Radiant energy – Photocells; circuits and apparatus – Optical or pre-photocell system
Patent
1981-03-11
1983-12-27
Nelms, David C.
Radiant energy
Photocells; circuits and apparatus
Optical or pre-photocell system
356446, G01N 2188
Patent
active
044233310
ABSTRACT:
A method and apparatus of inspecting a surface of a specimen for the presence of defects, foreign substance and the like are disclosed. The surface has a mark such as a cutting mark formed thereon and composed of fine grooves or recesses extending in a predetermined direction. The surface is scanned two-dimensionally with an irradiating laser beam impinging or illuminating on the specimen surface perpendicularly thereto. Those of the irregularly scattered laser light rays reflected from the specimen surface which are in a first direction perpendicular to the lengthwise direction of the mark are intercepted by a shielding member or caused to pass through regions other than a reflecting region of a reflecting mirror, while those scattered light rays which are in other directions than the first direction are directed to a photoelectric converter tube along a bypass path across the shielding member or through reflection of the mirror. A picture signal derived from the output of the photoelectric converter tube is digitalized into binary picture element signals by a sampling and binary encoding circuit, the resulting signals being then stored in a two-dimensional memory. The presence and forms of defects, foreign substances and the like on the specimen surface are discriminatively determined in dependence on particular combinations of the binary picture element signals stored in the memory.
REFERENCES:
patent: 3659950 (1972-05-01), Troll et al.
patent: 3879131 (1975-04-01), Cuthbert et al.
patent: 4095905 (1978-06-01), Kuni et al.
patent: 4197011 (1980-04-01), Hudson
patent: 4202627 (1980-05-01), Suzuki et al.
"A Laser Scan Technique for Electronic Materials Surface Evaluation" by Oswald et al., Jour. of Electronic Material, vol. 3, No. 1, 1974.
Akiyama Nobuyuki
Koizumi Mitsuyoshi
Oshima Yoshimasa
Hitachi , Ltd.
Nelms David C.
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