Patent Publication Number: US-2007109240-A1

Title: Display apparatus for controlling the brightness values of a plurality of light sources and method of controlling the same

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS  
      This application claims priority from Korean Patent Application No. 2005-0109754, filed on Nov. 16, 2005, in the Korean Intellectual Property Office, the disclosure of which is incorporated herein by reference.  
     BACKGROUND OF THE INVENTION  
      1. Field of Invention  
      The present invention relates to a display apparatus and a method of controlling the same, and more particularly, to a display apparatus having a plurality of light sources that are separately driven, and a method of controlling the same.  
      2. Description of the Related Art  
      Recently, flat panel displays (FPDs), such as liquid crystal displays (LCDs), display apparatuses that use plasma display panels (PDPs), and display apparatuses that use organic light emitting diodes (OLEDs), have been widely developed and used to replace cathode ray tubes (CRTs).  
      In general, a backlight including a linear lamp used as a light source is widely used for a display apparatus. The conventional display apparatus that uses the backlight including the linear lamp cannot control the brightness of a portion of an image. Therefore, it is difficult to vividly display an image signal having partially high brightness, such as an image containing an explosion scene.  
      Recently, a plurality of light sources that can be separately driven, such as light emitting diodes (LEDs), has been developed. So, a screen of a display apparatus is partitioned into a plurality of blocks, and light sources corresponding to the blocks can be separately driven.  
      However, such a display apparatus has a problem in that, depending upon the image, the difference in the brightness between the blocks of the same frame or between the blocks of the different frames may be large. In the case of the large difference in brightness between the blocks in the same frame, there may be an undesirable step difference. In the case of large differences in brightness between the blocks of the different frames, there may be undesirable screen flicker. Either of the step difference or the screen flicker may result in deterioration of image quality.  
     SUMMARY OF THE INVENTION  
      Accordingly, it is an aspect of the present invention to provide a display apparatus capable of controlling at least one of a difference in brightness between adjacent blocks and a difference in brightness between frames to improve image quality, and a method of controlling the same.  
      The foregoing and/or other aspects of the present invention can be achieved by a display apparatus comprising a display panel and a plurality of light source units corresponding to the blocks of the display panel, each of the plurality of light source units having one or more light source elements, comprising a light source driver for separately driving the light source units; a brightness level operator for operating brightness levels of image data applied to the display panel by blocks; a block brightness level controller for controlling at least one of the brightness levels of the blocks so that the difference in brightness level between at least one of the adjacent block falls within a predetermined range; and a controller for controlling the light source driver to drive the light source unit based on the controlled brightness level.  
      According to the embodiment of the present invention, the blocks comprise a first block and a second block adjacent to the first block, and wherein, when a difference between a first brightness level corresponding to the first block and a second brightness level corresponding to the second block is out of a predetermined range, the block brightness level controller changes at least one of the first brightness level and the second brightness level to a predetermined brightness level based on the difference.  
      According to the embodiment of the present invention, the brightness level controller calculates the brightness levels of the image data corresponding to frames, and further comprising a frame brightness level controller for controlling a difference in brightness level between consecutive preceding and current frames and controlling the brightness level of the receding frame so that the difference falls within a predetermined range.  
      According to the embodiment of the present invention, the frame brightness level controller controls the difference in brightness level between the consecutive preceding and current frames corresponding to at least one block and controls the brightness level of the current frame corresponding to at least one block so that the difference falls within a predetermined range.  
      According to the embodiment of the present invention, the frame brightness level controller controls the brightness level of the current frame to be between the brightness level of the preceding frame and the brightness level of the current frame.  
      According to the embodiment of the present invention, the frame brightness level controller controls the brightness level of the current frame to be close to the brightness level of the preceding frame as the difference in brightness level between the preceding frame and the current frame gets smaller.  
      According to the embodiment of the present invention, the light source elements are provided all over the back surface of the display panel.  
      According to the embodiment of the present invention, the light source elements are light emitting diodes (LED).  
