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Sheffield Scientists Have Revolutionized the Electron Microscope

samzenpus posted more than 2 years ago | from the I-can-see-clearly-now dept.

Science 90

An anonymous reader writes "For over 70 years, transmission electron microscopy (TEM), which 'looks through' an object to see atomic features within it, has been constrained by the relatively poor lenses which are used to form the image. The new method, called electron ptychography, dispenses with the lens and instead forms the image by reconstructing the scattered electron-waves after they have passed through the sample using computers. Scientists involved in the scheme consider their findings to be a first step in a completely new epoch of electron imaging. The process has no fundamental experimental boundaries and it is thought it will transform sub-atomic scale transmission imaging."

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holography? (1)

miknix (1047580) | more than 2 years ago | (#39280271)

didn't read TFA but did they just reinvent holography? http://en.wikipedia.org/wiki/Holography [wikipedia.org]

Re:holography? (1)

Anonymous Coward | more than 2 years ago | (#39280413)

no, they are just are using a synthetic aperture
http://en.wikipedia.org/wiki/Synthetic_aperture_radar

Re:holography? (3, Informative)

Anonymous Coward | more than 2 years ago | (#39280493)

No really. In SAR processing you need to know the phase of the signal. The important part here is they do it without phase information. The article doesn't explain how they reduce the ambiguity.

Re:holography? (1)

cyfer2000 (548592) | more than 2 years ago | (#39282865)

I think TFA meant to say they are going to use phase information, but TFA didn't say how they are going to get phase information.

Re:holography? (1, Funny)

Anonymous Coward | more than 2 years ago | (#39280437)

Sheffield, yeaaaaah, home to two shit football teams and the greatest condiment known to man, Henderson's Relish [hendersonsrelish.com]

Re:holography? (0)

Anonymous Coward | more than 2 years ago | (#39285725)

Mmm, must get more hendersons...

Re:holography? (2)

John Hasler (414242) | more than 2 years ago | (#39280449)

No. Read TFA (which is s bit short on detail).

Does anyone understand it? (0)

Anonymous Coward | more than 2 years ago | (#39281247)

No. Read TFA (which is s bit short on detail).

I read the original article from Nature (links posted several times below).

I understood very little of it. I got aperture, electron, wave and a couple of other words but other than that, it was so over my head I gave up.

I think the only people who would understand it are folks with PhDs in particle-optical-physics with ten years of post doc experience working in the electron microscope field.

Re:Does anyone understand it? (2, Insightful)

tqk (413719) | more than 2 years ago | (#39281877)

I think the only people who would understand it are folks with PhDs in particle-optical-physics with ten years of post doc experience working in the electron microscope field.

I really hate hearing people say stuff like this. Science isn't magic with scary, unknowable stuff going on behind the curtain. It's *very often* easily understood (car analogies, anyone? Hit me!!!111one :-). The devil's in the details and the details can be subtle, but it's not magic.

SEM bombards stuff with $something (energized particles, radiation, ...) which reflects back onto something that stores that reflected $something. It's the same process as an optical camera, but working at different wavelengths and energies (yes, please do feel free to correct me if I'm talking through my hat in your opinion; I won't be offended, honest).

I'm having a difficult time understanding TFS's "... after they have passed through the sample using computers."

Passed through? Since when!?! Passed through the sample using computers? What? SEM doesn't "pass any energy through" whatever it's sampling.

Are we talking about 3D representations of sample then using computers to $massage sample to death? That might make sense.

People should read more about science and how it's done. It wouldn't be as scary to them if they did.

Re:Does anyone understand it? (2)

ILMTitan (1345975) | more than 2 years ago | (#39282063)

There are several types of electron microscopes.
You are talking about Scanning Electron Microscopes (SEM), which do work like optical microscopes, bouncing an electron beam off of the object being imaged.
The summary is talking about Transmission Electron Microscopes (TEM), which pass an electron beam through the object being imaged, and works more like microfilm.

Re:Does anyone understand it? (3, Interesting)

ceoyoyo (59147) | more than 2 years ago | (#39282081)

This is transmission electron microscopy (not SEM), where electrons are shot through the sample. It's kind of like a standard light microscope where the light goes through the sample and you see the shadow.

What they're doing is reconstructing an image from diffraction patterns instead of focusing it with a lens. I think it's vaguely similar to interferometry. They can apparently also do it with light microscopes, which has certain advantages. Unfortunately the article mixes up the electron and light microscopy - you don't do TEM on living cells, for example, no matter how fancy an imaging system you have.

Re:Does anyone understand it? (2)

AK Marc (707885) | more than 2 years ago | (#39282391)

I'm having a difficult time understanding TFS's "... after they have passed through the sample using computers."

