ND filter and light quantity diaphragming device including the same
US7388723B2 · kind B2 · utility
Assignee
Inventor
Key dates
| Filing date | Nov 11, 2004 |
| Grant date | Jun 17, 2008 |
| Priority date | — |
| Expiry date | Sep 3, 2025 |
Classification
- Technology area (CPC G)Physics
- CPC primaryG03B7/18
- WIPO fieldOptics
- WIPO sectorInstruments
Abstract
A thin film type ND filter being inexpensive and excelling in durability. There is provided ND filter (0) comprising transparent substrate (1) and, superimposed thereon, light absorption films (3,5) and dielectric films (2,4,6), wherein the light absorption films 3.5 consist of a composition comprising 1 to 30 wt. % of a metal in pure form and 50 wt. % or more of a saturated oxide of the metal with the balance of compounds of the metal containing lower oxides of the metal. Metal raw material of the light absorption films (3,5) is selected from among Ti, Cr, Ni, NiCr, NiFe and NiTi. As for the dielectric films (2,4,6), SiO2 or Al2O3 is used. Function of reflection prevention is imparted by superimposing the light absorption films (3,5) and dielectric films (2,4,6) in predetermined film thicknesses and in predetermined sequence. Alternatively, a reflection prevention layer may be formed on the back of the substrate (1).
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.