WIRED - Super Power Issue - Being Invisible

[Guest guest]

Remember the 20-30 year rule in secret technology...What you hear and read about today was researched and developed 20-30 yearsago. The REAL stuff is 20-30 years ahead of this stuff. And at the ratetechnological evolution of humanity is advancing, 20-30 years may bemeaningless by now.-John NovakChanging Planet----------------WIRED MAGAZINEThe Super Power IssueBeing Invisiblehttp://www.wired.com/wired/archive/11.08/pwr_invisible.htmlThe Antigravity Undergroundhttp://www.wired.com/wired/archive/11.08/pwr_antigravity.htmlA User's Guide to Time Travelhttp://www.wired.com/wired/archive/11.08/pwr_timetravel.html8 Super Powershttp://www.wired.com/wired/archive/11.08/pwr_superpower.html-------Being Invisiblehttp://www.wired.com/wired/archive/11.08/pwr_invisible.htmlNext-gen optical camouflage is busting out of defense labs and into thestreet. This is technology you have to see to believe.By Wil McCarthyInvisibility has been on humanity's wish list at least since Amon-Ra, adiety who could disappear and reappear at will, joined the Egyptian pantheonin 2008 BC. With recent advances in optics and computing, however, thiselusive goal is no longer purely imaginary. Last spring, Susumu Tachi, anengineering professor at the University of Tokyo, demonstrated a crudeinvisibility cloak. Through the clever application of some dirt-cheaptechnology, the Japanese inventor has brought personal invisibility a stepcloser to reality.Tachi's cloak - a shiny raincoat that serves as a movie screen, showingimagery from a video camera positioned behind the wearer - is more gimmickthan practical prototype. Nonetheless, from the right angle and undercontrolled circumstances, it does make a sort of ghost of the wearer. And,unlike traditional camouflage, it's most effective when either the wearer orthe background is moving (but not both). You don't need a university lab tocheck it out: Stick a webcam on your back and hold your laptop in front ofyou, screen facing out. Your friends will see right through you. It's agreat party trick.Of course, such demonstrations aren't going to fool anyone for more than afraction of a second. Where is Harry Potter's cloak, wrapped around thestudent wizard as he wanders the halls of Hogwarts undetected? What aboutJames Bond's disappearing Aston-Martin in Die Another Day? Theextraterrestrial camouflage suit in the 1987 movie Predator? Wonder Woman'ssee-through Atlantean jet? It's not difficult to imagine a better systemthan Tachi's. In fact, invisibility that would satisfy any wizard - not tomention any spy, thief, or soldier - is closer than you might think.US Defense Department press releases citing "adaptive,advanced," and"active" camouflage suggest that the government is working on devices likethis. If so, it's keeping them under wraps. However, NASA's Jet PropulsionLaboratory has published a preliminary design for an invisible vehicle, andbattalions of armchair engineers have weighed in with gusto on newsgroupsand blogs. As it happens, most of the schemes that have been advancedoverlook the complexities of the problem. Invisibility isn't a simple matterof sensors that read the light beams on one side of an object and LEDs orLCDs that reproduce those beams on the other. In fact, such a system wouldwork about as well as the laptop party trick with the webcam's lens removed:Objects right up against the sensors would produce blurry images on thedisplay, but a few centimeters away they'd disintegrate into a featurelessgray haze.A real invisibility cloak, if it's going to dupe anyone who might see it,needs to represent the scene behind its wearer accurately from any angle.Moreover, since any number of people might be looking through it at anygiven moment, it has to reproduce the background from all angles at once.That is, it has to project a separate image of its surroundings for everypossible perspective.Impossible? No, just difficult. Rather than one video camera, we'll need atleast six stereoscopic pairs (facing forward, backward, right, left, upward,and downward) - enough to capture the surroundings in all directions. Thecameras will transmit images to a dense array of display elements, eachcapable of aiming thousands of light beams on their own individualtrajectories. And what imagery will these elements project? A virtual scenederived from the cameras' views, making it possible to synthesize variousperspectives. Of course, keeping this scene updated and projectedrealistically onto the cloak's display fabric will require