Thinking about buying a night vision device? Understand how they work first of all!

You will get a grasp of technical stuff like how these instruments succeed in amplifying the available light at night, get help from the infrared illuminator and displaying the images on a phosphor screen.

Night vision devices come in goggles, scopes, monoculars and binoculars. In this article I will focus only on monoculars (only one objective lens) and binoculars. The only technology which will be considered, is the intro-level known as Generation 1. Generations 2-4 are highly sophisticated and used only in specialized niches, like the military and security.

What are night vision devices for? These devices are not for seeing objects at a distance; magnifying objects to make them look closer is not what they are for, although some night vision instruments do come with a magnification of up to 4x. Their aim is to make vision at night possible.

Enhancement of available light: Night sight depends on the little light that’s always available at night. Sometimes, when the moon is full, there’s lots of light; sometimes not that much. Then the stars make a contribution as well, or some artificial light somewhere. These instruments have a special tube by means of which available light is amplified enough for night vision.

There’s no moon and the stars are behind the clouds and you’re in the bush. A lot of commotion reaches your ears, but you can’t see a thing. Then you switch on the infrared (IR) illuminator and you can’t believe your eyes: A leopard has just made a kill and without the illuminator you would never have known. The IR illuminator is a must, since the amplifier alone cannot always do what you expect from a night vision device: See in the dark. Sometimes it’s simply just too dark to see anything, even with all the amplification the amplifier can manage. The amplifier + IR illuminator can enhance the light by 15,000 times, or even by up to 40,000 in the case of high quality instruments.

Why is the feeding raccoon you’re seeing green? Why is any image you’re seeing when viewing an object in the dark with your night vision device green? Well, it’s green since the image you’re seeing is a projected electronic image on a green phosphoric screen inside the device. So you’re not really seeing the feeding raccoon directly; you’re seeing it on this little screen, not knowing the difference. The fact that it is green has to do with phosphor, but luckily we benefit from that, since green happens to be the colour of all colours we see the most shades in. Images you see with a night vision device will never be in colour in any case, but look on the bright side: Either these green images, or nothing at all!

The phosphor screens are not forever, but they will last for 1500-2500 hours - which is an awfully long time for a non-professional user. However, this also means that you should think twice before buying a used device, unless you know exactly how the previous owner used it. In addition to this, wrong use could also harm your night vision device. Night vision devices are supposed to be used in low light conditions. They do their job with the help of extremely light sensitive components. They will suffer damage or lose useful life when used in daylight or when "overloaded" by strong artificial light like flashlights, headlights or spotlights.

A little problem with the image area: The quality of the image is directly related to the price you’re willing to pay. The more, the better the image. The reason for this is that the image tube can hardly be flawless and scattered black spots come from blemishes on the intensifier tube. The cheaper the price, the more the black spots and vice versa. The edges of the images could also be slightly distorted.

Summary: How a night sight instrument succeeds in using the little light available at night and enhancing that to present an image to the viewer, as well as how additional light can be produced with the IR illuminator, and how the images are not viewed directly but on a green screen of phosphor, all these fundamentals have been explained in this article, so you should now know how these type of instruments work. I have also warned against abuse or incorrect use, which boils down to using the IR illuminator when not needed. If this is done, the sensitive parts, which includes the screen, will definitely be damaged. If used correctly, the viewer should have many years (up to 2500 hours of use) of pleasurable use of a night vision device.