Method and system for improving dimming performance in a field sequential color display device

1. A method for displaying an image on a display device having first and second light sources, the method comprising:

providing a video signal to the display device, the video signal comprising first and second video frames, each video frame comprising first and second sub-frames corresponding to the respective first and second light sources, the first and second sub-frames having adjustable on-times, and thus adjustable pulse-widths, for the first and second light sources;

operating the first light source during the first sub-frame of the first video frame to generate a first plurality of first light emission pulses, each of the first plurality of first light emission pulses having a first on-time and thus a first pulse-width, the first pulse-width equal to a minimum pulse-width, a maximum pulse-width, or a pulse-width between the minimum pulse-width and the maximum pulse-width;

operating the first light source during the first sub-frame of the second video frame to generate a second plurality of first light emission pulses, each of the second plurality of first light emission pulses having a second on-time and thus a second pulse-width, the second pulse-width equal to the minimum pulse-width, the maximum pulse-width, or a pulse-width between the minimum pulse-width and the maximum pulse-width, the second on-time being different from the first on-time, whereby the second pulse-width is different from the first pulse-width;

supplying a constant peak current to the first light source at least when the first pulse-width and the second pulse-width are equal to a pulse-width between the minimum pulse-width and the maximum pulse-width, wherein the difference in the first pulse-width and the second pulse-width varies the brightness of the first light source; and

selectively varying the peak current supplied to the first light source when either the first pulse-width or the second pulse-width is not equal to a pulse-width between the minimum pulse-width and the maximum pulse-width, to thereby further vary the brightness of the first light source.

2. The method of claim 1 , further comprising:

operating the second light source during the second sub-frame of the first video frame to generate a first plurality of second light emission pulses, each of the first plurality of second light emission pulses having a third on-time and thus a third pulse-width; and

operating the second light source during the second sub-frame of the second video frame to generate a second plurality of second light emission pulses, each of the second plurality of second light emission pulses having a fourth on-time and thus a fourth pulse-width.

3. The method of claim 2 , wherein the first light source emits light within a first frequency band and the second light source emits light within a second frequency band, the second frequency band being different from the first frequency band.

4. The method of claim 3 , further comprising generating an image with the light emitted from the first and second light sources with an image source based on the video signal.

5. The method of claim 4 , wherein the third on-time and thus the third pulse-width are the same as the first on-time and thus the first pulse-width, respectively.

6. The method of claim 5 , wherein the fourth on-time and thus the fourth pulse-width are the same as the second on-time and thus the second pulse-width, respectively.

7. The method of claim 4 , wherein the third on-time and thus the third pulse-width are different from the first on-time and thus the first pulse-width, respectively, and the fourth on-time and thus the fourth pulse-width are different from the second on-time and thus the second pulse-width, respectively.

8. The method of claim 4 , wherein the display device comprises a third light source and each video frame of the video signal comprises a third sub-frame corresponding to the third light source, and further comprising:

operating the third light source during the third sub-frame of the first video frame to generate a first plurality of third light emission pulses, each of the first plurality of third light emission pulses having a fifth on-time and a fifth pulse-width; and

operating the third light source during the third sub-frame of the second video frame to generate a second plurality of third light emission pulses, each of the second plurality of third light emission pulses having a sixth on-time and thus a sixth pulse-width.

9. The method of claim 8 , wherein the first, second, and third light sources comprise respective first, second, and third pluralities of light emitters, the image source comprises a plurality of pixels, and said generation of the image with the image source comprises configuring the plurality of pixels.

10. The method of claim 9 , further comprising adjusting the first, second, third, fourth, fifth, and sixth on-times and thus the first, second, third, fourth, fifth, and sixth pulse-widths based on usage of the respective pluralities of light emitters, a temperature on the display device, or a combination thereof.

