Multi-beam optical scanner

Abstract

A multi-beam optical scanner, in which a lateral magnification β in a composite system of an optical system between the light source for a multi-beam and the scanned surface satisfies the condition: 2<β≦8.5, and a plurality of light spots on the scanned surface execute optical scanning of the scanning lines adjacent to each other.

What is claimed is:  
     
       1. A multi-beam optical scanner comprising: 
       a light source for a multi-beam  providing plural light beams;  
       a coupling lens for coupling a plurality of light fluxes from said light source for a multi-beam to an image-forming optical system; 
       a first image-formation system for focusing a plurality of light fluxes coupled by said coupling lens  the plural light beams from the light source in a direction corresponding to auxiliary scanning and forming them to  the plural light beams into images as a plurality of line images each long  having a longer side in a direction corresponding to main scanning;  
       an optical deflector having a deflecting reflection surface adjacent to positions where images as  said plurality of line images are formed for deflecting said plurality of light fluxes  the plural light beams;  
       a second image-formation system for separating the plurality of light fluxes  plural light beams deflected by said optical deflector from each other in a direction of auxiliary scanning on a scanned surface and converging the plurality of light fluxes  plural light beams as a plurality of light spots for optically scanning said scanned surface in accordance with deflection of the plural light fluxes  beams; wherein  
       
         the plurality of light spots on the scanned surface optically scan scanning lines adjacent to each other on plural consecutive scans, and  
       
       a lateral magnification β in a direction corresponding to the auxiliary scanning in a composite system  of the optical system  scanner between said light source for a multi-beam  and said scanned surface is as follows:  
       
         
           2<β< 8 . 5   
         
       
       and the plurality of light spots on the scanned surface optically scan scanning lines adjacent to each other . 
     
     
       2. A multi-beam optical scanner according to  claim 1 ;, wherein said light source for a multi-beam  comprises at least two or more  LD light emitting sections or LED light emitting sections  monolithically provided therein. 
     
     
       3. A multi-beam optical scanner according to  claim 1 ;, wherein said light source for a multi-beam  comprises two or more  at least a pair of LD light emitting sections or LED light emitting sections  in hybrid  combination thereof . 
     
     
       4. A multi-beam optical scanner according to  claim 1 ;, wherein said light source for a multi-beam hascomprises two LD light emitting sections, andwherein said LD light emitting sections are provided symmetric with respect to an optical axis of a coupling lens. 
     
     
       5. A multi-beam optical scanner according to  claim 1 ; wherein said, further comprising a coupling lens is a collimate lens  for collimating a plurality of  coupling at least one light fluxes  beam of the plural light beams from said light source for a multi-beam at the same time . 
     
     
       6. A multi-beam optical scanner according to  claim 1 ;, wherein said second image-formation system includes a lengthy lens provided in a side of the scanned surface. 
     
     
       7. A multi-beam optical scanner according to  claim 1 ;, wherein said first image-formation system comprises a piece of  lens having power only in the auxiliary scanning direction, while said second image-formation system comprises a constant-velocity optical-scanning image-forming mirror and a lengthy lens each provided on the side of the scanned surface. 
     
     
       8. A multi-beam optical scanner according to  claim 1 ; wherein a lateral magnification β in a direction corresponding to the auxiliary scanning in a composite system of the optical system between said light source for a multi-beam and the scanned surface is as follows: 
       
         
           2<β≦8.5.  
         
       
     
     
       9. A multi- beam optical scanner according to    claim 5   , wherein said coupling lens is a collimate lens for collimating the plural light beams from said light source at the same time.   
     
     
       10. A multi- beam optical scanner according to    claim 1   , wherein said light source comprises at least two LED light emitting sections monolithically provided therein.   
     
     
       11. A multi- beam optical scanner according to    claim 1   , wherein said light source comprises at least a pair of LED light emitting sections in combination.   
     
     
       12. A multi- beam optical scanner comprising:    
       
         plural light beams;  
       
         a first image - formation system for focusing the plural light beams in a direction corresponding to auxiliary scanning and forming the plural light beams into images as a plurality of line images each having a longer side in a direction corresponding to main scanning;    
       
         an optical deflector having a deflecting reflection surface adjacent to positions where said plurality of line images are formed for deflecting the plural light beams;  
       
         a second image - formation system for separating the plural light beams deflected by said optical deflector from each other in a direction of auxiliary scanning on a scanned surface and converging the plural light beams as a plurality of light spots for optically scanning said scanned surface in accordance with deflection of the plural light beams; wherein    
       
         the plurality of light spots on the scanned surface optically scan scanning lines adjacent to each other on plural consecutive scans, and  
       
       
         a lateral magnification β in a direction corresponding to the auxiliary scanning of the optical scanner is as follows:  
       
       
         
           
               2 <β< 8 . 5 . 
           
         
       
     
     
       13. An image forming apparatus comprising: 
         a multi - beam optical scanner including:    
       
         a light source for providing plural light beams;  
       
         a first image - formation system for focusing the plural light beams from the light source in a direction corresponding to auxiliary scanning and forming the plural light beams into images as a plurality of line images each having a longer side in a direction corresponding to main scanning;    
       
         an optical deflector having a deflecting reflection surface adjacent to positions where said plurality of line images are formed for deflecting the plural light beams;  
       
         a second image - formation system for separating the plural light beams deflected by said optical deflector from each other in a direction of auxiliary scanning on a scanned surface and converging the plural light beams as a plurality of light spots for optically scanning said scanned surface in accordance with deflection of the plural light beams; wherein    
       
         the plurality of light spots on the scanned surface optically scan scanning lines adjacent to each other on plural consecutive scans, and  
       
       
         a lateral magnification β in a direction corresponding to the auxiliary scanning of the optical scanner is as follows:  
       
       
         
           
               2 <β< 8 . 5 . 
           
         
       
     
     
       14. An image forming apparatus comprising: 
         a multi - beam optical scanner including:    
       
         plural light beams;  
       
         a first image - formation system for focusing the plural light beams in a direction corresponding to auxiliary scanning and forming the plural light beams into images as a plurality of line images each having a longer side in a direction corresponding to main scanning;    
       
         an optical deflector having a deflecting reflection surface adjacent to positions where said plurality of line images are formed for deflecting the plural light beams;  
       
         a second image - formation system for separating the plural light beams deflected by said optical deflector from each other in a direction of auxiliary scanning on a scanned surface and converging the plural light beams as a plurality of light spots for optically scanning said scanned surface in accordance with deflection of the plural light beams; wherein    
       
         the plurality of light spots on the scanned surface optically scan scanning lines adjacent to each other on plural consecutive scans, and  
       
       
         a lateral magnification β in a direction corresponding to the auxiliary scanning of the optical scanner is as follows:  
       
       
         
           
               2 <β< 8 . 5 .