Optical beam scanning device and image forming apparatus

Abstract

An optical beam scanning device of the present invention is for having a light beam with the width in the main scanning direction wider than the width in the main scanning direction of the reflection surface of a deflector incident on the deflector, reflecting and polarizing a part thereof by the reflection surface of the deflector, and focusing the polarized light beam on a surface to be scanned by optical means including a transmission type optical member. Then, the polarization direction of the light beam incident on the deflector is substantially in the main scanning direction. According to an image forming apparatus comprising a plurality of light sources for forming a plurality of scanning lines with the light beams from a plurality of the light sources, the polarization direction of the light beams from the light sources at the time of being incident on the corresponding deflector is provided substantially in the main scanning direction.

1 . An optical beam scanning device comprising: 
 an optical element for converting an output light beam from a light source to a parallel light beam or a light flux close to the parallel light beam;    a cylindrical lens with a plane provided on an incident side, for focusing the output light beam from said optical element in vicinity of a deflector in a sub scanning direction; and    a half wave plate, or a birefringence substance to provide a function of the half wave plate, provided in the plane of said cylindrical lens.    
   
   
       2 . The optical beam scanning device according to  claim 1 , 
 wherein a light beam having a width in a main scanning direction wider than the width in the main scanning direction of a reflection surface of said deflector is incident on said deflector.    
   
   
       3 . The optical beam scanning device according to  claim 1 , 
 wherein a plurality of light sources are provided as the light source for outputting a light beam to said deflector; and    the half wave plate or the birefringence substance to provide the function of the half wave plate is provided on a flat surface of a part of the cylindrical lens corresponding to at least a part of said light sources.    
   
   
       4 . An image forming apparatus comprising a plurality of optical beam scanning devices for forming a scanning line, utilizing a deflector, or an optical beam scanning device with the deflector utilized commonly by a plurality of scanning light beams, for forming a plurality of scanning lines by light beams from a plurality of light sources, 
 wherein a light beam having a width wider in a main scanning direction than the width of a reflection surface of said deflector in the main scanning direction is incident on said deflector, and    the polarization direction of output light beams from said respective light sources at a time of being incident on said corresponding deflector is substantially in the main scanning direction.    
   
   
       5 . An optical beam scanning device comprising: 
 an optical element for converting an output light beam from a light source to a parallel light beam or a light flux close to the parallel light beam;    a cylindrical lens with a plane provided on an incident side, for focusing the output light beam from said optical element in vicinity of a deflector in a sub scanning direction; and    a wave plate, or a birefringence substance to provide a function of the wave plate, provided in the plane of said cylindrical lens,    wherein said cylindrical lens is provided rotatably around an optical axis of light beam passage as a center of rotation.    
   
   
       6 . An optical beam scanning device comprising: 
 an optical element for converting an output light beam from a light source to a parallel light beam or a light flux close to the parallel light beam;    a cylindrical lens with a plane provided on an incident side, for focusing the output light beam from said optical element in the vicinity of a deflector in a sub scanning direction; and    a polarizer provided in the plane of said cylindrical lens,    wherein said cylindrical lens is provided rotatably around an optical axis of light beam passage as a center of rotation.    
   
   
       7 . An optical beam scanning device comprising a deflector utilized commonly by a plurality of scanning light beams from a plurality of light sources, 
 wherein a common optical element for having the light beams from the plurality of the light sources passing through before reaching to said deflector, is provided with a wave plate or a birefringence substance to provide a function as the wave plate integrally.    
   
   
       8 . An optical beam scanning device comprising a deflector utilized commonly by a plurality of scanning light beams from a plurality of light sources, 
 wherein a common optical element for having the light beams from said plurality of the light sources passing through before reaching to said deflector, is provided with a polarizer integrally.