LED luminance-augmentation via specular retroreflection, including collimators that escape the etendue limit

• US 20080291682A1
• Filed: 05/21/2008
• Published: 11/27/2008
• Est. Priority Date: 05/21/2007
• Status: Active Grant

• Current Assignee: Light Engine Limited
• Original Assignee: Light Prescriptions Innovators, LLC
• Inventors: Chaves, Julio C., Falicoff, Waqidi, Benitez, Pablo, Minano, Juan Carlos, Parkyn, William A. JR.
• Granted Patent: US 7,874,704 B2
• Time in Patent Office: Days
• US Class Current: 362/310
• CPC Class Codes: F21V 13/04 the elements being reflectors and refractors for vehicle rear lights F21S43/40
• CPC Class Codes: F21V 5/04 of lens shape
• CPC Class Codes: F21V 7/0091 using total internal reflection
• CPC Class Codes: F21Y 2115/10 Light-emitting diodes [LED]
• 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: G02B 27/30 Collimators
• CPC Class Codes: G02B 3/08 with discontinuous faces, e.g. Fresnel lens diffractive Fresnel lenses G02B5/1876
• CPC Class Codes: G02B 5/12 Reflex reflectors
• CPC Class Codes: G02B 5/126 including curved refracting surface
• CPC Class Codes: H01L 33/58 Optical field-shaping elements

Abstract

The diffuse reflectivity of an LED source is utilized to recycle some of its emission, thereby enabling a luminaire to escape the étendue limit. Retroreflectors intercept the rays destined for the outer part of the luminaire aperture, which can then be truncated. The resulting smaller aperture has the same beam-width as the full original, albeit with lesser flux due to recycling losses. A reduction to half the original area is possible.

Claims

1. A collimating luminaire comprising a light-source with a diffuse reflectivity exceeding one half, a collimating luminaire intercepting the emitted light of said source, said luminaire producing a substantially uniform beamwidth across its exit aperture, and a system of retroreflectors that returns part of said emitted light to said source, said retroreflectors allowing the removal of the outer part of said exit aperture, so that said exit aperture is smaller than the é

tendue-limited aperture for said beamwidth.

14. The collimating luminaire of claim 1 wherein said retroreflectors operate in air.

15. The collimating luminaire of claim 1 wherein said retroreflectors operate inside a dielectric.

16. The collimating luminaire of claim 15 wherein said retroreflectors reflect via means of micro-linear grooves.

17. The collimating luminaire of claim 15 wherein said retroreflectors reflect via means of a thin film stack.

18. The collimating luminaire of claim 17 wherein said thin film stack has an initial layer of a low index of refraction material with a thickness approximately equal to two times the nominal wavelength for stack.

2. A collimating luminaire comprising a light-source with a diffuse reflectivity exceeding one half, said luminaire defining an exit aperture and intercepting the emitted light of said source in directions outside the exit aperture, said luminaire comprising at least one at least approximately elliptically concave retroreflector that returns part of said emitted light to said source.

3. A collimating luminaire according to claim 2, wherein at least one focus of an ellipse defining the elliptically concave retroreflector is at least approximately at an edge of a beam of light that reaches the retroreflector from the source.

4. A collimating luminaire according to claim 3, wherein at least one focus of the ellipse is at least approximately at an edge of the light source.

5. A collimating luminaire according to claim 3, wherein at least one focus of the ellipse is at least approximately at an edge of an opaque object that cuts off the beam of light.

6. A collimating luminaire according to claim 5, which comprises at least two said retroreflectors, and wherein at least one focus of the ellipse defining a first retroreflector is at least approximately at an edge of a second retroreflector between the source and the first retroreflector.

7. A collimating luminaire according to claim 2, further comprising at least one forward reflector positioned to direct intercepted light through the exit aperture in such a manner as to produce a substantially uniform beamwidth across the exit aperture wherein the exit aperture is smaller than the é

tendue-limited aperture for said beamwidth.

8. A collimating luminaire according to claim 7, wherein at least one said forward reflector is at least approximately hyperbolically concave.

9. A collimating luminaire according to claim 8, wherein at least one focus of a hyperbola defining the hyperbolically concave forward reflector is at least approximately at an edge of a beam of light that reaches the forward reflector from the source.

10. A collimating luminaire according to claim 9, wherein at least one focus of the hyperbola is at least approximately at an edge of the light source.

11. A collimating luminaire according to claim 9, wherein at least one focus of the hyperbola is at least approximately at an edge of at an edge of an opaque object that cuts off the beam of light.

12. A collimating luminaire according to claim 11, wherein at least one focus of the hyperbola is at least approximately at an edge of a said retroreflector between the source and the forward reflector.

13. A collimating luminaire comprising a light-source with a diffuse reflectivity exceeding one half, a collimating luminaire intercepting the emitted light of said source, said luminaire producing a substantially uniform beamwidth across its exit aperture, and a system of forward reflectors that directs part of said emitted light to said exit aperture, said system of reflectors allowing the removal of the outer part of said exit aperture, so that said exit aperture is smaller than the é

tendue-limited aperture for said beamwidth.