TEM is like an X-ray. You shine the "light" through and look at what comes out the other side. Shine a bright flashlight into your palm and notice that you see the light (filtered to be red) coming out the other side, with shadows for your bones and thick parts.

Re:Does anyone understand it? (1)

tqk (413719) | more than 2 years ago | (#39295861)

TEM is like an X-ray.

Thanks, all of you guys/people. "TEM" is something I'd never heard of before.

Re:Does anyone understand it? (1)

Taco Cowboy (5327) | more than 2 years ago | (#39282509)

People should read more about science and how it's done. It wouldn't be as scary to them if they did

True, people should read more about science

Just that the TFA is not only short on detail, and the info they carry kinda not sound right

Re:Does anyone understand it? (1)

gijoel (628142) | more than 2 years ago | (#39283003)

Science isn't magic with scary, unknowable stuff going on behind the curtain

He's angered the science gods. Get him.

Re:Does anyone understand it? (0)

Anonymous Coward | more than 2 years ago | (#39287643)

Seriously, how can this piece of ignorant rant be mod as insightful?

Re:Does anyone understand it? (1)

tqk (413719) | more than 2 years ago | (#39297579)

Seriously, how can this piece of ignorant rant be mod as insightful?

Compare it to any random AC rant, dick!@#$. YOU ARE SO BLOODY BORING! At least TRY to contribute something of ANY value. Gahd!

I'd rather be watching Serenity than reading your puerile pap BS anyday. Go play on MySpace if you've nothing better to do, FFS.

Re:holography? (1, Informative)

miknix (1047580) | more than 2 years ago | (#39280459)

from TFA:

The new method, called electron ptychography, dispenses with the lens and instead forms the image by reconstructing the scattered electron-waves after they have passed through the sample using computers.

Professor Rodenburg added: "We measure diffraction patterns rather than images. What we record is equivalent to the strength of the electron, X-ray or light waves which have been scattered by the object – this is called their intensity. However, to make an image, we need to know when the peaks and troughs of the waves arrive at the detector – this is called their phase.

"The key breakthrough has been to develop a way to calculate the phase of the waves from their intensity alone. Once we have this, we can work out backwards what the waves were scattered from: that is, we can form an aberration-free image of the object, which is much better than can be achieved with a normal lens.

I call it BS, there is no other way to measure phase than by interference. It seems they just reinvented holography indeed!

Re:holography? (4, Insightful)

deapbluesea (1842210) | more than 2 years ago | (#39280617)

I call BS on the summary. It says "The process has no fundamental experimental boundaries and it is thought it will transform sub-atomic scale transmission imaging". But TFA actually states "A typical electron or X-ray microscope image is about one hundred times more blurred than the theoretical limit defined by the wavelength. In this project, the eventual aim is to get the best-ever pictures of individual atoms in any structure seen within a three-dimensional object."

If they're measuring the wave diffraction as it passes through the atomic structure, then the diffraction limit is most definitely a "fundamental...boundary". If the addition of the word "experimental" means that they found no boundaries in their experiments, that just means they haven't gotten to the diffraction limit of the atomic aperture for those wavelengths yet (i.e. we're not even close to the fundamental boundaries, so we'll say our results are not limited in any way in our experiments). Either way, not a great way to talk about the results - too much sensationalism, not enough science.

Re:holography? (4, Informative)

suutar (1860506) | more than 2 years ago | (#39281429)

The phrase "no fundamental experimental boundaries" is in contrast to (in the actual paper) "However, to date all implementations of this approach have suffered from various experimental restrictions." The summary (and the article it summarizes) take it slightly out of context.

Re:holography? (1)

kaspar_silas (1891448) | more than 2 years ago | (#39280757)

Wrong! You can infer the phase by measuring the deflection angle due to the phase-shift. Naturally this doesn't work for normal angles of incident but the images are still dramatically improved.

Re:holography? (2)

sjames (1099) | more than 2 years ago | (#39281361)

And in turn, interference results in intensity differences arranged spatially. Thus, phase calculated from measured intensity.

It is certainly RELATED to holography.

Re:holography? (0)

Anonymous Coward | more than 2 years ago | (#39281833)

I think the thing you're looking for is interferometry. [wikipedia.org] (Although one might be able to consider holography as a specific optical application of an interferometric process. But also keep in mind that optical mice also use interferometry, but I don't recall anybody making a hologram with one - though in theory you could use one to produce an image with its sensor data.)

The news then isn't so much about the method, but rather about finding another application for it.

Re:holography? (1)

ceoyoyo (59147) | more than 2 years ago | (#39282147)

Yes, there is. You can measure the phase directly if the frequency is low enough. But the usual way, certainly with higher frequencies, is interference. Which is exactly what he describes - calculating the phase of the waves from their intensity alone.

