Patent Publication Number: US-8988451-B2

Title: Display apparatus and image correction method of the same

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application claims priority from Korean Patent Application No. 10-2010-0077783, filed on Aug. 12, 2010 in the Korean Patent Office, the disclosure of which is incorporated herein by reference. 
     BACKGROUND 
     1. Field 
     Apparatuses and methods consistent with the exemplary embodiments relate to a display apparatus and an image correction method of the same, and more particularly, to a display apparatus which includes a plurality of display panels and an image correction method of the same. 
     2. Description of the Related Art 
     While existing outdoor advertising provides simple content, a large format display (LFD) system enables display of various content and dynamic moving images with aggressive adoption of a liquid crystal display (LCD) panel or plasma display panel (PDP). The LFD system attracts attention as a next-generation display item to bring about changes in advertising industries and paradigms. The LFD system employs different technology from an LCD panel or PDP used for a television. That is, a television is for individuals and viewed by individuals for a long time, and thus advanced image-quality technologies to improve moving images, to represent natural colors, and the like are applied. However, an LFD is generally installed indoors or outdoors in bright surroundings such as in public places or shops, and may need multi-display technologies using a plurality of digital information displays depending on applications. 
     SUMMARY 
     Accordingly, one or more exemplary embodiments provide a display apparatus including a plurality of display panels to improve uniformity of an image and an image correction method of the same. 
     Further, one or more exemplary embodiments also provide a display apparatus to improve a color difference and a brightness difference between a plurality of display panels and an image correction method of the same. 
     According to an aspect of an exemplary embodiment, there is provided a display apparatus including: a plurality of display panels which are arranged adjacently; a sensing unit which senses a display characteristic of an image displayed on the display panels; and an image correction unit which generates non-uniformity correction data corresponding to a plurality of areas included in each of the display panels based on the display characteristic, interpolates non-uniformity correction data corresponding to a boundary area being in contact with a different display panel using non-uniformity correction data corresponding to a neighbor area adjacent to the boundary area, and corrects the image displayed on the display panels based on the generated and interpolated non-uniformity correction data. 
     The non-uniformity correction data may include at least one of color correction data and brightness correction data, the color correction data correcting a color difference of the image displayed on the display panels and the brightness correction data correcting a brightness difference of the image displayed on the display panels. 
     The color correction data may comprise a 3×3 matrix to convert a color characteristic of an input image into a predetermined target value. 
     The sensing unit may sense a color coordinate and a color temperature of each of the display panels, and the image correction unit may set the most frequent color coordinate and the most frequent color temperature, or an average color coordinate and an average color temperature among the sensed color coordinates and the sensed color temperatures as the target value. 
     The color correction data may include a lookup table to convert a color characteristic of an input image one to one. 
     The brightness correction data may include a coefficient to convert a brightness of an input image into a predetermined target value. 
     The image correction unit may interpolate the non-uniformity correction data corresponding to the boundary area based on a relative position between the boundary area and the neighbor area. 
     According to an aspect of another exemplary embodiment, there is provided an image correction method of a display apparatus which includes a plurality of display panels arranged adjacently, the method including: sensing a display characteristic of an image displayed on the display panels; generating non-uniformity correction data corresponding to a plurality of areas included in each of the display panels based on the display characteristic; interpolating non-uniformity correction data corresponding to a boundary area being in contact with a different display panel using non-uniformity correction data corresponding to a neighbor area adjacent to the boundary area; and correcting the image displayed on the display panels based on the generated and interpolated non-uniformity correction data. 
     The generating the non-uniformity correction data may include at least one of generating color correction data and generating brightness correction data, the color correction data correcting a color difference of the image displayed on the display panels and the brightness correction data correcting a brightness difference of the image displayed on the display panels. 
     The generating the non-uniformity correction data may include generating a 3×3 matrix to convert a color characteristic of an input image into a predetermined target value. 
     The sensing the display characteristic may include sensing a color coordinate and a color temperature of each of the display panels, and the generating the non-uniformity correction data may include setting the most frequent color coordinate and the most frequent color temperature, or an average color coordinate and an average color temperature among the sensed color coordinates and the sensed color temperatures as the target value. 
     The generating the non-uniformity correction data may include generating a lookup table to convert a color characteristic of an input image one to one. 
     The generating the non-uniformity correction data may include generating a coefficient to convert a brightness of an input image into a predetermined target value. 
     The interpolating the non-uniformity correction data may interpolate the non-uniformity correction data corresponding to the boundary area based on a relative position between the boundary area and the neighbor area. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The above and/or other aspects will become apparent and more readily appreciated from the following description of the exemplary embodiments, taken in conjunction with the accompanying drawings, in which: 
         FIG. 1  illustrates a display apparatus including a plurality of display panels according to an exemplary embodiment; 
         FIG. 2  is a block diagram of the display apparatus according to the exemplary embodiment; 
         FIG. 3  illustrates image correction between areas of the display apparatus according to the exemplary embodiment; 
         FIG. 4  is a flowchart illustrating an image correction method of the display apparatus according to the exemplary embodiment; 
         FIG. 5  is a flowchart illustrating an image correction method of a display apparatus according to another exemplary embodiment; and 
         FIG. 6  is a flowchart illustrating an image correction method of a display apparatus according to still another exemplary embodiment. 
     
