Light emitting diode (LED) illumination control system and method

• US 7,384,150 B2
• Filed: 05/27/2005
• Issued: 06/10/2008
• Est. Priority Date: 05/27/2005
• Status: Expired due to Fees

• Current Assignee: 3M Innovative Properties Company (3M Company)
• Original Assignee: 3M Innovative Properties Company (3M Company)
• Inventors: Prince, Dennis W.
• Primary Examiner(s): Dowling; William C.
• Application Number:
  US11/139,829
• Publication Number:
  US 20060268236A1
• Time in Patent Office: 1,110 Days
• Field of Search: 353/85, 353/30, 353/31, 353/86, 353/39, 353/84, 353/94, 362/341, 362/295, 362/231, 348742-744, 348/771
• US Class Current: 353/31
• CPC Class Codes: G03B 21/005 Projectors using an electronic spatial light modulator but not peculiar thereto
• CPC Class Codes: H04N 9/3111 for displaying the colours sequentially, e.g. by using sequentially activated light sources sequential projection in colour photography G03B33/08
• CPC Class Codes: H04N 9/3155 for controlling the light source light source control per se H05B35/00 – H05B47/00; control of an illumination source for displays in general G09G3/3406
• CPC Class Codes: H04N 9/3164 using multiple light sources
• CPC Class Codes: H04N 9/3182 Colour adjustment, e.g. white balance, shading or gamut white balance per se H04N9/73; control of amplitude of colour signals H04N9/68; colour control circuits for displays in general G09G5/02, G09G3/2003, G09G3/3607

Abstract

An LED illumination system includes control circuitry and first, second and third colored LEDs. The control circuitry sequentially drives the first, second and third colored LEDs in a color cycle frame with relative duty cycles having a known relationship that achieves a color balance. The control circuitry also operates to introduce at least one spoke period in the color cycle frame, during which the first, second and third LEDs are driven in a manner that is controlled to provide brightness adjusting light that matches the color balance achieved by the relative duty cycles of the first, second and third LEDs during sequential driving thereof.

Claims

1. A method of controlling a light emitting diode (LED) illumination system that includes a first colored LED, a second colored LED and a third colored LED, the method comprising:

sequentially operating the first colored LED, the second colored LED, and the third colored LED in a color cycle frame with relative duty cycles having a known relationship that achieves a color balance; and

operating the first colored LED, the second colored LED and the third colored LED during at least one spoke period in the color cycle frame, the operation of the first colored LED, the second colored LED and the third colored LED during the at least one spoke period being controlled to provide brightness adjusting light that matches the color balance achieved by the relative duty cycles of the first colored LED, the second colored LED, and the third colored LED during sequential operation thereof, wherein the operation of the first colored LED, the second colored LED and the third colored LED during the at least one spoke period is controlled by pulse width modulation of signals driving the LEDs.

2. The method of claim 1, wherein the brightness adjusting light provided during the at least one spoke period is provided, to achieve white peaking.

3. The method of claim 1, wherein the brightness adjusting light provided during the at least one spoke period is provided to achieve gray level bit expansion.

4. The method of claim 1, wherein the at least one spoke period occurs during a transition between sequential operation of different ones of the first colored LED, the second colored LED, and the third colored LED.

5. The method of claim 1, wherein the first, second and third colored LEDs are red, green and blue.

6. The method of claim 5, wherein the relative duty cycle of the green LED is greater than the relative duty cycles of the red LED and the blue LED.

7. A light emitting diode (LED) illumination system comprising:

a first colored LED;

a second colored LED;

a third colored LED;

control circuitry operatively connected to the first, second and third colored LEDs, the control circuitry being operable to;

sequentially drive the first colored LED, the second colored LED, and the third colored LED in a color cycle frame with relative duty cycles having a known relationship that achieves a color balance; and

drive the first colored LED, the second colored LED and the third colored LED during at least one spoke period in the color cycle frame, the driving of the first colored LED, the second colored LED and the third colored LED during the at least one spoke period in a manner that is controlled to provide brightness adjusting light that matches the color balance achieved by the relative duty cycles of the first colored LED, the second colored LED, and the third colored LED during sequential driving thereof, wherein the control circuitry controls the driving of first colored LED, the second colored LED and the third colored LED during at least one spoke period by pulse width modulation of signals driving the LEDs.

