Infrared goggles. Night vision devices and thermal imagers, or how to find a black cat in a dark room

In this article I will show you how to make simple night vision goggles. Of course, they will not be super powerful as real ones, but getting to the right place in the room in the dark will not be so difficult. All the necessary details can be found in your home, you can order them from the Chinese, or you can just read this article for general development.

There is an action camera in the design of the glasses, in fact this is one of the main parts, so in the daytime they can be used as a first-person camera and shoot interesting videos.

You will also need an infrared flashlight with a light wave of 850 nm, since this is the light that the camera perceives best, but you can try replacing it with infrared LEDs with similar characteristics, if these suddenly turn out to be available. It is convenient to use a flashlight because you do not need to make a separate box for power supply and it is much easier to mount it.

If you turn on the flashlight and look at the diode through the camera, you can observe a lilac glow, this is infrared light. It is not visible to the human eye, but through the camera please!

But not all cameras of a lonely person perceive such radiation well, so the author used the action camera, as it coped with the task better than others, moreover, such a camera has many settings that will help improve the perception of radiation.

We also need lenses for virtual reality glasses, which were bought by the author on Aliexpress, they are needed to focus the eye on the camera screen, since the human eye is not able to focus on objects that are directly in front of it at a minimum distance.

To fix the lens, you need to assemble the frame. Auto used a dark plastic drink bottle for this purpose.

The lens exactly fits the diameter of the neck, it remains only to fix it there.

To do this, you don’t need to glue anything, you just need to cut out with a blade or knife the middle part of the cork from the same bottle.

Then we put the lens in it and twist it onto the bottle. It seems that the lens was specially made according to the diameter of the neck, since the cork twists easily and fixes it.

Now you need to cut off the top of the bottle, while choosing a comfortable length at which the focus will be set correctly.

Next, you need to come up with a holder for the camera, to which the assembled optics will subsequently be attached. The author used foamed PVC plastic, which is used when assembling layouts. It needs to be cut into pieces according to the size of the chamber to make boxes and glue them together with super glue.

Then you need to fix the optics from the bottle segment to this viewing window. To do this, mark the edges of the window with molar tape and cut off everything superfluous without touching the tape. You will get two protrusions that should be easily inserted into the edges of the window, after which we glue everything with super glue to fix it.

After assembly, the camera fits very tightly into the resulting box and there is a chance that the camera cannot be pulled back, so the author decided to make cuts for the fingers and the record button. After a little refinement, the camera can be removed from the box without any problems.

To protect glasses from chips, we glue the glasses with molar tape. We take a crown and drill a hole in the center evenly from both sides. The author recommends not drilling to the end, leaving thin plastic, then finishing the hole with a clerical knife, this will help to avoid possible chips and cracks during drilling.

After the hole is made, the optic should be freely inserted there, but as you can see in the photo, the camera is directed to the side and needs to be aligned.

Then, using sandpaper, I cleaned all the edges and using super glue glued everything in its place.

To fix the lantern, plumbing clips of the required diameter were used, which are selected based on the dimensions of the lantern.

The clips are attached to the side of the goggles with bolts and nuts. After that, the lantern is easily fixed and securely held in place. The infrared flashlight can be replaced with a regular one and, as mentioned above, you can shoot good videos from the first person.

For a more secure fixation, the author recommends securing the 32nd tube with nylon ties, since the camera is heavy and the super glue mount may not withstand it. To do this, using a drill and a screwdriver, we make three holes in the pipe and three in the glasses opposite each other, run the ties in them and tighten them, now it’s definitely reliable!

Even 60 years ago, only birds and animals could see in the dark. But the rapid development of science and technology has opened this possibility to man. Thanks to numerous experiments, German developers have managed to create night vision goggles (NVG), which are now indispensable in many areas of human life.

What are ONV

This is a special device that allows you to distinguish objects in the absence of light. The device has double eyepieces and is mounted on the head or helmet with the help of special straps. This convenient design makes it possible to use glasses while driving.

NVGs have a built-in infrared brightener and, depending on the model, can provide visibility from 100 to 600 meters.

