Image display and method for displaying image

• US 20020140691A1
• Filed: 02/07/2002
• Published: 10/03/2002
• Est. Priority Date: 06/08/2000
• Status: Active Grant

• Current Assignee: Godo Kaisha IP Bridge 1 (IP Bridge, Inc.)
• Original Assignee: Matsushita Electric Industrial Company Limited (Panasonic Holdings Corporation)
• Inventors: Sato, Ichiro, Inoue, Kazuo, Kumagawa, Katsuhiko, Arimoto, Katsuyuki, Funamoto, Taro, Machidori, Wataru
• Granted Patent: US 7,173,609 B2
• Time in Patent Office: Days
• US Class Current: 345/212
• CPC Class Codes: G02F 1/134363 for applying an electric field parallel to the substrate, i.e. in-plane switching [IPS]
• CPC Class Codes: G02F 1/1368 in which the switching element is a three-electrode device G02F1/136277 takes precedence
• CPC Class Codes: G02F 2202/42 Materials having a particular dielectric constant
• CPC Class Codes: G09G 2300/0434 Flat panel display in which a field is applied parallel to the display plane
• CPC Class Codes: G09G 2320/02 Improving the quality of display appearance
• CPC Class Codes: G09G 2320/0257 Reduction of after-image effects
• 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 2340/16 Determination of a pixel data signal depending on the signal applied in the previous frame
• CPC Class Codes: G09G 3/3611 Control of matrices with row and column drivers

Abstract

At the time when displaying moving images using liquid crystal panels and others, there is such a problem that tail streaks occur, and resultantly image degradation is caused. In order to solve this problem, an echo suppression circuit 100 divides a video signal into a pair composed of two successive frames for comparison between these two frames in signal level for the purpose of suppressing an echo phenomenon occurring when a liquid crystal panel 108 displays video signals including moving images. If these two frames are not the same in signal level, the signal is accordingly so corrected as to equalize the signal level of those. Based on the video signals and others corrected by the echo suppression circuit 100, a controller 102 operates the liquid crystal panel with Alternating-Current drive through a source driver 104 and a gate driver 106. As such, the drive voltage used to operate the liquid crystal panel with AC drive is so adjusted as to be balanced between positive and negative. In this manner, the tail streaks are prevented when displaying moving images.

Claims

1. An image display apparatus for displaying an image based on an input video signal, comprising:

a display device for outputting image lights according to a voltage to be applied;

drive means for driving said display device by switching the drive voltage between positive and negative for application based on said input video signal; and

means for suppressing a polarization phenomenon in said display device.

2. The image display apparatus according to claim 1, wherein

said means for suppressing the polarization phenomenon is adjustment means for adjusting said drive voltage by correcting said input video signal or said drive voltage so that absolute values of said drive voltage between positive and negative become closer in at least any two successive frames.

3. The image display apparatus according to claim 2, wherein

when an absolute value of the drive voltage in an n-th frame of a signal being normal to said input video signal is different from an absolute value of the drive voltage in an n+1-th frame or in an n−

1-th frame, said adjustment means adjusts the drive voltage of any one of the n+1-th frame, the n−

1-th frame, or the n-th frame.

4. The image display apparatus according to claim 3, wherein

said adjustment means adjusts both of said n+1-th frame and said n−

1-th frame.

5. The image display apparatus according to claim 3, wherein

when adjusting said drive voltage, said adjustment means holds a maximum value or a minimum value.

6. The image display apparatus according to claim 3, wherein

when adjusting said drive voltage, said adjusting means holds a sum of the absolute values or a square sum of the absolute values of said n+1-th frame, said n−

1-th frame, and said n-th frame.

7. The image display apparatus according to claim 2, wherein

in the two successive frames the polarity of the drive voltage applied thereto is different from each other, said adjustment means adjusts said drive voltage to make a difference of the absolute values of the drive voltage to be ½

of a maximum drive voltage or smaller.

8. The image display apparatus according to claim 7, wherein

said adjustment means adjusts said drive voltage to make said difference of the absolute values of the drive voltage to be {fraction (1/10)} of the maximum drive voltage or smaller.

9. The image display apparatus according to claim 8, wherein

said adjustment means adjusts said drive voltage when, prior to adjustment, said difference of the absolute values of the drive voltage is exceeding {fraction (1/10)} of the maximum drive voltage.

10. The image display apparatus according to claim 1, wherein

said drive means divides one vertical scanning period of said input video signal into a first sub period and a second sub period, and the drive voltage applied to the sub periods is different in polarity.

11. The image display apparatus according to claim 10, wherein

said drive means outputs the same video signal in said first sub period and said second sub period.

12. The image display apparatus according to claim 10, wherein

said first sub period and said second sub period are the same in length.

13. The image display apparatus according to claim 10, wherein

said first sub period and said second sub period are not the same in length.

14. The image display apparatus according to claim 10, wherein

said drive means includes division means f or dividing said one vertical scanning period of said input video signal into said first sub period and said second sub period.

15. The image display apparatus according to claim 14, wherein

said division means includes means f or temporarily storing said input video signal.

16. The image display apparatus according to claim 14, wherein

said division means includes means for delaying said input video signal by a length of time equal to or shorter than the one vertical scanning period.

