Night vision devices give the user the ability to move and see objects in the dark. With goggles or binoculars, you can go on a night hunt, observe the life of nocturnal animals or protect your house from intruders. But there happen situations when goggles, monoculars, and other NV devices are useless. First of all, such devices cannot provide a clear image when there is a lack of light. Also, their lens can be damaged by flare. Therefore, it is worth knowing more about the disadvantages of such accessories to know how to use them correctly.
What is a night vision device?
NV device helps the human to see objects hidden in the dark. For the first time, this technology was used during the Second World War by the military forces of Germany and America. But the construction of those devices was quite bulky, they required additional infrared illumination, and the batteries quickly heated up.
The technology attracted the real interest of military and civil customers in 1960 when the image intensifier tube was invented. With each year, this technology was improving and becoming more affordable to a wide range of buyers.
How does night vision technology works?
Such equipment does not enlarge the image or enhance its clarity but captures the light that all objects reflect. Any object around us reflects a certain amount of light. The human eye can catch only a small part of this light, so people see very poorly in the dark. Night vision devices capture the maximum amount of reflected light, convert it into an image and pass it to the user’s display.
The design of night vision device
Such a device has a complex construction, which night vision manufacturer improves with each new generation. Today there are three generations of night vision devices, and the latest one can transmit a clear image with a minimum amount of light or even in total darkness.
NV device principle of work:
• Outer lenses catch all available light reflected from objects around and create a light beam
• The beam is directed to the photocathode. This element works from a power source – batteries. When passing through the photocathode, photons of light turns into electrons of energy.
• Electrons enter the image intensifier tube chamber. Into the chamber is a microchannel plate made from fiberglass. On its surface, there are hundreds of symmetrical microholes. When electrons pass through microholes, their number is increasing thousands of times.
• A huge stream of electrons is then directed to the phosphor screen. When electrons hit the screen, they create tiny flashes of energy. This way electrons transferring part of the image of the object from which the light was reflected.
• The phosphor screen “gather” particles of energy, convert them into an image visible to our eye, and pass it to the user's screen.
The first generation of night vision devices required good illumination. They could work only using long-range ir beam. They also could be spoiled. If light from flashlights or lamps was entered, their lenses. Gen 3 devices are not sensitive to artificial light, have a good range and clarity of view. Therefore, if necessary, night vision goggles can be used to move or even drive a car at low speed in darkness.
The size of modern night vision devices is tiny, as is the weight. The core element – an image intensifier tube – easily fits into miniature models of goggles and monoculars. Due to this, such accessories are convenient to carry in the pocket, attach to a head-mount or helmet.
Why is night vision green?
The image in the first models of NV accessories was black and white. But this color scheme had quickly tired the eyes, so it was quite hard to use a device for a long time. Gradually, night vision manufacturers
began to put inside the tube a special green filter. Why exactly green? Quite simply, green is the most comfortable to our eyes because it is at the center of the color spectrum that our eye sees. It does not tire the eyes but rather helps them to relax. Therefore, you can use your goggles or NV sight as long as you need.
In the last 10 years, scientists have developed a new technology – colored night vision. It allows NV devices to transmit a multicolor image. The clarity and color-true of the image depending on the image intensifier tube. The more sensitive it is to the photons of light, the better the image will be produced.
A color image is obtained using a special filter that needs to be attached to your NV equipment. This technology is called ColorTAC and is widely used by military and secure companies.
When won't the night vision device help you?
Yes, many people rightfully consider such accessories to be a genius invention of humanity, but they are not perfect. There are situations when your NV device cannot provide you with a good image:
• If you have an inexpensive device, it may show a dark or blurry picture in low-light conditions. For example, if there are few stars in the sky, no moon, or cloudy. Some devices need a short-range IR illumination, but this beam is well seen by other people who also have an NV device. Therefore, for military or secure purposes, Gen 2 or Gen 3 devices are using.
• Lenses of inexpensive models are susceptible to artificial light sources. They can be spoiled if light from streetlights or light from your own flashlight gets into the objective. Such devices are not recommended for use if there are buildings, highways, or other objects with artificial lighting nearby.
• In poor visibility conditions. Night vision devices only capture the light reflected from objects. If there is smoke, fog, raindrops, or snowflakes in the air, the light rays will not freely reach the lenses. And this is perhaps the biggest disadvantage of such devices. That is, you will not be able to use NV goggles or binoculars if it is foggy in the forest or field at night, it is raining or snowing outside, or there are sources of smoke nearby.
But, despite all the listed disadvantages, such devices are top-rated among hunters, fans of extreme recreations, and the military. Gen 1 equipment can still be bought on the market, which costs $300-400.
What to do if your night vision device becomes useless?
Any invention quickly gets an alternative. In our case, these are thermal vision devices. Yes, they are several times more expensive than NV, but thermal imagers do not need light to produce the image because they react to heat. Every object, alive or not, has its own temperature. A thermal imager gathers it and turns it into a colored image.
Thermal sensors collect temperature data of objects around and then pass this information to a computer. The software processes this data and turns it into a visible to the user image. Gotten image is not detailed like in NV but divided into temperature zones. The warmer the zone, the brighter and warmer the color.
Thermal imagers can see in any conditions:
• Through the smoke, fog, heavy rain, or snow.
• Through foliage and branches of trees, bushes, dense grass in the field.
• Through thin walls and doors.
• Through flame.
Thermal imagers are often used to rescue people during disasters or catastrophes. Also, this technology is very effective in identifying the hottest areas during the fire. Modern models of thermal Imagers are very compact and can be mounted on a head or helmet.
Night vision devices have many advantages. And the more modern the goggles, scope, or binoculars you buy, the fewer flaws you will notice. It is important to understand for what purpose you need the equipment and in what cases you are going to use it. Do not rush to buy the most expensive and newest one, start with a model that stands in the middle of the evolution of NV devices.