[Paleopsych] NYT: Using Advanced Physics to Find Concealed Weapons
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Thu Apr 14 18:50:48 UTC 2005
Using Advanced Physics to Find Concealed Weapons
April 14, 2005
By MATTHEW L. WALD
Three companies are racing to market a new form of technology for
detecting concealed weapons, using physics borrowed from radio
astronomy and manufacturing techniques from cellular phone makers.
The technology, called millimeter wave, is a new category of sensing
so unobtrusive that it seems like something out of "Star Trek."
Unlike conventional systems such as metal detectors, which sense
magnetic fields created by certain materials or objects, or X-ray
machines, which pass rays through objects, millimeter wave sensors are
passive and rely on detecting energy emitted by objects.
The energy the sensors look for is in an unfamiliar part of the
electromagnetic spectrum, different from the usual visible light or
infrared. At wavelengths of two centimeters to one millimeter, the
energy is much longer than light or infrared waves, and thus able to
pass through clothing and similar material. Human bodies radiate the
energy at a rate higher than metal, plastic or composite materials, so
those objects can be spotted under clothing, in silhouette.
The sensors have been successfully demonstrated in laboratories and
have been sold mostly to government agencies for evaluation.
With research grants from the National Institute of Justice, the
technology arm of the Justice Department, and from the Defense
Department and other federal agencies, three small firms - Brijot
Imaging Systems, Millivision Technologies and Trex Enterprises - are
working to manufacture portable sensor units.
"Millimeter wave imagery is remarkably well understood, but no one's
been able to build anything cheap enough and small enough to be
practical," said Brian Andrews, president and chief executive of
Brijot Imaging, which is a partner with Lockheed Martin, the giant
Mr. Andrews says his company has done just that, with a $60,000 box
that is supposed to be able to see from 5 to 45 feet, depending on the
lens attached. A computer scans the images and looks for anomalies
that could be weapons.
A second company, Trex Enterprises of San Diego, has a unit that sells
for $50,000 (so far only to government customers), and is working on a
hand-held version. Its chief technology officer, John A. Lovberg,
compared the technology to infrared technology, which is also
"passive," meaning that the sensor measures natural emissions rather
than bouncing energy off the object being observed, as radar does.
Infrared is used in a variety of settings, including military
Mr. Lovberg said that the technology mounted on cars or planes could
also help drivers or pilots see through fog or smoke. Millimeter wave
sensors, he said, can show "the difference between a road and a tree
and a metal street sign."
Millivision, of South Deerfield, Mass., is marketing a detector about
the size and shape of telescopes used by serious amateurs. The company
is partly owned by L-3 Communications, a major manufacturer of
scanning equipment. The potential market, said William J. Caragol,
vice president for business development, is "any entrance that you
pass through where there's a need for security."
"It expands," he said, "to every office building, stadiums - fill in
Millivision has a $60,000 device it has sold to government agencies
for testing, Mr. Cargol said. With L-3, it is developing a portal with
controlled-temperature conditions, for more accurate scanning. The
Millivision sensor, he said, can spot a ceramic gun that a metal
detector would miss.
The Justice Department expects to use the sensors as security tools
for courthouses and other buildings, but says they could also have
Over the last eight years, the department has given about $7 million
in research grants to companies working on millimeter wave
technologies. Sara V. Hart, director of the National Institute of
Justice, said in an e-mail message: "We want law enforcement and
corrections officers to be able to detect any weapon, such as a bomb,
gun, knife or nonmetallic weapon, from a safe distance. This would
enable officers to make immediate protection decisions to protect
themselves and the public."
She said that the technology could be "practical for use within the
next few years" and that her agency had bought several systems for
The energy levels detected by millimeter wave sensors are extremely
small - mere whispers of energy measured in femto-joules, or
quadrillionths of a joule. (A joule is the amount of energy of one
watt applied for one second.) Chips, which are used in the sensors to
process the data and run at speeds similar to the frequencies
involved, 80 to 100 gigahertz, are still quite costly to make. But the
machines that manufacture the chips have gotten cheaper because they
are closely related to the machines that make chips for cellphones.
Mr. Lovberg of Trex said that advances in electronics are making
millimeter wave technology more affordable. "Ten years ago, you
couldn't buy amplifiers in this spectrum," he said of the amplifiers
used in the sensors. But semiconductors made of gallium arsenide or
indium phosphide can run in the frequencies required, he said. Those
chips have been commercialized for use in other devices, and are now
available for use in millimeter wave technology.
Tom Byrne, a member of the executive board of the Center for
Commercialization of Advanced Technology, a public-private consortium
in San Diego that provided a $75,000 grant to Trex, said, "In the past
there was a lot of expense in the receiver because the signal is a
low-grade, weak signal, and that pushed the price up." But now, the
receivers are getting more sensitive, Mr. Byrne said, and that is
reducing the price and making the sensors potentially viable.
Some companies are working on "active" millimeter wave systems, which
are more like radar in bouncing energy off the person being studied,
Mr. Byrne said. In fact, low-power radar is already in use at some
airports to search arriving passengers. But radar systems raise
potential health concerns from exposure to the energy, and also
privacy issues because body parts are clearly visible. Active
millimeter systems could raise the same worries.
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