Patent Publication Number: US-7916111-B2

Title: Apparatus for driving liquid crystal display device

Description:
This application claims the benefit of Korean Patent Application No. 10-2006-0057304, filed on Jun. 26, 2006, which is hereby incorporated by reference for all purposes as if fully set forth herein. 
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a liquid crystal display device, and more particularly, to an device and method for driving a liquid crystal display device which are capable of minimizing a motion blurring phenomenon of a display image and improving the display quality of the display image. 
     2. Discussion of the Related Art 
     Recently, a cathode ray tube has been replaced with various kinds of flat-panel display device having a reduced weight and volume. The flat-panel display device includes a liquid crystal display device, a field emission display device, a plasma display panel, and a light emitting display device. 
     Among the flat-panel display device, the liquid crystal display device displays a moving image using a thin film transistor as a switching element. Since such a liquid crystal display device has a size smaller than that of the cathode ray tube, the liquid crystal display device is widely being used in a personal computer, a notebook computer, office automation equipments such as a copier, and a mobile device such as a mobile phone. 
     Meanwhile, the cathode ray tube, the plasma display panel, and the field emission display device are driven in an impulse form in which phosphor light is emitted to display data during a very short initial time of a frame period and a pause interval is held during most of the frame period, as shown in  FIG. 1 . 
     In the display device driven in the impulse form, the definition of a display image is excellent and a blurring phenomenon, in which a display image blurs, is prevented by disconnecting adjacent frame images. 
     In contrast, the liquid crystal display device is driven in a hold form in which data is supplied to liquid crystal by a high gate voltage during a scanning period and the data supplied to the liquid crystal is held in a non-scanning period which is substantially most of a frame period, as shown in  FIG. 2 . In the display device driven in the hold form, since an image is held during a frame period, a motion blurring phenomenon, in which a moving image blurs, occurs and thus display quality deteriorates. 
     SUMMARY OF THE INVENTION 
     Accordingly, the present invention is directed to a device and method for driving a liquid crystal display device that substantially obviate one or more problems due to limitations and disadvantages of the related art. 
     An object of the present invention is to provide a device and method for driving a liquid crystal display device, which are capable of minimizing a motion blurring phenomenon of a display image and improving the display quality of the display image. 
     Additional advantages, objects, and features of the invention will be set forth in part in the description which follows and in part will become apparent to those having ordinary skill in the art upon examination of the following or may be learned from practice of the invention. The objectives and other advantages of the invention may be realized and attained by the structure particularly pointed out in the written description and claims hereof as well as the appended drawings. 
     To achieve these objects and other advantages and in accordance with the purpose of the invention, as embodied and broadly described herein, an apparatus for driving a liquid crystal display device includes a liquid crystal panel having liquid crystal cells formed in regions defined by a plurality of gate lines and a plurality of data lines; a timing controller which analyzes a motion speed of an image in input data and converts the input data of one frame into different first and second double frame data or identical first and second double frame data according to the motion speed; a gate driver which sequentially supplies gate on voltages to the gate lines for each of first and second double frames under the control of the timing controller; and a data driver which converts the double frame data supplied from the timing controller into an analog video signal and supplies the analog video signal to the data lines under the control of the timing controller. 
     It is to be understood that both the foregoing general description and the following detailed description of the present invention are exemplary and explanatory and are intended to provide further explanation of the invention as claimed. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The accompanying drawings, which are included to provide a further understanding of the invention and are incorporated in and constitute a part of this application, illustrate embodiment(s) of the invention and together with the description serve to explain the principle of the invention. In the drawings: 
         FIG. 1  is a characteristic diagram showing a driving characteristic of a display device driven in an impulse form; 
         FIG. 2  is a characteristic diagram showing a driving characteristic of a display device driven in a hold form; 
         FIG. 3  is a schematic diagram showing an apparatus for driving a liquid crystal display device according to an embodiment of the present invention; 
         FIG. 4  is a schematic block diagram showing a timing controller according to the embodiment of the present invention; 
         FIG. 5  is a schematic block diagram showing a data converter according to a first embodiment of the present invention; 
         FIG. 6  is a schematic block diagram showing a moving image analyzer according to a first embodiment of the present invention; 
         FIG. 7  is a schematic block diagram showing an image modulator according to a first embodiment of the present invention; 
         FIG. 8  is a graph showing a gamma curve for a frame N th  according to an embodiment of the present invention; 
         FIG. 9  is a graph showing a gamma curve for a frame N+1 th  according to an embodiment of the present invention; 
         FIG. 10  is a graph showing a gamma curve of input data according to an embodiment of the present invention; 
         FIG. 11  is a schematic block diagram showing an image modulator according to a second embodiment of the present invention; 
         FIG. 12  is a schematic block diagram showing an image filter according to an embodiment of the present invention; 
         FIG. 13  is a schematic block diagram showing a motion filter according to an embodiment of the present invention; 
         FIG. 14  is a schematic block diagram showing a gray scale filter according to an embodiment of the present invention; 
         FIG. 15  is a schematic block diagram showing a data converter according to a second embodiment of the present invention; 
         FIG. 16  is a schematic block diagram showing a moving image analyzer according to a second embodiment of the present invention; 
         FIG. 17  is a schematic block diagram showing an image modulator according to a third embodiment of the present invention; and 
         FIG. 18  is a schematic block diagram showing an image modulator according to a fourth embodiment of the present invention. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Reference will now be made in detail to the preferred embodiments of the present invention, examples of which are illustrated in the accompanying drawings. Wherever possible, the same reference numbers will be used throughout the drawings to refer to the same or like parts. 
