All objects emit terahertz radiation

The ThruVision system could be deployed at airports, railway stations or other public spaces.

It is based on so-called "terahertz", or T-ray, technology, normally used by astronomers to study dying stars.

Although it is able to see through clothes it does not reveal "body detail" or subject people to "harmful radiation", according to the designers.

"It is totally and utterly passive - it receives only," said a spokesperson for Thruvision.

The portable camera, which has already been sold to the Dubai Mercantile Exchange and Canary Wharf in London, will be shown off at the Home Office scientific development branch's annual exhibition later this week.

Body glow

Unlike current security systems that use X-rays, the ThruVision system exploits terahertz rays, or T-rays.

This electromagnetic radiation is a form of low level energy emitted by all people and objects.

These are able to pass through clothing, paper, ceramics and wood but are blocked by metal and water.

The system works by collecting these waves and processing them to form an image which can reveal concealed objects.

"If I were to look at you in terahertz you would appear to glow like a light bulb and different objects glow less brightly or more brightly," said the firm's spokesperson.

"You see a silhouette of the form but you don't see surface anatomical effects."

In addition, the system does not involve any of the "harmful radiation associated with traditional X-ray security screening", according to the firm.

The company has made previous versions of the camera, but the T5000, as it is known, is the first that works both indoors and out.

The system exploits technology originally developed at the government owned Rutherford Appleton Laboratory (RAL) in Oxfordshire.

"Astronomers use T-ray cameras that can see through dust and clouds in space, revealing what lies beyond," explained Dr Liz Towns-Andrews, of the Science and Technology Facilities Council which runs RAL.

Other terahertz systems, developed by companies such as TeraView, are used to probe the structure of pharmaceutical compounds.