LIGHT EMITTING DIODE-BASED LAMP HAVING A VOLUME SCATTERING ELEMENT

• US 20100097821A1
• Filed: 01/09/2009
• Published: 04/22/2010
• Est. Priority Date: 10/16/2008
• Status: Abandoned Application

• Current Assignee: OSRAM Sylvania Inc. (Ams-Osram AG)
• Original Assignee: OSRAM Sylvania Inc. (Ams-Osram AG)
• Inventors: Spehalski, Tom, Huang, Michelle, Ulloa, Fernando, Lee, Junwon
• Application Number:
  US12/351,197
• Publication Number:
  US 20100097821A1
• Time in Patent Office: Days
• US Class Current: 362/555
• CPC Class Codes: F21K 9/61 using light guides
• CPC Class Codes: F21K 9/64 using wavelength conversion means distinct or spaced from the light-generating element, e.g. a remote phosphor layer
• CPC Class Codes: F21S 8/065 multi-branched, e.g. a chandelier
• CPC Class Codes: F21V 29/74 with fins or blades
• CPC Class Codes: F21V 3/02 characterised by the shape
• CPC Class Codes: F21W 2121/00 Use or application of lighting devices or systems for decorative purposes, not provided for in codes F21W2102/00 – F21W2107/00
• CPC Class Codes: F21Y 2115/10 Light-emitting diodes [LED]

Abstract

A lamp having a candle-like appearance and using one or more light-emitting diodes (LEDs) as its light source is presented. The candle-like appearance arises because light is emitted from only a small volume at or near the center of the bulb. The heat sink and control electronics are located outside the bulb of the lamp. Inside the bulb is a set of secondary optics that guide the light from one or more LEDs to an emission point at a prescribed location in the interior of the bulb. The secondary optics include a light pipe that guides light away from the LED chip, and a volume scattering element that receives the light from the light pipe and scatters it into various directions. The volume scattering element is made from a transparent base material, and includes transparent particles of a predetermined size and refractive index. Because the lamp is typically used in an overhead position, such as in a hanging chandelier, the density of particles in the volume scattering element, the particle size and the particle refractive index are chosen to produce a scattering pattern that directs more light downward (toward the base of the bulb) than upward, while maintaining a reasonable efficiency (fraction of produced light that successfully exits the lamp). Simulation results are presented.

Claims

1. A lamp (10), comprising:

a transparent bulb (20) enclosing a volume and having an opening at a longitudinal end;

a light emitting diode (50) disposed proximate the opening in the transparent bulb (20) for emitting light into the transparent bulb (20);

a transparent light pipe (31) disposed inside the transparent bulb (20) proximate the opening in the transparent bulb (20) for receiving light from the light emitting diode (50), the light entering a proximal end of the light pipe (31) and propagating longitudinally away from the proximal end to a distal end of the light pipe (31); and

a volume scattering element (32) disposed inside the transparent bulb (20) adjacent to the distal end of the light pipe (31) for receiving light from the transparent light pipe (31) and for scattering light into a plurality of exiting angles;

wherein the scattered light exits the lamp (10) through the transparent bulb (20); and

wherein the volume scattering element (32) comprises a transparent base material (33) and a plurality of particles (34) distributed throughout the base material (33), each particle (34) in the plurality being transparent and having a refractive index different than that of the base material (33).

2. The lamp (10) of claim 1, wherein the volume scattering element (32) is a sphere.

3. The lamp (10) of claim 1, wherein the light propagates longitudinally in the light pipe (31) by transmission and by total internal reflection off a lateral edge of the light pipe (31).

4. The lamp (10) of claim 1, wherein the light pipe (31) is longitudinally separated from the light emitting diode (50).

5. The lamp (10) of claim 4, further comprising a reflective element (41) directly longitudinally adjacent to the proximal end of the light pipe (31) for collecting high-angle light from the light emitting diode (50) and reflecting the high-angle light into the proximal end of the light pipe (31).

6. The lamp (10) of claim 1, wherein the particles (34) in the volume scattering element (32) have a size distribution and a refractive index distribution that determine the amount of light scattered in each direction.

7. The lamp (10) of claim 6, wherein each particle (34) in the plurality in the volume scattering element (32) has generally the same size and generally the same refractive index.

8. The lamp (10) of claim 7, wherein the particles (34) in the volume scattering element (32) scatter more light in the proximal direction than in the distal direction.

9. The lamp (10) of claim 1, wherein the light pipe (31) and the base material (33) of the volume scattering element (32) have the same refractive index.

10. The lamp (10) of claim 1, wherein the light pipe (31) and the base material (33) of the volume scattering element (32) are made from polymethyl methacrylate (PMMA) and have a refractive index of about 1.49 at a wavelength of 550 nm.

11. The lamp (10) of claim 1, wherein the particles (34) in the volume scattering element (32) have a refractive index in the range of about 1.51 to about 1.59 at a wavelength of 550 nm.

