Abstract:
An exemplary LCD includes a frame memory configured for receiving a plurality of first gradations of current frame and outputting a plurality of second gradations of preceding frame pre-stored therein; a comparator configured for receiving, comparing the first gradations with the second gradation to generate a comparison result; a luminance detector configured for detecting a luminance degree of each of pixel according to the gradations of current frame; a calculator configured for calculating a complication degree of a picture to be displayed in current frame; and a gradation processor configured for receiving the first gradations of current frame to be displayed on the LCD panel, generating a plurality of pairs of compensating gradations according to the gradation of each pixel, and selecting one pair of the compensating gradations to be outputted to the LCD panel according to a received comparison result, a received luminance degree, and a received complication degree.

Description:
FIELD OF THE INVENTION 
       [0001]    The present invention relates to a liquid crystal display (LCD) device configured to reduce image aberrations, and a method for driving such kind of LCD. 
       GENERAL BACKGROUND 
       [0002]    Because typical LCD devices have the advantages of portability, low power consumption, and low radiation, they have been widely used in various portable information products such as notebooks, personal digital assistants (PDAs), video cameras, and the like. Furthermore, LCD devices are considered by many to have the potential to completely replace CRT (cathode ray tube) monitors and televisions. On the other hand, the display mode of typical LCD devices is hold-type, and the response speed of liquid crystal molecules employed in such LCD devices may be too slow. As a result, the residual image phenomenon may occur when motion pictures are displayed on LCD devices. 
         [0003]    In order to solve the above-described problems, a typical method employed for eliminating the residual image of LCD devices is the so-called black image insertion method. In the black image insertion method, a frame is divided into a first sub-frame for displaying the actual image and a second sub-frame for displaying a black image. However, because a black image is displayed between every two actual images, a viewer may easily perceive a flicker phenomenon. Furthermore, because a black image is displayed in each second sub-frame, the brightness of the images displayed by the LCD device is correspondingly reduced. 
         [0004]    Referring to  FIG. 4 , a typical LCD  1  configured for eliminating the above-described problems of flicker and low brightness is shown. The LCD  1  includes a driving circuit  10  and an LCD panel  14 . The driving circuit  10  includes a frame memory  11 , a comparator  12 , and a gradation processor  13 . The frame memory  11  has a plurality of gradations V(m) of a number m (0≦m≦59, m is a natural number) frame pre-stored therein. The frame memory  11  provides the gradations V(m) of the number m frame to the comparator  13 . After the gradations V(m) are provided to the comparator  13 , the frame memory  11  receives a plurality of gradations V(m+1) of a number m+1 frame and stores the gradations V(m+1) therein. 
         [0005]    It is assumed that the LCD panel  14  of the LCD  1  has a resolution of (I, J). In other words, the LCD panel  14  includes a pixel matrix including I (I is a natural number) rows and J (J is a natural number) columns. The gradations V(m) include a plurality of gradations V(m, i, j) corresponding to the pixel matrix of the LCD  1 , each gradation V(m, i, j) represents a gradation of a number m frame to be provided to a pixel(i, j) located in a number i (1≦i≦I) row and in a number j (1≦j≦J) column of the pixel matrix. The gradations V(m+1) include a plurality of gradations V(m+1, i, j) corresponding to the pixel matrix, wherein each gradation V(m+1, i, j) represents another gradation of a number m+1 frame to be provided to the same pixel(i, j) of the pixel matrix. 
         [0006]    The comparator  12  receives the gradations V(m) of the number m frame and the gradations V(m+1) of the number m+1 frame, compares the gradations V(m, i, j) with the gradations V(m+1, i, j), and provides a comparison result to the gradation processor  13 . 