       FIG. 3  is a schematic diagram showing an apparatus for driving a liquid crystal display device according to an embodiment of the present invention. 
     Referring to  FIG. 3 , the apparatus for driving the liquid crystal display device according to the embodiment of the present invention includes a liquid crystal panel  2  including liquid crystal cells formed in regions defined by n gate lines GL 1  to GLn and m data lines DL 1  to DLm; a timing controller  8  for converting input data Data of one frame into different first and second frame data RGB or identical first and second double frame data RGB according to the motion of the input data Data; a gate driver  6  for sequentially supplying gate on voltages to the gate lines GL 1  to GLn for each of the double frames under the control of the timing controller  8 ; and a data driver for converting the double frame data RGB sequentially supplied from the timing controller  8  into analog video signals and supplying the analog video signals to the data lines DL 1  to DLm under the control of the timing controller  8 . 
     The liquid crystal panel  2  includes a transistor array substrate and a color filter array substrate, both of which face each other, a spacer for maintaining a constant cell gap between the two array substrates, and liquid crystal filled in a liquid crystal space provided by the spacer. 
     The liquid crystal panel  2  includes TFTs formed in regions defined by the n gate lines GL 1  to GLn and the m data lines DL 1  to DLm, and liquid crystal cells connected to the TFTs. The TFTs supply the analog video signals from the data line DL 1  to DLm to the liquid crystal cells in response to the gate on voltages from the gate lines GL 1  to GLn. Since each liquid cell includes a pixel electrode connected to each TFT and a common electrode, both of which face each other with the liquid crystal interposed therebetween, each liquid cell may be equivalently represented by a liquid crystal capacitor Clc. Such a liquid crystal cell includes a storage capacitor Cst for holding the analog video signal charged in the liquid crystal capacitor Clc until a next analog video signal is charged. 
     The timing controller  8  converts the input data Data of one frame into different first and second double frame data RGB or identical first and second double frame data RGB according to the motion of an input image, and supplies the double frame data to the data driver  4 . The timing controller  8  receives the externally input data Data having a frequency of 60 Hz, generates the double frame data RGB having a frequency of 120 Hz, and supplies the double frame data to the data driver  4 . 
     The timing controller  8  modulates a main clock MCLK, a data enable signal DE, and horizontal and vertical synchronization signals Hsync and Vsync input externally, and generates a data control signal DCS and a gate control signal GCS for respectively controlling drive timings of the data driver  4  and the gate driver  6  using at least one of the modulated main clock MCLK, the modulated data enable signal DE, and the modulated horizontal and vertical synchronization signals Hsync and Vsync, in order to display the double frame data RGB having the frequency of 120 Hz on the liquid crystal panel  2 . 
     The gate driver  6  includes a shift register for sequentially generating the gate on voltages in response to a gate start pulse GSP and a gate shift clock GSC in the gate control signal GCS supplied from the timing controller  8 . The gate driver  6  sequentially supplies the gate on voltages to the gate lines GL of the liquid crystal panel  2  and turns on the TFTs connected to the gate lines GL, for each double frame. 
     The data driver  4  converts the double frame data RGB supplied from the timing controller  8  to the analog video signals according to the data control signal DCS supplied from the timing controller  8 , and supplies the analog video signals of one horizontal line to the data lines DL for each horizontal period when the gate on voltages are supplied to the gate lines GL for each double frame. That is, the data driver  4  selects a gamma voltage having a predetermined level according to a gray scale value of the data RGB and supplies the selected gamma voltage to the data lines DL 1  to DLm. At this time, the data driver  4  inverts the polarities of the analog video signals supplied to the data lines DL in response to a polarity control signal POL supplied from the timing controller  8 . 
       FIG. 4  is a schematic block diagram showing the timing controller shown in  FIG. 3 . 
     Referring to  FIGS. 3 and 4  together, the timing controller  8  includes a control signal generator  22  and a data converter  24 . 
     The control signal generator  22  multiplies the frequencies of the main clock MCLK, the data enable signal DE, and the horizontal and vertical synchronization signals Hsync and Vsync input externally by 2, and generates the data control signal DCS for controlling the data driver  4  and the gate control signal GCS for controlling the gate driver  6  using at least one of the frequency-multiplied main clock MCLK, the frequency-multiplied enable signal DE, and the frequency-multiplied horizontal and vertical synchronization signals Hsync and Vsync. Here, the control signal generator  22  multiplies the frequency of the vertical synchronization signal Vsync having the frequency of 60 Hz by 2 and generates a vertical synchronization signal Vsync′ having a frequency of 120 Hz. 
