A professor in
Most of us will have spent some of our science lessons at school peering down a microscope, looking perhaps at dividing cells, leaves or sections of organs.
The moment when you look through the eyepiece can be like entering another world, one in which everything operates on a totally different scale.
That different sense of scale is possible thanks to the miscroscope's most important part: the lens. This precisely curved piece of glass is what takes the light coming off the specimen, however tiny, and focuses it on the eyepiece where you can see it at a scale that makes sense.
No lens, no microscope. Or so you'd think.
But a professor in
Rather than using a lens to focus the light from the specimen, it looks at how the specimen diffracts – or scatters – light shone through it on to a recording plane behind, before complex mathematical processing is used to create an image of the specimen.
The method is not just restricted to looking at light, either: it can also detect how electrons, X-rays or lasers are scattered by a specimen.
To understand how the process works,
"There's an object. I'm throwing some sand through this object. It hits the object and it's scattered to the ground," he says.
"Looking at this pattern of the sand on the floor, you can think about the particular object the sand hit. This is what the diffraction pattern tells you. From the footprint you can go back to [work out] what the object was. This is called phase retrieval."
In simple terms, this process of phase retrieval involves taking the basic, blurred image produced by the object – which in no way resembles the object itself – and processing it by using complex mathematical formulae called algorithms several times.
The scientist initially creates a rough guess of what the image looks like, and uses this as a reference point when processing the image. The processing continues until the picture that emerges is the same as the image that went in.
But why do away with the lens in the first place? According to
A key problem with lenses, he says, is that there is a trade-off between the level of detail that can be seen through the lens – the resolution of the image produced – and the amount of the specimen that can be viewed all at once.
Aberrations in the lens can require the use of expensive optical equipment, while traditional electron microscopes – which look at the scattering of electrons, instead of light, by a specimen – are held back by power-supply instabilities that cause variations in the energy of electrons, he says. These can affect the quality of the image produced.
Also, the staining that is often needed to highlight features of an object that is being viewed with a lens can be damaging to the specimen, particularly biological material such as cells. With FPM, no staining is needed.
"This is going to be another breakthrough in the field of microscopy. That's the potential it has," he says.
A whole specimen can be scanned, in great detail, at once, removing the need to take several pictures to create a detailed record of the whole object, something that can take several tens of minutes.
And the potential uses of FPM are many. Scientists can examine anything from biological specimens such as cells to crystalline structures – such as semiconductor wafers – to check for defects. Almost any nanostructure that scatters X-rays, electrons, lasers or normal light can be assessed.
The focus of
There are now companies trying to commercialise the techniques of FPM, although
"People may have to wait for some time, until this is ready on a table-top machine where this screening is done automatically and you get the image," he says.
Ultimately, FPM is likely to be of greatest use in research centres, rather than in facilities that screen large numbers of samples.
"You may not need this in normal hospital labs. They are not going into that much detail. [It is] more where such molecules are developed – pharmaceutical laboratories, like research-and-development institutions where research is taking place," he says.
"Where people need to see the structure, where they need to change the structure, to manipulate the chemical behaviour, the physical behaviour."
It is in research laboratories of the kind where ptychographic microscopy will probably prove most useful that many of tomorrow's scientific breakthroughs are likely to be made.
So although ptychographic microscopy is highly specialised, it could prove useful in helping science to progress, thanks in part to researchers such as
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OCTOBER 31, 2014
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