Abstract:
A liquid crystal display is provided having improved image quality and visibility. The display device includes: a plurality of display panels which display multiple images from multiple display panels; a projection film which overlaps the display panels; and a lens panel including a first lens unit and a second lens unit is interposed between the display panel and the projection film. The first lens unit refracts images and the second lens unit improves image brightness. Therefore the resultant projection is a seamlessly connected image from the multiple display panels.

Description:
REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application claims priority from Korean Patent Application No. 10-2008-0092252 filed on Sep. 19, 2008 in the Korean Intellectual Property Office, the disclosure of which is incorporated herein by reference in its entirety. 
       BACKGROUND OF THE INVENTION 
       [0002]    1. Field of the Invention 
         [0003]    The present invention relates to a display device, and more particularly, to a display device including a plurality of display panels which form a large display surface with superior display quality. 
         [0004]    2. Description of the Related Art 
         [0005]    As modern society becomes more dependent on sophisticated information and communication technology, market needs for larger and thinner displays are growing. In particular, since conventional cathode ray tubes (CRTs) have failed to fully satisfy these market needs, the demand for flat panel displays (FPDs), such as plasma display panels (PDPs), plasma address liquid crystal display panels (PALCs), liquid crystal displays (LCDs), and organic light emitting diodes (OLEDs), is exploding. Since display devices have clear image quality and can be made lighter and thinner, they are widely used in various electronic devices. 
         [0006]    LCDs are one of the most widely used FPDs. An LCD includes two display panels, on which electrodes are formed, and a liquid crystal layer which is interposed between the two display panels. The electric field formed by applying voltages to the electrodes rearranges the liquid crystal molecules and thus controls the amount of light passing through the liquid crystal layer. In this way, the LCD displays a desired image. 
         [0007]    With the soaring demand for a large display surface, large display panels are being actively developed. However, the cost of developing large display panels is high; there is growing interest in technology for forming a large display surface by using a plurality of smaller display panels. 
         [0008]    A conventional display panel has a display region where images are displayed and a non-display peripheral region where no images are displayed. Therefore, when a plurality of conventional display panels are arranged adjacent to each other to form a large display screen, their non-display regions are displayed as visible grids on the display screen. The screens of the display devices cannot be seamlessly merged for the viewer. 
       SUMMARY OF THE INVENTION 
       [0009]    Aspects of the present invention provide a large display device formed from a plurality of smaller display panels, which demonstrate superior display quality. 
         [0010]    However, aspects of the present invention are not restricted to the one set forth herein. The above and other aspects of the present invention will become more apparent to one of ordinary skill in the art to which the present invention pertains by referencing the detailed description of the present invention given below. 
         [0011]    According to one aspect of the present invention, a display device is provided including: a display panel which displays an image; a projection film which overlaps the display panel; and a lens panel which includes a first lens unit and is interposed between the display panel and the projection film, wherein the first lens unit receives and refracts the image from the display panel and projects the image onto the projection film. 
         [0012]    adjusts an output direction of the image by refracting the image input thereto and projects the image onto the projection film. 
         [0000]    According to another aspect of the present invention, a display device is provided including: a plurality of display panels which are arranged adjacent to each other, and each panel includes a display region where an image is displayed and a non-display region where the image is not displayed; a projection film which overlaps the display panels; and a lens panel, interposed between the display panels and the projection film, includes a first lens unit and a second lens unit. The first lens unit adjusts an image output direction images seamlessly on the projection film wherein the display panels have a portion formed by the non-display regions which are disposed adjacent to each other, and the first lens unit projects the image onto a region of the projection film which overlaps the non-display regions. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0013]    The above and other aspects and features of the present invention will become more apparent by describing in detail the exemplary embodiments thereof with reference to the attached drawings, in which: 
           [0014]      FIG. 1  is an exploded perspective view of a display device according to a first exemplary embodiment of the present invention; 
           [0015]      FIG. 2  is a schematic cross-sectional view of the display device shown in  FIG. 1 ; 
           [0016]      FIG. 3  is an enlarged cross-sectional view of a region A shown in  FIG. 2 ; 
           [0017]      FIG. 4  is a perspective view of a first lens unit included in the display device of  FIG. 1 ; 
           [0018]      FIG. 5A  is a perspective view of the first lens unit included in the display device of  FIG. 1  after a voltage is applied to the first lens unit; 
           [0019]      FIG. 5B  is a cross-sectional view of the first lens unit shown in  FIG. 5A ; 
