Patent ID: 7283206

Claim:
A projection optical system for projecting a reduced image of a first surface on a second surface; the projection optical system comprising at least ten reflecting mirrors; the mirrors defining: a first reflecting image forming optical system G 1 for forming a first intermediate image of the first surface based on light from the first surface, a second reflecting image forming optical system G 2 for forming a second intermediate image of the first surface based on light from the first intermediate image, and a third reflecting image forming optical system G 3 for forming the reduced image on the second surface based on light from the second intermediate image, wherein the number of reflecting mirrors comprising the third reflecting image forming optical system G 3 is greater than the number of reflecting mirrors comprising the first reflecting image forming optical system G 1 and is greater than or equal to the number of reflecting mirrors comprising the second reflecting image forming optical system G 2 ; the third reflecting image forming optical system G 3 has four or more reflecting mirrors; the first reflecting image forming optical system G 1 has a first reflecting mirror M 1 and a second reflecting mirror M 2 in order of the incidence of light from the first surface; the second reflecting image forming optical system G 2 has a third reflecting mirror M 3 , a fourth reflecting mirror M 4 , a fifth reflecting mirror M 5 , and a sixth reflecting mirror M 6 in order of the incidence of light from the first intermediate image; and the third reflecting image forming optical system G 3 has a seventh reflecting mirror M 7 , an eighth reflecting mirror M 8 , a ninth reflecting mirror M 9 , and a tenth reflecting mirror M 10 in order of the incidence of light from the second intermediate image.