11. A method for displaying an image on a display device having first and second pluralities of light emitters and an imaging source:

providing a video signal to the display device, the video signal comprising first and second video frames, each video frame comprising first and second sub-frames corresponding to the respective first and second pluralities of light emitters, the first and second sub-frames having adjustable on-times, and thus adjustable pulse-widths, for the first and second light sources;

operating the first plurality of light emitters during the first sub-frame of the first video frame to generate a first plurality of first light emission pulses, each of the first plurality of first light emission pulses having a first on-time and thus a first pulse-width, the first pulse-width equal to a minimum pulse-width, a maximum pulse-width, or a pulse-width between the minimum pulse-width and the maximum pulse-width;

operating the first plurality of light emitters during the first sub-frame of the second video frame to generate a second plurality of first light emission pulses, each of the second plurality of first light emission pulses having a second on-time and thus a second pulse-width, the second pulse-width equal to the minimum pulse-width, the maximum pulse-width, or a pulse-width between the minimum pulse-width and the maximum pulse-width, the second on-time being different from the first on-time, whereby the second pulse-width is different from the first pulse-width;

operating the second plurality of light emitters during the second sub-frame of the first video frame to generate a first plurality of second light emission pulses, each of the first plurality of second light emission pulses having a third on-time and thus a third pulse-width, the third pulse-width equal to the minimum pulse-width, the maximum pulse-width, or a pulse-width between the minimum pulse-width and the maximum pulse-width;

operating the second plurality of light emitters during the second sub-frame of the second video frame to generate a second plurality of second light emission pulses, each of the second plurality of second light emission pulses having a fourth on-time and thus a fourth pulse-width, the fourth pulse-width equal to the minimum pulse-width, the maximum pulse-width, or a pulse-width between the minimum pulse-width and the maximum pulse-width, the fourth on-time being different from the third on-time, whereby the fourth pulse-width is different from the third pulse-width;

supplying a constant peak current to the first plurality of light emitters at least when the first pulse-width and the second pulse-width are equal to a pulse-width between the minimum pulse-width and the maximum pulse-width, wherein the difference in the first-pulse-width and the second pulse-width varies the brightness of the first plurality of light emitters;

selectively varying the peak current supplied to the first plurality of light emitters when either the first pulse-width or the second pulse-width is not equal to a pulse-width between the minimum pulse-width and the maximum pulse-width, to thereby further vary the brightness of the first plurality of light emitters;

supplying a constant peak current to the second plurality of light emitters at least when the third pulse-width or the fourth pulse-width are equal to a pulse-width between the minimum pulse-width and the maximum pulse-width, wherein the difference in the third-pulse-width and the fourth pulse-width varies the brightness of the second plurality of light emitters;

selectively varying the peak current supplied to the second plurality of light emitters when either the third pulse-width or the fourth pulse-width is not equal to a pulse-width between the minimum pulse-width and the maximum pulse-width, to thereby further vary the brightness of the second plurality of light emitters; and

generating an image with the light emitted from the first and second pluralities of light emitters during the respective first and second on-times with the imaging device.

12. The method of claim 11 , wherein the display device further comprises a third plurality of light emitters and each video frame further comprises a third sub-frame corresponding to the third plurality of light emitters, and further comprising:

operating the third plurality of light emitters during the third sub-frame of the first video frame to generate a first plurality of third light emission pulses, each of the first plurality of third light emission pulses having a fifth on-time and thus a fifth pulse-width; and

operating the third plurality of light emitters during the third sub-frame of the second video frame to generate a second plurality of third light emission pulses, each of the second plurality of third light emission pulses having a sixth on-time and thus a sixth pulse-width, the sixth on-time being different from the fifth on-time, whereby the sixth pulse-width is different from the fifth pulse-width.

13. The method of claim 12 , further comprising adjusting the first, second, third, fourth, fifth, and sixth on-times, and thus the first, second, third, fourth, fifth, and sixth pulse-widths, based on usage of the respective pluralities of light emitters, a temperature on the display device, or a combination thereof.

