Variable brightness LCD backlight

• US 20060044254A1
• Filed: 01/27/2005
• Published: 03/02/2006
• Est. Priority Date: 08/31/2004
• Status: Active Grant

• Current Assignee: NVIDIA Corporation
• Original Assignee: NVIDIA Corporation
• Inventors: Kirk, David B.
• Granted Patent: US 7,502,010 B2
• Time in Patent Office: Days
• US Class Current: 345/102
• CPC Class Codes: G09G 2320/0646 Modulation of illumination source brightness and image signal correlated to each other
• CPC Class Codes: G09G 2330/021 Power management, e.g. power saving
• CPC Class Codes: G09G 2360/16 Calculation or use of calculated indices related to luminance levels in display data
• CPC Class Codes: G09G 3/3413 Details of control of colour illumination sources

Abstract

A display for a computer system, such as an LCD, is configured to consume less power when compared to conventional designs. The display includes a screen and at least one backlight configured to illuminate the screen. An input to the at least one backlight is adjustable to produce a desired level of brightness. The input may be computed based on a generated source image and a defined constraint. An input to the display is computed based on the input to the at least one backlight and the source image. The input to the display modifies the level of brightness provided by the at least one backlight to produce a viewable image.

Claims

1. A method for displaying a viewed image on a liquid crystal display (LCD), comprising:

generating a source image;

modifying an input to a backlight of the LCD device to illuminate the LCD based on the source image; and

generating an LCD input image to the LCD based on the source image and the input to the backlight.

2. The method of claim 1, wherein the LCD input image is based on a first brightness bitmap associated with the source image.

3. The method of claim 1, wherein the step of modifying the input to the backlight comprises computing an intensity gain based on the source image.

4. The method of claim 3, wherein computing the intensity gain is further based on a brightness profile of the backlight.

5. The method of claim 3, wherein the intensity gain ranges from zero to approximately one.

6. The method of claim 1, wherein the modified backlight input causes the backlight to illuminate the LCD to provide a pixel in the viewed image with a brightness that is equal to or greater than a minimum brightness, the minimum brightness being a brightness assigned to the pixel in the source image and also being the greatest brightness assigned to any pixel in the source image.

7. The method of claim 1, further comprising the step of generating a brightness bitmap associated with the viewed image based on the LCD input image and the illumination produced by the backlight, wherein the brightness bitmap is substantially similar to a brightness bitmap associated with the source image.

8. The method of claim 7, wherein the backlight comprises first and second segments, and the method includes the step of modifying an input to each of the segments of the backlight so that the segments illuminate each pixel of the LCD with a brightness level at least as great as a brightness assigned to said each pixel in a brightness bitmap associated with the source image.

9. A method for displaying a viewed image, comprising:

generating a source image having a first brightness bitmap;

modifying a first input to a first backlight and a second input to a second backlight based on the first brightness bitmap to illuminate a display surface of a display device, wherein the first backlight and the second backlight are part of a backlight array within the display device; and

generating a second brightness bitmap associated with the viewed image based on the first brightness bitmap and the illumination produced by the backlight array.

10. The method of claim 9, wherein the step of modifying the first input and the second input comprises computing a first intensity gain for the first backlight and a second intensity gain for the second backlight based on the first brightness bitmap.

11. The method of claim 10, wherein computing the first intensity gain and the second intensity gain is further based on a first brightness profile of the first backlight and a second brightness profile of the second backlight.

12. The method of claim 11, wherein the first intensity gain and the second intensity gain are computed using the equation, I(x,y)=<

IA*BrightnessA(x,y)+IB*BrightnessB(x,y), wherein I(x,y) represents the first brightness bitmap, IA represents the first intensity gain, IB represents the second intensity gain, BrightnessA(x,y) represents the first brightness profile, and BrightnessB(x,y) represents the second brightness profile.

13. The method of claim 11, further comprising the step of computing a third brightness bitmap associated with a display device input image (or LCD input image) based on the first brightness bitmap, the first intensity gain and the second intensity gain.

14. The method of claim 13, wherein the third brightness bitmap is computed using the equation, L(x,y)=I(x,y)/[IA*BrightnessA(x,y)+IB*BrightnessB(x,y)].

15. The method of claim 13, wherein the second brightness bitmap is generated based on the third brightness bitmap and the illumination produced by the backlight array.

16. A system for displaying a viewed image, comprising:

a display device having a backlight; and

one or more processors configured to carry out the steps of;

generating a source image having a first brightness bitmap; and

modifying an input to the backlight to illuminate a display surface of the display device based on the first brightness bitmap.

17. The system of claim 16, wherein the one or more processors are further configured to carry out the steps of generating a second brightness bitmap based on the first brightness bitmap and the input to the backlight and transmitting the second brightness bitmap to the display device.

18. The system of claim 17, wherein a third brightness bitmap associated with the viewed image is generated based on the second brightness bitmap and the illumination produced by the backlight.

19. A computer-readable medium storing instructions for causing a computing device to display a viewed image by performing the steps of:

modifying an input to a backlight of a display device based on first brightness bitmap associated with a source image, wherein the backlight is used to illuminate a display surface of the display device; and

generating a second brightness bitmap based on the input to the backlight and the first brightness bitmap.

20. The computer-readable medium of claim 19, further comprising the step of transmitting the second brightness bitmap to the display device to generate a third brightness bitmap associated with the viewed image, wherein the third brightness bitmap is based on the second brightness bitmap and the illumination produced by the backlight.

21. A display system for controllably illuminating a liquid crystal display (LCD) to display a viewed image, comprising:

a processor,

a backlight, and

an image display surface on the LCD, wherein

the processor is adapted to respond to a source image to control the intensity of the backlight so that the brightness of a pixel in the viewed image on the image display surface approximates the brightness assigned to the pixel in the source image.

22. A display system as claimed in claim 21, wherein the processor is further adapted to define an input image to the LCD based on the controlled backlight intensity and the source image.

23. A display system as claimed in claim 22, wherein a brightness level produced by the backlight is at least as great as a brightness associated with a brightest pixel in the source image.

24. A display as claimed in claim 22, wherein the backlight comprises at least two segments, and the processor controls the segments to produce a brightness level that is at least as great as a brightness associated with a brightest pixel in the source image.