Illuminating apparatus for an object under test in an interferometer with an optical axis (OA) has radiation director directing radiation at object from different locations distant from axis

摘要

The apparatus includes at least one source of radiation. A radiation directing element directs radiation from the source at the object (102). The radiation directing element directs radiation at the object from different locations that are distant from the optical axis (OA) such that radiation from the location is incident to the same points on the object along optical paths with identical optical path difference within the interferometer. Independent claims are also included for the following: (a) an interferometric apparatus; (b) an illumination method for use with an interferometer; (c) an interferometric method.