     The control signal generator  22  supplies the data control signal DCS including a source output enable SOE, a source shift clock SSC, a source start pulse SSP, and a polarity control signal POL to the data driver  4 , and supplies the gate control signal GCS including a gate start pulse SSP, a gate shift clock GSC and a gate output enable signal GOE to the gate driver  6 . The control signal generator  22  supplies the frequency-multiplied vertical synchronization signal Vsync′ to the data converter  24 . 
     The data converter  24  converts the input data Data of one frame into two pieces of different double frame data RGB and two pieces of identical double frame data RGB according to the motion of the input image, and supplies the double frame data RGB to the data driver  4 . 
     As shown in  FIG. 5 , the data converter  24  according to a first embodiment of the present invention includes a double frame generator  110 , a moving image analyzer  120 , and an image modulator  130 . 
     The double frame generator  110  converts the externally input data Data of one frame into two pieces of identical double frame data DF. For example, the double frame generator  110  stores the externally input data Data of one frame having a frequency of 60 Hz and supplies the stored data to the image modulator  130  so as to have a frequency of 120 Hz. 
     The moving image analyzer  120  analyzes whether the externally input data Data is a still image or a moving image and generates a motion signal MS. 
     As shown in  FIG. 6 , the moving image analyzer  120  includes a luminance separator  122 , a frame memory  124 , and a motion detector  126 . 
     The luminance separator  122  separates luminance component Y from the externally input data Data of one frame and supplies the luminance component to the frame memory  124  and the motion detector  126 . 
     The frame memory  124  stores the luminance component Y supplied from the luminance separator  122  in a frame unit and supplies the luminance component Y in the frame unit to the motion detector  126 . 
     The motion detector  126  compares luminance component YFn- 1  of a previous frame supplied from the frame memory  124  with luminance component YFn of a current frame and generates the motion signal MS for the motion of the image. That is, the motion detector  126  generates 0 th  motion signal MS corresponding to a still image if the luminance component YFn- 1  of the previous frame are identical to the luminance component YFn of the current frame. 
     The motion detector  126  generates a motion signal MS corresponding to a moving image if the luminance component YFn- 1  of the previous frame are different from the luminance component YFn of the current frame. That is, the motion detector  126  generates a first motion signal MS when the motion distance between images of the previous frame and the current frame is 1 to 3 pixels, generates a second motion signal MS when the motion distance between images of the previous frame and the current frame is 4 to 6 pixels, or generates a third motion signal MS when the motion distance between images of the previous frame and the current frame is 7 to 10 pixels. 
     In  FIG. 5 , the image modulator  130  according to the first embodiment of the present invention includes a gamma curve setting unit  132 , a look-up table  134 , and a gray scale generator  136 , as shown in  FIG. 7 . 
     The gamma curve setting unit  132  generates a selection signal CS corresponding to the motion signal MS supplied from the moving image analyzer  120  according to the frequency-multiplied vertical synchronization signal Vsync′ supplied from the control signal generator  22 , and supplies the selection signal CS to the gray scale generator  136 . That is, when the 0 th  motion signal MS is supplied from the moving image analyzer  120 , the gamma curve setting unit  132  generates and supplies a bypass selection signal CS to the gray scale generator  136 . When the frequency-multiplied vertical synchronization signal Vsync′ is an N th  frame, the gamma curve setting unit  132  generates and supplies first to third gamma curve selection signals CS for the N th  frame corresponding to the first to third motion signals MS supplied from the moving image analyzer  120  to the gray scale generator  136 . In contrast, when the frequency-multiplied vertical synchronization signal Vsync′ is an N+1 th  frame, the gamma curve setting unit  132  generates and supplies first to third gamma curve selection signals CS for the N+1 th  frame corresponding to the first to third motion signals MS supplied from the moving image analyzer  120  to the gray scale generator  136 . 
     The look-up table  134  includes a plurality of memories for registering a plurality of gamma curves for setting the gamma curve according to the motion speed of the moving image. 
     In more detail, the look-up table  134  includes a first memory for registering a plurality of different gamma curves for the N th  frame for setting the gamma curve of a first double frame data DF according to the motion speed of the moving image, and a second memory for registering a plurality of different gamma curves for the N+1 th  frame for setting the gamma curve of a second double frame data DF according to the motion speed of the moving image. 
     As shown in  FIG. 8 , the first memory stores gray scale values corresponding to the first to third gamma curves LG 1 , LG 2  and LG 3  for the N th  frame. 
