Calibration method and apparatus for lighting fixtures using multiple spectrum light sources and light mixing

• US 20080103714A1
• Filed: 10/25/2006
• Published: 05/01/2008
• Est. Priority Date: 10/25/2006
• Status: Active Grant

• Current Assignee: ABL IP Holding LLC (Acuity Brands, Inc.)
• Original Assignee: Renaissance Lighting Incorporated (Acuity Brands, Inc.)
• Inventors: Garbus, Michael E., Aldrich, Matthew H.
• Granted Patent: US 8,363,069 B2
• Time in Patent Office: Days
• US Class Current: 702/81
• CPC Class Codes: G01J 3/46 Measurement of colour; Colour measuring devices, e.g. colorimeters measuring colour temperature G01J5/60
• CPC Class Codes: G01J 3/462 Computing operations in or between colour spaces; Colour management systems
• CPC Class Codes: G01J 3/50 using electric radiation detectors
• CPC Class Codes: G01J 3/501 Colorimeters using spectrally-selective light sources, e.g. LEDs
• CPC Class Codes: G01J 3/506 measuring the colour produced by screens, monitors, displays or CRTs
• CPC Class Codes: G01J 3/513 having fixed filter-detector pairs
• CPC Class Codes: G01J 3/524 Calibration of colorimeters
• CPC Class Codes: H05B 45/22 using optical feedback
• CPC Class Codes: H05B 47/165 following a pre-assigned programmed sequence; Logic control [LC]
• CPC Class Codes: H05B 47/17 Operational modes, e.g. switching from manual to automatic mode or prohibiting specific operations

Abstract

Disclosed examples of optical systems having a plurality of light sources with each source having a different spectral outputs may be calibrated by measuring a spectral characteristic of the combined light with two measurements, e.g., one from a colorimeter and one from a sensor included in the system. Accordingly, one can determine a transform function in response to the two measures that models a feedback response of the optical system for each of a plurality of the inputs that would cause the optical system to generate radiant energy within a predetermined range of a spectrum. In order to calibrate the optical system, the transform function is programmed in the optical system to enable the optical system to transform an input to the optical system to a plurality of unique control signals each for controlling a respective light source of the plurality of light sources.

Claims

1. A method for calibrating an optical system having a plurality of light sources and outputting combined light from the sources wherein the plurality of light sources have different spectral outputs relative to an input setting which represents a desired characteristic of the combined light, the method comprising the steps of:

(a) generating a first set of data corresponding to measurements of a spectral characteristics of the combined output of the plurality of light sources using a calibrated meter;

(b) generating a second set of data corresponding to characteristics of the combined output of the plurality of light sources determined using a sensor different from the calibrated meter;

(c) determining a transform function in response to the first set of data and the second set of data that models a feedback response of the optical system for each of a plurality of different input settings that would cause the optical system to generate radiant energy within a predetermined range of a spectrum; and

(d) programming the transform function in the optical system to enable the optical system to transform an input to the optical system to a plurality of unique control signals each for controlling a respective light source of the plurality of light sources.

2. The method according to claim 1, wherein the plurality of light sources are configured to generate a plurality of color components so as to output combined light, further comprising repeating steps (a) and (b) for each of the plurality of different input settings which correspond to the plurality of color components.

3. The method according to claim 2, wherein step (c) further comprises the steps of:

(i) populating the first set of data and the second set of data into matrices; and

(ii) determining the transform function to transform the input to a unique control signal for each of the plurality of light sources based on the populated results.

4. The method according to claim 3, wherein the transform function comprises a plurality of transform functions.

5. The method according to claim 4, wherein at least one of the plurality of transform functions has linear characteristics.

6. The method according to claim 4, wherein at least one of the plurality of transform functions is represented by an M×

N matrix.

7. The method according to claim 2, wherein each of the plurality of color components corresponds to a primary color.

8. The method according to claim 1, wherein the second set of data corresponds to a measurement of frequency of the spectral output, further comprising the steps of:

(i) determining an amount of error attributed to the sensor used to determine the characteristics of the output of the plurality of light sources; and

(ii) adjusting the transform function for the amount of error determined in step (i).

9. The method according to claim 1, wherein the transform function determined in step (c) corresponds to a plurality of transform functions to transform the input to the plurality of unique control signals.

10. The method according to claim 9, wherein at least one of the plurality of transform functions has linear characteristics.

11. The method according to claim 9, wherein at least one of the plurality of transform functions is represented by an M×

N matrix.

12. The method according to claim 10, wherein at least one of the plurality of correlation functions has non-linear characteristics.

13. The method according to claim 11, wherein at least one of the plurality of transform functions has non-linear characteristics.