           [0020]      FIG. 6  is a perspective view of a second lens unit included in the display device of  FIG. 1 ; 
           [0021]      FIG. 7A  is a perspective view of the second lens unit included in the display device of  FIG. 1  after a voltage is applied to the second lens unit; 
           [0022]      FIG. 7B  is a cross-sectional view of the second lens unit shown in  FIG. 7A ; 
           [0023]      FIG. 8A  is a cross-sectional view of a first lens unit included in a display device according to a second exemplary embodiment of the present invention; 
           [0024]      FIG. 8B  is a cross-sectional view of the first lens unit of  FIG. 8A  after an electric field is applied thereto; 
           [0025]      FIG. 9  is a perspective view of lens panels and display panels included in a display device according to a third exemplary embodiment of the present invention; 
           [0026]      FIG. 10  is a perspective view of a first lens unit included in the display device of  FIG. 9 ; 
           [0027]      FIG. 11  is a perspective view of a second lens unit included in the display device of  FIG. 9 ; 
           [0028]      FIG. 12  is a perspective view of display panels and lens panels included in a display device according to a fourth exemplary embodiment of the present invention; 
           [0029]      FIG. 13  is a schematic cross-sectional view of the display device shown in  FIG. 12 ; 
           [0030]      FIG. 14  is a perspective view of a multi-display apparatus having a plurality of display devices arranged adjacent to each other according to an exemplary embodiment of the present invention; and 
           [0031]      FIG. 15  is a schematic cross-sectional view of the multi-display apparatus shown in  FIG. 14 . 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0032]    Advantages and features of the present invention and methods of accomplishing the same may be understood more readily by reference to the following detailed description of exemplary embodiments and the accompanying drawings. The present invention may, however, be embodied in many different forms and should not be construed as being limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete and will fully convey the concepts of the invention to those skilled in the art, and the present invention will only be defined by the appended claims. Like reference numerals refer to like elements throughout the specification. 
         [0033]    Spatially relative terms, such as “below”, “beneath”, “lower”, “above”, “upper”, and the like, may be used herein for ease of description to describe one element or feature&#39;s relationship to another element(s) or feature(s) as illustrated in the figures. It will be understood that the spatially relative terms are intended to encompass different orientations of the device in use or operation in addition to the orientation depicted in the figures. 
         [0034]    Hereinafter, a display device  1  according to a first exemplary embodiment of the present invention will be described in detail with reference to  FIG. 1 .  FIG. 1  is an exploded perspective view of the display device  1  according to the first exemplary embodiment of the present invention. 
         [0035]    Referring to  FIG. 1 , the display device  1  according to the first exemplary embodiment includes first through third display panels  10   a  to  10   c,  first through third lens panels  100   a  to  100   c,  a projection film  20 , an upper housing  30 , an intermediate frame  50 , optical sheets  60 , a diffusion plate  70 , lamps  80 , a reflective sheet  85 , and a lower housing  90 . 
         [0036]    Each of the first through third display panels  10   a  to  10   c  includes a lower display panel and an upper display panel which faces the lower display panel. The lower display panel includes gate lines, data lines, a thin-film transistor (TFT) array, pixel electrodes, and the like. The upper display panel includes a black matrix, a common electrode, and the like. Each of the first through third display panels  10   a  to  10   c  displays image information. 
         [0037]    Each of the first through third display panels  10   a  to  10   c  may be connected to a printed circuit board (PCB) (not shown) which provides gate driving signals and data driving signals. 
         [0038]    Each of the first through third display panels  10   a  to  10   c  is a unit panel that displays an image. The first through third display panels  10   a  to  10   c  are disposed adjacent to each other to form a large screen. The first through third display panels  10   a  to  10   c  may be arranged in various ways. In addition, the display device  1  according to the first exemplary embodiment may include various numbers of display panels. That is, the first through third display panels  10   a  to  10   c  may be arranged in a horizontal direction to form a horizontally long screen. Alternatively, the first through third display panels  10   a  to  10   c  may be arranged in a vertical direction to form a vertically long screen. Since each of the first through third display panels  10   a  to  10   c  is a unit panel that displays an image, it may be considered as a single unit block. 
         [0039]    The projection film  20  is disposed above the first through third display panels  10   a  to  10   c.  The projection film  20  overlaps each of the display panels  10   a  to  10   c  and provides a screen that a user actually sees. That is, an image provided by each of the first through third display panels  10   a  to  10   c  is projected onto the projection film  20  seen by an user. 
         [0040]    The projection film  20  is made of an opaque material to prevent the first through third display panels  10   a  to  10   c  from being seen. Thus, nothing other than an image is visible on the projection film  20 . An opaque material, such as a diffusion sheet or a diffusion plate, may be used as the projection film  20 . 
