Optics: measuring and testing – Inspection of flaws or impurities – Having predetermined light transmission regions
Patent
1990-09-18
1993-07-06
Rosenberger, Richard A.
Optics: measuring and testing
Inspection of flaws or impurities
Having predetermined light transmission regions
356338, G01N 2101
Patent
active
052258866
ABSTRACT:
Disclosed herein are method of and apparatus for detecting a foreign substance on an object by illuminating said object, detecting via an optical system light reflected from said object and detecting said foreign substance in distinction from a background. The object is exposed to first illumination such that light reflected from said background is suppressed but light reflected from said foreign substance is highlighted relative to the light reflected from said background. The light reflected from said object as a result of said first illumination is detected, thereby obtaining a first detection signal. The object is exposed to second illumination such that light reflected from said background is free from suppression relative to the light reflected from said substance as a result of said second illumination. The light reflected from said object as a result of said second illumination is detected, thereby obtaining a second detection signal. Foreign-substance-highlighting processing is performed on said first detection signal by using said second detection signal, whereby said substance is detected.
REFERENCES:
patent: 3790287 (1974-02-01), Cuthbert et al.
patent: 4391524 (1983-07-01), Steigmeier et al.
patent: 4740079 (1988-04-01), Koizumi et al.
patent: 4806774 (1989-02-01), Lin et al.
patent: 4889998 (1989-12-01), Hayano et al.
Koizumi Mitsuyoshi
Ohshima Yoshimasa
Hitachi , Ltd.
Rosenberger Richard A.
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