A projection exposure apparatus (10) for forming an image of a pattern present on a first object such as a reticle (R) onto a second object, such as a wafer (W). The apparatus comprises along three optical axes (AZ1, AX, AZ2), an illumination optical system capable of illuminating the reticle with partially polarized light, and a catadioptric projection optical system (40-70) arranged adjacent the reticle and opposite the illumination optical system. The catadioptric projection optical system comprises one or more substantially spherical mirrors (48), a plurality of refractive members (42, 48, 72, 74), and one or more plane mirrors (60, 66). The plane mirrors are designed and arranged so as to allow a substantially unpolarized image of the reticle pattern, which is illuminated with partially polarized light, to be formed on the wafer.