         [0041]    The first through third lens panels  100   a  to  100   c  are attached between the display panels  10   a  to  10   c  and the projection film  20 , respectively. The lens panels  100   a  to  100   c  enable images from the display panels  10   a  to  10   c  to project onto the projection film  20 . Specifically, the first through third lens panels  100   a  to  100   c  control the directions in which the images on the display panels  10   a  to  10   c  will show on the projection film  20 , respectively, as seamless images on the entire surface of the projection film  20 . Thus, the first through third lens panels  100   a  to  100   c  refract images output from surfaces of the first through third display panels  10   a  to  10   c,  respectively, so that the resultant images can be seamlessly displayed on the entire surface of the projection film  20 . 
         [0042]    The first through third lens panels  100   a  to  100   c  may magnify image output from the first through third display panels  10   a  to  10   c,  respectively, and project the magnified images onto the projection film  20 . In addition, the first through third lens panels  100   a  to  100   c  may magnify or refract at least part of images from edge portions of a combined surface of the first through third display panels  10   a  to  10   c  and project the edge images to the edge portions of the projection film  20 . 
         [0043]    The first through third display panels  10   a  to  10   c,  the first through third lens panels  100   a  to  100   c,  and the projection film  20  will be described in more detail later. 
         [0044]    The upper housing  30  forms the exterior of the display device  1  and has space to accommodate the first through third display panels  10   a  to  10   c.  In addition, an open window is formed in the center of the upper housing  30  to expose the first through third display panels  10   a  to  10   c.    
         [0045]    The projection film  20  is disposed above the first through third display panels  10   a  to  10   c.  The projection film  20  may be housed in the upper housing  30 , together with the first through third display panels  10   a  to  10   c.  Alternatively, the projection film  20  may be disposed on the upper housing  30  as shown in  FIG. 1 . 
         [0046]    The upper housing  30  is coupled to the lower housing  90  with the intermediate frame  50  interposed therebetween. 
         [0047]    The intermediate frame  50  accommodates the optical sheets  50 , the diffusion plate  70 , and the lamps  80  therein. In addition, the intermediate frame  50  is firmly fixed to the lower housing  90 . The intermediate frame  50  includes sidewalls which are formed along rectangular edges thereof. An open window is formed in the center of the intermediate frame  50  to pass light that comes from the diffusion plate  70  and the optical sheets  60 . 
         [0048]    The optical sheets  60  diffuse and concentrate light received from the diffusion plate  70 . The optical sheets  60  are disposed on the diffusion plate  70  and housed in the intermediate frame  50 . The optical sheets  60  include a first prism sheet, a second prism sheet, and a protective sheet. 
         [0049]    The first and second prism sheets refract light after the diffusion plate  70  and concentrate the light to the front of the display device  1  at a low incidence angle, thereby enhancing the brightness of the display device  1  within an effective viewing angle range. 
         [0050]    The protective sheet is formed on the first and second prism sheets. The protective sheet not only protects surfaces of the first and second prism sheets but also diffuses light more uniformly. The configuration of the optical sheets  60  is not limited to the above example and may vary according to specifications of the display device  1 . 
         [0051]    The diffusion plate  70  diffuses light emitted from the lamps  80  in all directions. The diffusion plate  70  prevents bright spots of the lamps  80  from being seen at the front of the display device  1 . 
         [0052]    The optical sheets  60  may be separated from the diffusion plate  70 . Alternatively, the optical sheets  60  and the diffusion plate  70  may be integrated into a single optical member. 
         [0053]    The lamps  80  may be line lamps such as cold cathode fluorescent lamps (CCFLs) and hot cathode fluorescent lamps (HCFLs). When the lamps  70  are HCFLs, each of the HCFLs includes two terminals at each end. 
         [0054]    The reflective sheet  85  is disposed under the lamps  80  and reflects light, which is emitted downward from the lamps  80 , back upward, thereby enhancing light efficiency. 
         [0055]    The display device  1  according to the first exemplary embodiment uses a direct-type backlight assembly in which the lamps  80  are arranged directly under the display panels  10   a  to  10   c.  However, the present invention is not limited thereto. That is, the display device  1  may also use an edge-type backlight assembly in which lamps are disposed under one or more sidewalls of a display panel and in which light emitted from the lamps is delivered to the display panel via a light guide plate. 
         [0056]    Hereinafter, an image projection process of the display device  1  according to the first exemplary embodiment will be described in detail with reference to  FIGS. 2 and 3 .  FIG. 2  is a schematic cross-sectional view of the display device  1  shown in  FIG. 1 .  FIG. 3  is an enlarged cross-sectional view of a region A shown in  FIG. 2 . 
         [0057]    The first through third display panels  10   a  to  10   c  are disposed under the projection film  20 . The projection film  20  may have a large area overlapping all the display panels  10   a  to  10   c.  In this specification, a case where three display panels, i.e.,  10   a  to  10   c,  are arranged in a straight line will be described as an example. However, the present invention is not limited to the example. That is, a plurality of display panels may be arranged in various forms, and the same principle may apply irrespective of the arrangement of the display panels. 
