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:
Nov. 04, 1997
Filed:
Dec. 21, 1994
Ayako Sugaya, Kawasaki, JP;
Masahiro Nakagawa, Yokohama, JP;
Nikon Corporation, , JP;
Abstract
In a position detecting apparatus, according to this invention, a convexly and concavely patterned wafer mark is imaged on an image pickup surface via an imaging optical system, and the image on the image pickup surface is detected. The position detecting apparatus defocuses the average surface of the wafer mark from the optimum focusing surface depending on the pitch and difference in level of the wafer mark, etc., in the direction of the optical axis of the imaging optical system, and varies an illumination .sigma. value definded as the ratio of the numerical aperture of the illumination optical system and the numerical aperture of the imaging optical system. Then the position detecting apparatus provides lights from the wafer mark to the image pickup surface with rotation-symmetric wave aberration to allow the resulting image to have the highest contrast for positional detection.