Polarized LED

• US 20060091412A1
• Filed: 10/29/2004
• Published: 05/04/2006
• Est. Priority Date: 10/29/2004
• Status: Abandoned Application

• Current Assignee: 3M Innovative Properties Company (3M Company)
• Original Assignee: 3M Innovative Properties Company (3M Company)
• Inventors: Wheatley, John A., Ouderkirk, Andrew J., Leatherdale, Catherine A.
• Application Number:
  US10/977,582
• Publication Number:
  US 20060091412A1
• Time in Patent Office: Days
• US Class Current: 257/98
• CPC Class Codes: H01L 2924/00 Indexing scheme for arrangements or methods for connecting or disconnecting semiconductor or solid-state bodies as covered by H01L24/00
• CPC Class Codes: H01L 2924/0002 Not covered by any one of groups H01L24/00, H01L24/00 and H01L2224/00
• CPC Class Codes: H01L 33/44 characterised by the coatings, e.g. passivation layer or anti-reflective coating
• CPC Class Codes: H01L 33/54 having a particular shape

Abstract

A solid state light source includes an LED die that generates light of two polarization states. A medium is provided at or near an emitting surface of the LED die that preferentially reflects one polarization state back into the LED die and preferentially transmits the other polarization state out of the LED die, thus providing a solid state light source whose light output is at least partially polarized. Recycling of light within the LED die together with polarization conversion mechanisms can enhance efficiency and brightness of the polarized output.

Claims

1. A light source, comprising:

an LED die that generates light of a first and second polarization state, the die having an emitting surface; and

a birefringent material coupled to the LED die such that light of the first polarization state is preferentially coupled out of the emitting surface.

2. The light source of claim 1, wherein the birefringent material has an input surface in optical contact with the emitting surface of the LED die.

3. The light source of claim 1, wherein the birefringent material has a refractive index mismatch for the first and second polarization states of at least about 0.05.

5. The light source of either claim 1 or 4, further comprising a polarization converting layer coupled to the LED die.

6. The light source of claim 5, wherein the polarization converting layer comprises a wave plate.

7. The light source of claim 5, wherein the polarization converting layer comprises a scattering surface.

4. A light source, comprising:

an LED die that generates light of a first and second polarization state, the die having an emitting surface; and

reflecting means coupled to the LED die for preferentially reflecting the second polarization state back into the LED die.

8. The light source of claim 4, wherein the reflecting means comprises a body of birefringent material proximate the emitting surface.

9. The light source of claim 8, wherein the body has an input surface proximate the emitting surface, and further has an output surface and at least one reflective side surface between the input and output surfaces.

10. The light source of claim 8, wherein the birefringent material comprises calcite.

11. The light source of claim 4, wherein the reflecting means comprises a reflective polarizer proximate the emitting surface.

12. The light source of claim 11, wherein the reflective polarizer comprises a wire grid.

13. The light source of claim 11, wherein the reflective polarizer comprises a multilayer optical film.

14. The light source of claim 11, wherein the reflective polarizer comprises cholesteric material.