LIGHT SOURCE AND METHOD FOR OPTIMISING ILLUMINATION CHARACTERISTICS THEREOF

• US 20080013314A1
• Filed: 07/12/2007
• Published: 01/17/2008
• Est. Priority Date: 07/13/2006
• Status: Active Grant

• Current Assignee: Signify Holding B.V. (Signify N.V.)
• Original Assignee: TIR Technology LP
• Inventors: Ashdown, Ian, Salsbury, Marc
• Granted Patent: US 7,772,787 B2
• Time in Patent Office: Days
• US Class Current: 362/231
• 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 45/32 Pulse-control circuits
• CPC Class Codes: H05B 45/325 Pulse-width modulation [PWM]

Abstract

The present invention provides a light source, method, computer-readable storage medium and computer program product for optimising one or more illumination characteristic thereof. In particular, the present invention provides a light source comprising four or more light-emitting elements, or groups or arrays thereof, each one of which having a respective predefined emission spectrum which, when combined in accordance with a given intensity ratio, provide illumination at a particular color temperature. This light source may comprise an internal and/or external selection module for selecting one or more illumination characteristics to be optimised, and internal and/or external computing module for optimising drive parameters of the light source to provide the optimised illumination characteristic selected. The light source may optionally be hardwired to operate according to predefined drive parameters selected, using a method, computer-readable storage medium and/or computer program product of the present invention, in order to optimise a pre-selected illumination characteristic.

Claims

1. A light source, comprising:

four or more light-emitting elements, each one of which having a respective emission spectrum;

a selection module for selecting one or more illumination characteristics for which the light source is to be optimised;

a computing module for computing, from values indicative of each said respective emission spectrum, optimised drive parameters for driving the light source to substantially attain said selected one or more illumination characteristics; and

a driving module for driving each of said four or more light-emitting elements in accordance with said optimised drive parameters.

2. The light source as claimed in claim 1, wherein said illumination characteristics are selected from the group comprising:

the CRI, the CQS, the luminous efficacy and the output power of the light source.

3. The light source as claimed in claim 1, said selection module being configured to associate a respective optimisation weight to two or more of said illumination characteristics, wherein each said respective optimisation weight is used by said computing module when computing said optimised drive parameters.

4. The light source as claimed in claim 3, wherein each said respective optimisation weight ranges substantially from 0 to 1.

5. The light source as claimed in claim 3, wherein selection of said respective optimisation weight for a given one of said illumination characteristics automatically selects said respective optimisation weight for another of said illumination characteristics according to a predefined relationship.

6. The light source as claimed in claim 5, wherein said respective optimisation weight for said given one of said illumination characteristics and said respective optimisation weight for said another one of said illumination characteristics add to 1.

7. The light source as claimed in claim 3, wherein said given one and said another one of said illuminations characteristics are respectively selected from the groups comprising the CRI and the CQS of the light source, and the luminous efficacy and the output power of the light source.

8. The light source as claimed in claim 1, wherein said drive parameters are selected from the group comprising:

output intensities, relative output intensities, drive currents, relative drive currents, duty cycles, relative duty cycles, and drive signal modulation parameters.

9. The light source as claimed in claim 1, wherein said selection module is selected from the group comprising:

one or more hardwired selection modules, one or more physical selection modules, one or more software selection modules, one or more firmware selection modules, and a combination thereof.

10. The light source as claimed in claim 1, wherein said selection module comprises a user interface enabling a user to select said one or more illumination characteristics for which the light source is to be optimised.

11. The light source as claimed in claim 1, further comprising a feedback module operatively coupled to said computing module for providing a feedback signal thereto indicative of one or more operational characteristics of the light source, wherein said computing module is further configured to account for said one or more operational characteristics and adjust said optimised drive parameters accordingly.

12. The light source as claimed in claim 1, each of said light-emitting elements comprising one or more of a respective type of light-emitting element.