From the article it sounds like they arrange for multiple diffraction images to interfere with each other.

Anonymous Coward (-1)

Anonymous Coward | more than 2 years ago | (#39280281)

Anonymous Coward revolutionizes first post with retina displays!

The Lytro of TEM (2, Insightful)

Anonymous Coward | more than 2 years ago | (#39280301)

Expect all sorts of imaging systems to evolve in this direction over the next few years.

It's more interesting for things like CAT and NMR, IMHO.

Re:The Lytro of TEM (2)

symes (835608) | more than 2 years ago | (#39280409)

It's more interesting for things like CAT and NMR, IMHO.

Tricorders?

Re:The Lytro of TEM (2)

kaspar_silas (1891448) | more than 2 years ago | (#39281227)

Electron imaging is only possible in vacuum and delivers massive doses typically to microscopic samples. So I doubt it will replace medical CAT or MRI scans any time soon.

Re:The Lytro of TEM (1)

ceoyoyo (59147) | more than 2 years ago | (#39282171)

nMR is already an interferometric process. I'm not sure how you'd use this in a CT scanner, or why.

Re:The Lytro of TEM (1)

kaspar_silas (1891448) | more than 2 years ago | (#39298953)

nMR measures the spectrum of RF emitted when nuclei excited into alignment by resonant RF pulses relax out of alignment with an externally applied magnetic field. MRI which is the correct name for the imaging modality measures the pattern of this RF emission. Maybe I am missing something but now exactly is this an interferometric process?

As to how this IS used in a research CT scanners google "phase-constrast CT". O and you want to do this in future to reduce patient dose or highlight soft-tissue boundaries which aren't obvious on a standard CT.

Re:The Lytro of TEM (1)

ceoyoyo (59147) | more than 2 years ago | (#39301047)

You're right, MRI (or nMRI) is nMR (Imaging). But the first poster said nMR and I wasn't feeling pedantic enough to contradict him. I really don't see how you'd use this at all if you weren't imaging.

In MRI you create an image by manipulating the relative phase of atomic nuclei with net magnetic moments. You measure the resulting interference for a bunch of different relative phases, then Fourier transform to get an image. It's interferometric imaging, except you're manipulating the phase instead of the sensor positions (as in radio interferometric imaging).

You're right, it does look similar to phase contrast CT. I'm not sure it's quite the same thing as they're doing here, but that's because the article on this technique isn't very clear.

Re:The Lytro of TEM (1)

kaspar_silas (1891448) | more than 2 years ago | (#39320545)

Okay take your point on the MRI. I'd describe that as phase encoding spatial information rather than interference but I accept your way is just as valid. It's certainly not the most common method in X-ray phase-constrast CT. However this method is used for X-ray CT at synchrotrons.

Re:The Lytro of TEM (1)

ceoyoyo (59147) | more than 2 years ago | (#39335053)

I wasn't aware they did interferometric CT at synchrotrons. Cool.

Phase encoding spatial information, interferometry, different words, but they mean the same thing. You are literally measuring interference, thus interfer-ometry. The only distinction is that in MR you get to manipulate the source, which is a little harder in astronomy.

About ten years ago there were some quite enthusiastic researchers who were trying to do super-resolution MRI. Some thought it was the best thing since phase encoding, others thought it was all bunk. They were both kind of right. I knew a grad student who was about to get an srMRI project dumped on her and she was a little unsure about it, so we looked into it carefully. It turns out that most of the srMRI experiments were just doing sync interpolation in a very convoluted (he he, literally) way.

In optical super resolution microscopy you acquire data in the image domain and to do super resolution you shift in space by half a pixel and then, from the two images, can reconstruct a higher resolution image. So the srMRI people were acquiring their data then shifting the object in space... which doesn't give you anything. srMRI DOES work, but since you're acquiring in the Fourier domain you need to shift in the same domain - i.e. apply a phase ramp in the image domain. And what you end up with is higher resolution in the Fourier domain - greater field of view in the image domain. We couldn't think of a use for a synthetically enhanced field of view and the noise characteristics weren't particularly good so we didn't pursue it.

The connection with interferometry comes because one of the srMRI researchers tried to coin the term synthetic aperture MRI. Synthetic aperture radar is (more or less) a kind of interferometry where instead of two receivers you have one, moving receiver. Of course, since MRI is already interferometry, if you were to actually do synthetic aperture MR (or two-receiver interferometry MR) you'd end up imaging in the image domain.

Re:The Lytro of TEM (1)

kaspar_silas (1891448) | more than 2 years ago | (#39336757)

I have done optical super resolution microscopy myself but have never heard about the MRI equivalent. Then again I don't really know much about MRI research so that's not so surprising and I obviously defer to your knowledge on this. Similarly I have seen synthetic aperture talks but only those done with Ultra sound or telescope based data.

