SYSTEMS AND METHODS FOR CALIBRATING SOLID STATE LIGHTING PANELS USING COMBINED LIGHT OUTPUT MEASUREMENTS

• US 20070216704A1
• Filed: 05/21/2007
• Published: 09/20/2007
• Est. Priority Date: 11/18/2005
• Status: Active Grant

• Current Assignee: Brightplus Ventures LLC (IPValuation Partners, LLC)
• Original Assignee: CREE Incorporated (Wolfspeed, Inc.)
• Inventors: Roberts, John, You, Chenhua, Vilcans, Clinton
• Granted Patent: US 8,514,210 B2
• Time in Patent Office: Days
• US Class Current: 345/597
• CPC Class Codes: G09G 2320/041 Temperature compensation
• CPC Class Codes: G09G 2320/0693 Calibration of display systems
• CPC Class Codes: G09G 2360/145 the light originating from the display screen
• CPC Class Codes: G09G 3/3426 the different display panel areas being distributed in two dimensions, e.g. matrix
• 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: H05B 45/40 Details of LED load circuits
• CPC Class Codes: H05B 45/44 with an active control inside an LED matrix

Abstract

A method of calibrating a lighting panel including a plurality of segments, a respective segment configured to emit a first color light and a second color light in response to pulse width modulation control signals having respective duty cycles, includes activating the plurality of segments to simultaneously emit the first and second colors of light. A combined light output for the plurality of segments is measured at a measurement location to obtain aggregate emission data. Separate emission data for the first and second colors of light is determined based on the aggregate emission data. For example, the separate emission data for the first and second colors of light may be derived based on extrapolation of the aggregate emission data and expected emission data for the first and second colors of light. Related calibration systems are also discussed.

Claims

1. A method of calibrating a lighting panel comprising a plurality of segments, a respective segment configured to emit a first color of light and a second color of light in response to pulse width modulation control signals having respective duty cycles, the method comprising:

activating the plurality of segments to simultaneously emit the first and second colors of light;

measuring a combined light output for the plurality of segments at a measurement location to obtain aggregate emission data; and

determining separate emission data for the first and second colors of light based on the aggregate emission data.

2. The method of claim 1, wherein determining the separate emission data comprises:

deriving the separate emission data for the first and second colors of light based on extrapolation of the aggregate emission data and expected emission data for the first and second colors of light.

3. The method of claim 2, wherein deriving the separate emission data further comprises:

determining first and second local peak wavelengths in respective wavelength ranges corresponding to each of the first and second colors based on the aggregate emission data;

determining starting points for an extrapolation algorithm based on the first and second peak wavelength values; and

calculating separate spectral distributions for each of the first and second colors of light using the extrapolation algorithm based on the respective starting points.

4. The method of claim 3, wherein calculating separate spectral distributions for each of the first and second colors of light comprises:

extrapolating portions of the separate spectral distributions for wavelength ranges between the first and second local peak wavelengths.

5. The method of claim 1, further comprising:

determining separate luminance and/or chromaticity data for the first and/or second colors of light at the measurement location based on the separate emission data.

6. The method of claim 1, wherein each of the plurality of segments is further configured to emit a third color of light in response to the pulse width modulation control signals, wherein activating the plurality of segments further comprises activating the plurality of segments to simultaneously emit the first, second, and third colors of light, and wherein determining separate emission data further comprises determining separate emission data for the first, second, and third colors of light based on the aggregate emission data.

7. The method of claim 6, wherein the first color of light comprises light in a red wavelength range, wherein the second color of light comprises light in a green wavelength range, and wherein the third color of light comprises light in a blue wavelength range.

8. The method of claim 1, further comprising:

adjusting the duty cycle for emission of at least one of the first and second colors of light for at least one of the plurality of segments to reduce a luminance variation thereof based on the separate emission data.

9. The method of claim 1, further comprising:

determining an average segment luminance for the lighting panel based on the aggregate emission data;

determining a luminance variation of one of the plurality of segments relative to the average segment luminance;

comparing the luminance variation of the one of the plurality of segments to a threshold; and

responsive to the luminance variation of the one of the plurality of segments exceeding the threshold, adjusting the duty cycle for emission of at least one of the first and second colors of light for the one of the plurality of segments to reduce the luminance variation.

