While increasing the projection area, and weight of the optical system is capable of projection optical system. Projection optical system of reflection refraction type to be formed in a projection magnification of the expansion plate (P) on the image of the pattern of the mask (M) in (PL1), in the optical path between the mask (M) and plate (P) and The first lens group concave reflecting mirror disposed between (CCMb), is disposed in an optical path between the mask (M) and the concave reflecting mirror and (CCMb) and (G1b), and the first (CCMb) concave reflecting mirror a second lens group disposed between lens groups and (G1b) and (G2b), is disposed on the optical path between the concave reflecting mirrors (CCMb) plates and (P), rotationally asymmetric at least one and a (G3b) the third lens group including a lens outer shape.
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