LED luminaire with light sensor configurations for optical feedback

• US 6,741,351 B2
• Filed: 06/07/2001
• Issued: 05/25/2004
• Est. Priority Date: 06/07/2001
• Status: Expired due to Term

• Current Assignee: Signify Holding B.V. (Signify N.V.)
• Original Assignee: Koninklijke Philips Electronics N.V. (Koninklijke Philips N.V.)
• Inventors: Marshall, Thomas M, Schuurmans, Frank J P, Pashley, Michael D
• Primary Examiner(s): Bruce, David V.
• Assistant Examiner(s): Artman, Thomas R.
• Application Number:
  US09/876,661
• Publication Number:
  US 20030030808A1
• Time in Patent Office: 1,083 Days
• Field of Search: 356/406, 356/416, 356/425, 356/420, 359/629, 359/618
• US Class Current: 356/406
• CPC Class Codes: F21V 23/0457 the sensor sensing the operating status of the lighting device, e.g. to detect failure of a light source or to provide feedback to the device
• CPC Class Codes: F21Y 2113/13 comprising an assembly of point-like light sources
• CPC Class Codes: F21Y 2115/10 Light-emitting diodes [LED]
• CPC Class Codes: G01J 1/0488 with spectral filtering
• CPC Class Codes: G01J 1/32 adapted for automatic variation of the measured or reference value regulation of light intensity G05D25/00
• CPC Class Codes: G01J 1/4228 arrangements with two or more detectors, e.g. for sensitivity compensation
• CPC Class Codes: G01J 2001/4252 for testing LED's
• CPC Class Codes: G02B 6/0006 Coupling light into the fibre in general G02B6/4298
• CPC Class Codes: G02B 6/4204 the coupling comprising intermediate optical elements, e.g. lenses, holograms encapsulated active devices H01S5/02208, H01L33/52
• CPC Class Codes: H05B 45/00 Circuit arrangements for operating light-emitting diodes [LED]
• CPC Class Codes: H05B 45/22 using optical feedback
• CPC Class Codes: H05B 45/40 Details of LED load circuits

Abstract

White light emitting LED luminaire incorporates an array of red, green and blue emitting LEDs and a feedback arrangement to maintain a desired color balance. The feedback arrangement includes photodiodes positioned and enabled to separately measure the light output of each RGB color component. In one embodiment, a single photodiode or array of photodiodes is positioned to intercept reflected light from a partially reflecting element placed in the path of the combined output of the LED array. Individual colors are measured sequentially by pulsing the LEDs and photodiodes or by the use of color filters. In an alternate embodiment, each LED has an associated photodiode, either incorporated into the LED package or in a separate package.

Claims

1. An LED luminaire comprising;

an array of LEDs comprising at least one LED in each of plurality of colors,

a condenser lens positioned to direct the combined light output of the array of LEDs to a target light guide,

a partially reflecting element positioned to reflect a portion of the light output from the condenser lens back toward the LED array, and

a light sensor positioned to intercept and measure at least a portion of the reflected light.

2. The LED luminaire of claim 1 further comprising;

means for supplying electrical current to said LED array, whereby said LEDs in each said color have a light output, and the LED array has a combined light output,

means for providing the reflected light output of each color separately to the light sensor,

means for comparing the measured light output for each color to a respective desired light output for each color, and

means for adjusting the electrical current to the LEDs in each color based on said comparison, whereby a desired combined light output may be achieved.

3. The LED luminaire of claim 2 in which the means for providing the reflected light output of each color separately to the light sensor comprises means for selectively turning off the LEDs so that the light sensor measures the light output for each color separately in a series of time pulses.

4. The LED luminaire of claim 2 in which the means for providing the reflected light output of each color separately to the light sensor comprises color filter means for selectively filtering out the light output of each separate LED color.

5. The LED luminaire of claim 4 in which the light sensor comprises an array of photodiodes.

6. The LED luminaire of claim 5 in which color filter means comprises separate color filters associated with the individual photodiodes.

7. The LED luminaire of claim 5 in which the light sensor additionally comprises a light diffuser and a light integrator.

8. An LED luminaire comprising;

an array of LEDs comprising at least one LED in each of a plurality of colors,

a condenser lens positioned to direct the combined light output of the array of LEDs to a target light guide, and

an array of light sensors, each light sensor associated with an LED or a partial array of LEDs, each light sensor positioned to intercept and measure at least a portion of the light output of its associated LED or partial array of LEDs, at least first and second ones of the light sensors being adapted to intercept and measure light output from mutually-exclusive subsets of the LEDs.

9. The LED luminaire of claim 8 further comprising;

means for supplying electrical current to said LED array, whereby said LEDs in each said color have a light output, and the LED array has a combined light output,

means for comparing the measured light output for each color to a respective desired light output for each color, and

means for adjusting the electrical current to the LEDs in each color based on said comparison, whereby a desired combined light output may be achieved.

10. The LED luminaire of claim 8, further comprising a filter configured and arranged with the first light sensor to pass light from a first one of the mutually-exclusive subsets of the LEDs to the first light sensor and to filter light from a second one of the mutually-exclusive subsets of the LEDs.

11. The LED luminaire of claim 10, further comprising a second filter configured and arranged with the second light sensor to pass light from the second one of the mutually-exclusive subsets of the LEDs to the second sensor and to filter light from the first one of the mutually-exclusive subsets of the LEDs.

12. The LED luminaire of claim 8, wherein the first light sensor is configured and arranged with the array of LEDs such that light from a first one of the mutually-exclusive subsets reaches the first light sensor and that light from a second one of the mutually-exclusive subsets does not reach the first light sensor.

13. The LED luminaire of claim 12, wherein the second light sensor is configured and arranged with the array of LEDs such that light from the second one of the mutually-exclusive subsets reaches the second light sensor and that light from the first one of the mutually-exclusive subsets does not reach the second light sensor.

14. An LED luminaire comprising

an array of LEDs comprising at least one LED in each of a plurality of colors,

a condenser lens positioned to direct the combined light output of the array of LEDs to a target light guide, and

an array of light sensors, each light sensor associated with an LED or a group of three LEDs, each light sensor positioned to intercept and measure at least a portion of the light output of its associated LED or group of LEDs.