| 摘要 |
PURPOSE:To provide a scanning optical system with low influence due to temperature change even when a lens provided with a modified toric plane is formed with a plastic lens as providing an ftheta lens with the modified toric plane whose radius of curvature in a sub scanning direction is decided independently from that in a main scanning direction. CONSTITUTION:This system is constituted in such a way that a cylindrical lens 3 which image-forms luminous flux emitted from a semiconductor laser 1 once in the sub scanning direction, a polygonal mirror 4 provided in the neighborhood of an image-forming position and which deflects the luminous flux, and the ftheta lens system 10 which image-forms the luminous flux deflected by the polygonal mirror 4 are provided, and the ftheta lens system 10 is comprised by arranging image-forming lenses 11, 12 and a correction lens 13 sequentially observing from a polygonal mirror 4 side, and the correction lens 13 is provided with the modified toric plane 13a whose radius of curvature in the sub scanning direction is decided independently from that in the main scanning direction, and it is formed in a meniscus lens whose convex surface is faced with an image surface 5 side. |
