How does night vision and thermal works in fog?

Weather is something that humans have not yet learned to control. Sometimes, she presents very unpleasant surprises. One night, driving along the highway, we got into a terrible fog. He was sticking to the glass-like diluted milk, and, two yards away, you could not see anything. The fog lights didn't cope. The traffic was paralyzed, and we spent the night in the car. Then my friend said that an NV or TV device would allow us to move freely in the fog. This situation required clarification and formed the basis of this article. We will analyze how justified thermal imaging equipment and night vision equipment are in night fog conditions.

NV and TV technologies - how they work.

How does night vision technology work?
Many users confuse NV and TV technologies. Both technologies are used to monitor objects at night. What is the difference between them? Let's clarify this issue. The technology of night vision is based on the principle of detecting and amplifying the weak, reflected from the surfaces of objects, night light. That is, the device captures the reflected light and amplifies it many times over. We have to fix the fact that light needs to overcome the atmosphere, which consists of dust, gases, tiny water particles and gets to the light-sensitive lens. The greater the distance and the more polluted the air, the less light will hit the screen. Accordingly, the worse the image on the monitor will be.
Conversely, transparent, clean air will give an almost perfect picture. After the lens, the photons of light enter the photocathode. It converts light energy (photons of light) into electrical energy (electrons). To enhance the image, electrons are directed towards the microchannel plate. Passing through its channels and hitting the walls, they provoke the release of a large army of electrons. These streams of electrons rush to the phosphor screen, which converts electrons into streams of photons - visible light. We see him in night vision goggles in the form of a green volumetric image. The color may not be green, but gray-white or colored. The type of phosphor influences the color and the filters used. We see a picture of the area as we are used to seeing with our eyes, but only in slightly different lighting.

How does TV technology work?

Unlike NV, thermal imagers give a flat two-dimensional image. The thermal imaging equipment reads the temperature from all surfaces at which the screen is directed. Different surface temperatures form a picture on the monitor of the device. The higher the temperature, the more intense the color of the object. Optionally, you can apply paint or monochrome image schemes. A picture with precise details is formed thanks to a thermal sensor. The more nuances of temperature changes from a unit surface it can capture, the higher its resolution. And the higher the resolution, the more detailed the picture the user will receive. In addition, this affects the range of the device and the ability to increase the target. The general scheme of the device consists of a lens, a thermal sensor, a processor for information processing, and a screen. The lens captures the thermal signatures of objects, the thermal sensor measures, and the processor processes the information and feeds it to the screen. Now let's decide on how the fog will affect the display of data in both gadgets.

How do NV and TV works in fog?

How a night vision device works in fog.
We have focused on the moment when any radiation passes through the atmosphere. Its composition and volume decisively affect the quality of the resulting image. Any atmospheric air has the property of absorbing a certain proportion of radiation and, to some extent, scattering them. The denser the atmosphere, the higher the percentage of absorption and dispersion. Air density is influenced by: humidity, temperature, pressure, and the content of various impurities in dust and gas. An ideal atmosphere for radiation transmission is in clean mountainous areas with comfortable weather—everything changes in fog. The air is oversaturated with the smallest particles of water. Photons of light will collide with water molecules, partially be absorbed, and somewhat change direction - scatter. In this case, the night vision goggles receive too little information to process. The image will have fuzzy outlines with gray areas. In such conditions, it is unthinkable to use weapons because it is impossible to identify the target.

How thermal imaging devices work in a fog.

In foggy conditions, thermal imaging equipment does the job better. We remember that temperature affects its performance. If the fog is light, then the water particles are too small to affect the image drastically. But the mists are different. There are several types of them, from light to extremely dense. We add that the fog, polluted by emissions from cities, dust, is prone to forming more significant and numerous drops of water. It transmits a small amount of heat radiation. Fogs on the sea coast are incredibly dense. Thus, we will come to understand that with thick fog, burdened by pollution, in places below sea level, especially along the coast, the use of a thermal imager will have its limitations. They will affect the target detection range and the ability to identify it correctly. It is worth considering the sensitivity of the sensor, the resolution of the camera, its generation. The difference in temperature between the target and the general background and the size of the target plays an important role. But TV equipment will still provide enough information for movement or target detection, compared to visual inspection or the use of night vision devices.

When should you use NV or TV?

Night vision does a great job on light nights. When using IR illumination on nights. The third generation works in dense cloudy conditions. NV gives a detailed picture of the area. With night vision goggles, you can comfortably move around the room. When using night vision binoculars or a night vision scope, there will be no problem determining the distance to the target. A night vision monocular provides detailed information in a small forest or farm backyard. All this works great in good weather. When the weather gets bad and the ground is enveloped in fog, rain, or snowstorm, the best solution would be to use a thermal imager. Any type of thermal imaging equipment will be much more effective than NV or eyes. If the night is dark and impenetrable, and in addition, there is fog, then the use of thermal glasses will be more than justified. If you are an avid hunter and find yourself in a strip of moisture, it isn't easy to find an alternative to a thermal imaging sight or binoculars. Only a thermal monocular or a thermal imaging bracket for an optical sight can compete with them.

In conclusion, we can say that no matter how all-weather the use of thermal imaging equipment is, it cannot cover absolutely all tasks. And if it can, it will require a very immodest investment. To save your budget, it makes sense to pay attention to the joint operation of NV and TV devices in any combination convenient for you. Thermal imaging optics have proven their worth when working in difficult weather conditions and will help identify a hidden target. And night vision will ideally determine the distance to the target. It will give comfortable movement and orientation.