Features of ONV

1. Wide range of models. Today, night vision goggles are produced by many foreign and Russian manufacturers. They make different models that differ in functionality and cost. Thanks to a large selection, both amateur and professional have the opportunity to easily find the right glasses.
2. No magnification. NVGs do not increase items.
3. Wide field of view. Due to the lack of magnification, the glasses have the largest field of view among all night vision devices.
4. Ease of use. All ONV can be worn in two versions: in working and folding. In the first case, the glasses are at eye level. And when there is no need to use the device, you can simply fold it up. This allows you to do work that is not related to glasses.
5. Possibility to use additional nozzles. If necessary, nozzles can be attached to the glasses to increase the magnification or an infrared illuminator, which allows you to increase the range of the device.

Advantages

The usual model of ONV costs about 10 thousand rubles. Therefore, many buyers are wondering about the appropriateness of the purchase. According to experts, night vision goggles are the best device for long-term night observations. The fact is that the monocular and binoculars have good characteristics, but with a long look from such devices, the hands quickly get tired. Well, if it is possible to mount the devices on a tripod or other support, you will only have to conduct static observation. At the same time, when using the NVG, hands are completely freed and it is possible to move around the area in any direction. And when they are not needed, it is enough to bring the glasses to the non-working position without removing them from the head.

Types of NVG: which one to choose?

To date, there are two types of ONV: binocular and pseudobinocular. The first type of glasses consists of two identical channels for the left and right eyes. Each channel has a lens, image intensifier tube and eyepiece. In such NVGs, the image is processed separately by each channel. Most models have a special regulator that allows you to adjust the distance between the pupils. Therefore, each operator can customize the binocular night vision goggles. A photo of this type of device is presented below.

Binocular NVGs allow you to quickly determine the distance of objects to the lens, but they are heavy and expensive. Their use is justified only in the case of performing tasks that require a quick assessment of the distance and speed of movement. Therefore, binocular glasses are most often used by special forces and helicopter pilots for night operations.

In pseudobinocular glasses, the image that enters the lens of the optical channel is enhanced, followed by its division into two eyepieces. Glasses of this type are ideal for night fishing and hunting.

Operating principle

Infrared night vision goggles allow you to see in complete darkness thanks to the use of a special backlight. It contributes to the amplification of light, which is usually not perceived by the human eye.

The light reflected from the objects falls on the lens, in which the image is focused on the surface of the electron-optical converter. The task of this element is to amplify the flow of light entering through the lens and transmit the image to the screen. On it, the observer examines objects through the eyepiece.

This mode of operation is called passive, because the glasses only amplify the light output. Well, if there is no light at all, the electron-optical converter cannot make it visible. To solve this problem, infrared brighteners are available in most modern NVG models. This element serves as a light source and is used in cases where natural light is not enough for night vision goggles to work.

Applications

Night vision goggles are designed to observe objects and navigate the terrain at night. This device is used for the protection and patrolling of territories, the performance of military special operations, the control of aircraft and ships, emergency and rescue operations, and even travel in extreme conditions. Many use NVG for hunting and fishing at night.

Night vision goggles for hunting

Goggles for night hunting are an indispensable device in the field. It not only makes it possible to quietly get close to the game, but also performs the functions of protecting the eyes from possible injuries.

Hunting glasses are also divided into several types. The most popular are monoculars. They are securely attached to the hunter's head, thereby freeing his hands for careful aiming. The only drawback of such glasses is the limited vision of the panorama.

Expensive models of goggles for hunting allow you to adjust the optical scale and magnify the image.

How to make ONV yourself?

Night vision goggles have long been part of the life of an ordinary person. Professional devices are usually expensive, so more and more people are trying to make such a device on their own.

To make your own night vision goggles, you will need two unnecessary mobile phones, old glasses, a flashlight and a children's metal constructor.

So, you need to take two identical working mobile phones with cameras. Remove the lenses from the glasses and install two identical magnifiers in their place.

From a metal children's designer, make two brackets that should fasten phones to glasses. In the locked position, the brackets should point forward. The mounting method depends on the design of the phones. In each case, the type of fixation must be selected individually.

Then you need to fix the phones on the glasses at a distance at which the image on the screens is clearly visible. It's great if phones allow you to turn on cameras without SIM cards. Well, if this is not possible, you need to insert cards into each phone.

After that, you should convert the usual LED flashlight to infrared. To do this, you need to solder the white diodes, and in their place, observing the polarity, solder the infrared ones. Now you can start testing homemade NVGs.