         [0058]    The first through third display panels  10   a  to  10   c  are disposed under the projection film  20 . In addition, the first through third lens panels  100   a  to  100   c  are disposed on the first through third display panels  10   a  to  10   c,  respectively. 
         [0059]    The first through third display panels  10   a  to  10   c  may be identical or may be different from each other in size, shape, or the like. The display device  1  according to the first exemplary embodiment uses identical display panels  10   a  to  10   c.  Therefore, a description of the first display panel  10   a  may also apply to the second and third display panels  10   b  and  10   c.    
         [0060]    The first display panel  10   a  includes a display region  11   a  where images are displayed and a non-display region  12   a  where no images are displayed. Since the display region  11   a  includes a plurality of pixels arranged in a matrix, it can display images. The non-display region  12   a  surrounds the display region  11   a.    
         [0061]    When the first through third display panels  10   a  through  10   c  are successively arranged adjacent to each other, the display region  11   a  and the non-display region  12   a  of the first display panel  10   a,  a display region  11   b  and a non-display region  12   b  of the second display panel  10   b,  and a display region (not shown) and a non-display region (not shown) of the third display panel  10   c  overlap the projection film  20 . That is, the non-display regions  12   a  and  12   b  of the first and second display panels  10   a  and  10   b  and the non-display region (not shown) of the third display panel  10   c  may exist in the form of lines in a large screen formed by the first through third display panels  10   a  to  10   c  which are connected to each other. 
         [0062]    In order to prevent the non-display regions  12   a  and  12   b  of the first and second display panels  10   a  and  10   b  and the non-display region (not shown) of the third display panel  10   c  from being seen, the first through third lens panels  100   a  to  100   c  are formed on the display regions  11   a  and  11   b  of the first and second display panels  10   a  and  10   b  and the display region (not shown) of the third display panel  10   c,  respectively. The first through third lens panels  100   a  to  100   c  refract images away from the display regions  11   a  and  11   b  of the first and second display panel  10   a  and  10   b  and the display region of the third display panel  10   c  to areas of the projection film  20  which overlap the non-display regions  12   a  and  12   b  of the first and second display panels  10   a  and  10   b  and the display region of the third display panel  10   c,  respectively. Since the images are projected onto the areas of the projection film  20  which overlap the non-display regions  12   a  and  12   b  of the first and second display panels  10   a  and  10   b  and the non-display region of the third display panel  10   c  as described above, the non-display regions  12   a  and  12   b  of the first and second display panels  10   a  and  10   b  and the non-display region of the third display panel  10   c  are not shown on the projection film  20 . 
         [0063]    The first lens panel  100   a  includes a first lens unit  110   a  which adjusts an output direction of an image by refracting the image input thereto and a second lens unit  120   a  which focuses the image. The first lens unit  110   a  contains two materials having different refractive indices, and an interface is formed between the two materials. Light changes its path as it passes through the interface between the two materials. That is, the first lens unit  110   a  refracts an image away from the display region  11   a  so that the image can be displayed on a region of the projection film  20  overlapping the non-display region  12   a.    
         [0064]    The first lens unit  110   a  may be formed along the non-display region  12   a  and divided into a plurality of sections. Therefore, the first lens unit  110   a  which is divided into a plurality of sections may be formed on pixels of the display region  11   a  which is adjacent to the non-display region  12   a.  Here, each section of the first lens unit  110   a  may correspond to a pixel or a plurality of pixels. A tilt angle of a refracting interface of the two materials of the first lens unit  110   a  may be gradually reduced as the lens&#39; distance from the non-display region  12   a  increases. 
         [0065]    The second lens unit  120   a  is formed between the first display panel  10   a  and the first lens unit  110   a  and focuses an image that is received from the first display panel  10   a . That is, an image output from the first display panel  10   a  spreads as the distance from the first display panel  10   a  increases, thereby overlapping images of adjacent pixels. To prevent this problem, the second lens unit  120   a  focuses the image and provides the focuses image to the first lens unit  110   a.    
         [0066]    For a light focus function, the second lens unit  120   a  may use a convex lens having a concave refracting surface. A focal distance of the convex lens may be gradually reduced as the distance from the non-display region  12   a  increases. 
         [0067]    Each of the first lens unit  110   a  and the second lens unit  120   a  may be made of a solid or a liquid material having a refracting interface that varies with a voltage applied thereto. The liquid material may be contained in transparent container which has the same refractive index as the liquid. 
