Patent ID: 7924434

Claim:
A system configured to generate output corresponding to defects on a specimen, comprising: an optical subsystem configured to create interference between a test beam and a reference beam, wherein the test beam and the reference beam are reflected from the specimen, wherein the optical subsystem 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, 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, wherein the optical subsystem further 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; and a detector configured to generate output representative of the interference between the test and reference beams, wherein the interference increases contrast between the output corresponding to the defects and output corresponding to non-defective portions of the specimen.