Optical projection system.

摘要

A first lens, a second lens, and a third lens are arranged successively in a direction of travel of a ray. The first lens has a predetermined negative refracting power. The second lens has a predetermined negative refracting power. The third lens has a predetermined positive refracting power. A group of fourth lenses follows the third lens in the direction of travel of the ray and has a predetermined positive refracting power. At least one of surfaces of the first, second, third, and fourth lenses is aspherical. The following conditions (1), (2), and (3) are satisfied: (1) 4f < f3 < 20f (2) 0.65 < (f4/d34) < 1.40 (3) 10f < R5 where the character "f" denotes a focal length of the optical projection system, the character "f3" denotes a focal length of the third lens, the character "f4" denotes a focal length of the fourth lens group, the character "d34" denotes a distance between a rear principal point of the third lens and a front principal point of the fourth lens group, and the character "R5" denotes a radius of curvature of a front surface of the third lens.