Abstract:
An apparatus and a method for compensating image blocking artifacts are capable of eliminating image blocking artifacts occurring in consecutively input image signals, in advance. The apparatus for compensating image blocking artifacts has a video signal comparing unit for comparing gradation values of video signals which are consecutively input at a predetermined time interval, the video signal comparing unit determining if the difference between the gradation values meets a certain condition, as the image blocking artifacts occur in the consecutively input video signals; and an operation processing unit for removing the image blocking artifacts by adding/subtracting the gradation values of the input video signals when it is determined that the image blocking artifacts occur. By eliminating the image blocking artifacts occurring in the consecutively input image signals, the image blocking artifact compensating apparatus can provide a clearer video on the liquid crystal display.

Description:
BACKGROUND OF THE INVENTION  
         [0001]    1. Field of the Invention  
           [0002]    The present invention generally relates to an apparatus and method for compensating image blocking artifacts, and more particularly to an apparatus and a method for compensating image blocking artifacts occurring in display systems like Liquid Crystal Displays (LCD). The present application is based on Korean Patent Application No. 2001-65226, which is incorporated herein by reference.  
           [0003]    2. Description of the Prior Art  
           [0004]    Generally, display devices like liquid crystal displays (LCD), plasma display systems, and light-emitting diodes (LED) display images by controlling on/off of a plurality of pixels arranged in matrixes. Such display devices, which perform the on/off control on the respective pixels, are only capable of displaying images in two ways, namely light on/light off or transparent/nontransparent.  
           [0005]    [0005]FIG. 1 is a view schematically showing a cell structure of a general LCD. Referring to FIG. 1, a plurality of pixels are arranged in a 4×9 matrix. Each pixel is categorized into a major pixel  11  and a minor pixel  13 . The ratio of the major pixel  11  to the minor pixel  13  in regard to the intensity of radiation is 8:1, and the major pixel  11  and the minor pixel  13  are driven in time series by the expression of gradation. For example, if the gradation is fifteen (15), the minor pixel  13  is driven fifteen ( 15 ) times. If the gradation is sixteen (16), the major pixel  11  is driven two (2) times. In the example shown in FIG. 1, minor pixels  13  are driven from the first to third columns, the major pixels  11  are driven from the fourth to the sixth columns, and the minor pixels  13  are driven from the seventh to the ninth columns.  
           [0006]    Conventionally, each pixel is driven in time series, and occasionally, a situation occurs in which the consecutively driven pixels are perceived by the user&#39;s eyes with a gradation that is different from the actual gradation. Such a situation will be called ‘image blocking artifacts’ hereinbelow. When the image blocking artifacts happen, the user may perceive two consecutive columns as one column. And he/she may perceive the respective columns of pixels by the order of 15 gradation, 15 gradation, 31 gradation, 16 gradation, 0 gradation, 15 gradation and 15 gradation. Accordingly, from the user&#39;s view, the user will perceive dark  31  gradation at an instance when the major pixel  11  is driven after the minor pixel  13  is driven. Then, at the instance when the minor pixel  13  is driven after the major pixel  11  is driven, the user will perceive 0 gradation, which will cause the interruption between lines.  
         SUMMARY OF THE INVENTION  
         [0007]    The present invention has been made to overcome the above-mentioned problems of the prior art. Accordingly, it is an object of the present invention to provide an apparatus and a method for compensating image blocking artifacts, which are caused due to the structure of a display device like a liquid crystal display.  
           [0008]    The above object is accomplished by an apparatus for compensating image blocking artifacts according to the present invention, including a video signal comparing unit for comparing gradation values of video signals which are consecutively input at a predetermined time interval, the signal comparing unit determining if the difference between the gradation values meets a certain condition, as the image blocking artifacts occur in the consecutively input video signals; and an operation processing unit for removing the image blocking artifacts by adding/subtracting the gradation values of the input video signals when it is determined that the image blocking artifacts occur.  
           [0009]    The video signal comparing unit comprises an index generating unit for generating an index for commanding an adding/subtracting of the gradation values of the video signals that are input to the operation processing unit when it is determined that the image blocking artifacts occur.  
           [0010]    The operation processing unit comprises a video signal modulating unit for modulating the input video signals, so that resultant gradation values of adding/subtracting can be output.  
           [0011]    When a gradation value of a preceding video signal of the consecutively input video signals meets a certain condition, the video signal comparing unit compares the gradation values of the consecutively input video signals.  
