Method and apparatus for driving liquid crystal display device

• US 20050140631A1
• Filed: 12/28/2004
• Published: 06/30/2005
• Est. Priority Date: 12/29/2003
• Status: Active Grant

• Current Assignee: LG Display Co., Ltd.
• Original Assignee: LG Philips LCD Company Limited (LG Display Co., Ltd.)
• Inventors: Baik, Seong Ho, Kim, Ki Duk, Oh, Eui Yeol, Sohn, Min Ho
• Granted Patent: US 7,782,281 B2
• Time in Patent Office: Days
• US Class Current: 345/89
• CPC Class Codes: G09G 2320/02 Improving the quality of display appearance
• CPC Class Codes: G09G 2320/0261 in the context of movement of objects on the screen or movement of the observer relative to the screen
• CPC Class Codes: G09G 2320/062 Adjustment of illumination source parameters
• CPC Class Codes: G09G 2320/106 Determination of movement vectors or equivalent parameters within the image
• 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 3/3611 Control of matrices with row and column drivers

Abstract

A method of driving a liquid crystal display device includes extracting brightness components of a portion of the first data for a current frame, arranging the brightness components for the current frame into a brightness histogram, retrieving brightness histograms for at least two frames prior to the current frame to generate an average histogram, generating second data for the current frame based on the average histogram, comparing the histogram for the current frame with the average histogram to determine whether an image at the current frame is a moving image or a still image, and driving the liquid crystal display device in accordance with one of the first data and the second data based on the comparison result.

Claims

1. A method of driving a liquid crystal display device, comprising steps of:

retrieving brightness histograms for at least two frames prior to a current frame to generate an average histogram;

generating modulated brightness components based on the average histogram; and

modulating first data for the current frame based on the modulated brightness components to generate second data for the current frame.

2. The method according to claim 1, further comprising assigning weighting values to the brightness histograms.

3. The method according to claim 1, further comprising controlling a back light to generate light having various degrees of brightness based on the average histogram.

4. The method according to claim 1, wherein the step of generating the average histogram includes:

storing the histograms for at least two frames that are immediately prior to the current frame;

assigning weighting values to the stored histograms; and

converting the histograms assigned with the weighting values into average values to produce the average histogram.

5. The method according to claim 4, wherein a higher value of the weighting values is assigned to the histogram for the frame closer to the current frame.

6. The method according to claim 1, further comprising:

extracting brightness components of the first data for the current frame;

arranging the brightness components for the current frame into a brightness histogram; and

storing the brightness histogram.

7. The method according to claim 6, further comprising:

comparing the histogram for the current frame with the average histogram to determine whether an image at the current frame is a moving image or a still image; and

driving the liquid crystal display device in accordance with one of the first data and the second data based on the comparison result.

8. The method according to claim 7, wherein the step of generating the average histogram includes:

storing the histograms for at least two frames that are immediately prior to the current frame;

assigning weighting values to the stored histograms; and

converting the histograms assigned with the weighting values into average values to produce the average histogram.

9. The method according to claim 8, wherein a higher value of the weighting values is assigned to the histogram for the frame closer to the current frame.

10. The method according to claim 7, wherein the step of comparing the histograms includes:

extracting a first image discriminating factor from the histogram for the current frame;

extracting a second image discriminating factor from the average histogram; and

comparing the first image discriminating factor with the second image discriminating factor to discriminate whether an image at the current frame is a moving image or a still image.

11. The method according to claim 10, wherein the first image discriminating factor includes an average gray level value of the histogram for the current frame, a most-frequent gray level value of the histogram for the current frame, a center value positioned at the center when the gray level values of the histogram for the current frame are arranged in accordance with the frequency number, a maximum gray level value of the histogram for the current frame, a minimum gray level value of the histogram for the current frame, a gray level range value of the histogram for the current frame, and an intermediate gray level value of the histogram for the current frame.

12. The method according to claim 11, further comprising the steps of:

assigning a high weighting value for the average gray level value and the most-frequent gray level value;

assigning a middle weighting value for the gray level range value;

assigning a low weighting value for the minimum gray level value, the maximum gray level value, the center value and the intermediate gray level value; and

generating the first discriminating factor based on the weighted average gray level value, the weighted most-frequent gray level value, the weighted gray level range value, the weighted minimum gray level value, the weighted maximum gray level value, the weighted center value and the weighted intermediate gray level value.

13. The method according to claim 10, wherein the second image discriminating factor includes an average gray level value of the average histogram, a most-frequent gray level value of the average histogram, a center value positioned at the center when the gray level values of the average histogram are arranged in accordance with the frequency number, a maximum gray level value of the average histogram, a minimum gray level value of the average histogram, a gray level range value of the average histogram, and an intermediate gray level value of the average histogram.

