Method and system for controlling a light source

• US 6,576,881 B2
• Filed: 04/06/2001
• Issued: 06/10/2003
• Est. Priority Date: 04/06/2001
• Status: Expired due to Fees

• Current Assignee: Koninklijke Philips Electronics N.V. (Koninklijke Philips N.V.)
• Original Assignee: Koninklijke Philips Electronics N.V. (Koninklijke Philips N.V.)
• Inventors: Van Der Sijde, Arjen, Muthu, Subramanian
• Primary Examiner(s): LE, QUE TAN
• Application Number:
  US09/827,629
• Publication Number:
  US 20020195541A1
• Time in Patent Office: 795 Days
• Field of Search: 250/205, 250/226, 250/214.R, 250/214.1, 250/206, 356/405-408, 356/416-420, 356/425, 356/451
• US Class Current: 250/205
• CPC Class Codes: H05B 45/20 Controlling the colour of the light
• CPC Class Codes: H05B 45/22 using optical feedback

Abstract

A light output control system for implementing a method for sensing the tri-stimulus values for controlling a light output illuminated from an LED based luminary is disclosed. The system comprises one or more filter/photo diode sensors for sensing a first set of tri-stimulus values of the light output and providing signals indicative thereof. The signals are utilized in a transformation matrix whereby a second set of tri-stimulus values is obtained. The system controls the light output as a function of the second set of tri-stimulus values.

Claims

1. A method for controlling a light output illuminating from a luminary including at least one light emitting diode, said method comprising:

sensing a first set of tri-stimulus values of the light output;

transforming said first set of tri-stimulus values into a second set of tri-stimulus values, said second set of tri-stimulus values being representative of a standard calorimetric system; and

controlling the light output as a function of the second set of tri-stimulus values.

2. The method of claim 1, further comprising:

measuring a third set of tri-stimulus values of a plurality of light outputs from a plurality of luminaries, each luminary including a plurality of light emitting diodes;

sensing a fourth set of tri-stimulus values of said plurality of light outputs;

determining a transformation matrix as a function of said second set of tri-stimulus values and said third set of tri-stimulus values; and

applying the transformation matrix to said first set of tri-stimulus values to thereby transform said first set of tri-stimulus values to said second set of tri-stimulus values when said transformation matrix is linear.

3. The method of claim 2, further comprising:

positioning a plurality of sensors relative to said plurality of luminaries to thereby sense said fourth set of tri-stimulus values of said plurality of light outputs; and

positioning at least two sensors of said plurality of sensors relative to the luminary to thereby sense said first set of tri-stimulus values of the light output.

4. The method of claim 1, further comprising:

measuring a third set of tri-stimulus values and a first set of xy coordinates and lumens of a plurality of light outputs from a plurality of luminaries, each luminary including a plurality of light emitting diodes;

sensing a fourth set of tri-stimulus values and a second set of xy coordinates and lumens of said plurality of light outputs;

determining a transformation matrix as a function of said second set of tri-stimulus values and said third set of tri-stimulus values; and

applying the transformation matrix to said first set of tri-stimulus values to thereby transform said first set of tri-stimulus values to said second set of tri-stimulus values when said transformation matrix is linear and a differential error between said first set of xy coordinates and lumens and said second set of xy coordinates and lumens is within a maximum error limit.

5. The method of claim 4, further comprising:

positioning a plurality of sensors relative to said plurality of luminaries to thereby sense said fourth set of tri-stimulus values and said first set of xy coordinates and lumens of said plurality of light outputs; and

positioning at least two sensors of said plurality of sensors relative to the luminary to thereby sense said first set of tri-stimulus values of the light output.

6. The method of claim 1, further comprising:

determining a first set of xy coordinates and lumens of the light output as a function of said second set of tri-stimulus values; and

controlling the light output as a function of the second set of tri-stimulus values and the first set of xy coordinates and lumens.

7. The method of claim 6, further comprising:

measuring a third set of tri-stimulus values of a plurality of light outputs from a plurality of luminaries, each luminary including a plurality of light emitting diodes;

sensing a fourth set of tri-stimulus values of said plurality of light outputs;

determining a transformation matrix as a function of said second set of tri-stimulus values and said third set of tri-stimulus values; and

applying the transformation matrix to said first set of tri-stimulus values to thereby transform said first set of tri-stimulus values to said second set of tri-stimulus values when said transformation matrix is linear.

