Head-Up Displays for Dual-focus contact lens

The Pentagon has put in an order for prototype contact lenses that give users a much wider field of vision.

The lenses are designed to be paired with compact heads up display (HUD) units - glasses that allow images to be projected onto their lenses.

Much bulkier HUDs are already deployed by the US Army and Air Force to superimpose data about targets and other status updates over users' views.

The tech could help troops enhance their awareness on the battlefield.

The iOptik system's developer, Innovega, told the BBC it had signed a contract earlier this week to deliver a fully-functioning prototype to the Pentagon's research laboratory, Darpa.

The US Department of Defense had previously funded part of the Washington-based firm's initial engineering work on the project.

"The new contract gives us an immediate opportunity to start prototyping and demonstrating elements of this new system," Innovega's chief executive Steve Willey said.
Multifocal
The lenses work by allowing the wearer to focus on two things at once - both the information projected onto the glasses' lenses and the more distant view that can be seen through them.

They do this by having two different filters.

The central part of each lens sends light from the HUD towards the middle of the pupil, while the outer part sends light from the surrounding environment to the pupil's rim.

 

 By building two filters into each lens, close-up and distant light sources are both in focus

The retina receives each image in focus, at the same time.

"Normally, for example, with a camera you focus on something distant or something close - but you focus on a particular spot," said Mr Willey.

"By wearing our contact lens you automatically have this multi-focus, or dual-focus, and you are doing something that humans don't usually do."

Augmented reality
The chief executive said he also hoped to license the technology to be sold to the public.

One suggested application would be to allow users to watch what appear to be big-screen 3D movies on their glasses - with a different image projected to each lens.

Other potential uses include augmented reality eyewear similar to that teased by Google in its recent  Project Glass demo, and a device to offer gamers a more immersive experience.
 
The lenses are still going through clinical trials as part of the US Food and Drug Administration's approval process, but Mr Willey said he was confident the tech should be available to the public towards the end of 2014.

E.Coli: UCLA Engineers create cell phone-based sensor

Researchers from the UCLA Henry Samueli School of Engineering and Applied Science have developed a new cell phone–based fluorescent imaging and sensing platform that can detect the presence of the bacterium Escherichia coli in food and water.

The engineers combined antibody functionalized glass capillaries with quantum dots (semiconductors often used for medical imaging) as signal reporters to specifically detect E. coli particles in liquid samples using a lightweight, compact attachment to an existing cell-phone camera.

The cost-effective cell-phone attachment acts as a florescent microscope, quantifying the emitted light from each capillary after the specific capture of E. coli particles within a sample.

By quantifying the florescent light emission from each tube, the concentration of E. coli in the sample can be determined.

E. coli can easily contaminate food and drinking water. It poses a significant threat to public health, even in highly developed parts of the world, and causes a large number of hospitalizations and deaths every year.

As few as 10–100 E. coli particles can kill the cells of the intestinal lining, destroy the kidneys and cause blood clots in the brain, as well as seizures, paralysis and respiratory failure.

This study illustrates the promising potential of a cell phone–enabled, field-portable and cost-effective E. coli detection platform for the screening of both water and food samples.

Authors of the research include UCLA electrical engineering postdoctoral scholar Hongying Zhu; UCLA electrical engineering undergraduate student Uzair Sikora; and UCLA associate professor of electrical engineering and bioengineering Aydogan Ozcan. Ozcan is also a member of the California NanoSystems Institute at UCLA.

More information: The research is published in the peer-reviewed journal The Royal Society of Chemistry and is available online at RSC Publishing

A breakthrough in superlens development: Cheap, simple

This is an illustration of Durdu Guney's theoretical negative-index metamaterial, which would be the heart of a perfect lens. The colors show magnetic fields generated by plasmons. 

The black arrows show the direction of electrical current in metallic layers, and the numbers indicate current loops that contribute to negative refraction. Credit: Durdu Guney

A superlens would let you see a virus in a drop of blood and open the door to better and cheaper electronics. It might, says Durdu Guney, make ultra-high-resolution microscopes as commonplace as cameras in our cell phones.

No one has yet made a superlens, also known as a perfect lens, though people are trying.

Optical lenses are limited by the nature of light, the so-called diffraction limit, so even the best won't usually let us see objects smaller than 200 nanometers across, about the size of the smallest bacterium.

Scanning electron microscopes can capture objects that are much smaller, about a nanometer wide, but they are expensive, heavy, and, at the size of a large desk, not very portable.

To build a superlens, you need metamaterials: artificial materials with properties not seen in nature. Scientists are beginning to fabricate metamaterials in their quest to make real seemingly magical phenomena like invisibility cloaks, quantum levitation—and superlenses.

Now Guney, an assistant professor of electrical and computer engineering at Michigan Technological University, has taken a major step toward creating superlens that could use visible light to see objects as small as 100 nanometers across.

The secret lies in plasmons, charge oscillations near the surface of thin metal films that combine with special nanostructures. When excited by an electromagnetic field, they gather light waves from an object and refract it in a way not seen in nature called negative refraction.

