invisible cloak

[fredreload]

I want to create an invisible cloak, basically any light photon that bounces off this cloak becomes ultraviolet, therefore the eyes cannot perceive it, render it invisible

[Klaynos]

That wouldn't be invisible. It'd be black.

[fredreload]

Black is when light is absorbed and nothing bounces back, invisible is if you increase or decrease the wavelength of light by a significant amount, I'm not sure if it is doable

[Klaynos]

Black is when light is absorbed and nothing bounces back, invisible is if you increase or decrease the wavelength of light by a significant amount, I'm not sure if it is doable

No invisible is when light can pass straight through without being altered. Black is when something doesn't reflect visble light.

[fredreload]

No invisible is when light can pass straight through without being altered. Black is when something doesn't reflect visble light.

I said light bounces off, but in ultraviolet or radio wave. If it reflects it's a mirror. Well but it doesn't exactly pass through either. Right it might be black, I'm sorry Klaynos

Edited November 5, 2016 by fredreload

[Klaynos]

I said light bounces off, but in ultraviolet or radio wave. If it reflects it's a mirror

If it doesn't reflect visible light, it's black.

[fredreload]

If it doesn't reflect visible light, it's black.

Right, the visible spectrum of the light is converted, need more thoughts on this, my bad

But on the contrary, black color could be converting light to a non-visible spectrum instead of having it absorbed?

[Klaynos]

If it converts from visible to non visible on a broadband it'll be black.

[Raider5678]

If it converts from visible to non visible on a broadband it'll be black.

Now you have to wonder if this cloak would be useful for anything.

[Endy0816]

You'd be a walking blacklight

[Sensei]

I want to create an invisible cloak, basically any light photon that bounces off this cloak becomes ultraviolet, therefore the eyes cannot perceive it, render it invisible

 

You can't change photon with lower energy (visible light), to higher energy. Each to each.

It would violate energy conservation.

Object has to absorb couple photons with smaller energies, to create new higher energy photon.

f.e. 2 eV photon + 3 eV photon = 5 eV photon.

From two initial photons there could be one photon emitted back.

 

Additionally UV photons, x-ray photons or gamma photons are visible, unlike what you think, but indirectly.

If UV photon, or x-ray photon, or gamma photon, hits some object/atom/particle, there will be created new photons, which have energies lower than initial incoming photon.

f.e. 5 eV photon = 2 eV photon + 3 eV photon.

And you can see white light after using UV light source...

It's used all the time for detecting security features in banknotes (they emit white light when they are illuminated by UV photons).

You don't see UV photons directly, but you see other elements excited by them and emitting light at visible spectrum.

 

Strong x-ray or gamma photon source will cause white dots appearing in your eyes even if you close eyes (very annoying if you're astronaut)..

They can be also visible by cameras as you can see f.e. in this video

Edited November 6, 2016 by Sensei

[fredreload]

Well then the only way is to have a ray tracing suit, nothing new, I've read it somewhere, first you record the image on one end, then you project the image on the other end with a screen, is as simple as that. With a suit like that even though light does not pass through you still have an invisible effect. So absorb photon on one end, and reemit it on the other end

Edited November 6, 2016 by fredreload

[fredreload]

Something that would reflect light by 180 degrees on all sides, something like this.

 

http://cdnassets.hw.net/dims4/GG/eaebca3/2147483647/resize/876x%3E/quality/90/?url=http%3A%2F%2Fcdnassets.hw.net%2F5b%2F54%2Ffd55d90747c189812134d33e35f1%2Ftech02-internal-20reflection-legacy-20reflector-drawings-tech-tcm47-2169643.jpg

[tar]

Well then the only way is to have a ray tracing suit, nothing new, I've read it somewhere, first you record the image on one end, then you project the image on the other end with a screen, is as simple as that. With a suit like that even though light does not pass through you still have an invisible effect. So absorb photon on one end, and reemit it on the other end

 

fredreload,

 

The trick is to design a "sceen" situation, that would look different from every possible different angle. That is you have to have both cameras and screens pointing in all directions. If you know the position of the observer, you can face the screen in her direction, and take a picture of the scene behind and project it toward her and be invisible. But if she moves to the left and you are still projecting the scene behind toward her former position, she will see the screen image does not match the background, in the shape and size of your cloak, thus giving you away.

 

Like your making the cloak look black, you would not be invisible, you would be a black blob moving across the landscape, a ray tracing suit would only be affective if the camera and screen were in line to where what was behind the object, from the perspective of the viewer toward which you wish to be invisible, was projected on the front of the suit in the exact size required by the distance the observer is from both the object being cloaked, and the scene exactly behind.

 

Perhaps this is possible through some tracking system that would identify the viewer and the position and distance of her eyes and project the appropriate image toward each of her eyes as she moved, but the system would fail, as soon as there was a second viewer.

 

Regards, TAR

 

Regards, TAR

Edited November 6, 2016 by tar

[fredreload]

 

fredreload,

 

The trick is to design a "sceen" situation, that would look different from every possible different angle. That is you have to have both cameras and screens pointing in all directions. If you know the position of the observer, you can face the screen in her direction, and take a picture of the scene behind and project it toward her and be invisible. But if she moves to the left and you are still projecting the scene behind toward her former position, she will see the screen image does not match the background, in the shape and size of your cloak, thus giving you away.

 

Like your making the cloak look black, you would not be invisible, you would be a black blob moving across the landscape, a ray tracing suit would only be affective if the camera and screen were in line to where what was behind the object, from the perspective of the viewer toward which you wish to be invisible, was projected on the front of the suit in the exact size required by the distance the observer is from both the object being cloaked, and the scene exactly behind.

