Abstract:
A liquid crystal display (LCD) inspection apparatus is provided which is capable of preventing detection of defects from being omitted or degraded due to formation of stains in a certain region of an LCD panel in an inspection of the LCD panel.

Description:
This application claims the benefit of Korean Patent Application No. 10-2005-080041, filed on Aug. 30, 2005, which is hereby incorporated by reference as if fully set forth herein. 
     BACKGROUND 
     1. Field of the Invention 
     The present invention relates to an apparatus that inspects a panel of a liquid crystal display (LCD). 
     2. Discussion of the Related Art 
     Generally, LCD inspection apparatuses are adapted to easily inspect, with the naked eye, whether or not an LCD panel is defective. 
       FIGS. 1 and 2  illustrate a conventional LCD inspection apparatus. As shown in  FIGS. 1 and 2 , the conventional LCD inspection apparatus includes a body  1 , an inspection stage  2  arranged at one side of the body  1 , to perform an inspection of an LCD panel  10 , to be inspected, and a loading/unloading stage  7  which is arranged at the other side of the body  1 , to load the LCD panel  10 , to be inspected, in the inspection stage  2 , and to unload the inspected LCD panel  10  from the inspection stage  2 . 
     As seen in  FIG. 2 , the LCD inspection apparatus includes a carrier  9  which is mounted to the body  1  such that the carrier  9  is laterally movable. The carrier transfer, the LCD panel  10  from the loading/unloading stage  7  to the inspection stage  2 , or from the inspection stage  2  to the loading/unloading stage  7 . 
     The inspection stage  2  includes probe units  3 , and a worktable  4  which brings the LCD panel  10  into contact with the probe units  3 . The worktable  4  also provides light. The worktable  4  includes a polarizing unit  4   a  and a backlight  4   b  which are arranged at a front portion of the worktable  4 , in this order. A moving stage  5  is arranged at the rear of the worktable  4 , and is connected to the probe units  3  in a state of being aligned with the probe units  3 . 
     A sub table  8  is mounted to the loading/unloading stage  7 . The sub table  8  functions to incline the LCD panel  10  transferred from a loader (not shown) of the loading/unloading stage  7  by a predetermined angle (for example, 60°). 
     A microscope  6  is mounted to the body  1  in front of the inspection stage  2  such that the microscope  6  is movable in vertical and lateral directions. When it is determined, in a macroscopic inspection operation, that the LCD panel  10  has defects, the operator can more precisely identify the defects of the LCD panel  10 , using the microscope  6 . 
     An inspection procedure carried out in the above-mentioned conventional LCD inspection apparatus will be described in brief. 
     A LCD panel  10  to be inspected is transferred from the loader (not shown) of the loading/unloading stage  7  to the sub table  8  which, in turn, transfers the LCD panel  10  to the carrier  9  while being inclined by a predetermined angle. Subsequently, the carrier  9  feeds the LCD panel  10  to the inspection stage  2 . When the LCD panel  10  is placed in the inspection stage  2 , the worktable  4  is moved toward the LCD panel  10  in accordance with operation of the moving stage  5 . The worktable  4  vacuum-chucks the LCD panel  10  such that the LCD panel  10  is maintained in a fixed state, and then connects pads (not shown) of the fixed LCD panel  10  to lead pins (not shown) of the probe units  3 , respectively. 
     When electrical connection is achieved between the LCD panel  10  and the probe units  3 , as mentioned above, a predetermined image signal from a pattern generator is input to the LCD panel  10  via the probe units  3 . The pattern generator, which is an external image signal input unit, sequentially provides various image patterns. When the LCD panel  10  is illuminated by the backlight  4   b , such various image patterns are sequentially displayed on the LCD panel  10 . Accordingly, the operator can determine whether or not the LCD panel  10  is defective, through the displayed patterns. 
     As shown in  FIG. 3A , the polarizing unit  4   a  of the above-mentioned conventional LCD inspection apparatus includes a polarizing plate  42 , a diffusing plate  43 , and a light guide plate  44  which are laminated over one another in a uniformly-spaced state. 