You can check the performance of the device in a normal room. At night, you need to turn off the lights, put on glasses with the cameras turned on. Illuminate the room with an infrared lamp. It is important that the backlight automatically turns off in phones and its minimum brightness is set.

All objects that fall under the sight of the lantern must be visible on the screens. But only their image will be white, and not green, as on factory-made devices.

If you can’t do the NVG yourself, but at the same time there is a need for them, the only option left is to buy a ready-made device.

Glasses "Dipole"

Dipol night vision goggles have been produced for over 20 years. Thanks to the latest technologies and extensive experience, the manufacturer manages to create high-quality devices at an optimal cost.

The main advantage of Dipol glasses is the ability to easily change lenses with different types of magnification without additional settings. All NVG models use eyepieces with a large pupil diameter. This greatly simplifies the use of the device, since there is no need to adjust the interocular distance.

The glasses are conveniently fixed on the head and do not cause discomfort even when worn for a long time. They are lightweight and comfortable to use. The simple design allows you to quickly adjust the position of the glasses and flip them to a vertical position.

Other advantages of the Dipol ONV are the reliability and durability of the device. The device has excellent mechanical, optical and ergonomic characteristics. To create glasses, the manufacturer uses a high-quality alloy of impact-resistant plastic and aircraft-grade aluminum.

ONV "Viz Max"

High-quality products with excellent optical characteristics are produced by the well-known American company Astronics Corp. It manufactures Vis Max night vision goggles for aircraft pilots. Thanks to the unique technology, the devices allow you to clearly see the space even through fog and smoke. The goggles help pilots accurately see trees, lines, obstacles and landmarks that are important to flight. Also, during the use of the ONV "Viz Max", spatial orientation improves and fatigue decreases.

The use of "Vis Max" glasses allows you to minimize or even completely eliminate the likelihood of meteorological interference during the flight.

Since 1992, the Optics Trade company has been actively operating in Moscow, specializing in the sale of various optical and mechanical products for professional activities and hobbies. Among the wide assortment variety you can find binoculars, sights, night vision devices, including special goggles for hunting.

Which glasses are better to choose

Modern devices for observation at night and in poor lighting due to weather conditions are now being produced as convenient and adapted for operation as possible. Night vision goggles, which you can buy in Moscow from the OpticsTrade online store, allow you to fish with special comfort - the hunter's hands are freed, the functionality of the device is increased. This device can be used indefinitely. If the need arises, the hunters move it up and are distracted from observations by any other activity.

Night vision goggles for hunting, the price of which can be different due to professional components, are expensive and more budgetary. Such a design of a night vision device is distinguished by the fact that they do not have a magnification factor. In case of poor visibility, this characteristic is considered an advantage, as it allows the hunter to more adequately assess the situation at the current moment. More productive observation allows you to maintain a wide field of view along with excellent quality optics.

Having decided to purchase night vision goggles in Moscow, hunters often additionally use infrared (IR) illumination or flashlights, which can be quickly and easily attached to the body without much effort and skills. Such a purchase will increase the observation range and detail the object. In addition, it is possible to retrofit the device with a nozzle, which increases the magnification of the existing optics. Now you can buy in Moscow any model from different world manufacturers, including exclusive models.

Benefits of the service and a large selection

The sale of night vision goggles for hunting in our company has a number of advantages:

• a large selection of models of different configurations and complexity of execution;
• the price of night vision goggles can be high or budget - it all depends on the choice of model and brand;
• the company changes the product if something in it does not suit the client, or returns 100% of the cost;
• service maintenance is carried out throughout the entire operational period - the company maintains contacts with all manufacturers;
• offer of post-warranty repair for devices not purchased in our store;
• Acceptance of payment only after confirmation by managers of the availability of the ordered model in stock.

If you decide to purchase the device at a retail outlet, it is possible for specialists to help install the bracket on the weapon. works from 9:00 to 21:00 without breaks in 7/7 mode. Experienced managers are always ready to provide advice and select a model for a specific purpose of use. Depending on the price of the goods and the chosen delivery method, payment methods may be different - cash on delivery, partial or full prepayment.

It is possible to pick up goods from different stores of the company, courier delivery in Moscow and the region within 4-24 hours (provided that the order amount is at least 12,000 rubles). It is also possible to send mail or delivery by courier postal service EMC "Post of Russia" or SDEK.

