| 摘要 |
PURPOSE:To shorten the length of the optical path from the scanning optical system to a scanned surface by providing a 2nd image formation optical system composed of a 1st signal lens which has a toric surface and positive refractive power in a scanning surface and a 2nd single lens which consists of a spherical surface or cylindrical surface and has negative refracting power in the scanning surface. CONSTITUTION:This system is equipped with a cylindrical lens 2 as a 1st image formation optical system which images the luminous flux from a light source 1 linearly and a 2nd image formation optical system which images the luminous flux deflected by a deflector 3 on the scanned surface 7. Namely, the 2nd image formation optical system consists of the 1st single lens 5 which has the toric surface and has the positive refracting power in the scanning surface 8 and the 2nd single lens 6 which consists of the spherical or cylindrical surface and has the negative refracting power in the scanning surface 8. Consequently, the quantity of variation of a scanning line perpendicular to scanning due to the tilt of a deflecting and reflecting surface and the quantity of curvature of field are held small and the back focus of the lens system in the scanning surface is made shorter than the focal length. |
