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Glass Invisibility Cloak Shields Infrared
An anonymous reader writes with the latest advance in the quest for a cloak of invisibility (Michigan Tech University's press release). We've been following this research as it develops; here are stories from each of the last four years. "Invisibility cloaks are slowly working their way up to shorter wavelengths — starting at millimeter-long microwaves and working their way to the nanometer wavelengths of visible light. EETimes says we are about half way there — micrometer wavelengths — in this story about using chalcogenide glass to create invisibility cloaks in the infrared. Quoting: 'Invisibility cloaks cast in chalcogenide glass can render objects invisible to infrared frequencies of light, according to researchers at Michigan Technological University... Most other demonstrations of invisibility cloaks have used metamaterials composed of free-space split-ring resonators that were constructed from metal printed-circuit board traces surrounded by traditional dielectric material. The Michigan Tech researchers... claim that by substituting nonmetallic glass resonators made from chalcogenide glass, infrared cloaks are possible too...'"
I so totally didn't see this story coming this morning...
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Once you can cloak infrared, then you have a genuine military grade cloak with true stealth capability and applications. Expect most of the real breakthroughs to never see the front page of /. or any other news source. Except maybe Wikileaks.
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Calling these things "invisibility cloaks" is being very, very generous.
They are fundamentally flawed in the specs: percent transmission, angle, bandwidth, and refraction.
They're more of a laboratory curiosity than anything that would fool anybody.
but can't see the story. What gives?
Anything you say will be held against you.
Yes. On a linear scale, we're basically all the way there. So what's you're point?
Seriously, log scales are the better way to measure this sort of thing, not just for convenience. Look at Moore's law.
On the other hand, I'm confused as to why we're only halfway there. Light wavelenghts aren't nanometer in size, they're hundreds of nanometers. Which means that we've gone from 1E-3 m to 1E-6 on our way to 1E-7. In log space, we're 75% of the way there.
Of course it's possible, it's just a question of whether or not we're ever able to do it effectively. For something to be invisible, you have to have the photons divert around it then converge at the other end as if they hadn't just diverted. That would make something invisible, the practice however is not easy by any reasonable stretch of the imagination.
Glass Invisibility Cloak Shields Infrared
You know you've been coding too much when the brain reads that as "noun noun noun noun noun" and throws a parse error expecting a verb...
( Redundancy is ) ^ n
Infrared also poses additional problems above and beyond what you've stated, because the light isn't coming from an external source.
Any hot object is going to radiate infrared radiation. That isn't something external being reflected off of it, that's coming from the surface of the radiating object itself. Infrared sensors work on contrast, so if you've got, say, a skin temperature object like a human being in a room temperature environment, it'll show up. Same applies for a room temperature object in an arctic environment - what matters is contrasting temperatures between the object to hide and the world around it.
So how do you mask this? Okay, you keep the infrared from escaping. Totally stopping it is impossible, but reducing it isn't, and "good enough" if it's reduced to the point where it no longer contrasts with its surroundings. Thing is, radiating heat is one of the ways internally heated objects (like human bodies) cool down, so depending on a number of factors, overheating will be an issue.
But you can lose heat in other ways. Conduction and convection dissipate more heat than radiation, at least in a terrestrial environment (space is another story). Except that the medium you're dumping heat into will itself heat up and start radiating in the IR spectrum, just like your hidden whatever would have. So you've mitigated the problem, but not eliminated it.
Now an important thing to note is that all of this applies to complete invisibility to IR. Partial stealth is another matter. Mitigating the problem is good enough if the intent is to make the job of whoever is looking for you harder. Stealth aircraft aren't invisible either, but are stealthy enough to give them an edge over the competition. OTOH, this pretty much kills any chance of making a Star Trek style cloaking device, especially if you want it to work in space.
Erotic is when you use a feather. Exotic is when you use the whole chicken.
Because a visible house with a completely transparent heat signature isn't going to raise any eyebrows.
To prevent this day from getting worse, I'll just read ERROR as GOOD TH
You're talking about thermal imaging. That's not how IR used for night-vision works. Your IR remote control doesn't shoot a jet of warmth at the TV. It's just a spectrum of light slightly outside of what we see.
Actual IR cameras work so well for finding people because of what's REFLECTING the IR light. Synthetic materials reflect differently to the sorts of things you find in the wild. Additionally IR is useful for marking friendlies in such a way that people without IR gear can't see.
Modern night-vision goggles use a combination of low-light sensitive cameras, IR imagery and image processing to enhance the image. I'm not actually sure if you'll find thermal imaging in use at all for combat situations.
Keeping that in mind, because the images are often of such low quality the concept of bending light around an object- even with large distortion errors - works very well. You're merely adapting the entire cloak to suit the surrounds, which is exactly what modern techniques for hiding from IR cams involves, except you disguise yourself with the surrounding foliage/debris/whatever. Same materials, same colour, same IR reflectivity. Fooling our eyes in daylight is going to be a little harder.
I know it is premature speculation on lab technologies but, well Infra-reds invisibility could mean improved heat isolating glasses windows for buildings. Keep visible light enter the building, let infra-reds refract though the other side and keep inside radiating heat bouncing the glass with perfect reflection. Would be a boon for vehicles where most windows face side to side. Would this be more efficient or combinable with athermic design?
Léa Gris
If this can be made to work at the frequencies used by infrared targeting sensors it could be extremely useful. It doesn't have to 'match' anything. All it has to do is make the platform not emit in the expected direction, but in a direction that will make tracking difficult. Remember that these kind of meta-materials have a negative index of reflection, so they can act like unusual lenses. It doesn't even have to do this for the entire vehicle, just the hot parts used for targeting. For example, this could be a big winner for UAV platforms.
Why is Snark Required?
measure the surrounding background heat levels and *match them*, like a chameleon matches background visual colors
How invisibility cloaks work http://www.howstuffworks.com/invisibility-cloak.htm
Ok, I'm not up on materials science and had to look this up--thought others might be curious, too: chalcogenide glass
You neither block nor reflect, you cause the light to bend around you.
Imagine a smoothly-flowing stream: If you put a rock in it, the flow will be disturbed. If the rock is irregularly shaped, some of the water will "bounce" back(because this is water, and not photons, it will only cause some turbulence, not actually be reflected; but such is the weakness of analogies...). If the rock has a nice, smooth, hydrodynamic sort of shape, the water will part smoothly when it hits the rock and then come back together behind the rock, with minimal disruption to the flow. The rock exists; but for a hypothetical organism that can only detect water currents(say a water bug with sensory hairs, sitting downstream), it will be invisible.
It turns out that, on small scales, under laboratory conditions(and often only in two dimensions), with exotic materials, you can cause photons to "bend around" an object, thus rendering the object effectively invisible. They don't get absorbed, so you can't detect the object by their absence, and they don't get reflected, so you can't see the object, they just take a circuitous path around the object, and continue on their merry way as though nothing was there(though, since a semicircular path is slightly longer than the straight path would have been, I suppose a sufficiently sensitive travel-time comparison system could still detect the cloaked object...)
Where does the heat go?
Have you fscked your local propeller head today?
The only way this will work to evade military grade infra red detection is if 1) you are not moving - people tend to notice a "cold patch" moving against a background - it's almost as good as a hot one; and 2)if you can manage to match the background heat exactly, thus masking your shape. Unfortunately if you're being viewed by something that's moving (like a helicopter or drone), you have no idea at what angle you are being viewed from at any point in time. This complicates matters.
Seven puppies were harmed during the making of this post.
Didn't the mythbusters already prove you can foil a heat-sensing alarm by holding a pane of glass in front of you?