Separate optical device for directing light from an LED

• US 20070152230A1
• Filed: 01/03/2007
• Published: 07/05/2007
• Est. Priority Date: 01/05/2006
• Status: Active Grant

• Current Assignee: illumitex, Inc.
• Original Assignee: illumitex, Inc.
• Inventors: Thomas, Matthew, Winberg, Paul, Duong, Dung
• Granted Patent: US 7,772,604 B2
• Time in Patent Office: Days
• US Class Current: 257/98
• CPC Class Codes: F21V 7/09 with a combination of different curvatures
• CPC Class Codes: G02B 19/0028 refractive and reflective surfaces, e.g. non-imaging catadioptric systems
• CPC Class Codes: G02B 19/0061 the light source comprising a LED semiconductor devices with at least one potential-jump barrier or surface barrier specially adapted for light emission H01L33/00
• CPC Class Codes: H01L 27/14618 Containers
• CPC Class Codes: H01L 27/14627 Microlenses
• CPC Class Codes: H01L 27/14629 Reflectors
• CPC Class Codes: H01L 33/58 Optical field-shaping elements
• CPC Class Codes: H01L 33/60 Reflective elements

Abstract

Embodiments of the present invention provide separate optical devices operable to couple to a separate LED, the separate optical device comprising an entrance surface to receive light from a separate LED when the separate optical device is coupled to the separate LED, an exit surface opposite from and a distance from the entrance surface and a set of sidewalls. The exit surface has at least a minimum area necessary to conserve brightness for a desired half-angle of light projected from the separate optical device. Furthermore, each sidewall is positioned and shaped so that at least a majority of rays having a straight transmission path from the entrance surface to that sidewall reflect to the exit surface with an angle of incidence at the exit surface at less than or equal to a critical angle at the exit surface.

Claims

1. A separate optical device operable to couple to a separate LED, the separate optical device comprising:

an entrance surface to receive light from a separate LED when the separate optical device is coupled to the separate LED;

an exit surface opposite from and a distance from the entrance surface, wherein the exit surface has at least a minimum area necessary to conserve radiance for a desired half-angle of light projected from the separate optical device;

a set of sidewalls, wherein each sidewall is positioned and shaped so that at least a majority of rays having a straight transmission path from the entrance surface to that sidewall reflect to the exit surface with an angle of incidence at the exit surface at less than or equal to a critical angle at the exit surface.

2. The separate optical device of claim 1, wherein the exit surface has the minimum area necessary to conserve brightness for the desired half-angle of light emitted from the separate optical device.

3. The separate optical device of claim 1, wherein the exit surface has an area that is at least equal to a minimum area equal to Φ

₂n₁²A₁Ω

₁/Φ

₁n₂²Ω

₂ wherein Φ

₁ is the light flux entering the entrance surface, Φ

₂ is the light flux exiting exit surface,

Ω

₁ is the effective solid angle whereby light enters the entrance surface, Ω

₂ is the effective solid angle whereby light leaves exit surface;

A₁ is the area of the entrance surface, n₁ is the refractive index of material of the separate optical device and n₂ is the refractive index of the substance external to the separate optical device.

4. The separate optical device of claim 3, wherein the LED has a square shape and wherein the effective solid angle whereby light leaves the exit surface is determined to account for the square shape of the LED.

5. The separate optical device of claim 1 wherein the distance is within 50% of a minimum distance so that all rays with a straight transmission path from the entrance surface to the exit surface have an angle of incidence that is less than or equal to the critical angle at the exit surface and wherein the area of the exit surface is within 50% of a minimum area defined by Φ

₂n₁²A₁Ω

<sub>1/Φ

1</sub>n₂²Ω

₂ wherein Φ

₁ is the light flux entering the entrance surface, Φ

₂ is the light flux exiting exit surface,

Ω

₁ is the effective solid angle whereby light enters the entrance surface, Ω

₂ is the effective solid angle whereby light leaves exit surface;

A₁ is the area of the entrance surface, n₁ is the refractive index of material of the separate optical device and n₂ is the refractive index of the substance external to the separate optical device.

6. The separate optical device of claim 1, wherein each sidewall is positioned and shaped so that at least 80% of rays with a straight transmission path from the entrance surface to the sidewall are reflected to the exit surface with an angle of incidence on the exit surface at less than or equal to the critical angle at the exit surface.

7. The separate optical device of claim 6, wherein the at least 80% of rays reflected are reflected through total internal reflection.

8. The separate optical device of claim 6, further comprising a reflective layer and wherein each sidewall is shaped so that the at least 80% of rays are reflected by the reflective layer to the exit surface with an angle of incidence on the exit surface at less than or equal to the critical angle at the exit surface.

9. The separate optical device of claim 1, wherein the shapes of the sidewall are selected to create a desired intensity profile.

10. The separate optical device of claim 8, wherein the desired intensity profile is an approximately uniform intensity profile.

11. The separate optical device of claim 1, wherein the separate optical device is formed of a single piece of solid material.

12. The separate optical device of claim 11, wherein the separate optical device has an index of refraction within 20% of the index of refraction of a substrate of the LED.

13. The separate optical device of claim 1, wherein the entrance surface and exit surface have the same shape and aspect ratio as the LED.

14. The separate optical device of claim 1, wherein the exit surface is parallel to and rotationally aligned with the entrance surface.

15. The separate optical device of claim 1, wherein the entrance surface is square.

16. The separate optical device of claim 1, wherein the separate optical device is configured to output a substantially square and uniform beam of light.

17. The separate optical device of claim 1, wherein the separate optical device is configured to direct light from the LED into a smaller solid angle while conserving radiance.

18. The separate optical device of claim 17, wherein the separate optical device is configured to provide a maximum radiant intensity.

