| 摘要 |
PURPOSE: An objective is provided to form an imaging quality of an objective having a diffraction mirror irrelevantly to a diffraction characteristic of light. CONSTITUTION: An objective comprises an object plane(1), a lens(2), a first diffraction mirror(3), a second diffraction mirror(4), a lens group(5), a concave mirror(6), a third diffraction mirror(7), a fourth diffraction mirror(8), a second lens group(9), an intermediate focal plane(IMI), a third lens group(10) and a focal plane(IM). The objective comprises diffraction mirrors(4,7) which are not disposed at the same plane as the diffraction mirror(3,8). An incident plane of each diffraction mirror(4,7) is perpendicular to that of each diffraction mirror(3,8).
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