Optics: measuring and testing – Inspection of flaws or impurities – Having predetermined light transmission regions
Patent
1995-07-21
1997-02-11
McGraw, Vincent P.
Optics: measuring and testing
Inspection of flaws or impurities
Having predetermined light transmission regions
G01N 2188
Patent
active
056026390
ABSTRACT:
A method and an apparatus for inspecting surface conditions of an object, on which a pattern is formed, by detecting scattered light generated by the surface of the object using a detection optical system. The method includes the steps of illuminating the surface of the object, providing first and second photodetectors on a pupil plane of the detection optical system, generating a first signal corresponding to the sum of the outputs of the first and second photodetectors, and a second signal corresponding to the difference between the outputs of the first and second photodetectors, and comparing the first signal with a first threshold value and the second signal with a second threshold value to obtain the logical product of the results of the comparisons for inspecting the surface of the object. The apparatus includes a detection optical system for detecting scattered light generated by the object illuminated by an illuminating device, first and second photodetectors provided at the pupil plane of the detection optical system, a device for comparing a signal corresponding to the sum of outputs of the first and second photodetectors with a first threshold value, and for comparing a signal corresponding to the difference between the outputs of the first and second photodetectors with a second threshold value, and a device for detecting the logical product of the results of the comparison by the comparison device.
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Canon Kabushiki Kaisha
McGraw Vincent P.
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