OPTICAL SCANNING DEVICE AND IMAGE FORMING APPARATUS

摘要

An optical scanning device includes: a common optical deflector that deflects light beams from light source devices; and a scanning optical system that focuses the deflected light beams on different scanning surfaces. All the light beams from the light source devices are incident on the optical deflector in directions oblique to a normal line of the scanning surfaces in a main-scanning cross section and to a normal line of a deflecting reflection plane of the optical deflector in a sub-scanning cross section. The scanning optical system includes individual lenses which are individually arranged for the respective light beams and have a plane shape symmetric in the main-scanning direction and satisfies a predetermined condition, and an optical axis of the individual lens is arranged obliquely to the normal line of the scanning surface in the main-scanning cross section so as to satisfy a predetermined condition.

主权项

1. An optical scanning device comprising:
a plurality of light source devices; a common optical deflector that deflects light beams from the light source devices; and a scanning optical system that focuses the deflected light beams on different scanning surfaces to scan the scanning surfaces in a main-scanning direction, wherein all the light beams from the light source devices are incident on the optical deflector in directions oblique to a normal line of the scanning surfaces in a main-scanning cross section and to a normal line of a deflecting reflection plane of the optical deflector in a sub-scanning cross section, the scanning optical system includes a common lens which is commonly used for the light beams scanned by the same deflecting reflection plane and individual lenses which are individually arranged for the respective light beams and have a plane shape symmetric in the main-scanning direction, when a light flux whose sub-scanning position of when reaching the scanning surface is farthest from a sub-scanning position at a central image height is defined as a first light flux, and a light flux toward an edge image height closer to where the first light flux reaches is defined as a second light flux, and an optical path length of the first light flux from the individual lens to the scanning surface is denoted by La, a power in the sub-scanning direction at a position where the first light flux passes through the individual lens is denoted by φa, an emission angle of the first light flux from the individual lens in the main-scanning cross section is denoted by ωa, an optical path length of the second light flux from the individual lens to the scanning surface is denoted by Lb, a power in the sub-scanning direction at a position where the second light flux passes through the individual lens is denoted by φb, and an emission angle of the second light flux from the individual lens in the main-scanning cross section is denoted by ωb, the individual lens satisfies the following condition formula (6),(Lbφb-1)cosωa(Laφa-1)cosωb<1(6) an optical axis of the individual lens is arranged obliquely to the normal line of the scanning surface in the main-scanning cross section such that the following condition formula (7) is satisfied, when a sub-scanning position shift amount of the first light flux on an image plane by tilting the individual lens is denoted by ΔVa, and a difference between a central image height and a sub-scanning position of the first light flux on the image plane of when the individual lens is not tilted is denoted by δ.ΔVa<2δ1-(Lbφb-1)cosωa(Laφa-1)cosωb(7)