| US 7,538,891 B1 | ||
| Surface characterization based on lateral shearing of diffracted wave fronts to measure in-plane and out-of-plane displacement gradient fields | ||
| Michael Mello, Phoenix, Ariz. (US); and Ares J. Rosakis, Altadena, Calif. (US) | ||
| Assigned to California Institute of Technology, Pasadena, Calif. (US) | ||
| Filed on Oct. 02, 2006, as Appl. No. 11/538,055. | ||
| Claims priority of provisional application 60/722514, filed on Sep. 30, 2005. | ||
| Int. Cl. G01B 9/02 (2006.01); G01L 1/24 (2006.01) | ||
| U.S. Cl. 356—520 [356/35.5; 356/521] | 37 Claims |
| 1. A method for optically characterizing a surface, comprising:
providing a first optical grating and a second optical grating on a sample surface of a sample, the first and second optical
gratings being along a first grating direction and a second, different direction within the sample surface and spatially overlapping
with each other;
directing a plurality of different optical probe beams to the sample surface at different incident directions, respectively;
using at least one optical shearing interferometer to receive diffracted light of the different optical probe beams from the
first and the second optical gratings, without interaction between two of the different optical probe beams, to obtain phase-shifted
optical shearing interferograms along two different shearing directions at each location that are perpendicular to a normal
direction of the sample surface at the location; and
processing obtained phase-shifted optical shearing interferograms from the different optical probe beams to generate a map
of field gradients for both in-plane and out-of-plane displacements on the sample surface.
|