Method and apparatus for multi-beam optical scanning capable of effectively adjusting a scanning line pitch

Abstract

An optical scanning apparatus includes light sources, an aperture having, and coupling lenses. Numbers of the light sources and the coupling lenses are equal to each other and the apparatus satisfies an inequality 12.7<(D×β 0 ×m 0 ×dpi)/(2×NA)<38.1 and an equation β 0 =(β + −β − )/(n−1), wherein D represents a width of the slit of the aperture, β 0 represents a beam open angle, mo represents a total lateral magnification ratio, dpi represents a number of dots per inch, NA represents a numerical aperture, β + represents a positive open angle, β − represents a negative open angle, and n represents the number. Further, an image forming apparatus using this optical scanning apparatus and an image forming method are provided.

1 - 7 . (canceled)  
   
   
       8 . An optical scanning apparatus, comprising: 
 a plurality of optical device sets each configured to generate multiple laser light beams; and    a light deflection mechanism configured to deflect the multiple laser light beams from the plurality of optical device sets to form different latent images on respective photosensitive surfaces,    wherein each set of the plurality of optical device sets includes a prism which is arranged between a coupling lens included in each optical device set and said light deflecting mechanism, said prism being configured to move in a direction to change positions of the multiple laser light beams in a particular direction.    
   
   
       9 . An optical scanning apparatus as defined in  claim 8 , wherein said particular direction is a sub-scanning direction.  
   
   
       10 . An optical scanning apparatus as defined in  claim 8 , wherein said particular direction is a direction to rotate around a light axis of the coupling lens.  
   
   
       11 . An optical scanning apparatus as defined in  claim 8 , wherein said particular direction is a direction to tilt about an axis orthogonal to a light axis of the coupling lens.  
   
   
       12 . An image forming apparatus comprising: 
 a plurality of photosensitive members each having a photosensitive surface;    a plurality of development mechanisms each configured to develop an image with a different color toner; and    an optical scanning apparatus which comprises: 
 a plurality of optical device sets each configured to generate multiple laser light beams; and  
 a light deflection mechanism configured to deflect the multiple laser light beams from the plurality of optical device sets to form different latent images on respective photosensitive surfaces of the plurality of photosensitive members;  
   wherein each set of the plurality of optical device sets includes a prism which is arranged between a coupling lens included in said each set and said light deflecting mechanism, said prism being configured to move in a direction to change positions of the multiple laser light beams in a sub-scanning direction, and    wherein the different latent images formed on the respective photosensitive surface of the plurality of photosensitive member are developed into visual images with different respective color toners by the plurality of development mechanisms.    
   
   
       13 . An optical scanning method, comprising: 
 providing a plurality of optical device sets each generating multiple laser light beams; and    deflecting the multiple laser light beams from the plurality of optical device sets to form different latent images on respective photosensitive surfaces with a light deflecting mechanism,    wherein each set of the plurality of optical device sets includes a prism arranged between a coupling lens included in each optical device set and said light deflecting mechanism and moving each said prism in a direction to change positions of the multiple laser light beams in a particular direction.    
   
   
       14 . An optical scanning apparatus as defined in  claim 13 , wherein said particular direction is a sub-scanning direction.  
   
   
       15 . An optical scanning apparatus as defined in  claim 13 , wherein said particular direction is a direction to rotate around a light axis of the coupling lens.  
   
   
       16 . An optical scanning apparatus as defined in  claim 13 , wherein said particular direction is a direction to tilt about an axis orthogonal to a light axis of the coupling lens.