Scanner having a light beam incident position adjusting device

Abstract

A scanner includes a light-beam emitter for emitting a light beam; a light-beam deflector for deflecting the light beam to scan a scanning surface; a photo-detector provided at a position outside an image-forming scanning range of the scanning surface to detect a scanning light beam before the scanning light beam starts generating a scanning line in the image-forming scanning range; a rotatable member, located in front of an incident surface of the photo-detector, that is rotatable about a rotational axis perpendicular to a plane defined by the scanning light beam by the deflector; an optical member, provided on the rotatable member, that allows the scanning light beam to pass therethrough to be incident upon the incident surface of the photo-detector; and a device for adjusting rotational position of the rotatable member about the rotational axis.

What is claimed is:  
     
         1 . A scanner comprising: 
 a light-beam emitter for emitting a light beam;    a light-beam deflector for deflecting said light beam to scan a scanning surface;    a photo-detector provided at a position outside an image-forming scanning range of said scanning surface to detect a scanning light beam before said scanning light beam starts generating a scanning line in said image-forming scanning range;    a rotatable member located in front of an incident surface of said photo-detector, said rotatable member being rotatable about a rotational axis perpendicular to a plane defined by said scanning light beam by said deflector;    an optical member that is provided on said rotatable member, said optical member allowing said scanning light beam to pass therethrough to be incident upon said incident surface of said photo-detector; and    a device for adjusting rotational position of said rotatable member about said rotational axis.    
     
     
         2 . The scanner according to  claim 1 , wherein said light-beam deflector comprises a polygon mirror.  
     
     
         3 . The scanner according to  claim 1 , wherein a signal, output from said photo-detector, is used for detecting the timing for commencement of writing said scanning line with respect to said scanning surface.  
     
     
         4 . The scanner according to  claim 1 , wherein said optical member comprises a cylindrical lens.  
     
     
         5 . The scanner according to  claim 1 , wherein said optical member comprises a plane-parallel plate.  
     
     
         6 . The scanner according to  claim 1 , wherein said optical member comprises a member having an optical axis which lies in said plane defined by said scanning light beam and wherein said rotational axis extends perpendicular to said optical axis.  
     
     
         7 . The scanner according to  claim 1 , wherein said rotatable member is positioned in a recess formed in a housing to be rotatable about said rotational axis.  
     
     
         8 . The scanner according to  claim 7 , wherein said recess is a circular recess, and wherein said rotatable member comprises a disc portion which is fitted into said circular recess to be rotatable about said rotational axis.  
     
     
         9 . The scanner according to  claim 7 , wherein said rotatable member comprises a shaft coaxial to said rotational axis, and wherein said rotatable member is positioned in said recess with said shaft being inserted into a hole formed at the bottom of said recess so that said rotatable member is rotatable about said shaft.  
     
     
         10 . The scanner according to  claim 7 , wherein said recess is formed on an outer surface of said housing, and 
 wherein a through hole through which said optical member is inserted in said housing is formed at the bottom of said recess, and    wherein said rotatable member is positioned in said recess with said optical member being inserted into said housing through said through hole.    
     
     
         11 . The scanner according to  claim 7 , wherein said adjusting device comprises at least one set screw which penetrates into said rotatable member through a slot formed thereon to be screwed into said housing.  
     
     
         12 . The scanner according to  claim 7 , wherein said adjusting device comprises a member, fixed to said housing, for pressing said rotatable member against the bottom of said recess.  
     
     
         13 . The scanner according to  claim 12 , wherein said pressing member comprises a spring.  
     
     
         14 . The scanner according to  claim 13 , wherein said spring comprises a leaf spring fixed to said housing by at least one set screw.  
     
     
         15 . The scanner according to  claim 1 , further comprising a device for rotating said rotatable member about said rotational axis.  
     
     
         16 . The scanner according to  claim 15 , wherein said rotating device comprises: 
 a radial slot formed on said rotatable member to extend in a radial direction thereof; and    a rotating tool engageable with said rotatable member to rotate said rotatable member about said rotational axis,    wherein said tool comprises an engaging pin engageable with said radial slot, an axis of said engaging pin deviating from a rotational axis of said rotating tool.    
     
     
         17 . The scanner according to  claim 15 , wherein said rotating device comprises: 
 a circumferential gear formed on an outer peripheral surface of said rotatable member; and    a rotating tool engageable with said rotatable member to rotate said rotatable member about said rotational axis, said rotating tool comprising a pinon gear which is engaged with said circumferential gear.    
     
     
         18 . The scanner according to  claim 1 , wherein said scanning surface is a photoconductive surface of a photoconductive drum.  
     
     
         19 . The scanner according to  claim 1 , wherein said photo-detector and said light-beam emitter are supported on a common circuit substrate and do not relatively move.  
     
     
         20 . The scanner according to  claim 1 , further comprising an fθ reflecting lens that reflects said scanning light beam deflected by said light-beam deflector to said scanning surface.  
     
     
         21 . A scanner comprising: 
 a light-beam emitter for emitting a light beam;    a light-beam deflector for deflecting said light beam to scan a scanning surface;    a photo-detector provided at a position outside an image-forming scanning range of said scanning surface to detect a scanning light beam before said scanning light beam starts generating a scanning line, said photo-detector generating an output signal upon detecting said scanning light beam to determine a timing of commencement of writing said scanning line with respect to said scanning surface; and    an optical member for deflecting said scanning light beam to be incident upon said photo-detector in a direction to vary the timing of the scanning light beam incident upon said photo-detector.