Method and system for variable color lighting

• US 7,990,083 B2
• Filed: 10/06/2006
• Issued: 08/02/2011
• Est. Priority Date: 10/13/2005
• Status: Active Grant

• Current Assignee: Signify Holding B.V. (Signify N.V.)
• Original Assignee: Koninklijke Philips Electronics N.V. (Koninklijke Philips N.V.)
• Inventors: Deurenberg, Peter Hubertus Franciscus, De Mol, Eugen Jacob
• Primary Examiner(s): Philogene; Haissa
• Application Number:
  US12/090,142
• Publication Number:
  US 20080238339A1
• Time in Patent Office: 1,761 Days
• Field of Search: 315/307, 315/308, 315/312, 315/318, 315/316, 315/324, 315/294, 315/297, 345/82, 345/83, 345/77, 345589-593, 345/600, 345/601, 345/690, 362/230, 362/231, 362/276, 250/205, 353/85, 353/121, 348/742
• US Class Current: 315/318
• CPC Class Codes: H04N 1/6058 Reduction of colour to a range of reproducible colours, e.g. to ink- reproducible colour gamut
• CPC Class Codes: H05B 45/20 Controlling the colour of the light
• CPC Class Codes: H05B 47/10 Controlling the light source

Abstract

A method, for controlling color output of a variable color lighting system (1) capable of emitting light within a color gamut, comprising the steps of receiving (10) a request for a target color (T), converting the target color (T) to a set of lighting system control parameters, and applying (15) the set of lighting system control parameters, thereby controlling the color output of the lighting system (1). The step of converting comprises the steps of determining (11) a target set (DT) of lighting system control parameters corresponding to the target color (T), evaluating (12) the target set (Dτ) of lighting system control parameters with respect to a range of allowable control parameters, thereby determining whether the target color (T) is outside the color gamut, and, when the target color (T) is outside the color gamut, determining (14) an approximation set (DA) of control parameters, the approximation set corresponding to an output color (A1; A2) within the color gamut, the output color (A1; A2) being an approximation of the target color (T).

Claims

1. A method, for controlling color output of a variable color lighting system capable of emitting light within a color gamut, comprising the steps of:

receiving a request for a target color;

converting said target color to a set of lighting system control parameters; and

applying said set of lighting system control parameters, thereby controlling the color output of said lighting system, characterized in that said step of converting comprises the steps of;

determining a target set of lighting system control parameters corresponding to said target color;

evaluating said target set of lighting system control parameters with respect to a range of allowable control parameters, thereby determining whether said target color is outside said color gamut; and

when said target color is outside said color gamut, determining an approximation set of control parameters, said approximation set corresponding to an output color (A_l;

A₂) within said color gamut, said output color being an approximation of said target color.

2. A method according to claim 1, wherein said step of determining an approximation set comprises the steps of:

selecting a correction set of lighting system control parameters corresponding to a color within said color gamut; and

forming said approximation set by combining said target set with said correction set multiplied by a correction factor.

3. A method according to claim 2, wherein said approximation set is formed according to the following relation:

D_A=D_T+a*D_C;

where D_A is the approximation set, is the target set, is the correction set, and a is the correction factor.

4. A method according to claim 2, wherein each set of said control parameters corresponds to a set of duty cycles for at least three light-sources comprised in said lighting system.

5. A method according to claim 4, wherein a target color (T) outside said color gamut is indicated by at least one of said duty cycles comprised in said target set (D_T) having a negative value.

6. A method according to claim 4 or 5, wherein said correction factor (a) is determined such that all of the duty cycles comprised in said approximation set become greater than or equal to zero.

7. A method according to claim 2, wherein said correction set corresponds to a white point on a blackbody curve.

8. A method according to claim 2, wherein said correction set is a unity vector.

9. A method according to claim 1, further comprising the step of:

transmitting, to at least a second lighting system, an out-of-gamut warning.

10. A method according to claim 9, further comprising the step of:

transmitting, to said at least second lighting system, color co-ordinates representing said output color.

11. A computer program module adapted to run on a controller in a variable color lighting system to perform the steps of claim 1.

12. A controller, for controlling color output of a variable color lighting system comprising at least two lighting devices, said controller being configured to:

receive a request for a target color;

convert said target color to a set of lighting system control parameters; and

apply said set of lighting system control parameters to said lighting devices, thereby controlling the color output of said lighting system,

characterized in that said controller is further configured to;

determine a target set of lighting system control parameters corresponding to said target color;

evaluate said target set of lighting system control parameters with respect to a range of allowable control parameters, thereby determining whether said target color is outside a color gamut; and

when said target color is outside said color gamut, determine an approximation set of control parameters, said approximation set corresponding to an output color inside said color gamut, said output color being an approximation of said target color.

13. A controller according to claim 12, wherein said controller is further adapted to:

select a correction set of lighting system control parameters corresponding to a color within said color gamut; and

form said approximation set by combining said target set with said correction set multiplied by a correction factor.

14. A controller according to claim 12, wherein the controller is further configured to transmit, to at least a second lighting system, an out-of-gamut warning.

15. A controller according to claim 14, wherein the controller is further configured to transmit, to said at least second lighting system, color co-ordinates representing said output color.

16. A variable color lighting system capable of emitting light within a color gamut, comprising:

at least two lighting devices, each arranged to controllably emit light of a primary color; and

a controller according to claim 12.

17. A lighting network comprising a plurality of variable color lighting systems according to claim 16, said variable color lighting systems being arranged to communicate over said lighting network.

18. A controller according to claim 13, wherein the controller is adapted to form said approximation set according to the following relation:

D_A=D_T+a*D_C;

where D_A is the approximation set, D_T is the target set, D_C is the correction set, and a is the correction factor.