Patent ID: 7630057

Claim:
A projection optical system for forming a reduced image of a first surface on a second surface, comprising: a first reflecting image forming optical system for forming an intermediate image of the first surface, the first reflecting image forming optical system comprising a first reflecting mirror M 1 , a second reflecting mirror M 2 , a third reflecting mirror M 3 , and a fourth reflecting mirror M 4 in order of incidence of light from the first surface side; and a second reflecting image forming optical system for forming an image of the intermediate image on the second surface, the second reflecting image forming optical system comprising a fifth reflecting mirror M 5 , a sixth reflecting mirror M 6 , a seventh reflecting mirror M 7 , and an eighth reflecting mirror M 8 in order of incidence of light from the first surface side, the first reflecting mirror M 1 , the fourth reflecting mirror M 4 , the fifth reflecting mirror M 5 , and the eighth reflecting mirror M 8 having concave reflecting surfaces, the seventh reflecting mirror M 7 having a convex reflecting surface, one of the reflecting mirrors from among the second reflecting mirror M 2 and the third reflecting mirror M 3 having a concave reflecting surface, and the other reflecting mirror having a convex reflecting surface, and wherein when the distance between an optical axis and the center of an arcuate effective image forming region formed on the second surface is Yc, and the width dimension of the effective image forming region along a direction that connects the optical axis and the center of the effective image forming region is Dw, the condition 0.06<Dw/Yc is satisfied.