14. The method according to claim 1, wherein:

a characteristic of combined light output by the plurality of light sources based on the plurality of unique control signals is substantially the same as a desired characteristic of light represented by an input to the optical system, and

the input causes the optical system to generate radiant energy within the predetermined range of the spectrum.

15. The method according to claim 1, wherein the predetermined range of the spectrum corresponds to a visual spectrum.

16. The method according to claim 1, wherein the transform function determined in step (c) is applicable to substantially all inputs to the optical system that would cause the optical system to generate light within the predetermined range of the spectrum.

17. The method according to claim 1, wherein the first set of data corresponds to a measure of tristimulus values.

18. The method according to claim 1, wherein the second set of data corresponds to a measure of frequency values that represent spectral characteristics of light emitted from the plurality of light sources.

19. A method for operating an optical system having a plurality of light sources and outputting combined light, wherein the plurality of light sources have different spectral outputs relative to an input setting which represents a desired characteristic of the combined light, wherein the optical system includes a color sensor for measuring characteristics of the combined light, the method comprising the steps of:

(a) receiving a user input which maps color to a predefined coordinate space in at least two colors;

(b) transforming the user input to a set of expected color component values representing expected measurements of the color sensor had the plurality of light sources output light corresponding to the user input in actual operation;

(c) outputting control signals for operating the plurality of light sources based on the set of expected color components;

(d) driving the plurality of light sources based on the control signals; and

(e) adjusting the control signals based on measurements of the spectral outputs received from the color sensor following step (d).

20. The method for operating an optical system according to claim 19, wherein step (b) comprises the step of multiplying tristimulus values based on the user input by an M×

N matrix representing a transform function calibrated for the optical system.

21. The method for operating an optical system according to claim 19, further comprising the steps of:

(i) transforming the set of expected color components to a corrected set of color components based on a set of predetermined error correction factors to compensate for anticipated errors in measurements attributed to the color sensor; and

(ii) transforming the corrected set of color components to the control signals for operating the plurality of light sources.

22. The method for operating an optical system according to claim 21, wherein step (i) further comprises the step of multiplying the set of color components by an M×

N matrix of the set of predetermined error correction factors.

23. The method for operating an optical system according to claim 21, wherein step (ii) further comprises generating RGB control signals corresponding to the control signals for operating the plurality of light sources by multiplying the corrected set of color components by predetermined coefficients according to at least a second order function representing non-linear operational characteristics of the optical system.

24. The method for operating an optical system according to claim 21, wherein the set of color components corresponds to a measure of frequency values that represent spectral characteristics of light emitted from the plurality of light sources.

25. The method for operating an optical system according to claim 21, wherein the corrected set of color components corresponds to a corrected measure of frequency values that represent spectral characteristics of light emitted from the plurality of light sources.

26. The method for operating an optical system according to claim 19, wherein the transform of step (b) has a linear characteristic.

27. The method for operating an optical system according to claim 21, wherein the transform of step (i) has a linear characteristic.

28. The method for operating an optical system according to claim 21, wherein the transform of step (ii) has a non-linear characteristic.

29. A system for emitting light, comprising:

a plurality of light sources for emission of light and for thereby producing visible light to form a combined light at least of portion of which is output from the system;

a color sensor for measuring color components emitted by the plurality of light sources contained within the combined light; and

a microcontroller for processing newly user inputted color parameters and controlling illumination of the plurality of light sources,

wherein the microcontroller is configured to execute the following steps for initially driving the plurality of light sources for the newly inputted color parameters;

(a) transforming the newly inputted color parameters to a set of expected color component values representing expected measurements of the color sensor had the plurality of light sources output light corresponding to the newly inputted color parameters in actual operation; and

(b) controlling the illumination of the plurality of light sources based on the expected set of color component values.

30. The system for emitting light according to claim 29, wherein step (a) comprises the step of multiplying tristimulus values based on the newly inputted color parameters by an M×

N matrix of values representing a transform function calibrated for the system.

31. The system for emitting light according to claim 29, wherein the microcontroller is further configured to execute the following steps for initially driving the plurality of light sources for the newly inputted color parameters:

(i) transforming the set of color components to a corrected set of color components to compensate for anticipated errors in the set of components that would have been measured by the color sensor in actual operation; and

(ii) transforming the corrected set of color components to the control signals for operating the plurality of light sources.

32. The system for emitting light according to claim 31, wherein step (i) comprises the step of multiplying the set of color components by an M×

N matrix of error correction factors to compensate for anticipated errors in measurement attributed to the color sensor.

33. The system for emitting light according to claim 31, wherein step (ii) comprises multiplying the corrected set of color components by predetermined coefficients according to at least a second order function representing non-linear operational characteristics of the system.