         [0068]    The first lens unit  110   a  will now be described in more detail with reference to  FIGS. 4 through 5B .  FIG. 4  is a perspective view of the first lens unit  110   a  included in the display device  1  of  FIG. 1 .  FIG. 5A  is a perspective view of the first lens unit  110   a  included in the display device  1  of  FIG. 1  after a voltage is applied to the first lens unit  110   a.    FIG. 5B  is a cross-sectional view of the first lens unit  110   a  shown in  FIG. 5A . 
         [0069]    The first lens unit  110   a  includes a liquid lens having a first liquid  111  and a second liquid  112 . The angle of a refracting surface of the first lens unit  110   a  varies with a voltage applied to the first lens unit  110   a.    
         [0070]    The first liquid  111  and the second liquid  112  may have different refractive indices so that the interface can function as a lens. One of the liquids may be hydrophilic, and the other one may be hydrophobic, so they will not mix with each other. For example, the first liquid  111  may be water with a refractive index of 1.33, and the second liquid  112  may be oil with a refractive index of 1.6. 
         [0071]    In addition, one of the liquids may be conductive. When a voltage is applied to the conductive liquid, the interface S 1  may change due to the effect of an electric field. However, the present invention is not limited thereto, and other materials that satisfy the above conditions may also be used. 
         [0072]    First and second electrodes  115  and  116  are respectively located on opposite sides of the first liquid  111  and the second liquid  112  facing each other. Each of the first and second electrodes  115  and  116  is at least partially overlaps the first liquid  111  and the second liquid  112 . 
         [0073]    Referring to  FIG. 4 , when no voltage is applied to the first and second electrodes  115  and  116 , the first liquid  111  and the second liquid  112  are separated from each other as a lower layer and an upper layer, respectively. Thus, the interface S 1  is flat between the first liquid  111  and the second liquid  112 . In this case, light travels straight through the first liquid  111  and the second liquid  112  without changing its direction. 
         [0074]    Referring to  FIG. 5A , when voltages are applied to the first and second electrodes  115  and  116 , the interface S 1 ′ (S 1 ′ indicating S 1  is under voltage in  FIGS. 5A and 5B ) tilts to a side. That is, when different voltages are applied to the first and second electrodes  115  and  116 , there occurs a potential difference between the first and second electrodes  115  and  116 . Then, electric fields are generated within the first liquid  111  and the second liquid  112 . In this case, the boundary surface S 1 ′ between the first liquid  111  and the second liquid  112  may tilt such that an end of the boundary surface S 1 ′ adjacent to one of the first and second electrodes  115  and  116 , to which a higher voltage has been applied, is placed higher than the other end of the boundary surface S 1 ′ adjacent to the other one of the first and second electrodes  115  and  116  to which a lower voltage has been applied. That is, an end of the boundary surface S 1 ′ adjacent to one of the first and second electrodes  115  and  116 , to which a higher voltage has been applied, is raised while the other end of the boundary surface S 1 ′ adjacent to the other one of the first and second electrodes  115  and  116 , to which a lower voltage has been applied, is lowered. However, since the entire boundary surface S 1 ′ remains flat, it becomes a flat surface that tilts at an angle to a side. In summary, when a voltage is applied to the electrodes  115  and  116 , different electric fields exist in the two liquids of different refractive indices, applying different forces on the two electrodes at the top portion which overlapping the first liquid and the bottom portion overlapping the second liquid. This induces the first liquid rising at the higher voltage electrode side which then results in the tilting of the liquid interface. When the voltage varies, the interface tilt angle also varies. 
         [0075]    Referring to  FIG. 5B , a higher voltage may be applied to the first electrode  115  than to the second electrode  116 . Then, the boundary surface S 1 ′ between the first liquid  111  and the second liquid  112  tilts such that an end of the boundary surface S 1 ′ adjacent to the first electrode  115  is placed higher than the other one of the boundary surface S 1 ′ adjacent to the second electrode  116 . In this case, light incident on the bottom of the first liquid  111  is refracted by the boundary surface S 1 ′ between the first liquid  111  and the second liquid  112 . When the boundary surface S 1 ′ between the first liquid  111  and the second liquid  112  tilts at an angle of θ to the second electrode  116 , the light incident on the bottom of the first liquid  111  is refracted toward the second electrode  116  and output accordingly. Therefore, light travel angle from the first lens unit  110   a  can be controlled by adjusting the voltages applied to the first and second electrodes  115  and  116 . 
         [0076]    The second lens unit  120   a  will now be described in more detail with reference to  FIGS. 6 through 7B .  FIG. 6  is a perspective view of the second lens unit  120   a  included in the display device  1  of  FIG. 1 .  FIG. 7A  is a perspective view of the second lens unit  120   a  included in the display device  1  of  FIG. 1  after a voltage is applied to the second lens unit  120   a.    FIG. 7B  is a cross-sectional view of the second lens unit  120   a  shown in  FIG. 7A . 
