Optical scanning apparatus

Claim 1

An optical scanning apparatus for scanning a scanning object along a scanning axis, said apparatus comprising: rotatable light deflecting means for deflecting a plurality of scanning light beams; and lens means including a spherical surface having an f-θ characteristic, for receiving deflected light beams from said light deflecting means at a plurality of inclinations relative to the optical axis of said lens means, to focus the received deflected light beams onto the scanning object; wherein the following condition is met: ##EQU9## where f represents the focal distance of said lens means (mm), ω represents the effective scanning rotation angle of said light deflecting means (deg), Δ(ω) represents the amount of curve (mm) in a subscanning direction at each angle ω of the scanning line if a light beam were to enter said lens means at an incident height h parallel to the optical axis of said lens means, ρ represents the resolution of the scan on the scanning object (lines/mm), θ represents the angle of inclination of any one of the light beams relative to the optical axis of said lens means within a plane which contains the optical axis of said lens means and which is perpendicular to the scanning axis (deg), L represents the distance between a first reflection surface of said light deflecting means and a principal plane of said lens means adjacent the scanning object along the optical axis, and h represents the height of incidence of any one of said light beams on said lens means (mm) relative to the optical axis of said lens means.