Method and apparatus for driving liquid crystal display

• US 20050104827A1
• Filed: 06/28/2004
• Published: 05/19/2005
• Est. Priority Date: 11/13/2003
• Status: Active Grant

• Current Assignee: LG Display Co., Ltd.
• Original Assignee: LG Philips LCD Company Limited (LG Display Co., Ltd.)
• Inventors: Baik, Seong Ho
• Granted Patent: US 7,522,135 B2
• Time in Patent Office: Days
• US Class Current: 345/87
• CPC Class Codes: G09G 2320/02 Improving the quality of display appearance
• CPC Class Codes: G09G 2320/0686 with two or more screen areas displaying information with different brightness or colours
• CPC Class Codes: G09G 2360/16 Calculation or use of calculated indices related to luminance levels in display data
• CPC Class Codes: G09G 3/2011 by amplitude modulation
• CPC Class Codes: G09G 3/3648 using an active matrix G09G3/367 - G09G3/3696 take precedence

Abstract

A driving method and apparatus for a liquid crystal display capable of selectively emphasizing a contrast is disclosed. In the apparatus, an image signal modulator partially expands or reduces the contrast of input data to generate output data. The brightness components for one frame are divided into a plurality of areas and an area having a large brightness difference is removed from each area to thereby produce new data. Gray levels of the new data are divided into a plurality of regions of different slopes. The range of output gray levels is enlarged in proportion to the slopes, thereby partially emphasizing the contrast ratio. A timing controller re-arranges the output data to apply it to a data driver.

Claims

1. A driving apparatus for a liquid crystal display, comprising:

image signal modulating means for partially expanding or reducing contrast of input data to generate output data; and

a timing controller for re-arranging the output data to apply the output data to a data driver.

2. The driving apparatus of claim 1, further comprising control means for changing a synchronizing signal inputted in synchronization with the input data to be synchronized with the output data.

3. The driving apparatus of claim 1, wherein the image signal modulating means includes:

a brightness/color separator for converting the input data into brightness components and chrominance components;

an entire area statistics part for dividing the brightness components for one frame into gray levels of the frame to generate an entire histogram;

a partial area statistics part for dividing the brightness components one of the frame into i areas (wherein i is an integer) and for generating i partial histograms using brightness components in each divided area;

an effective selector for comparing partial average values of the partial histograms with an entire average value of the entire histogram to select at least two effective areas of the i areas;

a brightness distribution calculator for summing partial histograms in the effective area to generate a new histogram; and

a data processor for generating modulated brightness components having a partially expanded and reduced contrast using the new histogram.

4. The driving apparatus of claim 3, wherein the entire histogram, the partial histograms and the new histogram are divided into a plurality of regions each including a desired gray level.

5. The driving apparatus of claim 3, wherein the partial area statistics part includes:

an area selector for dividing the brightness components one of the frame into i areas; and

i area statistics parts for generating i partial histograms using the brightness components from the area selector.

6. The driving apparatus of claim 4, wherein the effective area selector selects an area of the i areas in which the partial average value exists within a desired deviation from the entire average value as an effective area.

7. The driving apparatus of claim 6, wherein the effective area selector includes:

i comparators for comparing the entire average value with i partial average values;

i multiplexers for outputting a first control signal or a second control signal under control of the comparators; and

storage means for temporarily storing outputs of the multiplexers, wherein

the comparators control the multiplexers to output the first control signal when the entire average value and the partial average values exist within the desired deviation.

8. The driving apparatus of claim 7, wherein the brightness distribution calculator sums histograms in areas to which the first control signal corresponds to thereby generate the new histogram.

9. The driving apparatus of claim 8, further comprising a region slope calculator for assigning a slope for each region having a new histogram divided into the plurality of regions.

10. The driving apparatus of claim 9, wherein the region slope calculator assigns the slope to be in proportion to brightness components in which each region is included.

11. The driving apparatus of claim 10, wherein the data processor expands or reduces the gray levels of the brightness components included in each region to be in proportion to the slope to thereby generate modulated brightness components.

12. The driving apparatus of claim 11, further comprising a brightness/color mixer for generating the output data using the modulated brightness components and the chrominance components.

13. The driving apparatus of claim 12, further comprising delay means for delaying the chrominance components until the modulated brightness components are produced.

14. The driving apparatus of claim 12, wherein the data processor includes:

a contrast ratio emphasizer for generating the modulated brightness components; and

a contrast ratio compensator for applying the modulated brightness components to the brightness/color mixer when an average value of the modulated brightness components generated from the contrast ratio emphasizer and the entire average value exist within a predetermined deviation.

15. The driving apparatus of claim 14, wherein the contrast ratio compensator subtracts or adds a desired value from or to the modulated brightness components when an average value of the modulated brightness components and the entire average value does not exist within the predetermined deviation, thereby compensating brightness having the modulated brightness components to be analogous to brightness of the entire histogram.

