Patent Abstract:
The present invention provides a light-importing system, direct-lit backlight module and liquid crystal display device. The light-importing system includes ambient light collection system, facing and collecting ambient light, and outputting absorbed light; a plurality of light-guiding devices, each having light-entering end and light-exiting end, light-entering end adjacent to ambient light collection system, the absorbed light entering light-entering end and guided to light-exiting end, the plurality of the light-exiting ends being arranged in an array format underneath a light-entering surface of a diffuser; and a plurality of light diffusion devices, each disposed between light-exiting end and light-entering surface, expanding the light-emitting angle of the light-exiting end. Because of light diffusion device disposed between light-exiting end and light-entering surface expanding light-emitting angle of light-exiting end, the phenomenon of uneven luminance between light-exiting ends is improved, leading to improvement of displaying quality of direct-lit backlight module.

Full Description:
BACKGROUND OF THE INVENTION 
       [0001]    1. Field of the Invention 
         [0002]    The present invention relates to the field of liquid crystal displaying techniques, and in particular to a light-importing system, direct-lit backlight module and liquid crystal display device. 
         [0003]    2. The Related Arts 
         [0004]    Recently, the backlight module of the liquid crystal display device uses mostly original light source as the backlight source. The original light source means the light source using electricity to emit light, such as, LED, and CCFL. The LED has the advantage of high energy efficiency, and is widely used as the backlight source in backlight modules. However, as the demands on even higher efficiency in energy consumption grow, the number of original light sources in the backlight module must be reduced to meet such a high standard. Alternatively, a new type of energy-saving light source must be developed as the backlight module to meet the demands. 
         [0005]    By using the ambient light, such as, sun light, as the backlight source in the backlight module is a new energy-saving approach. In this approach, the original light source relying on electricity is reduced or even eliminated to save the energy consumption. At present, a possibly feasible approach is to collect the ambient light and use a plurality of optical fibers to output the collected ambient light to the backlight module to serve as the backlight source of the backlight module. However, because the light-emitting angle at the light-exiting end is smaller, the luminance difference between the light-exit end and the front of the light-exiting end (i.e., between left and right of the light-exiting end) is large, which leads to distinct luminance difference. An even more severe case would show the distinct locations of each light-exiting end, which results in deterioration of the displaying quality. 
       SUMMARY OF THE INVENTION 
       [0006]    The present invention provides a light-importing system, applicable to direct-lit backlight module, which comprises: an ambient light collection system, configured to face the ambient light to absorb the ambient light and output the absorbed light; a plurality of light-guiding devices, each having a light-entering end and a light-exiting end, the light-entering end being adjacent to the ambient light collection system, the absorbed light entering the light-entering end and being guided to the light-exiting end, the plurality of the light-exiting ends being arranged in an array format underneath a light-entering surface of a diffuser; and a plurality of light diffusion devices, each disposed between the light-exiting end and the light-entering surface, configured to expand the light-emitting angle of the light-exiting end. 
         [0007]    The present invention provides a direct-lit backlight module, which comprises: a backplane, a reflector, a diffuser and an optical film; wherein the diffuser having a light-entering surface and a light-exiting surface, disposed oppositely; the reflector being disposed underneath the light-entering surface, the backplane being disposed underneath the reflector; the optical film being disposed above the light-exiting surface; wherein the direct-lit backlight module further comprising a light-importing system, the light-importing system, comprising: an ambient light collection system, configured to face the ambient light to absorb the ambient light and output the absorbed light; a plurality of light-guiding devices, each having a light-entering end and a light-exiting end, the light-entering end being adjacent to the ambient light collection system, the absorbed light entering the light-entering end and being guided to the light-exiting end, the plurality of the light-exiting ends being arranged in an array format underneath a light-entering surface of a diffuser; and a plurality of light diffusion devices, each disposed between the light-exiting end and the light-entering surface, configured to expand the light-emitting angle of the light-exiting end. 