     The first gamma curve LG 1  for the N th  frame has a gray scale value of ‘0’ when the gray scale value of the input data is equal to or less than a first reference value LR 1  for the N th  frame and has gray scale values on a curved line between the first reference value LR 1  for the N th  frame and a gray scale value of ‘2 i −1’ (here, i is the number of bits of the input data) when the gray scale value of the input data is greater than the first reference value LR 1  for the N th  frame. The second gamma curve LG 2  for the N th  frame has a gray scale value of ‘0’ when the gray scale value of the input data is equal to or less than a second reference value LR 2  for the N th  frame, which is greater than the first reference value LR 1  for the N th  frame, and has gray scale values on a curved line between the second reference value LR 2  for the N th  frame and the gray scale value of ‘2 i −1’ when the gray scale value of the input data is greater than the second reference value LR 2  for the N th  frame. The third gamma curve LG 3  for the N th  frame has a gray scale value of ‘0’ when the gray scale value of the input data is equal to or less than a third reference value LR 3  for the N th  frame, which is greater than the second reference value LR 2  for the N th  frame, and has gray scale values on a curved line between the third reference value LR 3  for the N th  frame and the gray scale value of ‘2 i −1’ when the gray scale value of the input data is greater than the third reference value LR 3  for the N th  frame. Here, the third reference value LR 3  for the N th  frame may be the half of the gray scale value of ‘2 i −1’, and the first and second reference values LR 1  and LR 2  for the N th  frame may respectively be the gray scale values located at the ⅓ and ⅔ points between the gray scale value of ‘0’ and the third reference value LR 3  for the N th  frame. In the gray scale values on the curved lines of the first to third gamma curves LG 1 , LG 2  and LG 3  for the N th  frame, a ratio of an output gray scale value to an input gray scale value increases as the input gray scale value increases. Meanwhile, the first to third reference values LR 1 , LR 2  and LR 3  for the N th  frame may be reset by a user according to the motion speed. 
     As shown in  FIG. 9 , the second memory stores gray scale values corresponding to first to third gamma curves HG 1 , HG 2  and HG 3  for the N+1 th  frame. 
     The first gamma curve HG 1  for the N+1 th  frame has a gray scale value of ‘2 i −1’ when the gray scale value of the input data is equal to or greater than a first reference value HR 1  for the N+1 th  frame and has gray scale values on a curved line between the first reference value HR 1  for the N+1 th  frame and the gray scale value of ‘0’ when the gray scale value of the input data is less than the first reference value HR 1  for the N+1 th  frame. The second gamma curve HG 2  for the N+1 th  frame has the gray scale value of ‘2 i −1’ when the gray scale value of the input data is equal to or greater than a second reference value HR 2  for the N+1 th  frame, which is less than the first reference value HR 1  for the N+1 th  frame, and has gray scale values on a curved line between the second reference value HR 2  for the N+1 th  frame and the gray scale value of ‘0’ when the gray scale value of the input data is less than the second reference value HR 2  for the N+1 th  frame. The third gamma curve HG 3  for the N+1 th  frame has a gray scale the value of ‘2 i −1’ when the gray scale value of the input data is equal to or greater than a third reference value HR 3  for the N+1 th  frame, which is less than the second reference value HR 2  for the N+1 th  frame, and has gray scale values on a curved line between the third reference value HR 3  for the N+1 th  frame and a gray scale value of ‘0’ when the gray scale value of the input data is less than the third reference value HR 3  for the N+1 th  frame. Here, the third reference value HR 3  for the N+1 th  frame may be at least the half of the gray scale value of ‘2 i −1’ and the first and second reference values HR 1  and HR 2  for the N+1 th  frame may respectively be the gray scale values located at the ⅓ and ⅔ points between the gray scale value of ‘2 i −1’ and the third reference value HR 3  for the N+1 th  frame. In the gray scale values on the curved lines of the first to third gamma curves HG 1 , HG 2  and HG 3  for the N+1 th  frame, a ratio of an output gray scale value to an input gray scale value decreases as the input gray scale value increases. Meanwhile, the first to third reference values HR 1 , HR 2  and HR 3  for the N+1 th  frame may be reset by a user according to the motion speed. 
     The gray scale generator  136  bypasses the double frame data DF supplied from the double frame generator  110  to the data driver  4  or modulates the double frame data DF to supply the modulated double frame data to the data driver  4 , according to the selection signal CS supplied from the gamma curve setting unit  132 . 
     In more detail, the gray scale generator  136  bypasses the first and second double frame data DF successively supplied from the double frame generator  110  to the data driver  4 , and outputs the original input data of one frame without modulation, when receiving the bypass selection signal CS. 
     In contrast, the gray scale generator  136  modulates the input double frame data DF according to the first to third gamma curves LG 1  to LG 3  or HG 1  to HG 3  stored in the look-up table  134 , and supplies the modulated double frame data to the data driver  4 , when receiving the first to third gamma curve selection signals CS for the N th  frame or the N+1 th  frame. 
     In more detail, the gray scale generator  136  modulates the double frame data DF according to the first gamma curve LG 1  for the N th  frame when receiving the first gamma curve selection signal CS for the N th  frame, modulates the double frame data DF according to the second gamma curve LG 2  for the N th  frame when receiving the second gamma curve selection signal CS for the N th  frame, and modulates the double frame data DF according to the third gamma curve LG 3  for the N th  frame when receiving the third gamma curve selection signal CS for the N th  frame. 
