Patent ID: 7119880

Claim:
A projection optical system for performing reduction projection of a pattern of a reticle onto a projection plane, said system comprising: a first mirror having a concave reflective surface; a second mirror having a reflective surface; a third mirror having a convex reflective surface; a fourth mirror having a concave reflective surface; a fifth mirror having a convex reflective surface; and a sixth mirror having a concave reflective surface, wherein said first, second, third, fourth, fifth and sixth mirrors are disposed in the order named from the reticle, the reflective surface of said fourth mirror has a curvature radius of not less than 400 mm and not more than 800 mm in absolute value, the reflective surface of said sixth mirror has a curvature radius of not less than 400 mm and not more than 600 mm in absolute value, the reflective surfaces of said first, second, third, fourth, fifth and sixth mirrors have a curvature radius of not more than 1500 mm in absolute value, respectively, and said projection optical system forms an intermediate image of the pattern between said fourth mirror and said fifth mirror.