         [0007]    The gradation processor  13  receives the gradations V(m+1) of the number m+1 frame that are prepared to be displayed on the LCD panel  14 , and generates two pairs of compensating gradations according to the gradation V(m+1, i, j) of each pixel. Each pair of compensating gradations includes a primary compensating gradation “A” and a secondary compensating gradation “B”. The gradation processor  13  selects one of the pairs of compensating gradations according to the received comparison result, and then provides the primary compensating gradation “A” of the selected pair of compensating gradations to the LCD panel  14  in an earlier period of the m+1 frame, and provides the secondary compensating gradation “B” of the selected pair of compensating gradations to the LCD panel  14  in a later period of the m+1 frame. 
         [0008]    Referring to  FIG. 5 , is a graph of luminance versus time, showing two luminance curves for the LCD of  FIG. 4 . Corresponding to each pixel(i, j). the primary compensating gradation  1 A and the secondary compensating gradation  1 B are respectively equal to the gradation V(m+1, i, j) in the earlier period of a frame and in the later period of the frame. In addition, the primary compensating gradation  2 A is greater than the gradation V(m+1, i, j), and the secondary compensating gradation  2 B is less than the gradation V(m+1, i, j). An average value of the primary compensating gradation  2 A and the secondary compensating gradation  2 B is equal to the gradation V(m+1, i, j). 
         [0009]    A driving method for the LCD  1  includes the following steps: 
         [0010]    step a. providing a plurality of gradations V(m+1) of a number m+1 frame respectively to the frame memory  11  and the comparator  12 , and at the same time, providing all the gradations V(m) of the number m frame to the comparator  12  from the frame memory  11 ; 
         [0011]    step b. comparing the gradations V(m, i, j) with the gradations V(m+1, 1, j) respectively corresponding to each pixel by the comparator  12 , and providing a comparison result to the gradation processor  13 ; 
         [0012]    step c. when V(m, i, j)=V(m+1, i, j)—in other words, the pixel(i, j) in a number i row and in a number j column displays a still picture in the number m+1 frame—the gradation processor  13  provides the primary compensating gradation  1 A to the LCD panel  14  in the earlier period of the number m+1 frame, and provides the secondary compensating gradation  1 B to the LCD panel  14  in the later period of the number m+1 frame. When V(m, i, j)≠V(m+1, i, j)—in other words, the pixel(i, j) displays a moving picture in the number m+1 frame—the gradation processor  13  provides the primary compensating gradation  2 A to the LCD panel  14  in the earlier period of the number m+1 frame, and provides the secondary compensating gradation  2 B to the LCD panel  14  in the later period of the number m+1 frame. 
         [0013]    Because the average value of the primary compensating gradation “A” and the secondary compensating gradation “B” is equal to the gradation V(m+1) of the number m+1 frame, the luminance of each pixel of the LCD panel  14  can be maintained to correspond with the input image data. However, when a moving picture is displayed on the LCD panel  14 , the primary compensating gradation  2 A and the secondary compensating gradation  2 B are provided to the LCD panel  14 , and a bright picture and a dim picture are sequentially displayed on the LCD panel  14 . Thus a viewer may easily perceive flicker of images displayed on the LCD panel  14 . 
         [0014]    It is desired to provide a new LCD which can overcome the above-described deficiencies. It is also desired to provide a method for driving such LCD. 
       SUMMARY 
       [0015]    In one preferred embodiment, an LCD includes an LCD panel, the LCD includes a frame memory configured for receiving a plurality of first gradations of a current frame to be displayed and outputting a plurality of second gradations of a preceding frame pre-stored therein; a comparator configured for receiving the first gradations of the current frame and the second gradations of the preceding frame, and comparing the first gradations with the second gradations to generate a comparison result; a luminance detector configured for detecting a luminance degree of each of pixels of the LCD panel to be displayed in the current frame according to the gradations of the current frame; a calculator configured for calculating a degree of complication of a picture to be displayed in the current frame; and a gradation processor configured for receiving the first gradations of the current frame to be displayed on the LCD panel, generating a plurality of pairs of compensating gradations according to the first gradation of each pixel, and selecting one pair of the compensating gradations to be outputted to the LCD panel according to the comparison result, a received luminance degree, and the complication degree; wherein the calculator is further configured for providing the complication degree to the gradation processor. 
