QMC adapts astronomical sensors for terrestrial use

The technology, which is being developed by QMC Instruments, was originally used in space telescopes such as Plank and Herschel to peer into the far corners of the universe.

It focuses on terahertz radiation, the far infrared and microwave portion of the electromagnetic spectrum that astronomers use to study the Cosmic Microwave Background and dust clouds where stars are born.

In the past decade or so there has been increasing interest in producing and detecting terahertz radiation from terrestrial sources. Indeed, the latest generation of airport body scanners emit terahertz radiation at a defined frequency, which passes through clothes and to a lesser extent the body, but not metals.

However, the latest technology differs in that it is entirely passive, and is able to detect small amounts of terahertz radiation from endogenous sources such as the human body and certain objects such as explosives — essentially acting like a video camera, viewing the contrast in real time.

‘Astronomers are only interested in one thing and that’s sensitivity, so if you’ve got fabulously sensitive detectors you can do passive imaging if you’ve got the right combination of technologies, which is what we’re putting together,’ said Ken Wood, an astronomer by training, who is now a director at QMC.

As well as unprecedented sensitivity, there are a number of other advantages, including the negation of safety concerns (since no external radiation is actually emitted) and the ability to finely tune the camera to detect specific terahertz frequencies corresponding to certain objects of interest while blocking others.

The team has now built a demonstrator, dubbed KIDCAM, although there were significant challenges to replicate the sensors on board Plank and Herschel, which are cryogenically cooled to temperatures close to absolute zero (-273°C) to prevent internal interference.

‘If you want to hear a pin drop in the Albert Hall you don’t go on the last night of the proms — you have to quieten things down and that’s what you’re doing by making things cold,’ Wood said.

The team managed to create a closed-loop system using electrical cooling that does not require a constant supply of liquid gases pumping through the device.

As well as more obvious applications such as security, the KIDCAM could have uses in processes such as quality control in manufacturing processes.

’What normally happens in industry is when materials are mixed or a device is made, in order to check that the process is working properly they have to take materials out of the line process and analyse them separately — KIDCAM would be able to identify homogeneity and underlying structure,’ Woods said.

Also, since cancerous tissues seem to have a subtly different terahertz radiation signature to normal surrounding tissues, it could be used in diagnosis.

‘I’m pretty sure somewhere there’s going to be a killer application, where a technique based on terahertz frequency shows a kind of information that can’t be got another way,’ Woods added.