a catadioptric imaging system for micro - lithographic projection features a high numerical aperture objective where most of the focusing power is produced by reflection and refraction angles are limited to avoid additional aberration . a field correcting optic is appended to a mangin mirror in an immersive configuration for raising the numerical aperture . the optical connection between the mangin mirror and the field correcting optic is arranged to control refraction angles by limiting angles of incidence or refractive index differences . a radially symmetric polarizing effect is achieved in a pupil to improve image contrast .