Patent Abstract:
A computer display is disclosed. The computer display includes a LCD housing, a light source coupled to the LCD housing, and a LCD coupled to the LCD housing. The LCD housing conducts light from the light source to the LCD. A method for conducting light is also disclosed. The method includes generating light and conducting the generated light through a LCD housing.

Full Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates generally to flat panel display systems. More particularly, the present invention relates to methods and apparatus for backlighting a liquid crystal display (LCD). Even more particularly, the present invention relates to backlighting a LCD on a laptop computer. 
     2. Description of the Prior Art 
     A conventional laptop computer, such as the laptop computer shown in  FIG. 1 , utilizes a “fliptop” display to display computer data. The fliptop display is generally perpendicular to the body of the laptop computer when the laptop is in use, allowing the user to view the displayed computer data. When the laptop computer is not in use, the fliptop display is folded down into a closed position so that it is substantially parallel to the body of the computer. 
     The prior art fliptop display assemblies include a LCD housing. The LCD housing is typically hinged to the body of the laptop computer and generally operates as a protective cover for the LCD module. 
     Prior art fliptop displays also include an LCD module. The LCD module includes an LCD and a means for “backlighting” the LCD. Backlighting refers to generating light behind the LCD and uniformly projecting it through the LCD. Prior art backlighting techniques generally involve the use of a light source and a light pipe composed of light transmissive material located adjacent to the LCD. United U.S. Pat. No. 5,050,946, which is incorporated herein by reference, discusses various light source and light pipe designs. 
     A cross sectional view of a conventional fliptop display  2  is shown in  FIG. 2 . As shown in  FIG. 2 , the conventional fliptop display  2  includes an LCD housing  10  and an LCD module  15 . The LCD housing  10  is composed of an opaque material (usually plastic) and protects the LCD module  15 . The LCD module  15  is secured within the LCD housing  10  by various common securing means, such as screws, clips, or other frictionally engaging or interlocking means (not shown). Referring again to  FIG. 2 , the LCD housing  10  has a rear portion  12  and top and bottom portions  11 . 
     Referring again to  FIG. 2 , the LCD module  15  includes an LCD  20 , a light source  25 , and a light pipe  30 . The aperture  26  of the light source  25  is aligned adjacent to an end of the light pipe  30 . As shown in  FIG. 2 , the light pipe  30  is adjacent to the back surface  21  of the LCD  20 . The LCD  20  is backlit when light generated by the light source  25  is conducted through the light source aperture  26  and coupled into an end of the light pipe  30 . As shown in U.S. Pat. No. 5,050,946, the coupled light may be uniformly diffused throughout the light pipe  30 , and projected toward the back surface  21  of the LCD  20 . Some conventional LCD modules utilize a light pipe  30  with a light-reflective coating applied to the back side  31  of the light pipe  30  (not shown). In this manner, light incident upon the back surface  31  of the light pipe  30  will be reflected back into the light pipe  30  for projection toward the LCD  20 . 
     As shown in  FIG. 2 , the length of the top and bottom portions  11  of the LCD housing  10 , and hence the depth D of the fliptop display  2 , are roughly defined by the combined thickness of the rear portion  12  of the LCD housing  10  and the LCD module  15 . 
     As shown in  FIG. 3 , the depth D of the fliptop display  2  is at least the sum of the thickness d 1  of the rear portion  12  of the LCD housing  10 , the diameter d 3  of the light source  25 , and some fractional portion of the thickness d 5  of the LCD  20 . In situations where the diameter d 3  of the light source  25  is equal to the thickness d 4  of the light pipe  30 , the depth D may be the sum of the thicknesses d 1 , d 3  (or d 4 ), and d 5 . 
     For example, thickness d 1  of the rear portion  12  of the LCD housing  10  may be 4 mm, the diameter d 3  of the light source  25  may be 4 mm and the thicknesses d 4  and d 5  of the light pipe  30  and the LCD  20  may be 2 mm. As shown in  FIG. 3 , these dimensions will result in the light source  25  extending 1 mm on either side of the light pipe  30 . It can be seen that for this configuration of components, the depth D of the fliptop display  2  will be at least 9 mm and the thickness d 2  of the LCD module  15  will be 5 mm. In situations where the diameter d 3  of the light source  25  is equal to the thickness d 4  of the light pipe  30 , the depth D of the fliptop display  2  will be 8 mm and the thickness d 2  of the LCD module  15  will be 4 mm. 
