| 摘要 |
A first optical system (2, 4) guides a light beam from a light source (1) to an optical deflector (5), and a second optical system (6, 7) converges the light beam deflected by the optical deflector (5) on a surface to be scanned. The first optical system (2, 4) includes at least one resin lens having a diffractive surface. The second optical system (6, 7) includes at least one resin optical element. A beam diameter depth in a main scanning direction, Wm, that can have a maximum intensity of 1/e2, satisfies conditions (1) ”m1+”m2+”m3-”d1×(f2/f1)2<Wm/40 and (2) ”d1>0 and ”m2<0. |
