METHODS, LUMINAIRES AND SYSTEMS FOR MATCHING A COMPOSITE LIGHT SPECTRUM TO A TARGET LIGHT SPECTRUM

• US 20100188022A1
• Filed: 10/16/2009
• Published: 07/29/2010
• Est. Priority Date: 03/18/2003
• Status: Active Grant

• Current Assignee: Electronic Theatre Controls Incorporated
• Original Assignee: Electronic Theatre Controls Incorporated
• Inventors: Wood, Michael W., Kinzer, David J., Gerlach, Robert
• Granted Patent: US 8,403,523 B2
• Time in Patent Office: Days
• US Class Current: 315/312
• CPC Class Codes: F21W 2131/406 for theatres, stages or film studios
• CPC Class Codes: F21Y 2115/10 Light-emitting diodes [LED]
• CPC Class Codes: H05B 45/24 using electrical feedback from LEDs or from LED modules
• CPC Class Codes: H05B 47/10 Controlling the light source

Abstract

Methods, luminaires and systems for matching a composite light spectrum to a target light spectrum are disclosed. Method embodiments may be optimized for simultaneously maximizing luminous output with minimal chromaticity error. Method embodiments may further be optimized for simultaneously minimizing both chromaticity and spectral error. Embodiments of the present invention may be used with composite light sources having four or more distinct dominant colors within the visible spectrum.

Claims

1. A method of matching a composite light spectrum to a target light spectrum, the method comprising:

providing a light emitting diode (LED) array, the LED array comprising emitters having four or more distinct dominant wavelengths within visible spectrum for generating an output composite light spectrum; and

minimizing a difference between CIE chromaticity coordinates of the target light spectrum and the composite light spectrum while simultaneously maximizing luminous output of the LED array.

2. The method according to claim 1, wherein minimizing a difference between CIE chromaticity coordinates of the target light spectrum and the composite light spectrum comprises:

(1) calculating the CIE chromaticity coordinates of the target spectrum, x_t,y_t, using at least one of;

source color temperature, color standard and subject to be illuminated;

(2) calculating the CIE chromaticity coordinates of the output composite light spectrum, x_o,y_o;

(3) calculating a chromaticity error, E_c, between the CIE chromaticity coordinates of the target spectrum, x_t,y_t, and the chromaticity coordinates of the output composite light spectrum, x_o,y_o; and

(4) adjusting mix coefficients of the emitters and recalculating steps (2) and (3) to minimize the chromaticity error, E_c.

3. The method according to claim 2, wherein minimizing the chromaticity error, E_c, comprises applying a least squares optimization process.

4. The method according to claim 1, wherein maximizing luminous output of the LED array comprises calculating a total luminous output by integrating an output composite light spectrum function multiplied by a CIE photopic luminous efficacy function over all visible wavelengths.

5. The method according to claim 1, wherein minimizing a difference between CIE chromaticity coordinates of the target light spectrum and the composite light spectrum comprises applying an optimization process selected from the group consisting of:

least squares, linear, quadratic, conic, smooth non-linear and non-smooth.

6. A method of matching a composite light spectrum to a target light spectrum, the method comprising:

providing a light emitting diode (LED) array, the LED array comprising emitters having four or more distinct dominant wavelengths within visible spectrum for generating an output composite light spectrum; and

simultaneously minimizing differences between CIE chromaticity coordinates and spectral differences between the target light spectrum and the composite light spectrum.

7. The method according to claim 6, wherein minimizing the differences between CIE chromaticity coordinates of the target light spectrum and the composite light spectrum, comprises:

(1) calculating the CIE chromaticity coordinates of the target spectrum, x_t,y_t, using at least one of;

source color temperature, color standard and subject to be illuminated;

(2) calculating the CIE chromaticity coordinates of the output composite light spectrum, x_o,y_o;

(3) calculating a chromaticity error, E_c, between the CIE chromaticity coordinates of the target spectrum, x_t,y_t, and the chromaticity coordinates of the output composite light spectrum, x_o,y_o; and

(4) adjusting mix coefficients of the emitters and recalculating steps (2) and (3) to minimize the chromaticity error, E_c.