fancy softwareand a serious wearable computer.Many of the tech hurdles have been overcome already. Off-the-shelf miniaturecolor cameras can serve as suitable light sensors. As for the display, toremain unseen at a Potteresque distance of, say, 2 meters, the resolutionneed not be much finer than the granularity of human vision at that distance(about 289 pixels per square centimeter). LEDs this size are readilyavailable. Likewise, color isn't a problem - 16-bit displays are common andought to suffice.But it will take more than off-the-shelf parts to make the cloak's imagebright enough to blend in with the daytime sky. If the effect is to work inall lighting conditions, the display must be able to reproduce anything fromthe faintest flicker of color perceptible to the human eye (1 milliwatt persquare meter) to the glow of the open sky (150 watts per square meter).Actually, the problem is worse than that: According to Rich Gossweiler at HPLabs, the sun is 230,000 times more intense than the sky surrounding it. Ifwe want the cloak to be able to pass in front of the sun without lookinghazy or casting shadows, we'll need to make it equally bright. Of course,this would put severe demands on the display technology - LEDs just ain'tthat brilliant - and it would increase battery size or shrink battery lifeaccordingly. So let's ignore the sun and take our chances. An average TVscreen looks blank in full daylight, so we'll need something brighter, morealong the lines of a traffic light.Response time is also tricky. Like a TV screen, the cloak's display must beable to update faster than the eye's ability to perceive flickering. It hasto register motion in real time without the blurring, ghosting, smearing,and judder that plague today's low-end monitors. A laptop LCD screen isn'tgoing to cut it. A lattice of superbright LED microarrays probably will.The real challenge, though, is turning the video images into a realisticpicture. The view from a pair of cameras strapped to your body is differentfrom the perspective of an observer even a short distance away. The observercan see things the cameras can't, thanks to parallax - the way the angleschange with the distance.Imagine a life-size photograph of a wagon as seen from 20 feet away. Theview of this photo from an additional 20 feet away is about the same as anaked-eye view of the real wagon from 40 feet away. It doesn't satisfy depthperception but will trick a casual glance. But step back 10 more feet, andsuddenly the edges don't match anymore; objects behind the wagon have aperfectly rectangular discontinuity around them. It's painfully clear thatyou're looking at a picture.The solution? Create a synthetic image based on a 3-D model of the world.It's probably impractical to map real-world locations ahead of time, so thisvirtual scene will have to be constructed on the fly based on data from thecameras. The stereoscopic pairs allow the system to triangulate the locationof every pixel in its sight, as well as detect color and brightness.Anything out of the cameras' view will appear as a blank area, but as thecameras move, they'll eventually see enough to build a model of the entiresurrounding environment. To turn the model into a picture, the system willneed to calculate the paths that a light beam can take through the scene onits way to the observer's eye. This is known as ray-traced rendering, andit's not trivial.Especially thorny is how to cover the cloak with photorealistic syntheticimagery in a way that will fool observers from any angle. Standard displays(even flexible ones) are only intended for straight-on viewing. Aninvisibility cloak's pixels must spread their light in all directions, sothe edges look as good and as realistic as the center. Even then, you'd havean image that looked pretty good from the one angle at which everythinglined up with the background, but lousy and strange from anywhere else. Thecloaked alien in Predator, for instance, is pretty darned invisible standingstill in a gloomy jungle, but running through a well-lit area, he betrays aclear case of both parallax error and edge-color error. Harry Potter, on theother hand, walks effortlessly among peers and professors, undetected aslong as he doesn't breathe too loudly.If that's what we're after, our display will have to be an array ofhemispherical lenses, each with a tiny 180 x 180-pixel videoscreen behindit. These fish-eyes - hyperpixels, if you like - will send custom-coloredlight beams to every degree of arc, allowing for up to 32,400 differentviewing angles. Paired