Patent ID: 6574039
Filing Date: 2003-06-03
Classification: B82Y,G02B,G03F,G21K

Abstract:
An optical element comprising:an optical substrate; and a multilayered optical thin film which is formed on the optical substrate, wherein: at least one layer of the multilayered optical thin film is composed of fluoride of alkaline earth metal and is formed by a wet process; a refractive index of the at least one layer of the multilayered optical thin film with respect to a light beam having a wavelength of not more than 250 nm is not more than 1.35, and the multilayered optical thin film is an anti-reflection film, and a reflectance is not more than 0.5% with respect to the light beam having a wavelength selected from the group consisting of wavelengths of 157 nm, 193 nm, and 248 nm, provided that an angle of incidence is not more than 50 degrees.