Interesting now all the very different imaging modalities have vastly different implementation rates for similar techniques. Whilst the method and technology of acquisition is responsible for some of this I suspect a lot of it is researchers simply not knowing what is going on in other fields. (As I myself demonstrate with MRI)

Re:The Lytro of TEM (1)

ceoyoyo (59147) | more than 2 years ago | (#39346505)

"Whilst the method and technology of acquisition is responsible for some of this I suspect a lot of it is researchers simply not knowing what is going on in other fields."

Yes... but adding to that, I think a lot of researchers are so tied up in their own terminology (like phase encoding spatial information) that they have trouble recognizing the same or similar processes described in other fields. I had never thought of MRI as interferometry until I had to look into it. Now when I teach it to graduate students I throw up a picture of the VLA and take five minutes to talk about the similarities.

We've all seen the pictures of interference patterns from a double slit experiment. But did you ever wonder what exactly that pattern is? Optical interference is a Fourier transform, so that pattern is the Fourier spectrum of the image of the light source, convolved with the spectrum of the slits! (or something like that - it's been a long day)

Re:The Lytro of TEM (1)

kaspar_silas (1891448) | more than 2 years ago | (#39392691)

Couldn't agree more on the terminology. Eg phase-shift,interference,diffraction,scattering all used to describe similar things in different fields.
Yes I did wonder about double slit experiments (started in Atomic physics) but more so about the pattern's mere existence for single photons. The question of its shape seems trivial by comparison. :-) But thats for another board.

It's very easy with a system of computers (-1, Troll)

Anonymous Coward | more than 2 years ago | (#39280385)

Just like everything. You set it up to select women based on the attributes necessary to stimulate the breeding instinct in the males, since the female to male ratio will be very high, to repopulate the earth while in the caves.

Re:It's very easy with a system of computers (3, Funny)

squidflakes (905524) | more than 2 years ago | (#39281147)

So, are you predicting some sort of coal-mine gap?

Current users (3, Funny)

Pope (17780) | more than 2 years ago | (#39280415)

The Human League, Def Leppard, Heaven 17, ABC, Cabaret Voltaire and Pulp rejoice!

Re:Current users (1)

Jeremy Allison - Sam (8157) | more than 2 years ago | (#39282015)

I worked at Batchelors foods with Steve Singleton from ABC before they made it big. He saved me from being beaten up by the resident bully. It's a funny ole' world :-).

Jeremy.

The most important question: (4, Funny)

InsertWittyNameHere (1438813) | more than 2 years ago | (#39280431)

How do you pronounce "ptychography"??

Re:The most important question: (5, Funny)

SmurfButcher Bob (313810) | more than 2 years ago | (#39280549)

Exactly as it's spelled.

Re:The most important question: (0)

Anonymous Coward | more than 2 years ago | (#39281029)

There is allso correct French pronounciation with silent 'e'

Re:The most important question: (0)

Anonymous Coward | more than 2 years ago | (#39280587)

tie-COG-ruh-fee

Re:The most important question: (0)

blueforce (192332) | more than 2 years ago | (#39280597)

This is from Sheffield; the researchers are using Scottish Gaelic - looks like 'linoleum', sounds like 'floor'. In this case it's pronounced 'scatteredelectronwavereconstructor'.

Re:The most important question: (3, Informative)

Urban Garlic (447282) | more than 2 years ago | (#39280799)

The Sheffield that's pronounced "sheffield" is actually in Yorkshire, pronounced "yorkshire", which is where this research took place.

The Sheffield you're thinking of is the one that's pronounced "glasgow", and even there, you're more likely to run into Scots (a dialect of English, ye ken) than Scottish Gaelic, which is more of a highland thing.

Re:The most important question: (1)

blueforce (192332) | more than 2 years ago | (#39289703)

Ah, of course. There aren't any Mexicans in the U.S. just like there aren't any Scots in Great Britain. Thanks for clearing that up and missing the joke entirely.

Re:The most important question: (1)

K. S. Kyosuke (729550) | more than 2 years ago | (#39280921)

If it were in English, would it be pronounced "Throatwobbler Mangrove"?

Re:The most important question: (4, Funny)

Anne_Nonymous (313852) | more than 2 years ago | (#39280685)

>> How do you pronounce "ptychography"??

Choke on a crouton

Re:The most important question: (0)

Anonymous Coward | more than 2 years ago | (#39281839)

Fucking brilliant.
Well done Anne!

Re:The most important question: (0)

Anonymous Coward | more than 2 years ago | (#39280937)

The y's are silent

Re:The most important question: (1)

Alioth (221270) | more than 2 years ago | (#39285841)

My guess is that the 'p' is silent so it would be something like:

tie kog rafy

Re:The most important question: (1)

ed1park (100777) | more than 2 years ago | (#39289967)

like pterodactyl?

