New technology sees through objects

Researchers make progress with a technology that could one day be used to detect biological weapons in parcels, locate cancers, and see through fog.

Researchers in Europe have made advances with a new technology that could one day be used to detect explosives or biological weapons in parcels, locate cancers beneath the skin, reveal the state of wounds beneath dressings and see through fog.

As part of an effort sponsored by the European Space Agency, which works to bring the continent up to speed in outer-space research by coordinating multinational projects, scientists were able to take the first "photographs" using terahertz radiation. Researchers with the StarTiger project released on Tuesday images of a human hand taken through a 15 millimeter stack of paper, as well as pictures taken of the human body through clothing.

Terahertz radiation lies on the boundary between radio and light waves and is far more difficult to detect and analyze than either. But it's of huge interest for use in medicine, security, communications and the environment. In communications, for instance, the technology could theoretically carry wireless data at superfast terabit speeds (one terahertz is 1,000 gigahertz, and most current radio technology stops at around 100GHz, or 0.1THz).

Everything gives off terahertz radiation naturally, and like radio waves--but unlike heat or light--the waves can pass through some solid objects. Like light, it is possible to focus the radiation and create images as if the intervening material were translucent. Also, by analyzing the frequencies given off, the chemical and physical characteristics of the hidden object can be worked out.

The ESA originally investigated the radiation for sensing atmospheric and ground phenomena from satellites, but it's now examining ways that the new frequencies could be used here on Earth.

"We have recognized the huge potential in nonspace applications, and in parallel to exploiting the use of terahertz waves and the StarTiger technology in space, we have kicked off a commercialization study to identify the best way of transferring it into terrestrial systems," said Pierre Brisson, head of ESA's Technology Transfer and Promotion Office.

Terahertz radiation has wavelengths too short for normal radio antennae to pick up and too long for normal optical techniques, thus the band has been closed to experimenters and scientists. Until now, the only known user of the frequencies has been a species of moth. By using nano-engineering techniques to create micro-machined arrays of minute antennae, the StarTiger team created a sensor array that can image objects at 0.2THz and 0.3THz.

"The final version was an enhanced imaging system incorporating a two-color 16-pixel detector array that's the size of a postage stamp," said Chris Mann, the project manager at Rutherford Appleton Laboratories (RAL) in Oxfordshire, England, where most of the work was done. "The enhanced system delivered images that confirmed the nature of terahertz waves. An imager can show details of features under the skin, confirming the potential of this technique," Mann said.