         [0016]    Other novel features and advantages will become more apparent from the following detailed description when taken in conjunction with the accompanying drawings. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0017]      FIG. 1  is an abbreviated block diagram of certain components of an LCD according to an exemplary embodiment of the present invention, the LCD including a pixel matrix capable of displaying a plurality of pixels. 
           [0018]      FIG. 2  is an abbreviated relationship table utilized in the LCD of  FIG. 1 , the relationship table including a plurality of pairs of compensating gradations. 
           [0019]      FIG. 3  is a graph of luminance versus time, showing several of a plurality of luminance curves, each luminance curve depicting one of the pairs of compensating gradations of the relationship table of  FIG. 2 . 
           [0020]      FIG. 4  is a block diagram of certain components of a conventional LCD that is configured for eliminating flicker and low brightness, the LCD including an LCD panel. 
           [0021]      FIG. 5  is a graph of luminance versus time, showing two luminance curves for the LCD of  FIG. 4 , each luminance curve depicting one of two pairs of compensating gradations provided to the LCD panel of the LCD. 
       
    
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
       [0022]    Reference will now be made to the drawings to describe various embodiments of the present invention in detail. 
         [0023]    Referring to  FIG. 1 , an LCD  2  according to an exemplary embodiment of the present invention is shown. The LCD  2  includes an LCD panel  26  and a driving circuit  20  for driving the LCD panel  26 . The driving circuit  20  includes a frame memory  21 , a comparator  22 , a luminance detector  23 , a calculator  24 , and a gradation processor  25 . The LCD panel  26  includes a pixel matrix. 
         [0024]    The frame memory  21  has a plurality of gradations V(m) of a number m (0≦m≦59, m is a natural number) frame pre-stored therein. The frame memory  21  receives a plurality of gradations V(m+1) of a number m+1 frame, and provides the gradations V(m) to the comparator  22 . 
         [0025]    The luminance detector  23  is configured for detecting a degree of luminance (hereinafter, “luminance degree”) of each pixel of the pixel matrix of the LCD panel  26  in the number m+1 frame. 
         [0026]    It is assumed that the LCD panel  26  has a resolution of 1024×768. In other words, the pixel matrix of the LCD panel  26  includes pixels arranged in 1024 columns and 728 rows. The LCD panel  26  is defined to include 64 display areas. Each display area is defined by a sub pixel matrix having 12 rows and 16 columns of pixels. The gradations V(m) includes a plurality of gradations V(m, i, j) corresponding to the pixel matrix of the LCD  2 . Each gradation V(m, i, j) is provided to a pixel(i, j) located in a number i (1≦i≦728) row and in a number j (1≦j≦1024) column of the pixel matrix in the number m frame. 
         [0027]    The calculator  22  calculates a degree of complication (hereinafter, “complication degree”) of a picture to be displayed on each display area in the number m+1 frame, and provides the complication degree to the gradation processor  25 . The complication degree can be calculated by summing up gradations V(m+1) of the number m+1 frame to be provided to each sub pixel matrix. 
         [0028]    The comparator  22  receives the gradations V(m) of the number m frame and the gradation V(m+1) of the number m+1 frame, compares the gradations V(m, i, j) with the gradations V(m+1, i, j) corresponding to each pixel, and provides a comparison result to the gradation processor  25 . 
         [0029]    The gradation processor  25  receives the gradations V(m+1) of the number m+1 frame, and generates a plurality of pairs of compensating gradations according to the gradation V(m+1, i, j) of each pixel. Each pair of compensating gradations includes a primary compensating gradation “A” and a secondary compensating gradation “B”. The gradation processor  25  selects one of the pairs of the compensating gradations according to the comparison result, a degree of luminance of each pixel in the number m+1 frame, and the complication degree of the picture to be displayed on the sub pixel matrix having the pixel in the number m+1 frame, and then provides the primary compensating gradation “A” of the selected pair of compensating gradations to the LCD panel  26  in an earlier period of the number m+1 frame, and provides the secondary compensating gradation “B” of the selected pair of compensating gradations to the LCD panel  26  in a later period of the number m+1 frame. An average value of the primary compensating gradation “A” and the secondary compensating gradation “B” of each pair of compensating gradations is equal to the gradation V(m+1, i, j). 
