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Technology Stocks : ADI: The SHARCs are circling! -- Ignore unavailable to you. Want to Upgrade?

To: Jim Oravetz who wrote (2769)	9/24/2001 12:13:03 PM
From: Jim Oravetz	Read Replies (1) \| Respond to of 2882

Detector limitations at front of airport security issues By Charles J Murray, Electronics Times Sep 20, 2001 (8:25 AM) URL: electronicstimes.com News that terrorists used knives as weapons in last week's US hijackings has raised questions about airport metal detectors, and highlighted the need for a security technology to recognise non-metallic objects. Experts say determined terrorists know the weaknesses of metal detectors and have the means to get around them. Security technology expert Gabriel Rebeiz, professor of electrical engineering at the University of Michigan, said: "You don't need to be a rocket scientist to know that metal detectors can't detect a ceramic knife. Most people who want to bring a weapon into an airport are well aware of this." Richard Huguenin, chief technology officer of millimetre wave imaging group Millivision, pointed to other ways of deceiving the detectors: "There are 9mm automatic weapons that can be easily altered. People buy them at gun stores and replace the metal parts with ceramics and plastics." Scanning the human body is distinctly different from examining baggage because the task must be done quickly and safely but without violating anyone's privacy. In this context, imaging systems that use millimetre waves head a list of technologies being examined. The systems operate at wavelengths between 1 and 10mm. Engineers have developed two types of devices. In one, millimetre wave receivers measure thermal emissions. The other illuminates the target with millimetre waves and measures the reflected signal. Systems that measure thermal emissions look at the natural 'black-body emissions' generated by any object above 0° Kelvin (absolute zero). "Your body emits a signature radiation in the millimetre wave range," said Huguenin. "If a person has a gun or knife tucked into their belt, that object will block the radiation emitted by the body." The contrast between the object and the body creates an outline that can easily be seen on a display. Such systems depend primarily on two parameters — temperature and emissivity. If the contrast between those parameters is high, the image is sharp. A human body and a metal gun give a strong contrast because the body's emissivity is high (about 90%) while that of metal objects is low (near 0%). And although the contrast between the body and a ceramic knife is lower, it is still sufficient for a relatively sharp image. Millivision offers a portable unit the size of a radar gun, a gateway scanner and a video surveillance-type camera unit, all based on millimetre wave technology. Each uses an electronic focal plane array to measure the amount of radio energy emitted by the source. "It's just like a camera except that it operates at very long wavelengths," said Huguenin. Such equipment contrasts with so-called active millimetre wave systems, such as those developed by Battelle Memorial Institute's Pacific Northwest National Laboratory (PNNL). The system uses an array of antennas that transmit and receive a millimeter wave. The array illuminates the target, captures data and builds an image. To deal with the large amounts of scanning data, the system employs eight Sharc DSPs from Analog Devices, operating in parallel. The DSPs, each with a peak performance rating of 120Mflops, yield almost 1Gflops of performance. During operation, the system can scan a person in 1 to 2s and create an image in 4s. Doug McMakin, a developer of the system and staff engineer at PNNL, said: "It's fair to say that we could augment, or even replace, a metal detector." But engineers say that replacing metal detectors could still be a long and arduous task. In addition to privacy issues, millimetre wave systems will be very expensive. A metal detector costs about $5000. A millimeter wave system could cost at least $50 000. PNNL engineers say their system might cost $100 000.