14. The method of claim 13 , wherein the first, third, and fifth on-times, and thus the first, third, and fifth pulse-widths are the same, and the second, fourth, and sixth on-times, and thus the second, fourth, and sixth pulse-widths, are the same.

15. The method of claim 14 , wherein the first, third, and fifth on-times, and thus the first, third, and fifth pulse-widths, are different, and the second, fourth, and sixth on-times, and thus the second fourth, and sixth pulse-widths, are different.

16. A display device system comprising:

a backlight comprising first and second light emitters;

an image source coupled to the backlight and configured to generate an image with light emitted from the first and second light emitters; and

a controller coupled to the backlight and the image source, the controller being configured to:

provide a video signal to the backlight and the image source, the video signal comprising first and second video frames, each video frame comprising first and second sub-frames corresponding to the respective first and second light emitters of the backlight, the first and second sub-frames having adjustable on-times for the first and second light sources;

operate the first light emitter during the first sub-frame of the first video frame to generate a first plurality of first light emission pulses, each of the first plurality of first light emission pulses having a first on-time and thus a first pulse-width, the first pulse-width equal to a minimum pulse-width, a maximum pulse-width, or a pulse-width between the minimum pulse-width and the maximum pulse-width;

operate the first light emitter during the first sub-frame of the second video frame to generate a second plurality of first light emission pulses, each of the second plurality of first light emission pulses having a second on-time and thus a second pulse-width, the second pulse-width equal to the minimum pulse-width, the maximum pulse-width, or a pulse-width between the minimum pulse-width and the maximum pulse-width, the second on-time being different from the first on-time, whereby the second pulse-width is different from the first pulse-width;

supply a constant peak current to the first light emitter at least when the first pulse-width and the second pulse-width are equal to a pulse-width between the minimum pulse-width and the maximum pulse-width, wherein the difference in the first pulse-width and the second pulse-width varies the brightness of the first light emitter; and

selectively vary the peak current supplied to the first light emitter when either the first pulse-width or the second pulse-width is not equal to a pulse-width between the minimum pulse-width and the maximum pulse-width, to thereby further vary the brightness of the first light source.

17. The system of claim 16 , wherein the controller is further configured to:

operate the second light source during the second sub-frame of the first video frame to generate a first plurality of second light emission pulses, each of the first plurality of second light emission pulses having a third on-time and thus a third pulse-width; and

operate the second light source during the second sub-frame of the second video frame to generate a second plurality of second light emission pulses, each of the second plurality of second light emission pulses having a fourth on-time and thus a fourth pulse-width, the fourth on-time being different from the third on-time, whereby the fourth pulse-width is different from the third pulse-width.

18. The system of claim 17 , wherein the backlight further comprises a third light emitter and each video frame of the video signal further comprises a third sub-frame corresponding to the third light emitter, and wherein the controller is further configured to:

operate the third light source during the third sub-frame of the first video frame to generate a first plurality of third light emission pulses, each of the first plurality of third light emission pulses having a fifth on-time and thus a fifth pulse-width; and

operate the third light source during the third sub-frame of the second video frame to generate a second plurality of third light emission pulses, each of the second plurality of third light emission pulses having a sixth on-time and thus a sixth pulse-width, the sixth on-time being different from the fifth on-time, whereby the sixth pulse-width is different from the fifth pulse-width.

19. The system of claim 18 , wherein at least some of the first, second, and third light emitters are light emitting diodes and wherein the image source is a liquid crystal display comprising a plurality of pixels.

20. The system of claim 19 , further comprising a temperature sensor coupled to the backlight and configured to generate a signal representative of a temperature of the backlight and a photopic color sensor coupled to the backlight and configured to generate a signal representative of the luminance of the light emitters, and wherein the controller is further configured to adjust the first, second, third, fourth, fifth, and sixth on-times, and thus the first, second, third, fourth, fifth, and sixth pulse-widths, based on usage of the respective pluralities of light emitters, a temperature on the display device, or a combination thereof.