    
    
     DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS 
     Below, exemplary embodiments will be described in detail with reference to accompanying drawings so as to be easily realized by a person having ordinary knowledge in the art. The exemplary embodiments may be embodied in various forms without being limited to the exemplary embodiments set forth herein. Descriptions of well-known parts are omitted for clarity, and like reference numerals refer to like elements throughout. 
       FIG. 1  illustrates a display apparatus including a plurality of display panels according to an exemplary embodiment. As shown in  FIG. 1 , the display apparatus  100  includes a plurality of display panels  1  to  9 . Display panels may be arranged in an M×N matrix form in a grid shape, and  FIG. 1  shows the nine display panels  1  to  9  arranged in a 3×3 configuration. The display apparatus  100  may be realized as a large format display (LFD) system installed indoors or outdoors in bright surroundings such as in public places or shops for outdoor advertising. The same image or different images are displayed on the display panels  1  to  9  irrespective of the display panel  1  to  9 , but a single image is displayed over the display panels  1  to  9  as shown in  FIG. 1 . Generally, an advertisement to be viewed by a plurality of people may be displayed as a still image or replayed as a moving image. The LFD system which attracts attention as a next-generation display item includes a plurality of display panels  1  to  9  arranged to be connected with each other, and thus there is a need for uniformity of image display characteristics, for example, brightness or color characteristics. 
       FIG. 2  is a block diagram of a display apparatus according to an exemplary embodiment. As shown in  FIG. 2 , the display apparatus includes a display unit  10  including a plurality of display panels  1  to  9  arranged adjacently, a sensing unit  20 , and an image correction unit  30 . 
     The display unit  10  may include a liquid crystal display (LCD) panel including liquid crystals, an organic light emitting diode (OLED) panel including organic light emitting diodes, or a plasma display panel (PDP), and may include a panel driver driving the panels. The display panels  1  to  9  may include one kind of panel or different kinds of panels. The display panels  1  to  9  may be realized by one kind of display panel in order to easily control an image displayed on the display unit  10  and may be formed of an LCD panel in view of cost, power consumption, and a volume of the display panels  1  to  9 . The display panels  1  to  9  may display a single-color image such as a white image or block image in order to correct an image. 
     The sensing unit  20  may include a photo sensor to sense an image displayed on the display panels  1  to  9  and a module to identify display characteristics of the display panels  1  to  9  on which an image is displayed from information sensed by the photo sensor. The sensing unit  20  may identify the display characteristics while traveling over the display panels  1  to  9  or may be disposed in respective bezels between the display panels  1  to  9 . The sensing unit  20  senses a center part of the display panels  1  to  9  to identify a brightness, a color temperature, a color coordinate, and a gamma value of an image displayed on the display panels  1  to  9 . Also, the sensing unit  20  senses display characteristics in a plurality of parts of the display panels  1  to  9  and provides an average value or representative value of the display characteristics of the display panels  1  to  9  to the image correction unit  30 . As the number of display characteristics sensed by the sensing unit  20  from each of the display panels  1  to  9  or all the display panels  1  to  9  increases, more precise and reliable data is collected to easily control uniformity of the display panels  1  to  9 . 
     The image correction unit  30  generates non-uniformity correction data corresponding to a plurality of areas in each of the display panels  1  to  9  based on the display characteristics output from the sensing unit  20  and interpolates non-uniformity correction data corresponding to a boundary area B being in contact with different display panels  1  to  9  using non-uniformity correction data corresponding to a neighbor area A adjacent the boundary area B. Further, the image correction unit  30  corrects a display characteristic of an image displayed on the display panels  1  to  9  based on the generated and interpolated non-uniformity correction data. 