         [0008]    The present invention provides a liquid crystal display device, which comprises: which comprises: a backplane, a reflector, a diffuser, an optical film and a display panel; wherein the diffuser having a light-entering surface and a light-exiting surface, disposed oppositely; the reflector being disposed underneath the light-entering surface, the backplane being disposed underneath the reflector; the optical film being disposed above the light-exiting surface; the display panel being disposed above the optical film; wherein the liquid crystal display device further comprising a light-importing system, the light-importing system, comprising: an ambient light collection system, configured to face the ambient light to absorb the ambient light and output the absorbed light; a plurality of light-guiding devices, each having a light-entering end and a light-exiting end, the light-entering end being adjacent to the ambient light collection system, the absorbed light entering the light-entering end and being guided to the light-exiting end, the plurality of the light-exiting ends being arranged in an array format underneath a light-entering surface of a diffuser; and a plurality of light diffusion devices, each disposed between the light-exiting end and the light-entering surface, configured to expand the light-emitting angle of the light-exiting end. 
         [0009]    According to a preferred embodiment of the present invention, the light-guiding device is optical fiber. 
         [0010]    According to a preferred embodiment of the present invention, the light diffusion device is a biconcave lens or a plano-concave lens. 
         [0011]    According to a preferred embodiment of the present invention, the light-exiting end is corresponding to the center of the light diffusion device, and the light diffusion device has a width meeting the following condition: W&lt;P, wherein W is the width of the light diffusion device and P is the distance between two adjacent light-exiting ends. 
         [0012]    According to a preferred embodiment of the present invention, the light-importing system further comprises a plurality of original light sources, and the plurality of original light sources and the plurality light-exiting ends are arranged interleavingly in an array format. 
         [0013]    According to a preferred embodiment of the present invention, the original light source is an LED. 
         [0014]    According to a preferred embodiment of the present invention, the light-exiting end is corresponding to the center of the light diffusion device, and the light diffusion device has a width meeting the following condition: W&lt;P 2 −L and W&lt;P 1 −L, wherein W is the width of the light diffusion device, P 1  is the distance between two adjacent light-exiting ends, P 2  is the distance between two adjacent original light sources and L is the width of the original light source. 
         [0015]    The efficacy of the present invention is that to be distinguished from the state of the art. According to the light-importing system, direct-lit backlight module and the liquid crystal display device of the present invention, the light-importing system imports the ambient light into the direct-lit backlight module to serve as the backlight source of the backlight module to reduce or eliminate the use of the original light source and save energy consumption. In addition, because of the light diffusion device disposed between the light-exiting end and the light-entering surface to expand the light-emitting angle of the light-exiting end, the phenomenon of uneven luminance between the light-exiting ends is improved, leading to improvement of displaying quality of direct-lit backlight module. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0016]    To make the technical solution of the embodiments according to the present invention, a brief description of the drawings that are necessary for the illustration of the embodiments will be given as follows. Apparently, the drawings described below show only example embodiments of the present invention and for those having ordinary skills in the art, other drawings may be easily obtained from these drawings without paying any creative effort. In the drawings: 
           [0017]      FIG. 1  is a schematic view showing the structure of a direct-lit backlight module of the first embodiment of the present invention; 
           [0018]      FIG. 2  is a schematic view showing the biconcave lens expanding the light-emitting angle of the light-exiting end in the first embodiment of the present invention; 
           [0019]      FIG. 3  is a schematic view showing the plano-concave lens expanding the light-emitting angle of the light-exiting end in the first embodiment of the present invention; 
           [0020]      FIG. 4  is a schematic view showing another disposition of the plano-concave lens of the first embodiment of the present invention; 
           [0021]      FIG. 5  a schematic view showing the structure of a direct-lit backlight module of the second embodiment of the present invention; and 
           [0022]      FIG. 6  is a schematic view showing the liquid crystal display device of the first embodiment or the second embodiment of the present invention. 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0023]    For description of the technical means and result of the present invention, the following refers to the drawings and embodiments for detailed description, wherein the same number indicates the same part. 
       The First Embodiment 
       [0024]    Referring to  FIG. 1 , the direct-lit backlight module  1  comprises: an ambient light collection system  10 , a plurality of optical fibers  20 , a plurality of biconcave lenses  40 , a backplane  50 , a diffuser  30 , an optical film  60  and a reflector  90 ; wherein the diffuser  30  comprises a light-entering surface  31  and a light-exiting surface  32 , disposed oppositely; the reflector  90  is disposed underneath the light-entering surface  31 , the backplane is disposed underneath the reflector  90 , and the optical film  60  is disposed above the light-exiting surface  32 . 
