| US 7,453,630 B2 | ||
| Optical properties apparatus, the restoration method, and an optical system used in the apparatus | ||
| Satoshi Sakai, Yokohama (Japan); Shigenori Tsuruga, Yokohama (Japan); Hideo Yamakoshi, Yokohama (Japan); Shizuma Kuribayashi, Yokohama (Japan); Minoru Danno, Yokohama (Japan); Hiroshi Futami, Yokohama (Japan); and Noriko Yamazaki, Yokohama (Japan) | ||
| Assigned to Mitsubishi Heavy Industries, Ltd., Tokyo (Japan) | ||
| Filed on Mar. 06, 2007, as Appl. No. 11/682,789. | ||
| Application 11/682789 is a division of application No. 10/833998, filed on Apr. 29, 2004, granted, now 7,190,512. | ||
| Prior Publication US 2007/0158599 A1, Jul. 12, 2007 | ||
| Int. Cl. F21V 9/06 (2006.01); G02B 5/20 (2006.01) | ||
| U.S. Cl. 359—361 [359/350] | 4 Claims |
| 1. A method to use an optical apparatus, comprising steps of:
applying in advance a protective film of a metal oxide selected from the group consisting of Al2O3, MgO, TiO2, and ZrO2 to an optical system, wherein
a total thickness of all film applied to the optical system is 2 nm-10 nm, and
said protective film suppresses the stripping off of a structural element from the surface of a base stock of said optical
system or the oxidation of the surface of the base stock of said optical system, by the irradiation of vacuum ultraviolet
light over time or the plasma exposure to the base stock,
incorporating said optical system into a desired device that has vacuum ultraviolet light sources or plasma light sources
which has higher photon energy than an absorption wavelength of the base stock of said optical system, and
forming the protective film on the optical system, wherein
the optical system comprises of mono-crystal fluoride material having the crystal axis (the c axis) along the direction of
the light irradiation, and
a perpendicular surface of said protective film is coated by Si02 or metal oxides.
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