SCANNING OPTICAL SYSTEM AND SCANNING LENS

Provided is a scanning optical system, wherein, with a scanning direction on a surface as a y-axis, a principal ray perpendicularly incident on the surface as a z-axis, a reflection point on the deflector of the principal ray as an origin point, the distance from the origin point to the surface as L, the length of a scanning path on the surface as W, the maximum value and the minimum value of they-coordinate of a point at which the principal ray passes an emission surface of the scanning lens as ymax and ymin, respectively, the curvature in a main scanning direction of the emission surface atthe point as c, and the refractive index of a material as n, power phi = (1-n)*c in the main scanning direction at the point is defined, and with the maximum value of the absolute value of dphi/dy inranges from ymin to 0.6ymin and from 0.6ymax to ymax as absolute value of dphi/dy out, and the maximum value of the absolute value of dphi/dy in a range from 0.6ymin to 0.6ymax as absolute value of phi/dyin, 0.54