Patent Document ID: 9581430
Application ID: 14057827
Patent Status: 1

Claim One:
1. A system comprising: an illumination source arranged to produce electromagnetic radiation having a coherence length of less than 30 microns; a reference optical element; a phase controlled interferometer arranged to: receive the radiation from the illumination source; split the radiation between a target and the reference optical element, wherein the interferometer is arranged to controllably introduce a phase between radiation directed to the target and to the reference optical element; and, generate, from reflected radiation from the target and from the reference optical element, an interference beam; an imaging unit arranged to receive the interference beam and generate a plurality of interferometry images derived using phase characterization corresponding to different introduced phases at at least one of a pupil plane and a field plane, wherein the plurality of interferometry images are used to introduce a phase difference with the phase controlled interferometer to refine a focus signal calculation.