Methods, Apparatus and Articles of Manufacture to Calibrate Lighting Units

• US 20130038241A1
• Filed: 10/12/2012
• Published: 02/14/2013
• Est. Priority Date: 09/24/2008
• Status: Active Grant

• Current Assignee: B/E Aerospace, Inc. (Raytheon Technologies Corporation d/b/a RTX)
• Original Assignee: B/E Aerospace, Inc. (Raytheon Technologies Corporation d/b/a RTX)
• Inventors: Johannessen, Eric, LAWRENCE, KEVIN, Walsh, Andrew B., Waring, JR., Richard
• Granted Patent: US 9,018,853 B2
• Time in Patent Office: Days
• US Class Current: 315/294
• CPC Class Codes: H05B 45/22 using optical feedback
• CPC Class Codes: H05B 45/46 having LEDs disposed in parallel lines

Abstract

A system and appertaining method calibrate a color LED light unit comprising at least first-, second-, and third-color LEDs, comprising: a) defining a target color on a color map to calibrate; b) selecting initial calibration coefficients associated with the target color; c) storing the initial or updated calibration coefficients in a non-volatile memory of the light unit; d) controlling the light unit to drive the LEDs to attempt to emit the target color, producing an attempted color, utilizing the calibration coefficients; e) measuring the attempted color to determine if it matches the target color within a predefined tolerance; f) if the attempted color matches the target color, then terminating the method; g) if the attempted color does not match the target color, then performing the following; h) selecting a color component; i) adapting at least one calibration coefficient associated with the selected color component; and j) performing (c)-(i) again.

Claims

1. A method for calibrating a color LED light unit comprising at least first-, second-, and third-color LEDs, comprising:

a) defining a target color on a color map to calibrate;

b) selecting initial calibration coefficients associated with the target color;

c) storing the initial or updated calibration coefficients in a non-volatile memory of the light unit;

d) controlling the light unit to drive the LEDs to attempt to emit the target color, producing an attempted color, utilizing the calibration coefficients;

e) measuring the attempted color to determine if it matches the target color within a predefined tolerance;

f) if the attempted color matches the target color, then terminating the method;

g) if the attempted color does not match the target color, then performing the following;

h) selecting a color component;

i) adapting at least one calibration coefficient associated with the selected color component; and

j) performing (c)-(i) again.

2. The method according to claim 1, wherein the first color is red, the second color is blue, and the third color is green.

3. The method according to claim 2, wherein the LED light unit further comprises a white LED.

4. The method according to claim 3, wherein the controller determines which of the LEDs to turn on and at what intensities based on the following mathematical equations:

F(W)=W−

k_wwW 

 

(1)

F(R)=(R−

k_rrR)+k_rgG+k_rbB+k_rwW 

 

(2)

F(B)=(B−

k_bbB)+K_brR+k_bgG+k_bwW 

 

(3)

F(G)=(G−

k_ggG)+k_grR+k_gbB+k_gwW 

 

(4)

where the coefficients;

5. The method according to claim 1, wherein the controlling of the light unit is performed using variations in a pulse width in a pulse-width-modulated (PWM) signal.

6. The method according to claim 5, wherein the variations comprise at least 1024 different values.

7. The method according to claim 1, wherein the calibration coefficients are represented by 7-, 8-, 16-, or 24-bit values.

8. The method according to claim 1, wherein the determining a color match comprises:

matching to a level that is indistinguishable to the human eye.

9. The method according to claim 1, wherein the determining a color match comprises:

matching to a predefined multiplier of a MacAdam Ellipse.

10. The method according to claim 1, further comprising:

performing (a)-(j) for one or more additional target colors.

11. The method according to claim 10, wherein at least three colors are used as target colors, and the three colors define a color gamut as three points of vertices of a triangle.

12. The method according to claim 11, further comprising:

measuring a statistically significant plurality of each color class LED;

determining a variance for each color class LED;

defining a worst case color gamut within a predetermined probability; and

defined the tree points to specifically bound the worst case color gamut.

13. The method according to claim 11, wherein the vertices represent virtual primary colors.

14. The method according to claim 13, wherein the vertices require driving of the red, green, and blue LEDs with non-zero values.

16. A non-transitory computer program product, comprising a computer usable medium having a computer readable program code embodied therein, said computer readable program code adapted to be executed to implement the method according to claim 1.

15. A system for calibrating a color LED light unit, wherein:

the color LED light unit comprises;

at least first-, second-, and third-color LEDs; and

a non-volatile memory; and

the system comprises;

a) a target defining unit that defines a target color on a color map to calibrate;

b) an assigning unit that selects initial calibration coefficients associated with the target color and stores the initial or updated calibration coefficients in the non-volatile memory;

c) a controller that controls the light unit to drive the LEDs to attempt to emit the target color, producing an attempted color, utilizing the calibration coefficients;

d) a sensor that measures the attempted color to determine if it matches the target color within a predefined tolerance; and

e) a selection and adaption unit configured such that;

f) if the attempted color matches the target color, then the system ceases performing calibration;

g) if the attempted color does not match the target color, then a selection unit selects a color component, and an adaption unit adapts at least one calibration coefficient associated with the selected color component.