19. The separate optical device of claim 1, wherein the separate optical device defines a set of additional entrance surfaces that at least partially define a cavity into which the LED at least partially fits.

20. A separate optical device operable to couple to a separate LED, the separate optical device comprising:

an entrance surface to receive light from a layer of a separate LED when the separate optical device is coupled to the separate LED;

an exit surface opposite from and a distance from the entrance surface, wherein the exit surface has at least a minimum area necessary to conserve radiance for a desired half-angle of light projected from the separate optical device;

a set of sidewalls, wherein each sidewall is positioned and shaped so that at least a portion of rays having a straight transmission path from the entrance surface to that sidewall reflect to the exit surface with an angle of incidence at the exit surface at less than or equal to a critical angle at the exit surface, wherein each sidewall shape represents a superposition of multiple contoured surfaces;

wherein the area of the exit surface, distance and sidewall shapes are selected to project light with a half angle of between 10 to 60 degrees with at least 70% efficiency and a desired intensity profile.

21. The separate optical device of claim 20, wherein the area of the exit surface, distance and sidewall shapes are selected to project light with a half angle of between 10 to 60 degrees with at least 90% efficiency

22. The separate optical device of claim 20, wherein the exit surface has an area that is at least equal to a minimum area equal to Φ

₂n₁²A₁Ω

₁/Φ

₁n₂²Ω

₂ wherein Φ

₂ is the light flux entering the entrance surface, Φ

₂ is the light flux exiting exit surface,

Ω

₁ is the effective solid angle whereby light enters the entrance surface, Ω

2 is the effective solid angle whereby light leaves exit surface;

A₁ is the area of the entrance surface, n₁ is the refractive index of material of the separate optical device and n₂ is the refractive index of the substance external to the separate optical device.

23. The separate optical device of claim 22, wherein the LED has a square shape and wherein the effective solid angle whereby light leaves the exit surface is determined to account for the square shape of the LED.

24. The separate optical device of claim 20, wherein the distance is within 50% of a minimum distance so that all rays with a straight transmission path from the entrance surface to the exit surface have an angle of incidence that is less than or equal to the critical angle at the exit surface and wherein the area of the exit surface is within 50% of a minimum area defined by Φ

₂n₁²A₁Ω

₁/Φ

₁n₂²Ω

₂ wherein Φ

₂ is the light flux entering the entrance surface, Φ

₂ is the light flux exiting exit surface,

Ω

₁ is the effective solid angle whereby light enters the entrance surface, Ω

₂ is the effective solid angle whereby light leaves exit surface;

A₁ is the area of the entrance surface, n₁ is the refractive index of material of the separate optical device and n₂ is the refractive index of the substance external to the separate optical device.

25. The separate optical device of claim 20, wherein each sidewall is positioned and shaped so that at least 80% of rays with a straight transmission path from the entrance surface to the sidewall are reflected to the exit surface with an angle of incidence on the exit surface at less than or equal to the critical angle at the exit surface.

26. The separate optical device of claim 20, further comprising a reflective layer and wherein each sidewall is shaped so that the at least 80% of rays are reflected by the reflective layer to the exit surface with an angle of incidence on the exit surface at less than or equal to the critical angle at the exit surface.

27. The separate optical device of claim 20, wherein the separate optical device is formed of a single piece of solid material.

28. The separate optical device of claim 27, wherein the separate optical device has an index of refraction within 20% of the index of refraction of the layer of the LED.

29. The separate optical device of claim 20, wherein the entrance surface and exit surface have the same shape and aspect ratio as the LED.

30. The separate optical device of claim 20, wherein the exit surface is parallel to and rotationally aligned with the entrance surface.

31. The separate optical device of claim 20, wherein the entrance surface is square.

32. The separate optical device of claim 20, wherein the separate optical device defines a set of additional entrance surfaces that at least partially define a cavity into which the LED at least partially fits.

33. A separate optical device configured to couple to a separate LED, the separate optical device comprising:

an entrance surface to receive light from a layer of a separate LED when the separate optical device is coupled to the separate LED;

an exit surface opposite from and a distance from the entrance surface;

wherein the exit surface has an area at least equal to a minimum area defined by Φ

₂n₁²A₁Ω

₁/Φ

₁n₂²Ω

₂ wherein Φ

₁ is the light flux entering the entrance surface, Φ

₂ is the light flux exiting exit surface,

Ω

₁ is the effective solid angle whereby light enters the entrance surface, Ω

₂ is the effective solid angle whereby light leaves exit surface;

A₁ is the area of the entrance surface, n₁ is the refractive index of material of the separate optical device and n₂ is the refractive index of the substance external to the separate optical device. wherein the distance is selected to be at least a minimum distance so that all rays with a straight transmission path from the entrance surface to the exit surface have an angle of incidence that is less than or equal to a critical angle at the exit surface;

a set of sidewalls, wherein each sidewall is positioned and shaped so that at least a portion of rays having a straight transmission path from the entrance surface to that sidewall reflect to the exit surface with an angle of incidence at the exit surface at less than or equal to the critical angle at the exit surface, wherein each sidewall shape represents a superposition of multiple contoured surfaces;

wherein the area of the exit surface, distance and sidewall shapes are selected to project light with a half angle of between 10 to 60 degrees with at least 60% efficiency and a desired intensity profile.

34. The separate optical device of claim 33, wherein the area of the exit surface, distance and sidewall shapes are selected to project light with a half angle of between 10 to 60 degrees with at least 90% efficiency.

35. The separate optical device of claim 33, wherein the area of the exit surface is within 5% of the minimum area;

and the distance is within 5% of the minimum distance.

36. The separate optical device of claim 33, wherein the LED has a square shape and wherein the effective solid angle whereby light leaves the exit surface is determined to account for the square shape of the LED.