METHOD OF MODELING THE LIGHT FIELD CREATED BY A LOCAL-DIMMING LED BACKLIGHT FOR AN LCD DISPLAY

• US 20110227940A1
• Filed: 03/18/2010
• Published: 09/22/2011
• Est. Priority Date: 03/18/2010
• Status: Active Grant

• Current Assignee: STMicroelectronics Incorporated (STMicroelectronics NV)
• Original Assignee: STMicroelectronics Incorporated (STMicroelectronics NV)
• Inventors: Neal, Greg
• Granted Patent: US 8,766,904 B2
• Time in Patent Office: Days
• US Class Current: 345/589
• CPC Class Codes: G09G 2320/0238 Improving the black level
• CPC Class Codes: G09G 2320/0285 using tables for spatial correction of display data
• CPC Class Codes: G09G 2320/064 by time 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 2320/066 for control of contrast
• CPC Class Codes: G09G 2360/12 Frame memory handling
• CPC Class Codes: G09G 2360/16 Calculation or use of calculated indices related to luminance levels in display data
• CPC Class Codes: G09G 2360/18 Use of a frame buffer in a display terminal, inclusive of the display panel
• CPC Class Codes: G09G 3/3426 the different display panel areas being distributed in two dimensions, e.g. matrix
• CPC Class Codes: G09G 3/3611 Control of matrices with row and column drivers

Abstract

A controller for an LCD display is described. The controller can control an LED backlight that includes an array of LED lighting elements and an LCD panel that includes a number of pixels. The controller can modulate an individual or groups of the lighting elements in the LED backlight, such as dimming lighting elements, to control a light-field emitted from the LED backlight. The modulation of the lighting elements, such as dimming, can improve image contrast ratios that are generated using the LCD display. Methods and apparatus are described that can simplify calculations used to determine 1) the light-field generated by the LED backlight and 2) a correction factor for adjusting pixel data. The correction factor can be used to adjust an amount of light transmitted by each pixel in the LCD panel to compensate for the backlight producing a light-field that is brighter in some areas and dimmer in other areas.

Claims

1. In a liquid crystal display (LCD) controller, a method controlling a backlight and a LCD panel comprising:

receiving image data comprising a plurality of frames;

determining, using at least the received image data, a lighting level for each of a plurality of zones in the backlight wherein each zone includes one or more light-emitting diodes (LEDs);

driving each of the plurality of zones according to its determined lighting level;

determining a pixel setting for each of a plurality of pixels in the LCD panel based upon an estimated amount of light reaching each of the plurality of pixels from the backlight; and

configuring the LCD panel with the pixel settings to display an image associated with the image data.

2. The method of claim 1 wherein a lighting level of at least one zone is dimmed to improve a contrast ratio of the displayed image.

3. The method of claim 1 further comprising mapping a portion of the image data to each of the plurality of zones and determining the lighting level for each of the plurality of zones using the portion of image data associated with each zone.

4. The method of claim 3, wherein the lighting levels for each of the plurality of zones is determined on a frame by frame basis.

5. The method of claim 1 further comprising providing a grid with a plurality of grid points and estimating the amount of light reaching each of the grid points from the backlight wherein a number of grid points is less than a number of the plurality of pixels.

6. The method of claim 5, further comprising interpolating from the estimated amount of light reaching the grid points to determine the estimated amount of light reaching each of the plurality of pixels.

7. The method of claim 5, wherein for each grid point, the estimated amount of light reaching is generated as a summation of contributions of an amount of light emitted from each of the plurality of zones in the backlight.

8. The method of claim 5, wherein the estimation of the amount of light reaching each of the grid points is performed for a plurality of different grid point simultaneously.

9. The method of claim 1, wherein the plurality of zones are driven asynchronously such that the lighting levels for each of the plurality of zone are updated at different times.

10. The method of claim 1, wherein over a time period in which a single frame of image data is displayed, a lighting level for one of the plurality of zones is determined from a frame of image data different than the single frame of image data.

11. Computer readable medium for storing computer code for controlling in a LCD controller a backlight and a LCD panel, the computer readable medium comprising:

computer code for receiving image data comprising a plurality of frames;

computer code for determining, using at least the received image data, a lighting level for each of a plurality of zones in the backlight wherein each zone includes one or more light-emitting diodes (LEDs);

computer code for driving each of the plurality of zones according to its determined lighting level;

computer code for determining a pixel setting for each of a plurality of pixels in the LCD panel based upon an estimated amount of light reaching each of the plurality of pixels from the backlight; and

computer code for configuring the LCD panel with the pixel settings to display an image associated with the image data.

12. The computer readable medium of claim 11, further comprising computer code for mapping a portion of the image data to each of the plurality of zones and determining the lighting level for each of the plurality of zones using the portion of image data associated with each zone

13. The computer readable medium of claim 11, further comprising computer code for providing a grid with a plurality of grid points and estimating the amount of light reaching each of the grid points from the backlight wherein a number of grid points is less than a number of the plurality of pixels.

14. The computer readable medium of claim 13, further comprising computer code for interpolating from the estimated amount of light reaching the grid points to determine the estimated amount of light reaching each of the plurality of pixels.

15. An apparatus for displaying images comprising:

an LCD panel comprising a plurality of pixels for displaying the images;

an LED backlight including a plurality of zones for illuminating the LCD panel wherein each of the plurality of zones includes one or more LEDs;

a controller, coupled to the LCD panel and the LED backlight, designed or configured to

     1) receive image data comprising a plurality of frames;

     2) determine, using at least the received image data, a lighting level for each of a plurality of zones in the backlight;

     3) drive each of the plurality of zones according to its determined lighting level; and

     4) determining a pixel setting for each of a plurality of pixels in the LCD panel based upon an estimated amount of light reaching each of the plurality of pixels from the backlight; and

     5) configuring the LCD panel with the pixel settings to output the displayed images associated with the image data.

16. The apparatus of claim 15, wherein the apparatus is configured as a flat panel television.

17. The apparatus of claim 15, further comprising:

a memory for storing data indicating how an intensity of light diminishes as a function of distance from a location in each zone.

18. The apparatus of claim 15, wherein a lighting level of at least one zone is dimmed to improve a contrast ratio of the displayed images.

19. The apparatus of claim 15, wherein the controller is further designed or configured to map a portion of each frame of the image data to each of the plurality of zones and determine the lighting level for each of the plurality of zones using the portion of each frame mapped to each zone.

20. The apparatus of claim 15, wherein the estimated amount of light reaching each of the plurality of pixels is based upon a summation of an amount of light reaching each pixel from each zone.

21. An integrated circuit, comprising:

a zone brightness setting determiner block;

a grid brightness calculator block; and

a processor in communication with the zone brightness setting determiner block and the grid brightness calculator block arranged to improve a contrast ratio of image displayed on an LCD by determining a lighting level for a plurality of LEDs in a backlight of the LCD and by determining a light-field generated from the backlight at each pixel location of an LCD panel.