| 摘要 |
PROBLEM TO BE SOLVED: To surely restrain the unevenness of the pitch of a scanning line and to obtain excellent image quality in a scanning optical system whose reflecting angle exceeds 50 deg. by setting the scanning optical system so that the curved amount of a conjugate point may satisfy a specified condition. SOLUTION: This scanner is equipped with an fθlens system having power only in a main scanning direction and the scanning optical system consisting of a cylindrical mirror 111 having power only in a subscanning direction. An fθlens 108 is arranged to be inclined in a direction where an angle formed with an incident light beam gets larger, and light reflected and deflected by a rotary polygon mirror 109 is transmitted through the lens 108 again. The deflected light beam transmitted through the lens 108 is reflected at the angle of >=50 deg. by the mirror 111 and reaches a photoreceptor drum 305. The scanning optical system is set so that the curved amount C of the conjugate point may satisfy an expression: (C/2+Z)×tan(2δ/M)<2.54R when it is assumed that the maximum plane tilt amount of a light deflector isδ, conjugate magnification is M, the production error of the conjugate point is Z, and resolution in the subscanning direction is R. |
