A practical security system has to be small which means that the millimetre wave images have relatively low resolution. However, this has advantages: the millimetre wave pictures do not reveal the body in any private detail.

This millimetre wave camera uses a nodding mirror to build up an image from a line of detectors. With fewer pixels to collect, millimetre wave moving images can be recorded in real time and the system operates at walk-through speeds to minimise passenger inconvenience at airports etc.

Thus one way to deal with privacy concerns is to use a computer rather than a person to analyse the images, and give an alarm if a suspicious object is being carried

Here you can see how the threat object shows up as a dark region on the torso, blocking the body heat. the computer recognises this (blue man) and places an alarm box on top of the video image the alarm can be raised without a human operator ‘looking through’ clothing