Method of making a microlens array and mold

• US 5,300,263 A
• Filed: 10/28/1992
• Issued: 04/05/1994
• Est. Priority Date: 10/28/1992
• Status: Expired due to Term

• Current Assignee: Minnesota Mining and Manufacturing Co (3M Company)
• Original Assignee: Minnesota Mining and Manufacturing Co (3M Company)
• Inventors: Aastuen, David J. W., Hoopman, Timothy L.
• Primary Examiner(s): Lowe, James
• Application Number:
  US07/967,453
• Time in Patent Office: 524 Days
• Field of Search: 264/1.7, 264/1.9, 264/2.5, 264/1.4, 425/808
• US Class Current: 264/2.5
• CPC Class Codes: B29C 33/0022 Multi-cavity moulds B29C33/301 takes precedence
• CPC Class Codes: B29C 33/3842 Manufacturing moulds, e.g. shaping the mould surface by machining
• CPC Class Codes: B29C 33/3878 used as masters for making successive impressions
• CPC Class Codes: B29C 33/3892 Preparation of the model, e.g. by assembling parts
• CPC Class Codes: B29D 11/00278 Lenticular sheets B29D11/00269 takes precedence
• CPC Class Codes: B29L 2011/0016 Lenses
• CPC Class Codes: G02B 3/0025 Machining, e.g. grinding, polishing, diamond turning, manufacturing of mould parts
• CPC Class Codes: G02B 3/0031 Replication or moulding, e.g. hot embossing, UV-casting, injection moulding
• CPC Class Codes: G02B 3/0056 arranged along two different directions in a plane, e.g. honeycomb arrangement of lenses G02B3/0043 takes precedence; miniaturised objectives for electronic devices employing wafer level optics G02B13/0085
• CPC Class Codes: Y10S 425/808 Lens mold

Abstract

A method of making a microlens array and mold, and the articles made therefrom. The method involves forming a plurality of adjacent receptacles on a surface and partially filling the receptacles with a hardenable liquid, thereby forming a meniscus in each receptacle. A lens material can then be applied to the menisci, thereby forming an array of generally spherical microlenses. In one embodiment, the perimeters of the microlenses are modified rectangles in that each edge of the lens is a symmetrical elliptical arc, the ends of which terminate at the corners of the rectangle, and the middle of which curves toward the center of the rectangle.

Claims

1. A method of making a microlens array mold, comprising:

(a) forming an array of pyramid-shaped receptacles having parallelogram-shaped apertures;

(b) applying a hardenable liquid to the array of pyramid-shaped receptacles so that the receptacles are partially filled with the liquid, whereby a plurality of menisci are formed in the receptacles; and

(c) hardening the liquid to form a plurality of concave lens mold surfaces in the pyramid-shaped receptacles, thereby forming a mold capable of forming an array of generally spherical microlenses.

2. The method of claim 1, wherein step (a) comprises:

providing a first plurality of parallel grooves in a substrate surface;

providing a second plurality of parallel grooves in the substrate surface, wherein the second plurality of grooves intersects the first plurality of grooves; and

forming a negative replica of the substrate surface, thereby forming a first and second plurality of parallel raised walls corresponding to the first and second plurality of parallel grooves, whereby the pluralities of intersecting walls define an array of receptacles having parallelogram-shaped apertures.

3. The method of claim 2, wherein the first plurality of parallel grooves is perpendicular to the second plurality of parallel grooves.

4. The method of claim 1, further comprising, after step (c), the following steps;

(d) applying a conductive layer to the concave lens mold surfaces; and

(e) electroforming the conductive layer to form a nickel negative of the conductive layer, thereby forming a plurality of convex lens mold surfaces in the receptacles.

5. The method of claim 4, further comprising, after step (e), the step of electroforming the nickel negative to form a nickel positive of the conductive layer, thereby forming a plurality of concave lens mold surfaces corresponding to the receptacles.

6. The method of claim 1, wherein the receptacle apertures are rectangular and are defined by a first plurality of parallel walls which are perpendicular to and intersect a second plurality of parallel walls, further comprising, before step (b), the steps of:

providing a first plurality of arcuate grooves in the first plurality of parallel walls, wherein the arcuate grooves are parallel to the second plurality of parallel walls, and wherein each arcuate groove is centered between and spans the distance between each pair of adjacent walls in the second plurality of parallel walls; and

providing a second plurality of arcuate grooves in the second plurality of parallel walls, wherein the arcuate grooves are parallel to the first plurality of walls, and wherein each arcuate groove is centered between and spans the distance between each pair of adjacent walls in the first plurality of parallel walls.

7. The method of claim 6, wherein the shape of each arcuate groove is defined by the projection of the intersection of a desired spherical lens surface with the wall into a plane which has its surface normal oriented parallel to the length of the arcuate groove.

8. The method of claim 1, wherein the pyramid-shaped receptacles have flat bottoms.

9. A method of making a microlens array, comprising:

(a) forming an array of receptacles having generally polygonal apertures;

(b) applying a hardenable liquid to the array of receptacles so that the receptacles are partially filled with the liquid, whereby a plurality of menisci are formed in the receptacles;

(c) hardening the liquid to form a plurality of concave lens mold surfaces in the receptacles, thereby forming a mold capable of forming an array of generally spherical microlenses;

(d) applying a hardenable lens material to the array; and

(e) hardening the lens material, thereby forming an array of generally spherical microlenses.

