Patent ID: 6222188
Filing Date: 2001-04-24
Classification: G02B

Abstract:
A blackout curtain system for reducing undesired viewing by an external observer through an opening in a barrier into an interior space, the invention comprising:a filter sheet transmitting Electro-Magnetic (EM) radiation therethrough, and adapted to intercept EM radiation originating in the interior space from exiting the interior space through the opening;said filter sheet suppresses EM radiation having a frequency below a selected cut-off frequency, and passes EM radiation above the selected cut-off frequency;an internal night vision device for viewing from within the interior space adapted to detect EM radiation having a frequency above the selected cut-off frequency; and,an interior illumination source adapted to supply EM radiation having a frequency below the selected cut-off frequency into the interior space;whereby the filter sheet and interior illumination source prevents the external observer from viewing a scene in the interior space through the opening.