Comparison Dipol D209 vs Pulsar Challenger G2+ 1x21

— Binoculars. In its classic form, binoculars require a pair of optical systems, each with its own lens and eyepiece. Thanks to this, you can view objects with both eyes at once, which is quite convenient in itself (you don’t have to close your eyes), and the image looks three-dimensional. The main disadvantage of traditional binoculars compared to monoculars is their higher cost due to their more complex design. Also, such devices are larger, heavier, and if it is impossible to see normally with both eyes at once (for example, with strabismus, or if one eye is missing), all their advantages become irrelevant. At the same time, there is a specific variety - “pseudo-binoculars”: these are night vision devices with one lens, the image from which is sent to two eyepieces. In this case, there is no question of a three-dimensional image, which is why the use of such devices is more limited (in particular, they are considered poorly suitable for driving); but the designs are simpler, lighter and cheaper.

— Monocular. Optical instruments designed for one eye and equipped, respectively, with one optical system with an eyepiece and a lens. They are not as convenient as binoculars because they do not allow for a three-dimensional image and require one eye to be closed. On the other hand, monoculars are much more versatile. Thus, with a slight magnification of such a device, you can observe the situation wit...h both eyes at once, receiving an image from both the NVD and the naked eye; some monoculars can be mounted on weapons, turning a regular sight into a night sight; Another option is to install the device on a helmet and sight through it; and so on. However, the most important advantages over binoculars are compactness, low weight and low cost; In addition, monoculars are suitable even for people with binocular vision disorders.

— Sight. Devices designed for installation on weapons and equipped with appropriate mounts, as well as an aiming reticle of one type or another and a reinforced housing that can withstand recoil. They can be both NVGs and thermal imagers (see “Type”). In fact, such devices are an improved type of optical sights, designed for use in the dark, and in the case of thermal imagers, also in poor visibility conditions (fog, dense vegetation). And some models provide quite advanced functions that make accurate shooting much easier: rangefinder, barometer, compass, ballistic calculator, etc.

- Nozzle. Strictly speaking, this type of optical device is not a night vision device - the attachments themselves do not provide visibility in the dark. In fact, they are additional accessories, the installation of which allows you to expand the capabilities of a full-fledged night vision device. Most attachments play the role of magnetizers - i.e. increase the magnification factor. Such devices are created for specific NVD models, and even from the same manufacturer, not all attachments and devices are mutually compatible; Therefore, you should pay special attention to these points when purchasing.

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 diameter of the entrance lens that the lens of the night vision device is equipped with.

This parameter is one of the most important for any optical device, including night vision devices: the larger the lens, the more light (or infrared radiation) enters it and the more sensitive the optics are, all other things being equal. The downside of this is an increase in the size, weight and cost of the device. In addition, do not forget that various tricks and additional technologies can be used in the design; therefore, by itself, a large lens is far from always an unambiguous indicator of a high class.

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 visible image created by the night vision device. Indicated by the number of lines (strokes) per millimetre; the higher this indicator, the more detailed the image is capable of creating the night vision device, the better small details will be visible on it. However such devices will cost accordingly.

In models with an image intensifier tube (see "How it works"), the resolution is highly dependent on the generation of the transducer.

The size of the area visible in the night vision device from a distance of 100 m — in other words, the largest distance between two points at which they can be seen simultaneously from this distance. It is also called "linear field of view". Along with the angular field of view (see below), this parameter characterizes the space covered by the optics; at the same time, it more clearly describes the capabilities of a particular model than data on viewing angles.

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.

The smallest distance to the observed object, at which it will be clearly visible through the night vision device. For normal use of night vision devices, it is necessary that this distance does not exceed the minimum expected distance to the objects in question; thus, it must be borne in mind that the higher the magnification factor (see above), the greater the focus distance, usually.

The offset is the distance between the eyepiece lens and the exit pupil of an optical instrument (see "Exit Pupil Diameter"). Optimum image quality is achieved when the exit pupil is projected directly into the observer's eye; so from a practical point of view, offset is the distance from the eye to the eyepiece lens that provides the best visibility and does not darken the edges (vignetting). A large offset is especially important if the night vision device is supposed to be used simultaneously with glasses — after all, in such cases it is not possible to bring the eyepiece close to the eye. It is also relevant for devices that can be installed on a weapon: the greater the distance to the eye, the less likely it is to get injured due to recoil.