Radiant energy – Photocells; circuits and apparatus – Optical or pre-photocell system
Patent
1989-10-27
1991-03-12
Nelms, David C.
Radiant energy
Photocells; circuits and apparatus
Optical or pre-photocell system
356237, G01N 2186
Patent
active
049995103
ABSTRACT:
An apparatus for detecting foreign particles on a surface of a reticle or pellicle comprises an optical system through which a light beam forms a light spot on the surface. The surface and the light spot are shifted relatively so that the light spot scans the surface. Light detectors receive light scattered by a foreign particle and directed in different directions, respectively, and generated photoelectric outputs by which the presence of the foreign particle is discriminated. Beam diameter and scanning speed are varied to provide the most effective operation for particles of different sizes.
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Tanimoto, Akikazu et al., SPIE, vol. 470, pp. 242-249.
Hayano Fuminori
Imamura Kazunori
Kato Kinya
Murata Sunao
Messinger Michael
Nelms David C.
Nikon Corporation
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