| 摘要 |
<P>PROBLEM TO BE SOLVED: To reduce spectral reflectance in a whole visible wavelength region and to reduce occurrence of deficiencies of an image such as flare and ghost. <P>SOLUTION: A nonreflective cyclic layer 23 based on a large number of minute rugged cyclic structures 21 is formed on a substrate 11 and a neutral density film 15 is formed on another surface of the substrate 11 by a vacuum deposition method to improve antireflection function. Among light incident on a neutral density filter, spectral reflectance at a boundary between atmospheric air and the neutral density film 15 and at a boundary between the neutral density film 15 and the substrate 11 are suppressed low by a MgF<SB>2</SB>film of the laminated neutral density film 15. Reflectance at a boundary between the substrate 11 and the atmospheric air is reduced by the nonreflective cycle layer 23. <P>COPYRIGHT: (C)2008,JPO&INPIT |
