Abstract:
An exemplary optical guiding device for optically coupling a plurality of light beams having at least one laser beam, includes a light coupling lens, a light collimating lens, and an optical fiber. The light coupling lens and the light collimating lens are positioned apart along an optical path. The optical fiber is optically coupled to the light couple lens. External laser beam introduced by the optical fiber are optically coupled by the light coupling lens for collimating and mixing the light beams, then collimated by the at least one light collimating lens, and finally emitting out. A backlight module using the optical guiding device with colored semiconductor lasers and light transferring device are also provided. The backlight module has a good color performance, such as high color saturation.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to optical guiding devices, particularly, to an optical guiding device guiding at least a laser beam, and backlight modules using the optical guiding device. 
     2. Discussion of the Related Art 
     In a liquid crystal display device (LCD device), a liquid crystal is a substance that does not illuminate light by itself. Instead, the liquid crystal propagates (transmits) light received from a light source to display information. In the case of a typical liquid crystal display device, a backlight module powered by electricity supplies the needed light. 
     With the development of LCD technology, large-size LCD devices have been actively sought and researched. The larger the backlight modules, the higher the power consumption and the materials needed. To minimize the power consumption of the larger LCD devices, the backlight module of the larger LCD devices would usually employ fewer light sources. However, decreasing the light sources would decrease the optical performance of the backlight module, such as brightness, light output uniformity, and so on. Thus, affecting the display performance of the large-size LCD. Typically, backlight modules are classified into an edge lighting type or a bottom lighting type based upon the position of the light sources in the LCD devices. By employing the edge lighting type backlight module allows the LCD to adopt a thinner width, most of the large-size LCD devices employ the edge lighting type backlight module. 
     Referring to  FIG. 13 , a typical edge lighting type backlight module  100  includes two cold cathode fluorescence lamps (CCFLs)  11 , a light guide plate  12 , a plurality of complementary optical elements  13 , a light reflective sheet  14 , a receiving frame  15  and a bottom frame  16 . The two CCFLs  11  are disposed adjacent to two opposite side surfaces of the light guide plate  12 . The optical elements  13  include a first light diffusion sheet  131 , a prism sheet  132 , and a second diffusion sheet  133  stacked on the light guide plate  12  in that order. The light reflective sheet  14  is positioned under the light guide plate  12 . The receiving frame  15  and the bottom frame  16  cooperatively form a receiving space. The CCFLs  11 , the light guide plate  12 , the optical elements  13  and the light reflective sheet  14 , are assembled in the receiving space together. 
     Generally, an optical efficiency of a CCFL is relatively high, however, the volume of the CCFL is large and the power consumption of the CCFL is high. Furthermore, CCFL only covers about 75 percent of color saturation as defined by the National Television Standards Committee (NTSC). Therefore, the CCFL cannot satisfy high quality liquid crystal display requirements. 
     What is needed, therefore, is a new backlight module that overcomes the above mentioned disadvantages. 
     SUMMARY 
     An optical guiding device for optically coupling a plurality of light beams having three laser beam according to a preferred embodiment, includes a light coupling lens, a light collimating lens, and three optical fibers. The light coupling lens and the light collimating lens are positioned apart along an optical path. The optical fibers are optically coupled to the light couple lens. External laser beam introduced by the optical fiber are optically coupled by the light coupling lens for collimating and mixing the light beams, then collimated by the light collimating lens, and finally emitting out. 
     A backlight module includes a plurality of light sources having three colored semiconductor lasers, a light guide plate, a light transferring device and an optical guiding device. The optical guiding device is same as described in a previous paragraph. The optical guiding device and the light transferring device are position near the light guide plate. Laser beam from the three colored semiconductor lasers are optically coupled by the light coupling lens for collimating and mixing the light beams, then collimated by the light collimating lens, and finally are reflected and redirected by the light transferring device to enter the light guide plate. 
     Other advantages and novel features will become more apparent from the following detailed description of the preferred embodiments, when taken in conjunction with the accompanying drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The components in the drawings are not necessarily drawn to scale, the emphasis instead being placed upon clearly illustrating the principles of the present optical guiding device and backlight module. Moreover, in the drawings, like reference numerals designate corresponding parts throughout the several views, and all the views are schematic. 
