History of Thermal Imaging
Nearly thirty years ago a new technology was made available to firefighters. Thermal imaging, previously the preserve of high-end military programs - expensive, heavy and inflexible - clearly had a future in civilian markets, but could it be developed to the exacting requirements of fire and rescue services? Over two decades on, the benefits to fire and rescue services are well documented, with the count of people and property saved around the world steadily rising and new applications for thermal imaging emerging on a regular basis. So how did this technology develop and where is it likely to lead? Read on...
The Beginning
In the late 1970s a UK government''s Central Fire Brigade Advisory Council reported on assisting the vision of firemen in smoke. The report examined technologies that could help with the age-old problem of locating casualties and the seats of fires in thick smoke and correctly identified that long wavelength infrared radiation was almost unaffected by all classes of smoke. It was found that a suitable thermal imager would be able to "see through" smoke - almost as if it wasn''t there.
An ideal solution on the surface. In reality however, thermal imaging had been around for a considerable amount of time - but most of the systems were used by the military. This meant that they had been designed to be fixed to vehicles, aircrafts and ships and utilised detectors that had to be cooled down to very low temperatures to reach optimum performance. This meant that the systems were not only very bulky, but extremely expensive as well.
Luckily, a solution was in hand - a vacuum tube called "pyro-electric vidicon" or Pevicon™, which was originally designed for military applications. The technology had never reached the performance needed for a military system, but was both relatively cheap to produce and did not require cooling to operate.
At the time of the report, a handful of Pevicons™ were being produced per year and being sold to academic and research bodies -an interesting technology in search of real market applications.
In the early 1980s, e2v (then trading as EEV) developed a camera system based on the Pevicon™, which they successfully trialled in conjunction with a small number of UK fire brigades. However, the camera was still seen as something of a novelty, rather than the essential firefighting tool it was set to become.
So what changed?
The UK became involved in the Falklands conflict.
Images of Royal Navy ships with thick smoke billowing from them were seen around the globe. This smoke impeded the efforts of fire and rescue teams on board - and there is perhaps nothing so frightening as the prospect of a shipboard fire. Civilians and fire crews alike know there is little opportunity of escape, or the likelihood that the fire will burn itself out - something that is very relevant in the marine market today. Multiple sealed compartments can fill with smoke, hampering navigation through the ship and making the location of the seat of the fire a slow and time consuming process - time that isn''t available.
It was this urgent operational requirement that lead the Royal Navy to deploy the first cameras into shipboard use. They rapidly became an invaluable tool, helping to reduce losses due to fire both in peacetime and battle situations. Many of the other European and Commonwealth Navies quickly followed suit and late in the 1980''s - after serious damage was sustained by the USS Stark in a Gulf incident - the US navy and coastguard made the Pevicon™ based camera standard damage control equipment throughout the whole fleet. At last thermal imaging had started to become standard equipment in fire and rescue stations for military applications.
Although the Pevicon™ program had started to address needs in the civilian firefighting market, it was not until the early 1990''s and the saturation of the military shipboard market that major manufacturers once again turned their attention to this market. It became evident that while the military could easily justify the expense of a thermal imaging camera - setting this off against losses caused by fire - finding the funds to buy would prove more difficult for most of the world''s civilian brigades.
Where to?
The solution was a cheaper camera. e2v launched their Argus™ camera specifically designed for civilian usage at 70% of the price of the cameras supplied to the military market. The camera was of equal performance to the military units, and still based on Pevicon™ technology. It was, however, from the outset designed for volume manufacture and fast assembly, enabling substantial cost savings to be passed on to end-users.
Technology development
The next major milestone in the evolution of firefighting cameras occured in the mid 1990s with the commercial availability of a new range of solid-state detectors manufactured by Raytheon Corp. in the United States. These detectors were the result of many years and billions of dollars worth of investment, principally by the US government, aimed at producing lower cost and more flexible thermal imaging systems for military use. Although driven by military needs, most of these programs were funded on the "dual use" principle, meaning that usage for the detectors was envisaged both for military and civilian firefighting applications.
These new detectors are still in use today, and are called Focal Plane Arrays (FPAs). They take the form of a flat device placed behind the camera lens at the focal point. Unlike previous vacuum technology, these sensors have a discrete number of picture elements (pixels) - with the most common arrangement being 320x240. This format gives a total of 76,800 pixels, enabling the device to output a far clearer picture than was previously possible. It is noteworthy however that this is a long way away from the latest optical devices used in normal cameras, where 5,000,000 to 10,000,000 pixel sensors are common.
The availability of the new detector breed opened the market to competition, and today cameras for firefighting purposes are manufactured and offered by at least 10 different companies, principally from the UK and US.
Increased competition and volumes have also meant that the price of cameras has fallen dramatically in real terms over the last 10 years. This has resulted in the ever-increasing use of the technology worldwide and in different markets. Better images are now commonplace and improvements in electronics allow manufacturers to offer many additional features, enabling the camera to be a more flexible and useful tool. Today, remote video transmission, temperature measurement and digital zoom are common offerings, and innovations in the market place include colorized screens settings and image capture and download.
But what of the future?
Future advancements in thermal imaging camera technology are likely to be influenced by moves towards even smaller and lighter cameras meaning that the personal camera could become a reality. The personal camera could become small enough and cheap enough for every firefighter to have one as part of their basic kit, removing the need for a separate cameraman. The challenge with the personal camera is designing something that can be stored on the firefighters uniform neatly and easily when not in use, so that it doesn’t hinder a rescue where the firefighter needs both hands free.
Looking further into the future, the possibility of a ‘Heads-up’ display on the firefighters BA (breathing apparatus) mask is certainly a possibility. In this instance the visual would be transmitted from a miniature camera to the mask, projecting a colour image right in front of the firefighters eyes. The advantages to this technology are; that it would be hands free enabling the firefighter to use the thermal camera at all times, even when exiting with a casualty, there would be no cumbersome apparatus to attached to the helmet which has the possibility of falling off, finally the problem of constant adjustment could be removed as the mask would be in a fixed position on the face.
Another serious consideration for thermal imaging camera manufacturers looking to bring new products to market are the Environmental considerations that must now be undertaken. In Europe the Reduction of Hazardous Substances directive (RoHS), outlines the restriction of the use of certain hazardous substances in electrical and electronic equipment. This Directive bans the placing on the EU market of new electrical and electronic equipment containing more than agreed levels of lead, cadmium, mercury, hexavalent chromium, polybrominated biphenyl (PBB) and polybrominated diphenyl ether (PBDE) flame retardants. This means that all new Thermal Cameras have to be compliant with the RoHS directive. Although some manufactures are selling product under exemption, eventually all electronic and electrical equipment sold in Europe will have to be compliant. This directive, or forms of it are being introduced throughout the world. Japan and China have their version of the directive and in certain states in the USA this directive is being actively investigated. This directive was a major consideration for e2v when developing the Argus™4 and is the first compliant Thermal imaging camera.
Thermal imaging cameras have come a long way since they first came on the scene, they are smaller, lighter and the picture quality has improved ten fold. The camera of the future is yet to be decided, but one thing is certain, progress cannot be stopped.