         [0025]    In the instant embodiment, the ambient light collection system  10 , the plurality of optical fibers  20  and the plurality of biconcave lenses  40  form a light-importing system, wherein each optical fiber has a light-exiting end  21  and a light-entering end  22 . The light-entering ends  22  of the plurality of optical fibers  20  are bundled together and placed adjacent to the ambient light collection system  10 . The light-exiting ends  21  of optical fibers  20  are arranged in an array format above the reflector  90 . In other words, the light-exiting ends  21  of optical fibers  20  are arranged in an array format underneath the light-entering surface  31 . Each biconcave lens  40  is disposed correspondingly between the light-exiting end  21  of the optical fiber  20  and the light-entering surface  31 . 
         [0026]    The ambient light collection system  10  faces the ambient light CL to absorb the ambient light CL and transform the ambient light CL into absorbed light SL to output. The ambient light CL can be sun light, lamp light or light from any light-emitting objects. The wavelength of the absorbed light SL is within the range of the visible light. In other words, the absorbed light SL can be used as backlight source for the backlight module. The absorbed light SL passes the light-entering end  22  to enter the optical fiber  20  and is propagated to the light-exiting end  21 . The light exiting the light-exiting end  21  passes the biconcave lens  40  and the light-entering surface  31  to enter the diffuser  30 . The diffuser  30  diffuses the entering light and the diffused light is emitted from the light-exiting surface  32 . In the instant embodiment, the optical fiber  20  is a preferred light-guiding device, and the loss in the optical fiber  20  is very low to ensure sufficient light reaching the light-exiting end  21 . As a light diffusion device, the biconcave lens  40  can expand the light-emitting angle of the light-exiting end. 
         [0027]    In the instant embodiment, for the light-emitting angle of the light-exiting end to be expanded to an maximum, the light-exiting end  21  is preferably disposed correspondingly to the center of the biconcave lens  40  and maintains a suitable distance from the biconcave lens  40 . The light emitted from the light-exiting end  21  passes the biconcave lens  40  to reach the light-entering surface. To minimize the uneven luminance phenomenon of the light-entering surface, the width of the biconcave lens  40  must satisfy the following equation (1): 
         [0000]        W&lt;P   (1)
       wherein W is the width of the biconcave lens  40 , and P is the distance between two adjacent light-exiting ends.       
 
         [0029]    The following describes the theory behind the biconcave lens  40  expanding the light-emitting angle of the light-exiting end in details. 
         [0030]    Also referring to  FIG. 2 , for any two rays  211 ,  212  of the light emitted from the light-exiting end  21 , assume that the biconcave lens  40  is not disposed between the light-exiting end  21  and light-entering surface  31 . The rays  211 ,  212  will travel along a straight line, i.e., the dash line in the figure, to form a light-emitting angle of M. However, as the biconcave lens  40  is disposed between the light-exiting end  21  and light-entering surface  31  in the present embodiment, the refraction occurs the interface between any concave surface of the biconcave lens  40  and the air for rays  211 ,  212 . This is caused by the refraction index of the biconcave lens  40  greater than the refraction index of the air, i.e., the rays  211 ,  212  will travel along the solid line in the figure. The dash line extending from the reverse direction of the solid line of the biconcave lens  40  forms a light-emitting angle of N. As shown, the light-emitting angle N is greater than the light-emitting angle M. Similarly, any other rays emitted from the light-exiting end  21  follows the same theory so that the light emitted from the light-exiting end  21  after the biconcave lens  40  is expanded. 
         [0031]    A plano-concave lens  41  can also be used to replace the biconcave lens  40 . The theory behind the plano-concave lens  41  expanding the light-emitting angle of the light-exiting end  21  is described as follows. 