     The gray scale generator  136  modulates the double frame data DF according to the first gamma curve HG 1  for the N+1 th  frame when receiving the first gamma curve selection signal CS for the N+1 th  frame, modulates the double frame data DF according to the second gamma curve HG 2  when receiving the second gamma curve selection signal CS for the N+1 th  frame, and modulates the double frame data DF according to the third gamma curve HG 3  for the N+1 th  frame when receiving the third gamma curve selection signal CS for the N+1 th  frame. 
     The image modulator  130  according to the first embodiment of the present invention bypasses the first and second double frame data DF supplied from the double frame generator  110  to the data driver  4  without modulation such that the original data of one frame is displayed without alteration, when receiving the motion signal MS corresponding to the still image. 
     The image modulator  130  according to the first embodiment of the present invention differently sets the gamma curves on a frame-by-frame basis according to the motion signal MS corresponding to the motion speed of the moving image, modulates the first and second double frame data DF supplied from the double frame generator  110 , and supplies the modulated first and second double frame data DF to the data driver  4 , when receiving the motion signal MS corresponding to the moving image. The image modulator  130  according to the first embodiment of the present invention modulates the first double frame data DF to a low gray scale so as to become close to the gray scale value of ‘0’ as the motion speed increases in the N th  frame. The image modulator  130  according to the first embodiment of the present invention modulates the second double frame data DF to a high gray scale so as to become close to the gray scale value of ‘2 i −1’ as the motion speed increases in the N+1 th  frame. 
     Meanwhile, as shown in  FIG. 10 , the gamma curve of the first and second double frame data DF output from the image modulator  130  according to the first embodiment of the present invention is identical to the gamma curve of the original input data Data of one frame. 
     The apparatus for driving the liquid crystal display device according to the embodiment of the present invention displays the first and second double frame data DF identical to the original image on the liquid crystal panel  2  if the input data is a still image, and modulates the original image to the first and second double frame data DF, sets the gamma curves LG 1  to LG 3  and HG 1  to HG 3  according to the motion speed of the moving image, relatively darkly displays the first double frame data DF on the liquid crystal panel  2 , and relatively brightly displays the second double frame data DF on the liquid crystal panel  2 , if the input data is a moving image. 
     Accordingly, the apparatus for driving the liquid crystal display device according to the embodiment of the present invention can display a still image without noise, that is, flicker, and can display a high-definition moving image without motion blurring. 
       FIG. 11  is a schematic block diagram showing an image modulator  230  according to a second embodiment of the present invention. 
     Referring to  FIG. 11 , the image modulator  230  according to the second embodiment of the present invention includes a gamma curve setting unit  232 , a look-up table  234 , an image filter  235 , and a gray scale generator  236 . 
     The gamma curve setting unit  232  and the look-up table  234  respectively are equal to the gamma curve setting unit  132  and the look-up table  134  of the image modulator  130  according to the first embodiment of the present invention shown in  FIG. 7  and thus the detailed description thereof will be omitted. 
     As shown in  FIG. 12 , the image filter  235  includes a luminance/chrominance separator  300 , a delay unit  310 , a motion filter  320 , and a mixer  330 . 
     The luminance/chrominance separator  300  separates luminance component Y and chrominance components U and V from the double frame data DF supplied from the double frame generator. 
     The delay unit  310  delays the chrominance components U and V in a frame unit while the motion filter  320  modulates the luminance component Y in the frame unit, and supplies the delayed chrominance components UD and VD to the mixer  330 . 
     The motion filter  320  filters the luminance component Y supplied from the luminance/chrominance separator  300  according to the motion signal MS supplied from the moving image analyzer  120  and supplies the filtered luminance component Y′ to the mixer  330 . 
     As shown in  FIG. 13 , the motion filter  320  includes a line memory  322 , a low-pass filter  324 , a gray scale filter  326 , and a multiplier  328 . 
     The line memory  322  stores the luminance component Y of at least three horizontal lines using at least three line memories for storing the luminance component Y supplied from the luminance/chrominance separator  300  in a horizontal line unit, and supplies the luminance component Y in an j×j block unit (here, j is an integer of 3 or more) to the low-pass filter  324 . 
     The low-pass filter  324  receives the luminance component Y in the j×j block unit from the line memory  322 , low-pass filters the luminance component Y, and supplies the filtered luminance component Yf to the gray scale filter  326 . The low-pass filter  324  expands a Gaussian distribution of the luminance component Y based on j×j block unit using the luminance component Y in the j×j block unit. The luminance component Yf low-pass filtered by the low-pass filter  324  become a smooth image. 
     As shown in  FIG. 14 , the gray scale filter  326  includes an adder  350 , a comparator  352 , a selector  354 , a Gaussian filter  356 , and a sharpness filter  358 . 