12. The lamp (10) of claim 1, wherein the particles (34) in the volume scattering element (32) are generally round and have nominal diameters in the range of about 1 micron to about 10 microns.

13. The lamp (10) of claim 1, wherein the particles (34) in the volume scattering element (32) have nominal diameters in the range of about 3 microns to about 6 microns, have refractive indices of about 1.56 at a wavelength of 550 nm, and have a particle density in the range of about 1.5 million particles per cubic millimeter to about 2.0 million particles per cubic millimeter.

14. The lamp (10) of claim 1, wherein the light pipe (31A, 31B) has a cross-section, taken in a slice that includes a longitudinal axis of the light pipe (31A, 31B), that has straight sides.

15. The lamp (10) of claim 1, wherein the light pipe (31C) has a cross-section, taken in a slice that includes a longitudinal axis of the light pipe (31C), that has tapered sides.

16. The lamp (10) of claim 1, wherein the light pipe (31B, 31C) has cross-sections, taken in slices that are perpendicular to a longitudinal axis of the light pipe (31B, 31C), that are circular all along the longitudinal extent of the light pipe (31B, 31C), the circles decreasing in diameter from the proximal to the distal end of the light pipe (31B, 31C).

17. The lamp (10) of claim 1, wherein the volume scattering element (32) has a diameter roughly 1.5 to 2.5 times as large as a cross-sectional diameter of the light pipe (31).

18. The lamp (10) of claim 1, further comprising:

a light emitting diode driver (80) for supplying electrical power to the light emitting diode (50); and

a heat sink (60) for dissipating heat generated by the light emitting diode (50);

wherein the light emitting diode driver (80) and the heat sink (60) are disposed outside the transparent bulb (20).

19. The lamp (10) of claim 18,

wherein the light emitting diode driver (80) is disposed within a housing that resembles a candlestick;

and

wherein the heat sink resembles candle wax drippings on an exterior of the housing.

20. The lamp (10) of claim 1, wherein the volume scattering element (32) and the light pipe (31) are integral.

21. The lamp (10) of claim 1, wherein the volume scattering element (32) and the light pipe (31) are attached by optical contacting.

22. The lamp (10) of claim 1, wherein the volume scattering element (32) and the light pipe (31) are attached by adhesive.

23. A method of providing light, comprising:

locating a light emitting diode (50) proximate an opening in a transparent bulb (20);

electrically powering the light emitting diode (50) with a driver (80) disposed outside the transparent bulb (20);

dissipating heat generated by the light emitting diode (50) with a heat sink (60) disposed outside the transparent bulb (20);

collecting light emitted by the light emitting diode (50) with a proximal end of a light pipe (31) disposed inside the transparent bulb (20);

transmitting the collected light to a distal end of the light pipe (31) by transmission through the light pipe (31) and by total internal reflection from a lateral edge of the light pipe (31);

receiving the light from the distal end of the light pipe (31) at a volume scattering element (32), the volume scattering element (32) comprising a transparent base material (33) and a plurality of particles (34) distributed throughout the base material (33), each particle (34) in the plurality being transparent and having a refractive index different from that of the base material (33); and

scattering the received light into a plurality of directions with the volume scattering element (32).

24. The method of claim 23, wherein more light is scattered in the proximal direction than in the distal direction.

25. A lamp (10), comprising:

a transparent bulb (20) having an opening;

a light emitting diode (50) disposed proximate the opening in the transparent bulb (20) for emitting light into the transparent bulb (20);

a heat sink (60) proximate the light emitting diode (50) and in thermal contact with the light emitting diode (50), the heat sink (60) comprising a distal edge facing the light emitting diode (50) and a lateral edge extending longitudinally proximally away from the distal edge around a circumference of the lamp (10), the lateral edge and distal edge forming an interior of the heat sink (60);

a light emitting diode driver (80) disposed within the interior of the heat sink (60) for supplying electrical power to the light emitting diode (50); and

an electrically conductive base (100) extending proximally from the lamp (10) for receiving electrical power from a socket and supplying electrical power to the light emitting diode driver (80), the base (100) being thermally insulated from the heat sink (60).

26. The lamp (10) of claim 25, further comprising:

a driver insulator (70) surrounding the light emitting diode driver (80) on its distal and transverse sides and being surrounded by the heat sink (60) on its distal and transverse sides; and

a base insulator (90) proximate a proximal side of the light emitting diode driver (80);

wherein the base insulator (90) thermally insulates the base (100) from both the heat sink (60) and the light emitting diode driver (80).

27. The lamp (10) of claim 26,

wherein the heat sink (60) radially surrounds a portion of a telescoping extension tube (110);

and

wherein the telescoping extension tube (110) radially surrounds a portion of the driver insulator (70).

28. The lamp (10) of claim 25, wherein the heat sink (60) forms an exterior shell around the transverse circumference of the lamp (10) between the bulb (20) and the base (100).

29. The lamp (10) of claim 25, wherein the heat sink (60) has an appearance that resembles dripping candle wax.