     In the polarizing unit  4   a  having the above-mentioned structure the diffusing plate  43  may be expanded due to hot air generated during light emission of the backlight unit  4   b  carried out in an inspection of the LCD panel  10 , as shown in  FIG. 3B . Due to the expansion of the diffusing plate  43 , non-uniform gap regions “a” are formed in gaps between the diffusing plate  43  and the polarizing plate  42  and between the diffusing plate  43  and the light guide plate  44 . Such non-uniform gap regions “a” may be exhibited in the form of stains in an image displayed on the LCD panel  10  in the inspection of the LCD panel  10 . 
     Boundary regions of stains present in an image displayed on the LCD panel  10  in an inspection of the LCD panel  10  are excluded from inspection regions. This is because the stain boundary regions are detected as defects. 
     Since no inspection is carried out for the stain boundary regions, there is a problem in that it is impossible to detect substantial defects, for example, point defects (PDs) or line defects (LDs), present in the stain boundary regions. 
     In order to detect substantial defects present in the non-inspected regions, an additional precise inspection must be carried out for the non-inspected regions. In this case the total task time (namely, the total inspection time for the LCD panel) is increased. 
     SUMMARY 
     The present invention is directed to an LCD inspection apparatus that substantially obviates one or more problems due to limitations and disadvantages of the related art. 
     A LCD inspection apparatus is provided that comprises a worktable with a forwardly-open hollow box structure that supports an LCD panel seated on a front side of the worktable. On the front side of the worktable probe units are arranged and are electrically connected to pads of the LCD panel supported by the worktable. At a rear side of the worktable a backlight unit is arranged inside the worktable and is adapted to emit light toward the LCD panel. At the front side of the worktable a polarizing unit is arranged inside the worktable to polarize light. The polarizing unit includes a first glass sheet. A polarizing plate coated over a front surface of the first glass sheet such that the polarizing plate is integrated with the first glass sheet. A diffusing plate formed at a back surface of the first glass sheet such that the diffusing plate is integrated with the first glass sheet, and a light guide plate arranged at a rear surface of the diffusing plate. 
     In another embodiment of the present invention, an LCD inspection apparatus comprises a polarizing unit adapted to polarize light supplied to an LCD panel. The polarizing unit includes a first glass sheet. A polarizing plate coated over a front surface of the first glass sheet such that the polarizing plate is integrated with the first glass sheet. A diffusing plate formed at a back surface of the first glass sheet such that the diffusing plate is integrated with the first glass sheet, and a light guide plate arranged at a rear surface of the diffusing plate. 
     It is to be understood that both the foregoing general description and the following detailed description of the present invention are exemplary and explanatory and are intended to provide further explanation of the invention as claimed. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The accompanying drawings, which are included to provide a further understanding of the invention and are incorporated in and constitute a part of this application, illustrate embodiment(s) of the invention and together with the description serve to explain the principle of the invention. In the drawings: 
         FIG. 1  is a front view schematically illustrating a conventional LCD inspection apparatus; 
         FIG. 2  is a side view of the LCD inspection apparatus shown in  FIG. 1 ; 
         FIGS. 3A and 3B  are enlarged sectional views illustrating a detailed structure of a polarizing unit included in the conventional LCD inspection apparatus; 
         FIG. 4  is a lateral sectional view schematically illustrating an LCD inspection apparatus according to a first embodiment of the present invention; 
         FIG. 5  is an enlarged sectional view illustrating a detailed structure of a polarizing unit included in the LCD inspection apparatus according to the first embodiment of the present invention; and 
         FIG. 6  is an enlarged sectional view illustrating a detailed structure of a polarizing unit included in an LCD inspection apparatus according to a second embodiment of the present invention. 