     In the laptop computer industry, it is always desirable to reduce the size and weight of the laptop computer and its component parts. It is also desirable to minimize the number of parts. Thus, there exists a need for a thinner, less complex, and lighter fliptop display. 
     SUMMARY OF THE INVENTION 
     One embodiment of the present invention is a computer display. The computer display includes a LCD housing, a light source coupled to the LCD housing, and a LCD coupled to the LCD housing. In this embodiment, the LCD housing conducts light from the light source to the LCD. 
     Another embodiment of the invention is a method for conducting light. The method includes generating light and conducting the generated light through a LCD housing. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  illustrates a perspective view of a laptop computer. 
         FIG. 2  is a cross sectional view of a prior art fliptop display for a laptop computer. 
         FIG. 3  is a close up view of the lower portion of  FIG. 2 . 
         FIG. 4  is a cross sectional view of a novel fliptop display of a laptop computer. 
         FIG. 5  is a close up view of the lower portion of  FIG. 4 . 
         FIG. 6  is a close up view of an alternative embodiment of the lower portion of  FIG. 4 . 
         FIG. 7  is a cross sectional view of an alternative embodiment of the present invention. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       FIG. 4  illustrates a cross sectional view of a novel fliptop display  5 . The fliptop display  5  includes a planar LCD module  70  and a generally planar LCD housing  50 . The LCD module  70 , which includes a planar LCD  71 , is secured in the LCD housing  50  by various common securing means, such as screws, clips, or other frictionally engaging or interlocking means (not shown). 
     The LCD housing  50  is composed of a translucent material that functions as a light pipe. For example, the LCD housing  50  may be formed from an ABS plastic such as Lexan™ from General Electric. The LCD housing  50  may include a planar rear portion  54  and top and bottom portions  55 . As shown in  FIG. 4 , a light source  60  may be partially embedded in or enclosed in the LCD housing  50 . The light source  60  may be secured in the LCD housing  50  by friction fit or by various common securing means, such as screws, clips, or other frictionally engaging or interlocking means (not shown). The LCD housing  50  may also have a light-reflective coating  53  applied to its outer surface  58 . The light-reflective coating  53 , may be composed of aluminum or a variety of metallic or other reflective substances. The light-reflective coating  53  reflects light incident upon it back into the LCD housing  50  for projection to the LCD module  70 . The reflective coating  53 , when made of materials such as electroless chrome followed by 40 to 50 (inches) of copper, then nickel plating of 10 (inches) may also operate to minimize EMI emissions from the fliptop display  5 . Alternatively, a nickel-copper-nickel plating may be utilized. Because the reflective coating  53  forms the outer surface  58  of the housing  50 , it may be desirable to cover it or paint it with a protective layer  56  composed of a material such as soft touch polyethylene paint, that resists scratching and preserves its desired optical qualities. 
     During operation of the fliptop display  5 , the light source  60  generates light. This light is conducted through the LCD housing  50 . The conducted light is then projected into the back surface  72  of the LCD module  70 . 
       FIG. 5  shows a close-up view of the lower portion of  FIG. 4 . In  FIG. 5 , the rear portion  54  of the LCD housing  50  has a thickness d 6 . The fractional portion of the LCD housing  50  between its outer surface  58  and the light source  60  has a thickness d 7 . (The light-reflective coat  53  and its protective layer  56  add a negligible thickness). The light source  60  depicted in  FIG. 5  is a cold cathode fluorescent lamp that has a diameter d 3 . For maximum light coupling, the cold cathode fluorescent lamp  60  may be embedded in the LCD housing  50  so that the aperture  61  of the cold cathode fluorescent lamp  60  is completely adjacent to the LCD housing  50 . The LCD module  70 , which has a thickness d 8 , may be adjacent to the inner surface  52  of the LCD housing  50 . Thus, it can be seen from  FIG. 5 , that the depth D of the fliptop display  5 , closely approximates the sum of the thickness d 7  of the fractional portion of the LCD housing  50  between its outer surface  58  and the light source  60 , the diameter d 3  of the light source, and some fraction of the thickness d 8  of the LCD module  70 . It can also be seen that the depth D of the fliptop display  5  closely approximates the sum of the thickness d 6  of the rear portion  54  of the LCD housing  50  and the thickness d 8  of the LCD  71 . 
