Color tunable light source

• US 6,357,889 B1
• Filed: 12/01/1999
• Issued: 03/19/2002
• Est. Priority Date: 12/01/1999
• Status: Expired due to Term

• Current Assignee: Savant Technologies, LLC (Savant Systems, LLC)
• Original Assignee: General Electric Company
• Inventors: Srivastava, Alok M., Levinson, Lionel M., Duggal, Anil R., Duclos, Steven J.
• Primary Examiner(s): Husar, Stephen
• Assistant Examiner(s): Ton, Anabel
• Application Number:
  US09/452,554
• Time in Patent Office: 839 Days
• Field of Search: 362/230, 362/231, 362/84, 362/260, 362/293, 362/235, 362/800, 362/249, 405/42, 405/43, 313/483, 313/485, 313/486, 313/113, 313/512
• US Class Current: 362/84
• 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: F21V 3/061 the material being glass
• CPC Class Codes: F21V 3/062 the material being plastics
• CPC Class Codes: F21V 3/12 the coatings comprising photoluminescent substances
• CPC Class Codes: F21V 7/24 characterised by the material
• CPC Class Codes: F21Y 2113/13 comprising an assembly of point-like light sources
• CPC Class Codes: F21Y 2113/17 forming a single encapsulated light source
• CPC Class Codes: F21Y 2115/10 Light-emitting diodes [LED]
• CPC Class Codes: F21Y 2115/30 Semiconductor lasers
• CPC Class Codes: H01L 25/0753 the devices being arranged next to each other
• 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: H05B 45/20 Controlling the colour of the light
• CPC Class Codes: H05B 45/24 using electrical feedback from LEDs or from LED modules

Abstract

A color tunable light source (10) includes multiple light emitting components (32, 34, 36), such as light emitting diodes (LEDs) or laser diodes (LDs) with different emission wavelengths, and multiple phosphors (24) with different excitation and emission wavelengths. The emission wavelengths of the different light emitting components are chosen to match the excitation wavelengths of the different phosphors. The light emitting components are powered by an electrical circuit (42, 44, 46), which allows separate control of the optical power output of the different wavelength LEDs/LDs. The light from the light emitting components is arranged to impinge on the combination of phosphors such that the phosphors are excited and emit light at their characteristic wavelengths. By separately adjusting the power to each LED/LD, the amount of light emitted by each phosphor, and hence, through color mixing, the color of the light emitted, is varied.

Claims

1. A light source comprising:

a first light emitting component which emits light at a first wavelength;

a second light emitting component which emits light at a second wavelength different from that of the first wavelength; and

phosphors positioned to receive the light emitted by the first and second light emitting components, the phosphors including;

a first phosphor which absorbs a part of the light from the first light emitting component and emits light of a third wavelength, and

a second phosphor which absorbs a part of the light from the second light emitting component and emits light of a fourth wavelength, the second phosphor being excited relatively less by light of the first wavelength than by light of the second wavelength, such that when power supplied to at least one of the first and second light emitting components is varied, the color of light emitted by the light source is changed.

2. The light source of claim 1, wherein the first and second light emitting components are selected from the group consisting of light emitting diodes and laser diodes.

3. The light source of claim 1, wherein each of the first and second light emitting components includes a plurality of light emitting diodes.

4. The light source of claim 1, further including:

a controller for variably controlling power supplied to at least one of the first and second light emitting components separately from the other of the first and second light emitting components for varying the color of light emitted by the light source.

5. The light source of claim 4, wherein the power to both the first and the second light emitting components is separately variable.

6. The light source of claim 1, wherein the first phosphor is excited by light emitted by both the first and second light emitting components.

7. The light source of claim 1, wherein the first and second phosphors are selected from the group consisting of:

BaMg₂Al₁₆O₂₇;

Eu² ;

Ca₈Mg(SiO₄₎₄Cl₂;

Eu² , Mn² ;

Y₂O₃;

Bi³ ,Eu² ;

Y₃Al₅O₁₂;

Ce;

Y₂O₂S;

Eu;

ZnS;

Cu,Ag; and

mixtures thereof.

8. The light source of claim 1, wherein the phosphors further include a third phosphor which is capable of absorbing a part of the light from at least one of the first light emitting component and/or the second light emitting component and emitting light of a fifth wavelength.

9. The light source of claim 1, further including:

a third light emitting component which emits light at a wavelength different from that of the first and second wavelengths.

10. The light source of claim 9, further including:

a phosphor which is capable of absorbing a part of the light from the third light emitting component and emitting light of a wavelength which is different from the that of the light emitted from the third light emitting component.

11. The light source of claim 10, wherein the third phosphor is substantially unaffected by light of the first and second wavelengths.

12. The light source of claim 1, further including:

a housing; and

a reflective coating disposed on an interior surface of the housing, the light emitting components being positioned within the housing.

13. The light source of claim 12, further including a transparent plate which closes an open end of the housing and wherein the phosphors are in the form of a coating on the transparent plate.

14. A light source comprising:

a first light emitting component which emits light at a first wavelength;

a second light emitting component which emits light at a second wavelength different from that of the first wavelength; and

phosphors positioned to receive the light emitted by the first and second light emitting components, the phosphors including;

a first phosphor which absorbs a part of the light from the first light emitting component and emits light of a third wavelength, and

a second phosphor which absorbs a part of the light from the second light emitting component and emits light of a fourth wavelength, the second phosphor being excited relatively less by light of the first wavelength than by light of the second wavelength, the phosphors being dispersed in a medium which contacts and encapsulates the light emitting components.

15. The light source of claim 1, wherein the light emitting components comprise GaN semiconductor materials.

16. The light source of claim 14, wherein the GaN semiconductor materials for each of the light emitting components are formed on a single substrate.

17. The light source of claim 4, wherein the controller includes a rheostat, which variably adjusts the power supplied to one of the first and second light emitting components.

18. The light source of claim 17, wherein the controller includes a switch, which connects the first and second light sources with a source of power.

19. The light source of claim 4, wherein the controller includes a control system which determines the amount of power to be supplied to the first and second light emitting components in accordance with a color of light selected by an operator.

20. A method of changing the color of light comprising:

providing a first light emitting component which emits light of a first wavelength, a second light emitting component which emits light of a second wavelength, a first phosphor which absorbs a part of the light from the first light emitting component and emits light of a longer wavelength, and a second phosphor which absorbs a part of the light from the second light emitting component and emits light of a longer wavelength different from the wavelength of the light emitted by the first phosphor, the second phosphor relatively less affected by light of the first wavelength than by light of the second wavelength;

adjusting power supplied to at least one of the first and second light emitting components separately from the other of the first and second light emitting components such that the amount of light emitted by the at least one of the first and second light emitting components is adjusted; and

combining the light emitted by the first phosphor and the second phosphor.

21. The method of claim 20, wherein the first phosphor is excited by both the first and the second light emitting components.

22. The method of claim 20, wherein the step of adjusting power supplied to at least one of the first and second light emitting components includes separately adjusting power supplied to both the first and second light emitting components.