           [0012]    When a remainder of dividing the gradation value of the preceding video signal by a predetermined number equals a predetermined value, the video signal comparing unit compares the gradation values of the consecutively input video signals.  
           [0013]    According to the present invention, the apparatus for compensating image blocking artifacts compares gradation values of sequentially input video signals. When there is a possibility of having image blocking artifacts, the apparatus minimizes the image blocking artifacts by adding or subtracting a predetermined gradation value with respect to the gradation value of the input signals.  
           [0014]    According to the present invention, a method for compensating image blocking artifacts comprises the steps of comparing gradation values of video signals that are consecutively input at a predetermined time interval; determining when a difference between the gradation values meets a certain condition, as the image blocking artifacts occur in the video signals; and when determining that the image blocking artifacts occur, removing the blocking artifacts by adding/subtracting the gradation values of the consecutively input video signals. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0015]    The above-mentioned object and the feature of the present invention will be more apparent by describing the preferred embodiment of the present invention by referring to the appended drawings, in which:  
         [0016]    [0016]FIG. 1 is a view schematically showing the cell structure of a conventional liquid crystal display;  
         [0017]    [0017]FIG. 2 is a block diagram schematically showing an apparatus for compensating image blocking artifacts according to the present invention;  
         [0018]    [0018]FIG. 3 is a view showing a variable region of a gradation that is displayable in pixels; and  
         [0019]    [0019]FIG. 4 is a flowchart for illustrating a process of compensating image blocking artifacts of FIG. 2. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT  
       [0020]    From now on, the present invention will be described in greater detail by referring to the appended drawings.  
         [0021]    [0021]FIG. 2 schematically shows the apparatus for compensating the image blocking artifacts according to the present invention. As shown in FIG. 2, the image blocking artifacts compensating apparatus includes an image delay unit  21 , a video signal comparing unit  23  and an operation processing unit  25 . The video signal comparing unit  23  has an index generating unit  23   a . Also, the operation processing unit  25  has a video signal modulating unit  25   a.    
         [0022]    The image delay unit  21  delays an input video signal by a predetermined time period. The predetermined delay time made by the image delay unit  21  is preferably set to be as much as the time interval at which each frame of the video signal is input. Further, it is preferred that the image delay unit  21  be constructed in a first-in first-out type buffer, in which the image delay unit  21  temporarily stores the input video signal for a predetermined time before outputting the signal.  
         [0023]    The video signal comparing unit  23  compares the gradation values of the video signals that are consecutively input at a predetermined time interval. The video signal comparing unit  23  determines if the difference between the compared video signals meets a certain condition, as there are image blocking artifacts occurring between the consecutively input video signals.  
         [0024]    When it is determined by the video signal comparing unit  23  that there are image blocking artifacts occurring in the consecutively input video signals, the index generating unit  23   a  generates an index that gives a command to add/subtract the gradation values of the video signals that are input to the operation processing unit  25 , to eliminate the possibility of having the image blocking artifacts.  
         [0025]    When it is determined that there is a possibility of having image blocking artifacts in the consecutively input video signals, the operation processing unit  25  adds/subtracts the gradation values of the input video signals, to thereby eliminate the possibility of having the image blocking artifacts.  
         [0026]    When it is determined that there is a possibility of having image blocking artifacts in the consecutively input video signals, the video signal modulating unit  25   a  modulates the input video signals so that the input video signals can be output with the resultant gradation values of adding or subtracting by the operation processing unit  25 . FIG. 3 shows the available range of gradation values that can be added/subtracted to modulate the input video signals, when it is determined that there is a possibility of having the image blocking artifacts in the consecutively input video signals. The general range of gradation is between  14  and  241 .  
         [0027]    [0027]FIG. 4 is a flowchart showing the process of compensating the image blocking artifacts of FIG. 2. Referring to FIG. 4, first, video signals in a frame unit are input to the image blocking artifact compensating apparatus consecutively (step S 103 ). As mentioned above, the input video signals have the gradation value ranging from 14 to 241. Among the input video signals, the preceding input signals are delayed for a predetermined time so that the preceding signals can be input to the video signal comparing unit  23  together with the following input signals.  