14. The method according to claim 13, further comprising the steps of:

assigning a high weighting value for the average gray level value and the most-frequent gray level value;

assigning a middle weighting value for the gray level range value;

assigning a low weighting value for the minimum gray level value, the maximum gray level value, the center value and the intermediate gray level value; and

generating the second discriminating factor based on the weighted average gray level value, the weighted most-frequent gray level value, the weighted gray level range value, the weighted minimum gray level value, the weighted maximum gray level value, the weighted center value and the weighted intermediate gray level value.

15. The method according to claim 10, wherein the image at the current frame is discriminated as a still image when the first and second discriminating factors fall within a predetermined range, and the image at the current frame is discriminated as a moving image when the first and second discriminating factors fall outside the predetermined range.

16. The method according to claim 10, further comprising the steps of:

controlling a back light to generate light of various degrees of brightness based on the second discriminating factor when the image at the current frame is discriminated as a moving image; and

controlling the back light to generate light of a predetermined brightness when the image at the current frame is discriminated as a still image.

17. The method according to claim 7, wherein the liquid crystal display device is driven based on the first data when the image at the current frame is discriminated as a still image.

18. The method according to claim 7, wherein the liquid crystal display device is driven based on the second data when the image at the current frame is discriminated as a moving image.

19. The method according to claim 7, further comprising controlling a back light to generate light of various degrees of brightness when the image at the current frame is discriminated as a moving image.

20. The method according to claim 7, further comprising the steps of:

receiving a first vertical synchronizing signal, a first horizontal synchronizing signal, a first clock signal and a first data enable signal from an exterior source; and

generating a second vertical synchronizing signal, a second horizontal synchronizing signal, a second clock signal and a second data enable signal in synchronization with the first data or the second data in response to the comparison result.

21. A method of driving a liquid crystal display device, comprising:

extracting brightness components of a portion of the first data for a current frame;

arranging the brightness components for the current frame into a brightness histogram;

retrieving brightness histograms for at least two frames prior to the current frame to generate an average histogram;

generating second data for the current frame based on the average histogram;

comparing the histogram for the current frame with the average histogram to determine whether an image at the current frame is a moving image or a still image; and

driving the liquid crystal display device in accordance with one of the first data and the second data based on the comparison result.

22. The method according to claim 21, wherein the portion of the first data corresponds to image data for a center display area of a liquid crystal display panel.

23. The method according to claim 21, wherein the step of generating the average histogram includes:

storing the histograms for at least two frames that are immediately prior to the current frame;

assigning weighting values to the stored histograms; and

converting the histograms assigned with the weighting values into average values to produce the average histogram.

24. The method according to claim 23, wherein a higher value of the weighting values is assigned to the histogram for the frame closer to the current frame.

25. The method according to claim 21, wherein the step of comparing the histograms includes:

extracting a first image discriminating factor from the histogram for the current frame;

extracting a second image discriminating factor from the average histogram; and

comparing the first image discriminating factor with the second image discriminating factor to discriminate whether an image at the current frame is a moving image or a still image.

26. The method according to claim 25, wherein the first image discriminating factor includes an average gray level value of the histogram for the current frame, a most-frequent gray level value of the histogram for the current frame, a center value positioned at the center when the gray level values of the histogram for the current frame are arranged in accordance with the frequency number, a maximum gray level value of the histogram for the current frame, a minimum gray level value of the histogram for the current frame, a gray level range value of the histogram for the current frame, and an intermediate gray level value of the histogram for the current frame.

27. The method according to claim 26, further comprising the steps of:

assigning a high weighting value for the average gray level value and the most-frequent gray level value;

assigning a middle weighting value for the gray level range value;

assigning a low weighting value for the minimum gray level value, the maximum gray level value, the center value and the intermediate gray level value; and

generating the first discriminating factor based on the weighted average gray level value, the weighted most-frequent gray level value, the weighted gray level range value, the weighted minimum gray level value, the weighted maximum gray level value, the weighted center value and the weighted intermediate gray level value.

28. The method according to claim 25, wherein the second image discriminating factor includes an average gray level value of the average histogram, a most-frequent gray level value of the average histogram, a center value positioned at the center when the gray level values of the average histogram are arranged in accordance with the frequency number, a maximum gray level value of the average histogram, a minimum gray level value of the average histogram, a gray level range value of the average histogram, and an intermediate gray level value of the average histogram.

29. The method according to claim 28, further comprising the steps of:

assigning a high weighting value for the average gray level value and the most-frequent gray level value;

assigning a middle weighting value for the gray level range value;

assigning a low weighting value for the minimum gray level value, the maximum gray level value, the center value and the intermediate gray level value; and

generating the second discriminating factor based on the weighted average gray level value, the weighted most-frequent gray level value, the weighted gray level range value, the weighted minimum gray level value, the weighted maximum gray level value, the weighted center value and the weighted intermediate gray level value.

