Security screening at airports and railway stations could be streamlined using a new high-frequency radio scanner that automatically spots concealed weapons.
The scanner detects millimetre-wavelength radio waves reflected off a target and converts the reflected signal into a 2D image. Computer software performs a rapid analysis of the scanner imagery, searching for incriminating objects.
Millimetre-wave radiation passes through clothing easily and is absorbed and reflected by other materials to different degrees. This makes it well suited to security screening (see All-seeing scan spares your blushes).
It can be used to spot hidden handguns and knives, and even non-metal weapons such as ceramic knives. Until now, however, a human operator has been needed to pick out concealed weaponry.
The new system could therefore speed-up routine security checks by rapidly screening for hidden weapons, says developer Yvan Petillot, a computer vision researcher at Heriot-Watt University in the UK.
In tests, participants were asked to stand a few metres in front of a scanner developed by UK firm QinetiQ and turn through 360°. Some were also given a small handgun to hide beneath their clothes. The computer software was able to identify the gun based on its shape and track it across several successive frames using a statistical image processing technique.
Research team-member Emanuele Trucco says the system could have benefits over conventional airport metal detectors. “This can go further because it can say exactly what and where a metal object is without the need for a touch or strip search,” he says. Trucco also suggests that a computer scanner could be more reliable than some human operators.
The team also used the system to identify non-metallic weapons, although it was less reliable for this. “We can detect metallic objects very well,” Petillot says. “But ceramic knives are much harder.”
Petillot adds that newer high-frequency scanners could sharpen images and work at greater distances: “The hardware is advancing so I think that in around two years it could be possible to spot [ceramic knives] automatically, like we can with metal objects.”
Graham Smith, who works on millimetre-wavelength imaging at St Andrews University in the UK, says the approach shows promise. “It is amazing what you can see with millimetre wave,” he told New Scientist (see graphic).
But Smith says the Heriot-Watt University system will need to be fine-tuned to meet with stringent security screening standards. “I’m not sure they are specific enough to be as reliable as a metal detector yet,” he says.