10. The method of claim 9, wherein step (a) comprises:

providing a first plurality of parallel grooves in a substrate surface;

providing a second plurality of parallel grooves in the substrate surface, wherein the second plurality of grooves intersects the first plurality of grooves; and

forming a negative replica of the substrate surface, thereby forming a first and second plurality of parallel raised walls corresponding to the first and second plurality of parallel grooves, whereby the pluralities of intersecting walls define an array of receptacles having generally polygonal apertures.

11. The method of claim 10, wherein the first plurality of parallel grooves is perpendicular to the second plurality of parallel grooves.

12. The method of claim 10, wherein the grooves are V-shaped.

13. The method of claim 10, wherein the grooves are provided by a machining process.

14. The method of claim 9, further comprising, after step (c), the following steps:

applying a conductive layer to the concave lens mold surfaces; and

electroforming the conductive layer to form a nickel negative of the conductive layer, thereby forming a plurality of convex lens mold surfaces in the receptacles.

15. The method of claim 14, further comprising, after electroforming the conductive layer, the step of electroforming the nickel negative to form a nickel positive of the conductive layer, thereby forming a plurality of concave lens mold surfaces corresponding to the receptacles.

16. The method of claim 9, wherein the receptacle apertures are rectangular and are defined by a first plurality of parallel walls which are perpendicular to and intersect a second plurality of parallel walls, further comprising, before step (b), the steps of:

providing a first plurality of arcuate grooves in the first plurality of parallel walls, wherein the arcuate grooves are parallel to the second plurality of parallel walls, and wherein each arcuate groove is centered between and spans the distance between each pair of adjacent walls in the second plurality of parallel walls; and

providing a second plurality of arcuate grooves in the second plurality of parallel walls, wherein the arcuate grooves are parallel to the first plurality of walls, and wherein each arcuate groove is centered between and spans the distance between each pair of adjacent walls in the first plurality of parallel walls.

17. The method of claim 16, wherein the shape of each arcuate groove is defined by the projection of the intersection of a desired spherical lens surface with the wall into a plane which has its surface normal oriented parallel to the length of the arcuate groove.

18. The method of claim 9, wherein the receptacle apertures are triangular.

19. A method of making a microlens array mold, comprising:

(a) providing a first plurality of parallel grooves in a substrate surface;

(b) providing a second plurality of parallel grooves in the substrate surface, wherein the second plurality of grooves intersects the first plurality of grooves;

(c) forming a negative replica of the substrate surface, thereby forming a first and second plurality of parallel raised walls corresponding to the first and second plurality of parallel grooves, whereby the pluralities of intersecting walls define an array of receptacles having generally polygonal apertures;

(d) applying a hardenable liquid to the array of receptacles so that the receptacles are partially filled with the liquid, whereby a plurality of menisci are formed in the receptacles; and

(e) hardening the liquid to form a plurality of concave lens mold surfaces in the receptacles, thereby forming a mold capable of forming an array of generally spherical microlenses.

20. The method of claim 19, further comprising, after step (e), the following steps;

(f) applying a conductive layer to the concave lens mold surfaces; and

(g) electroforming the conductive layer to form a nickel negative of the conductive layer, thereby forming a plurality of convex lens mold surfaces in the receptacles.

21. The method of claim 20, further comprising, after step (g), the step of electroforming the nickel negative to form a nickel positive of the conductive layer, thereby forming a plurality of concave lens mold surfaces corresponding to the receptacles.

22. The method of claim 19, wherein the first plurality of parallel grooves is perpendicular to the second plurality of parallel grooves.

23. A method of making a microlens array mold, comprising:

(a) forming an array of receptacles having rectangular apertures defined by a first plurality of parallel walls which are perpendicular to and intersect a second plurality of parallel walls;

(b) providing a first plurality of arcuate grooves in the first plurality of parallel walls, wherein the arcuate grooves are parallel to the second plurality of parallel walls, and wherein each arcuate groove is centered between and spans the distance between each pair of adjacent walls in the second plurality of parallel walls;

(c) providing a second plurality of arcuate grooves in the second plurality of parallel walls, wherein the arcuate grooves are parallel to the first plurality of walls, and wherein each arcuate groove is centered between and spans the distance between each pair of adjacent walls in the first plurality of parallel walls;

(d) applying a hardenable liquid to the array of receptacles so that the receptacles are partially filled with the liquid, whereby a plurality of menisci are formed in the receptacles; and

(e) hardening the liquid to form a plurality of concave lens mold surfaces in the receptacles, thereby forming a mold capable of forming an array of generally spherical microlenses.

24. The method of claim 23, wherein the shape of each arcuate groove is defined by the projection of the intersection of a desired spherical lens surface with the wall into a plane which has its surface normal oriented parallel to the length of the arcuate groove.

25. A method of making a microlens array mold, comprising:

(a) forming an array of tetrahedral receptacles having triangular apertures;

(b) applying a hardenable liquid to the array of receptacles so that the receptacles are partially filled with the liquid, whereby a plurality of menisci are formed in the receptacles; and

(c) hardening the liquid to form a plurality of concave lens mold surfaces in the triangular receptacles, thereby forming a mold capable of forming an array of generally spherical microlenses.

26. The method of claim 25, wherein each tetrahedral receptacle is defined by three walls and the receptacle apertures are equilateral triangles, and further comprising, after step (a) and before step (b), the step of providing one arcuate groove through the top of each wall of each receptacle, wherein each groove is centered between and spans the distance between each adjacent wall.

27. The method of claim 26, wherein the shape of each arcuate groove is defined by the projection of the intersection of a desired spherical lens surface with the wall into a plane which has its surface normal oriented parallel to the length of the arcuate groove.