30. The method according to claim 25, wherein the image at the current frame is discriminated as a still image when the first and second discriminating factors fall within a predetermined range, and the image at the current frame is discriminated as a moving image when the first and second discriminating factors fall outside the predetermined range.

31. The method according to claim 25, further comprising the steps of:

controlling a back light to generate light of various degrees of brightness based on the second discriminating factor when the image at the current frame is discriminated as a moving image; and

controlling the back light to generate light of a predetermined brightness when the image at the current frame is discriminated as a still image.

32. The method according to claim 21, wherein the liquid crystal display device is driven based on the first data when the image at the current frame is discriminated as a still image and the liquid crystal display device is driven based on the second data when the image at the current frame is discriminated as a moving image.

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

an image signal modulator receiving first data for a current frame, retrieving brightness histograms for at least two frames prior to the current frame to generate an average histogram, and generating second data for the current frame based on the average histogram; and

a back light controller generating a brightness control signal based on the average histogram.

34. The driving apparatus according to claim 33, wherein the image signal modulating means includes:

a brightness/color separator separating the first data for the current frame into brightness components and chrominance components;

a histogram analyzer converting the brightness components into a histogram;

a storage storing histograms for at least two frames analyzed by the histogram analyzer;

an average value calculator generating the average histogram based on the histograms for the at least two frames stored in the storage;

a data processor modulating the brightness components extracted from the brightness/color separator using said average histogram; and

a brightness/color mixer for generating the second data based on the modulated brightness components and the chrominance components.

35. The driving apparatus according to claim 34, further comprising a weighting value assigner assigning a weighting value to each of the histograms.

36. The driving apparatus according to claim 33, further comprising:

an image discriminator discriminating whether an image at the current frame is a moving image or a still image; and

a selector receiving the first data and the second data and selectively outputting one of the first data and the second data based on the discrimination result.

37. The driving apparatus according to claim 36, wherein the image signal modulating means includes:

a brightness/color separator separating the first data for the current frame into brightness components and chrominance components;

a histogram analyzer converting the brightness components into a histogram;

a storage storing histograms for at least two frames analyzed by the histogram analyzer;

an average value calculator generating the average histogram based on the histograms for the at least two frames stored in the storage;

a data processor modulating the brightness components extracted from the brightness/color separator using said average histogram; and

a brightness/color mixer for generating the second data based on the modulated brightness components and the chrominance components.

38. The driving apparatus according to claim 37, wherein the image discriminator includes:

a first image discriminating factor detector extracting a first image discriminating factor based on the histogram from the histogram analyzer; and

a second image discriminating factor detector extracting a second image discriminating factor from the average histogram.

39. The driving apparatus according to claim 38, wherein the first and second image discriminating factors respectively include an average gray level value, a most-frequent gray level value, a center gray level value, a maximum gray level value, a minimum gray level value, a gray level range value and an intermediate gray level value.

40. The driving apparatus according to claim 39, further comprising a weighting value assigner for assigning a weighting value to the first image discriminating factor and the second image discriminating factor.

41. The driving apparatus according to claim 40, wherein the weighting value assigner assigns a high weighting value for the average gray level value and the most-frequent gray level value;

assigns a middle weighting value for the gray level range value; and

assigns a low weighting value for the minimum gray level value, the maximum gray level value, the center value and the intermediate gray level value.

42. The driving apparatus according to claim 41, wherein the image discriminator further includes:

a comparator generating a first control signal when the first and second discriminating factors fall within a predetermined range and generating a second control signal when the first and second discriminating factors fall outside of the predetermined range.

43. The driving apparatus according to claim 42, wherein the selector outputs the first data when the first control signal is applied thereto and outputs the second data when the second control signal is applied thereto.

44. The driving apparatus according to claim 42, wherein the back light controller generates the brightness control signal based on the second discriminating factor when the second control signal is applied thereto, and generates the brightness control signal based on a predetermined brightness when the first control signal is applied thereto.

45. The driving apparatus according to claim 36, further comprising an image area selector extracting a portion of the brightness components for the first data for a current frame to be inputted to the histogram analyzer.

46. The driving apparatus according to claim 45, wherein the portion of the brightness components for the first data corresponds to image data for a center display area of a liquid crystal display panel.

47. The driving apparatus according to claim 45, wherein the image discriminator includes:

a first image discriminating factor detector extracting a first image discriminating factor based on the histogram from the histogram analyzer; and

a second image discriminating factor detector extracting a second image discriminating factor from the average histogram.

48. The driving apparatus according to claim 47, wherein the back light controller generates the brightness control signal based on the second discriminating factor when the first and second discriminating factors fall outside of a predetermined range, and generates the brightness control signal based on a predetermined brightness when the first and second discriminating factors fall within the predetermined range.

49. The driving apparatus according to claim 47, wherein the selector outputs the first data when the first and second discriminating factors fall within a predetermined range, and outputs the second data when the first and second discriminating factors fall outside of the predetermined range.