         FIG. 1  is an exploded, isometric view of a backlight module according to a first preferred embodiment of the present invention, the backlight module having an optical guiding device and a light transfer unit. 
         FIG. 2  is an isometric view of the optical guiding device of  FIG. 1 , the optical guiding device having three light collimating lenses. 
         FIG. 3  is a cross-sectional view of the light collimating lens of  FIG. 2 . 
         FIG. 4  is an isometric view of the light transfer unit of  FIG. 1 . 
         FIG. 5  is a top plan view of the backlight module of  FIG. 1 . 
         FIG. 6  is an enlarged view of a circle portion VI of  FIG. 5 . 
         FIG. 7  is an exploded, isometric view of a backlight module according to a second preferred embodiment of the present invention. 
         FIG. 8  is an exploded, isometric view of a backlight module according to a third preferred embodiment of the present invention. 
         FIG. 9  is an exploded, isometric view of a backlight module according to a fourth preferred embodiment of the present invention. 
         FIG. 10  is an enlarged view of a circle portion X of  FIG. 9 . 
         FIG. 11  is an exploded, isometric view of a backlight module according to a fifth preferred embodiment of the present invention. 
         FIG. 12  is an abbreviated, assembled, cross-sectional view of the backlight module of  FIG. 11 . 
         FIG. 13  is an exploded, isometric view of a conventional backlight module. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Reference will now be made to the drawings to describe preferred embodiments of the present optical guiding device and backlight module using the optical guiding device, in detail. 
     Referring to  FIG. 1 , a backlight module  200  in accordance with a first preferred embodiment of the present invention is shown. The backlight module  200  includes three colored semiconductor lasers  20 , an optical guiding device  21 , a rotating reflector apparatus  22 , a light guide plate  23 , a plurality of complementary optical elements  24 , a light reflective sheet  25 , a receiving frame  26 , and a bottom frame  27 . 
     The optical guiding device  21  is on a side of the light guide plate  23 , and the rotating reflector apparatus  22  are disposed in a corner on the same side. The optical elements  24  include a first light diffusion sheet  241 , a prism sheet  242 , and a second diffusion sheet  243  stacked on the light guide plate  23  in that order. The light reflective sheet  25  is positioned under the light guide plate  23 . The receiving frame  26  and the bottom frame  27  cooperatively form a receiving space  28 . The colored semiconductor lasers  20 , the optical guiding device  21 , the rotating reflector apparatus  22 , the light guide plate  23 , the optical elements  24 , and the light reflective sheet  25  are all assembled in the receiving space  28 . 
     Referring to  FIG. 2 , in the first embodiment, the optical guiding device  21  includes a casing  210 , three optical fibers  211 , three light coupling lenses  212 , and three light collimating lenses  213 . The casing  210  is substantially an oblong cuboid defining a hollow cavity communicating with opposite ends of the casing  210 , thus defining a light input opening  2101  and a light output opening  2102  correspondingly. The light input opening  2101  and the light output opening  2102  are located at opposite ends of the casing  210 . Each of the three light coupling lenses  212  is disposed on a lens support  215  that extends out of the casing  210  adjacent to the light input opening  2101 . The light coupling lenses  212  and the lens supports  215  are arranged in the casing  210  such that the focal points of the light coupling lenses  212  are aligned. Each of the three collimating lenses  213  is disposed on other lens support  215  that extends out of the casing  210  adjacent to the light output opening  2102 . The focal points of the light coupling lenses  212  and the light collimating lenses  213  lie on a same optical path in the casing  210  (for example, a center axis of the casing  210 ). An end of each of the three optical fibers  211  is optically coupled to the light coupling lens  212  adjacent to the light input opening  2101  correspondingly. The other end of the three optical fibers  211  is optically connected to the three colored semiconductor lasers  20  (such as red, blue, green semiconductor lasers) respectively. 
