| 摘要 |
<p>An optical device (1) which has an optical substrate (10) and a multilayer optical thin film (11 - 16) formed on the optical substrate (10). The MgF2 layers (12 and 16) of the multilayer optical thin film have a refractive index of 1.10 - 1.35, more particularly 1.15 - 1.25, for vacuum ultraviolet ray with a wavelength of not longer than 250nm. Therefore, if the optical device (1) is used with an excimer laser beam with a wavelength of 248nm (KrF), 193nm (ArF), 157nm (F2), etc., excellent optical characteristics in reflectance anti (reflection), polarization characteristics, incident angle dependency, etc. can be obtained. The MgF2 layers (12 and 16) can be produced by a sol/gel method. The optical device can be satisfactorily applied to the projection lens of an aligner whose light source is an excimer laser.</p> |
