System and method for modulating backlight

• US 8,451,300 B2
• Filed: 12/27/2010
• Issued: 05/28/2013
• Est. Priority Date: 12/30/2009
• Status: Active Grant

• Current Assignee: Wintek Corporation
• Original Assignee: Wintek Corporation
• Inventors: Hsu, Ching-Fu, Lai, Chih-Chang
• Primary Examiner(s): Bolotin, Dmitriy
• Application Number:
  US12/979,166
• Publication Number:
  US 20110157255A1
• Time in Patent Office: 883 Days
• Field of Search: 345/55, 345 87-102, 345/204, 345/690, 382/172, 362/97.2, 362611-613
• US Class Current: 345/690
• 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 2320/0673 for control of gamma adjustment, e.g. selecting another gamma curve
• CPC Class Codes: G09G 2340/06 Colour space transformation
• CPC Class Codes: G09G 2360/16 Calculation or use of calculated indices related to luminance levels in display data
• CPC Class Codes: G09G 3/342 using several illumination sources separately controlled corresponding to different display panel areas, e.g. along one dimension such as lines
• CPC Class Codes: G09G 3/3426 the different display panel areas being distributed in two dimensions, e.g. matrix

Abstract

A backlight modulation system includes a light source module, an image mapping unit, a histogram analysis unit, a backlight dimming unit, and an image reconstruction unit. An active display area of a panel is divided into multiple illumination areas. The image mapping unit performs an RGB-to-YUV transformation to acquire an original brightness factor for each pixel. The histogram analysis unit sums up the amount of pixels reaching a preset ratio in each illumination area to acquire reference brightness for each illumination area. The backlight dimming unit calculates out a dimming ratio and a reset brightness model according to the reference brightness. The image reconstruction unit resets original brightness factor of each pixel into an output brightness factor according to the reset brightness model, and outputs an image for an illumination area according to the output brightness factor and input image data.

Claims

1. A system for modulating backlight, comprising:

a light source module providing backlight for a display panel and forming a plurality of illumination areas corresponding to a display area of the display panel, wherein the illumination areas are adjacent to each other and substantially cover the display area;

an image mapping unit performing a transformation on an image displayed on the display panel to convert a RGB color model of the image to another color model independent of an image processing device to acquire an original brightness factor for each pixel of the image;

a histogram analysis unit summing up the amount of total pixels of each illumination area and calculating the amount of accumulated pixels in each illumination area reaching a preset ratio to acquire a reference brightness for each illumination area;

a backlight dimming unit calculating a backlight dimming ratio and a mapping calibration curve of each illumination area according to the reference brightness of each illumination area, wherein the backlight dimming ratio BD(n) of the n^th illumination area satisfies the following criterion;

BD(n)=Var+[ABL_(n)/(ABL_MAX/(1−

Var))],

where Var is a variable larger than 0 and smaller than 1, ABL_(n) is the reference brightness of the n^th illumination area and ABL_MAX is the maximum reference brightness;

when the light source module comprises N_a light sources to divide the display area into (N_a+1) illumination areas, if each illumination area is distributed with N_p scan lines, the slope of the mapping calibration curve of all the N_p scan lines in the first illumination area is the inverse of the backlight dimming ratio of the first light source, the slope of the mapping calibration curve of all the N_p scan lines in the (N_a+1)^th illumination area is the inverse of the backlight dimming ratio of the N_a^th light source and the slope S(m,n) of the mapping calibration curve of the m^th scan lines in the n^th illumination area of the 2^nd to (N_a)^th illumination areas satisfies the following criterion;

2. The system according to claim 1, wherein the light source module comprises a plurality of linear light sources and the linear light sources divide the display area into the illumination areas.

3. The system according to claim 1, wherein the light source module comprises a light emitting diode array.

4. The system according to claim 1, wherein the illumination areas are arranged into an array.

5. The system according to claim 1, wherein the color model independent of an image processing device is a xyY color model, an Lab color model, or an Luv color model.

6. The system according to claim 1, wherein the amount of accumulated pixels is calculated by accumulating the amount of pixels for each individual brightness factor from the highest brightness factor toward a lower brightness factor.

7. The system according to claim 1, wherein the reference brightness is the value of an original brightness factor fetched when the amount of accumulated pixels is equal to the product of the amount of total pixels and the preset ratio or when the amount of accumulated pixels is larger than a minimum integer of the product of the amount of total pixels and the preset ratio.

8. The system according to claim 1, wherein the maximum reference brightness ABL_MAX is equal to 100.

9. The system according to claim 1, wherein the illumination area covers a plurality of pixel arrays and each pixel array corresponds to a mapping calibration curve.

10. The system according to claim 1, wherein the input image data comprises a chromatic factor for each pixel.

11. A method for modulating backlight, comprising:

forming a plurality of illumination areas corresponding to a display area of a display panel, wherein the illumination areas are adjacent to each other and substantially cover the display area;

transforming a RGB color model of an image to be displayed on the display panel into another color model independent of an image processing device to acquire an original brightness factor for each pixel;

summing up the amount of total pixels of each illumination area and calculating the amount of accumulated pixels in each illumination area reaching a preset ratio to acquire a reference brightness for each illumination area;

calculating out a backlight dimming ratio and a reset brightness model for each illumination area according to the reference brightness of each illumination area;

resetting the original brightness factor of each pixel into an output brightness factor according to the reset brightness model; and

outputting an image for the corresponding illumination area according to the output brightness factor and input image data, wherein the backlight dimming ratio BD(n) of the n^th illumination area satisfies the following criterion;

BD(n)=Var+[ABL_(n)/(ABL_MAX/(1−

Var))],

where Var is a variable larger than 0 and smaller than 1, ABL_(n) is the reference brightness of the n^th illumination area and ABL_MAX is the maximum reference brightness;

the light source module comprises N_a light sources to divide the display area into (N_a+1) illumination areas, if each illumination area is distributed with N_p scan lines, the slope of the mapping calibration curve of all the N_p scan lines in the first illumination area is the inverse of the backlight dimming ratio of the first light source, the slope of the mapping calibration curve of all the N_p scan lines in the (N₂+1)^th illumination area is the inverse of the backlight dimming ratio of the N_a^th light source and the slope S(m,n) of the mapping calibration curve of the m^th scan lines in the n^th illumination area of the 2^nd to (N_a)^th illumination areas satisfies the following criterion;

12. The method according to claim 11, wherein the illumination area covers a plurality of pixel arrays and each pixel array corresponds to a mapping calibration curve.

13. The method according to claim 11, wherein the color model independent of an image processing device is a xyY color model, an Lab color model, or an Luv color model.

14. The method according to claim 11, wherein the amount of accumulated pixels is calculated by accumulating the amount of pixels for each individual brightness factor from the highest brightness factor toward a lower brightness factor.

15. The method according to claim 11, wherein the reference brightness is the value of an original brightness factor fetched when the amount of accumulated pixels is equal to the product of the amount of total pixels and the preset ratio or when the amount of accumulated pixels is larger than a minimum integer of the product of the amount of total pixels and the preset ratio.

16. The method according to claim 11, wherein the input image data comprises a chromatic factor for each pixel.