     As shown in  FIG. 2 , the image correction unit  30  includes a non-uniformity correction data generation unit  31  and an image signal conversion unit  32 . The non-uniformity correction data generation unit  31  generates at least one of color correction data and brightness correction data as non-uniformity correction data. The color correction data is used to correct a color difference of an image displayed on the display panels  1  to  9 , and the brightness correction data is used to correct a brightness difference of an image displayed on the display panels  1  to  9 . The image signal conversion unit  32  maps or converts an input image signal into a new image signal using the non-uniformity correction data generated by the non-uniformity correction data generation unit  31 . 
       FIG. 3  illustrates image correction between areas of the display apparatus according to the exemplary embodiment. For convenience, description is made with four display panels  1 ,  2 ,  3 , and  4  arranged up, down, right, and left as an illustrative example. As shown in  FIG. 3 , each of the display panels  1 ,  2 ,  3 , and  4  is divided into a matrix of 3×3 areas I. However, the number of divided areas I is not limited, and each display panel may be divided in 2×2 or more precisely than 3×3. Boundary areas B of one display panel  1 ,  2 ,  3 , and  4  among the plurality of areas I are adjacent to boundary areas B of another display panel  1 ,  2 ,  3 , and  4 . For example, areas {circle around ( 1 )} to {circle around ( 4 )} and areas {circle around ( 6 )} to {circle around ( 9 )} of each display panel  1  through  4  correspond to the boundary areas B because each of these areas is adjacent to a corresponding area in a different display panel. For instance, areas {circle around ( 3 )} through {circle around ( 9 )} of the first display panel  1  are adjacent to the second display panel  2 , and areas {circle around ( 7 )} to {circle around ( 9 )} of the first display panel  1  are adjacent to the third display panel  3 . Meanwhile, in the present embodiment, an area adjacent to the boundary areas B is defined as a neighbor area A. For example, a neighbor area A 1  of an area {circle around ( 3 )} B 1  of the second display panel  2  is areas {circle around ( 2 )}, {circle around ( 5 )}, and {circle around ( 6 )} of the second display panel  2 . A neighbor area A 2  of area {circle around ( 3 )} B 2  of a third display panel  3  is areas {circle around ( 8 )} and {circle around ( 9 )} of the first display panel  1 , area {circle around ( 7 )} of the second display panel  2 , areas {circle around ( 2 )}, {circle around ( 5 )}, and {circle around ( 6 )} of the third display panel  3 , and areas {circle around ( 1 )} and {circle around ( 4 )} of a fourth display panel  4 , which encompass the area {circle around ( 3 )} B 2 . 
     The non-uniformity correction data generation unit  31  according to the present embodiment generates non-uniformity correction data corresponding to each of the plurality of areas I and interpolates non-uniformity correction data of the boundary areas B using the non-uniformity correction data.  FIG. 4  is a flowchart illustrating an image correction method of the display apparatus according to the exemplary embodiment, describing a method of generating color correction data among non-uniformity correction data. 
     First, the sensing unit  20  senses a display characteristic of an image displayed on each of the display panels  1 ,  2 ,  3 , and  4  (S 10 ). 
     The non-uniformity correction data generation unit  31  sets the most frequent color coordinate and the most frequent color temperature, or an average color coordinate and an average color temperature among color coordinates and color temperatures of the respective display panels  1 ,  2 ,  3 , and  4  output from the sensing unit  20  as a target value (xt, yt, Tt) (S 20 ). The target value may be set as tristimulus values (X, Y, Z) based on a color coordinate and a color temperature. That is, the most major color coordinate and the most major color temperature among the color coordinates and the color temperatures of the plurality of display panels  1 ,  2 ,  3 , and  4  are set as a standard, and a non-uniformity correction data of each of the areas I is generated based on the standard. 
     Then, the non-uniformity correction data generation unit  31  generates a 3×3 matrix which corresponds to each of the areas I and converts color characteristics of the image into the target value (xt, yt, Tt) based on the display characteristics (S 30 ). An algorithm to obtain a conversion parameter such as the 3×3 matrix may vary and is not limited to a specific one in the present embodiment. A 3×3 matrix to make a representative value (xi, yi, Ti) of a color coordinate and a color temperature sensed in each area the target value (xt, yt, Tt) is as follows. 
     