         [0030]    Referring to  FIG. 2 , this is a relationship table showing relations between the comparison results of a pixel(i, j), the luminance degrees of the pixel(i, j) in the number m+1 frame, the complication degree of a picture displayed on the sub pixel matrix including the pixel (i, j) in the number m+1 frame, and the plurality of pairs of compensating gradations. The luminance degree of each pixel(i, j) is divided into X(2≦X) levels. The complication degrees of a picture displayed on the sub pixel matrix are divided into Y (2≦Y) levels. The amount of the pairs of compensating gradations is equal to X+Y. The higher the level of the luminance degree, the brighter the pixel. The higher the level of the compensating gradation is, the more complicated the picture displayed on the sub pixel matrix including the pixel is. 
         [0031]    Referring to  FIG. 3 , this shows several of a plurality of luminance curves, each luminance curve depicting one of the pairs of compensating gradations of the relationship table. The plurality of pairs of compensating gradations includes a number  1  pair of compensating gradations, a number  2  pair of compensating gradations, . . . , and so on through to a number X+Y pair of compensating gradations, with the succeeding pairs of compensating gradations having gradually increasing amplitudes. The primary compensating gradation  1 A and the secondary compensating gradation  1 B of the number  1  pair of compensating gradations are respectively equal to the gradations V(m+1, i, j) in the earlier period of the number m+1 frame and in the later period of the number m+1 frame. The primary compensating gradations  2 A˜(X+Y)A are greater than the gradation V(m+1, i, j), and the secondary compensating gradations  2 B˜(X+Y)B are less than the gradation V(m+1, i, j). An average value of the primary compensating gradation  2 A˜(X+Y)A and the secondary compensating gradation  2 B˜(X+Y)B of each pair of compensating gradations is equal to the gradation V(m+1, i, j). 
         [0032]    An exemplary method for driving the LCD  2  includes the following steps: 
         [0033]    step a. providing a plurality of gradations V(m+1) of the number m+1 frame respectively to the frame memory  21 , the comparator  22 , the luminance detector  23 , the calculator  24 , and the gradation processor  25 , and at the same time, providing all the gradations V(m) of the number m frame to the comparator  22  from the frame memory  21 . 
         [0034]    step b. comparing the gradations V(m, i, j) with the gradations V(m+1, i, j) corresponding to each pixel(i, j) by the comparator  22 , and providing a comparison result to the gradation processor  25 , and at the same time, providing a level of luminance degree to the gradation processor  25  by the luminance detector  23 , and at the same time, providing a level of the complication degree to the gradation processor  25  by the calculator  24 . 
         [0035]    step c. selecting a pair of the compensating gradations according to the comparison result, the level of the luminance degree of each of pixel, and the level of the complication degree of a picture to be displayed on the sub pixel matrix including the pixel(i, j) by the gradation processor  25 , and then providing the primary compensating gradation “A” of the selected pair of compensating gradations to the LCD panel  26  in an earlier period of the number m+1 frame, and providing the secondary compensating gradation “B” of the selected pair of compensating gradations to the LCD panel  26  in a later period of the number m+1 frame. 
