| 摘要 |
PROBLEM TO BE SOLVED: To attain effective multibeam scanning by satisfactorily correcting the curve of an image surface in main and sub scanning directions while excellently holding the conjugating function and constant speed function of a scanning image formation lens. SOLUTION: This multibeam scanner is constituted so that the constant speed optical scanning for plural scanning lines of a surface 8 to be scanned is executed by forming plural beams from plural light emitting parts as respective linear images extended in a main scanning correspondence direction, deflecting respective linear images at constant angular velocity by a light deflector 5 having a deflecting reflection face A in the vicinity of the image forming positions of respective linear images and converging respective deflected beam on the surface 8 to be scanned by the same scanning image formation lens as optical spots separated in the sub-scanning direction. The scanning image formation lens is constituted of two lenses 6, 7, the lens 6 is positive meniscus lens turning its concave face to the topical deflector side and has coaxial aspherical shapes on its both faces and the lens 7 has a non-circular arc shape in a main scanning cross section at least on one face and can change a radius of curvacture in the sub-scanning cross section in the main scanning correspondence direction so that a center line of curvature obtained by connecting the centers of curvature in respective sub-scanning cross sections of the lens face in the main scanning corresponding direction becomes a curve different from the non-circular arc shape in the main scanning cross section. |
