Contamination prevention in optical system

Abstract

Disclosed are an optical structure and an exposure apparatus having the same, in which a clean gas is supplied efficiently to the surface, or in the neighborhood thereof, of an optical element being isolated from a surrounding ambience, thereby to keep the surface clean and to prevent adhesion of depositions thereon. This assures minimization of the influence of the gas flow to the imaging performance, such that contamination of the optical element can be prevented with a very small amount of gas flow. To this end, an inactive gas is blown directly against the surface of the optical element or, alternatively, it is flown along the surface in the form of a laminar flow.

Dependencies are inferred from the claim text.