
Can computers read through a book page by page without opening it? - triplesec
http://cameraculture.media.mit.edu/can-computers-read-through-closed-books/
======
fma
The research has interests of museums that want to read books without opening
and damaging them. Is there any chance the scans can damage them?

Also, what are the laws of the US government applied this to reading our
letters. Our mail is protected by law from opening, but what if they aren't
physically opened?

~~~
kens
You don't need this technology to read through an envelope. You can get a
spray (envelope X-ray spray) that makes the envelope temporarily transparent
and then evaporates without a trace. The other way to read mail without
opening it is to insert a shaft at the top of the envelope, wrap the contents
around it, pull out the contents to read, and then reverse to put the letter
back in the envelope.

I think I saw this stuff at the International Spy Museum in Washington DC; it
was a much more interesting museum than I expected.

~~~
robryk
In many cases you can just shine bright light through the envelope with the
letter inside.

~~~
kzrdude
You're a hacker!

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rwmj
Might this be used to read the famous burned scrolls of Pompeii and
Herculaneum? (Although according to this article, current thinking is they
might be able to read them with X-rays:
[http://www.smithsonianmag.com/history/ancient-scrolls-
blacke...](http://www.smithsonianmag.com/history/ancient-scrolls-blackened-
vesuvius-are-readable-last-herculaneum-papyri-180953950/?no-ist))

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DavidWanjiru
I find this interesting because I've ever thought of it conceptually, the idea
of a scanner that instantly scans closed books (instantly because one pulse of
whatever EM wave you're using suffices). I thought about it after reading
about the Timbuktu manuscripts that were saved from Boko Haram in Mali. I hear
many of them are too delicate to open. I hope this works. It'd be awesome for
so many use cases.

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gus_massa
Somewhat related: "X-Rays Expose a Hidden Medieval Library"
[https://medievalbooks.nl/2015/12/18/x-rays-expose-a-
hidden-m...](https://medievalbooks.nl/2015/12/18/x-rays-expose-a-hidden-
medieval-library/) HN discussion:
[https://news.ycombinator.com/item?id=10758257](https://news.ycombinator.com/item?id=10758257)
(86 points, 267 days ago, 6 comments)

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Animats
The sensing system used was from "Zomega Terahertz Corporation", which had a
web site "z-thz.com". That company seems to have disappeared at the end of
2015, but it's still in archive.org. Can't find any info that indicates what
happened to them.

Zomega was one of the few companies with a true terahertz system, at 2THz, or
0.006in wavelength. Other "terahertz" products seem to be around 100GHz, which
is much easier to reach; there are 77GHz automotive radars.

Zomega systems had already been used to image hidden layers in paintings, so
looking into a stack of paper wasn't a big stretch. This new paper is mostly
about a data reduction technique.

Overview of terahertz technology.[2]

[1]
[https://web.archive.org/web/20151220072732/http://z-thz.com/](https://web.archive.org/web/20151220072732/http://z-thz.com/)
[2] [http://spectrum.ieee.org/aerospace/military/the-truth-
about-...](http://spectrum.ieee.org/aerospace/military/the-truth-about-
terahertz)

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alanz1223
Does anyone know what kind of oscillator is used to produce the signal? And
how they managed to get such a high sample rate?

~~~
eternauta3k
They use an ultra-short laser pulse which "gates" (enables/disables) the
detector for a very short window of time. They repeat the stimulus+gated
detection with different offsets in order to sample different parts of the
signal.

The ultra-short laser pulse can be generated through purely-optical means. You
have a laser pulse traveling around a cavity. Due to a combination of non-
linear optical effects, each round-trip tends to shorten and concentrate the
pulse. The resulting pulses can be much shorter than what's achievable with
electronic generators.

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cdevs
"Write it down on paper I don't trust passwords in computers..

All that's left is thought scanning and then we will think about rethinking
passwords.

~~~
sova
or just abandoning the notion of passwords entirely

~~~
Houshalter
I hope that never happens. I don't want to be tied to a specific Facebook
account and computer for everyone I do online for the rest of my life.

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amelius
> Statistics of the electric field in THz TDS can provide much better results
> for layer localization at deeper layers (lower SNRs) than conventional
> deconvolution techniques.

Could this technique also be useful for crystallography, or electron
microscopy?

~~~
skykooler
Terahertz waves range in length from 1 micrometer to 1 millimeter. These are
far too large to be able to image things at the scales of crystals. (That's
part of why X-rays are used for crystallography - they provide higher
resolution than visible light, because the wavelength is shorter.)

~~~
amelius
Petahertz (or higher) is not an option, I presume?

~~~
kragen
Petahertz electromagnetic radiation is what's currently used for diffraction
crystallography; it's conventionally known as "X-rays" (or "gamma rays" if it
comes from radioactive decay instead of from Bremsstrahlung.)

~~~
amelius
Yes, can we use time-domain techniques on this frequency range?

~~~
kragen
You want to measure the instantaneous amplitudes of a wave packet in the
petahertz range at above the Nyquist frequency?

I don't want to say it's impossible, but I think you'd have to improve the
capabilities of our instruments by about four orders of magnitude, which means
you would have to invent several new major technologies.

Maybe if you digitize the time-domain pulses using some kind of controlled
nuclear reaction? Electronics are far too slow (although I don't really
understand why, so maybe that can be fixed). X-ray-stimulated nuclear
reactions are going to be tricky to get to happen at all, much less to chain
together into computational circuits, although in that case maybe you can use
α particles or neutrons to carry the information around between the
computational elements, simplifying the task somewhat.

It seems like, however you manage to measure it, the quantization of the
radiation is going to pose really significant problems to measuring its
amplitude accurately as a function of time, but maybe you can get around that
by repeating the pulses a lot of times. But you'll need to make sure that
you're emitting pulses of the same shape, rather than just pulses with a
similar frequency spectrum and envelope but varying relative phases among the
frequencies.

On the other hand, if you just want to measure the time-of-flight for X-ray
wavepackets to sub-picosecond precision, without worrying about the time-
domain waveform within the packet, I don't think that gets any harder or
easier depending on the "carrier frequency" of the wavepacket — X-rays should
be just as easy as terahertz light. You do need a few terahertz of bandwidth,
so you aren't going to be able to do this with bursts of gigahertz microwaves.

X-rays' interaction with the material you're trying to image might be less or
more convenient; their cross-section for backscattering is pretty small, but
maybe you could scan the book from different angles and use total internal
reflection to find interfaces between materials in the book with different
refractive indices. This would also reduce your requirements for time-domain
precision down into the hundreds of GHz range, which is a lot easier to deal
with.

~~~
eternauta3k
> Maybe if you digitize the time-domain pulses using some kind of controlled
> nuclear reaction? Electronics are far too slow

Terahertz TDS already samples at frequencies beyond the capabilities of bare
electronics (look at my other comment on this story).

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triplesec
Journalism about this research: [http://www.ibtimes.com/mit-georgia-tech-
develop-system-read-...](http://www.ibtimes.com/mit-georgia-tech-develop-
system-read-closed-books-using-terahertz-radiation-2414140)

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sterex
Could this be implemented to scan through layers of other material, say
clothing, and used for real-time scanning at sensitive areas such as airports?

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kirykl
useful technology for the MIT blackjack team

~~~
astrodust
Scan the shoe and know the optimal betting strategy? You'd need some pretty
serious technology to hide your knowledge and come up with a betting strategy
that's optimally _undetectable_ as well.

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ianai
Of course I love the premise. But I also fear what this could allow to be
surveilled.

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neom
I wonder if you could use a chemoreceptor for this also.

