System and Methods for Filtering Electromagnetic Visual, and Minimizing Acoustic Transmissions
A combination of filters for filtering selected wavelengths of electromagnetic radiation is provided on a transparent substrate such as a plastic film or glazing of a window. The combination of filters prevents or attenuates the passage of wavelengths through the substrate which would pose a security risk. The combination of filters is useful to prevent unauthorized data collection and information exchange from or within buildings or otherwise prevent such unauthorized data collection and information exchange from, for example, computer monitors or screens, personal digital assistance, and local area networks. The substrate with the combination of filters may be in the form of a bag or a tent.
1 . A transparent anti-surveillance security apparatus for preventing or attenuating the passage therethrough of electromagnetic wavelengths which pose a security risk; said apparatus comprising a transparent substrate and a combination of filters connected to said substrate, said combination of filters comprising a first light filter, wherein said first light filter is:
a light filter (a) comprising a heat reflecting layer and an electrically conductive metal layer, or
a light filter (b) having an IR transmission at wavelengths between 780 nm and 2500 nm of no more than 50%, or
a light filter (c) which has a sheet resistance of less than 4 ohms per square and comprises a sequence of layers:
dielectric layer/IR reflecting metal layer/dielectric layer; or
IR reflecting metal layer/dielectric layer/IR reflecting metal layer
wherein said sequence of layers is coated onto said substrate or onto a transparent plastic sheet; said apparatus optionally further including an IR absorbing filter; said combination of filters being configured to prevent or attenuate the passage of said electromagnetic wavelengths through said apparatus and said dielectric of each dielectric layer has an index of refraction in the range of about 1.35 to 2.6.
2 . A transparent anti-surveillance security apparatus for preventing or attenuating the passage therethrough of electromagnetic wavelengths which pose a security risk; said apparatus comprising a transparent substrate and a combination of filters connected to said substrate, said combination of filters comprising a first light filter which is not grounded, wherein said first light filter comprising:
a light filter (a) comprising a heat reflecting layer and an electrically conductive metal layer, or
a light filter (b) having an IR transmission at wavelengths between 780 nm and 2500 nm of no more than 50%, or
a light filter (c) which has a sheet resistance of less than 4 ohms per square and comprises a sequence of layers:
dielectric layer/IR reflecting metal layer/dielectric layer; or
IR reflecting metal layer/dielectric layer/IR reflecting metal layer
wherein said sequence of layers is coated onto said substrate or onto a transparent plastic sheet; said apparatus optionally further including an IR absorbing filter; said combination of filters being configured to prevent or attenuate the passage of said electromagnetic wavelengths through said apparatus and said dielectric of each dielectric layer has an index of refraction in the range of about 1.35 to 2.6.
3 . The apparatus of claim 1 , wherein an indirectly connected filter layer is connected to the substrate via the first light filter.
4 . The apparatus of claim 1 , wherein an indirectly connected filter layer is connected to the substrate via the IR absorbing filter.
5 . The apparatus of claim 1 , wherein the IR reflecting metal layer comprises silver, and the thickness of the IR reflecting metal layer is adjusted to achieve the desired ohms per square.
6 . The apparatus of claim 2 , wherein an indirectly connected filter layer is connected to the substrate via the first light filter.
7 . The apparatus of claim 2 , wherein an indirectly connected filter layer is connected to the substrate via the IR absorbing filter.
8 . The apparatus of claim 2 , wherein the IR reflecting metal layer comprises silver, and the thickness of the IR reflecting metal layer is adjusted to achieve the desired ohms per square.