         [0032]    Referring to  FIG. 3 , the concave surface of the plane-concave lens  41  is corresponding to the light-exiting end  21 . For any two rays  211 ,  212  of the light emitted from the light-exiting end  21 , assume that the plano-concave lens  41  is not disposed between the light-exiting end  21  and light-entering surface  31 . The rays  211 ,  212  will travel along a straight line, i.e., the dash line in the figure, to form a light-emitting angle of Q. However, as the plano-concave lens  41  is disposed between the light-exiting end  21  and light-entering surface  31  in the present embodiment, the refraction occurs the interface between the concave surface or the planar surface of the plano-concave lens  41  and the air for rays  211 ,  212 . This is caused by the refraction index of the plano-concave lens  41  greater than the refraction index of the air, i.e., the rays  211 ,  212  will travel along the solid line in the figure. The dash line extending from the reverse direction of the solid line of the plano-concave lens  41  forms a light-emitting angle of K. As shown, the light-emitting angle K is greater than the light-emitting angle Q. Similarly, any other rays emitted from the light-exiting end  21  follows the same theory so that the light emitted from the light-exiting end  21  after the plano-concave lens  41  is expanded. 
         [0033]    Referring to  FIG. 4 , the planar surface of the plano-concave lens  41  can also be corresponding to the light-exiting end  21 . The rays  211 ,  212  will be refracted first at the interface between the air and the planar surface of the plano-concave lens  41  and then refracted again at the interface between the air and the concave surface of the plano-concave lens  41 . As shown, the light-emitting angle K is greater than the light-emitting angle Q, and the light emitted from the light-exiting end  21  after the plano-concave lens  41  is expanded. 
       The Second Embodiment 
       [0034]    The part of the description of the second embodiment that is identical to the description of the first embodiment will not be repeated here. The following only describes different part. 
         [0035]    LED is often used as an original light source of the backlight module. Other original light sources include fluorescent light, CCFL or other light-emitting objects with electricity as power. 
         [0036]    Referring to  FIG. 5 , the direct-lit backlight module  1  can further comprise a plurality of LEDs  70 . The LEDs  70  and the light-exiting ends  21  are arranged interleavingly in an array format above the reflector  90 . That is, the LEDs  70  and the light-exiting ends  21  are arranged interleavingly in an array format underneath the light-entering surface  31 . The biconcave lens  40  is disposed between the light-exiting end  21  and the light-entering surface  31 . Alternatively, the plano-concave lens  41  can be used instead of biconcave lens  40 . With such structure, the LED  70  and the light-exiting ends  21  are used as the backlight source to reduce the number of LEDs used. In the present embodiment, the ambient light collection system  10 , the plurality of optical fibers  20 , the plurality of LEDs  70  and the plurality of biconcave lens  40  form the light-importing system. 
         [0037]    It should be noted that in the instant embodiment, for the light-emitting angle of the light-exiting end to be expanded to an maximum, the light-exiting end  21  is preferably disposed correspondingly to the center of the biconcave lens  40  and maintains a suitable distance from the biconcave lens  40 . The light emitted from the light-exiting end  21  passes the biconcave lens  40  to reach the light-entering surface. To minimize the uneven luminance phenomenon of the light-entering surface, the width of the biconcave lens  40  must satisfy the following equation (2): 
         [0000]        W&lt;P   2   −L  and  W&lt;P   1   −L   (2)
       wherein W is the width of the biconcave lens  40 , P 1  is the distance between two adjacent light-exiting ends, P 2  is the distance between two adjacent LEDs  70  and L is the width of the LED  70 .       
 
         [0039]    The direct-lit backlight module of the first or second embodiment is applicable to liquid crystal display device. The following describes a liquid crystal display device using the direct-lit backlight module of the first or second embodiment. 
         [0040]    Referring to  FIG. 6 , a display panel  80  is disposed on the direct-lit backlight module  1  to form a complete liquid crystal display device  2 . The direct-lit backlight module  1  provides uniformly distributed light source to the display panel  80  so that the display panel  80  has sufficient luminance to display images. 
         [0041]    In summary, the light-importing system imports the ambient light into the direct-lit backlight module to serve as backlight source to reduce or eliminate the use of original light source and save energy. In addition, the disposition of the biconcave lens or the plano-concave lens between the light-exiting end and the light-entering surface to expand the light-emitting angle will improve the uneven luminance phenomenon between light-exiting ends and improve the displaying quality of the direct-lit backlight module. 
         [0042]    Embodiments of the present invention have been described, but not intending to impose any unduly constraint to the appended claims. Any modification of equivalent structure or equivalent process made according to the disclosure and drawings of the present invention, or any application thereof, directly or indirectly, to other related fields of technique, is considered encompassed in the scope of protection defined by the clams of the present invention.

Technology Classification (CPC): 6