This is no revolution (-1)

Anonymous Coward | more than 2 years ago | (#39280481)

They should study more.

Pics... (0)

Anonymous Coward | more than 2 years ago | (#39280505)

... or it didn't happen.

Re:Pics... (2)

anyaristow (1448609) | more than 2 years ago | (#39281085)

We're so used to ignoring things that look like ads or links to other stories that we fail to notice the images down the column at the right are, in fact, the images we're looking for.

5 times improvement? (1)

mykepredko (40154) | more than 2 years ago | (#39280511)

Not to mention simpler preparation of samples.

To cap it off, I would expect that electron microscopy just got a whole bunch more accessible.

Well done - there might be a Nobel in it for you.

myke

Welcome Message (-1)

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Ptychography: great method, not new (5, Informative)

vincefn (705639) | more than 2 years ago | (#39280769)

The article implies that the method is new, which is not the case - in fact it even has its wikipedia page (http://en.wikipedia.org/wiki/Ptychography). The team (J. Rodenburg's) behind that press release is indeed among the pioneers.

The whole idea behind the technique is to illuminate the sample at different positions using an electron or X-ray beam, with an overlap between the different positions of the beam. Once this is done the algorithm reconstructs both the structure in the sample (the electronic density) and the structure of the probe (the electron or X-ray beam).

For those who can access articles behind paywalls :
[1] W. Hoppe, Ultramicroscopy 10 (1982) 187–198. http://dx.doi.org/10.1016/0304-3991(82)90038-9 [doi.org]
[2] B.C. McCallum, J.M. Rodenburg, Ultramicroscopy 52 (1993) 85–99. http://dx.doi.org/10.1016/0304-3991(93)90024-R [doi.org]
[3] P.D. Nellist, B.C. McCallum, J.M. Rodenburg, Nature 374 (1995) 630–632. http://dx.doi.org/10.1038/374630a0 [doi.org]
[4] P.D. Nellist, J.M. Rodenburg, Acta Crystallogr A Found Crystallogr 54 (1998) 49–60. http://dx.doi.org/10.1107/S0108767397010490 [doi.org]
[5] T. Plamann, J.M. Rodenburg, Acta Crystallogr A Found Crystallogr 54 (1998) 61–73. http://dx.doi.org/10.1107/S0108767397010507 [doi.org]
[6] J.M. Rodenburg, H.M.L. Faulkner, Appl. Phys. Lett. 85 (2004) 4795. http://dx.doi.org/http://link.aip.org/link/APPLAB/v85/i20/p4795/s1&Agg=doi [doi.org]

It's also used with X-rays (the last article is open access) :
[1] J.M. Rodenburg, A.C. Hurst, A.G. Cullis, B.R. Dobson, F. Pfeiffer, O. Bunk, C. David, K. Jefimovs, I. Johnson, Phys. Rev. Lett. 98 (2007) 034801. http://dx.doi.org/10.1103/PhysRevLett.98.034801 [doi.org]
[2] P. Thibault, M. Dierolf, A. Menzel, O. Bunk, C. David, F. Pfeiffer, Science 321 (2008) 379–382. http://dx.doi.org/10.1126/science.1158573 [doi.org]
[3] M. Dierolf, A. Menzel, P. Thibault, P. Schneider, C.M. Kewish, R. Wepf, O. Bunk, F. Pfeiffer, Nature 467 (2010) 436–439. http://dx.doi.org/10.1038/nature09419 [doi.org]
[4] C.M. Kewish, P. Thibault, M. Dierolf, O. Bunk, A. Menzel, J. Vila-Comamala, K. Jefimovs, F. Pfeiffer, New J. Phys. 110 (2010) 325–329. http://dx.doi.org/10.1016/j.ultramic.2010.01.004 [doi.org]

Re:Ptychography: great method, not new (0)

Anonymous Coward | more than 2 years ago | (#39281269)

so, it's basically just a CAT scan, using electrons instead of x-rays.

Re:Ptychography: great method, not new (1)

ceoyoyo (59147) | more than 2 years ago | (#39282193)

No, it's a diffraction imaging technique. A CT scan reconstructs internal structure based on rotating a source around an entire sample. This constructs a regular image, but without the need for a lens.

I love new technology but... (0)

blueforce (192332) | more than 2 years ago | (#39280771)

I'll wait for the 2nd or 3rd gen iScan so they can get the bugs worked out before I get one. I can get this from the Genius Bar, right?

original article (3, Interesting)

vossman77 (300689) | more than 2 years ago | (#39280847)

took me forever to find it, but here is the original article behind the Nature paywall

http://www.nature.com/ncomms/journal/v3/n3/full/ncomms1733.html [nature.com]

the paper feels like it written by the marketing department for his company.

