Why not just cloak with a wall?

the physics arXiv blog » Blog Archive » Cloaking objects at a distance

Cloaking a region of space is relatively straightforward but cloaking an object in that space is another matter. Lai and co say the trick is to work out the optical properties of the object and then embed the “complementary image” within the cloaking material. So a plane wave would be bent by the object but then bent back into a plane as it passes through the cloaking material.
Et voila: cloaking at a distance. And in a way that doesn’t leave the cloaked object blind.

Okay, I’ve made my cloaking material out of unobtanium and embedded a wavelength-accurate complementary image of the thing to be cloaked (which had better not move or flex), and now any light that passes directly from the cloaked object to an observer on the other side of the cloak won’t show the object. Hurrah! Oh, and the cloaked object will see an oddly-distorted view of the observer (because the light gets fritzed on the way from the observer to it) but won’t be completely blind in that direction.

Now let’s say the observer moves, or there are a bunch of observers. I have to build another block of unobtanium with another perfect complementary image of the thing to be cloaked at each angle from which an observer is going to look. In the areas where an observer’s field of view passes through cloaking material on the front and back, I’m going to need a wavelength-perfect image of the far-side unobtainium embedded so that the observer doesn’t just see the cloak. Oh, and vice versa. I’m sure there’s an analytical technique for creating two pieces of unobtanium, each containing a complementary image of each other and a third object without going into an infinite regress, but I don’t ever want to find out how it works.

Then, when we’re done, the object to be cloaked will be surrounded with a wall of incredibly distorting material, through which it can see only by apply equally complicated distorting lenses, which in turn will alter its image…

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