         [0028]    The image delay unit  21  delays the input video signals for a predetermined time (step S 103 ). The image delay unit  21  can be achieved by a first-in/first-out type buffer. The video signals, which are delayed by the image delay unit  21 , are input to the video signal comparing unit  23  together with the following input signals that are not delayed. The delayed input video signals and non-delayed input video signals are input to the video signal comparing unit  23  together with each other. Alternatively, once-delayed and twice-delayed input video signals can be input to the video signal comparing unit  23 . The video signals, which are consecutively input to the video signal input unit  23 , have to be input to the video signal comparing unit  23  at the same time.  
         [0029]    The video signal comparing unit  23  determines whether the remainder of dividing the gradation value of the preceding input video signal corresponds to a certain value or not (steps S 105 , S 113 , S 119 , S 125 ). If the remainder of dividing the gradation value of the preceding input video signal corresponds to the certain value, the video signal comparing unit  23  determines whether the resultant gradation value of adding or subtracting a certain gradation value with respect to the gradation value of the following input video signal corresponds to the gradation value of the preceding input video signal or not (steps S 107 , S 115 , S 121 , S 127 ). In other words, the video signal comparing unit  23  determines whether the difference between the gradation value of the preceding input video signal and the gradation value of the following input video signal meets a certain condition or not.  
         [0030]    When it is determined that the resultant gradation value of adding or subtracting a certain gradation value with respect to the gradation value of the following input video signal corresponds to the gradation value of the preceding input video signal, i.e., when it is determined that the difference between the gradation value of the preceding input video signal and the gradation value of the following input video signal corresponds to a certain value, the index generating unit  23   a  generates the respective indexes (steps S 109 , S 117 , S 123 , S 129 ). The indexes generated by the index generating unit  23   a  are transmitted to the operation processing unit  25 . The video signal comparing unit  23  transmits the preceding input video signal and the following input video signal to the operation processing unit  25  so that the image blocking artifacts occurring in the consecutively input video signals can be compensated.  
         [0031]    The operation processing unit  25  receives the indexes from the index generating unit  23   a , and adds/subtracts the gradation value of the input video signal to eliminate the possibility of having the image blocking artifacts in the input video signals. At this time, based on the received indexes, the operation processing unit  25  determines whether to add or subtract the gradation value of the input video signals. Also, the video signal modulating unit  25   a  of the operation unit  25  modulates the input video signals so that the input video signals can be output with the gradation values of the video signals that are added/subtracted by the operation processing unit  25  (step S 111 ). Either the preceding input video signal or the following input video signal can be modulated. Alternatively, both of the preceding and following input video signals can be modulated.  
         [0032]    When it is determined that the resultant gradation value of adding or subtracting a certain gradation value with respect to the gradation value of the following input video signal does not meet the gradation value of the preceding input video signal, the video signal comparing unit  23  terminates the image blocking artifact compensating process, and stands by for the process of compensating the image blocking artifacts of the next input video signals.  
         [0033]    When it is determined that the remainder of dividing the gradation value of the preceding input video signal by a predetermined value does not correspond to any of the preset values, the video signal comparing unit  23  terminates the process of compensating the image blocking artifacts of the input video signal, and stands by for the process of compensating the image blocking artifacts with respect to the next input video signals.  
         [0034]    [0034]FIG. 4 shows an example of image blocking artifact compensation, which is performed when the remainder of dividing the gradation values of the input video signal by sixteen (16) corresponds to any of 14, 15, 0 and 1. It is based on the fact that there is a high possibility of having the image blocking artifacts when the remainders of dividing the gradation values of the consecutively input video signals by sixteen (16) falls into the range of +2˜−2. However, it does not necessarily mean that the image blocking artifacts are compensated only when the remainder of dividing the gradation value of the input video signal by sixteen (16) corresponds to any of 14, 15, 0 and 1.  
         [0035]    As described above, whether the difference between the gradation values of the consecutively input video signals is two (2) or three (3) is determined according to the remainder of dividing the gradation values of the input video signals by sixteen (16). However, it should be noted that it is just based on the fact that the difference of 2 or 3 between the gradation values of the consecutively input video signals indicates a high possibility of having the image blocking artifacts. Accordingly, one does not necessarily have to use certain limited figures to compensate the image blocking artifacts.  
         [0036]    As described above, the image blocking artifact compensating apparatus according to the present invention reduces occurrence of image blocking artifacts by compensating to prevent occurrence of the image blocking artifacts between the video signals that are consecutively input in a frame unit.  
         [0037]    Although the preferred embodiment of the present invention has been described, it will be understood by those skilled in the art that the present invention should not be limited to the described preferred embodiment, but various changes and modifications can be made within the spirit and scope of the present invention as defined by the appended claims.