Night Vision History
Night Vision - Past, Present and Future
People have many requirements to see at night and powerful illumination systems have been around since the first lighthouse went into service at Eddystone Rock in 1698.
However, these systems were simply methods of illumination with the obvious, and sometimes very dangerous, drawback that everyone could see the source of the light.
For this reason it became vital that a solution be found for military use - a decisive advantage was to be achieved by gaining the ability to see at night without being seen.
In 1887, Heinrich Hertz first discovered photoemission, on which night vision technology is based. In 1905, no lesser person than Albert Einstein theoretically explained the principle - the release of electrons from a solid material due to energy put in to it from radiation and light.
Active Infrared Night Vision Systems
The breakthrough came about in 1936 when the first Active Infrared system was developed using a silver photocathode. These systems were very bulky and primitive by today’s standards, but at the time they represented a major military advantage.
Active Infrared systems continued in use until the late 1970’s in some countries, but NATO forces were phasing them out by the late 1960’s.
The main drawback of Active Infrared systems was that to operate they required powerful infrared lamps, which meant the range was restricted by the performance of the lamp.
In addition, although infrared is not visible to the naked eye (other than a very dull red glow if you are close to the lamp), a major problem would arise during covert operations where both sides were using Active Infrared systems, in that each side could see the light emitted by the others infrared lamp.
Therefore, you are back to square one.
With the source of the light easily identifiable the system was rendered virtually useless, and probably lethal, as you would only have to shoot at the lamp to take out the person using it.
Passive Night Vision Devices
It was at this point that new technology was urgently required and modern Image Intensifiers were developed.
The advantage of these systems was that infrared lamps were no longer vital, and for this reason they are referred to as Passive Night Vision devices.
However, all Image Intensifiers need some light to work because by their very nature they amplify the avail¬able light to give a visible image.
If an area is pitch black with no ambient light at all, no Image Intensifier will be able to function.
For this reason infrared illuminators still play an important role and will always enhance Image Intensifier performance, but at the expense of losing the covert capability.
Night vision ability can also be realised through the use of Thermal Imagers, which perform a similar function to Image Intensifiers, but with the big advantage of being able to operate in zero light conditions as well as fog, smoke, snow, etc., which is not possible with night vision devices.
The latest, most sophisticated thermal imaging equipment will locate people or vehicles in trees, build¬ings and through a variety of media.
Although there are methods to defeat them, doing so can be difficult and expensive.
Thermal Imagers obviously detect heat and not light energy and the images they produce are generally less well defined than those of an Image Intensifier.
As range increases the subject simply becomes a hot ‘spot’.
Although Thermal Imagers have been around for some time, the early devices required a cooling system, which was usually com¬pressed gas, and their size and weight restricted them to static observation and surveillance work only.
With the development of uncooled solid state models, they have become portable and a potential rival to the Image Intensifier.
However, a major drawback to Thermal Imaging is cost, with basic systems starting at around £10,000 and the military/police equipment at many times this.
Using Computers for Night Vision
There is one other area of development concerning night vision ability and this centres around the use of computers.
Increas¬ingly, developments in CCD technology are producing low light images of impressive quality. It is already possible to integrate and ‘build-up’ a visible picture but the problem here is that you do not get a real time image, giving a blurred and distorted picture if your equipment or subject is moving.
The technology also already exists where the system gathers whatever information it can on the subject being viewed and in low light conditions where it is information limited, will ‘fill in the holes’ to produce a full, if not completely accurate, image.
The Future of Night Vision
As for the future, it is certain that technological developments will allow the improvement of all the systems already existing, but it is also likely that systems will be combined and integrated into smaller, more efficient devices where two or more technologies can be alternated at the touch of a button.