     The adder  350  adds a luminance component Yf of a peripheral portion except for a central portion in the luminance component Yf based on j×j block units, which are processed by low pass filtering by the low-pass filter  324 , and supplies the added luminance component Ya to the comparator  352 . 
     The comparator  352  compares the luminance component Ya added by the adder  350  with the luminance component Yc of the central portion in the luminance component Yf based on j×j block unit low-pass filtered by the low-pass filter  324 , and generates a comparison signal SS having first and second logic states. At this time, the comparator  352  generates a comparison signal SS having the first logic state when the luminance component Yc of the central portion is larger than the added luminance component Ya and generates the comparison signal SS having the second logic state when the luminance component Yc of the central portion is equal to or smaller than the added luminance component Ya. 
     The selector  354  supplies the luminance component Yf low-pass filtered by the low-pass filter  324  to the Gaussian filter  356  according to the comparison signal SS having the first logic state supplied from the comparator  352 . The selector  354  supplies the luminance component Yf low-pass filtered by the low-pass filter  324  to the sharpness filter  358  according to the comparison signal SS having the second logic state supplied from the comparator  352 . 
     The Gaussian filter  356  filters the low-pass filtered luminance component Yf supplied from the selector  354  according to the motion signal MS supplied from the moving image analyzer  120  such that summation of the low-pass filtered luminance component Yf becomes ‘1’ and supplies the filtered luminance component to the multiplier  328 . The Gaussian filter  356  smoothly filters the luminance component Yf based on j×j block unit so as to minimize an overshoot generated in the luminance component Yf based on j×j block unit. 
     The sharpness filter  358  filters the low-pass filtered luminance component Yf supplied from the selector  354  according to the motion signal MS supplied from the moving image analyzer  120  such that summation of the low-pass filtered luminance component Yf becomes ‘0’ and supplies the filtered luminance component to the multiplier  328 . At this time, in the luminance component Ym based on j×j block unit filtered by the sharpness filter  358 , since the luminance component of the central portion has a value larger than that of the luminance component of the peripheral portion but the luminance component of the peripheral portion has a value smaller than that of the luminance component of the central portion, the sum thereof becomes ‘0’. The sharpness filter  358  sharply filters the luminance component based on j×j block unit such that undershoot is generated in the luminance component Yf based on j×j block unit according to the motion speed of the moving image corresponding to the motion signal MS. 
     The gray scale filter  326  filters the luminance component Yf based on j×j block unit low-pass filtered by the low-pass filter  324  such that the overshoot is minimized and the undershoot is generated in the boundary of the moving image according to the motion signal MS. 
     The multiplier  328  multiplies the luminance component Ym supplied from the gray scale filter  326  by an externally input gain value G, and supplies the filtered luminance component Y′ to the mixer  330 . The level of the undershoot generated in the boundary of the moving image in the filtered luminance component Y′ is adjusted by the gain value. 
     In  FIG. 12 , the mixer  330  mixes the luminance component Y′ filtered by the motion filter  320  with the chrominance components UD and VD delayed by the delay unit  310 , and generates a filtered double frame data FDF. 
     The image filter  235  filters the double frame data DF such that a black line is clearly drawn on the boundary of the moving image by only the undershoot except for the overshoot which is sensitive to the visibility of a person, and supplies the filtered double frame data FDF to the gray scale generator  236 . 
     In  FIG. 11 , the gray scale generator  236  bypasses the filtered double frame data FDF supplied from the mixer  330  of the image filter  235  or modulates the filtered double frame data FDF to supply the modulated signal to the data driver  4 , according to the selection signal CS supplied from the gamma curve setting unit  232  to the data driver  4 . 
     The gray scale generator  236  is equal to the gray scale section  136  of the image modulator  130  of the first embodiment of the present invention and thus the detailed description will be omitted. 
     The apparatus for driving the liquid crystal display device including the second modulator  230  according to the second embodiment of the present invention displays the first and second double frame data DF equal to the original image on the liquid crystal panel  2  if the input data of one frame is a still image, and modulates the original image to the first and second double frame data DF, Gaussian- or sharpness-filters the boundary of the moving image in the first and second double frame data DF according to the motion speed of the moving image, sets the gamma curve according to the motion speed, relatively darkly displays the first double frame data DF on the liquid crystal panel  2 , and relatively brightly displays the second double frame data DF on the liquid crystal panel  2 , if the input data of one frame is a moving image. 
     Accordingly, the apparatus for driving the liquid crystal display device including the image modulator  230  according to the second embodiment of the present invention can display a still image without noise, that is, flicker, and can display a high-definition stereoscopic moving image without motion blurring by filtering an image such that only an undershoot is generated in the boundary of the moving image according to the motion speed of the moving image. 
       FIG. 15  is a schematic block diagram showing a data converter according to a second embodiment of the present invention. 
     Referring to  FIGS. 15 and 4  together, the data converter  524  according to the second embodiment of the present invention includes a double frame generator  610 , a moving image analyzer  620 , and an image modulator  630 . 
