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:
Jan. 26, 1999
Filed:
Jul. 08, 1997
Applicant:
Inventors:
Kazuhiro Takahashi, Utsunomiya, JP;
Hirohiko Shinonaga, Utsunomiya, JP;
Assignee:
Canon Kabushiki Kaisha, Tokyo, JP;
Attorney:
Primary Examiner:
Int. Cl.
CPC ...
G02B / ;
U.S. Cl.
CPC ...
359637 ; 359822 ; 355 71 ; 353101 ; 250548 ; 356375 ;
Abstract
In a projection exposure apparatus, two plane-parallel plates, which are equal in thickness and refractive index, are interposed between a projection optical system and a wafer. By tilting these two plane-parallel plates at the same angle in opposite directions with respect to the optical axis of the optical system by means of an adjusting device, astigmatism caused in the optical system by exposure is corrected. The amount of astigmatism is calculated by a calculating device based on the amount of light incident on the optical system per unit of time which is obtained according to the output of a light amount sensor.