     Referring to  FIG. 3 , the light collimating lenses  213  are Fresnel lenses. In use, laser beams from the colored semiconductor lasers are projected into the optical fibers  211  and out toward the optical guiding device  21 , then the laser beams are optically coupled together by the three light coupling lenses  212  that collimate and mix the laser beams. Finally the laser beams are collimated again by the three light collimating lenses  213  and exit out through the light output opening  2102  of the casing  210 . 
     Referring to  FIG. 4 , the rotating reflector apparatus  22  includes a multi-faced prism  221  and a server motor  223 . The vertical side of the multi-faced prism  221  is attached to the rotor of the sever motor  223  such that a center of axis of the multi-faced prism  221  is aligned with the rotational axis of the rotor. The server motor  223  is configured for rotating the multi-faced prism  221  at predetermined rotation per minute (rpm). In the illustrated embodiment, the multi-faced prism  221  is an eight-faced prism having eight reflective lateral faces. In the preferred embodiment, the lateral faces are mirrors. 
     Referring to  FIGS. 5 and 6 , in the first embodiment, the adjacent corners of the same side of the light guide plate  23  defines a first cutout  231  and a second cutout  232  correspondingly. The first cutout  231  is elongated rectangular in shape. The second cutout  232  defines a curved-shaped corner. The rotating reflector apparatus  22  is disposed in the second cutout  232  and the optical guiding device  21  is disposed in the first cutout  231  facing the rotating reflector apparatus  22 . In use, the rotating multi-faced prism  221  of the rotating reflector apparatus  22  reflects the focused light beams ( 21   a ,  21   b ) from the optical guiding device  21  into the light guide plate  23 . 
     It should be pointed out, the colored semiconductor lasers  20  can be positioned outside the receiving space  28 , as long as the colored semiconductor lasers  20  are connected to the optical guiding device  21  by the optical fibers  211 . 
     In alternative embodiments, the lens supports  215  can be omitted, and the light coupling lenses  212  and the light collimating lens  213  are instead substantially permanently positioned on the casing  210  using glue, or, the light coupling lenses  212  and the light collimating lens  213  are fixed to the casing  210  by using fastener structures formed in the casing  210 . 
     According to the shape of the light guide plate  23 , the multi-faced prism  221  of the rotating reflector apparatus  22  can be selected from one of four-faced prism, six-faced prism, twelve-faced prism and so on. For example, if the light guide plate  23  is triangular in shape, the multi-faced prism  221  is preferable to be a twelve-faced prism. 
     It should be also pointed out that, one or more of colored semiconductor lasers  20  and other light sources, such as colored light emitting diode (LED), can be used in the backlight module  200 . Laser beams from the colored semiconductor lasers  20  or other light beams from the LED can be projected into the optical guiding device  21  together. The optical guiding device  21  may have only one light coupling lens  212 , and only one light collimating lens  213  to mix and collimate the laser beams and other light beams. Alternatively, referring to  FIG. 2  again, between the light coupling lens  212  and the light output opening  2102  of the casing  210  define a space. The space can be filled with solid glue materials for fixing the optical fibers  211  tightly. 
     Referring to  FIG. 7 , a backlight module  300 , in accordance with a second preferred embodiment of the present invention, is similar in principle to the backlight module  200  of the first embodiment. However, the backlight module  300  has a light guide rod  32  for replacing the rotating reflector apparatus  22  of the backlight module  200 . An optical guiding device  31  and the light guide rod  32  are aligned in a line adjacent to one side surface of the light guide plate  33 . The light guide rod  32  is wedgy, and includes a light incident surface  320 , a light emitting surface  321 , and a light reflective surface  322 . The light incident surface  320  is an end surface of the light guide rod  32 . A light output opening  3142  of the optical guiding device  31  is in contact with light incident surface  320 . The light emitting surface  321  adjoins to the light incident surface  320  and faces one side surface of the light guide plate  33 . The light reflective surface  322  is opposite to the light emitting surface  321 , and also oblique with respect to the light emitting surface  321 . 