      The foregoing and/or other aspects of the present invention can be achieved by providing a display apparatus having light source units, comprising: alight source driver for driving the light source units; a brightness level controller for controlling brightness levels of image data corresponding to frames; a frame brightness level controller for controlling a difference in brightness level between consecutive preceding and current frames and controlling the brightness level of the receding frame so that the difference falls within a predetermined range; and a controller for controlling the light source driver to drive the light source unit based on the controlled brightness level.  
      According to the embodiment of the present invention, the brightness level controller controls the brightness levels of the image data by blocks; and the frame brightness level controller operates the difference in brightness level between consecutive preceding and current frames corresponding to at least one block and controls the brightness level of the current frame corresponding to at least one block so that the difference falls within a predetermined range.  
      According to the embodiment of the present invention, the frame brightness level controller controls the brightness level of the current frame to be between the brightness level of the current frame and the brightness level of the current frame.  
      According to the embodiment of the present invention, the frame brightness level controller controls the brightness level of the current frame to be close to the brightness level of the preceding frame as the difference in brightness level between the preceding frame and the current frame gets smaller.  
      The foregoing and/or other aspects of the present invention can be achieved by providing a method of controlling a display apparatus comprising a plurality of light source units, the method comprising controlling brightness levels of image data applied to the display panel by blocks; controlling difference in the brightness level between adjacent blocks; wherein if the difference is out of a predetermined range, controlling at least one of the brightness levels by blocks so that the difference falls within a predetermined range; and driving the light source unit based on the controlled brightness level.  
      According to the embodiment of the present invention, the blocks comprise a first block and a second block adjacent to the first block, and the controlling the at least one of the brightness levels comprises changing at least one of a first brightness level corresponding to the first block and a second brightness level corresponding to the second block to a predetermined brightness level set based on the difference between the first brightness level and the second brightness level so that the difference falls within a predetermined range.  
      According to the embodiment of the present invention, the method further comprises: calculating the brightness levels of the image data corresponding to the frames; controlling a difference in brightness level between consecutive preceding and current frames; and controlling the brightness level of the current frame so that the difference falls within a predetermined range.  
      According to the embodiment of the present invention, the controlling the difference in brightness level between the preceding and current frames comprises operating the difference in brightness level between the consecutive preceding and current frames corresponding to at least one block, and the controlling the brightness level of the current frame comprises controlling the brightness level of the current frame corresponding to at least one block so that the difference falls within a predetermined range.  
      According to the embodiment of the present invention, the controlling the brightness level comprises controlling the brightness level of the current frame to be close to the brightness level of the preceding frame as the difference in brightness level between the preceding frame and the current frame gets smaller.  
      The foregoing and/or other aspects of the present invention can be achieved by providing a method of controlling a display apparatus having a light source unit, the method comprising: controlling brightness levels of image data corresponding to frames; operating a difference in brightness between consecutive preceding and current frames; when the difference is out of a predetermined range, controlling the brightness level of the current frame so that the difference falls within a predetermined range; and driving the light source unit based on the controlled brightness level.  
      According to the embodiment of the present invention, the operating the brightness levels comprises controlling the brightness levels of the image data by blocks, the controlling the difference in brightness level between the preceding and current frames comprises controlling the difference in brightness level between consecutive preceding and current frames corresponding to at least one block, and the controlling the brightness levels comprises controlling the brightness level of the current frame corresponding to at least one block so that the difference falls within a predetermined range.  
      According to the embodiment of the present invention, the controlling the brightness levels comprises controlling the brightness level of the current frame to be close to the brightness level of the preceding frame as the difference in brightness level between the preceding frame and the current frame gets smaller.  
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
      The above and/or other aspects and advantages of the prevent invention will become apparent and more readily appreciated from the following description of the exemplary embodiments, taken in conjunction with the accompany drawings, in which:  
       FIG. 1  is an exploded perspective view of a display apparatus according to an embodiment of the present invention;  
       FIG. 2  is a control block diagram of the display apparatus according to the embodiment of the present invention; and  
       FIG. 3  is a flow chart illustrating an operation of the display apparatus according to the embodiment of the present invention. 
