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Defense Intelligence Reference Document Invisibilty Cloaking Theory And Experiments

Defense Intelligence Agency · 29 pages · text from the file's own layer

This Defense Intelligence Reference Document, dated 2 March 2010 and produced by the Defense Intelligence Agency under its Advanced Aerospace Weapon System Applications (AAWSA) Program, is a technical survey of invisibility. It covers camouflage, including stealth aircraft and optical camouflage, then transparency, cloaking by coordinate transformation, metamaterials and non-Euclidean broadband cloaking. It concludes that perfect cloaking is impossible but imperfect microwave cloaks are within reach of present technology. Whether cloaking will work at visible wavelengths remains unclear.

  • p. 6 …From the direction and the time delay of the reflected waves, the direction and --:.. distance of…
  • p. 8 …the atoms or molecules of these substances absorb and re-emit light, which takes time. The…
  • p. 11 …According to Fermat's principle, light follows the path that takes the shortest time. In refractive…
  • p. 12 …In traveling from A to B, light follows the path that takes the shortest time, traveling…
  • p. 21 …For light, the wave fronts are the features of oscillations across space and time; by themselves…
  • p. 24 …The sphere is invisible; it shows only as a time delay of the light ray. Although…
  • p. 25 …With sensitive timing or wave-front sensing one could, in principle, detect the presence of the…
  • p. 27 …The required optical properties should be calculated in real time, and the material should change accordingly…
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Figure 9. An Optical Material Deforms the Coordinates of Space. A: virtual space, B: real space.
The material acts like a transformation of space. In the device, each point in real space
is put to a new location in a virtual space (outside of the device, space remains the
same). The device creates the illusion that light propagates along straight lines through
the virtual space, whereas in reality it is bent. Suppose the device encloses a hollow
region that is not part of the virtual space or, to be more precise, a region with a
surface that, in virtual space, has become a single point. The red circle in Figure 9B is
reduced to the red dot in Figure 9A. As the hollow region is not part of the virtual space
where light propagates, everything inside it has become invisible. As the coordinates of
virtual space smoothly go over into the coordinates of real space at the outer surface of
the device, light rays are not distorted. Any object inside the cloaking device is hidden,
and so is the act of hiding itself. Moreover, the cloaking device not only would bend
light rays but would modify the entire structure of light waves in such a way that
detecting the hidden object is impossible. Light waves would advance around the
hidden core of the device, engulfing it, as Figure 10 shows. 8
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Report, from the dia collection. The PDF is mirrored here; the original link is under it. 29 pages are in the text index: search them above, or from the library's search.