LED with compound encapsulant lens

• US 7,798,678 B2
• Filed: 12/30/2005
• Issued: 09/21/2010
• Est. Priority Date: 12/30/2005
• Status: Expired due to Fees

• Current Assignee: 3M Innovative Properties Company (3M Company)
• Original Assignee: 3M Innovative Properties Company (3M Company)
• Inventors: Destain, Patrick R.
• Primary Examiner(s): O'Shea; Sandra L
• Assistant Examiner(s): CARTER, WILLIAM JOSEPH
• Application Number:
  US11/322,801
• Publication Number:
  US 20070152231A1
• Time in Patent Office: 1,726 Days
• Field of Search: 362/800, 362/268, 362/335, 362/336, 362/331
• US Class Current: 362/311.02
• CPC Class Codes: H01L 2224/48091 Arched
• CPC Class Codes: H01L 2224/48247 connecting the wire to a bond pad of the item
• CPC Class Codes: H01L 2924/00012 Relevant to the scope of the group, the symbol of which is combined with the symbol of this group
• CPC Class Codes: H01L 2924/00014 the subject-matter covered by the group, the symbol of which is combined with the symbol of this group, being disclosed without further technical details
• CPC Class Codes: H01L 2924/181 Encapsulation
• CPC Class Codes: H01L 33/58 Optical field-shaping elements
• CPC Class Codes: Y10S 362/80 Light emitting diode

Abstract

An LED light source includes an LED emitter and an encapsulant that at least partially surrounds the emitter. The encapsulant includes an inner lens and an outer lens, the inner lens having a refractive index less than, and in some cases about 70 to 80% of, the refractive index of the outer lens. The inner lens and outer lens can contact each other along a curved surface, and in some cases the inner lens is substantially plano-convex and the outer lens is meniscus. The inner lens produces a first virtual image of the emitter and the outer lens produces a second virtual image, and the first virtual image is disposed between the emitter and the second virtual image. The LED light source is capable of providing uniform illumination in a compact space.

Claims

1. A light source, comprising:

an LED emitter having an angular range of emitted light θ

_s, where 0°

≦

θ

_s≦

90°

; and

an encapsulant that at least partially surrounds the LED emitter;

wherein the encapsulant includes an inner lens and an outer lens that are aligned along an optical axis, the inner lens having a refractive index n₁ and an outer convex surface, and the outer lens having a refractive index n₂>

n₁, and an inner concave surface that is in contact with the outer convex surface of the inner lens; and

wherein the inner lens produces a first virtual image of the LED emitter and the outer lens produces a second virtual image of the first virtual image, the first virtual image being disposed between the LED emitter and the second virtual image.

2. The light, source of claim 1, wherein the LED emitter emits wide-angle light from axial to grazing angles into the inner lens, and the inner lens converges and transmits such wide-angle light to the outer lens.

3. The light source of claim 2, wherein the emitted light emerges from the outer lens over a range of surface angles from 0 to θ

_2MAX, where θ

_2MAX is 45 degrees or less.

4. The light source of claim 1, wherein the second virtual image has a magnification relative to the LED emitter in a range from 3 to 4.

5. The light source of claim 1, wherein the LED emitter is substantially planar and has a maximum in-plane dimension of 2 h.

6. The light source of claim 5, wherein the outer lens has an outer curved surface of radius R₂, and wherein h/R₂ is no greater than 0.4.

7. The light source of claim 6, wherein h/R₂ is in a range from 0.3 to 0.4.

8. The light source of claim 1, wherein the outer lens has an outer curved surface that is substantially aplanatic with respect to the first virtual image.

9. The light source of claim 1, wherein the outer lens has an outer curved surface of radius R₂, the outer lens being exposed to a medium of refractive index n₀, and wherein the first virtual image is disposed at a distance Sag₂ from an apex of the outer curved surface of the outer lens, and wherein Sag₂ ≈

R₂*((n₀+n₂)/n₂).

10. The light source of claim 1, wherein n₁/n₂ is in a range from 0.7 to 0.8.

11. The light source of claim 10, wherein n₁ is about 1.5 and n₂ is about 2.

12. The light source of claim 1, wherein the inner lens is substantially plano-convex and the outer lens is substantially meniscus.

13. The light source of claim 1, further comprising a substrate on which the LED emitter is mounted, and wherein the inner lens adheres the outer lens to the substrate.

14. The light source of claim 1, wherein the outer lens has an outer curved surface and wherein the light source further comprises an anti-reflection coating on such outer curved surface of the outer lens.

15. The light source of claim 1, wherein the outer convex surface of the inner lens has a radius of curvature R₁ and has an apex disposed at a distance Sag₁ from the LED emitter, and where Sag₁ and R₁ are selected to substantially minimize the volume of the inner lens while encompassing the LED emitter and any wire bonds attached thereto.

16. lhe light source of claim 1 and further comprising:

a collimating lens that receives light from the outer lens; and

a polarizer that receives light from the collimating lens.

17. The light source of claim 16 wherein the collimating lens comprises a bulk lens.

18. The light source of claim 16 wherein the collimating lens comprises a Fresnel lens.

19. The light source of claim 16 wherein the polarizer comprises a reflecting polarizer.

20. The light source of claim 19 wherein the reflecting polarizer comprises at least one antireflective coating.

21. A light source, comprising:

an LED emitter having an angular range of emitted light θ

_s, where 0°

≦

θ

_s≦

90°

; and

an encapsulant that at least partially surrounds the LED emitter;

wherein the encapsulant includes an inner lens and an outer lens that are aligned along an optical axis, the inner lens having a refractive index n₁ and an outer convex surface, and the outer lens having a refractive index n₂>

n₁, and an inner concave surface that is in contact with the outer convex surface of the inner lens; and

wherein the inner lens is composed of a non-solid material and the outer lens is composed of a solid material.

22. The light source of claim 21, wherein the inner lens is composed of a light-transmissive liquid or gel.

23. The light source of claim 21, further comprising a substrate on which the LED emitter is mounted, and wherein the non-solid material is contained between the outer lens and the substrate.

24. A light source, comprising:

an LED emitter having angular range of emtitted light θ

_s, where 0°

≦

θ

_s≦

90°

; and

an encapsulant that at least partially surrounds the LED emitter;

wherein the encapsulant includes an inner lens and an outer lens that are aligned along an optical axis, the inner lens having a refractive index n₁ and an outer convex surface, and the outer lens having a refractive index n₂>

n₁, and an inner concave surface that substantially mates with the outer curved surface of the inner lens; and

wherein the emitted light exits the outer lens over a range of surface angles θ

₂ from 0 degrees to θ

_2MAX, where θ

_2MAX is no more than 45 degrees.

25. The light source of claim 24, wherein θ

_2MAX is no more than 30 degrees.