Method and apparatus for extending the color depth of displays

• US 20070109251A1
• Filed: 11/17/2005
• Published: 05/17/2007
• Est. Priority Date: 11/17/2005
• Status: Active Grant

• Current Assignee: Honeywell International Inc.
• Original Assignee: Honeywell International Inc.
• Inventors: Cernasov, Andrei, De La Vega, Fernando, Porawski, Donald
• Granted Patent: US 7,746,303 B2
• Time in Patent Office: Days
• US Class Current: 345/102
• CPC Class Codes: G09G 2310/0237 Switching ON and OFF the backlight within one frame
• CPC Class Codes: G09G 2320/0271 Adjustment of the gradation levels within the range of the gradation scale, e.g. by redistribution or clipping
• CPC Class Codes: G09G 2320/0633 by amplitude modulation of the brightness of the illumination source
• CPC Class Codes: G09G 2320/0646 Modulation of illumination source brightness and image signal correlated to each other
• CPC Class Codes: G09G 3/2018 by time modulation using two or more time intervals
• CPC Class Codes: G09G 3/3406 Control of illumination source illumination devices structurally associated with liquid crystal cells G02F1/1336

Abstract

A method of extending color depth in a display includes determining pixel sub-intervals for pixel intervals in a video signal, modulating a transmissivity of a display panel of the display from one sub-interval to another sub-interval, and modulating backlight intensity of a backlight from the one sub-interval to the another sub-interval.

Claims

1. A method of extending color depth in a display, comprising:

determining pixel sub-intervals for pixel intervals in a video signal;

modulating a transmissivity of a display panel of the display from one sub-interval to another sub-interval; and

modulating backlight intensity of a backlight from the one sub-interval to the another sub-interval.

2. The method of claim 1, further comprising synchronizing the modulating the backlight intensity from one sub-interval to the another sub-interval and the modulating the transmissivity of the display panel from the one sub-interval to the another sub-interval.

3. The method of claim 2, wherein the backlight intensity is modulated step-wise between the sub-intervals of each pixel interval.

4. The method of claim 2, wherein the backlight intensity is modulated between sub-intervals such that an average of an intensity for the pixel interval is equal to an equivalent uniform backlight intensity.

5. The method of claim 2, wherein the backlight intensity is modulated in a binary pattern between sub-intervals.

6. The method of claim 2, wherein synchronizing the modulating the backlight intensity from one sub-interval to the another sub-interval and the modulating the transmissivity of the display panel from the one sub-interval to the another sub-interval, comprises:

receiving a desired output of a pixel for a pixel interval;

determining a modulation of the backlight intensity; and

determining a modulation of the transmissivity of the pixel, wherein the modulation of the transmissivity is synchronized with the modulation of the backlight intensity to produce the desired output.

7. The method of claim 6, further comprising:

powering the backlight based on the determined modulation of the backlight intensity; and

setting the transmissivity of the pixel based on the determined modulation of the transmissivity of the pixel.

8. A method of extending color depth in a display, comprising:

determining pixel sub-intervals for pixel intervals in a video signal;

determining a light source modulation for the pixel sub-intervals;

modulating intensity of a light source based on the light source modulation; and

synchronizing a transmittance of a display panel of the display with the light source modulation for each sub-interval.

9. The method of claim 8, wherein the light source modulation is step-wise between the sub-intervals of each pixel interval.

10. The method of claim 8, wherein the light source intensity is modulated between sub-intervals such that an average of an intensity for the pixel intervals is equal to an equivalent uniform light source intensity.

11. The method of claim 8, wherein the light source modulation is modulated in a binary pattern between sub-intervals.

12. The method of claim 8, further comprising:

receiving a desired output of a pixel of the display panel for a pixel interval; and

determining the light source modulation based on the received desired output.

13. The method of claim 12, further comprising:

determining a modulation of the transmissivity of the pixel,

wherein the modulation of the transmissivity is synchronized with the light source modulation to produce the desired output.

14. The method of claim 13, further comprising:

powering the light source based on the light source modulation; and

setting transmissivity of the pixel based on the determined modulation of the transmissivity of the pixel.

15. A display with extended color depth, comprising:

a light source;

a light source driver coupled to the light source;

a transmissive display panel disposed adjacent to the light source;

a display panel control circuit coupled to the display panel; and

a dithering circuit coupled to the light source driver and display panel control circuit, the dithering circuit comprising;

logic for determining pixel sub-intervals for pixel intervals in a video signal,

logic for modulating a transmissivity of the display panel from one sub-interval to another sub-interval, and

logic for modulating light source intensity from the one sub-interval to the another sub-interval.

16. The display of claim 15, wherein the dithering circuit further comprises:

logic for synchronizing the modulating the light source intensity from one sub-interval to the another sub-interval and the modulating the transmissivity of the display panel from the one sub-interval to the another sub-interval.

17. The display of claim 16, wherein the light source driver further comprises:

logic for modulating the intensity of the light source step-wise between the sub-intervals of each pixel interval.

18. The display of claim 16, wherein the logic for synchronizing comprises:

logic for receiving a desired output of a pixel for a pixel interval; and

logic for determining a modulation of the light source intensity.

19. The display of claim 18, wherein the logic for synchronizing, further comprises:

logic for determining a modulation of the transmissivity of the pixel; and

logic for synchronizing the determined modulation of the transmissivity of the pixel with the modulation of the light source intensity to produce the desired output.

20. The display of claim 19, wherein the display further comprises:

logic for powering the light source based on the modulation of the light source; and

logic for setting transmissivity of the pixel based on the determined modulation of the transmissivity of the pixel.