OT Invisibility Cloak

[harry]

[Chris Hogg]

Been around for several years.

[John]

Chris Hogg [e-mail] wrote in news: [e-mail]:

I sometimes find myself wearing one when I go to a bar in a pub.

[whisky-dave]

Interesting as we've been working on a version here, us and another univ, got a $5 million grant over a few years, we've worked out how to do a infra red version, it's just that we havent the current tech to make the 'fabric' according to the researcher I spoke to.

[Brian Gaff (Sofa)]

Yes I can't find my camouflage net either. Brian

[Brian Gaff (Sofa)]

I have the problem in doctors waiting rooms and at reception in hospitals as well. I think what actually happens is because I cannot make eye contact, nobody talks to me, assuming I'm just hanging around for somebody ellse. Need more disability training.... Brian

[Brian Gaff (Sofa)]

Its that negative refractive index which is the issue. Brian

[whisky-dave]

It's not just you, people rarely talk in such situation.

Same as in bus queues on trains or buses and many other situations. And it's not because you are blind it's because you don't matter same as everyone else that's equality.

[whisky-dave]

Something similar it's making 'mirrors' in fabric that can be moved that are as small as the wavelengh of infra red or something like that.

[John]

"Brian Gaff \(Sofa\)" [e-mail]> wrote in news:qqmi58$4ec$ [e-mail]:

A friend of mine has a guide dog - unfortunately too many people try to touch the dog and make a fuss of it.

[news19k]

Cloaks do not need a negative refractive index (although perhaps exterior cloaks might, I'd have to check. But this isn't one of those.)

As regards the original link, the displayed "invisibility cloak" doesn't at all match the intent of the ideal Dolin (1951) and/or Pendry/Schurig/Smith (2006) concepts. At best it's a crap half-version of the bi-directional Leonhardt (2006) idea. But I suppose it sort of works, which is always fun.

From what I can see (which is not much in the way of detail) it looks much like a modulated & in-part strongly diverging lens (presumably Fresnel, given the thinness); hence for a carefully positioned object, a forward observer will see only past the object to a variously distorted background.

Notably, however, there is no real attempt to reconstruct any proper view of the background, so it is helpfully (or perhaps sneakily) positioned against a very horizontally self-similar backdrop to make it less unconvincing. Naturally, the blurriness helps considerably in this regard.

I would be surprised if there was anything really exotic about their concept or their implementation. And the quote "HyperStealth Biotechnology Corp said its new applications related to their Quantum Stealth technology - otherwise known as the Invisibility Cloak" smells

- at least to me - very strongly of a buzzword-bingo infected barnyard. But then, what would I know about transformation optics?

#Paul

[Brian Gaff (Sofa)]

I looked at this some time ago, and decided that using any current tech, it was impossible to do at all wavelengths. Its a bit like full colour holograms. There are problems of phase and of cours the incoherence of normal light stops you using other techniques. Brian

[news19k]

Oops, that should be 1961, not 1951.

There's a translation at

for any interested parties.

#Paul