Millimeter-wave imager safer, more accurate than x-ray method

Sciencenewsline : A new detector can sense knives hidden in packages, impurities in chocolate, and explosive powder in pieces of mail—all without the use of ionizing radiation. Called SAMMI, short for standalone millimeter-wave imager, the device can see through many nontransparent, nonmetallic materials, according to its developers at the Fraunhofer Institute for High-Frequency Physics and Radar Techniques FHR in Wachtberg, Germany. “It can even detect and monitor the dehydration process in plants and how severely they have been stressed by drought,” says Helmut Essen, head of the FHR’s millimeter-wave radar and high-frequency sensors department. When SAMMI is running, a conveyor belt moves a sample between two antennae that transmit 78-GHZ electromagnetic waves. The varying degrees to which different areas of the sample absorb the signal reveal the sample’s varying material composition. Currently in the development stage, SAMMI may one day be adapted, for example, to automatically inspect goods on industrial assembly lines.