Optically transmissive Faraday cage

• US 5,373,102 A
• Filed: 08/19/1993
• Issued: 12/13/1994
• Est. Priority Date: 08/19/1993
• Status: Expired due to Fees

• Current Assignee: United States Of America As Represented By The Secretary Of The Army (Government of the United States of America)
• Original Assignee: The United States Of America As Represented By The Secretary Of The Army
• Inventors: Davenport, Wayne E., Taylor, Travis S., Ehrlich, John J.
• Primary Examiner(s): Picard, Leo P.
• Assistant Examiner(s): Horgan, Christopher
• Application Number:
  US08/108,274
• Time in Patent Office: 481 Days
• Field of Search: 174/35 R, 174/35 MS, 428/34, 428/334, 428/333, 428/458, 428/432, 428/434, 428/192, 428/212-215
• US Class Current: 174/381
• CPC Class Codes: H05K 9/0094 being light-transmitting, e.g. transparent, translucent
• CPC Class Codes: Y10T 428/261 In terms of molecular thickness or light wave length

Abstract

The structure of this invention provides a means for shielding an opticallyensitive detector, device, or components from electromagnetic fields without shielding them from the optical spectra desired to be transmitted. The structure of the invention is in the form of an optically transmissive Faraday cage or box having optically transparent material selected from optical glass and optically transparent plastic which functions as a substrate. The substrate is provided a thin film of predetermined skin depths in the form of a conductive coating selected from silver and a nickel-chromiumiron-manganese-silicon-copper-alloy. The conductive coating is applied in a thickness equivalent to a predetermined number of skin depths in order to attenuate an external electromagnetic field strength to meet the tolerance of the detector, device, or components which are to be shielded.

Claims

1. An optical transmissive shield for an optically sensitive detector or device and components thereof which attenuates an external electromagnetic field while being transmissive to optical signals, said optically transmissive shield comprising:

(i) a transparent box of a predetermined size to meet the physical size requirements of said optically sensitive detector or device and components thereof, said transparent box having external surfaces which function as external substrates for a conducting optically transmissive thin film applied to said external substrates, said transparent box constructed of an optically transparent material selected from the group consisting of glass, acrylic resin, methyl methacrylate, and acrylic sheet;

(ii) a conducting optically transmissive thin film of a nickel-chromium-iron-manganese-silicon-copper-alloy applied in skin depths of one, two or three on said external substrates for shielding said optically sensitive detector or device and components thereof to said external electromagnetic field while allowing optical signals of the spectra of ultraviolet, visible, infrared near, infrared middle, and infrared far to pass, said optical signals having wavelength ranges in microns of 0.02-0.38, 0.397-0.723, 0.750-1.5, 1.5-10, and 10.0-12.0, respectively.

2. The optically transmissive shield as defined in claim 1, wherein said optically transparent material selected is methyl methacrylate and wherein said nickel-chromium-iron-manganese-silicon-copper-alloy is applied in said skin depths of one, two, or three to achieve attenuation of said external electromagnetic field by 87%, 98%, or 99.8%, respectively.