| 摘要 |
<P>PROBLEM TO BE SOLVED: To provide high numerical (NA) catadioptric objectives without a central obscuration, and applications thereof. <P>SOLUTION: Such objectives can operate through a wide spectral bandwidth of radiation, including deep ultraviolet (DUV) radiation. Importantly, refractive elements in the catadioptric objectives can be manufactured from a single type of material (such as, for example, CaF<SB>2</SB>and/or fused silica). In addition, the elements of such catadioptric objectives are rotationally symmetric about an optical axis. The catadioptric objectives eliminate the central obscuration by (1) using a polarized beamsplitter (which passes radiation of a first polarization and reflects radiation of a second polarization), and/or (2) using one or more folding mirrors to direct off-axis radiation into the pupil of the catadioptric objective. An example catadioptric objective is shown in Fig.2. <P>COPYRIGHT: (C)2010,JPO&INPIT |
