US Patent 7663657 Optical scanning device and image forming apparatus

An optical scanning device includes a light source having light emitting points for emitting light beams, a coupling optical element that couples the light beams, a deflecting unit that deflects and scans the light beams, and a scanning optical system that focus the light beams to form an image. The optical scanning device satisfies the following condition: F tan(θ/2)+A<D/0.7 where A is the maximum distance between the light emitting points and an optical axis of the coupling optical element, θ is a divergence angle (full-width half-maximum) of the light beams, F is a focal length of. the coupling optical element, and D is an effective radius of the coupling optical element.