Patent ID: 6816292
Filing Date: 2004-11-09
Classification: G02B,H04N

Abstract:
A scanning optical system for dynamically deflecting a plurality of beams simultaneously and thereby scanning the beams in a main scanning direction on a scan target surface, comprising:a light source having a plurality of light emitting points which emit the plurality of beams and a collimator lens which collimates the plurality of beams, the plurality of beams being emitted from said light source as a plurality of collimated beams collimated by the collimator lens; a first optical system including a first fixed lens group placed on a light source side of said first optical system and a movable lens group having negative finite transverse magnification with respect to images formed by said first fixed lens group, said first optical system converging each of the plurality of beams emitted from said light source in an auxiliary scanning direction perpendicular to the main scanning direction; a moving mechanism which holds said movable lens group to be movable along an optical axis of said collimator lens and selectively stops said movable lens group at a first position and a second position only, the first and second positions being determined so that transverse magnification Mp1 of said movable lens group with respect to the images formed by said first fixed lens group when said movable lens group is placed at the first position and transverse magnification Mp2 of said movable lens group with respect to the images formed by said first fixed lens group when said movable lens group is placed at the second position will satisfy Mp1Ã—Mp2=1 . . . (1); a deflecting system that dynamically deflects the plurality of beams simultaneously in the main scanning direction at a position in the vicinity of a line image formation position where a plurality of line images are formed by the convergence of the beams in the auxiliary scanning direction by said first optical system; and a second optical system which converges the dynamically deflected beams in the main scanning direction and in the auxiliary scanning direction to focus in the vicinity of said scan target surface and thereby forms a plurality of scan lines on said scan target surface.