Image display apparatus and image display method

Abstract

When displaying moving images by using liquid crystal panels and others, a problem exists in that tail streaks occur, and image degradation is resultantly caused. To solve this problem, an echo suppression circuit 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 displays video signals including moving images. If these two frames are not the same in signal level, the signal is accordingly corrected so as to equalize the signal level of these frames. Based on the video signals and others corrected by the echo suppression circuit, a controller operates the liquid crystal panel with AC drive through a source driver and a gate driver. As such, the drive voltage used to operate the liquid crystal panel with AC drive is adjusted so as to be balanced between positive and negative. In this manner, the tail streaks are prevented when displaying moving images.

1 . A liquid crystal display apparatus for displaying an image based on an input video signal, said liquid crystal display apparatus comprising: 
 a display device for outputting image lights according to a voltage to be applied; and    a drive unit for driving said display device by switching a drive voltage applied across a pixel liquid crystal between positive and negative for application based on the input video signal, wherein    said display device is a liquid crystal display device including liquid crystal, 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, and    said drive unit is operable to drive said liquid crystal display device by dividing one vertical scanning period of the input video signal into a first sub period and a second sub period.    
   
   
       2 . The liquid crystal display apparatus according to  claim 1 , wherein the drive voltage applied to the sub periods is different in polarity.  
   
   
       3 . The liquid crystal display apparatus according to  claim 2 , wherein said drive unit is operable to output the same video signal in the first sub period and the second sub period.  
   
   
       4 . The liquid crystal display apparatus according to  claim 1 , wherein the first sub period and the second sub period are the same in length.  
   
   
       5 . The liquid crystal display apparatus according to  claim 1 , wherein the first sub period and the second sub period are not the same in length.  
   
   
       6 . The liquid crystal display apparatus according to  claim 1 , wherein said drive unit includes a division unit for dividing the one vertical scanning period of the input video signal into the first sub period and the second sub period.  
   
   
       7 . The liquid crystal display apparatus according to  claim 6 , wherein said division unit is operable to temporarily store the input video signal.  
   
   
       8 . The liquid crystal display apparatus according to  claim 6 , wherein said division unit is operable to delay the input video signal by a length of time equal to or shorter than the one vertical scanning period.  
   
   
       9 . The liquid crystal display apparatus according to  claim 6 , further comprising a conversion unit for converting the input video signal into a data display signal for driving said liquid crystal display device, 
 wherein in a process for converting the input video signal into the data display signal, said conversion unit is operable to divide one vertical scanning period of the input video signal into the first sub period and the second sub period.    
   
   
       10 . The liquid crystal display apparatus according to  claim 1 , for performing display by switching between a TV video signal and a PC video signal, 
 wherein the drive unit is operable to apply drive voltages in alternately different polarity in each of the sub periods of one vertical scanning period when a moving image of the TV video signal is displayed, and apply drive voltages in alternately different polarity in each vertical scanning period when an image of the PC video signal is displayed.    
   
   
       11 . The liquid crystal display apparatus according to  claim 10 , further comprising: 
 a first converter-circuit for converting the TV video signal to a video signal for the liquid crystal display device;    a second converter circuit for converting the PC video signal to a video signal for the liquid crystal display device; and    a switching unit for selecting and outputting, as the input video signal, either one of an output signal from said first converter circuit and an output signal from said second converter circuit, wherein    said drive unit includes a division unit for dividing the one vertical scanning period of the input video signal into the first sub period and the second sub period,    said division unit is incorporated into said first converter circuit, and    said drive unit is operable to apply drive voltages in alternately different polarity in each of the sub periods of one vertical scanning period while said switching unit is selecting the output signal from said first converter circuit, and apply drive voltages in alternately different polarity in each vertical scanning period while said switching unit is selecting the output signal from said second converter circuit.    
   
   
       12 . The liquid crystal display apparatus according to  claim 11 , wherein said drive unit is operable to drive said liquid crystal display device in such a manner as to scan two scanning lines of said liquid crystal display device at one time while said switching unit is selecting the output signal from said first converter circuit.  
   
   
       13 . The liquid crystal display apparatus according to  claim 12 , wherein said liquid crystal display device has TFTs placed therein in a staggered arrangement with respect to a gate wiring.  
   
   
       14 . The liquid crystal display apparatus according to  claim 1 , wherein said drive unit is operable to output the input video signal in the first sub period, and output a compensation signal in the second sub period.  
   
   
       15 . The liquid crystal display apparatus according to  claim 14 , wherein the second sub period is shorter than the first sub period.  
   
   
       16 . The liquid crystal display apparatus according to  claim 14 , wherein the drive voltage in the second sub period is a voltage of a pedestal level or lower when said liquid crystal display device is a normally black type, and is a voltage of the pedestal level or higher when said liquid crystal display device is a normally white type.  
   
   
       17 . The liquid crystal display apparatus according to  claim 14 , wherein said liquid crystal display device is a normally black type, and the drive voltage in said second sub period is 0V.  
   
   
       18 . The liquid crystal display apparatus according to  claim 14 , wherein the drive voltage in the second sub period is applied to a plurality of scanning lines at one time.  
   
   
       19 . An image display method for displaying an image by driving a display device based on an input video signal, wherein said display device is a liquid crystal display device including liquid crystal, 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, said method comprising: 
 driving the liquid crystal display device by switching a drive voltage applied across a pixel liquid crystal between positive and negative for application based on the input video signal, and by dividing one vertical scanning period of the input video signal into a first sub period and a second sub period.    
   
   
       20 . The image display method according to  claim 19 , wherein the drive voltage applied to the sub periods is different in polarity.  
   
   
       21 . The image display method according to  claim 19 , wherein said driving includes outputting the input video signal in the first sub period, and outputting a compensation signal in the second sub period.  
   
   
       22 . An image display method for displaying an image by driving a display device based on an input video signal, wherein said display device is a liquid crystal display device including liquid crystal, 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, said method comprising: 
 a drive step of driving said liquid crystal display device by switching a drive voltage applied across a pixel liquid crystal 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 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.  
   
   
   
       23 . An image display method for displaying an image by driving a display device based on an input video signal, wherein said display device is a liquid crystal display device including liquid crystal, 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, said method comprising: 
 a drive step of driving said liquid crystal display device by switching a drive voltage applied across a pixel liquid crystal 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 scanning lines other than said either ones of odd-numbered scanning lines and even-numbered scanning lines.    
   
   
       24 . An image display method for displaying an image by driving a display device based on an input video signal, wherein said display device is a liquid crystal display device including liquid crystal, 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, said method comprising: 
 a drive step of driving said liquid crystal display device by switching a drive voltage applied across a pixel liquid crystal 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.