Night Vision: How Does It Work?

All night vision devices consist of several main parts: an objective lens, an eyepiece, a power supply and an image intensifier tube (Photocathode Tube). Night vision devices gather existing ambient light (starlight, moonlight or infra-red light) through the front lens. This light, which is made up of photons goes into a photocathode tube that changes the photons to electrons. The electrons are then amplified to a much greater number through an electrical and chemical process. The electrons are then hurled against a phosphorus screen that changes the amplified electrons back into visible light that you see through the eyepiece. The image will now be a clear green-hued amplified re-creation of the scene you were observing. That's the basic breakdown, but there are some major differences in price and practical application between the handful of generations of night vision technology. Here, we'll go through the technology and give you a brief summary of how it works.

GEN 1

Gen 1 technology is the oldest of the night vision tech, having been in use since the 1950s. It's anything but ancient historyGen 1 night vision devices are still being made to this day. GEN 1 optics utilize all the technology listed above, but are not particularly sophisticated compared to modern, higher-generation devices: image quality is average at best, and effective range is limited. The good news, of course, is that Gen 1 night vision optics are highly affordable.

GEN 2

Gen 2 is a major step up from Gen 1, and is primarily used by law enforcement or for professional applications. The main difference between a 1st and a 2nd generation unit is the addition of a micro-channel plate, commonly referred to as an MCP. The MCP works as an electron amplifier and is placed directly behind the photocathode. The MCP consists of millions of short, parallel glass tubes. When the electrons pass through these short tubes, thousands more electrons are released. This extra process allows 2nd generation units to amplify the light many more times then 1st generation, giving you a brighter and sharper image. Gen 2 also provides better maximum range and the ability to work passively without needing an infrared illuminator.

GEN 3

Gen 3 night vision optics add a sensitive chemicalgallium arsenideto the photocathode, which helps provide a brighter and sharper image over 2nd generation units. There are a number of different grades of Gen 3. For the sake of brevity, we'll only look at Gen 3+. Gen 3+ is the current standard of the US Military and Special Forces, and varies from standard Gen 3 is two distinct ways. First, an automatic gated power supply system regulates the photocathode voltage, allowing the device to instantaneously adapt to changing light conditions. The second is a removed or greatly thinned ion barrier, which decreases the number of electrons that are usually rejected by the standard Gen 3 MCP. Gen 3+ provides the ultimate in range, resolution and life expectancy.

WPT

It's not a generation, but WPT (or White Phosphor Technology) is a major breakthrough in night vision. Studies show that nighttime scenes appear remarkably more natural in black and white versus the usual green. B&W provides clearer information about contrast, shapes and shadows. WPT provides users with this natural B&W night vision image. Operators that tested units that use WPT reported a significantly better degree of detail, overall contrast, full moon similarity and range of shades. WPT provides more discriminating shades of intensity between white and black than between green and black resulting in better contrast and depth perception then when compared to green phosphor.

GEN 4

There isn't really such a thing as Gen 4, at least as far as military classification goes. Most Gen 4 is simply gated/filmless, much like Gen 3+.

So There You Have It.

That's the breakdown of technological generations in night vision. Of course, the subtleties are far too numerous to cover here, but we hope that this primer gives you a good idea of what each new technology brings to the table.