We present to your attention the section with night vision goggles. These modern devices, which give a person the ability to see in complete darkness, have one great advantage over similar devices. This is a convenient attachment to the head with a special mask helmet. Users do not need to constantly hold a high-tech device in their hands, in addition, in this position it can be perfectly adjusted once to their vision parameters. The scope of the glasses is not limited to night hunting, they can be successfully used by tourists, rescuers, sailors, security workers, lovers of observing the life of animals, whose activity is manifested in the dark, etc.

Night vision goggles for hunting

If you consider yourself an avid hunter, we advise you to buy night vision goggles from our range. Here you can choose a model that is ideal for any of your requirements. Image intensifier tube brand, photosensitivity, presence or absence of IR illumination, durability and reliability of work in almost any conditions. If you choose night vision goggles, the price of which is in the middle price range, we advise you to pay attention to the products of the Pulsar or NPF Dipol brands. These devices will be able to serve you for more than one year. The operating period of devices of this class goes far beyond the warranty period. The ability to see in complete darkness or at a very low level of illumination gives the hunter undeniable advantages that he can take advantage of during the night hunting for a cautious animal.

price of night vision goggles

If you are looking for modern night vision goggles, we advise you to pay attention to the assortment of the corresponding section. A wide selection and loyal pricing policy will allow you to choose a modern device that will fully satisfy your requirements. A small cost of night vision goggles for hunting will allow you to go in for your favorite hobby next weekend.

Vision is the most important way of perceiving the surrounding reality. Visually, we get most of the information about the outside world. Our eyes are an amazingly complex and perfect mechanism, gifted to us by nature. But, unfortunately, their possibilities are somewhat limited.

A person is able to perceive only a very narrow optical range of the entire spectrum of electromagnetic radiation (it is also called the visible part of the spectrum), in addition, the eye can perceive a “picture” only in conditions of sufficient illumination. For example, if it falls below the level of 0.01 lux, then we lose the ability to distinguish the colors of objects and can only see large objects that are nearby.

This is doubly insulting, because because of this feature of our vision, we become almost blind in the dark. Man has always envied other representatives of the animal kingdom, for whom the darkness of the night is not an obstacle: cats, owls, wolves, bats.

The military especially did not like this limited human vision. But the situation was radically changed only in the middle of the last century, when, thanks to the achievements of physics, night vision devices appeared, allowing you to see at night almost as clearly as during the day.

Currently, night vision devices are not only in the army arsenals, they are used with pleasure by rescuers, hunters, security units, and special services. And if we talk about thermal imagers, then the list of their use is even wider.

Today, there is a huge number of a wide variety of types and types of night vision devices (NVD) in the free market, made in the form of binoculars, monocles (monoculars), sights or ordinary glasses. However, before talking about the design of a night vision device, a few words should be said about the physical principles on which the operation of such devices is based.

How does he work

The operation of night vision devices and thermal imagers is based on the physical phenomena of the internal and external photoelectric effect.

The essence of the phenomenon of the external photoelectric effect (or photoelectron emission) lies in the fact that solid bodies emit electrons under the influence of light, which are captured by night vision devices. The basis of any night vision device is an image intensifier tube - an electron-optical converter that captures weak reflected light, amplifies it and turns it into an electronic signal. That is what a person sees in the NVD lens. It should be understood that no night vision device is capable of "seeing" in absolute darkness. True, there are also active night vision devices that use their own source of infrared radiation to illuminate objects.

Any night vision device consists of three main components: optical, electronic and one more optical. Light is received by a lens, which then focuses it onto an image intensifier tube, where the photons are converted into an electronic signal. The maximum amplified signal is transmitted to a fluorescent screen, where it again turns into an image familiar to the human eye. The above design is generally typical for any generation of night vision devices, it's just that modern night vision devices (second and third generations) have a more advanced signal amplification system.

Thermal imagers, on the other hand, capture their own radiation from any body or object whose temperature is different from absolute zero. The main part of thermal imagers are the so-called bolometers - complex photodetectors that capture infrared waves. Such sensors are sensitive to wavelengths corresponding to the temperature range from -50 to +500 degrees Celsius.