         [0077]    The second lens unit  120   a  includes a liquid lens having a first liquid  121  and a second liquid  122 . A refracting surface of the second lens unit  120   a  becomes concave or convex according to a voltage applied to the second lens unit  120   a.    
         [0078]    The first liquid  121  and the second liquid  122  may have different refractive indices so that the first liquid  111  and the second liquid  112  can function as a lens. One of the first liquid  121  and the second liquid  122  may be hydrophilic, and the second liquid  122  may be hydrophobic they do not mix with each other. For example, the first liquid  121  may be water with a refractive index of 1.33, and the second liquid  122  may be oil with a refractive index of 1.6. 
         [0079]    In addition, one of the first liquid  121  and the second liquid  122  may be conductive. When a voltage is applied to the conductive liquid, the interface may change due to the effect of an electric field. However, the present invention is not limited thereto, and other materials that satisfy the above conditions may also be used. That is, the first liquid  121  and the second liquid  122  may use materials identical to those of the first liquid  111  (see  FIG. 4 ) and the second liquid  112  (see  FIG. 4 ) included in the first lens unit  110   a  (see  FIG. 4 ) described above. 
         [0080]    The first liquid  121  and the second liquid  122  are separated from each other as a lower layer and an upper layer, respectively. Thus, an interface is formed between the first liquid  121  and the second liquid  122  on top of the first liquid  121 . 
         [0081]    A first electrode  125  is disposed on four sidewalls of the first liquid  121  and the second liquid  122 . The first electrode  125  may surround both liquids  121  and  122 . That is, the first electrode  125  may surround the interface S 2  between the liquids  121  and  122 . 
         [0082]    In addition, a second electrode  126  is disposed under the first liquid  121  and/or on the second liquid  122 . That is, the second electrode  126  may be disposed in contact with at least one of the first liquid  121  and the second liquid  122 . 
         [0083]    Referring to  FIG. 6 , when no voltage is applied to the first and second electrodes  125  and  126 , the first liquid  121  and the second liquid  122  are separated from each other as a lower layer and an upper layer, respectively. Thus, a flat interface is formed between the first liquid  121  and the second liquid  122 . In this case, light incident on the bottom of the first liquid  121  travels straight through the top of the second liquid  122  without refracting at the interface S 2 . 
         [0084]    Referring to  FIG. 7A , when voltages are applied to the first and second electrodes  125  and  126 , the interface S 2 ′ (“′” indicating that voltage is applied in  FIGS. 7A and 7B ) between the first liquid  121  and the second liquid  122  may be curved downward or upward. The electric field is not uniform within the first liquid  121  and the second liquid  122 . In this case, interface S 2 ′ between the liquids  121  and  122  is curved and thus functions as a concave lens or a convex lens. Here, since the second liquid  122  has a higher refractive index than the first liquid  121 , if the interface S 2 ′ is curved downward, it may function as a convex lens. 
         [0085]    Referring to  FIG. 7B , the interface S 2 ′ between the first liquid  121  and the second liquid  122  of the second lens unit  120  is curved downward to function as a convex lens. In this case, light incident on the bottom of the first liquid  121  is refracted at the interface S 2 ′ between the first liquid  121  and the second liquid  122 , and is curved to form a convex lens, light incident on the bottom of the first liquid  121  converges at a focal point of the convex lens and is output accordingly. A focal distance of the convex lens can be controlled by adjusting voltages applied to the first and second electrodes  125  and  126 . 
         [0086]    Hereinafter, a display device according to a second exemplary embodiment of the present invention will be described in detail with reference to  FIGS. 8A and 8B .  FIG. 8A  is a cross-sectional view of a first lens unit  210  included in the display device according to the second exemplary embodiment of the present invention.  FIG. 8B  is a cross-sectional view of the first lens unit  210  of  FIG. 8A  after an electric field is applied thereto. Elements having the same functions as those shown in the drawings for the first exemplary embodiment are indicated by like reference numerals, and thus their description will be omitted. 
         [0087]    The first lens unit  210  included in the display device according to the second exemplary embodiment includes a first layer  211 , a second layer  212 , and a third layer  213 . The first through third layers  211  to  213  are sequentially stacked from bottom to top in this order. The first and third layers  211  and  213  may be made of the same liquid, and the second layer  212  may be made of a liquid having a different refractive index from that of the liquid of the first and third layers  211  and  213 . That is, the first and third layers  211  and  213  may be made of, for example, the first liquid  111  (see  FIG. 4 ) described above in the first exemplary embodiment, and the second layer  212  may be made of the second liquid  112  (see  FIG. 4 ) of the first exemplary embodiment. 
         [0088]    First and second electrodes  215  and  216  are respectively disposed on both sides of the first and second layers  211  and  212  to face each other. In addition, third and fourth electrodes  217  and  218  are respectively disposed on both sides of the second and third layers  212  and  213  to face each other. 
