First developed in 1935 by AEG, night vision devices have long been a key piece of kit for the military as they enable images to be viewed in low-level light. With goggles and other devices now becoming widely available on a commercial scale, the question about how night vision actually works, and whether it’s legal, is being more commonly asked. This article explains how.
Seeing in the dark can actually be achieved in one of two main ways, and neither involves eating any carrots.
The original night vision devices (NVDs) were used initially during World War II and enhanced the low-level infrared light that’s barely visible to the human eye. It focuses this light on the photocathode element of an image intensifier tube to amplify it by thousands of times. You can then view this image on a screen or through goggles.
Nowadays, this is a relatively inexpensive technique and is used in many infrared cameras and camcorders that you’ll find readily available from specialist shops.
Infrared light is actually a low-level form of radiation, generated from electromagnets. This has longer wavelengths than the light we normally see and is so called because it sits below red on the electromagnetic spectrum. For an infrared NVD to work, it is paired with an infrared illuminator, which provides a light source for the device to amplify and enhance images in the dark.
Another common technique used in these devices is thermal imaging, which doesn’t require any low-level light to exist, in order to work. Instead of light, a thermal imaging camera uses energy, or heat, to capture an image. These units are often used by the Police to track suspects at night as they can pick out the heat from a body even when it’s being concealed. Thermal imaging can cut through darkness, fog and even smoke, making it a hugely popular device for the emergency services.
Are these devices legal on a commercial scale?
A debate has been raging for a number of years now surrounding the legality of commercially available night vision devices. NVDs are designed to aid wildlife tracking, photography or nighttime hunting. However concerns over privacy and in particular snooping, or stalking, began to creep in as a genuine concern for many.
However it’s night vision’s use in conjunction with firearms that creates the most fear. NVDs are often paired with shotguns or rifles and have allowed users to stalk and shoot their victims under the protection of darkness.
Different countries adopt different laws for the use of NVDs as they are classified as a tool for military purposes. This means they remain illegal for sale and ownership outside of approved organisations and personnel.