Black-out curtain
US6222188A · kind A · utility
Assignee
Inventor
Key dates
| Filing date | Jun 4, 1999 |
| Grant date | Apr 24, 2001 |
| Priority date | — |
| Expiry date | Jun 4, 2019 |
Classification
- Technology area (CPC G)Physics
- CPC primaryG02B23/12
- WIPO fieldOptics
- WIPO sectorInstruments
Abstract
A black-out curtain system (S) reduces undesired viewing by an external observer (O) through an opening (10) in a barrier (12) into an interior space (14). A filter sheet (16) that transmits Electro-Magnetic (EM) radiation (18) is adapted to intercept EM radiation originating in the interior space (14) from exiting the interior space (14) through the opening (10). The filter sheet (16) suppresses EM radiation below a selected cut-off frequency (C), and passes EM radiation above the selected cut-off frequency. An internal night viewer (20) detects only EM radiation having a frequency above the selected cut-off frequency (C). An interior illumination source (22) supplies the interior space (14) EM radiation having a frequency below the selected cut-off frequency (C).
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.