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. 21, 1995
Filed:
Aug. 28, 1992
Hitachi, Ltd., Tokyo, JP;
Abstract
A method for detecting a period of a periodically varying signal and/or an inclination of a specimen utilizing an exposure apparatus wherein a coherent light is divided into first and second lights and the first light is irradiated onto the specimen at a predetermined angle, and a reflected light thereof and a reference light as the second light interfere with each other so as to form interference fringes, the interference fringes are detected, and the inclination of the specimen is detected from a pitch representing a period of the interference fringes. The method includes detecting a spectrum of a signal intensity obtained from the detected interference fringes or the periodically varying signal, subjecting the detected spectrum data to a fast complex Fourier transformation, calculating a true spectrum peak position j.sub.R in accordance with a relationship j.sub.R =j.sub.0 +.DELTA., where j.sub.0 is a detected spectrum peak position and .DELTA. is a correcting value estimated from the Fourier transformed spectrum data adjacent to j.sub.0, and calculating the pitch P of the period of the signal intensity information in accordance with a relationship P=N/j.sub.R, where N is the number of sample data points for the complex Fourier transformation. Further, the method includes calculating the inclination of the specimen from the pitch P.