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" In 1897, H. G. Wells imagined a hellish existence for a young scientist who managed to find the key to invisibility, but not how to reverse it. More recently, in the movie Predator, a big green extraterrestrial hunts humans while concealed in blurry, almost invisible battle armor. Harry Potter goes even further, disappearing completely beneath his wizard&amp;#039;s cloak. Now the invisibility technology once reserved for sci-fi mags, movie theaters and comic books is quietly sneaking up on us. While hiding from your little brother is fun, the ability to hide from bullets can save your life. To that end, adaptive camouflage for personnel and vehicles has become a military priority. Traditional camouflage\u2014common to the animal kingdom\u2014uses a static color and shape pattern to blend in visually with the background. Researchers at NASA&amp;#039;s Jet Propulsion Laboratory have defined adaptive camouflage as a form of camouflage that actively changes to best match the environment. The key idea is to wrap yourself in real-time images of the surrounding environment\u2014sort of like wearing a flexible television screen. You can get started right now: Aim a webcam backward over your shoulder and stand behind the computer monitor. Because the computer screen is displaying an image of what&amp;#039;s behind you, anyone standing directly in front of you will see a rectangular hole where your totally ripped abs should be. Then imagine crouching inside a box made of flat-panel monitors with cameras pointing in every direction. Now imagine the U.S. military imagining a tank inside that box. The basic idea is sound, but don&amp;#039;t sneak into the womens&amp;#039; locker room quite yet\u2014the edges of the computer monitor are still visible and each view looks convincing from only one perspective. Researchers from Tokyo University in Japan have developed an early prototype of adaptive camouflage. Their approach is simple: A video camera on the back of a white rain jacket collects an image that is projected onto the front of the jacket as if it were a movie screen. The jacket is made of a retroreflective material that clearly shows the projected image. Although casually glancing at the jacket reveals a ghostly image of whatever is behind it, this approach is little more than a parlor trick; it requires a separate projector and only works from front-on (see photo above, courtesy of Tachi Laboratory/Tokyo University).  The real problem is to make adaptive camouflage show the right image from every angle at once, not just from the front. This is a challenge, but it isn&amp;#039;t impossible. Remember those cheap holographic stickers\u2014the ones that show a different image depending on how much they are tilted? Using a similar principle, it is theoretically possible to go invisible. First, the system needs at least six stereoscopic pairs of cameras (that&amp;#039;s twelve in all) and they must be pointed in every direction. This will capture a complete image of the surroundings. Second, a dense array of display elements is needed, each capable of aiming light beams on their own individual trajectories. The refresh rate must be faster than the human eye in order to avoid creating a flickering effect. Anyone who plays video games knows that a high frame rate is tough to maintain when there is a lot of motion; the entire screen must refresh quickly without blurring, ghosting, smearing or juddering. Finally, a hardworkin&amp;#039; wearable computer has to calculate the virtual scene to send to each element of the display. All the above technology then has to be stitched together into a wacky robe covered with moons and stars. Invisibility applications extend past the battlefield and beyond the womens&amp;#039; locker room: Surgeons could see through their own fingers during operations, pilots could orient themselves by seeing through the airplane floor, and you could finally get a decent window in your basement apartment. Unfortunately, current technology only works at short distances, in dim places and at select viewing angles. The only way to transcend these boundaries is to develop faster processors, brighter LEDs and more-flexible display elements. Alternately, you could join a team of battle-hardened jungle commandos and track down and capture a Predator alien, being sure to remove its quasi-invisible battle gear before it has a chance to self-destruct. "^^<http://www.w3.org/2001/XMLSchema#string>
<http://www.popularmechanics.com/technology/gadgets/a1621/4216202/>