In fact, thermal imagers have a fairly simple design. Each such device consists of a lens, a thermal imaging matrix and a signal processing unit, as well as a screen on which the finished image is displayed. There are two types of thermal imagers: with a cooled and uncooled matrix. The former are the most sensitive, expensive and massive. Their matrix is ​​cooled to a temperature of -210 to -170o C, usually liquid nitrogen is used for this. More often they are used on large military equipment (for example, any tank night vision device).

Thermal imagers with an uncooled matrix are much cheaper, they are smaller in size, but their sensitivity is much lower. However, most of the thermal imagers that are on the market today (up to 97%) belong to this category.

One of the main features of thermal imagers, which largely determines their high cost, is their lenses. The fact is that ordinary glass, used in most optical instruments, is absolutely opaque to infrared radiation. Therefore, rare materials such as germanium, which has a market price of about $2,000 per kg, are used for thermal imaging lenses. The average germanium lens for a thermal imager costs about $7,000, while a good one can cost up to $20,000. Today, both in Russia and abroad, they are actively looking for a replacement for germanium, which, in theory, can reduce the cost of a thermal imager by 40-50%.

History and classification of night vision devices

The classification of night vision devices is based on the sensitivity of the photocathode, the degree of light amplification, and the resolution at the center of the resulting image. As a rule, there are three generations of NVD. In addition, early NVGs with an additional source of infrared radiation are often referred to as a separate generation. On the websites of manufacturers, you can find information about night vision devices of the so-called intermediate generations, like 1+ or 2+. However, such a gradation is more for marketing purposes than it is a reflection of real differences.

Improvement in the design of night vision devices and the emergence of new generations of these devices proceeded sequentially, one after another. Therefore, it is more convenient to consider the classification of night vision devices together with the history of their development.

On August 23, 1914, near the Belgian city of Ostend, the Germans managed, with the help of heat direction finders, to detect a British squadron consisting of armored cruisers and destroyers. And not just to detect, but also to correct artillery fire with the help of these devices, preventing enemy ships from approaching an important port. It is believed that it was from this moment that the history of night vision devices began.

In 1934, there was a real breakthrough in this area: the Dutchman Holst created the world's first electron-optical converter (EOC). Two years later, Russian emigrant Zworykin developed an image intensifier tube with electrostatic signal focusing, which later became the "heart" of the first commercial night vision device of the American company Radio Corporation of America.

The period of rapid development of NVD was World War II. Nazi Germany became the leader in their development and application. The first prototype of a night vision sight was created by the German company Allgemeine Electricitats-Gesellschaft (AEG) in 1936, it was intended for installation on Pak 35/36 L/45 anti-tank guns.

By 1944, German Pak 40 anti-tank guns could fire using night vision devices at distances up to 700 meters. Around the same time, the Wehrmacht tank troops received the Sperber FG 1250 night vision device, with the use of which the last major German offensive on the Eastern Front near the Hungarian Lake Balaton took place.

All of the above night vision devices belong to the so-called zero generation. Such devices were characterized by very low sensitivity, so an additional source of infrared light was needed for their normal operation. For example, every five German tanks equipped with the Sperber FG 1250 were accompanied by an armored personnel carrier with a powerful Uhu ("Owl") infrared radar. In addition, zero-generation night vision devices had image intensifier tubes that were sensitive to bright flashes of light. That is why, at the end of the war, Soviet troops often used conventional searchlights in the offensive. They simply blinded the German night vision devices.

The Germans also had attempts to create night vision devices that would provide a greater range of vision (up to 4 km), but due to the significant size of the IR illuminator, they were abandoned. In 1944, an experimental batch (300 pieces) of Vampir night vision devices was sent to the troops, intended for installation on German Sturmgever assault rifles. In addition to the sight itself, it included an IR illuminator and a rechargeable battery. The total weight of the device exceeded 30 kg, the range was 100 meters, and its operation time was only 20 minutes. Despite these rather modest figures, the Germans actively used the "Vampire" in the night battles of the final stage of the war.

Attempts to create a zero-generation NVD were also in the Soviet Union. Even before the war, the Dudka complex was developed for tanks of the BT family, and later a similar system appeared for the T-34. You can also recall the domestic night vision device Ts-3, which was developed for PPSh-41 submachine guns. It was planned to equip assault units with similar weapons. However, night vision devices were not widely used in the Red Army. At that time, night vision devices were still exotic, and the Soviet Union during the Great Patriotic War was definitely not up to it.

