Backlight dimming and LCD amplitude boost

• US 8,059,086 B1
• Filed: 12/14/2007
• Issued: 11/15/2011
• 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): Dharia; Prabodh M
• Application Number:
  US11/957,356
• Time in Patent Office: 1,432 Days
• Field of Search: 345 88-102, 345207-213, 345/522, 345/589, 345690-694, 345/905, 345/545, 315/193, 315/291, 315/209.R, 315/213, 315/169.3, 349/69, 323/271
• 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 m 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 display, the method comprising:

determining a first maximum pixel brightness value for a first frame of pixels by examining individual pixel values of the first frame;

calculating a first scale factor as a function of the first maximum pixel brightness value for the first frame;

dimming backlighting of the display by the first scale factor after sending the first frame of pixels to the display;

receiving a second frame of pixels to be displayed on the display subsequent to the first frame of pixels;

calculating a second scale factor based on the first maximum pixel brightness value for the first frame; and

increasing brightness values of the pixels of the second frame of pixels by the second scale factor to generate boosted pixel values for the second frame; and

sending the boosted pixel values to the display.

2. The method of claim 1, wherein the calculating comprises applying a low pass filter to the first maximum pixel brightness value and at least one additional maximum pixel brightness value for previous frames of pixels.

3. The method of claim 2, wherein the low pass filter is applied to the additional maximum pixel brightness values of N frames, wherein N is determined based on a response time of a backlighting element.

4. The method of claim 3, further comprising determining a second maximum pixel brightness value for the first frame of pixels prior to increasing the brightness values of the pixels of the second frame of pixels.

5. The method of claim 1, further comprising determining a second maximum pixel brightness value for the second frame of pixels as the boosted pixel values of the second frame of pixels are scanned out to the display.

16. The method of claim 1, wherein the step of increasing the brightness values of the pixels of the second frame comprises clamping the brightness values of the pixels of the second frame that are greater than the first maximum pixel brightness value.

17. The method of claim 1, further comprising monitoring an amount of change in the first scale factor, and wherein the step of calculating the first scale factor is based on the amount of change in the first scale factor.

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

determining a first maximum pixel brightness value for a first frame of pixels by examining individual pixel values of the first frame;

calculating a first scale factor as a function of the first maximum pixel brightness value for the first frame;

dimming backlighting of the display by the first scale factor after sending the first frame of pixels to the display;

receiving a second frame of pixels to be displayed on the display subsequent to the first frame of pixels;

calculating a second scale factor based on the first maximum pixel brightness value for the first frame; and

increasing brightness values of the pixels of the second frame of pixels by the second scale factor to generate boosted pixel values for the second frame; and

sending the boosted pixel values to the display.

7. The computer-readable storage medium of claim 6, wherein the calculating comprises applying a low pass filter to the first maximum pixel brightness value and at least one additional maximum pixel brightness value for previous frames of pixels.

8. The computer-readable storage medium of claim 7, wherein the low pass filter is applied to the additional maximum pixel brightness values of N frames, wherein N is determined based on a response time of a backlighting element.

9. The computer-readable storage medium of claim 8, further comprising determining a second maximum pixel brightness value for the second frame of pixels as the boosted pixel values of the second frame of pixels are scanned out to the display.

10. The computer-readable storage medium of claim 6, further comprising determining a second maximum pixel brightness value for the second frame of pixels as the boosted pixel values of the second frame of pixels are scanned out to the display.

18. The computer-readable storage medium of claim 6, wherein the step of increasing the brightness values of the pixels of the second frame comprises clamping the brightness values of the pixels of the second frame that are greater than the first maximum pixel brightness value.

19. The computer-readable storage medium of claim 6, further comprising monitoring an amount of change in the first scale factor, and wherein the step of calculating the first scale factor is based on the amount of change in the first scale factor.

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

a memory for storing instructions; and

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

determining a first maximum pixel brightness value for a first frame of pixels by examining individual pixel values of the first frame;

calculating a first scale factor as a function of the first maximum pixel brightness value for the first frame;

dimming backlighting of the display by the first scale factor after sending the first frame of pixels to the display;

receiving a second frame of pixels to be displayed on the display subsequent to the first frame of pixels;

calculating a second scale factor based on the first maximum pixel brightness value for the first frame; and

increasing brightness values of the pixels of the second frame of pixels by a second scale factor to generate boosted pixel values for the second frame; and

sending the boosted pixel values to the display.

12. The computing device of claim 11, wherein the calculating comprises applying a low pass filter to the first maximum pixel brightness value and at least one additional maximum pixel brightness value for previous frames of pixels.

13. The computing device of claim 12, wherein the low pass filter is applied to the additional maximum pixel brightness values of N frames, wherein N is determined based on a response time of a backlighting element.

14. The computing device of claim 13, further comprising determining a second maximum pixel brightness value for the first frame of pixels prior to increasing the brightness values of the pixels of the second frame of pixels.

15. The computing device of claim 11, further comprising determining a second maximum pixel brightness value for the second frame of pixels as the boosted pixel values of the second frame of pixels are scanned out to the display.

20. The computing device of claim 11, wherein the step of increasing the brightness values of the pixels of the second frame comprises clamping the brightness values of the pixels of the second frame that are greater than the first maximum pixel brightness value.