Method for controlling the luminous flux spectrum of a lighting fixture

• US 7,023,543 B2
• Filed: 08/01/2002
• Issued: 04/04/2006
• Est. Priority Date: 08/01/2002
• Status: Expired due to Term

• Current Assignee: David W. Cunningham
• Original Assignee: David W. Cunningham
• Inventors: Cunningham, David W.
• Primary Examiner(s): Toatley, Jr., Gregory J.
• Assistant Examiner(s): GEISEL, KARA E
• Application Number:
  US10/211,769
• Publication Number:
  US 20040021859A1
• Time in Patent Office: 1,342 Days
• Field of Search: 356/300, 362/227, 315/309, 315/312
• US Class Current: 356/300
• CPC Class Codes: H05B 45/22 using optical feedback
• CPC Class Codes: H05B 45/28 using temperature feedback

Abstract

A method is disclosed for controlling a lighting fixture of a kind having individually colored light sources, e.g., LEDs, that emit light having a distinct luminous flux spectrum that varies in its initial spectral composition, that varies with temperature, and that degrades over time. The method controls such fixture so that it projects light having a predetermined desired flux spectrum despite variations in initial spectral characteristics, despite variations in temperature, and despite flux degradations over time.

Claims

1. A method for controlling the luminous flux spectrum of light produced by a lighting fixture of a kind incorporating a plurality of groups of light-emitting devices, each group emitting light having a distinct luminous flux spectrum subject to substantial initial variability, wherein the lighting fixture lacks a filter for substantially limiting the bandwidth of light emitted by any of the plurality of groups of light-emitting devices, the method comprising:

calibrating each of the plurality of groups of light-emitting device by measuring the initial flux magnitude or light emitted by the group, at a prescribed test temperature, in response to a predetermined electrical power input; and

supplying a prescribed amount of electrical power to the light-emitting devices in each of the plurality of groups of devices, such that the groups of devices cooperate to emit light having a desired composite luminous flux spectrum.

2. A method as defined in claim 1, wherein the step of calibrating further includes measuring the spectral distribution of light emitted by each of the plurality of groups of light-emitting devices in response to a predetermined electrical power input.

3. A method as defined in claim 1, wherein the method controls the lighting fixture such that is emitted light has a composite luminous flux spectrum emulating the luminous flux spectrum of a known light source, with or without a filter.

4. A method as defined in claim 1, wherein:

each of the light-emitting devices of the plurality of groups of devices is a light-emitting diode; and

the plurality of groups of light-emitting diodes include at least four groups, collectively configured to emit light spanning a substantial contiguous portion of the visible spectrum.

5. A method for controlling the luminous flux spectrum of light produced by a lighting fixture of a kind incorporating a plurality of groups of light-emitting devices, each group emitting light having a distinct luminous flux spectrum subject to substantial initial variability, the method comprising:

calibrating each of the plurality of groups of light-emitting device, by measuring the spectral distribution of light emitted by the group in response to a predetermined electrical power input, wherein the step of calibrating includes measuring the initial magnitude, the initial peak wavelength, and the initial spectral half-width of flux emitted by each of the plurality of groups of light-emitting devices at a prescribed test temperature, in response to a predetermined electrical power input; and

supplying a prescribed amount of electrical power to the light-emitting devices in each of the plurality of groups of devices, such that the groups of devices cooperate to emit light having a desired composite luminous flux spectrum.

6. A method for controlling the luminous flux spectrum of light produced by a lighting fixture of a kind incorporating a plurality of groups of light-emitting devices, each group emitting light having a distinct luminous flux spectrum subject to substantial initial variability, wherein the method controls the lighting fixture such that its emitted light has a composite luminous flux spectrum emulating the luminous flux spectrum of a known light source, with or without a filter, the method comprising:

calibrating each of the plurality of groups of light-emitting devices by measuring the flux magnitude of light emitted by the group in response to a predetermined electrical power input; and

supplying a prescribed amount of electrical power to each of the light-emitting devices in each of the plurality of groups of devices such that the plurality of groups of devices cooperate to emit light having a composite luminous flux spectrum that has a minimum normalized mean deviation across the visible spectrum relative to the luminous flux spectrum of a known light source to be emulated, with or without an associated color filter.

