Optical transparency having an electromagnetic pulse shield

• US 4,932,755 A
• Filed: 10/12/1988
• Issued: 06/12/1990
• Est. Priority Date: 10/12/1988
• Status: Expired due to Fees

• Current Assignee: Pilkington Aerospace, Inc. (Melrose Industries Plc)
• Original Assignee: Swedlow Incorporated
• Inventors: Dewald, Duane S., Holdridge, David W.
• Primary Examiner(s): Arnold, Bruce Y.
• Assistant Examiner(s): Ben, Loha
• Application Number:
  US07/257,458
• Time in Patent Office: 608 Days
• Field of Search: 350/276 R, 350/276 SL, 350/321, 350/322, 350/164, 358/253, 358/252, 174/35 MS, 174/36, 324/156
• US Class Current: 359/896
• CPC Class Codes: B64C 1/1476 Canopies; Windscreens or similar transparent elements
• CPC Class Codes: H01Q 15/0013 said selective devices working as frequency-selective reflecting surfaces, e.g. FSS, dichroic plates, surfaces being partly transmissive and reflective

Abstract

An optical transparency adapted to substantially attenuate electromagnetic pulses incident on it, yet transmit visible light with minimal distraction being caused by Fraunhofer diffraction. The transparency includes a transparent sheet and a laminated, electrically-conductive grid that defines a densely-packed array of apertures. Each aperture is a modified polygon having multiple curved sides, such that visible light from a remote point source of light is diffracted by the curved sides of each aperture over multiple, diverging, fan-like areas and minimal distraction to a person viewing through the transparency is thereby provided.

Claims

1. An optical transparency adapted to attenuate an impinging electromagnetic pulse, yet transmit visible light with negligible distraction being caused by Fraunhofer diffraction, the optical transparency comprising:

a transparent sheet; and

an electrically-conductive grid laminated with the transparent sheet and including electrical conductors of substantially uniform width that define a densely-packed array of apertures, each aperture being a modified polygon having multiple curved sides;

wherein the electrically-conductive grid substantially attenuates any electromagnetic pulse impinging on the transparency, yet transmits a substantial proportion of incident visible light, with negligible distraction being caused by Fraunhofer diffraction.

2. An optical transparency as defined in claim 1, wherein the apertures defined by the electrically-conductive grid all have three sides.

3. An optical transparency as defined in claim 1, wherein the apertures defined by the electrically-conductive grid all have four sides.

4. An optical transparency as defined in claim 1, wherein the apertures defined by the electrically-conductive grid all have six sides and are substantially identical in shape and area.

5. An optical transparency as defined in claim 4, wherein the apertures defined by the electrically-conductive grid all have sides that are alternatively convex and concave.

6. An optical transparency as defined in claim 1, wherein the apertures defined by the electrically-conductive grid all have substantially the same shape and area.

7. An optical transparency as defined in claim 1, wherein the apertures defined by the electrically-conductive grid all have multiple curved sides, including just a single arc.

8. An optical transparency as defined in claim 1, wherein the electrically-conductive grid is sized to transmit through its apertures at least about 95 percent of visible light incident on the grid.

9. For use in laminated aircraft transparency, an electromagnetic pulse shield that transmits visible light with negligible distraction being caused by Fraunhofer diffraction, the electromagnetic pulse shield comprising:

an electrically-conductive grid including electrical conductors of substantially uniform width that define a densely-packed array of apertures, each aperture being a polygon modified to have multiple curved sides;

wherein the electrically-conductive grid substantially attenuates any electromagnetic pulse impinging on the transparency, yet transmits a substantial proportion of incident visible light, with negligible distraction being caused by Fraunhofer diffraction.

10. An electromagnetic pulse shield as defined in claim 9, wherein the apertures defined by the electrically-conductive grid all have three sides.

11. An electromagnetic pulse shield as defined in claim 9, wherein the apertures defined by the electrically-conductive grid all have four sides.

12. An electromagnetic pulse shield as defined in claim 9, wherein the apertures defined by the electrically-conductive grid all have six sides and are substantially identical in shape and area.

13. An electromagnetic pulse shield as defined in claim 12, wherein the apertures defined by the electrically-conductive grid all have sides that are alternatively convex and concave.

14. An electromagnetic pulse shield as defined in claim 9, wherein the apertures defined by the electrically-conductive grid all have substantially the same shape and area.

15. An electromagnetic pulse shield as defined in claim 9, wherein the apertures defined by the electrically-conductive grid all have multiple curved sides, each including just a single arc.

16. An electromagnetic pulse shield as defined in claim 9, wherein the electrically-conductive grid is sized to transmit through its apertures at least about 95 percent of visible light incident on the grid.