Optical beam scanning apparatus and image forming apparatus

Abstract

An image forming apparatus provided with an optical beam scanning apparatus according to the invention includes a semiconductor laser device, a pre-deflection optical system, a polygon mirror, and a post-deflection optical system, wherein at least one imaging lens for imaging the luminous flux is provided in the post-deflection optical system includes; at least one projection on a vertical surface to a sub-scanning direction axis is provided in the imaging lens; and at least one positioning member having an engaging groove into which the projection is interfitted and which is engaged in a concave-convex shape is provided in the housing unit of the optical beam scanning apparatus. In accordance with an image forming apparatus according to the invention, in a scanning optical system using an imaging lens or an imaging mirror, influences against optical characteristics following an environmental fluctuation or a change with time can be reduced.

1 . An optical beam scanning apparatus comprising:
 a light source configured to emit one or plural luminous fluxes,   a pre-deflection optical system configured to form a luminous flux emitted from the light source to image the luminous flux as a line image in a direction corresponding to a main scanning direction,   a scanning unit configured to scan the imaged luminous flux by the pre-deflection optical system against a scanning subject, having at least one reflecting surface in which a width of the luminous flux made incident on the scanning unit from the pre-deflection optical system is wider than a width of one reflecting surface forming the scanning unit, and   a post-deflection optical system configured to image the luminous flux scanned by the scanning unit on the scanning subject, in which at least one optical parts configured to image the luminous flux scanned from the scanning unit on the scanning subject is provided, the optical parts having at least one projection provided on a vertical surface to a sub-scanning direction formed in an effective region in the optical parts, through which the luminous flux passes, the projection being protruded in the sub-scanning direction.   
   
   
       2 . The optical beam scanning apparatus according to  claim 1 , wherein at least one positioning member which supports the projection is provided while being made opposing to the projection in a housing unit of the optical beam scanning apparatus. 
   
   
       3 . The optical beam scanning apparatus according to  claim 2 , wherein the projection is provided in a plural number; the positioning member is provided in a plural number; and the respective projections are interfitted into the engaging groove to be a pair with the projection which the positioning member has and then engaged in a concave-convex shape with the housing unit in the main scanning direction. 
   
   
       4 . The optical beam scanning apparatus according to  claim 2 , wherein the optical parts are brought into contact with the sub-scanning direction by the positioning member in the concave-convex engagement between the projection and the engaging groove to be a pair with the projection which the positioning member has. 
   
   
       5 . The optical beam scanning apparatus according to  claim 2 , wherein the optical parts are brought into contact with the sub-scanning direction by the positioning member via a space in the vicinity of the projection in the concave-convex engagement between the projection and the engaging groove to be a pair with the projection which the positioning member has. 
   
   
       6 . The optical beam scanning apparatus according to  claim 2 , wherein a supporting member for supporting the optical parts in the optical axis direction after the both ends thereof are placed is further provided in the housing unit. 
   
   
       7 . The optical beam scanning apparatus according to  claim 1 , wherein the both ends of the optical parts are excluded from the effective region through which the luminous flux passes in the optical parts. 
   
   
       8 . The optical beam scanning apparatus according to  claim 1 , wherein the optical parts are a lens or a mirror. 
   
   
       9 . The optical beam scanning apparatus according to  claim 1 , wherein the optical parts are configured of a single lens. 
   
   
       10 . An image forming apparatus provided with an optical beam scanning apparatus comprising:
 a light source configured to emit one or plural luminous fluxes,   a pre-deflection optical system configured to form a luminous flux emitted from the light source to image the luminous flux as a line image in a direction corresponding to a main scanning direction,   a scanning unit configured to scan the imaged luminous flux by the pre-deflection optical system against a scanning subject, having at least one reflecting surface in which a width of the luminous flux made incident on the scanning unit from the pre-deflection optical system is wider than a width of one reflecting surface forming the scanning unit, and   a post-deflection optical system configured to image the luminous flux scanned by the scanning unit on the scanning subject, in which at least one optical parts configured to image the luminous flux scanned from the scanning unit on the scanning subject is provided, the optical parts having at least one projection provided on a vertical surface to a sub-scanning direction formed in an effective region in the optical parts, through which the luminous flux passes, the projection being protruded in the sub-scanning direction.   
   
   
       11 . The image forming apparatus according to  claim 10 , wherein at least one positioning member which supports the projection is provided while being made opposing to the projection in a housing unit of the optical beam scanning apparatus. 
   
   
       12 . The image forming apparatus according to  claim 11 , wherein the projection is provided in a plural number; the positioning member is provided in a plural number; and the respective projections are interfitted into the engaging groove to be a pair with the projection which the positioning member has and then engaged in a concave-convex shape with the housing unit in the main scanning direction. 
   
   
       13 . The image forming apparatus according to  claim 11 , wherein the optical parts are brought into contact with the sub-scanning direction by the positioning member in the concave-convex engagement between the projection and the engaging groove to be a pair with the projection which the positioning member has. 
   
   
       14 . The image forming apparatus according to  claim 11 , wherein the optical parts are brought into contact with the sub-scanning direction by the positioning member via a space in the vicinity of the projection in the concave-convex engagement between the projection and the engaging groove to be a pair with the projection which the positioning member has. 
   
   
       15 . The image forming apparatus according to  claim 11 , wherein a supporting member for supporting the optical parts in the optical axis direction after the both ends thereof are placed is further provided in the housing unit. 
   
   
       16 . The image forming apparatus according to  claim 10 , wherein the both ends of the optical parts are excluded from the effective region through which the luminous flux passes in the optical parts. 
   
   
       17 . The image forming apparatus according to  claim 10 , wherein the optical parts are a lens or a mirror. 
   
   
       18 . The image forming apparatus according to  claim 10 , wherein the optical parts are configured of a single lens.