Detection range
The greatest distance at which a night vision device is capable of detecting individual objects.
The methods by which manufacturers determine this parameter may vary in detail, but the general principle is the same. Usually, the distance is indicated at which, with an illumination of 0.05 lux (a quarter of the moon) and a medium-contrast background, a rather large object can be seen — for example, a human figure with a height of about 170 cm is most often taken. of this object, but only to notice the very fact of its presence. Simply put, a detection range of, say, 200 m means that “something that looks like a person” can be seen in such a device at a distance of 200 m, but individual parts (head, hands) cannot be disassembled.
It is also worth noting that in fact this parameter is highly dependent on the characteristics of the situation. For example, a dark object on a very light background will be visible further, and on a dark one it may not be noticeable even up close; a similar phenomenon is observed for thermal imagers (see "Type"), only regarding the difference in temperature, and not in colours.
Wavelength
The wavelength of infrared radiation emitted by the IR illuminator installed in the night vision device. In most cases, this parameter is purely reference: manufacturers usually select the wavelength in such a way that it best suits the features of the device and provides the claimed characteristics. Nevertheless, a practical moment is also associated with the wavelength — the "visibility" or "invisibility" of the illuminator (see "Invisible radiation spectrum").
Invisible emitter spectrum
The presence in the design of night vision devices
of an IR emitter(see above), operating in a completely invisible spectrum.
One of the features of modern lighting devices (including infrared ones) is that none of them is capable of producing waves of exactly the same wavelength — some part of the radiation will inevitably capture neighboring ranges. Because of this, situations arise when the illuminator, the main power of which is concentrated in the IR spectrum, also emits visible light. It looks like a dim red glow; it is not strong enough to illuminate surrounding objects to the naked eye, but is clearly visible in the dark and can unmask the user. Radiators with an invisible spectrum, as the name implies, do not have this drawback. Therefore, if you are looking for night vision devices for situations in which stealth is important — for example, for hunting — it makes sense to choose among models with this function. However note that the illumination range of such emitters is somewhat less than that of visible ones.
Usually, "invisible" emitters have a wavelength (see above) of at least 800 nm.