with image-warping software that coordinates anddistributes all the different views, this is probably sufficient to trickthe eye in most circumstances.Now we just need to fit 289 hyperpixels into a square centimeter, along withsensors that track the position and orientation of each one. Multiply by 4square meters of fabric, and add, oh, a wee bit of computing power.How much computing power? Overall, our display has something like 375billion pixels (32,400 per fish-eye times 11.6 million fish-eyes), or theequivalent of 286,000 SVGA monitors. Rendering a decent image generallyrequires at least 17 traced rays per pixel. However, even at the lowly rateof 1 ray per pixel, with 60 refreshes a second, the cloak will require a CPUrunning at 10 billion GHz. Add image capture, stereo vision, 3-D scenemanipulation, image warping, and correction for deformations of the cloak,and we'll easily double that burden. Even if clever software tricks canreduce the computing load by a factor of 100 million, we'll still need astack of a hundred 2-GHz Pentium motherboards.And these computers will require electrical power - around 8 to 10 kilowattstotal, enough to run six heavy-duty hair dryers. Thus, a superpowerful,hyperefficient substitute would be really helpful. For the sake of argument,let's say that sometime in the next couple of decades, we have a computermighty enough to tackle this task while drawing the same 100 watts that ahigh-end laptop does today. (If we're willing to accept Predator-levelinvisibility, Moore's law coupled with advanced graphics processing mightmake that possible within a decade.) The display itself will need power aswell; even at 100 percent efficiency (no waste heat), it will draw at least600 watts in full daylight (that's 150 watts per square meter to match thesky times 4 square meters of hyperpixelated fabric). At 12 volts DC, thenorm for digital video systems, this level of power consumption will depletea 2.5 kilogram, 20 amp-hour lithium-ion battery in just 24 minutes. For longdaylight strolls through enemy territory we'll need a lighter, strongerbattery.Even with all this firepower, we'll never entirely avoid blank spots andmisplaced pixels. Visual artifacts and anomalies will occur when a distantobserver sees an object through the cloak that has never been in direct viewof any of its cameras (imagine a highly dynamic environment like abattlefield, where an object can enter and exit the scene before the camerashave had a chance to process it fully). Also, one camera may see a pixelthat others can't, resulting in points of known color but unknown distance.Highly fractal objects like trees may be difficult to reproduce by anymethod, whereas indoor and urban environments will be relatively error-free.Notably, nothing we've discussed so far can mask the wearer's heatsignature, and, in fact, the cloak is bound to generate substantial heat ofits own. Harry Potter would stand out like a bonfire to even a cheapiethermal imaging system, and heat pumps and thermoelectric materials willsimply add to the problem. If Harry can stand the weight penalty, a cylinderof compressed or liquefied air that slowly bleeds pressure can cool thegarment and its wearer the way a spray can chills your hand.Beyond that, all I can say is that a holographic display could substantiallyreduce the computing load and eliminate the need for fish-eye optics.There's no need to simulate 3-D if your display can show it naturally.Today's videoscreens don't have the resolution to display holograms, butit's likely that arrays of quantum dots - up to 1,000 times smaller than thegrain of film used to capture holographic images - one day will display verybright, full-color, full-motion holograms on a flexible surface.Until engineers find a way around these obstacles, true invisibility willremain just out of reach. So relax: The men in black aren't leaning overyour shoulder as you read this. Still, the tech is physically possible andlikely on its way. As is the obvious countermeasure: a balloon full ofscreaming yellow paint.********If this email is cut short, changingplanet/messagesYou can help us make a difference. Click here for details:http://changingplanet.supremalex.org/help.htmChanging Planet News - Where Ethics, Science and Spirituality BlendCOLLECTIVE CONSCIOUSNESS PROJECT: If this email sparked emotions in you, positive or negative, please pray, meditate, visualize or concentrate on the best possible outcome for Humanity and Earth for AT LEAST 10 seconds. On the web at http://changingplanet.supremalex.org