| 摘要 |
Disclosed are high numerical (NA) catadioptric objectives without a central obscuration, and applications thereof. 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, CaF2 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. |