This lets the lens overcomes the diffraction limit. And, in the case of Guney's model, it could allow us to see objects smaller than 1/1,000th the width of a human hair.

Other researchers have also been able to sidestep the diffraction limit, but not throughout the entire spectrum of visible light.

Guney's model showed how metamaterials might be "stretched" to refract light waves from the infrared all the way past visible light and into the ultraviolet spectrum.

Making these superlenses would be relatively inexpensive, which is why they might find their way into cell phones. But there would be other uses as well, says Guney.

"It could also be applied to lithography," the microfabrication process used in electronics manufacturing.

"The lens determines the feature size you can make, and by replacing an old lens with this superlens, you could make smaller features at a lower cost. You could make devices as small as you like."

Computer chips are made using UV lasers, which are expensive and difficult to build. "With this superlens, you could use a red laser, like the pointers everyone uses, and have simple, cheap machines, just by changing the lens."

What excites Guney the most, however, is that a cheap, accessible superlens could open our collective eyes to worlds previously known only to a very few.

"The public's access to high-powered microscopes is negligible," he says. "With superlenses, everybody could be a scientist. People could put their cells on Facebook. It might just inspire society's scientific soul."

Guney and graduate student Muhammad Aslam published an article on their work, "Surface Plasmon Diven Scalable Low-Loss Negative-Index Metamaterial in the visible spectrum," in Physical Review B, volume 84, issue 19.

Converting Infrared radiation into visible light

Jeppe Seidelin Dam and colleagues at the Technical University of Denmark in Roskilde are developing a device that can convert infrared radiation into visible light. Attached to a digital camera fitted with an infrared flash, it could detect tumours by recording the telltale pattern of infrared light they reflect.

"This would allow a surgeon to quickly determine if the entire tumour has been removed before finishing an operation," he says.

At the heart of the system is a multilayered crystal of potassium titanium oxide phosphate in which the infrared photons from the object to be imaged interfere with photons from an infrared laser, also fired into the crystal. The interaction shifts the wavelength into the visible spectrum while preserving the image information, allowing it to be captured by a normal camera.

Mirror amplifiers

The idea was first explored in the 1970s, but improvements to methods for growing crystals since then have improved the resolution of the device 300-fold. By placing a pair of mirrors on either side of the crystal so that the laser light reflects back and forth, the team increased the odds of its photons interfering with infrared photons from the object.

"We pass the same photons through the crystal up to 100 times," says Dam. The crystal was able to capture an infrared panorama with a resolution of 200 by 1000 pixels, the team says.

The device could be placed in front of a digital camera lens like a filter, and be used to take thermal photographs or video. Shrinking it down to a size suitable for everyday use should not be difficult, says Dam. "These are basically the same components that are in green laser pointers."

While current infrared colour imagers need to run at -200°C and cost around $100,000, Dam says that an upconversion imager would run at room temperature and cost about $10,000.

Stefano Bonora of the University of Padua, Italy, calls the upconversion technique "really interesting" for its potential to generate infrared images at room temperature. Such detectors are lacking at the moment, he says.

Journal reference: Optics Letters, DOI: 10.1364/OL.35.003796

Capture a Rainbow in a Glass Lens

The rainbow trap is a gilded 4.5-millimetre-wide lens perched atop a gold-coated glass slide (Image: Vera Smolyaninova/Towson University, Baltimore, Maryland)

Oh, to catch a rainbow. Well, it's been done for the first time ever – and with just a simple lens and a plate of glass at that.

The technique could be used to store information using light, a boon for optical computing and telecommunications.

All-optical computing devices promise to be faster and more efficient than current technology, but they suffer from the drawback that signals have to be converted back and forth from optical to electrical. The ability to "slow" light to a crawl or even trap it helps, as information in the light can then be manipulated directly.

In 2007, Ortwin Hess of the University of Surrey in Guildford, UK, and colleagues proposed a technique to trap light inside a tapering waveguide, which is a structure that guides light waves down its length. The waveguide in question would use metamaterials – exotic materials that can bend light sharply.

The idea is that as the waveguide tapers, the components of the light are made to stop in turn at ever narrower points. That's because any given component of the light cannot pass through an opening that's smaller than its wavelength. This leads to a "trapped rainbow".

Gilded waveguide
While numerical models showed that such waveguides would work in theory, making them out of metamaterials remained a distant dream. Now Vera Smolyaninova of Towson University in Baltimore, Maryland, and colleagues have used a convex lens to create the tapered waveguide and trap a rainbow of light.

They coated one side of a 4.5-millimetre-diameter lens with a gold film 30 nanometre thick, and laid the lens – gold-side down – on a flat glass slide which was also coated with film of gold. Viewed side-on, the space between the curved lens and the flat slide was a layer of air that narrowed to zero thickness where the lens touched the slide – essentially a tapered waveguide.

When they shone a multi-wavelength laser beam at the open end of the gilded waveguide, a trapped rainbow formed inside. This could be seen as a series of coloured rings when the lens was viewed from above with a microscope: the visible light leaked through the thin gold film.