Patent ID: 7990543
Filing Date: 2011-08-02
Classification: G01B

Abstract:
1. A method for optically characterizing a sample surface, comprising: operating a laser to produce a single probe beam that is collimated and coherent; directing the single probe beam onto an area of incidence on a sample surface; obtaining a wavefront that propagates away from the area of incidence, wherein a phase of the wavefront carries information on the sample surface; operating an optical interferometer to obtain copies of the wavefront, wherein the copies are spatially separated; operating the optical interferometer to induce a relative phase shift of π/2 between the copies of the wavefront; operating the optical interferometer to cause interference between each copy of the phase shifted wavefront and a corresponding reference wavefront based on a self-referencing interferometry, without using a reference reflector separated from the sample surface, to obtain optical interferograms from the sample surface that are relatively separated in phase by π/2; and processing the obtained optical interferograms to extract information on the sample surface, wherein each copy of the phase shifted wavefront is self-referenced through a laterally sheared duplicate wavefront which operates as a respective corresponding reference wavefront produced by using two grating elements spaced along a propagation direction of each phase-shifted wavefront to produce each respective optical interferogram of the optical interferograms.