     For example, using the dimensions previously discussed for these components, the thickness d 8  of the LCD  71  is 2 mm and the thickness d 6  of the LCD housing  50  is 4 mm. To provide maximum light coupling, the light source  60  with a 2 mm aperture  61  will be embedded in the LCD housing  50  so that 1 mm of diameter protrudes from the assembly. Accordingly, the thickness d 7  will be 1 mm, and the fraction of the thickness d 8  contributing to the depth D of the fliptop display  5  will be 1 mm. Thus, it can be seen that the depth D of the fliptop display  5  is now 6 mm. This depth D is 25% less than the depth of conventional fliptop displays. 
     Another embodiment of the present invention is shown in  FIG. 6 . This embodiment, includes an omnidirectional light source  62 . A reflector  63  is used to direct incident light generated by the omnidirectional light source  62  back into the LCD housing  50 . As shown by the path traveled by light ray A, the light-reflective coating  53  will internally reflect light conducted into the bottom portion  55  of the LCD housing  50  until the light is eventually directed toward the rear surface  72  of the LCD module  70 . Since all internal reflections will inherently have a lossy effect on the incident light, the junction of the rear portion  54  and the bottom portion  55  of the LCD housing  50  may be geometrically shaped so that light is reflected into the rear portion  54  with a minimum amount of internal reflections. In this embodiment, the light source  62  need not be enclosed in the LCD housing  50  to the extent of the cold cathode fluorescent lamp  60  of  FIG. 5 . In situations where a greater thickness d 7  is required to protect the light source  62 , the light source  62  may be enclosed in the LCD housing  50  at a variety of depths. 
     Still another embodiment of the present invention is shown in  FIG. 7 . In this embodiment, the light source  62  and the reflector  63  may be located in the middle of the rear portion  54  of the LCD housing  50 . The light source  62  may be partially enclosed in the LCD housing  50 . The protrusion of the light source  62  (and the reflector  63 ) from the LCD housing  50  creates a gap  66  between the rear surface  72  of the LCD module  70  and the inner surface  52  of the LCD housing  50 . This results in a larger gap  66  than required solely to accommodate the protrusion of the light source  62  from the LCD housing  50 . 
     The gap  66  may be purposely designed into the fliptop display  5  as a design tradeoff between depth D and lighting efficiency. While the depth D of the fliptop display  5  will be increased, lighting efficiency may be improved. The addition of the gap  66  will provide the light with a greater depth d in which to diffuse before being incident upon the rear surface  72  of the LCD  71 . This may provide better illumination of the LCD  71  toward the top and bottom portions  55  of the LCD housing  50 . 
     Yet another embodiment is shown in  FIG. 8 . In this embodiment, the thickness d 6  of the rear portion  54  of the LCD housing  50  in  FIG. 7  may be increased in order to strengthen the LCD housing  50 . For example, using the typical dimensions previously discussed for the various fliptop display components, the thickness d 6  may be increased up to 2 mm before the fliptop display  5  has the same depth D as in the prior art. As shown in  FIG. 8 , the depth d of the gap  66  is correspondingly reduced. 
     In yet another embodiment, the LCD housing  50  can be designed to display a variety of ornamental effects. In this embodiment, areas of the light-reflective coating  53  can be masked or removed by scoring or by etching so that light incident upon these areas is no longer reflected back into the LCD housing  50 , but instead is conducted out of the LCD housing  50 . The protective layer  56  would also typically be similarly scored or etched in order to allow the light to leave the LCD housing  50 . In this manner, text, company logos, trademarks, or other designs may be illuminated. 
     With respect to the embodiments described herein, it can be seen that the present invention&#39;s incorporation of the light pipe function into the LCD housing provides the laptop computer designer with greater design flexibility. The potential reduction in depth D of the fliptop display provides the laptop computer designer with a variety of configurations for the light source, LCD, and LCD housing assembly. The laptop computer designer may configure these components in a variety of ways resulting in a fliptop display depth D that is less than or equal to the width of the prior art fliptop display assembly. Additionally, the size and/or weight of the LCD module may substantially reduced. While this design flexibility has been demonstrated in the description of the preferred embodiments, it is clear that many other modifications, changes, variations, and substitutions are within the scope of this invention.

Technology Classification (CPC): 6