Anti-aliaising for optical inspection system

Abstract

A wafer inspection tool including: an illumination system providing ultraviolet illumination light with wavelengths 2 below 300 nm and configured to direct light towards an object to be inspected; a detector array having a pixel pitch; one or more anti-aliasing (AA) elements; an objective having a numerical aperture (NA) and configured to collect light provided by the illumination system and returning from a plurality of field points on the object and to onwardly transmit a light beam formed from the returning light which has been collected towards the detector array via the one or more AA elements; a processor configured to: receive imaging requirements; control a NA of the objective; control, when the pixel pitch is larger than λ/(4*NA), position of the one or more anti-aliasing elements, based on the pixel pitch, the NA, and the imaging requirements.

Dependencies are inferred from the claim text.