     The double frame generator  610  is equal to the double frame generator  110  shown in  FIG. 5  and thus the detailed description thereof will be omitted. 
     As shown in  FIG. 16 , the moving image analyzer  620  includes a luminance separator  622 , a frame memory  624 , and a motion detector  626 . 
     The luminance separator  622  separates luminance component Y from the externally input data Data of one frame and supplies the luminance component Y to the frame memory  624  and the motion detector  626 . 
     The frame memory  624  stores the luminance component Y supplied from the luminance separator  622  in a frame unit, and supplies the stored luminance component Y in the frame unit to the motion detector  626 . 
     The motion detector  626  compares luminance component YFn- 1  of a previous frame supplied from the frame memory  624  with the luminance component YFn of a current frame in the same manner as the description of  FIG. 6  and generates the motion signal MS for the motion of an image. The motion generator  626  for generating the motion signal MS is equal to the motion detector  126  shown in  FIG. 6  and thus the detailed description thereof will be omitted. 
     The motion detector  626  generates motion position information MP of the boundary of the moving image, and supplies the motion position information MP to the image modulator  630 , if the input data is the moving image. Here, the motion position information MP is address information of vertical and horizontal pixels for the boundary of the moving image on the liquid crystal panel  2 . 
       FIG. 17  is a schematic block diagram showing an image modulator according to a third embodiment of the present invention. 
     Referring to  FIGS. 17 and 15 , the image modulator  630  according to the third embodiment of the present invention includes a gamma curve setting unit  632 , a look-up table  634 , and a gray scale generator  636 . 
     The gamma curve setting unit  632  and the look-up table  634  respectively are equal to the gamma curve setting unit  132  and the look-up table  134  of the image modulator  130  according to the first embodiment of the present invention shown in  FIG. 7  and thus the detailed description thereof will be omitted. 
     The gray scale generator  636  bypasses the double frame data DF supplied from the double frame generator  610  to the data driver  4  or modulates the double frame data DF to supply the modulated double frame data to the data driver  4 , according to the selection signal CS supplied from the gamma curve setting unit  632 . 
     In more detail, the gray scale generator  636  bypasses the first and second double frame data DF successively supplied from the double frame generator  610  to the data driver  4  and outputs the original input data of one frame without modulation, when receiving the bypass selection signal CS. 
     In contrast, the gray scale generator  636  modulates the data of the boundary of the moving image corresponding to the motion position information MP supplied from the moving image analyzer  620  in the input double frame data DF according to the first to third gamma curves LG 1  to LG 3  for the N th  frame or the first to third gamma curves HG 1  to HG 3  for the N+1 th  frame stored in the look-up table  634 , and supplies the modulated double frame data to the data driver  4 , when receiving the first to third gamma curve selection signals CS for the N th  frame or the N+1 th  frame. That is, the gray scale generator  636  modulates only the data of the boundary of the moving image by referring to the different gamma curves LG 1  to LG 3  and HG 1  to HG 3  according to the motion speed such that the gray scale of the boundary of the moving image is reduced to prevent a discontinuous artifact from being generated. 
     The first to third gamma curves LG 1  to LG 3  for the N th  frame and the first to third gamma curves HG 1  to HG 3  for the N+1 th  frame, which are set in the frame unit according to the motion signal MS, are the same as described above and thus the detailed description thereof will be omitted. 
     The apparatus for driving the liquid crystal display device including the data converter  524  having the image modulator  630  according to the second embodiment of the present invention displays the first and second double frame data DF identical to the original image on the liquid crystal panel  2  if the input data is a still image, and modulates the original image to the first and second double frame data DF, sets the gamma curves LG 1  to LG 3  and HG 1  to HG 3  according to the motion speed of the moving image, relatively darkly displays only the data of the boundary of the moving image in the first double frame data DF on the liquid crystal panel  2 , and relatively brightly displays only the data of the boundary of the moving image in the second double frame data DF on the liquid crystal panel  2 , if the input data is a moving image. 
     Accordingly, the apparatus for driving the liquid crystal display device including the data converter  524  according to the third embodiment of the present invention can display a still image without noise, that is, flicker, and can display a high-definition moving image without motion blurring by preventing a discontinuous artifact from being generated in the boundary of the moving image according to the motion speed of the moving image. 
       FIG. 18  is a schematic block diagram showing an image modulator according to a fourth embodiment of the present invention. 
     Referring to  FIGS. 18 and 15  together, the image modulator  730  according to the fourth embodiment of the present invention includes a gamma curve setting unit  732 , a look-up table  734 , an image filter  735 , and a gray scale generator  736 . 
     The gamma curve setting unit  732  and the look-up table  734  respectively are equal to the gamma curve setting unit  132  and the look-up table  134  of the image modulator  130  according to the first embodiment of the present invention shown in  FIG. 7  and thus the detailed description thereof will be omitted. 