Re:original article (1)

vossman77 (300689) | more than 2 years ago | (#39280961)

After reading the paper, they are definitely doing something novel, but the claims made in the paper far exceed what is being presented. Imaging bacteria cells is considered pretty easy -- show me some atoms.

Finally!!! (2)

M0j0_j0j0 (1250800) | more than 2 years ago | (#39280871)

We will be able to see that violin you talk about!!!!

Nice but not that nice (5, Insightful)

kaspar_silas (1891448) | more than 2 years ago | (#39280989)

Basically what they have done is phase contrast transmission electron imaging. This is quite an achievement in itself and well done to them. However they most certainly did not invent this "technique" (and I doubt they actually claimed that). The method is well known from X-ray phase contrast imaging research.

They even wrote this: "The technique is applicable to microscopes using any type of wave and has other key advantages over conventional methods. For example, when used with visible light, the new technology forms a type of image that means scientists can see living cells very clearly without the need to stain them, a process which usually kills the cells."
Em, yes but optical phase-contrast is damn well established. O and Frits Zernike who got the Nobel prize for doing exactly this in 1953 might be pissed off.

Re:Nice but not that nice (1)

squidflakes (905524) | more than 2 years ago | (#39281179)

I'll say. I've got optical phase-contrast technology in 4 of the 9 cameras currently in my house.

Re:Nice but not that nice (1)

Anonymous Coward | more than 2 years ago | (#39281673)

Well, this and most comments here seem to show that Slashdotters generally think that they understand something and then dismiss it as trivial (hint: most of the comments here completely missed the point). Ptychography generates images from the coherent scattering pattern of the object, and thus it requires no optics. The achievable resolution is limited not by the quality of the optical components, but by the wavelength of the radiation being used (and the time you are able to spend counting those electrons or photons that scatter to wider angles). The method requires (almost) fully coherent radiation, thus making it a bit more tricky than just regular phase contrast imaging.

Re:Nice but not that nice (1)

Anonymous Coward | more than 2 years ago | (#39282045)

O and Frits Zernike who got the Nobel prize for doing exactly this in 1953 might be pissed off.

I don't think he cares. He died in 1966.

Re:Nice but not that nice (2)

ceoyoyo (59147) | more than 2 years ago | (#39282247)

I don't think it's quite that simple. Their technique uses a type of interferometry to reconstruct the image - the imaging itself is done in the Fourier domain, which is definitely not the case for a phase contrast microscope. They also don't need lenses, also not the case in phase contrast microscopy.

Re:Nice but not that nice (1)

kaspar_silas (1891448) | more than 2 years ago | (#39298925)

It's not a type of interferometry as they don't measure phase-shifts directly. They measure the diffraction pattern and infer the phase-shifts that would result in such an image. Basically measuring the Fraunhofer diffraction pattern and computationally reconstructing a sample that would create such a pattern.

As such if the sample was a plane normal to the electron beam they would see nothing in this method. The imaging is not done in the Fourier domain thou the reconstruction can be if you prefer. For the imaging it is merely a standard electron imaging array which is why on their webpage they can show "The [diffraction] image before it is reconstructed using a computer"

You don't actually need a lens for phase constrast measurement. That is why it is possible to do exactly this method for hard X-rays for which reasonable lens don't exist. See the following for example: http://www.nature.com/nature/journal/v467/n7314/full/nature09419.html [nature.com]

Re:Nice but not that nice (1)

ceoyoyo (59147) | more than 2 years ago | (#39301085)

"It's not a type of interferometry as they don't measure phase-shifts directly."

Interferometry is traditionally done by looking at interference patterns (which is what a diffraction pattern is). That's why it's called interferometry. It's only quite recently that we've been able to (sort of) measure the phase of light at reasonably high frequencies.

Re:Nice but not that nice (1)

kaspar_silas (1891448) | more than 2 years ago | (#39320275)

That's not true. When a physicist (like me) talks about an interferometer generally we mean a device that can measure phase shift or relative phase by comparing a beam with unknown phase to a separate known phase-shift reference beam.
See: http://en.wikipedia.org/wiki/Interferometry [wikipedia.org]

Such interferometers (which normally use a point detector and therefore aren't measuring a pattern) have been about for well over a hundred years
See: A. Michelson, E. Morley. American Journal of Science: 333–345. (1887). So I simply don't know what you mean by "traditionally done".

Inferring phase-shifts from diffraction patterns is different (but obviously mathematically related) and more limited. For example a light beam going normally through a thin sheet of glass has no diffraction pattern. However it has a measurable phase-shift with an optical interferometer.

