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.

1. A multi-beam optical scanner comprising:
 a light source for a multi-beam;    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 in a direction corresponding to auxiliary scanning and forming them to images as a plurality of line images each long 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;    a second image-formation system for separating the plurality of light fluxes 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 as a plurality of light spots for optically scanning said scanned surface in accordance with deflection of the light fluxes; 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 said scanned surface is as follows: 
   2<β 
   
       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 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 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 has two LD light emitting sections, and said LD light emitting sections are provided symmetric with respect to an optical axis of a coupling lines. 
     
     
       5. A multi-beam optical scanner according to  claim 1 ; wherein said coupling lens is a collimate lens for collimating a plurality of light fluxes 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 βin 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 comprising:      a light source for a multi - beam;        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 in a direction corresponding to auxiliary scanning and forming them to images as a plurality of line images each long 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 plurality of line images formed on the deflecting reflection surface of the optical deflector;        a second image - formation system for separating the plurality of light fluxes 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 as a plurality of light spots for optically scanning said scanned surface in accordance with deflection of the light fluxes; 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 said scanned surface is as follows:          2 <β       
       
         the plurality of light spots on the scanned surface optically scan scanning lines adjacent to each other, and the deflecting reflection surface is conjugate with the scanned surface, wherein said adjacent scanning lines do not have any subsequent scanning lines therebetween.  
       
     
     
       10. A multi-beam optical scanner comprising:
   a light source for a multi-beam;        a coupling lens for coupling a plurality of light fluxes from said light source for a multi-beam to an image-forming optical system, said coupling lens being a positive convex lens having a planar surface;        a first image-formation system for focusing a plurality of light fluxes coupled by said coupling lens in a direction corresponding to auxiliary scanning and forming them to images as a plurality of line images each long 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;        a second image-formation system for separating the plurality of light fluxes 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 as a plurality of light spots for optically scanning said scanned surface in accordance with deflection of the light fluxes; 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 said scanned surface is as follows:          2 <β       
       
         and the plurality of light spots on the scanned surface optically scan scanning lines adjacent to each other. 
        
       
     
     
       11. A multi-beam optical scanner comprising:
   a light source for a multi-beam;        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 in a direction corresponding to auxiliary scanning and forming them to images as a plurality of line images each long 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;        a second image-formation system for separating the plurality of light fluxes 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 as a plurality of light spots for optically scanning said scanned surface in accordance with deflection of the light fluxes, said second image-formation system including a lengthy lens, the lengthy lens being a toroidal lens; 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 said scanned surface is as follows:          2 <β       
       
         and the plurality of light spots on the scanned surface optically scan scanning lines adjacent to each other, wherein said adjacent scanning lines do not have any subsequent scanning lines therebetween. 
        
       
     
     
       12. A multi-beam optical scanner according to  claim 11 , wherein said toroidal lens is provided in an optical path extending in a main scanning direction from a constant-velocity optical-scanning image-forming mirror toward a scanned surface.  
     
     
       13. A multi-beam optical scanner comprising:
   a light source for a multi-beam;        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 in a direction corresponding to auxiliary scanning and forming them to images as a plurality of line images each long 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;        a second image-formation system for separating the plurality of light fluxes 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 as a plurality of light spots for optically scanning said scanned surface in accordance with deflection of the light fluxes, said second image-formation system including a lengthy lens, the lengthy lens being a toroidal lens; 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 said scanned surface is as follows:          2 <β       
       
         and the plurality of light spots on the scanned surface optically scan scanning lines adjacent to each other, wherein said toroidal lens is provided in an optical path extending in a main scanning direction from a constant-velocity optical-scanning image-forming mirror toward a scanned surface.