Comparison FLIR Scout II 640 vs FLIR Scout PS32

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.

The maximum magnification that a night vision device can achieve through digital image processing.

This function is available only in thermal imagers and some digital models of classic night vision devices (see "How it works"). In general terms, it can be described as follows: the device electronics takes part of the image from the NVD receiver and “stretches” it to the entire frame visible to the user, due to which objects in the field of view look larger. At the same time, this procedure reduces the clarity of the visible image. Therefore, models with digital zoom are quite rare, and even in such cases it plays an auxiliary role and has a very limited magnification — usually less than 2x.

The focal length of a night vision device. This term means such a distance from the optical centre of the lens to the photocathode of the image intensifier tube or the matrix of a digital device(see "Operation principle"), at which a clear image is obtained on the photocathode/matrix.

In general, long focal lengths are characteristic of optical systems with a high degree of optical magnification (see above). However, in the case of night vision devices, this dependence is not rigid — it is simply easier to ensure a high magnification with long-focus optics. In fact, this means that models with the same focal length can differ markedly in magnification. But what this indicator directly affects is light transmission: other things being equal, longer optical systems transmit less light, which negatively affects the capabilities of the device. This is also true for thermal imagers (see "Type"), because their working infrared range in this case also obeys the general laws of optics.

The resolution of the matrix installed in the thermal imager (see "Type") or digital night vision device (see "Operating principle"). Usually specified in pixels horizontally and vertically, for example 640x480.

On the one hand, the higher the resolution, the clearer and more detailed the image will be. On the other hand, increasing the resolution without changing the matrix size means that less light will fall on each pixel, which negatively affects the detection range (see above) and leads to the appearance of noise. Therefore, the resolution of receivers in modern NVDs is small - in terms of conventional megapixels, it rarely exceeds 0.3 MP. And it hardly makes sense to compare different models by this parameter, because the actual quality of work also largely depends on the size of the receiver, the features of signal processing, etc.

The angle of view provided by a night vision device — that is, the angle between the lines connecting the observer's eye with the two extreme points of visible space. Wide viewing angles allow you to cover a large area, but the magnification factor (see above) is low; in turn, increasing the magnification leads to a decrease in the field of view.

— Video output. The presence in the NVD design of an output that allows you to broadcast an image from the device to an external device — for example, a laptop. Thus, you can view the "picture" on a large display and record video even if the night vision device does not have its own video recorder (see below); and if it is available, you can broadcast not only the image in real time, but also the captured materials. The specific video output interface may vary, but most often the signal is transmitted in analogue format.

— Built-in video recorder. The presence of its own video recorder in the design of night vision devices. This allows you to use the device as a video camera, capturing everything that falls into the field of view on video; at the same time, such recording does not require additional equipment, in contrast to working with the video output described above. Video, usually, is stored on a memory card, and in many models it is possible to view the recording directly on the device itself.

— Switching observation modes. The ability to switch observation modes means changing the colour features in the “picture” visible to the user. So, thermal imagers (see "Type") with this function support at least two classic modes "white hot" (the warmer the object, the brighter it is) and "black hot" (the warmer, the darker); in addition, additional format...s can be provided, such as highlighting especially warm objects in red. In classic night vision devices, switching modes usually involves changing the colour tone of the visible image — for example, from classic green to red or black and white. And additional features may include, for example, a high contrast mode.

— Filling with gas. This feature implies the presence in the body of a filler in the form of an inert gas — for example, nitrogen — containing a minimum of water vapor. Such an environment does not oxidize the parts in contact with it, and the “dryness” of the filler also prevents fogging of the optics from the inside during temperature changes. Note that a kind of “side effect” of filling with gas is dust and water protection (see below), since the cases of such devices, by definition, must be airtight.

— Dust-, water protection. The presence in the design of night vision protection against dust and moisture, which prevents the ingress of contaminants on sensitive components. This feature is almost mandatory if you plan to actively use the device in the open air — for example, hunting. Note that the level of security can be different, and a high degree of protection usually means a high price. Therefore, when choosing, it makes sense to clarify the parameters claimed for each specific model and correlate them with your real needs.

— Impact protection. This function involves the use of various means — strong elastic body materials, shock absorption systems, etc. — which prevent damage to the sensitive components of the device during shock and shock. The degree and features of shock protection can vary markedly: usually, such models can withstand drops of at least 1.5 m, but in some cases this figure may be more. Note that for installation on firearms, special protection against recoil is required, which not all shock-resistant devices have.

— Angled eyecups. The presence of beveled eyecups (or one eyecup, in the case of monoculars — see "Type") in the design of night vision devices. The elongated part of the eyecup when working with the device is located on the outside of the eye, almost on the temple; due to this, it provides additional protection for the eye — primarily from extraneous "flare" that interferes with normal viewing of the image in the eyepiece. At the same time, such models do not go well with glasses: at best, the eyecup will have to be turned up, negating all its advantages, and in some devices this is not even possible.

The type of batteries used by the night vision device for operation. Technically, these can be both replaceable elements of a standard size and built-in batteries. However, in fact, the second option is practically not found, because. it does not make it possible to quickly replace a dead battery with a fresh one — and this possibility is critical for most NVD applications.

As for specific types of batteries, the most common options are:

— CR123. The element that has received the greatest distribution among modern night vision devices. These batteries are similar in shape to the popular AA batteries (see below), but their diameter is larger, and their length is noticeably smaller: 17 and 35 mm, respectively. The operating voltage is 3.7 V, which provides good power, sufficient for normal NVD operation. This led to the popularity of CR123.

— AA. Classic 1.5 V finger batteries. The power of such a power supply is lower than that of CR123, which requires more cells; on the other hand, such batteries are easier to find commercially.

— AAA. "Mini finger" or "little finger" batteries, a smaller version of AA cells. Due to their small size, such elements do not differ in power and capacity, and therefore are used only in relatively simple devices for which compact dimensions are important.