Different better invisibility suit

To recap, the problem is to adapt the old idea of "cameras on one side linked to a screen on the opposite side" so that it works when viewed from all angles.

As before, we'll assume we want an invisible cube, for now.

There are two problems to solve:

1) how to have a camera on each face, but keep the camera itself invisible

2) how to have the image viewable from all angles, without parallax.

Here's how. We'll start with a clunky version which is easy to understand. We'll also imagine (for now) that we only want to be able to walk around this cube, and not climb above or dive below it.

On the front of the cube, we have a series of cameras. The cameras are strange, because each one is very tall (as tall as the cube) and narrow (maybe 1mm wide). It "sees" only a vertical stripe of its surroundings, looking straight out from the face of the cube. The face is covered with maybe a hundred of these tall skinny cameras, spaced 2mm apart.

In between these cameras are the display elements. Each element is a single column of LEDs, 1mm wide. Each display strip is linked to a single camera on the opposite face.

Everything is now fine: each face will display what is shown on the opposite face, in the form of vertical strips 1mm wide, with gaps of 1mm.

However, the gappiness is a problem. There's also a second, more serious problem - the illusion will only work if you're standing square-on to the front or back faces. If you look from an angle, you'll get a parallax error and the illusion will fail.

Now the cunning bit.

We take a clear plastic sheet with vertical ridges on it. The ridges are vertical lenses. If you put this sheet in front of the face of the cube, the lenses will direct the light from the LED stripes straight forward. Likewise, the cameras in the interleaved strips will see only the image from straight-forward.

Now move the sheet just a tiny fraction to one side. Now, the lenses in the sheet direct the LED output off at an angle, so that they can be seen only by someone who is off at that angle (the viewer standing square-on will not see anything - the lenses are bending the light from the LEDs away from him). Likewise, the camera strips will see an image from the same angle. (Remember, the camera strips on the front face are connected to the LEDs on the rear face, and vice versa).

Thus, as we move the lens-covered plastic sheet s l o w l y from left to right (on both the front and back faces of the cube, at the same time), the invisibility illusion will work first for someone standing off to the right of the cube, then for someone standing face-on, then for someone standing off to the left. When the illusion isn't "working" for someone (ie, when the sheet sweeps away from them), they just see darkness.

Now, persistence of vision is a wonderful thing. If we oscillate the sheet back and forth at sufficient speed, *all the viewers* will see the illusion working perfectly. Or, equally, a single viewer can walk past the face of the cube, and will see a perfect, parallax-error-free image at all times!

OK, now, we need to make it all a bit better. First, we may have difficulties keeping these oscillating lens- sheets "in sync" between the front and back faces of the cube. No problem: electronics can delay the image (as it passes from the cameras on one side to the displays on the other side) by a millisecond or two as necessary, to restore the sync.

Next, we want the illusion to work not just as someone walks around the cube, but also as they climb above it or crouch below it. Again, no problem: we use two sheets, at right angles, oscillating at right angles, so allow both vertical and horizontal compensation.

Finally, we might not want mechanical sheets (they will be hard to oscillate quickly, if they're big). Again, no problem: there are electrorefractive materials whose refractive index can be changed by a voltage, and these can be fashioned into lens systems which will "sweep" back and forth (and up and down) in the same way.

Gadulka!