     Alternatively, the light reflective surface  322  may be omitted, if the backlight module  300  further includes a reflector  38  partially surrounding the light guide rod  32 . In use, laser beams  31   a  emitted from the optical guiding device  31  enter into the light guide rod  32  via the light incident surface  320 , then are reflected by the light reflective surface  322 , and finally the laser beams  31   b  emit out from the light guide rod  32  via the light emitting surface  321 . 
     Referring to  FIG. 8 , a backlight module  400 , in accordance with a third preferred embodiment of the present invention, is similar in principle to the backlight module  300  of the second embodiment. However, an optical guiding device  41  of the backlight module  400  is positioned adjacent to one end of one side surface of a light guide plate  43 ; a light guide rod  42  is positioned adjacent to another adjacent side surface of the light guide plate  43 . A light output opening  4142  of the optical guiding device  41  is in contact with the light guide rod  42 . The light guide rod  42  is similar to the light guide rod  32 , except that the light guide rod  42  has an inclined end surface  420  facing the light output opening  4142  of the optical guiding device  41 . The inclined end surface  420  is a mirror surface for reflecting the laser beams  41   a  from the optical guiding device  41  towards light reflective surface  422  of the light guide rod  42 . The laser beams  41   a  are reflected by the light reflective surface  422 , and finally the laser beams  41   b  emit out from the light guide rod  42  via light emitting surface  421 . 
     Referring to  FIG. 9 , a backlight module  500 , in accordance with a fourth preferred embodiment of the present invention, is similar in principle to the backlight module  400  of the third embodiment. However, an optical guiding device  51  of the backlight module  500  is disposed under a light guide plate  53  adjoining to one end of one side surface of the light guide plate  53 ; a light guide rod  52  further includes a multi-faced protuberance  520  extending from one end surface of the light guide rod  52 . The light guide rod  52  is disposed near to adjacent side surface of the light guide plate  53 . 
     Referring to  FIG. 10 , the multi-faced protuberance  520  includes a trapeziform incident surface  5203 , a first mirror surface  5201  and a second mirror surface  5202 . The trapeziform incident surface  5203  is in contact with the optical guiding device  51 . The first mirror surface  5201  faces the light output opening  5142  of the optical guiding device  51  and adjoins to the trapeziform incident surface  5203 . The second mirror surface  5202  is opposite to the first mirror surface  5201 . Light beams emitted from the optical guiding device  51  are introduced into the light guide rod  52  by being redirected at the first mirror surface  5201  and the second mirror surface  5202  in that order. It is should be noted that the optical guiding device  51 , the light guide rod  52  are not positioned in a same plane. 
     Referring to  FIGS. 11 and 12 , a backlight module  600 , in accordance with a fifth preferred embodiment of the present invention, is similar in principle to the backlight module  400  of the third embodiment. The backlight module  600  includes an optical guiding device  61 , a light guide rod  62  and a light guide plate  63 . However, the optical guiding device  61  and the light guide rod  62  are both positioned under the light guide plate  63 , and both adjoin to bottom edges of adjacent side surface of the light guide plate  63 . The optical guiding device  61  and the light guide rod  62  are in contact with each other. The backlight module further includes a reflector  68  that extends from a bottom surface of the light guide rod  62  to a top surface of the light guide plate  63 . The reflector  68  is configured to reflect light beams from the light guide rod  62  into the light guide plate  63 . 
     In the backlight modules  200 ,  300 ,  400 ,  500 ,  600 , laser beams from the colored semiconductor lasers  20  can be mixed by the optical guiding device  21 ,  31 ,  41 ,  51 ,  61 . Because the laser beams have excellent optical transmission property, the laser beams can be reflected and/or redirected into the light guide plate  23 ,  33 ,  43 ,  53 ,  63  by a light optical device such as rotating reflector apparatus  22  and light guide rods  32 ,  42 ,  52 ,  62 . The backlight module has a good color performance due to the high color saturation and excellent light transmission of the laser beam. 
     Finally, while the present invention has been described with reference to particular embodiments, the description is illustrative of the invention and is not to be construed as limiting the invention. Therefore, various modifications can be made to the embodiments by those skilled in the art without departing from the true spirit and scope of the invention as defined by the appended claims.