7. A method for controlling the luminous flux spectrum of light produced by a lighting fixture of a kind incorporating a plurality of groups of light-emitting devices, each group emitting light having a distinct luminous flux spectrum subject to substantial initial variability, the method comprising:

calibrating each of the plurality of groups of light-emitting devices by measuring the initial flux magnitude of light emitted by the group, at a prescribed test temperature, in response to a predetermined electrical power input; and

supplying a prescribed amount of electrical power to the light-emitting devices in each of the plurality of groups of devices, such that the groups of devices cooperate to emit light having a desired composite luminous flux spectrum;

wherein the distinct luminous flux spectrum of light emitted by each of the plurality of groups of light-emitting devices varies with temperature;

wherein the method further comprises determining the temperature of each of the light-emitting devices in each of the plurality of groups of devices;

and wherein the prescribed amount of electrical power that is supplied to the light-emitting devices in the step of supplying is selected, in part, based on the temperature determination for each device.

8. A method as defined in claim 7, wherein:

each group of light-emitting devices emits flux having a magnitude that varies with temperature; and

the step of calibrating each of the plurality of groups of light-emitting devices includes considering measurements of the magnitude of flux emitted by each of the plurality of groups of devices at a plurality of test temperatures.

9. A method as defined in claim 7, wherein:

each group of light-emitting devices emits flux having a magnitude and a peak wavelength that vary with temperature; and

the step of calibrating each of tho plurality of groups of light-emitting devices includes a preliminary step of measuring the magnitude and peak wavelength of flux emitted by each of the plurality of groups of devices at a plurality of test temperatures.

10. A method as defined in claim 7, wherein:

the plurality of groups of light-emitting devices are mounted on a heat sink; and

the step of determining the temperature of each of the light-emitting devices includes

measuring the temperature of the heat sink using one or more temperature sensors, and

calculating the temperature of each of the light-emitting devices based on the amount of electrical power being supplied to such device, the amount of flux emitted by the device, the thermal resistance between such device and the heat sink, and the measured temperature of the heat sink.

11. A method as defined in claim 7, wherein

the plurality of groups of light-emitting devices are mounted on a heat sink;

and

the step of determining the temperature of each of the light-emitting devices includes

measuring ambient temperature, and

calculating the temperature of each of the light-emitting devices based on the amount of electrical power being supplied to such device, the amount of flux emitted by the device, the thermal resistance between such device and the heat sink, the total amount of electrical power being supplied to all of such devices less the total amount of flux emitted by the devices, the thermal resistance between the heat sink and the surrounding air, and the measured ambient temperature.

12. A method as defined in claim 7, wherein the step of calibrating each of the plurality of groups of light-emitting devices includes considering a factor relating to flux degradation over time for such devices.

13. A method as defined in claim 12, wherein the step of calibrating each of the plurality of groups of light-emitting devices includes maintaining a record of the temperature of the device over time.

14. A method for controlling the luminous flux spectrum of light produced by a lighting fixture of a kind incorporating a plurality of groups of light-emitting devices, each group emitting light having a distinct luminous flux spectrum having a magnitude and a peak wavelength that vary with temperature, the method comprising:

determining the temperatures or the light-emitting devices in each of the plurality of groups of devices;

determining the spectral distribution of the flux emitted by each of the plurality of groups of light-emitting devices based on the temperature determinations, including a preliminary step of measuring the magnitude and peak wavelength of flux emitted by each of the plurality of groups of devices at a plurality of test temperatures; and

supplying a prescribed amount of electrical power to the light-emitting devices in each of the plurality of groups of devices, such that the groups of devices cooperate to emit light having a composite luminous flux spectrum that has a minimum normalized mean deviation across the visible spectrum relative to the luminous flux spectrum of a known light source to be emulated, with or without a color filter.

15. A method as defined in claim 14, wherein:

each group of light-emitting devices emits flux having a magnitude that varies with temperature; and

the step of determining the spectral distribution of the flux emitted by each of the plurality of groups of light-emitting devices includes considering measurements of the magnitude of flux emitted by each of the plurality of groups of devices at a plurality of test temperatures.

