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Superman’s Transmission Matrix

I was torn this week between using two different types of titles for this blog.

One was a sensationalized attention grabbing title like:

Scientists develop method to see through solid objects like Superman

My other idea was more precise but a bit off-putting:

Researchers in Paris create a transmission matrix to see through an opaque layer of zinc oxide 80 thousandths of a millimeter thick.

Predictably, the coolness of this development lies somewhere between these two titles.

The research in question was done at ESPCI, the City of Paris Industrial Physics and Chemistry Higher Educational Institution.

The scientists at ESPCI did indeed devise a way to see through an opaque material but it’s not easy like shining some x-rays on a patient. You first need to know a lot about the material like its molecular structure and the way it effects and scatters light that is trying to go through it.

Their experiment shined a green laser beam at a layer of zinc oxide only 80 micrometers thick. Zinc oxide is commonly used in white paint and some sunscreens. Remember seeing lifeguards with bright white sunscreen on their noses? That was zinc oxide.

By examining how the beam of light changed as it interacted with the material, the scientists were able to construct a numerical model that described the interaction in detail. This model is called a transmission matrix. If you saw this matrix for light going through pure water if would have maybe a few numbers in it. For zinc oxide the transmission matrix  consisted of over 65,000 numbers.

Using this matrix, you could manipulate the light before it went through the material to come out the other end and focus on whatever was there. Conversely, you could also take the feeble disorganized light coming out of an opaque object, and reassemble an image of what was on the other side. This is very similar to the chemical lasers in development designed to shoot down missiles. Some of them send a low-power laser beam into the atmosphere to sample what the atmosphere is doing at that time. This information is used to manipulate the subsequent powerful laser beam so the atmosphere focuses it instead of scattering it. They in essence “pre-scatter” the laser beam so the atmosphere could then un-scatter it back to the way it would have been if the atmosphere wasn’t there. Cool huh?

Before you try to steal this equipment to see through a wall safe, physicist Allard Mosk at University of Twente in Amsterdam says it would be a million times more difficult to see through a 4 inch wall. He concludes that this technology will probably never be any good for doing that.

That seems a bit pessimistic to me. Assuming this is a limitation on computing power, I would hesitate to say “probably never”.  On the other hand, this guy may be too optimistic. Most walls block not just a little light but all of it. If no light goes through then using this technique would be somewhat more difficult than merely a million times. Perhaps you could shoot an intense but harmless laser at a wall in such a way that some photons get through. I’m not sure if that would work. Anyone know?

This still could have a bright future though even if he is correct. Building a lens for nano-scale optical devices is notoriously difficult. This method essentially turns almost any material into a lens with no grinding or polishing or anything except making a transmission matrix for it.

Further in the future Biological imaging may even be possible. This would be especially difficult considering that biological tissue is constantly moving around inside but it may be doable.

Even with the apparent limitations inherent in this technology, we may one day develop see-through vision that would make even Superman proud.

1 comment to Superman’s Transmission Matrix

  • KeithJM

    Very interesting article. On the title — “Scientists develop method to see through solid objects like Superman” seems to imply that scientists can see through Superman. I like the one you ended up going with.

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