    
    
     DETAILED DESCRIPTION OF THE ILLUSTRATIVE, NON-LIMITING EMBODIMENTS OF THE INVENTION  
      Reference will now be made in detail to the embodiments of the present invention, examples of which are illustrated in the accompanying drawings, wherein like reference numerals refer to like elements throughout.  
      The present invention provides a display apparatus  1  having a display panel such as an LCD panel employing LEDs as a light source or a PDP that can emit light by itself in which the blocks of the light  47  can be separately driven.  
       FIG. 1  is an exploded perspective view of a display apparatus  1  including an LCD panel, according to an embodiment of the present invention.  
      As illustrated in  FIG. 1 , the display apparatus  1  includes a display panel  20 , a light controlling member  30  sequentially positioned on the back surface of the display panel  20 , a light source  40  including a plurality of light source elements  45 , and a light source substrate  41  on which the light source elements  45  are mounted.  
      The display panel  20 , the light controlling member  30 , and the light source substrate  41  are accommodated between a top chasse  10  and a bottom chasse  70 .  
      The display panel  20  includes a thin film transistor (TFT) substrate  21  on which TFTs are formed, a color filter substrate  22  that faces the TFT substrate  21 , a sealant (not shown) that bonds the two substrates  21  and  22  to form a cell gap, and a liquid crystal layer (not shown) positioned between the two substrates  21  and  22  and the sealant. In this embodiment, the display panel  20  has a rectangular shape with long sides and short sides. However, the shape of the display panel  20  is not limited to the above but may have various shapes.  
      In the display panel  20 , the orientation of liquid crystals in the liquid crystal layer is controlled to form an image. However, since the display panel  20  is a non-emission device, the display panel  20  has to receive light from the light source elements  45  positioned on the back surface of the display panel  20 . A driver  25  for applying a driving signal is provided on one side of the TFT substrate  21 . The driver  25  includes a flexible printed circuit board (FPC)  26 , a driving chip  27  mounted on the FPC  26 , and a printed circuit board (PCB)  28  connected to the FPC  26 . The driver  25  is shown to employ a chip-on-film (COF) system. Alternatively, other well-known systems, such as a tape carrier package (TCP) system and a chip-on-glass (COG) system may be applied to the driver  25 . Also, the driver  25  may be formed on the TFT substrate  21  in a wiring line forming process.  
      The light controlling member  30  positioned on the back surface of the display panel  20  includes a diffusing plate  31 , a prism film  32 , and a passivation film  33 .  
      The diffusing plate  31  is formed of a coating layer containing a base plate and beads formed in the base plate. The diffusing plate  31  diffuses light supplied from the light source elements  45  to provide uniform brightness.  
      Triangular prisms are uniformly arranged on the top surface of the prism film  32 . The prism film  32  collects the light diffused by the diffusing plate  31  in a direction perpendicular to the plane at which the display panel  20  is arranged. Two sheets of prism films  32  are commonly used and micro prisms formed in the prism films  32  form a predetermined angle. Most of the light that passes through the prism films  32  perpendicularly travels to provide uniform distribution of brightness. If necessary, a reflective polarizing film may be used together with the prism films  32 , or only the reflective polarizing film may be used without the prism films  32 .  
      The light source  40  that provides light to the display panel  20  includes the plurality of light source elements  45  and the light source substrate  41  on which the light source elements  45  are mounted. The light source substrate  41  is positioned on the entire back surface of the display panel  20 . Here, for the sake of convenience of description, the light source substrate  41  is shown to be partitioned. As described later, the light source  40  of the display apparatus  1  according to the embodiment of the present invention includes the plurality of light source units  47  each including at least one light source element  45 . The plurality of light source units  47  may be provided to correspond to the plurality of blocks by which the light source substrate  41  is partitioned. That is, as illustrated in  FIG. 1 , the light source substrate  41  may be partitioned into the plurality of blocks and the light source units  47  may be provided to correspond to the blocks.  
