How night vision works
"Illumination by means of an infrared beam" , phosphoric screen" and "How light is amplified at night" are subjects you will come to understand reading this article.When you think about these type of devices, you are looking at monoculars and scopes in the first instance, but you do get a few binoculars as well with this technology. Then you also get goggles, which is more for kids. Of the four available technologies only the most basic one (Generation 1) will be discussed. The other three are advanced, but too expensive.
Do you want to see objects in the dark? That"s what night vision monoculars/scopes etc. make possible. This is what they"re made for; not making things look closer than they are in real live, like binoculars do. However, you do get some magnification with certain models of night sight models.
So you would really like to see what"s making that noise among the trees, but it"s simply way too dark? Take up your night vision device and you cannot believe your eyes: A leopard has just killed an impala! Being able to see this is made possible by a special tube inside the night vision instrument, which has the ability to capture the little light there is (from the stars, moon or far-away house light), amplify it and present a vivid image to your eyes.
Infrared illuminator: All quality night vision devices have a trick up their sleeves. They provide extra light (infrared) when the available light is not enough to get a bright image. They do that with infrared illuminators (or accept supplementary IR illuminators). This illuminator casts a virtually invisible infrared ray at the object at which you are looking, the objective lenses of the binoculars pick up the extra (infrared) light along with the visible light which is available and this then results in a brighter image. Without this illuminator no night vision is possible when absolutely no light is available to amplify. All in all, the amount of light gain varies from 15,000 to 40,000 times, depending on the quality of the night vision device. The more light gained, the brighter the image.
Green screen: All night sight devices have a little green phosphoric screen on which you see (through the eyepiece) what"s going on in the dark. So what you"re actually seeing, is not the object itself, but a projected and amplified electronic image of what"s going on outside in the dark. But you won"t worry, since without it no vision is possible. The image that you see is not in colour; it"s in shades of green. Why green? This is interesting. The human eye can distinguish more shades of green than any other colour.
The light sensitive parts of Night vision devices are very sensitive, so you have to keep this in mind all the time. If you do not understand this, look straight into a sharp light and see what happens! These parts operate in low light conditions and if exposed to too much light, they will be damaged (or the life time shortened drastically). For this reason it is better not to switch on the IR illuminator from the start; first try only with the light amplifier. The phosphoric screen can last for 1500 + hours, but should not exceed 2500 hours in any case, so use your instrument as intended to get the maximum use from it. From this you can gather that buying a second-hand one is not that good an idea, since you might end up with a good looking instrument with only a few hours of service still left!
More expensive night vision devices always deliver better images than cheaper ones and this is very evident in the area where the image is located. Cheaper instruments have more black spots scattered over the image area and more expensive ones less spots. However, more spots or less spots, you will enjoy your night sight device! Image distortion at the edges may also occur.