Systems and methods for calibrating light output by light-emitting diodes

• US 8,013,281 B2
• Filed: 12/30/2008
• Issued: 09/06/2011
• Est. Priority Date: 09/29/1999
• Status: Expired due to Fees

• Current Assignee: Signify North America Corporation (Signify N.V.)
• Original Assignee: Philips Solid-State Lighting Solutions (Koninklijke Philips N.V.)
• Inventors: Lys, Ihor A., Morgan, Frederick M.
• Primary Examiner(s): Epps; Georgia Y
• Assistant Examiner(s): WYATT, KEVIN S
• Application Number:
  US12/345,953
• Publication Number:
  US 20100148689A1
• Time in Patent Office: 980 Days
• Field of Search: 250/205, 315/291, 315/307, 362/800
• US Class Current: 250/205
• 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 2001/4252 for testing LED's
• CPC Class Codes: H05B 45/00 Circuit arrangements for operating light-emitting diodes [LED]
• CPC Class Codes: H05B 45/20 Controlling the colour of the light
• CPC Class Codes: H05B 45/22 using optical feedback
• CPC Class Codes: H05B 45/325 Pulse-width modulation [PWM]
• CPC Class Codes: Y10S 362/80 Light emitting diode

Abstract

A system and method for calibrating light output from an LED is provided. The system includes a support on which an LED is positioned, a photosensor to measure the light output from the LED, and means for calibrating and adjusting the light output of the LED. Calibration is accomplished by measuring the light output from the LED, comparing such output against a reference value, and adjusting the measured output against the reference value.

Claims

1. An LED-based lighting apparatus, comprising:

at least one first LED to generate first radiation having a first spectrum;

at least one second LED to generate second radiation having a second spectrum different than the first spectrum;

a memory for storing at least one first calibration value and at least one second calibration value, wherein the first calibration value represents a difference between a peak value of the first LED and a reference value established for the first LED, and wherein the second calibration value represents a difference between a peak value of the second LED and a reference value established for the second LED; and

at least one controller to receive at least first and second lighting commands, the at least one controller configured to;

control the at least one first LED and the at least one second LED using a pulse width modulation technique, the at least first and second lighting commands representing respective duty cycles of pulse width modulation signals used to control the at least one first LED and the at least one second LED,

apply the at least one first calibration value to the first lighting command to control the at least one first LED so as to output the first radiation at a first calibrated intensity that substantially corresponds in a predetermined manner to the first lighting command, and

apply the at least one second calibration value to the second lighting command to control the at least one second LED so as to output the second radiation at a second calibrated intensity that substantially corresponds in a predetermined manner to the second lighting command.

2. The apparatus of claim 1, wherein the at least one first LED and the at least one second LED are arranged with respect to each other so as to mix the first and second radiation having the respective first and second calibrated intensities to produce a single calibrated color of the visible radiation emanating from the apparatus at a given time.

3. The apparatus of claim 2, wherein the at least first and second lighting commands are provided to the at least one controller such that the single calibrated color of the visible radiation emanating from the apparatus is a calibrated substantially white color.

4. The apparatus of claim 3, further comprising an at least partially transparent housing that at least partially encloses at least the at least one first LED and the at least one second LED.

5. The apparatus of claim 4, wherein the at least partially transparent housing is configured to resemble a conventional light bulb.

6. The apparatus of claim 5, wherein the at least partially transparent housing comprises at least one connector that is adapted to engage mechanically and electrically with a conventional light socket arrangement.

7. The apparatus of claim 1, wherein the at least one controller is configured as an addressable controller to receive the at least first and second lighting commands via a network connection based on an address associated with the addressable controller.

8. The apparatus of claim 7, wherein the at least first and second lighting commands are communicated over the network connection using a DMX protocol.

9. The apparatus of claim 1, wherein the at least one controller is configured as an addressable controller to receive the at least first and second lighting commands via a network connection based on an address associated with the addressable controller.

10. The apparatus of claim 9, wherein the at least first and second lighting commands are communicated over the network connection using a DMX protocol.

11. A method, comprising acts of:

A) energizing at least one first LED so as to generate first radiation having a first spectrum;

B) energizing at least one second LED so as to generate second radiation having a second spectrum different than the first spectrum;

C) providing at least first and second lighting commands, the at least first and second lighting commands representing respective duty cycles of pulse width modulation signals for controlling the at least one first LED and the at least one second LED;

D) retrieving from at least one memory at least one first calibration value and at least one second calibration value, wherein the first calibration value represents a difference between a peak value of the first LED and a reference value established for the first LED, and wherein the second calibration value represents a difference between a peak value of the second LED and a reference value established for the second LED;

E) applying the at least one first calibration value to the first lighting command to control the at least one first LED so as to output the first radiation at a first calibrated intensity that substantially corresponds in a predetermined manner to the first lighting command; and

F) applying the at least one second calibration value to the second lighting command to control the at least one second LED so as to output the second radiation at a second calibrated intensity that substantially corresponds in a predetermined manner to the second lighting command.

12. The method of claim 11, further comprising an act of:

mixing the first and second radiation having the respective first and second calibrated intensities to produce a single calibrated color of the visible radiation at a given time.

13. The method of claim 12, wherein the act C) comprises an act of:

providing the at least first and second lighting commands such that the single calibrated color of the visible radiation emanating from the apparatus is a calibrated substantially white color.

14. The method of claim 11, wherein the act C) comprises an act of:

C1) providing the at least first and second lighting commands as addressed commands via a network connection.

15. The method of claim 14, wherein the act C1) comprises an act of:

providing the at least first and second lighting commands via a network connection using a DMX protocol.