     
    
    
     DETAILED DESCRIPTION 
     Reference will now be made in detail to the preferred embodiments of the present invention associated with an LCD inspection apparatus according to the present invention, examples of which are illustrated in the  FIGS. 4 to 6 . Wherever possible, the same reference numbers will be used throughout the drawings to refer to the same or like parts. 
       FIG. 4  is a lateral sectional view schematically illustrating an LCD inspection apparatus according to a first embodiment of the present invention. As shown in  FIG. 4 , the LCD inspection apparatus according to the first embodiment of the present invention mainly includes a worktable  110 , probe units  120 , a backlight unit  130 , and a polarizing unit  160 . 
     The worktable  110  has a substantially-square hollow box structure which is longitudinally open. An LCD panel  10  is seated on a front side of the worktable  110 . 
     The probe units  120  are arranged in front of the front side of the worktable  110 . The probe units  120  receive image signals of various patterns for inspection of the LCD panel  10  from a pattern generator  153 , and supply the received image signals to the LCD panel  10 . 
     The LCD inspection apparatus also includes a moving stage  140  which is arranged outside the worktable  110  at the rear of the worktable  110 . The moving stage  140  functions to align the worktable  110  with the probe units  120 , and to connect the worktable  110  to the probe units  120 . 
     The backlight unit  130  is arranged in the worktable  110  at the rear side of the worktable  110 , to supply light to the LCD panel  10  seated on the front side of the worktable  110 . Preferably, the backlight unit  130  includes a lamp which is one of a cold fluorescent lamp (CFL), a cold cathode fluorescent lamp (CCFL), an external electrode fluorescent lamp (EEFL), and a high-brightness light emitting diode (LED). It is preferred that the backlight unit  130  be integrated with the worktable  110 . 
     The polarizing unit  160  is arranged inside the worktable  110  at the front side of the worktable  110 . The polarizing unit  160  functions to polarize light emitted from the backlight unit  130 , and to guide the polarized light to be irradiated to the LCD panel  10 . 
       FIG. 5  is a lateral sectional view illustrating a detailed structure of the polarizing unit  160 . 
     In accordance with the first embodiment of the present invention, the polarizing unit  160  mainly includes a first glass sheet  161 , a polarizing plate  162 , a diffusing plate  163 , and a light guide plate  164 . Preferably, the first glass sheet  161  is made of heat-resistant glass having a low thermal expansion coefficient. 
     The polarizing plate  162  changes the optical path of light emitted from the backlight unit  130  such that the light is incident to the LCD panel  10 . The polarizing plate  162  is coated over a front surface of the first glass sheet  161  such that the polarizing plate  162  is integrated with the first glass sheet  161 . 
     The diffusing plate  163  functions to diffuse the light incident to the LCD panel  10 , in order to enhance the uniformity of the incidence light. The diffusing plate  163  is integrated with a back surface of the first glass sheet  161 . 
     The diffusing plate  163  is coated over the back surface of the first glass sheet  161  in the form of a thin film such that the diffusing plate  163  is integrated with the first glass sheet  161 . 
     The diffusing plate  163  may be formed to have an adhesive front surface. The diffusing plate  163  can be bonded, at the adhesive front surface thereof, to the back surface of the first glass sheet  161  so that the diffusing plate  163  can be integrated with the first glass sheet  161 . 
     The light guide plate  164  functions to uniformly scatter the light emitted from the backlight unit  130  over a wide area. The light guide plate  164  is arranged at a back surface of the diffusing plate  163 . 
     Although not shown, the light guide plate  164  may also be integrated with the diffusing plate  163 . In this case, the polarizing plate  162 , first glass sheet  161 , diffusing plate  163 , and light guide plate  164  form an integrated structure. 
     A procedure for supplying light emitted from the backlight unit  130  to the LCD panel  10  in an inspection of the LCD panel  10  carried out using the above-described LCD inspection apparatus according to the first embodiment of the present invention will be described in detail. 