16. The driving apparatus of claim 14, further comprising an inverter controller for controlling brightness of a back light when an average value of the modulated brightness components and the entire average value are not within the predetermined deviation to compensate for brightness having the modulated brightness components.

17. A method of driving a liquid crystal display, the method comprising:

partially expanding or reducing contrast of input data to generate output data; and

re-arranging the output data to apply the output data to a data driver.

18. The method of claim 17, further comprising changing a synchronizing signal inputted in synchronization with the input data to be synchronized with the output data.

19. The method of claim 17, wherein generating the output data includes:

converting the input data into brightness components and chrominance components;

dividing brightness components for one frame into gray levels to generate an entire histogram;

dividing the brightness components into i areas (wherein i is an integer) and generating i partial histograms using the brightness components in each divided area;

comparing partial average values of the partial histograms with an entire average value of the entire histogram to select at least two effective areas of the i areas;

summing the partial histograms in each effective area to generate a new histogram; and

generating modulated brightness components having a partially expanded and reduced contrast using the new histogram.

20. The method of claim 19, wherein the entire histogram, the partial histograms and the new histogram are divided into a plurality of regions each including a desired gray level.

21. The method of claim 20, further comprising selecting an area in which the partial average value is within a desired deviation from the entire average value as one of the effective areas.

22. The method of claim 21, wherein generating the modulated brightness components comprises:

assigning a slope for each region of the new histogram divided into the plurality of regions; and

expanding or reducing gray levels of the brightness components of each region to be in proportion to the slope in the region.

23. The method of claim 22, wherein the slope of each region is proportional to the brightness components of the region.

24. The method of claim 22, further comprising:

delaying the chrominance components until the modulated brightness components are produced; and

generating the output data using the modulated brightness components and the chrominance components.

25. The method of claim 22, wherein generating the modulated brightness components further comprises subtracting or adding a desired value from or to the modulated brightness components when an average value of the modulated brightness components and the entire average value are not within a predetermined deviation, thereby compensating for brightness having the modulated brightness components analogous to brightness of the entire histogram.

26. The method of claim 22, further comprising controlling brightness of a back light such that brightness of the modulated brightness components is analogous to brightness of the entire histogram when an average value of the modulated brightness components and the entire average value are not within a desired deviation.

27. A method of driving a liquid crystal display, the method comprising:

separating an entire area of the liquid crystal display into a plurality of individual areas;

extracting brightness components of one frame from input data to be supplied to the liquid crystal display for the entire area and for the individual areas;

determining an average of the brightness components in the entire area and averages of the brightness components in the individual areas;

comparing the average values of the individual areas with the average value of the entire area;

modifying the brightness components of the individual areas differently dependent on whether or not the averages of the brightness components in the individual areas are within a predetermined deviation from the average of the brightness components in the entire area to produce modulated brightness components;

generating output data using the modulated brightness components instead of the brightness components; and

supplying the output data to the liquid crystal display.

28. The method of claim 27, further comprising eliminating, from generating the output data, the brightness components of the individual areas in which the averages of the brightness components are not within the predetermined deviation from the average of the brightness components in the entire area.

29. The method of claim 27, further comprising reducing contrast in the frame using the modulated brightness components from the contrast in the frame that would be displayed using the brightness components.

30. The method of claim 27, further comprising extracting chrominance components from the input data along with the brightness components.

31. The method of claim 30, further comprising delaying the chrominance components until the modulated brightness components are produced.

32. The method of claim 31, further comprising generating the output data using the chrominance components.

33. The method of claim 27, further comprising adjusting the modulated brightness components by a desired value when an average value of the modulated brightness components and the average value of the entire area are not within a predetermined deviation prior to generating the output data from the modulated brightness components.

34. The method of claim 33, further comprising adding or subtracting a predetermined value to the modulated brightness components to compensate for brightness having the modulated brightness components analogous to brightness of the entire area.

35. The method of claim 27, further comprising controlling brightness of a back light such that brightness of the modulated brightness components is analogous to brightness of the entire area when an average value of the modulated brightness components and the average value of the entire area are not within a predetermined deviation.

36. The method of claim 27, further comprising creating histograms of the brightness components and the modulated brightness components to aid in modification of the brightness components and the modulated brightness components.

37. The method of claim 27, further comprising generating an output gray level related to an input gray level such that brightness of the input gray level is diffused proportional to the brightness of the input gray level.

38. The method of claim 27, further comprising decreasing contrast differences in the frame by using the modulated brightness components.

39. The method of claim 27, further comprising generating histograms of the brightness components and statistically adjusting the histograms during generation of the modulated brightness components.