Light enters the human eye via the pupil and the lens present inside the eye focuses the image you see, which is detected by the retina. When you use a projector, the image is formed on the wall or the screen, the retina of the eye is like this wall. The retina comprises rods and cones which are sensitive to light. They detect the light and transmit the images to the brain.
Rods can detect movement and dim light; however, they cannot detect colors. The cones in the eye help us to see color, but they function only when there is very bright light and they lose their ability to see colors when it is dark. The human eye has 4 times the number of rods compared to cones.
This means that we can see very well during the day when there is light and we see many different colors and we can see reasonably well at night too because of the rods, but cannot see color, which makes everything appear in blacks, whites and grays.
Why Can't We See In The Dark
The eye structure of all vertebrates is the same and the pupil controls the amount of light that enters the eye by dilating or constricting. The lens focuses the image onto the retina and the information is transmitted to the brain, However, when it becomes dark, humans find it difficult to see while animals can easily see and hunt in the dark.
So, the question is, how do animals like cats and owls see in the dark? The answer to that is that firstly, animals have large eyes and nocturnal hunting animals like cats and owls have pupils that open quite wide and in fact, they open so wide that they cover the entire front of the eye. Owls have such large eyes that they occupy almost half of their skulls.
Also, the eyes of the nocturnal animals are physiologically different. Owls, for instance, have tubular eyes with a very large lens that is located very close to the retina. This allows a lot of light to fall onto the lens.
Also, nocturnal animals have a tapetum, a mirror-like layer located behind the retina which helps to maximize the light coming in. The eyes of nocturnal animals have a large number of rods and fewer cones, which helps them to see better in the night.
In the human eye, the cones connect to the circuits which transmit light or dark signals to the brain that helps to increase the sensitivity to movement and the edges of the various objects.
While nocturnal animals have a pathway via which the rods connect the dark circuits by means of cones which help them to see better in dim light or in the dark. The nuclei of the rod cells are also adapted for night vision in the case of nocturnal animals.
Basically, a night vision device or NVD is an optical device which lets images to be produced in dim light or in total darkness. Usually, NVDs are used by military and law enforcement personnel. NVDs are electro-optical devices which contain IT image intensifier tubes (IITs) that are shielded in a protective water-resistant casing and have a mounting system.
History Of Night Vision
The history of NVDs dates back to the times before the WWII and the first infrared devices were developed by the Germans and these were also widely used during the Vietnam War. These devices were termed as Gen 0 (generation zero) devices which amplified the light by around 1,000 times.
However, these devices were quite bulky and cumbersome to carry around. They were so large, that they need to be mounted on flatbed trucks, which made them quite visible and easy targets.
The M1 and M3 night vision devices, also known as the snooper scope or sniper scope were introduced during the WWII by the US Army and were also employed in the Korean War. These NVDs were active devices and made use of large-sized infrared light sources in order to illuminate the targets.
Through the 40s and 50s, the American Army collaborated with RCA (Radio Corporation of America) to develop the NVD technology and by the mid-60s, the first generation of NVDs came into existence, which did not require an infrared illumination to work.
During the Vietnam War, equipment such as the starlight scope was used, which allowed soldiers to fight in the jungles in low-light conditions. In the 70s, thermal imaging made an appearance on the NVD scene and this technology went through many improvements over the following decades.
In the 90s, NVDs played a very important role in Operation Desert Storm, giving the army the greatest advantage of advanced night vision. Today, NVDs have become so advanced that they can amplify light by over 50,000 times and the technology only continues to improve each day.
Types Of Night Vision Used Today
There are 3 kinds of NVD technologies – image intensification, active illumination and thermal imaging.
In image intensification, the image enhancers or intensifiers in the NVDs magnify the photons which are received from the various natural light sources such as moonlight or starlight. The image is intensified as the output visible light is much brighter than the light that comes in.
The NVD makes use of even the smallest amount of light available and augments it to provide better vision. The NVDs which work on the principle of image enhancement feature an image intensifier tube or IIT that collects and enhances the visible and infrared light.
Active illumination devices combine image intensification with another active light source, usually shortwave infrared or near-infrared light.
The energy of the light wave is directly proportional to its wavelength, which means that light with a shorter wavelength has more energy i.e. in the light spectrum, the violet light has the greatest energy, while the red light has the least amount of energy.
And, apart from the visible light, there is also the infrared or IR spectrum, which is divided into near-infrared (0.7-1.3 microns), mid-infrared (1.3-3 microns) and thermal infrared (3- 30 microns).
In the case of thermal imaging, the heat emitted by people, animals and objects appears as light at the top end of the IR light spectrum and this light is not visible to the naked eye. The night vision device that works by thermal imaging detects the heat emitted and creates an image, which is known as a thermogram.
