Optical scanning unit

An optical scanning unit comprising:

• a light source module which emits a plurality of beams, each of which is independently optically modulatable;
• an optical path changing unit which changes propagation paths of the plurality of beams so that a plurality of changed beams are directed toward a plurality of exposed objects, respectively;
• and
• a plurality of f-θ lenses which correct the plurality of changed beams and have traveled along different optical paths at different magnifications in the main scanning direction than in the subscanning direction so that corrected beams are focused onto the plurality of exposed objects,
• wherein, when H is an entire length in the main scanning direction of the beam focused onto the exposed object and L is an axial distance between a reflection face of the beam deflector and the exposed object, a relationship of H and L satisfies an expression
• 0.25
• ≤
• H
• 2
• ·
• L
• ≤
• 1.75
• .

A method of arranging optical components in an optical scanning device, comprising:

• providing a light source which emits a beam, a beam deflector which deflects the beam so that the beam scans in a main scanning direction of an exposed object;
• and an f-θ lens which corrects the beam deflected by the beam deflector so that a corrected beam is focused onto the exposed object, the correcting being at different magnifications for the main scanning direction than for the subscanning direction;
• and
• setting a distance between the beam deflector and the exposed object so that the following expression is satisfied
• 0.25
• ≤
• H
• 2
• ·
• L
• ≤
• 1.75
• ,
• wherein, H is an entire length in the main scanning direction of the beam focused onto the exposed object and L is an axial distance between a reflection face of the beam deflector and the exposed object.