Absorption type multi-layer film ND filter
US7239464B2 · kind B2 · utility
6Cited by
6References
11Claims
0Family size
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Key dates
| Filing date | Jul 13, 2005 |
| Grant date | Jul 3, 2007 |
| Priority date | — |
| Expiry date | Jul 13, 2025 |
Classification
- Technology area (CPC G)Physics
- CPC primaryG02B5/22
- WIPO fieldOptics
- WIPO sectorInstruments
Abstract
An absorption type multi-layer film ND filter having a substrate and an optical multi-layer member consisting essentially of metal layers each composed chiefly of nickel (Ni) and dielectric layers each formed of any one of SiO2, Al2O3 and a mixture of these; the layers being alternately layered on the substrate. An Ni type metallic material having a small wavelength dependence of transmittance in the visible spectral range is used in the metal layers serving as light attenuation layers, and this enables materialization of an ND filter which can attain transmittance attenuation that is flat for wavelengths.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.