10. The method of claim 9, wherein the measurement location comprises a location at about a center of the lighting panel.

11. The method of claim 1, wherein each segment of the plurality of segments comprises a group of tiles.

12. The method of claim 1, wherein each segment of the plurality of segments comprises a bar of tiles.

13. A method of calibrating a lighting panel comprising a plurality of segments, a respective segment configured to emit red, green, and blue light in response to pulse width modulation control signals having respective duty cycles, the method comprising:

activating the plurality of segments to simultaneously emit red, green, and blue light;

measuring a combined red, green, and blue light output for the plurality of segments at a measurement location to obtain aggregate emission data; and

determining separate emission data for the red, green, and blue light based on the aggregate emission data.

14. The method of claim 13, wherein determining the separate emission data comprises:

calculating the separate emission data for the red, green, and blue light based on extrapolation of the aggregate emission data and expected emission data for the red, green, and blue light.

15. The method of claim 13, further comprising:

adjusting the duty cycle for emission of at least one of the red, green, and blue light for at least one of the plurality of segments to reduce a luminance variation thereof based on the separate emission data.

16. A calibration system for calibrating a lighting panel comprising a plurality of segments, a respective segment configured to emit a first color of light and a second color of light in response to pulse width modulation control signals having respective duty cycles, the calibration system comprising:

a calibration controller configured to be coupled to the lighting panel; and

a calibration unit coupled to the calibration controller and comprising a calorimeter;

wherein the calibration controller is configured to activate the plurality of segments to simultaneously emit the first and second colors of light, wherein the calibration unit is configured to measure a combined light output from the plurality of segments at a measurement location to obtain aggregate emission data, and wherein the calibration controller is configured to determine separate emission data for the first and second colors of light based on the aggregate emission data.

17. The calibration system of claim 16, wherein the calibration controller is configured to derive the separate emission data for the first and second colors of light based on extrapolation of the aggregate emission data and expected emission data for the first and second colors of light.

18. The calibration system of claim 17, wherein the calibration controller is further configured to determine first and second local peak wavelengths in respective wavelength ranges corresponding to each of the first and second colors based on the aggregate emission data, determine starting points for an extrapolation algorithm based on the first and second peak wavelength values, and calculate separate spectral distributions for each of the first and second colors of light using the extrapolation algorithm based on the respective starting points.

19. The calibration system of claim 18, wherein the calibration controller is configured to extrapolate portions of the separate spectral distributions for wavelength ranges between the first and second local peak wavelengths.

20. The calibration system of claim 16, wherein the calibration controller is configured to determine separate luminance and/or chromaticity data for the first and/or second colors of light at the measurement location based on the separate emission data.

21. The calibration system of claim 16, wherein each of the plurality of segments is further configured to emit a third color of light in response to the pulse width modulation control signals, and wherein the calibration controller is configured to activate the plurality of segments to simultaneously emit the first, second, and third colors of light and determine separate emission data for the first, second, and third colors of light based on the aggregate emission data.

22. The calibration system of claim 21, wherein the first color of light comprises light in a red wavelength range, wherein the second color of light comprises light in a green wavelength range, and wherein the third color of light comprises light in a blue wavelength range.

23. The calibration system of claim 16, wherein the calibration controller is configured to adjust the duty cycle for emission of at least one of the first and second colors of light for at least one of the plurality of segments to reduce a luminance variation thereof based on the separate emission data.

24. The calibration system of claim 16, wherein the calibration unit further comprises an XY positioner connected to the calorimeter and configured to move the calorimeter to the measurement location in two dimensions.

25. The calibration system of claim 16, wherein the calibration unit further comprises:

an enclosure having an entrance;

a conveyor extending from outside the enclosure to inside the enclosure through the entrance; and

a pallet on the conveyor and configured to hold the lighting panel during calibration;

wherein the conveyor and the pallet are configured to bring the lighting panel into enclosure, and wherein the colorimeter is positioned within the enclosure so as to detect the combined light output emitted from the plurality of segments of the lighting panel.