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:
Aug. 22, 1989
Filed:
Jul. 22, 1987
Yukio Matsuyama, Yokohama, JP;
Toshiaki Ichinose, Yokohama, JP;
Hitachi, Ltd., Tokyo, JP;
Abstract
System for detecting pattern defects wherein images of corresponding portions of two originally identical patterns are detected and two image signals representing the images are registered with each other, a second image signal of the two registered signals is shifted by a predetermined number of pixels with respect to a first image signal, thus providing shifted second image signals. Differences in brightness between the first and second image signals as well as each of the shifted second image signals are calculated within intervals corresponding to pixels on one scanning line, thus providing a first group of difference image signals, preset values are added to and substracted from the first or second image signal to provide a sum image signal and a substraction image signal. Differences in brightness between the second or first image signal and each of the sum and substraction image signals are calculated within the intervals to provide a second group of at least two difference signals, normality of one of the two patterns is decided when the first group of difference signals and the second group of difference signals have coexistent positive and negative signs within one interval and a minimum of absolute values of the first group of difference signals and the second group of difference signals is calculated when the first and second group of difference signals have all either positive signs or negative signs within one interval, and the mimimum is detected as a true defect when the minimum exceeds a predetermined threshold.