      As illustrated in  FIG. 1 , the light source  40  includes 9 light source units  47 , each of which includes 6 light source elements  45 . Here, each of the light source units  47  can receive power from a respective light source driver  150  (see  FIG. 2 ). The light source driver  150  and a controller  130  for controlling the light source driver  150  are provided on the back surface of the light source substrate  41 .  
      It is preferable but not necessary that the light source elements  45  are mounted on the light source substrate  41  and are uniformly arranged on the entire back surface of the display panel  20 . Each of the light source elements  45  is composed of 3 sub-light source elements for emitting red, blue, and green light components, respectively. The red, blue, and green light components are mixed with each other to supply white light to the display panel  20 . A method of arranging the red, blue, and green sub-light source elements is not limited to the above but white diodes may be provided instead of the red, blue, and green sub-light source elements. Furthermore, red, blue and green light may be individually provided instead of being mixed to form the white light. That is, the different colored LED may be sequentially operated in synchronization with the corresponding colored image signals to provide colored light.  
      A reflecting plate  51  is provided on the light source substrate  41  where the light source elements  45  are not formed. Light source element accommodating holes  52  corresponding to the light source elements  45  are provided in the reflecting plate  51  so that the light source elements  45  are accommodated in the light source device accommodating holes  52 . The reflecting plate  51  reflects light incident on the lower part thereof to supply the reflected light to the diffusing plate  31 . The reflecting plate  51  may be formed of polyethyleneterephthalate (PET) or polycarbonate (PC). Also, the reflecting plate  51  may be provided to be thick so that the reflecting plate  51  is not shriveled by the strong heat generated by the light source elements  45 .  
      According to another embodiment, the light source  40  may include lamps as well as light emitting devices such as the LEDs if the lamps can be driven by block. In this case, it is preferable but not necessary that the lamps are divided into a plurality of blocks to adjust highlight of the light source  40  by block. In this case, a plurality of light source drivers  150  has to be provided to correspond to the plurality of blocks. A cold cathode fluorescent lamp (CCFL) or an external electrode fluorescent lamp (EEFL) may be used as the lamp.  
      A heat conduction sheet  80  is attached to the external surface of the bottom chasse  70 . The heat conduction sheet  80 , which is arranged in parallel with the light source substrate  41 , receives the heat generated by the light source elements  45  and discharges the received heat to the outside. The heat conductivity of the heat conduction sheet  80  in a plane direction is different from the heat conductivity of the heat conduction sheet  80  in a thickness direction. It is preferable but not necessary that the heat conductivity in the plane direction is larger by more than 100 W/mK than the heat conductivity in the thickness direction.  
       FIG. 2  is an internal control block diagram of the display apparatus  1  according to the embodiment of the present invention. Hereinafter,  FIG. 2  will be described in detail with reference to  FIG. 1 .  
      As illustrated in  FIG. 2 , the display apparatus  1  according to the embodiment of the present invention includes the display panel  20 , the light source units  47  each having at least one light source element  45 , the light source driver  150 , a data processor  110 , and a controller  130 .  
      The display panel  20  displays a predetermined image based on image data. The display panel  20  is partitioned into a plurality of blocks each having a respective light source unit  47 . To be specific, each of the plurality of light source units  47  provided on the back surface of the display panel  20  includes at least one light source element  45 .  
      In the display apparatus  1 , the display panel  20  is divided into blocks and the light source units  47  are provided to correspond to the blocks. For example, when the display panel  20  is divided into 9 blocks, the light source  40  includes 9 light source units  47  corresponding to the 9 blocks. Here, since each of the light source units  47  is driven by the light source driver  150  capable of transmitting a voltage, which will be described later, the light source units  47  provide highlighted light components different by blocks to the display panel  20 .  
