Documents / Report
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.
“The Advance”9 pages
UNCLASSIFIED/ ,'P81l 8PPll!l*L tl!II!! t!IHLY Figure 8. Fermat's Principle. The grey level indicates the refractive index. In traveling from A to B, light follows the path that takes the shortest time, traveling, if possible, through regions of low index. The bending of light in materials or, equivalently, the change of the spatial geometry by optical materials is the cause of most optical illusions. For instance, the figure used to illustrate Fermat's Principle shows the path of light in a mirage. The air above a hot surface, hot tarmac, or desert sand is hotter than the air farther above. As hot air is thinner than cooler air, the refractive index is lower above the hot surface. Light rays are bent upwards, conjuring up images of water in the distance that, in reality, are images of the sky. Such optical geometries may also be employed for creating the ultimate illusion: invisibility. Imagine an optical material changing the geometry of space, as shown in Figure 9 below. 7 UNCLASSIFIED/ ,'P81l err1e1-.t tl!il! 8111:'I'
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Report, from the dia collection. The PDF is mirrored here; the original link is above. 29 pages are in the text index: search them above, or from the library's search.