34. The system for emitting light according to claim 31, wherein the set of color components corresponds to a measure of frequency values that represent spectral characteristics of light emitted from the plurality of light source.

35. The system for emitting light according to claim 31, wherein the corrected set of color components corresponds to a corrected measure of frequency values that represent spectral characteristics of light emitted from the plurality of light source.

36. The system for emitting light according to claim 29, wherein the transform of step (a) has a linear characteristic.

37. The system for emitting light according to claim 31, wherein the transform of step (i) has a linear characteristic.

38. The system for emitting light according to claim 31, wherein the transform of step (ii) has a non-linear characteristic.

39. The system for emitting light according to claim 31, wherein the plurality of light sources corresponds to a plurality of solid state lighting elements.

40. The system for emitting light according to claim 39, wherein the plurality of solid state lighting elements corresponds to a plurality of LEDs.

41. The system for emitting light according to claim 39, further comprising:

a plurality of digital to analog controllers (DACs) for receiving control signals output by the microcontroller; and

a plurality of light source driver circuits for receiving outputs from respective DACs and controlling respective light sources.

42. A lighting system, comprising:

a first solid state light emitting element for emitting electromagnetic energy of a first spectral characteristic;

a second solid state light emitting element for emitting electromagnetic energy of a second spectral characteristic different from the first spectral characteristic;

a mixing element coupled to receive electromagnetic energy of the first and second spectral characteristics emitted by the first and second solid state light emitting elements, for mixing the received energy to form a combined electromagnetic energy into a region to facilitate a humanly perceptible lighting application for the system;

a user interface, for user input of a desired setting for a spectral characteristic of the combined energy output;

a sensor for detecting a spectral characteristic of the combined electromagnetic energy; and

a control circuit for performing a matrix transform operation on data related to the user input of the desired setting to generate data related to expected spectral characteristic of the combined electromagnetic energy by the sensor and using the expected spectral characteristics of the combined electromagnetic energy to determine respective output settings for the first and second solid state light emitting elements, and for applying the respective output settings to control amounts of electromagnetic energy of the first and second spectral characteristics emitted by the first and second solid state light emitting elements to achieve a spectral characteristic of the combined energy substantially corresponding to the desired setting.

43. The lighting system of claim 42, wherein:

the mixing element comprises an optical integrating cavity having a reflective interior surface;

at least a portion of the reflective interior surface of the optical integrating cavity exhibits a diffuse reflectivity such that diffuse reflections of electromagnetic energy of the first and second spectral characteristics received from the first and second solid state light emitting elements combines electromagnetic energy of the first and second spectral characteristics; and

the optical integrating cavity has an optical aperture for allowing emission of electromagnetic energy reflected and combined within the interior of the cavity as the combined energy output.

44. The lighting system of claim 42, wherein:

the first solid state light emitting element comprises at least one light emitting diode for emitting visible light of a first color; and

the second solid state light emitting element comprises at least one light emitting diode for emitting visible light of a second color different from the first color.

45. The lighting system of claim 44, further comprising:

the third light emitting diode for emitting visible light of a third color different from the first and second colors;

wherein the control circuit is configured to control operation of the first, second and third light emitting diode in accord with results of the matrix transform operation.

46. The lighting system of claim 42, wherein:

the control circuit stores coefficients for the performance of the matrix transform operation; and

values of the coefficients have been determined based on operational performance of the system.

47. The lighting system of claim 44, wherein in the matrix transform operation, a matrix of the data related to the user input of the desired setting is multiplied by a matrix of transformation factors to generate a matrix of the data related to expected spectral characteristic of the combined electromagnetic energy by the sensor.

48. The lighting system of claim 47, wherein the matrix of transformation factors are based on a reverse matrix transformation between a matrix of data related to a given input of a desired setting for a spectral characteristic of the combined energy output and a matrix of data related to the spectral characteristic of the combined electromagnetic energy by the sensor based on the given input.

49. The lighting system of claim 47, wherein the matrix of data related to the user input corresponds to an M×

N matrix and the matrix of the spectral characteristic of the combined electromagnetic energy corresponds to an M×

M matrix.

50. The lighting system of claim 44, wherein in the matrix transform operation, a matrix of the data related to the spectral characteristic of the combined electromagnetic energy by the sensor is multiplied by a matrix of correction factors to compensate for anticipated errors in measurement by the color sensor.

51. The lighting system of claim 50, wherein the matrix of correction factors are based on the spectral characteristic of the combined electromagnetic energy detected by the sensor that is attributed to the first solid state light emitting element when the second solid state light element emits light and the first solid state light emitting element does not and vica versa.