Illumination system.

摘要

Disclosed is an illumination system applicable to contact or proximity exposure apparatus, which provides exellently well-collimated light without any irradiance reduction in peripheral area of an object to be illuminated. The illumination system according to the invention includes a light source (LS), an ellipsoidal mirror (EM) positioned with respect to the light source, an optical system (OS) 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 (CS) designed so that light passed therethrough is abated in the sperical aberration. Light exited from the optical system is received on the front surface of the Fresnel lens (CS), where the irradiance distribution is uniform through the surface, and the Fresnel lens transmits light received with abating the sperical aberration to a mask film (MF) bearing a desired circuit pattern. Desired exposure is made on a photosensitive material (PM) with exellently well-collimated light.