16. A method as defined in claim 14, wherein:

the plurality of groups of light-emitting devices are mounted on a heat sink; and

the step of determining the temperature of each of the light-emitting devices includes

measuring the temperature of the heat sink using one or more temperature sensors, and

calculating the temperature of each of the light-emitting devices based on the amount of electrical power being supplied to such device, the amount of flux emitted by the device, the thermal resistance between such device and the heat sink, and the measured temperature of the heat sink.

17. A method as defined in claim 14, wherein:

each of the light-emitting devices of the plurality of groups of devices is a light-emitting diode; and

the plurality of groups of light-emitting diodes include at least four groups, collectively configured to emit light spanning a substantial contiguous portion of the visible spectrum.

18. A method for controlling the luminous flux spectrum of light produced by a lighting fixture of a kind incorporating a plurality of groups of light-emitting devices are mounted on a heat sink, each group emitting light having a distinct luminous flux spectrum that varies with temperature, the method comprising:

determining the temperatures of the light-emitting devices in each of the plurality of groups of devices;

determining the spectral distribution of the flux emitted by each of the plurality of groups of light-emitting devices based on the temperature determinations; and

supplying a prescribed amount of electrical power to the light-emitting devices in each of the plurality of groups of devices, such that the groups of devices cooperate to emit light having a desired composite luminous flux spectrum;

wherein the step of determining the temperature of each of the light-emitting devices includes

measuring ambient temperature, and

calculating the temperature of each of the light-emitting devices based on the amount of electrical power being supplied to such device, the amount of flux emitted by the device, the thermal resistance between such device and the heat sink, the total amount of electrical power being supplied to all of such devices less the total amount of flux emitted by the devices, the thermal resistance between the heat sink and the surrounding air, and the measured ambient temperature.

19. A method for controlling the luminous flux spectrum of light produced by a lighting fixture of a kind incorporating a plurality of groups of light-emitting devices, each group emitting light having a distinct luminous flux spectrum that varies with temperature, the method comprising:

determining the temperatures of the light-emitting devices in each of the plurality of groups of devices;

determining the spectral distribution of the flux emitted by each of the plurality of groups of light-emitting devices based on the temperature determinations and also based on a factor relating to flux degradation over time for such devices; and

supplying a prescribed amount of electrical power to the light-emitting devices in each of the plurality of groups of devices, such that the groups of devices cooperate to emit light having a desired composite luminous flux spectrum.

20. A method as defined in claim 19, wherein the step of determining the spectral distribution of the flux emitted by each of the plurality of groups of light-emitting devices includes maintaining a record of the temperature of the device over time.

21. A method for controlling the luminous flux spectrum of light produced by a lighting fixture of a kind incorporating a plurality of groups of light-emitting devices, each group emitting light having a distinct luminous flux spectrum that varies with temperature, the method comprising:

determining the temperatures of the light-emitting devices in each of the plurality of groups of devices;

determining the spectral distribution of the flux emitted by each of the plurality of groups of light-emitting devices based on the temperature determinations; and

supplying a prescribed amount of electrical power to the light-emitting devices in each of the plurality of groups of devices, such that the groups of devices cooperate to emit light having a desired composite luminous flux spectrum;

wherein the step of supplying includes supplying an amount of electrical power to each of the light-emitting devices in each of the plurality of groups of devices such that the plurality of groups of devices cooperate to emit light having a composite luminous flux spectrum that has a minimum normalized mean deviation across the visible spectrum relative to the luminous flux spectrum of a known light source to be emulated, with or without a color filter.

22. A method for controlling the luminous flux spectrum of light produced by a lighting fixture of a kind incorporating a plurality of groups of light-emitting devices, each group emitting light having a distinct luminous flux spectrum subject to degradation over time, the method comprising:

establishing a time-based degradation factor for each of the plurality of groups of light-emitting devices; and

supplying a prescribed amount of electrical power to the light-emitting devices in each of the plurality of groups of devices, wherein the prescribed amount of electrical power is selected, in part, based on the time-based degradation factor established for each of the groups of devices, such that the groups of devices cooperate to emit light having a desired composite luminous flux spectrum throughout the lighting fixture'"'"'s lifetime.

23. A method as defined in claim 22, wherein the step of establishing a time-based degradation factor for each of the plurality of groups of light-emitting devices includes maintaining a record of the temperature of the devices over time.