Surveillance window

• US 20030095331A1
• Filed: 05/28/2002
• Published: 05/22/2003
• Est. Priority Date: 11/21/2001
• Status: Active Grant

• Current Assignee: Thales Avionics Incorporated (Thales SA)
• Original Assignee: Thales Avionics In-Flight Systems LLC (Thales SA)
• Inventors: Grich, Richard, Bengoechea, Xavier, Finizio, Francesco
• Granted Patent: US 7,187,498 B2
• Time in Patent Office: Days
• US Class Current: 359/489.07
• CPC Class Codes: G02B 27/28 for polarising used in stereoscopes G02B30/25
• CPC Class Codes: G08B 13/19626 optical details, e.g. lenses, mirrors or multiple lenses

Abstract

A surveillance window comprising at least one set of linear polarizer and quarter-waveplate and a reflecting surface is presented. The surveillance window appears dull and opaque to a subject, while allowing a relatively high percentage of light to be transmitted to an observer. Various enhancements including an illuminator and detector, camouflaging, fire resistance, and improvements to the opacity are also described.

Claims

1. A window for covert surveillance, said window comprising:

a circularly polarizing set, comprising;

a linear polarizer on a subject side,

a quarter-waveplate on an observer side,

an optically clear material for joining the linear polarizer to the quarter-waveplate; and

a reflecting surface on the observer side of the circularly polarizing set.

2. The window of claim 1 further comprising:

an additional circularly polarizing set disposed between the circularly polarizing set and the reflecting surface.

3. The window of claim 1, the window further comprising:

a protective transparent covering for the subject side of the window.

4. The window of claim 1, the window further comprising:

a protective transparent coating on the subject side of the window.

5. The window of claim 1, the window further comprising:

a two-way mirror on the subject side of the set.

6. The window of claim 1, the window further comprising:

a two-way mirror on the observer side of the set.

7. The window of claim 1, the window further comprising:

a neutral density filter on the subject side of the set.

8. The window of claim 1, the window further comprising:

a neutral density filter on the observer side of the set.

9. The window of claim 1, the window further comprising:

camouflage graphics for the subject side of the window.

10. A method for covert surveillance, the method comprising the steps of:

polarizing an incident light along one axis in order to produce linearly polarized light,

converting the linearly polarized light into circularly polarized light, and

reflecting the circularly polarized light.

11. The method of claim 10, the method further comprising the step of:

protecting an exterior with a transparent coating.

12. The method of claim 10, the method further comprising the step of:

protecting an exterior with a transparent covering.

13. The method of claim 10, the method further comprising the step of:

filtering light with a uniformly absorbing filter.

14. The method of claim 10, the method further comprising the step of:

camouflaging an exterior with camouflaging graphics.

15. The method of claim 10, the method further comprising the steps of:

illuminating a subject with a wavelength of light not detectable by that subject; and

detecting the subject with a detector suitable for use with the wavelength of light.