| 摘要 |
PURPOSE:To correct an ftheta characteristic and the curvature of an image surface by constituting a titled system so that a paraxial radius of curvature of a corrected aspherical surface becomes reverse to the aspherical surface displacement direction. CONSTITUTION:In a light scanning optical system constituted of a light source, an optical system for shaping a beam from the light source, a beam deflecting device, an image forming element for forming as an image the deflected beam on a recording medium, and a corrected aspherical lens placed in the vicinity of the recording medium, a paraxial radius of curvature of the corrected aspherical surface is set in reverse to the aspherical surface displacement direction. That is to say, in case of converting a surface r4 of the recording medium side of the corrected aspherical lens 3, to an aspherical surface, a paraxial radius of curvature R of its aspherical surface is set to O<=R. Also, in order to improve the workability, when an effective half-value length of a beam deflection range is denoted as, it is desirable that the paraxial radius of curvature R is O<(1R1)<-1(1.5Y)<-1>. In this way, an ftheta characteristic and a curvature of image are also corrected well. |
