Scientists Develop Device for Image Compression

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Using a new class of artificial materials, scientists at Duke University have designed a sensor that compresses images far more efficiently than existing technologies like JPEG.

The materials, called metamaterials, have exotic qualities that bend light, X-rays and radio waves in unusual ways.

While they are barely a decade old, they are fast falling in cost and are expected to become commercially available beginning within two years for a wide array of applications, including radio communications, security and automotive safety.

In 2006, the Duke researchers made headlines by demonstrating that an "invisibility cloak" could be created by bending the light that strikes a metamaterial.

The researchers, at the Center for Metamaterials and Integrated Plasmonics, reported Thursday in the journal Science that their scanning sensor captures both still and video images while simplifying compression by integrating it directly into the sensor array.

A cost advantage of the new technology is that it permits image compression to be performed directly by the sensor hardware, rather than by the specialized hardware and software in use today.

Although the cost of optical sensors has fallen rapidly, automobile manufacturers have been searching for alternatives to expensive laser radar, or Lidar, to provide sensors that work in a range of natural light conditions, including night, dust clouds and snowstorms.

The current generation of airport millimeter-wave security scanners has gained popularity because they do not rely on X-ray radiation and its attendant health risks.

But they require an elaborate mechanical arm that sweeps around a passenger standing in a scanning booth.

"The drawbacks are that it takes time and adds a lot of expense because of complicated mechanical rotors," said the lead author of the Science paper, John Hunt, a graduate researcher at the Duke center. "We have been trying to replace the whole system with one that has no moving parts."

Although the design of metamaterial sensors might offer high compression ratios, Mr. Hunt said the real advantage lay in the potential for reductions in size. For example, he noted, even the most advanced planes and boats today use a mechanically steered dish antenna for radar. This requires setting aside a large space to swivel the dish.

"Our system could potentially replace that with a flat sheet wrapped onto the side of the fuselage," he said.

Another potential advantage is speed. Intellectual Ventures, established by the former Microsoft chief scientist Nathan Myhrvold, has started a company to develop communications antennas made from metamaterials.

The company, Kymeta, has said it will introduce an inexpensive high-speed satellite antenna as soon as the end of next year. Bill Gates, the Microsoft co-founder, is an investor.

Depending on the wavelength they are focused on, metamaterials are made with either printed circuit boards or semiconductors. The sensor elements can be laid out in a linear array or as a three-dimensional matrix.

If the elements are small enough, the materials can manipulate visible light; other researchers are exploring applications with both sound waves and seismic waves.

Metamaterials bend radiation more sharply than natural materials. One of their strangest qualities is the ability to create a structure with what scientists call a "negative refractive index" -- a behavior of light and other forms of radiation that is not found when light waves pass through materials like glass or water. They can be aimed in many different directions, or used in parallel to increase bandwidth.

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This article originally appeared in The New York Times.


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