There are many reasons that someone might want to use night vision goggles. They are great for hunting, for example, and they can have law enforcement or security uses. They’re also a lot of fun just to play with if you like camping or exploring.
Night vision devices, in their most basic form, were first created for actual field use during World War II, and they became more commonplace during the Vietnam War.
The first practical devices were used by the Germans in 1939 – they were based on devices that AEG developed a few years previously. The first infrared night-vision products became popular in 1943, when telescopic range fingers, and Nacht Jager night-vision devices were mounted on the Panther line of tanks. From there, other forces involved in the war started working on night vision devices too. The Germans eventually deployed the Vampir – a man-portable version of the night vision technology which was suitable for use with the Sturmgewehr 44 assault rifle.
Over time, the technology used in night vision goggles has improved a lot. Third generation systems were based on MCP which was also used in Gen II, but the photocathode is made from gallium arsenide, which helps to improve image resolution. The MCP has an ion barrier film, which helps to mak the tube last longer. There is one downside to the ion barrier, though – it allows fewer electrons through it, which means that there is a bigger halo effect around light sources and bright spots in the field of view. However, light amplification is improved significantly.
Photons from a low quality light source enter the objective lens in the goggles and then strike the photocathode. The photcathode will release electrons, which are accelerated, and this allows the higher-voltage microchannel plate to amplify the light. Electrons are drawn to a higher-voltage screen of phosphor, and when they strike the phosphor this causes it to release photons, which can be sen through the eyepiece.
The US Arm’s Night Vision Electronic Sensors Directorate includes naming conventions for different types of night vision technology, according to their ‘generation’. The current high performance goggles are GEN-III OMNI-VI-VII, but the Army has not given permission for any components to use the name ‘GEN-IV’.
There are a few key differences between GEN-III and the OMNI-V-VII improvements – one of the main ones being the presence of a system which regulates the voltage sent to the photocathode, allowing the unit to adapt to changes in light conditions pretty quickly.
In the consumer market, this system is classed as being Generation 4, but the military thinks of it as third generation, because it still uses Autogated tubes. Autogating power supplies can actually be added to any of the previous generations of night vision goggles.
The modern ATG function is designed to allow for better resolution and contrast even in rapidly changing conditions. ATG is an interesting feature which constantly operates, and which will help to protect the user from potentially being blinded if they go through a rapid day-night-day transition, or if a dark room is suddenly illuminated. ATG can also help to reduce the temporary blindness that you might have to worry about in flame bursts, or shootings – which are something that could be a concern in a military or security application.
During the 90s and early 2000s, there were some significant improvements made to the quality and resolution of night vision googles, and today they offer very good clarity, but there are still a lot of things that could be improved with them, and consumer grade units are not quite as good as the military ones.