The patent badge is an abbreviated version of the USPTO patent document. The patent badge does contain a link to the full patent document.
The patent badge is an abbreviated version of the USPTO patent document. The patent badge covers the following: Patent number, Date patent was issued, Date patent was filed, Title of the patent, Applicant, Inventor, Assignee, Attorney firm, Primary examiner, Assistant examiner, CPCs, and Abstract. The patent badge does contain a link to the full patent document (in Adobe Acrobat format, aka pdf). To download or print any patent click here.
Patent No.:
Date of Patent:
Feb. 11, 1997
Filed:
Jul. 21, 1995
Michio Kohno, Tokyo, JP;
Canon Kabushiki Kaisha, Tokyo, JP;
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.