Colour xray scanners.

April 13, 2009 4:15 AM

Teach me about the newer colour display x ray scanners used in security checkpoints.

What are these machines called, and where can I learn more about them?
What do the different colours represent? Will plastics be a distinctly different colour than organic matter? What sort of tips and tricks can be used to thwart such systems?

Assume, if necessary, that I am trying to bypass the security screening of an evil warlord in order to bring freedom and justice to the oppressed masses he is exploiting.

posted by Meatbomb to Technology (1 answer total)

The most common colour displays in airport scanners are CAT scanners. CAT is "computer assisted tomography", based on x-ray technology. Normally an X-ray gives a greyscale image, showing how opaque your luggage is to X-rays. Because everything in your luggage overlaps and may be at strange angles, it can be difficult to discern shapes in the overlapping white blurs.

All CAT does is apply false colour to the images so, instead of fading black>white, the images fade white>colour1>colour2>colour3. This makes it much easier for the operator to spot small changes in the brightness of X-rays between different areas of the image, so it's much easier to discern and recognise the shapes of whatever is in your bag.

So all that matters for this layer of security is how opaque your freedom-fighting tools are to X-rays. It's easy to make things more opaque (e.g. wrap them in tinfoil) or to disguise their sillhuettes (hide inside an opaque object). Making them more transparent can only really be done by making them thinner or changing what they're made of.

Because it's pretty easy to disguise stuff like this, I'd imagine that the operators are trained to be suspicious of large, completely opaque objects in people's luggage.
posted by metaBugs at 5:27 AM on April 13, 2009