Randomized circular grids for low-scatter EM shield

• US 20100180428A1
• Filed: 12/16/2009
• Published: 07/22/2010
• Est. Priority Date: 12/16/2008
• Status: Active Grant

• Current Assignee: Lockheed Martin Corporation (Martin Marietta Corporation)
• Original Assignee: Lockheed Martin Corporation (Martin Marietta Corporation)
• Inventors: Hines, Leslie D., Jones, Michael I.
• Granted Patent: US 8,361,540 B2
• Time in Patent Office: Days
• US Class Current: 29/592.100
• CPC Class Codes: B05D 5/12 to obtain a coating with specific electrical properties
• CPC Class Codes: B32B 2038/0092 Metallizing
• CPC Class Codes: C23C 28/02 only coatings only including layers of metallic material
• CPC Class Codes: H05K 9/0094 being light-transmitting, e.g. transparent, translucent
• CPC Class Codes: Y10T 156/1089 of discrete laminae to single face of additional lamina
• CPC Class Codes: Y10T 29/49002 Electrical device making
• CPC Class Codes: Y10T 428/24479 including variation in thickness
• CPC Class Codes: Y10T 428/24612 Composite web or sheet
• CPC Class Codes: Y10T 428/24917 including metal layer

Abstract

A randomized elliptical grid disposed on a sensor window for electro-magnetic and/or radio-frequency shielding of sensors, and a method of applying same. Grids may be made of electrically conductive or resistive material and may include elliptical or circular shapes. The shapes are in physical contact with each-other and preferably do not contain straight lines to reduce detection artifacts caused by the coating. Grid element shape, size, orientation, and grid pattern density may be randomized or varied across a sensor window.

Claims

1. A metallization coating for a sensor window, the coating comprising:

a randomized elliptical grid pattern, the pattern including a plurality of randomly distributed elliptical shapes arranged such that the elliptical shapes disposed on the sensor window are physically connected to each-other as a result of direct shape-to-shape contact or overlap; and

where the elliptical shapes are hollow to allow for transmission of electro-optical radiation through the sensor window.

2. The coating of claim 1, wherein the randomized elliptical grid pattern is made of an electrically conductive material.

3. The coating of claim 1, wherein the randomized elliptical grid pattern is made of an electrically resistive material.

4. The coating of claim 1, where each elliptical shape has a 1-2 micron deposition thickness and the elliptical shapes have an average major axis width of 10 microns.

5. The coating of claim 1, where pattern density, which is a ratio of shapes per unit of sensor window area, increases toward an edge of the sensor window.

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

a light-absorbing surface binder layer; and

a primer layer, disposed on top of the binder layer, where the primer layer improves adhesion between the randomized elliptical grid pattern and the binder layer; and

where the randomized elliptical grid pattern is disposed on top of the primer layer.

7. The coating of claim 1, wherein the randomized elliptical grid pattern is radio-frequency (RF) resonant.

8. The coating of claim 1, where rotational orientation of at least one of the elliptical shapes with respect to the sensor window is randomized.

9. The coating of claim 1, where a size of the major and minor axes of at least one of the elliptical shapes is randomized.

10. The coating of claim 9, where at least one the elliptical shapes has major and minor axes of equal size.

11. The coating of claim 1, where the elliptical shapes are electrically connected.

12. The coating of claim 1, where the elliptical shapes are distributed on the sensor window according to a normal probability distribution.

13. The coating of claim 10, where the elliptical shapes are circles.

14. The coating of claim 11, where at least one of the elliptical shapes is electrically connected to a window frame encompassing the sensor window.

15. The coating of claim 1, where each of the elliptical shapes is physically connected to at least one other elliptical shape.

16. The coating of claim 11, where each of the elliptical shapes is electrically connected to at least one other elliptical shape.

17. The coating of claim 1, where the coating is spoke-free.

18. The coating of claim 1, where the grid pattern is a radio-frequency (RF) absorptive randomized elliptical mesh with ellipses arranged in electrically isolated RF-resonant patterns.

19. A method of electromagnetically shielding a sensor window with a metallization coating, the method comprising:

providing a randomized elliptical grid pattern having a plurality of randomly distributed elliptical shapes, where providing includes arranging the elliptical shapes on the sensor window such that the elliptical shapes are physically connected to each-other as a result of direct shape-to-shape contact or overlap.

20. The method of claim 19, where arranging includes increasing a pattern density, which is a ratio of elliptical shapes per unit of sensor window area, towards an edge of the sensor window.

21. The method of claim 19, where arranging further includes:

first providing a light-absorbing surface binder layer;

second providing a primer layer on top of the binder layer, where the primer layer improves adhesion between the randomized elliptical grid pattern and the binder layer; and

providing the randomized elliptical grid pattern on the primer layer.

22. The method of claim 19, where said arranging includes permitting effective transmission of electro-optical radiation through the sensor window while shielding a sensor behind the sensor window from radio-frequency or electro-magnetic radiation.

23. The method of claim 19, where arranging includes distributing the elliptical shapes according to a uniform probability distribution.

24. The method of claim 19, where arranging includes randomizing sizes of major and minor axes of at least one of the elliptical shapes.

25. The method of claim 19, where arranging includes electrically connecting the elliptical shapes to each-other.

26. The method of claim 19, where arranging includes randomizing a rotational orientation of at least one of the elliptical shapes with respect to the sensor window.

27. The method of claim 19, where providing a randomized elliptical grid includes providing a randomized elliptical grid where at least one of the elliptical shapes has major and minor axes of equal size.

28. The method of claim 19, where arranging includes randomizing a thickness of the elliptical shapes.

29. The method of claim 19, where providing an randomized elliptical grid includes providing a randomized elliptical grid where all the elliptical shapes are circles.

30. The method of claim 25, where arranging further includes electrically connecting at least one of the elliptical shapes to a window frame encompassing the sensor window.

31. The method of claim 19, where arranging includes physically connecting each elliptical shape to at least one other elliptical shape.

32. The method of claim 25, where arranging further includes electrically connecting each elliptical shape to at least one other elliptical shape.

33. The method of claim 19, where arranging includes selecting elliptical shapes and shape distributions such that the randomized elliptical grid is spoke-free.

34. The method of claim 19, where providing further includes depositing each elliptical shape such that is has 1-2 micron deposition thickness and such that the elliptical shapes have an average major axis width of 10 microns.