      The light source driver  150  supplies power to the corresponding light source unit  47  that is electrically connected to the light source driver  150 . Specifically, the light source driver  150  supplies power to the light source elements  45 , for example, red, blue, and green LEDs, included in the corresponding light source unit  47 . The amount of power supplied to the red, blue, and green LEDs are controlled by the controller  130  to be described later.  
      The data processor  110  processes image data of an image signal applied to the display panel  20  and determines brightness levels to be output from the light source units  47 . That is, the data processor  110  provides brightness levels that are different by blocks or the same brightness level for all blocks to the controller  130  that controls the light source units  47 .  
      In this embodiment, the data processor  110  includes a brightness level operator  111  and may further include at least one of a block brightness level controller  113  and a frame brightness level controller  115 .  
      The brightness level operator  111  operates brightness levels of input image data. Here, it is preferable but not necessary that 60 frames of the image data are sequentially applied in one second.  
      The brightness level operator  111  may operate a brightness level for each frame by blocks or may operate the brightness levels of the entire frames regardless of blocks. Here, the brightness level operator  111  may calculate the brightness level for each pixel of the image signal.  
      The block brightness level controller  113  operates differences in brightness level between adjacent blocks and controls at least one of the brightness levels by blocks so that the differences in brightness level between the adjacent blocks fall within a predetermined range.  
      To be specific, in the case where the blocks include a first block and a second block adjacent to the first block, when a difference between a first brightness level corresponding to the first block and a second brightness level corresponding to the second block is out of a predetermined range, the block brightness level controller  113  changes at least one of the first brightness level and the second brightness level to a predetermined brightness level based on the difference between in the first and second brightness levels.  
      For example, the blocks may be distinguished from each other in accordance with their positions on the display panel as follows.  
                                                          B (x, y)   B (x + 1, y)   . . .           B (x, y + 1)   B (x + 1, y + 1)           . . .                      
 
      As shown in the above table, the blocks of the display panel  20  are distinguished from each other by B(x,y), B(x+1,y), B(x,y+1), and B(x+1,y+1) to correspond to the positions of the blocks. In this embodiment, the block brightness level controller  113  controls the brightness levels of the blocks according to [EQUATION 1] and [EQUATION 2] when differences in brightness level between blocks are out of a predetermined range.  
      when B(x, y)≧B(x+1,y) and (x, y)−B(x+1,y)|&gt; predetermined range, 
 
 B ( x+ 1, y )= B ( x,y )− a   [EQUATION 1]
 
      wherein, a is preferably a value obtained by experiments.  
      when B(x, y)&lt;B(x+1,y) and |B(x, y)−B(x+1,y)|&gt; predetermined range, 
 
 B ( x, y )= B ( x+ 1, y )− a   [EQUATION 2]
 
      A difference in brightness level between B(x,y) and B(x,y+1) as well as between B(x,y) and B(x+1,y) is determined to control the brightness levels of the blocks. Also, a difference in brightness level between B(x,y) and B(x+1,y+1) is determined to control the brightness levels of the blocks.  
      When the brightness level operator  111  calculates the brightness levels of the image data corresponding to the frames, the frame brightness level controller  115  operates a difference in brightness level between two consecutive frames and controls the brightness levels of the frames based on the difference in brightness level between the two consecutive frames.  
      For example, the frame brightness level controller  115  operates a difference in brightness level between preceding and current frames and controls the brightness levels of the frames based on the operated difference in brightness level between the preceding and the current frames.  
      Here, the frame brightness level controller  115  calculates the difference in brightness level between the preceding and current frames based on the brightness levels of the pixels of the image data. That is, the frame brightness level controller  115  calculates the difference in brightness level between the preceding and current frames based on a difference between a histogram of brightness level vs. pixel of the preceding frame and a histogram of brightness level vs. pixel of the current frame.  
      That is, the frame brightness level controller  115  controls the brightness level of the current frame to be controlled to be a brightness level between the brightness level of the preceding frame and the brightness level of the current frame before the adjustment. To be specific, the smaller the difference in brightness level between the preceding frame and the current frame before the adjustment, the closer the brightness level of the current frame is to the brightness level of the preceding frame.  