The experience of the Second World War showed that night vision devices have excellent prospects. It became clear that this technology could seriously change the way we fight not only on land, but also in the air and at sea. However, for this, zero-generation night vision devices had to get rid of a large number of their inherent shortcomings, the main of which was their low sensitivity. It not only limited the range of night vision devices, but also forced the use of a bulky and very energy-intensive IR searchlight with the device. And in general, the design of the first night vision devices was too complicated and did not differ in sufficient reliability.

Soon the primitive night vision devices of the war period were replaced by first-generation devices based on image intensifier tubes with electrostatic focusing. They were able to amplify the input signal several thousand times. This, in turn, made it possible to refuse additional illumination. IR searchlights not only made the system unnecessarily heavy, but also unmasked the fighter on the battlefield. The first generation night vision devices reached their peak of perfection by the 60s of the last century, the Americans actively used them during the Vietnam War.

The second generation of night vision devices appeared due to the emergence of revolutionary microchannel technology, this happened in the 70s. Its essence was that now the optical plates were dotted with hollow tubes-channels with a diameter of 10 microns and a length of not more than 1 mm. Their number determined the resolution of the light guide plate. A photon of light, falling into each of these channels, causes a whole cascade of electrons to be knocked out, which significantly increased the sensitivity of the device. For second-generation night vision devices, the amplification can reach 40 thousand times. Their sensitivity is 240-400 mA/lm, and the resolution is 32-56 lines/mm.

In the Soviet Union, based on this technology, Quaker night vision goggles were created, and in the USA - AN / PVS-5B.

Later, night vision devices appeared, in which there is no electrostatic lens at all and there is a direct transfer of electrons to a plate with microchannels. Such NVDs are usually referred to as generation 2+. On the basis of a similar scheme, domestic night vision goggles "Eyecup" or their American counterpart AN / PVS-7 were made.

Further efforts of scientists to improve night vision devices were aimed at improving the photocathode. Philips engineers proposed to make it from a new semiconductor material - gallium arsenide.

This is how third-generation night vision devices appeared. Compared to traditional multi-alkali photocathodes, their sensitivity has become 30% higher, which made it possible to observe even on a cloudy moonless night. The only problem was that the new material could only be made under high vacuum conditions, and this process turned out to be very laborious. Therefore, the cost of such a photocathode turned out to be an order of magnitude higher than that of its predecessors. at the same time, third-generation night vision devices can amplify incoming light by 100,000 times. It can also be added that only two countries, the USA and Russia, can produce gallium arsenide on an industrial scale.

If you see information about the sale of fourth-generation night vision devices somewhere, then keep in mind: most likely, you are being deceived. It does not yet exist, it is not even clear what criteria to use to define this group. Although, of course, research to improve existing "night lights" is being conducted in dozens of countries around the world. For thermal imagers, they are looking for a budget replacement for germanium glass, the main problem of night vision devices is the search for a cheaper analogue of gallium arsenide photocathodes. At the beginning of the 2000s, the Americans announced the creation of a new generation of night vision devices, but some experts believe that it can rather be called the 3+ generation.

Applications and prospects

Devices that allow a person to see at night are becoming more popular every year and find new areas of application. Modern "civilian" night vision devices are quite affordable, so hunters, security agencies, and other categories of citizens who need night vision can afford them.

The most interesting thing is that all three generations of night vision devices are present on the market today. Many night vision devices for hunting are first generation or even zero and have IR illumination, which is absolutely unacceptable for military night vision devices. Third-generation devices are also used on the “citizen” (you can see them even in basements). The technologies that are used in their creation have not been secret for a long time, it’s just that the devices are very expensive. NVG sights can also be made using elements of different generations.

The use of thermal imagers has also long ceased to be the exclusive prerogative of the military. In addition to hunting and observing at night, such devices are increasingly used in scientific research. With their help, for example, they check spacecraft before launch: the thermal imager perfectly shows various leaks that can lead to disaster. The thermal imager is also indispensable in the energy sector. This device can easily show where heat is leaving the building most actively, and will also allow you to detect places of maximum loads in energy networks. Thermal imagers are also used in medicine: according to the temperature map of the human body, some diagnoses can even be made. Every year, such devices are becoming cheaper, so the scope of their application is steadily expanding.

If you have any questions - leave them in the comments below the article. We or our visitors will be happy to answer them.