Optical device for LED-based light-bulb substitute

• US 20040228131A1
• Filed: 06/12/2003
• Published: 11/18/2004
• Est. Priority Date: 05/13/2003
• Status: Active Grant

• Current Assignee: Light Engine Limited
• Original Assignee: Light Prescriptions Innovators LLC A Delaware Limited Liability Company
• Inventors: Falicoff, Waqidi, Parkyn, William A., Benitez, Pablo, Minano, Juan C.
• Granted Patent: US 7,021,797 B2
• Time in Patent Office: Days
• US Class Current: 362/307
• CPC Class Codes: F21K 9/232 specially adapted for generating an essentially omnidirectional light distribution, e.g. with a glass bulb
• CPC Class Codes: F21K 9/233 specially adapted for generating a spot light distribution, e.g. for substitution of reflector lamps
• CPC Class Codes: F21K 9/61 using light guides
• 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 19/0066 in the form of an LED array
• CPC Class Codes: G02B 19/0071 adapted to illuminate a complete hemisphere or a plane extending 360 degrees around the source
• CPC Class Codes: H01L 33/54 having a particular shape

Abstract

An optical device for coupling the luminous output of a light-emitting diode (LED) to a predominantly spherical pattern comprises a transfer section that receives the LED'"'"'s light within it and an ejector atop it that receives light from the transfer section and spreads it spherically. The base of the transfer section is optically coupled to the LED so that the LED'"'"'s light goes inside the transfer section, which comprises a compound elliptic concentrator operating via total internal reflection. The ejector section can have a variety of shapes, and can have diffusive features on its surface as well. The device is circularly symmetric, with a height preferably only a few times its diameter. An important application is for use at the focus of the parabolic reflectors in flashlights. This version of the invention further comprises a base-can identical in outer shape and electric contacts to those of flashlight bulbs. Within the can is the current-control circuitry the interfaces the LED with battery voltage. Another version uses half a transfer section at each end of a long cylindrical ejector, illuminated by an LED at both ends. Ejection is via internal scattering by controlled sub-wavelength roughness. In one cylindrical embodiment, diffuse reflectivity varies from one third at the ends to two thirds at center.

Claims

1. An optical device for distributing the radiant emission of a light emitter comprising:

a lower transfer section; and

an upper ejector section situated upon the lower transfer section, said lower transfer section operable for placement upon the light emitter and operable to transfer the radiant emission to said upper ejector section, said upper ejector section shaped such that the emission is redistributed externally into a substantial solid angle.

2. The device of claim 1 wherein the lower transfer section is a solid of revolution having a profile in the shape of an ellipse with a long axis parallel to an axis of revolution of the solid and displaced laterally therefrom so as to place a focus of said elliptical profile on an opposite side of said axis.

3. The device of claim 2 wherein the upper ejector section is a cylinder of the same diameter as a top diameter of the transfer section, said cylinder having a conical depression on a top surface of the cylinder.

4. The device of claim 2 wherein said lateral displacement substantially equals a radius of said ellipsoid at a focus of said ellipsoid.

5. The device of claim 4 wherein said upper ejector section is conicoid.

6. The device of claim 1 wherein said upper ejector section is spherical.

7. The device of claim 1 wherein said upper ejector section is an indented section of a sphere.

8. The device of claim 1 wherein said upper ejector section is a cylinder.

9. The optical device of claim 1 further comprising a light emitting diode (LED) optically coupled to said lower transfer section via immersion in a solid transparent dielectric having an external shape forming an upper portion of said lower transfer section and forming said upper ejector section and wherein a reflector cup immersed in said dielectric surrounding said LED forms a lower section of said lower transfer section, said external shape of said dielectric having a positive mold release.

10. The device of claim 1 further comprising:

a light emitter optically coupled to said lower transfer section; and

a base can mounted below said light emitter, said base can containing power and control electronic means for said light emitter, said can having an electrically conductive side and an electrically separate end-means of opposite electrical polarity from said conductive side, said can having thermally conductive paths for heat generated by said light emitter.

11. The device of claim 10 further comprising a transparent enclosure atop of said base can, said enclosure surrounding said upper and lower transfer sections and said light emitter.

12. The device of claim 11 further comprising a parabolic reflector surrounding said transparent enclosure and having a focus on said upper ejector section.

13. The device of claim 12 wherein the upper ejector section has a diffusive surface.

14. An optical device for distributing the radiant emission of a light emitter, comprising multiple off-axis ellipsoids made of substantially transparent material, said ellipsoids truncated at a focal point of each ellipsoid, said ellipsoids coupled longitudinally to each other to provide a totally internally reflecting channel.

15. The device of claim 14 having a surface with graded sub-wavelength roughness operable for reflective scattering of said emitted light out of said device.

16. An optical device for distributing radiant emission of a light emitter, comprising:

an expander section made of substantially transparent material operable for receiving said radiant emission and widening said radiant emission while narrowing an angular range of said radiant emission at least down to that of cylindrical light-guiding via total internal reflection; and

a cylindrical ejector section coupled to said expander section and made of substantially transparent material operable for receiving and ejecting said angularly narrowed radiation via graded sub-wavelength surface roughness of the cylindrical ejector section.

17. The optical device of claim 16 further comprising a planar mirror extending across a distal end of said ejector section.

18. The optical device of claim 16 further comprising at the distal end of said ejector section a second expander section and light emitter optically coupled to said distal end of said ejector section.

19. The device of claim 18 wherein said sub-wavelength roughness is highest on a perimeter of said ejector section at equal distance from both said expander sections, and lowest in proximity to said expander sections.

20. A method calculating proper distribution of sub-wavelength roughness of an optical device comprising the steps of:

measuring of external brightness of a uniform distribution of sub-wavelength roughness on a first sample device;

adjusting said roughness distribution on a second sample device with roughness increases in low-luminance zones and roughness decreases in high-luminance zones; and

continuing said adjustments in subsequent samples until proper roughness distribution is achieved for subsequent mass production.

21. A method of calculating proper distribution of sub-wavelength roughness of an optical device comprising the steps of:

calculatingexternal brightness of a uniform distribution of sub-wavelength roughness at each position along a cylindrical ejector of the optical device in accordance with a local specular view factor of an expander section of the optical device so as to achieve a desired external luminance distribution along said cylindrical ejector; and

calculating said external luminance of an out-refracted portion of said local specular view factor by luminance-weighted reverse ray-tracing through multiple internal reflections back through said cylindrical ejector, said internal reflections with specular reflectivity reduced from total in accordance with non-specular scattering induced by a local value of said sub-wavelength roughness.