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:
Apr. 09, 1991
Filed:
May. 24, 1989
Abstract
An illumination system applicable to contact or proximity exposure apparatuses provides excellently collimated light without any irradiance reduction in the peripheral area of an object to be illuminated and includes a light source, an ellipsoidal mirror positioned with respect to the light source, an optical system designed so that the entrance height of the light received in the entrance pupil thereof is substantially proportioned to the tangent of the exit angle in the exit pupil thereof, and a single Fresnel lens designed so that light passing therethrough is abated in the spherical aberration. Light exiting from the optical system is received on the front surface of the Fresnel lens, where the irradiance distribution is uniform through the surface, and the Fresnel lens transmits light received with abated spherical aberration to a mask film bearing a desired circuit pattern.