Backlight dimming and LCD amplitude boost

• US 8,085,239 B1
• Filed: 01/02/2007
• Issued: 12/27/2011
• Est. Priority Date: 12/11/2002
• Status: Active Grant

• Current Assignee: NVIDIA Corporation
• Original Assignee: NVIDIA Corporation
• Inventors: Lew, Stephen D., Ogrinc, Michael A.
• Primary Examiner(s): Eisen, Alexander
• Assistant Examiner(s): MARINELLI, PATRICK
• Application Number:
  US11/619,160
• Time in Patent Office: 1,820 Days
• Field of Search: 345/102, 345 87-100, 345204-211, 345690-696
• US Class Current: 345/102
• CPC Class Codes: G09G 2320/0276 for the purpose of adaptation to the characteristics of a display device, i.e. gamma correction
• CPC Class Codes: G09G 2320/0626 for control of overall brightness
• 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 2320/0653 Controlling or limiting the speed of brightness adjustment of the illumination source
• 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 3/3406 Control of illumination source illumination devices structurally associated with liquid crystal cells G02F1/1336
• CPC Class Codes: G09G 3/3685 Details of drivers for data electrodes

Abstract

Embodiments of the present invention generally provide methods and apparatus for reducing power consumption of backlit displays are described. Power consumption is reduced by dimming backlighting by a first scale factor and boosting pixel values by a second scale factor to compensate for the dimming. The scale factors may be constant values. Alternately, one or both of the scale factors may be determined based on pixel values for one or more frames to be displayed and/or one or more frames that have been displayed. For example, scale factors may be calculated based on an average linear amplitude of one or more frames of pixel values or from a maximum pixel value of one or more frames of pixel values. A graphical processing system is described including an integrated circuit capable of transforming a pixel value from a gamma-compensated space to a linear space.

Claims

1. A method for reducing power consumption of a backlit display, the method comprising:

sampling individual pixel values of a frame of pixels to be displayed on the backlit display to determine a plurality of maximum pixel values for the frame;

determining a first scale factor based on an average linear amplitude for the plurality of maximum pixel values;

reducing backlighting of the display by the first scale factor; and

increasing pixel values for the frame of pixels based on a second scale factor that is inversely proportional to the first scale factor and a factor k that accounts for a reduction in brightness of the backlit display due to clamping.

2. The method of claim 1, wherein the first scale factor is equal to a single maximum pixel value for the frame of pixels.

3. The method of claim 1, wherein the sampling comprises examining a luminance value of each pixel in the frame of pixels.

4. The method of claim 1, wherein the first scale factor equals the Nth maximum pixel value of the plurality of maximum pixel values, wherein N is greater than 1.

5. A non-transitory computer-readable storage medium storing instructions that when executed by a processor cause the processor to reduce power consumption of a backlit display, by performing the steps of:

sampling individual pixel values of a frame of pixels to be displayed on the backlit display to determine a plurality of maximum pixel values for the frame;

determining a first scale factor based on an average linear amplitude for the plurality of maximum pixel values;

reducing backlighting of the display by the first scale factor; and

increasing pixel values for the frame of pixels based on a second scale factor that is inversely proportional to the first scale factor and a factor k that accounts for a reduction in brightness of the backlit display due to clamping.

6. The non-transitory computer-readable storage medium of claim 5, wherein the first scale factor is equal to a single maximum pixel value for the frame of pixels.

7. The non-transitory computer-readable storage medium of claim 5, wherein the sampling comprises examining a luminance value of each pixel in the frame of pixels.

8. The non-transitory computer-readable storage medium of claim 5, wherein the first scale factor equals the Nth maximum pixel value of the plurality of maximum pixel values, wherein N is greater than 1.

9. A computing device configured for graphical processing, the computing device comprising:

a memory for storing instructions; and

an integrated circuit including a processor configured to execute the instructions and cause a reduction in power consumption of a backlit display, by performing the steps of;

sampling individual pixel values of a frame of pixels to be displayed on the backlit display to determine a plurality of maximum pixel values for the frame;

determining a first scale factor based on an average linear amplitude for the plurality of maximum pixel values;

reducing backlighting of the display by the first scale factor; and

increasing pixel values for the frame of pixels based on a second scale factor that is inversely proportional to the first scale factor and a factor k that accounts for a reduction in brightness of the backlit display due to clamping.

10. The computing device of claim 9, wherein the first scale factor is equal to a single maximum pixel value for the frame of pixels.

11. The computing device of claim 9, wherein the sampling comprises examining a luminance value of each pixel in the frame of pixels.

12. The computing device of claim 9, wherein the first scale factor equals the Nth maximum pixel value of the plurality of maximum pixel values, wherein N is greater than 1.