'Adaptive optics' come into focus

A technology called adaptive optics is slowly finding its way into consumer electronics and optometrists' offices. The BBC's Jason Palmer reports from the annual meeting of the American Association for the Advancement of Science, where researchers outlined how the approach is revolutionising their work.

Representation of how ESO's Very Large Telescope uses adaptive optics (Image: ESO) The idea of "adaptive optics" has been embraced by a range of scientific applications, not just astronomy

Back in 1953, Horace Babcock had an idea.

As an astronomer, he was toiling with the problems caused by the Earth's atmosphere.

Light could come from the farthest reaches of the cosmos, billions of light years, and then get impossibly muddled up in the last couple of hundred kilometres as it passed through the turbulent gases that envelop the Earth.

So he came up with the idea of adaptive optics: figuring out just how the atmosphere muddled up the light, and subtly changing the shapes of optical elements like mirrors to perfectly undo those effects.

It all looked good on the back of the proverbial envelope, but in Babcock's time it would have been a Herculean technological task.

It took the US defence industry - and a purported $1bn - to put the idea into practice in the 1970s and 1980s. They were trying to get ever-better satellite pictures - sort of the astronomer's problem in reverse.

This week at the American Association for the Advancement of Science (AAAS) meeting, one session is showing how far adaptive optics has come.

"The idea is terribly simple," Christopher Dainty, a physicist from the National University of Ireland, Galway, told the meeting.

"It's like taking a crinkled crisp and flattening it without it crumbling, taking those distortions out of optical wavefronts... but some of the applications are tremendously demanding."

Among civilian pursuits, adaptive optics first returned to its ancestral home, taking hold in the European astronomy community. By now, Professor Dainty told BBC News, the gain of resolution that adaptive optics provides makes its use a foregone conclusion.

Start Quote

Every time we set a patient down in front of the system it's the first time we're seeing their disease with that kind of detail”

End Quote Joseph Carroll Medical College of Wisconsin, Milwaukee

"You would not dream of building a large telescope now without adaptive optics; there would be no scientific justification," he said.

"The difference is just staggering - it's almost like a blind person being able to see."

But the approach is finding its way into more and more avenues of research, and a simple version of it has found its way already into a consumer product.

Professor Dainty told the meeting that one make of DVD player has an adaptive optics element in it, to correct for distortions from the disc and anything that may be on it.

"They make a million a month, and they cost much less than a dollar," he said.

Mapping the mind

Eric Betzig, of the Janelia Farm Research Campus of the Howard Hughes Medical Institute, described how his research looking through brain tissue is a different matter than telescopes and DVDs.

Scientist Eric Betzig uses adaptive optics in his research into deep tissue imaging

"The atmosphere... doesn't scatter much light - largely it's transparent and you see stars many light years away. In microscopy, if you're looking into brain tissue, it basically to your naked eye looks like tofu," he told BBC News. "So trying to create an image inside tofu isn't necessarily an easy thing to do.

"With the adaptive optics, we bend each of the rays to make sure that they come together at one point to create a perfect focus, to allow us to image both deeply and with high resolution."

Dr Betzig's work can image single neurons in 3D, deep within mouse brain tissue - using them to piece together the circuit diagram of what he terms the "Pentium processor" that is the whole, functioning brain.

So far, adaptive optics techniques have allowed Dr Betzig and his team to image through about a third of the thickness of the mouse brain's cerebral cortex.

"Our goal is to really try to get the adaptive optics good enough that we can see throughout the entirety of the cortex and see the circuit," he said.

Joseph Carroll, of the Medical College of Wisconsin, Milwaukee, is looking at a different kind of single cell - the cells in the retinas of human eyes.

Medical researcher Joseph Carroll uses adaptive optics in his quest to improve eye disease diagnosis

Just like the atmosphere, the human eye creates a mish-mash of the light that passes through it; Dr Carroll reminded the meeting that the 19th-century physicist Hermann von Helmholtz said that if he had ordered an optical component and a human eye showed up, he would have sent it back.

As a result, detailed studies of the back of the eye have until now been difficult; with the benefit of adaptive optics, however, individual retinal cells - "rods" and "cones" - come into view. It is a boon for the science of ophthalmology, Dr Carroll explained to the meeting.

"When you go to an eye doctor, they usually rely on you to tell them how good your vision is - that's pretty silly. We want something more quantitative, more objective in order to measure what's changed in a person's retina."

Speaking to the BBC, Dr Carroll described how adaptive optics has transformed his work.

"Every time when I look into a retina now with adaptive optics, I'm the first one to see the cells in that retina, every single time it's a discovery because we just didn't have the technology before to see disease or even the normal retina on that scale.

"Now, every time we set a patient down in front of the system it's the first time we're seeing their disease with that kind of detail. Every single day its exciting to see that."

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