Patent ID: 7190512

Claim:
An optical properties restoration apparatus for improving the reliability and longevity of optical properties of an optical system by preventing, suppressing, or improving degradation of the optical properties of the optical system lying in output light or along a light path of said output light, wherein said optical system is provided within a near vacuum zone where organic components may be decomposed, said degradation is caused by carbon deposited or accumulated upon light irradiation surfaces, light reflection surfaces, light emission surfaces (collectively called ‘lighting surfaces’) of said optical system, and said lighting surfaces face said near vacuum zone, said optical properties restoration apparatus comprising: means for matching a location of the carbon deposits and a position through which a vacuum ultraviolet light is irradiated, the vacuum ultraviolet light having a wavelength of 200 nm or less; means for creating the near vacuum zone having a gas partial pressure of 20 mtorr or less so that there will be an absorption function for the vacuum ultraviolet light by gasses containing one of O 2 and water vapor on an irradiation side of the vacuum ultraviolet light on the lighting surfaces; means for generating negative ions or radicals in said near vacuum zone; means for facilitating an oxidation reaction between said negative ions or radicals and said carbon in said near vacuum zone, wherein said optical properties restoration apparatus removes or reduces the accumulated carbon which deposits on said lighting surface by the oxidation reaction.