This article was taken from the June issue of Wired magazine. Be the first to read Wired's articles in print before they're posted online, and get your hands on loads of additional content bysubscribing online
Currently on trial at Heathrow airport, L-3’s ProVision scanner can see through layers of clothing to detect hidden items just a few millimetres wide. Yes, it’s controversial. But here’s what we can reveal.
How it worksA millimetre-wave scanner uses antenna arrays to transmit and receive high-frequency radio waves as they circle a subject -- dense materials such as metal will reflect more energy. The raw data is turned into a hologram that is examined for suspicious objects by algorithms. The holograms are then rendered into 3D figures for inspection. The process takes about seven seconds.
Imaging Sampling Unit (ISU)The unit processes data from the antenna arrays and reconstructs it in 3D. With the reflected energy data -- seen as a greyscale value, with brighter areas denoting materials of higher reflectivity -- the samples are digitised and passed on to the System Control Unit.
Antenna arraysDual antenna-masts rotate around the body, transmitting and receiving radio waves at frequencies between 24 and 30GHz. In this range, waves pass right through clothing but bounce off denser materials such as skin -- or concealed objects. Unlike X-ray scanners’ waves, those emitted by millimetre wave scanners cannot cause tissue damage.
System Control Unit (SCU)This quad-core computer assembles data from the ISU into a hologram. The image is rendered as a 3D figure after the automated threat detection algorithms have been applied. Earlier this year, a worker at Heathrow was warned after ogling a colleague’s hologram on a similar type of machine also being trialled there.
Automated threat detectionImage-processing routines identify suspicious objects by analysing more than 200 distinct features such as texture, an object’s outline and unexpectedly bright or dark areas.
Operator control panelThis LCD panel displays a stylised 3D model of the subject -- any areas of potential interest are highlighted in yellow.
<img src="http://cdni.wired.co.uk/674x952/o_r/ProVision Wired Cutaway Final.jpg" alt="Airport Scanner"/>
This article was originally published by WIRED UK
