Narrow band and wide angle hemispherical interference optical filter
US4851664A · kind A · utility
69Cited by
9References
7Claims
0Family size
Assignee
Inventor
Key dates
| Filing date | Jun 27, 1988 |
| Grant date | Jul 25, 1989 |
| Priority date | — |
| Expiry date | Jun 27, 2008 |
Classification
- Technology area (CPC G)Physics
- CPC primaryG01J2003/1226
- WIPO fieldMeasurement
- WIPO sectorInstruments
Abstract
An optical interference filter has narrow linewidth and wide acceptance ae and includes a hemisphere coated to provide a narrow bandpass filter at a desired wavelength at normal incidence while other wavelengths at normal incidence are absorbed or reflected. A photodetector placed at the center of the hemisphere detects the desired wavelength only. Other wavelengths that are shorter than the wavelength of the filter are transmitted through the filter to be absorbed by a black absorbing surface around the photodetector. Thus, only the frequency of interest at normal incidence provides a representative signal at the detector.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.