Adaptive backlight control and contrast enhancement

Patent metadata

Field	Value
Publication number	US-9230484-B2
Application number	US-20325408-A
Country	US
Kind code	B2
Filing date	Sep 3, 2008
Priority date	Sep 3, 2008
Publication date	Jan 5, 2016
Grant date	Jan 5, 2016

Abstract

A transform function represented by at least n points that define n−1 regions is determined based at least in part on a first set of values associated with a display frame and a maximum average contrast function. The n points can be determined in response to a change in an average contrast of the display frame compared to an average contrast of a previous display frame exceeding a predetermined threshold. The first set of values is converted to a corresponding second set of values based on the transform function. A backlight control signal is generated based on an average contrast of the second set of values, whereby the backlight control signal is configured to control an intensity of a backlight of a display. Further, a video signal is generated based on the second set of values, whereby the video signal configured to drive the display.

First claim

What is claimed is:

1. A method comprising:
determining n points that define n−1 regions of a first transform function based at least in part on a first set of values associated with a first display frame and a maximum average contrast function, n being an integer greater than 2;
converting the first set of values to a corresponding second set of values based on the first transform function; and
generating a backlight control signal based on an average contrast of the second set of values, the backlight control signal configured to control an intensity of a backlight of a display.

2. The method of claim 1 , further comprising:
generating a video signal based on the second set of values, the video signal configured to drive a display.

3. The method of claim 1 , wherein determining the n points that define the n−1 regions of the first transform function comprises determining the n points in response to a change in an average contrast of the first display frame compared to an average contrast of a previous display frame exceeding a predetermined threshold.

4. The method of claim 1 , further comprising:
generating the first set of values based on a third set of values associated with the display frame, the first set of values having a first color space and the third set of values having a second color space.

5. The method of claim 4 , wherein:
the first color space comprises a Hue-Saturation-Value (HSV) color space and the second color space comprises a Red-Green-Blue (RGB) color space; and
the first set of values comprises value (V) values in the HSV color space.

6. The method of claim 1 , wherein generating the backlight control signal comprises generating the backlight control signal to gradually adjust the intensity of the backlight over one of a predetermined duration or a predetermined number of display frames.

7. The method of claim 1 , wherein determining the n points of the first transform function comprises:
determining an initial point of the n points based on the darkest value of the first set of values; and
determining a final point of the n points based on a saturation criterion.

8. The method of claim 7 , wherein determining the n points of the first transform further comprises:
determining a first intermediate point and a second intermediate point of the n points of the first transform function based on the initial point, the final point, and an iterative application of the maximum average contrast function.

9. The method of claim 8 , wherein determining the first intermediate point and the second intermediate point comprises:
determining the first intermediate point and the second intermediate point based on one or more iterative applications of the maximum average contrast function until each of one or more predefined criteria are met based on the resulting first intermediate point and the second intermediate point.

10. The method of claim 9 , wherein the one or more predefined criteria includes at least one selected from a group consisting of: a criterion that is met when a slope of a segment of the first transform function defined by the first point and the first intermediate point is the greatest slope of the first transform function; and a criterion that is met when a ratio of populations of values in each region is not greater than a ratio of slopes of segments of the first transform function defined by the n points.

11. A system comprising:
a hardware mapping module comprising:
a point generation module configured to determine n points that define n−1 regions of a first transform function based at least in part on a first set of values associated with a first display frame and a maximum average contrast function, n being an integer greater than two;
a conversion module configured to convert the first set of values to a second set of values based on the first transform; and
an intensity control module configured to generate a backlight control signal based on an average contrast of the second set of values, the backlight control signal configured to control an intensity of a backlight of a display.

12. The system of claim 11 , further comprising:
a backlight controller configured to operate the backlight of the display based on the backlight of control signal.

13. The system of claim 11 , wherein the point generation module is configured to determine the n points of the first transform function by:
determining an initial point of the n points based on the darkest value of the first set of values; and
determining a final point of the n points based on a saturation criterion.

14. The system of claim 13 , wherein the point generation module is configured to determine the n points of the first transform by determining a first intermediate point and a second intermediate point of the n points of the first transform function based on an iterative application of the maximum average contrast function using the initial point and the final point.

15. The system of claim 14 , wherein the point generation module is configured to determine the first intermediate point and the second intermediate point based on one or more iterative applications of the maximum average contrast function until each of one or more predefined criteria are met based on the resulting first intermediate point and the second intermediate point.

16. The system of claim 15 , wherein the one or more predefined criteria comprises at least one selected from a group consisting of: a criterion that is met when a slope of a segment of the first transform function defined by the first point and the first intermediate point is the greatest slope of the first transform function; and a criterion that is met when a ratio of populations of values in each region is not greater than a ratio of slopes of segments of the first transform function defined by the n points.

17. A computer readable memory storing data representative of a set of instructions, the set of instructions configured to manipulate one or more processors to:
determine n points that define n−1 regions of a first transform function based at least in part on a first set of values associated with a first display frame and a maximum average contrast function, n being an integer greater than two;
convert the first set of values to a second set of values based on the first transform; and
generate a backlight control signal based on an average contrast of the second set of values, the backlight control signal configured to control an intensity of a backlight of a display.

18. The computer readable memory of claim 17 , wherein the set of instructions is configured to manipulate the one or more processors to determine the n points of the first transform function by manipulating the one or more processors to:
determine an initial point of the n points based on the darkest value of the first set of values; and
determine a final point of the n points based on a saturation criterion.

19. The computer readable memory of claim 17 , wherein the set of instructions is configured to manipulate the one or more processors to determine the n points of the first transform function by manipulating the one or more processors to:
determine a first intermediate point and a second intermediate point of the n points of the first transform function based on an iterative application of the maximum average contrast function using the initial point and the final point.

20. The computer readable memory of claim 17 , wherein the set of instructions comprises register transfer level (RTL

Assignees

• Leung Charles
• Naik Jatin
• Lim Lawrence
• Dahan Laurent
• Aleksic Milivoje
• Ati Technologies Ulc

Inventors

• Leung Charles
• Naik Jatin
• Lim Lawrence
• Dahan Laurent
• Aleksic Milivoje

Classifications

• G09G2360/16

  Calculation or use of calculated indices related to luminance levels in display data · CPC title

• G09G3/3406 Primary

  Control of illumination source (illumination devices structurally associated with liquid crystal cells G02F1/1336) · CPC title

• G09G2320/064

  by time modulation of the brightness of the illumination source · CPC title