| 摘要 |
<P>PROBLEM TO BE SOLVED: To obtain an ND filter stabilized in spectral characteristics by suppressing changes in spectral characteristics of an optical attenuation film caused by the oxidation of metal or a metal oxide. <P>SOLUTION: The ND filter has an ND film 26 comprising 12 layers in total formed on a transparent substrate 21, the ND film formed by disposing an optical attenuation film comprising alternately deposited dielectric Al<SB>2</SB>O<SB>3</SB>films 22 as first, third, fifth, seventh and ninth layers and light-absorbing Ti<SB>x</SB>O<SB>y</SB>films 23 as second, fourth, sixth, eighth and tenth layers, layering a Si<SB>3</SB>N<SB>4</SB>film 24 that functions as a water vapor barrier layer as an eleventh layer on the Ti<SB>x</SB>O<SB>y</SB>film 23 as the tenth layer, and further forming a MgF<SB>2</SB>film 25 that is an antireflection film as the outermost surface layer. The intrusion of water vapor or the like is prevented by the Si<SB>3</SB>N<SB>4</SB>film 24, and thus, the Ti<SB>x</SB>O<SB>y</SB>films 23 of light-absorbing layers are prevented from be deteriorated. <P>COPYRIGHT: (C)2011,JPO&INPIT |
