Postobjective optical deflector

A postobjective optical deflector for a postobjective optical scanning device which scans an objective surface by a light beam emitted from a semiconductor laser, comprising:

• a polygonal optical deflector for reflecting the light beam emitted from the semiconductor laser toward the objective surface, having a plurality of convex reflecting surfaces each formed of a portion of a spherical surface or a portion of the circumference of a circular cylinder having its power in the scanning direction;
• and
• a correcting lens disposed between the polygonal optical deflector and the objective surface on an optical path;
• and having a rotationally symmetric curved surface of incidence having a cross section having the shape of an arc of a circle with its center on the axis of rotational symmetry, rotationally symmetric with respect to a plane including the axis of rotation of the polygonal optical deflector and perpendicular to axis of rotational symmetry and having its power in both the feed direction and the scanning direction, and a surface of departure symmetrical with respect to a plane perpendicular to the scanning direction and having its power in the scanning direction.