Method of making an array of aberrated optical elements

1. A method of making a substrate for assembly into a production tool to make an array of aberrated optical elements, said method comprising the steps of:

providing a substrate having a first surface with forming elements thereon, wherein the geometry of the forming elements corresponds to the geometry of non-aberrated optical elements in an analogous array comprising mutually intersecting faces;

performing a working step by application of one of pressure, energy, chemicals, and impingement of particles to the first surface at a localized region on the first surface of the substrate such that face smoothness of the first surface is substantially the same as the non-aberrated optical elements, said working step is of a magnitude sufficient to aberrate forming elements in an affected site including and surrounding the localized region on the first surface;

wherein the optical elements are retroreflective cube corner elements with three mutually perpendicular faces that intersect with each other at edges forming three dihedral angles;

wherein said working step results in a dihedral angle of one or more of the forming elements being unequal to 90°;

wherein the dihedral angle is the angle of a corner element between mutually intersecting faces of the forming element;

wherein a second surface opposite the first surface is not worked;

wherein said working step is a controlled working step; and

wherein the substrate is electroformed nickel.

2. A method as set forth in claim 1 , wherein said working step is performed so that the array has a greater mean geometric divergence than the analogous array.

3. A method as set forth in claim 1 , wherein said working step is performed so that the array has a total retroreflectance that is at least 90% of that of the analogous array.

4. A method as set forth in claim 1 , wherein the optical elements are micro-optical elements.

5. A method as set forth in claim 1 , wherein the substrate is a master substrate, a copy of another substrate, or an assembly substrate.

6. A method as set forth in claim 1 , wherein said working step is performed while an electroformed copy is still attached to the substrate.

7. A method as set forth in claim 1 , wherein the magnitude of the working is sufficiently small such that smoothness of the faces of the forming elements is not substantially damaged, and/or such that sharpness of edges of the forming elements is not substantially damaged.

8. A method as set forth in claim 1 , wherein the substrate has a thickness in the range of about 0.01 mm to about 2.0 mm.

9. A method as set forth in claim 1 , wherein said working step is accomplished by the application of chemicals.

10. A method as set forth in claim 1 , wherein said working step comprises working a plurality of localized regions on the first surface of the substrate.

11. A method as set forth in the claim 1 , wherein the magnitude of the working step is the same in at least some of the plurality localized regions.

12. A method as set forth in claim 1 , wherein the magnitude of the working step varies in at least some of the plurality localized regions.

13. A method comprising the step of assembling a substrate made by the method of claim 1 into the production tool.

14. A method comprising the step of using a production tool made by the method of claim 13 to form the array of retroreflective elements.

15. A method as set forth in claim 1 , wherein the work step comprises impingement of particles to the first surface at the localized region.

16. A method of making a substrate for assembly into a production tool to make an array of aberrated optical elements, said method comprising the steps of:

providing a substrate having a first surface with forming elements thereon, wherein the geometry of the forming elements corresponds to the geometry of non-aberrated optical elements in an analogous array;

performing a working step by application of one of pressure, energy, chemicals, and the impingement of particles at a localized region on the first surface of the substrate such that sharpness of edges of the forming elements is not damaged, said working step is of a magnitude sufficient to aberrate forming elements in an affected site including and surrounding the localized region on the first surface;

wherein the optical elements are retroreflective cube corner elements with three mutually perpendicular faces that intersect with each other at edges forming three dihedral angles;

wherein said working step results in a dihedral angle of more than one of the forming elements being unequal to 90°;

wherein the dihedral angle is the angle of a corner element between mutually intersecting faces of the forming element;

wherein a second surface opposite the first surface is not worked;

wherein said working step is a controlled working step; and

wherein the substrate is electroformed nickel.

17. A method of making a substrate for assembly into a production tool to make an array of aberrated optical elements, said method comprising the steps of:

providing a substrate having a thickness of greater than 10.00 mm and a first surface with forming elements thereon, wherein the geometry of the forming elements corresponds to the geometry of non-aberrated optical elements in an analogous array;

performing a working step by application of one of pressure, energy, chemicals, and the impingement of particles at a localized region on the first surface of the substrate, said working step is of a magnitude sufficient to aberrate forming elements in an affected site including and surrounding the localized region on the first surface;

wherein said working step is performed so that the array has a total retroreflectance that is at least 90% of that of the analogous array;

wherein the optical elements are retroreflective cube corner elements with three mutually perpendicular faces that intersect with each other at edges forming three dihedral angles;

wherein said working step results in a dihedral angle of one or more of the forming elements being unequal to 90°;

wherein the dihedral angle is the angle of a corner element between mutually intersecting faces of the forming element;

wherein a second surface opposite the first surface is not worked;

wherein said working step is a controlled working step; and

wherein the substrate is electroformed nickel.