Gradial zone lens and method of fabrication

• US 5,629,800 A
• Filed: 06/05/1995
• Issued: 05/13/1997
• Est. Priority Date: 12/16/1993
• Status: Expired due to Fees

• Current Assignee: Eastman Kodak Company
• Original Assignee: Eastman Kodak Company
• Inventors: Hamblen, David P.
• Primary Examiner(s): Henry, Jon W.
• Application Number:
  US08/464,487
• Time in Patent Office: 708 Days
• Field of Search: 359/565, 359/566, 359/569, 359/570, 359/571, 359/742, 264/1.31, 264/1.32, 264/1.33, 264/1.7, 264/2.1
• US Class Current: 359/565
• CPC Class Codes: B29C 2035/0827 using UV radiation
• CPC Class Codes: B29C 2791/001 Shaping in several steps
• CPC Class Codes: B29C 35/0888 using transparant moulds
• CPC Class Codes: B29C 41/04 Rotational or centrifugal casting, i.e. coating the inside of a mould by rotating the mould
• CPC Class Codes: B29C 41/045 the axis being placed vertically, e.g. spin casting
• CPC Class Codes: B29D 11/00355 with a refractive index gradient
• CPC Class Codes: B29D 11/00471 made by rotational casting B29D11/00115 takes precedence
• CPC Class Codes: B29K 2105/0002 monomers or prepolymers
• CPC Class Codes: B29L 2011/0016 Lenses
• CPC Class Codes: G02B 3/0087 with index gradient
• CPC Class Codes: G02B 5/1876 Diffractive Fresnel lenses; Zone plates; Kinoforms G02B5/1842, G02B5/1847 take precedence; optical systems having diffractive correction means G02B27/0037; Fresnel lenses operating by refraction G02B3/08

Abstract

Diffractive lenses having gradial zones (62, 70, 78, 90, 98, 106, 114) are formed by separately, sequentially spin casting and polymerizing successive radial zones of the lens to produce optical phase differences of 2π between adjacent gradial zones. Diffractive lenses may be molded in plano-plano(60), plano-concave (68) and plano-convex (76) geometries and also may be combined with conventional plano-plano (84), convex-convex (92), plano-concave (100) and plano-convex (108) refractive lenses.

Claims

1. A method of making a diffractive lens, comprising the steps of:

providing a mold having an axis and a mold cavity symmetrically surrounding the axis, the cavity having a desired geometry for at least one exterior surface of the diffractive lens;

spinning the mold about the axis;

injecting a first volume of a first optically transparent material into the cavity during the spinning, thereby placing the first volume at a periphery of the cavity to define a radially outer zone of the diffractive lens;

curing the first volume within the outer zone to at least partially solidify the material;

injecting a second volume of a second optically transparent material into the cavity during the spinning, thereby placing the second volume against an inner periphery of the outer zone to define a first radially inner zone of the diffractive lens;

curing the second volume within the first inner zone to at least partially solidify the material; and

repeating the injecting and curing steps to define and cure subsequent inner zones of the diffractive lens until the mold cavity is filled with concentric zones of cured material, the cross sectional areas of the zones and the first and second materials being chosen to produce an optical phase difference between adjacent zones of 2π

; and

the first and second optically transparent materials defining alternate ones of the zones.

2. The method of claim 1, wherein the material is a polymer and the curing is achieved by subjecting the volumes of polymer to radiation to polymerize the monomer.

3. A method according to claim 1, wherein the cross sectional area of each zone is equal for all zones of the diffractive lens.

4. A method according to claim 1, further comprising the step of placing a previously made refractive lens in the mold cavity coaxially with the axis of the mold, whereby the zones of the diffractive lens are applied to a surface of the refractive lens.

5. A method according to claim 1, wherein the mold cavity is shaped to provide a plano/plano diffractive lens.

6. A method according to claim 1, wherein the mold cavity is shaped to provide a plano/convex diffractive lens.

7. A method according to claim 1, wherein the mold cavity is shaped to provide a plano/concave diffractive lens.

8. A diffractive lens comprising a plurality of individual, concentric annular zones of material, the zones extending from a central radially innermost zone to a concentric radially outermost zone, the cross sectional areas of the plurality of concentric annular zones and the indicies of refraction of the plurality of concentric annular zones being chosen so that first and second zones of material of said plurality of individual concentric annular zones of material have a first and second index of refraction, respectively, and other of said plurality of individual concentric annular zones of materials have alternately repeating first and second indicies of refraction to produce an optical phase difference between adjacent zones of 2π

;

whereby the alternating zones function as a radial grating to diffract light incident upon the lens.

9. A diffractive lens according to claim 8, wherein the material is a radiation-cured polymer.

10. A diffractive lens according to claim 8, further comprising a refractive lens with the diffractive lens applied coaxially to a surface of the refractive lens.

11. A diffractive lens according to claim 8, further comprising a plano-plano element with the diffractive lens applied coaxially to a surface of the plano-plano element.

12. A diffractive lens according to claim 10, wherein the refractive lens is a convex/convex lens.

13. A diffractive lens according to claim 10, wherein the refractive lens is a plano/convex lens and the diffractive lens is applied to the plano surface.

14. A diffractive lens according to claim 10, wherein the refractive lens is a plano/convex lens and the diffractive lens is applied to the convex surface.

15. A diffractive lens according to claim 10, wherein the refractive lens is a plano/concave lens and the diffractive lens is applied to the concave surface.

16. A diffractive lens according to claim 8, wherein the lens is a plano-plano diffractive lens.

17. A diffractive lens according to claim 8, wherein the lens is a plano-convex diffractive lens.

18. A diffractive lens according to claim 8, wherein the lens is a plano-concave diffractive lens.