     When the worktable  110  is forwardly moved in accordance with a driving operation of the moving stage  140  under the condition in which the LCD panel  10  has been seated on the front side of the worktable  110 , electrical connection is achieved between the LCD panel  10  and the probe units  120 . Image signals of various patterns are sequentially applied from the pattern generator  190  to the LCD panel  10  via the probe units  120 . The backlight unit  130  then emits light which is, in turn, scattered over a wide area while passing through the light guide plate  164 . The scattered light is then uniformly diffused while passing through the diffusing plate  163 . Subsequently, the light passes through the first glass sheet  161  and polarizing plate  162 , in this order. The light emerging from the polarizing plate  162  is irradiated to the LCD panel  10  in a polarized state. 
     During the above-described procedure, the interior of the worktable  110  is heated to a high temperature due to the light emission of the backlight unit  130 . However, the diffusing plate  163  exhibits no or little deformation caused by thermal expansion because it is coated over the first glass sheet  161  made of heat-resistant glass in an integrated state. 
     Thus, no stain is formed in each pattern image displayed on the LCD panel  10 . Accordingly, it is possible to prevent detection of defects from being omitted due to formation of stains. 
       FIG. 6  illustrates a polarizing unit according to a second embodiment of the present invention. 
     As shown in  FIG. 6 , the polarizing unit  160  according to the second embodiment of the present invention includes a second glass sheet  165 , in addition to the configuration according to the first embodiment of the present invention. 
     The second glass sheet  165  is integrated with the back surface of the diffusing plate  163 . Preferably, the diffusing plate  163  is coated, at the back surface thereof, over a front surface of the second glass sheet  165 . 
     Although not shown, the light guide plate  164  may be integrated with a back surface of the second glass sheet  165 . Thus, the polarizing plate  162 , first glass sheet  161 , diffusing plate  163 , second glass sheet  615 , and light guide plate  164  form an integrated structure. 
     The above-described polarizing unit  160  according to the second embodiment of the present invention has a structure in which the diffusing plate  163  is arranged between the first and second glass sheets  161  and  165  while being integrated with the first and second glass sheets  161  and  165 , thereby being capable of further suppressing expansion of the diffusing plate  163  caused by high temperature. The second glass sheet  165  may be made of heat-resistant glass having a low thermal expansion coefficient. 
     The polarizing unit  160  is not limited to appliances which have the same configuration as the LCD inspection apparatus according to each embodiment of the present invention as described above. For example, the polarizing unit  160  may be applied to arrangements other than the arrangement in which the polarizing unit  160  is arranged inside the worktable  110 . The polarizing unit  160  according to each embodiment of the present invention may be applied to modular appliances (for example, LCD monitors, LCD TVs, or mobile phones). Thus, the polarizing unit of the present invention is useful in that it is applicable to various arrangements. 
     As apparent from the above description, the LCD inspection apparatus of the present invention can be implemented in the form of a single modular product because the polarizing unit and backlight unit are arranged in the worktable. Accordingly, the LCD inspection apparatus has an effect capable of achieving a convenient assembly process in the manufacture of the LCD inspection apparatus. 
     Since the polarizing plate, first glass sheet, and diffusing plate, which constitute the polarizing unit, form an integrated structure in accordance with the present invention, the LCD inspection apparatus of the present invention has an effect capable of suppressing expansion of the diffusing plate caused by hot air generated from the backlight unit. 
     Since it is possible to positively suppress expansion of the diffusing plate, no stain is formed in an image displayed on the LCD panel during an inspection of the LCD panel. Accordingly, it is possible to prevent detection of defects from being omitted due to formation of stains. 
     The LCD inspection apparatus according to the second embodiment of the present invention effectively suppresses deformation of the diffusing plate because the polarizing unit further includes the second glass sheet, with which the diffusing plate integrated with the first glass sheet is integrated at the back surface thereof. 
     It will be apparent to those skilled in the art that various modifications and variations can be made in the present invention without departing from the spirit or scope of the inventions. Thus, it is intended that the present invention covers the modifications and variations of this invention provided they come within the scope of the appended claims and their equivalents.