Since major combat ended in April, more than 40 American soldiers
have been killed by Iraqi insurgents armed with hidden weapons and
explosives. In many cases, such as Sunday's attack when a soldier
was killed while waiting to buy a drink, the assailants often strike
from among crowds of people.
But keeping soldiers and others safe from assassins hidden in a
crowd may eventually become a bit easier.
Rick Blum, a professor of electrical and computer engineering at
Lehigh University in Bethlehem, Pa., has been working with a team of
scientists that could give soldiers and police a set of X-ray eyes.
The setup uses two cameras. One camera takes normal digital
images while a separate camera uses a new chip called a
millimeter-wave (MMW) sensor.
The new sensor, based on MMW radar developed by the military,
emits very high frequency radio waves that can penetrate clothing
and walls to reveal metal objects such as guns and knives. The
resulting image looks much like an X-ray photograph.
While other researchers and companies are working to develop
similar -- and controversial -- concealed weapons detectors, Blum's
system goes a bit further that just revealing what's under a
The Best of Both Views
At the heart of the experimental system is a unique set of
computer algorithms or programming code, that analyzes the images
from both the MMW sensor and digital camera. The software is
optimized to compare matching regions of each digital image and use
only the best features and details of each.
The idea, says Blum, is that both visual and MMW images have
their own unique strengths and weaknesses.
"You need to look at each image and say, 'What am I trying to get
out of it?' " says Blum. "The visual image is better than the MMW
image at helping to identify exactly who they're looking at. But the
MMW image is good at revealing what's hidden but at the expense of
[other] visual details."
Since the software is designed to show only details that is found
in one image but lacking in the other, the results are stunning. An
operator sees not only a normal visual of what the video camera sees
but also any objects that are hidden from plain view. That makes it
much easier to identify a suspicious person in a crowd and direct
soldiers and police to pay attention to that particular person.
Before the system can become fully operational, Blum admits that
key issues still need to be worked out. Key among them: the MMW
With only two or three such sophisticated sensors built so far,
"the MMW is far too expensive," says Blum. "Right now, it's just not
As such, Blum is modifying his software to work with other types
of sensors including infrared, and so-called backscatter radar that
is currently being considered for use in airport screening systems.
And like those other screening systems, there remains the
question if such weapons detectors could be used in the United
States without violating laws against unreasonable search and
"The use of anything that is invasive for general purposes --
capturing everyone that comes in the scope of the technology --
really does raise the most serious questions," says David Sobel,
general counsel for the Electronic Privacy Information Center in
On the Move
Blum believes that the system could still find eventual use among
the U.S. military -- especially among forces deployed in
peace-keeping roles in other nations. By equipping troops with such
technology, soldiers would be able to spot potential enemies without
resorting to physical body searches and potentially alienating
"It would be great to be able to give this technology to police
and to military troops in Iraq," said Blum in a press release from
In the meantime, Blum is seeking additional funding from the
Department of Defense for further research and development. He hopes
that a portable prototype can be developed for field trials soon.