Starting a conversation about night vision devices, you need to eliminate one very common misconception first. In the pitch darkness, you can not even see the most expensive device. Because the principle of action of any night vision device is a multiple amplification of light that has fallen into the range open to the eye of the beholder.

The night vision device enhances the already available natural or artificial light. That is why in an absolutely dark room (that is called "without windows, without doors") with any night vision device you can not see anything. True, night vision devices are equipped with illuminators emitting infrared rays, but the role of these illuminators is only ancillary and of value in the event that some kind of "extraneous" light is still present.

An important characteristic of any night vision device, as, indeed, of all optical technology in general, is the multiplicity or increase. The higher the multiplicity, the stronger the device "increases" or "approximates" the observed object. We have already discussed this characteristic in detail in the text on daytime optical devices. The above can be extended to their multiplicity. The range of vision is a more specific characteristic. Professionals, as a rule, "lay out" it for "range of identification" and "detection range". The first term means the maximum distance from which a figure of a person can be examined in detail in a particular model of the night vision device in clear weather, at night, by the light of a quarter from the full moon. The second term refers to a slightly larger distance, from which, with the help of a night vision device, it is possible to determine the presence of a person or an object or animal of approximately the same size, but it is no longer possible to discern the figure in detail and to say whether the person is a beast or a large one lawn mower. The next significant characteristic of the night vision device is the light diameter. This is the diameter of the input lens, through which light enters the optical system of the device. It is difficult to overestimate the importance of this indicator. Through the input lens of a larger diameter, there passes, respectively, more light - the better and brighter the image observed in the night vision device. True, the larger the light diameter, the more bulky and bulky the whole device will be. The size of the light diameter for most night vision devices ranges from 24 to 50 mm.
The angle of view, measured in degrees, shows how vast the space can be seen in a night vision device. The higher this characteristic, the wider the "field of vision".
In the technical characteristics of some models of night vision devices, the value of the "linear field" of vision is sometimes indicated, i.e. diameter of a circle in which, from a certain distance (100, 1000 meters, etc.), objects can be observed with the aid of a night vision device. The light gain factor indicates how much light output at the eyepiece output exceeds the light fluxes entering the optical system of the night vision device from the observed object. To put it simply: the higher the light gain, the clearer and brighter the image of the object observed in the night vision device will be.
The light amplification coefficient is a complex indicator that depends both on the light loss in the optical system and on the amount of light amplification available to the electron-optical converters (EOS) of this model.
And, finally, we need to say about such a characteristic as resolution. The resolution resolution (measured in minutes) is smaller, the more convenient the model is for viewing small details of the object under review. If you try to give a simple and accurate definition of this characteristic, then the resolution is the number of distinct strokes per square millimeter of the image.

Having finished this, if necessary, a quick overview of the technical characteristics of the night vision device, let's present a schematic classification of these devices from the point of view of their purpose.
1. Night vision monoculars are designed for observation with one eye. Cheap and practical, night monoculars are in demand among fishermen, tourists, hunters, and also drivers of small ships.
2. Night vision binoculars are viewed with both eyes, which creates undeniable comfort, unavailable when using monocular. As a monocular, nighttime binoculars are useful to the tourist, examining the moon-flooded Alpine meadows, and the hunter, and the fisherman.
3. If, in the twilight or night haze, you want to not only look at something, but also carry out some actions, night vision goggles will help you.

"RONBO.RU" Moscow
2007