       
         
           
             
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     The non-uniformity correction data generation unit  31  interpolates a 3×3 matrix as non-uniformity correction data corresponding to a boundary area of each area I, using a 3×3 matrix corresponding to a neighbor area A adjacent to the boundary area B (S 40 ). The area {circle around ( 3 )} B 1  of the second display panel  2  shown in  FIG. 3  is interpolated or newly generated using a 3×3 matrix of the neighbor area A 1 . 
     In particular, when a neighbor area A 2  of area {circle around ( 3 )} B 2  of the third display panel  3  includes areas I of the plurality of display panels  1 ,  2 ,  3 , and  4 , generation of a 3×3 matrix by interpolation of the neighbor area A 2  is more effective to solve non-uniformity. When the plurality of display panels  1 ,  2 ,  3 , and  4  are disposed adjacently, there is a high possibility of occurrence of non-uniformity on a boundary between the display panels  1 ,  2 ,  3 , and  4  depending on properties of the respective display panels  1 ,  2 ,  3 , and  4 . Thus the non-uniformity correction data generation unit  31  generates non-uniformity correction data for the boundary areas B using non-uniformity correction data of different display panels  1 ,  2 ,  3 , and  4  from each other. 
     The non-uniformity correction data generation unit  31  stores the generated and interpolated 3×3 matrix and provides the matrix to the image signal conversion unit  32 . 
     The above processes may be repeated a plurality of times to generate a more precise 3×3 matrix. For example, when the image signal conversion unit  32  corrects an image based on a generated 3×3 matrix, the sensing unit  20  detects a display characteristic of the image again. Then, when a difference between the sensed display characteristic and a target value does not satisfy a predetermined range, a process of obtaining a 3×3 matrix is repeated. 
     According to another exemplary embodiment, a matrix is not limited to a 3×3 form but may have an m×n (m and n are an integer) shape formed based on sensed display characteristics. 
     Finally, the image signal conversion unit  32  corrects an input image based on the generated and interpolated 3×3 matrix and displays the image on the display panels  1 ,  2 ,  3 , and  4  (S 50 ). 
       FIG. 5  is a flowchart illustrating an image correction method of a display device according to another exemplary embodiment. 
     A non-uniformity correction data generation unit  31  according to the present embodiment generates a lookup table to convert a color characteristic of an input image on a one to one basis (S 31 ). The non-uniformity correction data generation unit  31  sets a correction level of R, G, and B in each area based on a display characteristic output from a sensing unit  20 . Further, the non-uniformity correction data generation unit  31  generates a lookup table of a gray scale value to adjust a gamma value and a color coordinate corresponding to each area to be a predetermined target gamma value and a predetermined target color coordinate. The non-uniformity correction data generation unit  31  may be realized by a program to generate a lookup table of a color characteristic, that is, a gray scale. When generating the lookup table, unique characteristics of each of the display panels  1 ,  2 ,  3 , and  4  may be reflected. In addition, when generating the lookup table, instead of generating a lookup table of all gray scale, a lookup table of part of a gray scale is generated, and a lookup table of the remaining of the gray scale may be generated by interpolation. 
     Then, the non-uniformity correction data generation unit  31  interpolates a lookup table corresponding to a boundary area B among a lookup table of each area I using a lookup table corresponding to a neighbor area A adjacent to the boundary area B (S 41 ). 
     The image signal conversion unit  32  corrects an input image based on the generated and interpolated lookup table and displays the image on the display panels  1 ,  2 ,  3 , and  4  (S 51 ). 
       FIG. 6  is a flowchart illustrating an image correction method of a display apparatus according to still another exemplary embodiment. The present embodiment describes a method of generating brightness correction data to correct a brightness difference of an image. 
     The sensing unit  20  senses a display characteristic of an image displayed on the display panels (S 10 ). The non-uniformity correction data generation unit  31  according to the present embodiment generates a coefficient to convert a brightness of an input image into a predetermined target value (S 33 ). The non-uniformity correction data generation unit  31  sets a coefficient in each area based on display characteristics, that is, a brightness of an image, output from a sensing unit  20 . A target brightness value may be the most frequent brightness value or the lowest brightness value. For example, there is a case where when an image having a brightness of 100 is input, an area {circle around ( 1 )} of a first display panel  1  is sensed to have a brightness of 90, and an area {circle around ( 1 )} of a second display panel  2  is sensed to have a brightness of 95. In this case, the brightness of the area {circle around ( 1 )} of the first display panel  1  of 90, which represents a lower brightness, may become the target brightness value, and a coefficient of the area {circle around ( 1 )} of the second display panel  2  may be set to be 90/95. 
     Then, the non-uniformity correction data generation unit  31  interpolates a gray scale corresponding to a boundary area B among a gray scale of each area I using a gray scale corresponding to a neighbor area A adjacent to the boundary area B (S 43 ). 
     The image signal conversion unit  32  corrects an image in the same process as the above (S 53 ). 
     The display apparatus may perform color correction after brightness correction or perform brightness correction after color correction. Also, only either one of color correction and brightness correction may be performed as long as uniformity is improved. 
     Alternatively, a brightness of a backlight unit may be adjusted based on non-uniformity correction data instead of an image signal. When the display panels  1  to  9  include an LCD panel, an image&#39;s display characteristics may be changed by light emitted from the backlight unit. Thus, the light emitted from the backlight unit is controlled to control the display characteristics of the image uniformly. In particular, when the backlight unit includes three colors of light emitting diodes, light may be controlled by the colors, thereby efficiently controlling the display characteristics. 
     Although a few exemplary embodiments have been shown and described, it will be appreciated by those skilled in the art that changes may be made in these exemplary embodiments without departing from the principles and spirit of the invention, the scope of which is defined in the appended claims and their equivalents.