Back light module having concave-down luminance distribution

Abstract

Several optical mechanism designs for making luminance of the outer portion of a back light module to become higher than luminance of the inner portion of the back light module of the direct lighting type are disclosed in accordance with the present invention. The disclosed optical mechanism designs can be cooperated with each other to enhance the optical effect of the back light module. Additionally, the back light modules of the present invention are feasible for utilization in various scanners or liquid crystal displays.

1 . A back light module of direct lighting type comprising: 
 a light emitting device for emitting light, wherein an outer portion of the light emitting device with respect to an axis having higher luminous intensity than an inner portion of the light emitting device;    a diffuser positioned on a side of the light emitting device for diffusing light; and    a reflecting device positioned on another side of the light emitting device for reflecting light emitted from the light emitting device to the diffuser.    
     
     
         2 . The back light module of direct lighting type of  claim 1 , wherein the light emitting device is a lamp having a bended shape.  
     
     
         3 . The back light module of direct lighting type of  claim 2 , wherein the lamp is a cold cathode fluorescent lamp (CCFL).  
     
     
         4 . The back light module of direct lighting type of  claim 2 , wherein the lamp is a U-shape lamp.  
     
     
         5 . The back light module of direct lighting type of  claim 1 , wherein the light emitting device comprises a plurality of electro luminances (ELs) or a plurality of light emitted diodes (LEDs).  
     
     
         6 . The back light module of direct lighting type of  claim 1 , wherein the light emitting device comprises a straight cold cathode fluorescent lamp (CCFL) and a plurality of electro luminances (ELs) or comprises a straight CCFL and a plurality of light emitted diodes (LEDs).  
     
     
         7 . The back light module of direct lighting type of  claim 1 , wherein the outer portion of the reflecting device has higher reflectivity or larger reflecting area than the inner portion of the reflecting device.  
     
     
         8 . The back light module of direct lighting type of  claim 7 , wherein the reflecting device comprises: 
 a housing; and    a reflector positioned between the light emitting device and the housing for reflecting light emitted from the light emitting device to the diffuser;    wherein the outer portion of the reflector has higher reflectivity or larger reflecting area than the inner portion of the reflector.    
     
     
         9 . The back light module of direct lighting type of  claim 7 , wherein the reflecting device comprises: 
 a housing; and    two reflectors positioned between the light emitting device and the housing with each corresponding to one of two ends of the light emitting device, the two reflectors for reflecting light emitted from the two ends of the light emitting device to the diffuser.    
     
     
         10 . The back light module of direct lighting type of  claim 7 , wherein the reflecting device is a reflecting housing in which the outer portion has higher reflectivity or larger reflecting area than the inner portion.  
     
     
         11 . The back light module of direct lighting type of  claim 1 , wherein the outer portion of the diffuser has higher light transmittance than the inner portion of the diffuser.  
     
     
         12 . A back light module of direct lighting type comprising: 
 a light emitting device for emitting light;    a diffuser positioned on a side of the light emitting device for diffusing light; and    a reflecting device positioned on another side of the light emitting device for reflecting light emitted from the light emitting device to the diffuser;    wherein the outer portion of the reflecting device has higher reflectivity or larger reflecting area than the inner portion of the reflecting device.    
     
     
         13 . The back light module of direct lighting type of  claim 12 , wherein the reflecting device comprises: 
 a housing; and    a reflector positioned between the light emitting device and the housing for reflecting light emitted from the light emitting device to the diffuser;    wherein the outer portion of the reflector has higher reflectivity or larger reflecting area than the inner portion of the reflector.    
     
     
         14 . The back light module of direct lighting type of  claim 12 , wherein the reflecting device comprises: 
 a housing; and    two reflectors positioned between the light emitting device and the housing with each corresponding to one of two ends of the light emitting device, the two reflectors for reflecting light emitted from the two ends of the light emitting device to the diffuser.    
     
     
         15 . The back light module of direct lighting type of  claim 12 , wherein the reflecting device is a reflecting housing in which the outer portion has higher reflectivity or larger reflecting area than the inner portion.  
     
     
         16 . The back light module of direct lighting type of  claim 12 , wherein the outer portion of the diffuser has higher light transmittance than the inner portion of the diffuser.  
     
     
         17 . A back light module of direct lighting type comprising: 
 a light emitting device for emitting light;    a diffuser positioned on a side of the light emitting device for diffusing light, wherein the outer portion of the diffuser has higher light transmittance than the inner portion of the diffuser; and    a reflecting device positioned on another side of the light emitting device for reflecting light emitted from the light emitting device to the diffuser.