         [0089]    The first and second electrodes  215  and  216  are separated from the third electrode  217  and the fourth electrode  218 , respectively. The first and second electrodes  215  and  216  control a first interface S 4 ′ between the first layer  211  and the second layer  212 , and the third and fourth electrodes  217  and  218  control a second interface S 3 ′ between the second and third layers  212  and  213 . As described above, when different voltages are applied to the first and second electrodes  215  and  216 , the first interface S 4 ′ tilts at an angle. In addition, when different voltages are applied to the third and fourth electrodes  217  and  218 , the second interface S 3 ′ tilts at an angle. That is, angles at which the first interface S 4 ′ and the second interface S 3 ′ tilt can be controlled independently by adjusting voltages applied to the first and second electrodes  215  and  216  and to the third and fourth electrodes  217  and  218 . 
         [0090]    Referring to  FIG. 8A , when no voltage is applied to any electrodes, the first and second interfaces S 4  and S 3  do not tilt but remain horizontal. Referring to  FIG. 8B , when voltages are applied to the first and second electrodes  216  and to the third and fourth electrodes  217  and  218 , the first and second boundary surfaces S 4  and S 3  tilt at predetermined angles with respect to a horizontal surface, respectively. Angles at which the first and second boundary surfaces S 4  and S 3  tilt with respect to the horizontal surface can be controlled independently by adjusting voltages applied to the first and second electrodes  215  and  216  independently of adjusting voltages applied to the third and fourth electrodes  217  and  218 . By adjusting voltages applied to the first and second electrodes  215  and  216  independently of adjusting voltages applied to the third and fourth electrodes  217  and  218 , the path of light incident on the bottom of the first layer  211  can be controlled more efficiently. 
         [0091]    Hereinafter, a display device  1  according to a third exemplary embodiment of the present invention will be described in detail with reference to  FIGS. 9 and 11 .  FIG. 9  is a perspective view of lens panels  300   a  and  300   b  and display panels  10   a  and  10   b  included in the display device  1  according to the third exemplary embodiment of the present invention.  FIG. 10  is a perspective view of a first lens unit  310   a  included in the display device  1  of  FIG. 9 .  FIG. 11  is a perspective view of a second lens unit  320   b  included in the display device  1  of  FIG. 9 . Elements having the same functions as those shown in the drawings for the first exemplary embodiment are indicated by like reference numerals, and thus their description will be omitted. 
         [0092]    Referring to  FIG. 9 , the first lens unit  310   a  and a second lens unit  320   a  are repeatedly formed along a non-display region  12   a  (not shown) of the display panel  10   a , and a first lens unit  310   b  and the second lens unit  320   b  are repeatedly formed along a non-display region  12   b  (not shown) of the display panel  10   b.  Thus, the first and second lens units  310   a  and  320   a  may overlap each row or column of pixels of the display panel  10   a,  and the first and second lens units  310   b  and  320   b  may overlap each row or column of pixels of the display panel  10   b.  That is, when each of the first and second lens units  310   a  and  320   a  or  310   b  and  320   b,  which are repeatedly formed along the non-display region  12   a  or  12   b,  is divided into a plurality of sections, each section of each of the first and second lens units  310   a  and  320   a  or  310   b  and  320   b  may be allocated to a pixel or a plurality of pixels. When each of the first and second lens units  310   a  and  320   a  or  310   b  and  320   b , which are repeatedly formed along the non-display region  12   a  or  12   b,  is not divided into a plurality of sections, it may be allocated to each row or column of pixels of the display panel  10   a  or  10   b.    
         [0093]    Referring to  FIG. 10 , the first lens unit  310   a  of the lens panel  300   a  may be shaped like a long rectangle. First and second electrodes  315  and  316  are respectively disposed on both sides of a first liquid  311  and a second liquid  312  to face each other. The first and second electrodes  315  and  316  may extend parallel to the non-display region  12   a.    
         [0094]    When voltages are applied to the first and second electrodes  315  and  316 , an interface S 5  between the first liquid  311  and the second liquid  312  tilts to a side to be parallel to the non-display region  12   a.    
         [0095]    Referring to  FIG. 11 , the second lens unit  320   b  of the lens panel  300   b  may be shaped like a long rectangle. Two first electrodes  325  are respectively disposed on both sides of a first liquid  321  and a second liquid  322  to face each other, and a second electrode  326  is disposed under the first liquid  321 . The same voltage is applied to the first electrodes  325  which are respectively disposed on both sides of the first liquid  321  and the second liquid  322  to face each other, and a voltage different from the voltage applied to the first electrodes  326  is applied to the second electrode  325 . 