When you say we can only recently measure phase at high frequency for light I think I am missing something. If you are clever with the optics you can make all phase-shifts manifest as intensity variations. This is exactly the principle of a phase-contrast optical microscope widely available since the 60s.

Re:Nice but not that nice (1)

ceoyoyo (59147) | more than 2 years ago | (#39334773)

I should have been more clear. There are several different types of interferometry. The one you're referring to measures the relative phase between a reference beam and a beam that's had something done to it (passing through a substance or travelling a different distance). Michelson and Morley, as you point out, is probably the most famous example. They were measuring (or trying to measure) very small differences in the time it took two light beams to travel the same distance, in different directions.

A different type of interferometry measures the size (or can be used to form an image) of objects. It's what the various forms of radio interferometers do. The oldest example I know of is, interestingly, attributed to the same Michelson: http://en.wikipedia.org/wiki/Michelson_stellar_interferometer [wikipedia.org] . Note that the distinction here is that you make measurements at two (or more) different locations, combine the signals, and measure the interference pattern. You're not measuring what happened (or didn't happen) to the beam as it travelled, you're measuring things relating to the source of the signal. If you sample all the directions you end up with a Fourier spectrum that you can transform into an image.

A third type is synthetic aperture radar where you have one receiver but it's moving relative to the source. A fourth type is MRI, where you manipulate the phase of the source and measure... etc.

In your OP you asserted that what the researchers in the article are doing is the equivalent of phase contrast microscopy. It's not. Phase contrast microscopy, as you point out, is the first type of interferometry - measuring what happened to the beam as it travelled. What they're doing in the article appears to be (roughly) the second type - imaging the source of the signal via interferometry. A tipoff is that in phase contrast microscopy your signal is formed in the image domain - you can look into the microscope and see the image. In a radio or optical interferometer, or in this application, the signal is in the Fourier domain - you have to transform to get an image.

When I said that we can only recently directly measure (sort of) the phase of light, and only for low enough frequencies, I meant just that. All the types of interferometry we've both mentioned normally work using interference. In the first case you combine two beams of light and they interfere, giving you a measure of the relative phase. In the second, you combine signals from two spatially separated receivers and they interfere, giving you a Fourier spectrum (and thus a more complicated measure of relative phase). Recently, as in, not in Michelson's time, if the signal is low enough frequency you can use electronics to measure the phase directly - a 60 Hz household electrical supply, for example. You don't need to cause two signals to interfere, you just measure the phase directly. Even more recently, radio astronomers who wanted to put their telescopes so far apart it was impractical to run a cable between them have figured out how to directly (sort of) measure the phase of higher frequency signals, allowing very long baseline interferometry (VLBI): http://en.wikipedia.org/wiki/Very_Long_Baseline_Interferometry [wikipedia.org] .

So basically, when you said "it's not a type of interferometry as they don't measure phase-shifts directly" I didn't realize that you weren't familiar with the second type of interferometry and assumed you meant it wasn't interferometry because they didn't directly measure the phase, but instead used interference to indirectly measure it.

Re:Nice but not that nice (1)

kaspar_silas (1891448) | more than 2 years ago | (#39336879)

Ah okay, I understand what you mean now. However I still think your wrong as whilst you can measure phase of photons in the RF/Microwave domain there is no method of measuring phase directly with optical photons never mind 100keV electrons.

Indirectly by observing the imaging pattern (like a classic optical fringe pattern) the phase-shift can be done. Thou you might have to manipulate the beams to make the pattern more obvious as in classic interferometers or classic phase-contrast microscopy. Or you can look from "far" enough away so that the scattering from the phase-shift is enough to produce an image from which you can infer the phase-shift itself. This is the technique the Sheffield electron folk, some telescope folk and the X-ray folk can use. There is actually a smooth continuum of techniques depending on how far away your detector is, now transparent you object is and now you block or deal with the transmission image that "contaminates" the pure scatter/phase-shift image. But lets ignore the other fields for now as this is a semantic debate.

In this particular case they are not measuring the phase of the electron wave. They use a Gatan, Inc. ORIUS SC200 CCD Camera. Such a detector doesn't even detect the electrons directly. Instead it detects the 10 or so optical photons emitted from the scintillator placed in front of a CCD when each electron strikes it (the optical photons are of course emitted with random phase). So all they can possibly detect is an electron intensity profile. As this is a far field diffraction pattern you can mathematically reconstruct the sample that would produce it.

They themselves point on page 2 left column that this technique has been about for 40 years in the optical world and admit X-ray researchers have looked into it before.