     The image filter  735  filters the double frame data DF by the same manner as the image filter  235  shown in  FIGS. 12 and 14  and supplies the filtered data to the gray scale generator  736 . That is, if the received data is a moving image, the image filter  735  filters the double frame data DF such that that a black line is clearly drawn on the boundary of the moving image by only the undershoot except for the overshoot which is sensitive to the visibility of a person. 
     The gray scale generator  736  bypasses the double frame data DF supplied from the image filter  735  to the data driver  4  or modulates the double frame data DF to supply the modulated double frame data to the data driver  4 , according to the selection signal CS supplied from the gamma curve setting unit  732 . 
     In more detail, the gray scale generator  736  bypasses the first and second double frame data DF successively supplied from the image filter  735  to the data driver  4  and outputs the original input data of one frame without modulation, when receiving the bypass selection signal CS. 
     In contrast, the gray scale generator  736  modulates the data of the boundary of the moving image corresponding to the motion position information MP supplied from the moving image analyzer  620  in the input double frame data DF according to the first to third gamma curves LG 1  to LG 3  for the N th  frame or the first to third gamma curves HG 1  to HG 3  for the N+1 th  frame stored in the look-up table  734 , and supplies the modulated double frame data to the data driver  4 , when receiving the first to third gamma curve selection signals CS for the N th  frame or the N+1 th  frame. That is, the gray scale generator  736  modulates only the data of the boundary of the moving image by referring to the different gamma curves LG 1  to LG 3  and HG 1  to HG 3  according to the motion speed such that the gray scale of the boundary of the moving image is reduced to prevent a discontinuous artifact from being generated. 
     The first to third gamma curves LG 1  to LG 3  for the N th  frame and the first to third gamma curves HG 1  to HG 3  for the N+1 th  frame, which are set in the frame unit according to the motion signal MS, are the same as described above and thus the detailed description thereof will be omitted. 
     The apparatus for driving the liquid crystal display device including the data converter  524  having the image modulator  730  according to the fourth embodiment of the present invention displays the first and second double frame data DF identical to the original image on the liquid crystal panel  2  if the input data is a still image, and modulates the original image to the first and second double frame data DF, and Gaussian-filters or Sharpness-filters the boundary of the moving image in the first and second double frame data DF according to the motion speed of the moving image, sets the gamma curves LG 1  to LG 3  and HG 1  to HG 3  according to the motion speed of the moving image, relatively darkly displays only the data of the boundary of the moving image in the first double frame data DF on the liquid crystal panel  2 , and relatively brightly displays only the data of the boundary of the moving image in the second double frame data DF on the liquid crystal panel  2 , if the input data is a moving image. 
     Accordingly, the apparatus for driving the liquid crystal display device including the data converter  524  including the image modulator  730  according to the fourth embodiment of the present invention can display a still image without noise, that is, flicker, and can display a high-definition stereoscopic moving image without motion blurring by preventing a discontinuous artifact from being generated in the boundary of the moving image according to the motion speed of the moving image. 
     As described above, according to an device and method for driving a liquid crystal display device of the embodiments of the present invention, if an input data is a still image of one frame, it is possible to display the still image without noise, that is, flicker, by displaying first and second double frame data equal to an original image on a liquid crystal panel. 
     If the input data is a moving image of one frame, since the original data is modulated to first and second double frame data, gamma curves are set according to the motion speed of the moving image, the first double frame data is relatively darkly modulated and displayed on the liquid crystal panel, and the second double frame data is relatively brightly modulated and displayed on the liquid crystal panel, it is possible to display a high-definition moving image without motion blurring. 
     If the input data is a moving image of one frame, since the boundary of the moving image in the first and second double frame data is Gaussian- or Sharpness-filtered according to the motion speed of the moving image and the image is filtered such that only an undershoot is generated in the boundary of the moving image according to the motion speed of the moving image, it is possible to display a high-definition stereoscopic moving image without motion blurring. 
     If the input data is a moving image of one frame, since gamma curves are set according to the moving speed of the moving image, only the data of the boundary of the moving image in the first double frame data is relatively darkly modulated, and only the data of the boundary of the moving image in the second double frame data is relatively brightly modulated such that a discontinuous artifact is prevented from being generated in the boundary of the moving image according to the motion speed of the moving image, it is possible to display a high-definition moving image without motion blurring. 
     If the input data is a moving image of one frame, since the boundary of the moving image in the first and second double frame data is Gaussian- or Sharpness-filtered according to the motion speed of the moving image and only the data of the boundary of the moving image is modulated such that a discontinuous artifact is prevented from being generated in the boundary of the moving image according to the motion speed of the moving image, it is possible to display a high-definition stereoscopic moving image without motion blurring. 
     Therefore, according to the present invention, it is possible to minimize a motion blurring phenomenon of a display image and to improve the display quality of the display image. 
     It will be apparent to those skilled in the art that various modifications can be made in the present invention without departing from the spirit or scope of the invention. Thus, it is intended that the present invention covers the modifications and variations of this invention provided they come within the scope of the appended claims and their equivalents.