Night vision scopes see daylight
"OK, make sure you've got your glow in the dark armband, watch out for vehicles without any lights and don't cross that line, otherwise you might be shot."
So started a briefing at the Owning The Night Conference, an event held at the Bisley range in Surrey, showcasing the latest development in night vision technology.
The two-day event brought together members of the armed forces, military contractors and weapons researchers to a foggy and wet corner of Surrey.
On offer was a range of night vision and thermal-imaging equipment that developers hope will give the British armed forces an edge in night-time operations.
The former commander of British troops in Afghanistan, Col Richard Kemp, told BBC News that the development of night vision was of "critical importance" to the ongoing conflict in Afghanistan.
Night vision can turn the darkest scene into virtual daylight
"It's not so much about night fighting, it's about night surveillance.
"The Taliban do much of their mine laying and planting of improvised explosive devices (IEDs) at night, so the advantage of turning night into day is very necessary indeed," he said.
Night sights can be broken down into two main categories - thermal imaging and near infrared (IR) - both of which are in use in Afghanistan.
Thermal sights detect the heat signature produced by hot objects (people, animals, vehicles etc) while IR sights work on the same principle as our eyes, only they "see" light reflected off objects in the infrared spectrum, rather than the visible.
"The near IR, such as you get on night sights and security cameras, work up to 1.1 microns in wavelength, that's redder than we can see, and similar to that produced by a TV remote control," explained Dr Neil Bowles, a physics lecturer at Oxford University.
A micron is one millionth of a metre.
Infrared systems can be further broken down into active and passive systems.
"Active near-IR systems use a near-infrared source to illuminate the scene and then measure the reflected light using a detector array similar to the sort you find in an ordinary digital camera," said Dr Bowles.
"Passive IR systems use a range of technologies to sometimes amplify, but then convert the infrared image to one in visible light.
One of the pieces of kit on show at Bisley was LUCIE, a passive binocular system used by vehicle drivers and commanders in Afghanistan.
It operates in the near IR and allows the operator to see the environment as if it were daylight, albeit in green.
Looking down the business end of a sniper rifle, fitted with thermal sights
Infrared systems such as this rely on a vacuum tube with an active infrared pigment at one end and a visible pigment at the other.
"It uses the photo-electric effect to generate electrons at the infrared end of the tube and then a high voltage to pass them down the tube to where they hit a pigment that glows in the visible," said Dr Bowles.
Because passive IR systems don't require a light source, they can be used in an environment where a source could be detected by a hostile force. Instead they use moonlight or, in some cases, starlight, to illuminate the area and then see what is going on.
Where this becomes a problem is on a truly dark night: full cloud cover and no way of illuminating the environment.
This is when the thermal imaging systems, such as Qioptiq's Virpr-2, for sniper rifles, come into their own. Rather than using reflected light to view the terrain, these systems work by detecting thermal emissions (heat) from objects.
"You can get them to cover a range of wavelengths, depending on the type of material you use to detect the light in your detector array, but they all work in a similar way to a digital camera," said Dr Bowles.
"Typically they work in the 7-14 micron region, where most body heat is emitted and are traditionally more complex than active near-IR and image intensifiers."
The technology shown off at Bisley was part of the MoD's Future Integrated Soldier Technology (Fist) programme, a multi-nation project designed to improve the fighting capabilities of the infantryman by equipping them with the latest technology and equipment.
The project includes advanced clothing, communications and weapons systems. A complete Fist system is expected to enter service in the coming decade.