| 摘要 |
An optical system (10) comprises three lens sections, a catadioptric objective lens section (128), a reimaging lens section (50) and a zoom lens section (139), which are all aligned along the optical path of the optical system. The reimaging lens section re-images the system pupil such that the re-imaged pupil is accessible separately from any of the lens sections. The optical system may also include a beamsplitter (132), which creates a separated illumination pupil (46) and collection pupil (48). The illumination pupil (46) and the collection pupil (48) may then be manipulated with an illumination aperture and a collection aperture, respectively, so that the optical system may operate in various test modes such as brightfield, ring darkfield, full-sky illumination, and laser darkfield with Fourier filtering capability. The invention also pertains to a method that includes operations of directing radiation from a radiation source so that the radiation passes through the illumination pupil (46) and the collection pupil (48) of the optical system, and operations for configuring the illumination pupil (46) and the collection pupil (48) so that the optical system may operate in either of the above modes of illumination, with Fourier filtering capability.
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