8. The method according to claim 6, wherein minimizing the differences between CIE chromaticity coordinates of the target light spectrum and the composite light spectrum, comprises minimizing a chromaticity error defined by:

E_c=W((x_o−

x_t)²+(y_o−

y_t)²),

where x_t,y_t, is the target CIE chromaticity coordinates, x_o,y_o is the output composite light CIE chromaticity coordinates and W is a weighting factor.

9. The method according to claim 6, wherein minimizing the spectral differences between the target light spectrum and the composite light spectrum, comprises minimizing:

E_s=Σ

_i=1ⁿ[(P(λ

_i)−

F(λ

_i))²]×

y(λ

_i),

where E₅ is the spectral error, P(λ

) is the target light spectrum, F(λ

) is the composite light spectrum, and y(λ

_i) is the CIE photopic function, calculated over n points across the visible spectrum.

10. A light emitting diode (LED) array including four or more distinct dominant wavelengths within visible spectrum configured for generating an output composite light spectrum matched to a preselected target light spectrum wherein the output composite light spectrum provides maximum lumen output.

11. The LED array according to claim 10, wherein providing maximum lumen output comprises maximizing:

Lumens=∫

F(λ

)V(λ

)dλ

where F(λ

) is the output composite light spectrum and V(λ

) is the CIE photopic luminous efficacy function.

12. The LED array according to claim 10, wherein the preselected target light spectrum is a color standard.

13. The LED array according to claim 12, wherein the color standard is selected from the group consisting of:

a theatrical gel color, a Pantone™

color, sunlight, and an incandescent lamp with or without color filters.

14. The LED array according to claim 10, wherein generating an output composite light spectrum matched to a preselected target light spectrum comprises minimizing a chromaticity error between the target light spectrum and the output composite light spectrum.

15. A light emitting diode (LED) array including four or more distinct dominant wavelengths within visible spectrum configured for generating an output composite light spectrum matched to a preselected target light spectrum wherein the output composite light spectrum provides best spectral match between the target light spectrum and the composite light spectrum.

16. The LED array according to claim 15, wherein generating an output composite light spectrum matched to a preselected target light spectrum comprises minimizing a chromaticity error between the target light spectrum and the output composite light spectrum.

17. The LED array according to claim 16, wherein the chromaticity error is defined as:

E_c=W((x_o−

x_t)²+(y_o−

y_t)²),

where x_t,y_t, is CIE chromaticity coordinates of the target spectrum, x_o,y_o is CIE chromaticity coordinates of the output composite light spectrum and W is a weighting factor.

18. The LED array according to claim 15, wherein providing best spectral match between the target light spectrum and the composite light spectrum comprises minimizing a spectral error between the target light spectrum and the output composite light spectrum.

19. The LED array according to claim 18, wherein the spectral error is defined as:

E_s=Σ

_i=1ⁿ[(P(λ

_i)−

F(λ

_i))²]×

y(λ

_i),

where P(λ

) is the target light spectrum, F(λ

) is the composite light spectrum, and y(λ

_i) is the CIE photopic function, calculated over n points across the visible spectrum.

20. A lighting system configured for generating an output composite light spectrum matched to a preselected target light spectrum, the system comprising:

a luminaire having LEDs of at least four distinct primary color wavelengths; and

a controller for driving the luminaire to generate a composite light spectrum, the composite light spectrum providing maximum lumen output and also matched for chromaticity with the preselected target light spectrum.

21. The system according to claim 20, wherein the controller simultaneously drives the luminaire to spectrally match the composite light spectrum to the preselected target light spectrum.

22. The system according to claim 20, wherein the control desk further comprises a fixture library having look-up tables for generating control signals driving the luminaire according to selected color standards.