Re:Nice but not that nice (1)

ceoyoyo (59147) | more than 2 years ago | (#39346611)

I'm not sure if you think I'm wrong or you think I'm right but misunderstood what I said. I do not think it's possible, at this time, to directly (i.e. without causing two signals to interfere with each other) measure the phase of high frequency waves, EM or electron. IIRC people are starting to talk about doing direct phase measurement (sort of) with infrared. If you do think it's possible, and know of an example, I would be very interested to read about it.

The Sheffield people aren't measuring the phase of the electron wave directly (as you said). They're measuring relative phase using interference by arranging for multiple images from the scattering to interfere with each other, a la classic interferometric imaging. That's why their raw image is a Fourier spectrum.

I don't know the details of what they're doing, it's definitely not my specialty, but they are definitely not doing an EM version of optical phase contrast imaging as described by Zernike.

Re:Nice but not that nice (1)

kaspar_silas (1891448) | more than 2 years ago | (#39392641)

Okay sorry my mistake I thought you meant a direct phase measurement.

IMHO they are exactly doing a classic optic phase-constrast technique. Not exactly the same geometry as in microscopes due to the vastly superior optical beam available. But very similar and identical to the one often used for accelators X-ray CT which is why they reference this research. If you think this is wrong thats fine, I just disagree.

Re:Nice but not that nice (1)

kaspar_silas (1891448) | more than 2 years ago | (#39299165)

Saying you don't need a lens is just wrong. At the very very least you need a lens to focus the beam onto the specimen.

O and if you actually read the paper you'll see that on the right hand column of page 5 all the current experimental limitations on resolution are listed. That the lens doesn't feature doesn't mean it follows that it is just down to wavelength, it's not. There is no lens in any hospital X-ray systems and your 100 keV diagnostic X-rays does not give you ~0.01nm resolution images. There is a world of difference between physics based resolution limits and that which can actually be obtained in most cases.

The method is nice, worthy of a nature paper and will improve on the future. However those that are saying that this is it "they got this" for imaging are just plain wrong. It's a new imaging modality we get one every couple of years or a few a year depending on your definition.

Coming soon to a TSA booth near you! (2)

snikulin (889460) | more than 2 years ago | (#39281041)

We want to see your electron clouds

Finally! (0)

Anonymous Coward | more than 2 years ago | (#39281667)

A development where the phrase "a quantum leap" in advancement would be appropriate!

Goody Goody Gumdrops! I want one! (1)

lexsird (1208192) | more than 2 years ago | (#39281743)

Of course, who wouldn't? Looks like a lot of fun, not to mention we might have some scientists in some fields make some discoveries. If we have any scientists, do we still do that or did we outsource?

So the flow is... (1)

nko321 (788903) | more than 2 years ago | (#39282125)

"...has been constrained by the relatively poor lenses which are used to form the image. The new method, called electron ptychography, dispenses with the lens and instead forms the image by reconstructing the scattered electron-waves after they have passed through the sample using computers"

So while the old way had the electrons go through a "lens", they now go through a "computer."

I have this vision in my head of people looking through PC chassis and hoping to use it in place of a lens. So, what type of sensor IS being used? (No, didn't RTFA).

Re:So the flow is... (0)

Anonymous Coward | more than 2 years ago | (#39282317)

So, what type of sensor IS being used?

Whatever type of sensor they normally use, except now there's no lens in front of it.

TEMs in the 1980's... (2)

t4ng* (1092951) | more than 2 years ago | (#39282251)

I was a field service engineer in the 1980's for an electron microscope company. I read TFA and I have no idea what the hell they are talking about. After an installation of a sufficiently high voltage TEM I used to take atomic resolution images to prove the thing was working. And diffraction imaging is extremely common. The only thing I can think of that this might improve is TEM imaging at low voltages. As the accelerator voltage of the electron beam decreases, the field strength of the electromagnetic lenses needs to be decreased to bring everything into alignment and focus. Because of that, noise has a greater effect on the system which effectively reduces resolution. If this process involves any physical movement or integration of multiple images over time, it will never produce an atomic resolution image.

Re:TEMs in the 1980's... (1)

t4ng* (1092951) | more than 2 years ago | (#39282431)

Ah! Read the article on Nature.... That's exactly what they are doing. They are trying to get atomic resolution images at 30KeV, which is pretty amazing. Back when I worked on TEMs, you needed a minimum of 400KeV to get a decent atomic resolution image.

Re:TEMs in the 1980's... (0)

Anonymous Coward | more than 2 years ago | (#39287795)

you read TFA and you had no idea what the hell they were talking about. That's why you were only a service man.

You iNsensitive 3lod? (-1)

Anonymous Coward | more than 2 years ago | (#39284123)

Data recovery? (1)

detritus. (46421) | more than 2 years ago | (#39298483)

Given electron microscopes are already used for data recovery of mission critical hard drives, it makes me wonder if this discovery has any effect on DOD drive wiping standards.

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