13. The light source as claimed in claim 12, each said respective type being selected from the group comprising:

one or more substantially red light-emitting elements, one or more substantially amber light-emitting elements, one or more substantially orange light-emitting elements, one or more substantially green light-emitting elements, one or more substantially blue light-emitting elements, one or more substantially white light-emitting elements.

14. The light source as claimed in claim 12, each said selected type comprising one or more of a single light-emitting element, a group of similar light-emitting elements, an array of similar light-emitting elements, a cluster of similar light-emitting elements and a combination thereof.

15. The light source as claimed in claim 1, wherein the light source is an RAGB light source.

16. The light source as claimed in claim 3, wherein each said respective optimisation weight is used by said computing module to compute said optimised drive parameters via an automated optimisation routine expressed as a minimisation of a weighted illumination characteristic objective function.

17. The light source as claimed in claim 16, wherein said weighted illumination characteristic objective function is expressed as:

f(IC<sub>i=1→

n</sub>)=−

Σ

(σ

_iIC_i²)^1/2

wherein IC_i represents respective ones of said two or more illumination characteristics and σ

_i represent said respective optimisation weight associated therewith.

18. The light source as claimed in claim 17, wherein said weighted illumination characteristic objective function is expressed as:

19. The light source as claimed in claim 16, wherein said weighted illumination characteristic objective function is minimised via a Nelder-Mead Simplex method.

20. A method for driving a light source in accordance with drive parameters that optimise one or more illumination characteristics of the light source, the light source comprising four or more light-emitting elements each having a respective emission spectrum, the method comprising:

identifying for each of the four or more light emitting elements, one or more values indicative of its respective emission spectrum;

selecting the one or more illumination characteristics for which the light source is to be optimised;

calculating, using each said one or more values, the drive parameters that optimise for said selected one or more illumination characteristics; and

driving the light source in accordance with said calculated drive parameters.

21. The method as claimed in claim 20, wherein said calculating step is performed via an automated optimisation routine.

22. The method as claimed in claim 21, wherein said automated optimisation routine comprises a Needler-Mead optimisation routine.

23. The method as claimed in claim 21, wherein said automated optimisation routine is implemented by a computing module operatively coupled a drive module of the light source and configured to automatically communicate said calculated drive parameters thereto to drive the light source in accordance therewith.

24. The method as claimed in claim 20, wherein said selecting step is implemented via a user interface of the light source.

25. The method as claimed in claim 20, further comprising the step after said selecting step of associating a respective optimisation weight to each of said one or more selected illumination characteristics, said calculating step comprising calculating the drive parameters in accordance with each said respective optimisation weight.

26. The method as claimed in claim 25, wherein each said respective optimisation weight is used to compute the drive parameters via an automated optimisation routine expressed as a minimisation of a weighted illumination characteristic objective function.

27. The method as claimed in claim 26, wherein said weighted illumination characteristic objective function is expressed as:

f(IC<sub>i=1→

n</sub>)=−

Σ

(σ

_iIC_i²)^1/2

wherein IC_i represents respective ones of said two or more illumination characteristics and σ

_i represent said respective optimisation weight associated therewith.

28. The method as claimed in claim 27, wherein said weighted illumination characteristic objective function is expressed as:

29. A computer program product comprising means for implementing the steps of claim 20.

30. A computer-readable storage medium having embodied therein instructions for operating a computing module to determine drive parameters for optimising one or more selected illumination characteristics of a light source, the light source comprising four or more light-emitting elements each having a respective emission spectrum, in accordance with the following:

for each of said four or more light emitting elements, receiving as input one or more values indicative of the respective emission spectrum;

receiving as a selected input the one or more selected illumination characteristics;

calculating, from each said one or more indicative values and said selected input, the drive parameters that optimise the selected one or more illumination characteristics; and

outputting said calculated drive parameters for use in driving the light source in accordance with the selected one or more illumination characteristics.