Patent ID: 7626744

Claim:
An optical scanning device that scans a writing area on a scan-target surface with a plurality of light beams in a main scanning direction, the optical scanning device comprising: a light source including a plurality of light emission outlets arranged two-dimensionally; a first optical system including a coupling lens for coupling the light beams output from the light emission outlets; an aperture member having an opening and placed at or near a focal position of the coupling lens; a rotating polygon mirror including a plurality of deflecting surfaces, each of the deflecting surfaces deflecting light beams that have passed through the opening in the aperture member; and a second optical system that collects the light beams deflected by the rotating polygon mirror on the writing area on the scan-target surface, wherein W is a distance between, among the light emission outlets, light emission outlets spaced farthest apart from each other in the main scanning direction, E is a dimension of the opening of the aperture in the main scanning direction, Rc is a radius of a circle inscribing the rotating polygon mirror, M is a number of deflecting surfaces of the rotating polygon mirror, α is an angle of incidence of the light beams on the deflecting surfaces, φ is an angle of view of the second optical system from start to end of scanning on the writing area, x is a distance between the aperture member and the rotating polygon mirror, f 1 is a focal length of the coupling lens, and 2 ⁢ Rc × tan ⁡ ( π M ) × cos ( α + φ / 4 2 ) - E - W × x f 1 - Rc × sin ⁢ ϕ 2 ⁢ cos ⁢ α 2 > 0.