| 摘要 |
A very high-aperture, purely refractive projection objective having a multiplicity of optical elements has a system diaphragm ( 5 ) arranged at a spacing in front of the image plane. The optical element next to the image plane ( 3 ) of the projection objective is a planoconvex lens ( 34 ) having a substantially spherical entrance surface and a substantially flat exit surface. The planoconvex lens has a diameter that is at least 50% of the diaphragm diameter of the system diaphragm ( 5 ). It is preferred to arrange only positive lenses ( 32, 33, 34 ) between the system diaphragm ( 5 ) and image plane ( 3 ). The optical system permits imaging in the case of very high apertures of NA>=0.85, if appropriate of NA>=1.
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