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. 06, 1990
Filed:
Dec. 22, 1989
Masato Aketagawa, Yokohama, JP;
Canon Kabushiki Kaisha, Tokyo, JP;
Abstract
A projection exposure system is disclosed, which includes: a laser; a mask stage for supporting a photomask; a wafer stage for supporting a wafer; an illumination optical system effective to illuminate the photomask by use of a light from the laser; a projection optical system for projecting, upon the wafer, a circuit pattern formed on the photomask; an adjusting device for adjusting the wavelength to be emitted from the laser; a discharge tube disposed on a path for at least a portion of the light from the laser and being adapted to emit a predetermined line spectrum; a detecting device for detecting a change in a discharged electric current from the discharge tube; and a control device for controlling the adjusting device on the basis of an output signal from the detecting device.