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. 18, 1998
Filed:
Dec. 06, 1996
Shigeru Nakayama, Tokyo, JP;
Nikon Corporation, Tokyo, JP;
Abstract
Using an LIA alignment sensor, consecutive sensings of a reference-mark position are taken. I(.omega.), the power spectrum of the fluctuations of these sensings in a time period is computed. I'(.omega.), the power spectrum of the averaged fluctuations for an averaging time .DELTA.T that changes between two different measurement times .DELTA.T1 and .DELTA.T2 is then computed. The dispersion of the data averaged during this averaging time .DELTA.T matches the integral of the power spectrum I'(.omega.). The time period during which the value of the integral of the power spectrum I'(.omega.) reaches its lowest value is used as the measurement time of the position based on the beat signal obtained by the alignment sensor.