Patent ID: 8432532

Claim:
A projection optical system for projecting a pattern of an object plane onto an image plane, comprising: a first lens whose refractive index increases by ultraviolet irradiation; and a second lens whose refractive index decreases by the ultraviolet irradiation, wherein letting TT be a distance between a first intersection as an intersection of the object plane and an optical axis of the projection optical system, and a second intersection as an intersection of the image plane and the optical axis, a distance D 1 between a first central position as a central position of a thickness of the first lens on the optical axis and an intersection position of one of the first intersection and the second intersection which is closer to the first central position satisfies D 1≦ TT/ 8, and a distance D 2 between a second central position as a central position of a thickness of the second lens on the optical axis and the intersection position satisfies D 2≦ TT/ 8.