| 摘要 |
PURPOSE:To make a curvature of image extremely small by specifying a relation between a radius of curvature of each refracting surface of the second image forming optical system, and a radius of curvature in the direction vertical to the main scanning direction. CONSTITUTION:The second image forming optical system for bringing a luminous flux which has been deflected by a deflector 3, to image formation onto a scanning surface is constituted of an anamorphic single lens 5, a spherical single lens 6 having a positive refractive index, and a single lens 7 having a toric surface in order from the deflector 3 side. Also, when radiuses of curvature of each refracting surface thereof are denoted as r:1, r:2, r:3, r:4, r:5, and r:6 in order from the deflector 3 side, and a component of a radius of curvature in the direction vertical to the main scanning direction, the condition of -1.0<r:6Y/r:2Y<-0.3 is allowed to be satisfied. In this way, the quantity of a curvature of image can be made small, and an optical scan can be executed with high density. |
