Patent ID: 6633423
Filing Date: 2003-10-14
Classification: G02B

Abstract:
A scanning optical system comprising:a first optical system for shaping a light beam emitted from light source means and forming the light beam into a linear image, which is elongated in the same direction as a main scanning direction; a light deflector, which has a deflection surface at or near an imaging position of said first optical system, and which deflectively scans the incident light beam in the main scanning direction; a second optical system for forming the light beam deflected by said light deflector into an image on a scanned surface in the main scanning direction; and a third optical system for forming the light beam deflected by said light deflector into an image on the scanned surface in a subscanning direction and setting the deflection surface of said light deflector and the scanned surface optically so as to be conjugate with each other, wherein the light beam guided by said first optical system is made to strike said light deflector at a predetermined angle with respect to a plane perpendicular to a rotational axis of said light deflector, wherein said third optical system comprises at least one lens, wherein said at least one lens of said third optical system is positioned to make a light beam strike said at least one lens of said third optical system at a position shifted from a surface vertex in a subscanning cross-section of said at least one lens of said third optical system by a predetermined amount in the subscanning direction to correct a deterioration in a spot shape on a scanning end portion in the main scanning direction, wherein said second optical system is located closer to said light deflector than half the distance between said light deflector and the scanned surface, and wherein |&phgr;2S|&lE;0.001 where &phgr;2S is a refracting power of said second optical system in the subscanning direction.