There are several generations on night vision devices ranging from generation 1 to generation 4. The way in which night vision has evolved is shown below.
Devices via each generation may look similar, this is because the only real difference is the type of image intensifier tube that is certainly used. The actual difference for each type of generation are explained below:
Generation I
The oldest, least expensive and then the most popular type of night vision in the world. 1st generation units amplify the available light several thousand times creating a bright sharp image. 1st generation units all have the the same characteristics:
The image can be blurry throughout the edges – geometric distortion
When the unit is switched on, it will glow green for some time later
The unit will produce a high pitched whine when switched on.
Generation II
Better quality, brightness and quality than generation I units. Tube performance is measured in line pairs per millimetre (lpm). The greater the resolution the better the quality (also, the price).
Advantages over Generation I are reduced distortion a the edge of the field, screen has better contrast and resolution and better light amplification and improved tube life. 2nd generation units have a greater range of both detection and recognition, on average 50 to make sure you 75 yards improvement over 1st generation devices.
The differences between generation I and II units are the addition of of an micro channel plate (MCP). The MCP is an electron magnifier which is placed behind the photocathode. The MCP contains lots of short parallel glass tubes. When the electrons flow through the tubes thousands more electrons are released. This provides brighter, sharper image.
Generation III
3rd generation units are currently used by the military. In good conditions they may detect human sized objects over 200 yards away. Intensifier tubes for the military must meet or exceed uniform standards, the ones that do not are referred to as commercial grades. The best of these are identified as ‘commercial grade A’. These will often fall short of military specification in only one measurement. ‘Commercial grade B’ falls short of military specification in quite a few measurement.
3rd generation units differ from 2nd generation by the addition of gallium arsenide to the photocathode to generate a brighter and sharper image. Tube life has been improved by adding a ion barrier film.
Generation IV
4th generation devices are usually rare. These night vision devices were produced as an option for military use. The US military instead thought we would adopt Generation III units.
Generation IV units have the advantage of not being as affected to bright lgt as other night vision generations. This comes at the cost of reduced tube life.
Please go to How night vision works for a detailed explaination of the principles of Night Vision Devices
