Optics: measuring and testing – Inspection of flaws or impurities – Having predetermined light transmission regions
Patent
1985-01-28
1987-03-03
Nelms, David C.
Optics: measuring and testing
Inspection of flaws or impurities
Having predetermined light transmission regions
356359, G01N 2188, G01B 902
Patent
active
046471960
ABSTRACT:
A flaw detection method for detecting flaw existing in the surface of a substantially plate-shaped examination object by making use of an interference of light. A coherent light is applied to the surface of the examination object and also to a reference mirror surface. The light reflected by the surface of the examination object and the light reflected by the reference mirror surface are made to interfere with each other to form an interference image from which the flaw is detected. The reference mirror surface is disposed at an optical inclination to the surface of the examination object. The reference mirror surface may be the reverse surface of the examination object while the obserse side of the same is being examined. Infrared coherent ray is preferably used as the coherent light.
REFERENCES:
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patent: 3720471 (1973-03-01), Kasahara et al.
patent: 4302108 (1981-11-01), Timson
King et al., "A Comparison of Methods for Accurate Film Thickness Measurement", J. Phys. E., vol. 5, No. 5, pp. 445-449, May 1972.
Bruce et al. "Relative Flatness Measurement of Uncoated Optical Flats", Applied Optics, vol. 14, No. 12, pp. 3082-3085, Dec. 1975.
Kwon, "Infrared Lateral Shearing Interferometers", Applied Optics vol. 19, No. 8, pp. 1225-1227, Apr. 1980.
Akiyama Nobuyuki
Endo Juro
Kuni Asahiro
Yamaguchi Kazuo
Hitachi Metals Ltd.
Koren Matthew W.
Nelms David C.
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