         [0036]    A typical method for selecting one of the pairs of the compensating gradations is as follows. When V(m, i, j)=V(m+1, i, j)—in other words, the pixel(i, j) in number i row and in number j column displays a still picture in the number m+1 frame—the gradation processor  25  selects the number  1  pair of the compensating gradations, and provides the primary compensating gradation  1 A to the LCD panel  26  in the earlier period of the number m+1 frame, and provides the secondary compensating gradation  1 B to the LCD panel  26  in the later period of the number m+1 frame. When V(m, i, j)≠V(m+1, i, j)—in other words, the pixel(i, j) displays a moving picture in the number m+1 frame—the method includes the following steps: 
         [0037]    When the luminance degree of the pixel(i, j) is equal to level  1  which indicates the pixel(i, j) is the dimmest, and the complication degree of a picture displayed on the sub pixel matrix including the pixel(i, j) is equal to level Y which indicates that the picture displayed on the sub pixel matrix including the pixel(i, j) is the most undistinguishable, the gradation processor  25  selects a number X+Y−1 pair of the compensating gradations, and provides the primary compensating gradation (X+Y−1)A of the number X+Y−1 pair of the compensating gradations to the LCD panel  26  in the earlier period of the number m+1 frame, and provides the secondary compensating gradation (X+Y−1)B of the number X+Y−1 pair of the compensating gradations to the LCD panel  26  in the later period of the number m+1 frame. An amplitude of the number X+Y−1 pair of the compensating gradations is defined to be the greatest to make the picture displayed on the sub pixel matrix including the pixel(i, j) most indistinguishable. 
         [0038]    When the luminance degree of the pixel(i, j) is equal to level  1 , and the complication degree of a picture displayed on the sub pixel matrix including the pixel(i, j) is equal to level Y−1, the number X+Y−2 pair of the compensating gradations is selected by the gradation processor  25 . The amplitude of the number X+Y−1 pair of the compensating gradations is greater than that of the number X+Y−2 pair of the compensating gradations. 
         [0039]    When the luminance degree of the pixel(i, j) is equal to level  1 , and the complication degree of a picture displayed on the sub pixel matrix including the pixel(i, j) is equal to level  1 , the number X pair of the compensating gradation is selected. 
         [0040]    When the luminance degree of the pixel(i, j) is equal to level  2 , and the complication degree of a picture displayed on the sub pixel matrix including the pixel(i, j) is equal to level Y, the number X+Y−2 pair of the compensating gradation is selected. 
         [0041]    When the luminance degree of the pixel(i, j) is equal to level  2 , and the complication degree of a picture displayed on the sub pixel matrix including the pixel(i, j) is equal to level Y−1, the number X+Y−3 pair of the compensating gradation is selected. 
         [0042]    When the luminance degree of the pixel(i, j) is equal to level  2 , and the complication degree of a picture displayed on the sub pixel matrix including the pixel(i, j) is equal to level  1 , the number X−1 pair of the compensating gradation is selected. 
         [0043]    When the luminance degree of the pixel(i, j) is equal to level X which indicates the pixel(i, j) is the brightest, and the complication degree of a picture displayed on a sub pixel matrix including the pixel(i, j) is equal to level  1 , the number  2  pair of the compensating gradation is selected. An amplitude of the number  2  pair of the compensating gradation is greater than that of the number  1  pair of the compensating gradations and is less than that of the number  3  pair of the compensating gradations. 
         [0044]    Because the LCD  2  includes the gradation processor  25  configured for generating a plurality of pairs of compensating gradation according to each gradation V(m+1. i, j), and selecting one pair of the compensating gradation according to a comparison result, a level of a luminance degree of each pixel, and a level of a complication degree of a picture displayed on a sub pixel matrix including the pixel, a flicker phenomenon and a residual image of the LCD  2  can be eliminated or at least depressed. Furthermore, an average value of the primary compensating gradation (X+Y)A and the secondary compensating gradation (X+Y)B of each pair of compensating gradations is equal to the gradations V(m+1, i, j), and the brightness of the LCD  2  is correspondingly not decreased. 
         [0045]    It is to be understood, however, that even though numerous characteristics and advantages of the preferred embodiments have been set out in the foregoing description, together with details of the structures and functions of the embodiments, the disclosure is illustrative only; and that changes may be made in detail, especially in matters of arrangement of parts within the principles of present invention to the full extent indicated by the broad general meaning of the terms in which the appended claims are expressed.