8. The LED illumination system of claim 7, wherein the control circuitry drives the first colored LED, the second colored LED and the third colored LED during at least one spoke period to achieve white peaking.

9. The LED illumination system of claim 7, wherein the control circuitry drives the first colored LED, the second colored LED and the third colored LED during at least one spoke period to achieve gray level bit expansion.

10. The LED illumination system of claim 7, wherein the at least one spoke period occurs during a transition between sequential operation of different ones of the first colored LED, the second colored LED, and the third colored LED.

11. The LED illumination system of claim 7, wherein the first, second and third colored LEDs are red, green and blue.

12. The LED illumination system of claim 11, wherein the relative duty cycle of the green LED is greater than the relative duty cycles of the red LED and the blue LED.

13. A method of controlling an illumination system that includes first, second and third light sources for respectively providing first, second and third colors of light, the control scheme comprising:

sequentially operating the first, second and third light sources in a color cycle frame with relative duty cycles having a known relationship that achieves a color balance; and

operating the first, second and third light sources during at least one spoke period in the color cycle frame in a manner that is controlled to provide brightness adjusting light that matches the color balance achieved by the relative duty cycles of the first, second and third light sources during sequential operation thereof;

wherein the operation of the first, second and third light sources during the at least one spoke period is controlled by pulse width modulation of signals driving the light sources.

14. The method of claim 13, wherein the brightness adjusting light provided during the at least one spoke period is provided to achieve white peaking.

15. The method of claim 13, wherein the brightness adjusting light provided during the at least one spoke period is provided to achieve gray level bit expansion.

16. A method of controlling a light emitting diode (LED) illumination system that includes a first colored LED, a second colored LED and a third colored LED, the method comprising:

sequentially operating the first colored LED, the second colored LED, and the third colored LED in a color cycle frame with relative duty cycles having a known relationship that achieves a color balance; and

operating the first colored LED, the second colored LED and the third colored LED during at least one spoke period in the color cycle frame, the operation of the first colored LED, the second colored LED and the third colored LED during the at least one spoke period being controlled to provide brightness adjusting light that matches the color balance achieved by the relative duty cycles of the first colored LED, the second colored LED, and the third colored LED during sequential operation thereof, herein the brightness adjusting light provided during the at least one spoke period is provided to achieve gray level bit expansion.

17. A light emitting diode (LED) illumination system comprising:

a first colored LED;

a second colored LED;

a third colored LED;

control circuitry operatively connected to the first, second and third colored LEDs, the control circuitry being operable to;

sequentially drive the first colored LED, the second colored LED, and the third colored LED in a color cycle frame with relative duty cycles having a known relationship that achieves a color balance; and

drive the first colored LED, the second colored LED and the third colored LED during at least one spoke period in the color cycle frame, the driving of the first colored LED, the second colored LED and the third colored LED during the at least one spoke period in a manner that is controlled to provide brightness adjusting light that matches the color balance achieved by the relative duty cycles of the first colored LED, the second colored LED, and the third colored LED during sequential driving thereof, wherein the control circuitry drives the first colored LED, the second colored LED and the third colored LED during at least one spoke period to achieve gray level bit expansion.

18. A method of controlling an illumination system that includes first, second and third light sources for respectively providing first, second and third colors of light, the control scheme comprising:

sequentially operating the first, second and third light sources in a color cycle frame with relative duty cycles having a known relationship that achieves a color balance; and

operating the first, second and third light sources during at least one spoke period in the color cycle frame in a manner that is controlled to provide brightness adjusting light that matches the color balance achieved by the relative duty cycles of the first, second and third light sources during sequential operation thereof, wherein the brightness adjusting light provided during the at least one spoke period is provided to achieve gray level bit expansion.