Methods, apparatus and articles of manufacture to calibrate lighting units

• US 9,414,459 B2
• Filed: 04/27/2015
• Issued: 08/09/2016
• 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, Walsh, Andrew B., Lawrence, Kevin, Waring, Richard Jr.
• Primary Examiner(s): Taningco, Alexander H
• Assistant Examiner(s): Correa, Nelson
• Application Number:
  US14/697,273
• Publication Number:
  US 20150230315A1
• Time in Patent Office: 470 Days
• Field of Search: None
• US Class Current: 1/1
• 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 that requires a contribution from at least the first- and second-color LEDs, wherein the defined target color is one of at least three target colors and the three colors define a color gamut as three points of vertices of a triangle;

b) selecting first and second initial calibration coefficients associated with the first- and second-color contributing LEDs that contribute to the target color;

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

d) controlling the light unit to simultaneously drive the first and second 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 corresponding to the first-color LED;

i) updating the first calibration coefficient associated with the selected color component;

j) performing (c)-(f) immediately again;

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

l) selecting a color component corresponding to the second-color LED;

m) updating the second calibration coefficient associated with the selected color component;

n) performing (c)-(f) again;

performing (a)-(j) for one or more target colors of the at least three target colors;

measuring a statistically significant plurality of LEDs of each color class;

determining a variance for each color class LED;

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

defining the three points to specifically bound the worst case color gamut.

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, further comprising determining, by a controller, 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 initial or updated first and second 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, wherein the vertices represent virtual primary colors.

11. The method according to claim 10, wherein the vertices require driving of the red, green, and blue LEDs with non-zero values.

12. 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.