8. The method of claim 7, further comprising:

positioning a plurality of sensors relative to said plurality of luminaries to thereby sense said fourth set of tri-stimulus values; and

positioning at least two sensors of said plurality of sensors relative to the luminary to thereby sense said first set of tri-stimulus values of the light output.

9. The method of claim 6, further comprising:

measuring a third set of tri-stimulus values and a second set of xy coordinates and lumens of a plurality of light outputs from a plurality of luminaries, each luminary including a plurality of light emitting diodes;

sensing a fourth set of tri-stimulus values and a third set of xy coordinates and lumens of said plurality of light outputs;

determining a transformation matrix as a function of said second set of tri-stimulus values and said third set of tri-stimulus values; and

applying the transformation matrix to said first set of tri-stimulus values to thereby transform said first set of tri-stimulus values to said second set of tri-stimulus values when said transformation matrix is linear and a differential error between said second set of xy coordinates and lumens and said third set of xy coordinates and lumens is within a maximum error limit.

10. The method of claim 9, further comprising:

positioning a plurality of sensors relative to said plurality of luminaries to thereby sense said fourth set of tri-stimulus values and said third set of xy coordinates and lumens of said plurality of light outputs; and

positioning at least two sensors of said plurality of sensors relative to the luminary to thereby sense said first set of tri-stimulus values of the light output.

11. A method of selectively employing at least two sensors of a plurality of sensors within a light output control system, said method comprising:

measuring a first set of tri-stimulus values and a first set of xy coordinates and lumens of at least one light output;

operating the plurality of sensors to sense a second set of tri-stimulus values and a second set of xy coordinates and lumens of said at least one light output; and

computing a transformation matrix as a function of the first set of tri-stimulus values and the second set of tri-stimulus values.

12. The method of claim 11, further comprising:

rejecting the plurality of sensors when said transformation matrix is nonlinear; and

employing the at least two sensors of the plurality of sensors in the system when the transformation matrix is linear.

13. The method of claim 11, further comprising:

comparing said first set of xy coordinates and said second set of xy coordinates and lumens to obtain a differential error when said transformation matrix is linear;

rejecting the plurality of sensors when said differential error exceeds a maximum error limit; and

employing the at least two sensors of the plurality of sensors in the system when the differential error is within a maximum error limit.

14. A method for controlling a light output illuminating from a luminary including a plurality of light emitting diodes, said method comprising:

sensing a first set of tri-stimulus values of the light output;

transforming said first set of tri-stimulus values into a second set of tri-stimulus values;

determining a set of xy coordinates and lumens as function of said set of tri-stimulus values; and

controlling a color and a lighting level of the light output as a function of the second set of tri-stimulus values and said set of xy coordinates and lumens.

15. A system for controlling a light output illuminating from a luminary including a plurality of light emitting diodes, said system comprising:

a plurality of sensors operable to provide a first set of signals indicative of a first set of tri-stimulus values of the light output; and

a first controller is operable to apply a transformation matrix to said first set of tri-stimulus values as indicated by said first set of signals to determine a second set of tri-stimulus values and a set of xy coordinates and lumens of the light output.

16. The system of claim 15, wherein

said first controller is further operable to provide a signal to the luminary, said signal indicative of an adjustment of said light output in view of said second set of tri-stimulus values and said set of xy coordinates and lumens of the light output.

17. The system of claim 15, further comprising:

a second controller operable to provide a signal to the luminary, said signal indicative of an adjustment of said light output in view of said second set of tri-stimulus values and said set of xy coordinates and lumens of the light output; and

wherein said first controller is further operable to provide a second set of signals indicative of said second set of tri-stimulus values and said set of xy and lumens coordinates to said second controller.

18. A computer program product in a computer readable medium, said computer program product for controlling a light output illuminating from a luminary, said computer program product comprising:

a first computer readable code for applying a transformation matrix to a first set of tri-stimulus values of the light output to determine a second set of tri-stimulus values and a set of xy coordinates and lumens of the light output; and

a second computer readable code for controlling the light output as a function of said second set of tri-stimulus values and said set of xy coordinates and lumens of the light output.