Optical characteristic recovery method of optical element e.g. light transmissive window of ultraviolet lamp, involves forming vacuum region of activity energy existence, at side of photo-irradiation surface of optical system

摘要

A vacuum region (14) of activity energy existence, where an oxidation reaction of carbon is excited, is formed at the side of photo-irradiation surface of an optical element e.g. light transmissive window (8). Negative ion or radical is generated in the vacuum region, to produce oxidation reaction between carbon (15) adhered to photo-irradiation surface, to remove or decrease adhered carbon. An independent claim is also included for optical characteristic recovery apparatus.