| 摘要 |
PROBLEM TO BE SOLVED: To correct the curving of image surface and distortion aberration and to prevent jitter caused by the mount error of a light deflector and the change of a sport diameter caused by image height by specifying the shape of an fθlens for forming a converged luminous flux into an image on a surface to be scanned. SOLUTION: The surface of a photoreceptor drum 7 is optically scanned with the luminous flux deflected by the light deflector 5 through the fθlens 6. The paraxial radius of curvature on the principal scanning surface of the lens 6 is defined as R1 and R2 in order from the side of a light deflecting element, spherical surface amounts from the paraxial lens surface of the lens surfaces on the side of the deflecting element side and the side of the surface to be scanned in the maximum effective diameter Ymax on the principal scanning surface are respectively defined as S1 and S2 , the center thickness of a single lens is defined as (d), a focal distance on the principal scanning surface is defined as (ft), and a distance from the single lens to the surface to be scanned is defined as Sk. In this case, conditions that 0<R1 <|R2|, R2 <0, (R1 <2> -Ymax <2> )<1/2> -R1 <S1 <0,|R2|-(R2 <2> -Ymax )<1/2> -d<S2 <0 and 0.2<=1-Sk/ft<=0.5 are satisfied. |
