This is inspired by Michael Steven's new video about optics.

He shows off Selenite, which has the property that light entering on one side travels perpendicularly down the crystal until it exits the other side.

The problem with it is that it requires the crystal to be held up to whatever you're looking at. What I'm looking for is a more strict version of it, that actually reflects/absorbs light that isn't coming it perpendicularly.

What I hope to see is a crystal/material that showed an image of whatever's behind it, as if it were on the surface.

Does such a thing exist?

  • $\begingroup$ Just checking: do you want a material that will produce a 2D image on one face, of the 3D scene behind it? $\endgroup$ – S. McGrew Aug 26 '18 at 0:14
  • $\begingroup$ @S.McGrew I think the result of the effect I'm looking for would create a 2D image. Since light coming in at any distance would be treated the same and released on the same point on the surface. $\endgroup$ – Daffy Aug 26 '18 at 0:20
  • $\begingroup$ @S.McGrew Oops, I didn't realize you asked a yes/no question. Yes, that's what I'm looking for. $\endgroup$ – Daffy Aug 26 '18 at 0:26
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    $\begingroup$ A glass surface does this as Brewster's angle. $\endgroup$ – C. Towne Springer Aug 26 '18 at 0:54

There is not a material that can produce a 2D image from a 3D scene. There are structures that can do it. For example, if a small lens is placed in front of a selenite crystal (or equivalently, in front of a coherent optical fiber bundle) to image the scene onto the scene-facing surface of the crystal, then the scene will appear in 2D on the opposite surface of the crystal. There are variations on this theme, but they all amount to the same thing: the scene must be converted to a 2D image and then the image must be focused onto a surface of the crystal.

I don't think a glass surface at Brewster's angle does what you want: it "simply" passes light of one polarization and reflects light of the other polarization.

  • $\begingroup$ "There is not a material that can produce a 2D image from a 3D scene." Is this because of some fundamental law? Or have we just not found something with the right structure? $\endgroup$ – Daffy Aug 30 '18 at 6:50
  • $\begingroup$ There is not a law specifically to that effect, but you can deduce it from what we know about optics. Consider how the light from the 3D scene gets to the block of material: every point in the scene illuminates every point on the scene-facing surface of the material. Moreover, when you look at a 3D scene with your eye, you see a 2D image but the components of the scene shift relative to each other if you move your eye even a little bit. A 2D image is really a single-point perspective of a 3D scene. Something needs to determine which point perspective to use. $\endgroup$ – S. McGrew Aug 30 '18 at 15:15
  • $\begingroup$ In the example I gave using a lens, it's the lens position that picks the point perspective to use. $\endgroup$ – S. McGrew Aug 30 '18 at 15:15

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