      In this embodiment, the brightness levels of the pixels are divided into 0 to 255 and the brightness levels of the pixels are calculated to calculate differences in brightness level between pixels included in the preceding frame and pixels included in the current frame.  
      Here, the difference in brightness level between the preceding frame Ff and the current frame Fr is obtained from [EQUATION 3]. 
 
Difference=(the number of 0s of  Ff −the number of 0s of  Fr )+(the number of 1s of  Ff −the number of 1s of  Fr )+ . . . +(the number of 255s of  Ff −the number of 255s of  Fr )  [EQUATION 3]
 
      In this manner, the frame brightness level controller  115  calculates coefficients corresponding to the calculated difference values and calculates the brightness level of the current frame controlled by EQUATION 4 based on the calculated coefficients. 
 
Controlled brightness level of current frame=(255−coefficient)′the brightness level of the preceding frame+coefficient′brightness level of current frame that is not controlled  [EQUATION 4]
 
      The frame brightness level controller  115  controls the brightness level corresponding to the current frame according to [EQUATION 4]. The larger the difference between the brightness level of the current before the adjustment and the brightness of the preceding frame is, the closer the brightness level of the current frame is to the brightness level of the current frame before the adjustment.  
      That is, the smaller the difference between the brightness level of the current frame and the brightness level of the preceding frame is, the closer the brightness level of the current frame is to the brightness level of the preceding frame.  
      Here, the frame brightness level controller  115  calculates only the difference in brightness level between the frames in a predetermined region and controls only the brightness level of the current frame in the predetermined region based on the difference in brightness level in the predetermined region.  
      That is, the frame brightness level controller  115  operates the difference in brightness level between the consecutive preceding and current frames corresponding to at least one block and controls the brightness level of the current frame corresponding to at least one block so that the difference in brightness level between the frames falls in the predetermined range.  
      It is noted that the various other ways of obtaining the difference in the brightness levels between the adjacent blocks of the same frame or between the blocks of the different frames that correspond to the same position within the frame may be utilized. Furthermore, in case the difference between the blocks is limited to a predetermined maximum value, the maximum value may be arrived at by a tuning process involving a visual observation by a technician or an end-user. Still furthermore, the maximum values may be variable in accordance with the input video signal. As an example, if the difference in the brightness levels of the blocks are between the blocks in the lower range of the brightness levels, the maximum difference level allowed by the controller  130  may be smaller as compared to the case in which the difference in the brightness levels of the blocks are between the blocks in the higher range of the brightness levels. The reason for this is that the human eyes tend to be more sensitive to the changes in the brightness levels in the lower range (which may cause to viewer to see artifacts) than the changes in the brightness levels in the higher range. Other factors that may influence the setting of the maximum brightness values between the blocks allowed by the controller  130  may include the type of lights source  47  and the specification or rating of the light source  47 .  
      The controller  130  controls the light source driver  150  based on the brightness of each block calculated and controlled by the data processor  110 . That is, the controller  130  controls the light source driver  150  in such a manner that a light source unit  47  corresponding to a block having high brightness provides light of high brightness and that a light source unit  47  corresponding to a block having low brightness provides light of low brightness. To this end, the light source driver  150  supplies different power to the light source units  47  corresponding to the brightness of the blocks. Accordingly, the brightness of each light source unit  47  provided to a screen varies with blocks. Also, the controller  130  controls the light source driver  150  so that the brightness of each light source unit  47  in the next frame also varies with image data. Then, the light source driver  150  supplies power to each of the light source units  47 .  
      Hereinafter, a control method of the above-described display apparatus will be described with reference to  FIG. 3  showing a flow chart of an operation of the display apparatus according to the embodiment of the present invention.  
      As illustrated in  FIG. 3 , in the display apparatus  1 , when image data are applied to the display panel  20  at operation S 11 , an image is displayed on the display panel  20  based on the applied image data.  