 

Perhaps this is possible through some tracking system that would identify the viewer and the position and distance of her eyes and project the appropriate image toward each of her eyes as she moved, but the system would fail, as soon as there was a second viewer.

 

Regards, TAR

 

Regards, TAR

I agree with you, that is the example I saw. Thing is I want to improve it and what I have in mind is a spherical shape object capable of deflecting light to the back as light enters. For instance when light enters from the front it would deflect it to the right by 45 degree, then another 45 degree to the left, and exit from the back, sort of like how diamond works. That way this sphere would exist and look as if it is invisible without any other mechanics.

 

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light source

Edited November 6, 2016 by fredreload

[Strange]

https://en.wikipedia.org/wiki/Metamaterial_cloaking

[John Cuthber]

So far, you have failed to distinguish between an invisible cloak and an invisibility cloak.

A polythene bag is fairly nearly invisible...

[Phi for All]

So far, you have failed to distinguish between an invisible cloak and an invisibility cloak.

A polythene bag is fairly nearly invisible...

 

Nor has he established the context for the invisibility. My invisibility cloak is invisible and can't be detected by any sense, but doesn't confer those traits on me. It's invisibility is strictly for making itself invisible.

[John Cuthber]

I wasn't strictly sure if JK Rowling had more or less canonically defined "invisibility cloak." so I googled it.

And Google offered- as one of the options for the search- you guessed it "search for images of invisibility cloak."

 

I give up.

[Sensei]

A polythene bag is fairly nearly invisible...

 

Transparent materials are visible because they have different refractive index than medium they are placed.

 

When either medium and transparent material have the same IOR

what's inside is not visible (at least in visible spectrum), as light pass through it without being bend.

It's sometimes used by magicians to do this trick:

Edited November 7, 2016 by Sensei

[fredreload]

Well if you are at the center of the spherical invisible cloak, it will make you invisible, doctor Strage got it, it will look something like this

||||||

|/ \|

|( )|

|\ /|

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The trick is to not create any reflection on the material surface and tries to guide the flow of light around the object back to its original position

Edited November 7, 2016 by fredreload

[fredreload]

https://www.cnet.com/news/invisibility-cloak-uses-lenses-to-bend-light/

 

 

P.S. Thanks Google!

P.S. Well, didn't come up with the lens idea

Edited November 7, 2016 by fredreload

[tar]

fredreload,

 

In the invisible four lens demo from Rochester I noticed that the grid behind is a little smaller than the grid around. Probably because the light has traveled farther than a straight line distance. In another link, the problem of phase change was brought up, which has similar cause. If you have a sphere and you are guiding the light around the sphere, the distance of travel of the light will be greater, around the circumference than through the center. Therefore the light coming from the backgrround, will be affected in two ways. Size of image seen, and phase of the light. A careful viewer or instrument would be able to pick up such irregularities in the area of the cloaking device, and such irregularities would be in the shape of the cloaking device, hence the device itself would not be invisible. It would be similar to putting something inside a box. You can't see the item, but you can see the box.

 

Regards, TAR

[fredreload]

fredreload,

 

In the invisible four lens demo from Rochester I noticed that the grid behind is a little smaller than the grid around. Probably because the light has traveled farther than a straight line distance. In another link, the problem of phase change was brought up, which has similar cause. If you have a sphere and you are guiding the light around the sphere, the distance of travel of the light will be greater, around the circumference than through the center. Therefore the light coming from the backgrround, will be affected in two ways. Size of image seen, and phase of the light. A careful viewer or instrument would be able to pick up such irregularities in the area of the cloaking device, and such irregularities would be in the shape of the cloaking device, hence the device itself would not be invisible. It would be similar to putting something inside a box. You can't see the item, but you can see the box.

 

Regards, TAR

You are right, the distance traveled would be greater, so it is not perfect cloaking. Well, one thing I found out from the video is essentially that the image can be passed through the convex lens in this way and having the image recovered after it passes through. Of course you can't build a sphere out of convex lens, and the image would probably get inverted on the other side, but probably some tweaks and it would work, convex then concave

 

http://www.passmyexams.co.uk/GCSE/physics/concave-lenses-convex-lenses.html

[tar]

fredreload,

 

Two thoughts.

 

About the sphere, if you think of a sphere around a cube, the 12 edges of the cube provide a division of the sphere to where 6 Rochester cloaks could be built with equal spacing, allowing there to be at least 6 places around the sphere where you could stand to view the background without seeing the items hidden within the sphere where the light rays are not.

 

The other thought is using fiber optic arrays. I wonder if you had a wall of ends of fiber optic strands and a similar wall of the other end of the fibers in the same orientation, to each other as the other end, whether you would see the image on the opposite side, as if you where looking through a window. If you would, then putting an item between the fibers and routing the fibers around the item would be a ray tracing analog. You would still have the distance problem, but you could set up your twelve sides of the sphere on the edges of a cube, so to speak, and effectively see the view on the other side of the device, without seeing the items you have hidden between the strands.

 

Regards, TAR

but alas I ran out of room inside the sphere for all the fibers, being that there is no circumference to go around since each of the 12 faces is actually on the circumference and each face is packed solid with fiber...oh well, maybe a combination of electronics and fibers where the signals could be recorded on the one face and regenerated on the other, maybe every other fiber being a receiver or a sender...or something...just a thought

Edited November 7, 2016 by tar