Black-out curtain

Details Black-out curtain Black-out curtain

1999-06-04

2001-04-24

Hannaher, Constantine (Department: 2878)

Radiant energy

Infrared-to-visible imaging

C250S338100, C250S472100

Reexamination Certificate

active

06222188

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Technical Field
The invention relates to the field of night vision devices that enable a viewer to observe objects at night or during other low-light conditions. More particularly, this present invention relates to a system to prevent the undesired viewing into an interior space or compartment by an external or outside observer.
2. Background Art
Night vision devices are well known. A common type of a night vision device is based on an image intensification technology and is used to provide soldiers, aviators, and sailors with the ability to view objects at night or during other low light conditions.
A common scenario associated with the use of a night vision device is a soldier using a night viewer, such as a night vision goggle (“NVG”) AN/PVS-7 or others, to observe a battlefield scene at night. If the night-time battlefield scene includes people sitting in a vehicle, it is likely that at some point the vehicle occupants will need light to illuminate their compartment to complete operations. Unless otherwise protected, the light source will cast a glow that is visible to the observer outside the vehicle. To prevent or minimize observation by an “unfriendly” soldier using a NVG, a “blackout mode of operation” has been adopted to counteract the observation advantages that the “unfriendly” NVG equipped soldier may have on the battlefield. Consequently, this scenario has prompted a concern with the tactical risk associated with any lighting used in the night vision goggle (“NVG”) blackout mode of operation.
Internal lighting for vehicles, aircraft, and naval warships is clearly required to permit continued use of the vehicles in battle while in the blackout mode of operation. In response night viewer compatible flashlights have been provided as one source of lighting. Alternatively, IR illuminators have been provided and incorporated into night vision systems equipment. The IR illuminators provide lighting at a frequency that is not normally observable without NVG. In both cases the lighting poses a genuine and significant tactical threat from enemy night vision devices.
A technology solution is needed to provide illumination within a vehicle also eyeing the issue of tactical risk from the enemy use of night vision devices.
While the above cited known solutions introduce a number of noteworthy advances and technological improvements within the art, none completely fulfills the specific objectives achieved by this invention.
DISCLOSURE OF INVENTION
The present invention is a low-cost black-out curtain system for reducing undesired viewing by an external observer through an opening in a barrier or window and into an interior space, such as a crew compartment of an armored vehicle, an aircraft cockpit, or the bridge of a naval warship.
In accordance with the present invention, a filter sheet that transmits Electro-Magnetic (EM) radiation, also generally known as light, is adapted to intercept EM radiation originating in the interior space from exiting the interior space through the opening. The filter sheet suppresses EM radiation below a selected cut-off frequency while passing EM radiation above the selected cut-off frequency.
An internal night viewer is adapted to detect only EM radiation having a frequency above the selected cut-off frequency. An interior illumination source supplies the interior space with EM radiation having a frequency below the selected cut-off frequency. The filter sheet and interior illumination source cooperate to prevent the external observer from viewing a scene in the interior space through the opening, while at the same time allow the observer in the compartment to use the internal night viewer to view outside of the compartment.
These and other objects, advantages and features of this invention will be apparent from the following description taken with reference to the accompanying drawings, wherein is shown the preferred embodiments of the invention.


REFERENCES:
patent: 5608213 (1997-03-01), Pinkus et al.
Night Vision Equipment Company brochure, particularly p. 23, Covert Illuminators, and others for background.

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