Optics: measuring and testing – Crystal or gem examination
Patent
1993-05-10
1995-04-11
Evans, F. L.
Optics: measuring and testing
Crystal or gem examination
356 36, 356237, 356446, G01N 2188
Patent
active
054063671
ABSTRACT:
Apparatus for detecting and mapping defects in the surfaces of polycrystalline materials in a manner that distinguishes dislocation pits from grain boundaries includes a laser for illuminating a wide spot on the surface of the material, a light integrating sphere with apertures for capturing light scattered by etched dislocation pits in an intermediate range away from specular reflection while allowing light scattered by etched grain boundaries in a near range from specular reflection to pass through, and optical detection devices for detecting and measuring intensities of the respective intermediate scattered light and near specular scattered light. A center blocking aperture or filter can be used to screen out specular reflected light, which would be reflected by nondefect portions of the polycrystalline material surface. An X-Y translation stage for mounting the polycrystalline material and signal processing and computer equipment accommodate rastor mapping, recording, and displaying of respective dislocation and grain boundary defect densities. A special etch procedure is included, which prepares the polycrystalline material surface to produce distinguishable intermediate and near specular light scattering in patterns that have statistical relevance to the dislocation and grain boundary defect densities.
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B. L. Sopori, Use of Optical Scattering to Characterize Dislocations Semiconductors, 22 Appl. Optics 4676 (1988).
Evans F. L.
Midwest Research Institute
O'Connor Edna M.
Richardson Ken
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