Patent ID: 8355140

Claim:
A system configured to generate phase information about defects on a specimen, comprising: an optical subsystem configured to combine a test beam and a reference beam to create an interference beam, wherein the test beam and the reference beam are reflected from the specimen, wherein the reference beam has a lower resolution than the test beam and is laterally shifted from the test beam in the pupil space of the optical subsystem to create spatial fringes at an image plane of the optical subsystem, wherein the optical subsystem comprises a wedge element comprising a concave element and a convex element, and wherein the system is further configured to move one or more of the concave and convex elements with respect to each other to create lateral shift between the test beam and the reference beam, wherein the optical subsystem further comprises a first pupil aperture and a second pupil aperture, wherein the first pupil aperture is different than the second pupil aperture, wherein the first pupil aperture is positioned in a path of the test beam reflected from the specimen and is not positioned in a path of the reference beam reflected from the specimen such that the first pupil aperture images the test beam and not the reference beam, and wherein the second pupil aperture is positioned in the path of the reference beam reflected from the specimen and is not positioned in the path of the test beam reflected from the specimen such that the second pupil aperture images the reference beam and not the test beam; and a detector configured to generate output representative of the spatial fringes at the image plane, wherein the output can be used to determine the phase information about the defects.