         [0096]    When voltages are applied to the first and second electrodes  325  and  326 , an interface S 6  between the first liquid  321  and the second liquid  322  curves like a furrow to be parallel to the non-display region  12   b.  The interface S 6  may function as a concave lens or a convex lens. 
         [0097]    Hereinafter, a display device  1  according to a fourth exemplary embodiment of the present invention will be described in detail with reference to  FIGS. 12 and 13 .  FIG. 12  is a perspective view of display panels  10   a  through  10   c  and lens panels  400   a  through  400   c  included in the display device  1  according to the fourth exemplary embodiment of the present invention.  FIG. 13  is a schematic cross-sectional view of the display device  1  shown in  FIG. 12 . Elements having the same functions as those shown in the drawings for the first exemplary embodiment are indicated by like reference numerals, and thus their description will be omitted. 
         [0098]    Referring to  FIGS. 12 and 13 , each of the lens panels  400   a  through  400   c  is formed in a region of the display panel  10   a,    10   b,  or  10   c.  That is, since the lens panels  400   a  through  400   c  are designed to prevent non-display regions  12   a  and  12   b  of the display panels  10   a  and  10   b  and a non-display region (not shown) of the display panel  10   c  from being seen through the projection film  20 , each of the lens panels  400   a  through  400   c  may be formed only in a region of the display panel  10   a,    10   b,  or  10   c  which is adjacent to the non-display region  12   a,    12   b,  or the non-display region (not shown) of the display panel  10   c.    
         [0099]    Each of the lens panels  400   a  through  400   c  may be formed to a predetermined width along a corresponding one of the non-display regions  12   a  and  12   b  of the display panels  10   a  and  10   b  and the non-display region (not shown) of the display panel  10   c.  Each of the lens panels  400   a  and  400   b  may include only a first lens unit  410   a  or  410   b  which can control the path of light. Likewise, the lens panel  400   c  may include only a first lens unit (not shown) which can control the path of light. 
         [0100]    Regions of a projection film  20 , which respectively overlap display regions  11   a  and  11   b  of the display panels  10   a  and  10   b  and a display region (not shown) of the display panel  10   c,  may receive images directly from the display panels  10   a  through  10   c,  respectively. On the other hand, regions of the projection film  20 , which respectively overlap the non-display regions  12   a  and  12   b  of the display panels  10   a  and  10   b  and the non-display region (not shown) of the display panel  10   c,  may receive images from the display panels  10   a  through  10   c  through the first lens units  410   a  and  410   b  of the lens panels  400   a  and  400   b  and the first lens unit (not shown) of the lens panel  400   c,  respectively. 
         [0101]    Hereinafter, a method of forming a multi-display apparatus by arranging a plurality of display devices according to an exemplary embodiment of the present invention will be described in detail with reference to  FIGS. 14 and 15 .  FIG. 14  is a perspective view of a multi-display apparatus having a plurality of display devices  1   a  through  1   c  arranged adjacent to each other according to an exemplary embodiment of the present invention.  FIG. 15  is a schematic cross-sectional view of the multi-display apparatus shown in  FIG. 14 . Elements having the same functions as those shown in the drawings for the first exemplary embodiment are indicated by like reference numerals, and thus their description will be omitted. 
         [0102]    The display devices  1   a  through  1   c  may be connected to each other to form the multi-display apparatus. The display devices  1   a  through  1   c  may include lens panels  100   a  to  100   c  and projection films  520   a  through  520   c,  respectively. The projection films  520   a  through  520   c  may be as wide as the display panels  10   a  through  10   c  included in the display devices  1   a  through  1   c,  respectively. 
         [0103]    Each of the display devices  1   a  through  1   c  includes the projection film  520   a ,  520   b  or  520   c  on a top surface thereof. When the display devices  1   a  through  1   c  are arranged adjacent to each other, the projection films  520   a  through  520   c  are also arranged adjacent to each other. Therefore, the projection films  520   a  through  520   c  of the display devices  1   a  through  1   c  function as unit screens, and the unit screens are arranged adjacent to each other to form a large screen. 
         [0104]    When the display devices  1   a  through  1   c  are used separately, they function as separate devices. When the display devices  1   a  through  1   c  are arranged adjacent to each other, they form the multi-display apparatus and function as one large screen. The lens panels  100   a  through  100   c  magnify display regions of the display devices  1   a  through  1   c,  respectively, thereby minimizing the display of a non-display region of a large screen of the multi-display apparatus. 
         [0105]    While the present invention has been particularly shown and described with reference to exemplary embodiments thereof, it will be understood by those of ordinary skill in the art that various changes in form and detail may be made therein without departing from the spirit and scope of the present invention as defined by the following claims. The exemplary embodiments should be considered in a descriptive sense only and not for purposes of limitation.