17. The image display apparatus according to claim 14, further comprising conversion means for converting said input video signal into a data display signal for driving said display device, wherein

in a process for converting said input video signal into said data display signal, said conversion means divides said one vertical scanning period of said input video signal into said first sub period and said second sub period.

18. The image display apparatus according to claim 1, wherein

said drive means divides one vertical scanning period of said input video signal into a first sub period and a second sub period, and outputs said input video signal in said first sub period, and outputs a comparison signal in said second sub period.

19. The image display apparatus according to claim 18, wherein

said second sub period is shorter than said f irst sub period.

20. The image display apparatus according to claim 18, wherein

the drive voltage in said second sub period is a voltage of a pedestal level or lower when said display device is a normally black type, and when said display device is a normally white type, a voltage of the pedestal level or higher.

21. The image display apparatus according to claim 20, wherein

said display device is a normally black type, and said drive voltage in said second sub period is 0V.

22. The image display apparatus according to claim 18, wherein

said drive voltage in said second sub period is applied to a plurality of scanning lines at one time.

23. The image display apparatus according to claim 1, wherein

said drive means

scans, in an n-th frame, odd-numbered scanning lines for a data signal, and even-numbered scanning lines for a compensation signal, and

scans, in an n+1-th frame, the odd-numbered scanning lines for the compensation signal, and the even-numbered lines for the data signal.

24. The image display apparatus according to claim 1, wherein

during one vertical scanning period of said input video signal, after sequentially scanning either ones of odd-numbered scanning lines and even-numbered scanning lines, said drive means sequentially scans the scanning lines.

25. The image display apparatus according to claim 1, wherein

said drive means applies the drive voltage of the same polarity without polarity reverse to at least any two successive frames.

26. The image display apparatus according to claim 25, wherein

said drive means applies such a drive voltage as alternating the polarity for every two frames.

27. The image display apparatus according to claim 25, wherein

said drive means applies the drive voltage of the same polarity between any two successive frames once for every n frames.

28. The image display apparatus according to claim 1, wherein

said display device includes:

liquid crystal; and

an orientation film, and

a combination of said liquid crystal and said orientation film is a combination to make a voltage holding ratio 98% or higher.

29. The image display apparatus according to claim 1, wherein

said display device includes:

liquid crystal; and

an orientation film, and

as said means for suppressing the polarity phenomenon, said liquid crystal includes 1 wt % or less of a CN compound, and said orientation film does not include a high polymer whose conjugated length is seven atoms or more.

30. The image display apparatus according to claim 1, wherein

said display device includes:

liquid crystal;

an orientation film; and

a pixel electrode and a common electrode for applying the voltage to said liquid crystal, and

at least a part of said pixel electrode and said common electrode applies the voltage to said liquid crystal only via said orientation film.

31. The image display apparatus according to any one of claims 1 to 30, wherein

said display device includes:

liquid crystal; and

an electrode for applying the voltage to said liquid crystal, and

a part of said liquid crystal is driven in a state that there is none of said electrode in the vicinity thereof.

32. The image display apparatus according to any one of claims 1 to 30, wherein

said display device includes:

liquid crystal; and

a pixel electrode and a common electrode for applying the voltage to said liquid crystal, and

said liquid crystal is driven by an electric field which is generated between said pixel electrode and said common electrode, and is almost parallel to a substrate.

33. The image display apparatus according to anyone of claims 1 to 27, wherein

said display device is made of a material with which an echo phenomenon easily occurs.

34. An image display method for displaying an image by driving a display device based on an input video signal, comprising:

a drive step of driving said display device by switching a drive voltage between positive and negative for application based on said input video signal; and

an adjusting step of adjusting said drive voltage by correcting said input video signal or said drive voltage so that absolute values of said drive voltage between positive and negative become closer in at least any two successive frames.

35. An image display method for displaying an image by driving a display device based on an input video signal, comprising

a drive step of driving said display device by switching a drive voltage between positive and negative for application based on said input video signal, wherein

said drive step divides one vertical scanning period of said input video signal into a first sub period and a second sub period, and the drive voltage applied to the sub periods is different in polarity.

36. An image display method for displaying an image by driving a display device based on an input video signal, comprising

a drive step of driving said display device by switching a drive voltage between positive and negative for application based on said input video signal, wherein

said drive step divides one vertical scanning period of said input video signal into a first sub period and a second sub period, and outputs said input video signal in said first sub period, and outputs a compensation signal in said second sub period.

37. An image display method for displaying an image by driving a display device based on an input video signal, comprising

a drive step of driving said display device by switching a drive voltage between positive and negative for application based on said input video signal, wherein

said drive step

scans, in an n-th frame, odd-numbered scanning lines for a data signal, and even-numbered scanning lines f or a compensation signal, and

scans, in an n-th frame, the odd-numbered scanning lines for the compensation signal, and the even-numbered lines for the data signal.

38. An image display method for displaying an image by driving a display device based on an input video signal, comprising

a drive step of driving said display device by switching a drive voltage between positive and negative for application based on said input video signal, wherein

during one vertical scanning period of said input video signal, after sequentially scanning either ones of odd-numbered scanning lines and even-numbered scanning lines, said drive step sequentially scans the scanning lines.

39. An image display method for displaying an image by driving a display device based on an input video signal, comprising

a drive step of driving said display device by switching a drive voltage between positive and negative for application based on said input video signal, wherein

said drive step applies the drive voltage of the same polarity without polarity reverse to at least any two successive frames.