      The display panel  20  is divided into predetermined blocks so that the light source units  47  corresponding to the blocks are separately driven. Accordingly, the brightness levels of the blocks may be differently represented. Here, the division of the display panel  20  into the predetermined blocks is not seen to a user, but means that the light source elements included in the light source  40  are separately driven with predetermined units.  
      The brightness level operator  111  of the display apparatus  1  operates the brightness levels of the image data applied to the display panel  20 . At this time, the brightness level operator  111  operates the brightness levels of the image data by blocks into which the display panel  20  is divided at operation S 13 . The block brightness level controller  113  operates a difference in brightness level between adjacent blocks based on the brightness levels of the image data operated by the brightness level operator  111  at operation S 15 .  
      The block brightness level controller  113  controls at least one of the brightness levels by blocks to a predetermined brightness level so that the difference in brightness level between the adjacent blocks falls within a predetermined range at operation S 17 . That is, the difference in the brightness level is limited to a maximum brightness value (as described above). Since the method of the block brightness level controller  113  controlling the brightness levels of the image data corresponding to the blocks was described above, description of the method will be herein omitted.  
      On the other hand, the brightness level operator  111  calculates the brightness levels of the image data corresponding to the frames at operation S 19 . Then, the frame brightness level controller  115  operates a difference in brightness level between continuous preceding and current frames at operation S 21 . Since the method of the frame brightness level controller  115  operating the difference in brightness level between the preceding and current frames was described above, description of the method will be herein omitted.  
      The frame brightness level controller  115  controls the brightness level of the image data corresponding to the current frame so that the difference in brightness level of image data between continuous preceding and current frames fall within a predetermined range at operation S 23 . That is, the difference in the brightness level is limited to a maximum brightness value (as described above). At this time, it is preferable but not necessary that the frame brightness level controller  115  controls the controlled brightness level of the image data corresponding to the current frame to be between the brightness level of the image data corresponding to the current frame and the brightness level of the image data corresponding to the preceding frame. At this time, since the method of the frame brightness level controller  115  controlling the brightness level of the image data corresponding to the current frame was described above, description of the method will be herein omitted.  
      At this time, the frame brightness level controller  115  calculates the difference in brightness level between preceding and current frames in the predetermined region based on the brightness levels of the image data corresponding to the blocks and controls the brightness level corresponding to the current frame based on the calculated difference.  
      The controller  130  controls the light source driver  150  so that the light source  40  is separately driven, based on at least one of the brightness levels of the image data controlled by the block brightness level controller  113  and the frame brightness level controller  115  at operation S 25 .  
      According to the above-described embodiment, the data processor  110  calculates brightness levels and the light source units  47  are driven based on the calculated brightness levels. Here, the brightness levels include gray scale levels. The data processor  110  calculates the gray scale levels of the image data and the controller  130  drives the light source units  47  based on the gray scale levels to control the brightness of the image displayed on the display panel  20 .  
      As described above, in the display apparatus  1  of the present invention, the light source units  47  are separately driven to provide different highlighted light components to the blocks of the display panel  20 . Also, in the display apparatus  1  of the present invention, different highlighted light components are provided to the blocks. However, since the block brightness level controller  113  controls the brightness levels of the blocks, it is possible to prevent differences in the highlighted light components by blocks from increasing, hence preventing stepped brightness difference from being generated between blocks, thereby avoiding deteroration of image quality. Also, in the display apparatus  1 , the frame brightness level controller  115  controls the brightness levels by frames or by some blocks in the frames to prevent flickers from being generated in the frames or in some regions due to the difference in brightness level between preceding and current frames.  
      As apparent from the above description, the present invention provides a display apparatus capable of controlling at least one of a difference in brightness level between adjacent blocks and a difference in brightness level between frames to improve image quality, and a method of controlling the same.  
      Although a few exemplary embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that changes may be made in these embodiments without departing from the principles and spirit of the invention, the scope of which is defined in the appended claims and their equivalents.