ND filter having composite PVD film of metal and its oxide
US6671109B2 · kind B2 · utility
Assignee
Inventor
Key dates
| Filing date | Jul 25, 2002 |
| Grant date | Dec 30, 2003 |
| Priority date | — |
| Expiry date | Jul 25, 2022 |
Classification
- Technology area (CPC G)Physics
- CPC primaryG02B5/285
- WIPO fieldOptics
- WIPO sectorInstruments
Abstract
A neutral density filter has a multi-layer structure of thin films laminated on a substrate made of a transparent material. The multi-layer structure contains a transparent thin film composed of a dielectric material effective to transmit the incident light and a non-transparent thin film effective to absorb a part of the incident light. The non-transparent thin film is composed of a metal material which is deposited by vacuum evaporation. The non-transparent thin film contains an oxide of the metal material, which is generated during the vacuum evaporation by introducing a gas containing an oxygen while maintaining a vacuum degree in a range of 1×10−3Pa to 1×10−2Pa, and which is deposited concurrently with the metal material.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.