within the opening.
16. The apparatus as defined in claim 1 , wherein the opening is at least 8 mm wide.
17. The apparatus as defined in claim 5 , wherein the cylinder includes at least one metal sheet, at least one first permanent magnet, and at least one second permanent magnet.
18. The apparatus as defined in claim 17 , wherein a number of metal sheets, first permanent magnets, and second permanent magnets varies depending on a size of the cylinder.
19. The apparatus as defined in claim 17 , wherein the cylinder includes four of each of the metal sheet, first permanent magnet, and second permanent magnet.
20. The apparatus as defined in claim 1 , further comprising a belt supporting a substrate to be printed.