'Cloaking' device uses ordinary lenses to hide objects across range of angles

[rtxoff]

Interesting new approach on cloaking from the university of rochester.

Read the full article here and/or watch the video:

[dbmorpher]

But that's not really cloaking.

You can get the same result with a peephole

[Camacha]

But that's not really cloaking.

What would you consider real cloaking?

[ZetaX]

I am pretty sure to have seen such a construct before and am a bit baffled by a university selling it as "novel". But that might just be me imagining things.

The actual research in "cloaking devices" has a different goal, though: researching metamaterials. Cloaking is just a byproduct.

[dbmorpher]

What would you consider real cloaking?

Like what ZetaX said what I believe true "cloaking" is is the use of metamaterials to make an object undetectable in multiple reference frames.

[Jovus]

....... answer: the 1960s called, DARPA wants its technology back.

[KerikBalm]

1960's? DARPA?

A kid playing with a magnifying glass can get this effect... I know I did...

Its not a cloak.

Conceptually, its about as close to a cloak as 2 periscopes, each composed of 2 mirrors

something like this:

................/----------------\

................|....................|

eye---------/........X..........\-----------------Background

Where / and \ are mirrors (assume a 45 degree angle) while --- and | denote the path of the light/the line of sight between one's eye and the background

Would you say the object X is cloaked? I think not.

[magnemoe]

I am pretty sure to have seen such a construct before and am a bit baffled by a university selling it as "novel". But that might just be me imagining things.

The actual research in "cloaking devices" has a different goal, though: researching metamaterials. Cloaking is just a byproduct.

The novel part it the way they bend the light, however its just fancy optic. I kind of doubt metamaterials will work well as an practical cloaking device either, stealth as in non reflective is pretty easy. looking transparent is far harder. Adaptive camouflage as in changing color to match background would work most of the time

[ZetaX]

No, there is nothing novel to it.

All they seem to do is using lenses to make the bundle of light smaller in radius, presumably by just converging to a focal point, then making the rays parallel again after, and then add a second such aparatus to revert to mirroring caused by the first half.

On the mirror examples: those have the obvious flaw that there is no direction from which it is truly cloaked (you will always see the mirror). The lenses work at least form one direction.

[rtxoff]

No, there is nothing novel to it.

They claim in the video that nobody has done this before in such an configuration. Maybe you have some evidence supporting your statement?

All they seem to do is using lenses to make the bundle of light smaller in radius, presumably by just converging to a focal point, then making the rays parallel again after, and then add a second such aparatus to revert to mirroring caused by the first half.

, as they show in the video the light is bent into a ring around the center axis, the only thing stopping the cloak was when they made a ring with their fingers and moved it in the middle of the experiment.

You could show some trust to them, they are from the university of rochester and not some hobby shed.

Edited October 3, 2014 by gpisic

[EdFred]

What if it's looked from a reference frame 90º to the light bending. Does it still show up? Oh, it does? Not a cloak.

[Geneborg]

Hm..well, its a nice..trick, and, tbh, they figured out how to do it with "of the shelf" stuff, so good for them, why not have some fun.

But, look closely on how they hold their hands, how far down they put the ruler/pencil...this cloaking device has a weakness. It has to focus somewhere, thus if you would put a solid plate behind it it would show an artefact.

So yea, nice trick for an optics-student to show he understands light, and if you look at their faces, they take it lightly too, its something to have fun with.

[ZetaX]

, as they show in the video the light is bent into a ring around the center axis, the only thing stopping the cloak was when they made a ring with their fingers and moved it in the middle of the experiment.

They don't show that. They actually talk about the center being the only point where nothing is allowed to be for the cloaking to work. And if that does not convince you, I can even show you, using topology, that it is completely impossible to work as you say:

The lense is a full circle from the front, which is a "simply connected" (it is a single undivided object with no "holes") shape. Going along the path of a (initially parallel) light bundle and looking at vertical sections (=when you shine light through it and hold paper in there) is a "homotopy" (a [continuous] deformation). Homotopies preserve the property of being simply connected. A ring is not simply connected as it has a hole. Therefore you can never get a ring.

[rtxoff]

You are right, i misunderstood that part the first time i watched it. Sorry.

[PB666]

more along this line

https://www.sciencenews.org/blog/science-ticker/invisibility-cloaks-slim-down

[baggers]

A maybe more "promishing" cloak of invisibility:

OK, that don't look impressive at all, but it's a 1,300 square microns cloak at the moment.

They say they can make a bigger one.

here the link: https://newscenter.lbl.gov/2015/09/17/making-3d-objects-disappear/

They say that sort of chinese things too:

“Recent developments in metasurfaces, however, allow us to manipulate the phase of a propagating wave directly through the use of subwavelength-sized elements that locally tailor the electromagnetic response at the nanoscale, a response that is accompanied by dramatic light confinement.â€Â

But it's more a "flat mirror cap" than a "transparency cap":

In the Berkeley study, when red light struck an arbitrarily shaped 3D sample object measuring approximately 1,300 square microns in area that was conformally wrapped in the gold nanoantenna skin cloak, the light reflected off the surface of the skin cloak was identical to light reflected off a flat mirror, making the object underneath it invisible even by phase-sensitive detection.

Still look cool, and I want one.

[burn] Ach, sorry, PB666 previous link is on the same thing. I'm burned.

Edited September 18, 2015 by baggers