Why Are Most Night Vision Equipment Green?
The eerie green tint that most night vision equipment have is by design. When the photons of light hit the lens of the NVD, they carry the light of all colors, even in the dark. However, when they are converted into electrons, this information is not preserved and all the incoming light is converted into black and white.
Night vision device manufacturers have discovered that when they are in green light, monochrome night vision images can be perceived and distinguished most accurately as our eyes are more sensitive to green light.
The green tint is most user-friendly and gives the wearer of the NVD the most accurate picture. Also, since the human eye is most sensitive to wavelengths of light close to 555nm, which is green, the display can be a bit dimmer, which helps to conserve the battery power of the NVD.
What Are Night Vision Generations And How Does It Affect Performance?
Just as all other types of technology, night vision devices have also undergone significant evolutions over time and several generations of night vision devices have emerged.
Gen 0 Devices
As we have already discussed earlier, night vision devices were invented as early as the WWII. The soldiers were not able to fight at night due to the inability to see in the dark and difficulty in communication. The first vision technology was developed in 1939 in Germany.
The Gen 0 night vision devices made use of intensifier tubes which worked using an S1 photocathode and anode. The scopes were made of cesium, silver and oxygen to produce electrons which made it easier for the scope to identify human targets.
Gen 1 Devices
The Generation 1 night vision devices were developed in the 60s and used during the Vietnam War. Today, they are among the cheapest NVD available in the market and include monoculars, binoculars and goggles using the technology.
The Gen 1 devices were essentially similar to Gen 0 devices and also made use of ambient light and were different compared to the traditional devices which made use of IR light sources. The Gen 1 devices made use of a S-20 photocathode, which allowed you to see images more easily than Gen 0 devices.
The gen 1 devices had image intensifiers that amplified the light up to 1,000 times; however, these devices were quite heavy and required some amount of moonlight to work.
Gen 1 night vision devices are not suitable for photography purposes as the quality around the images are not high-quality. However, the Gen 1 devices have many practical applications and are quite popular due to their affordable price.
The Gen 1+ devices that came soon after offered improvements over the Gen 1 devices in terms of better quality tubes and they also had a fibre optic plate in the tube which helped to enhance the image resolution and prevented distortion around the edges. The Gen 1+ devices provide an amplification of 900-1000 times.
Gen 2 Devices
In the Gen 2 night vision devices, the image intensifier tubes are much better than in Gen 1 devices and in addition, they made use of an electron amplifier i.e. the MCP (microchannel plate), which allowed the military snipers to get a better shot at the target. Since the Gen 2 devices made use of an S-25 photocathode, the images produced were much brighter around the lens edge.
The Gen 2 devices provided more illumination in dark conditions and provided 20,000 times more light amplification, the image resolution of these devices were better and they also offered better reliability, making the Gen 2 devices good for use in low light conditions. The Gen 2 devices were quite expensive, which made them suitable for use mostly by professionals.
Gen 2 night vision devices were followed by the G 2+ devices and these night vision devices had Supergen tubes and offered better optics, resolution. They were equipped with an automatic gain control which helped to regulate the image brightness depending on the external light conditions.
Gen 2+ devices also have flash protection and the images practically are free of any distortion around the edges. Until now, the Gen 2+ devices were used by the military only; however, in the recent years, they have been available for wider commercial use.
Gen 3 Devices
The Gen 3 night vision devices make use of the same microchannel plate as the Gen 2 devices but in Gen 3 devices, the photocathode is made of gallium arsenide, which provides images of much higher resolution with light amplification of 30,000-50,000 times. The Gen 3 devices are used by the military and special forces.
The Gen 3 night vision devices available today are easily the best and are quite expensive. Gen 3 devices provide several advantages. They offer viewing range up to 300 yards and more, most efficient low-light performance, excellent resolution and are very long-lasting, offering more than 10,000+ hours of usage.
Gen 4 Devices
The Gen 4 devices are fairly new and have not been officially accepted by the military. Gen 4 devices are also known as gated and filmless image intensifiers. These devices are filmless, as the ion barrier film which was present in the Gen 3 devices have been removed producing clearer images.
The Gen 4 devices are known as gated devices, as they have a power supply that allows usage even during the daytime. The Gen 4 night vision devices give excellent image resolution and a minimized halo effect. The Gen 4 devices are the most expensive and can easily cost around $5,000-$6,000.
What Are Civilian Uses For Night Vision Googles?
Apart from use for military purposes, today, night vision devices are being used for several day-to-day activities.
Today, increasingly, NVDs are being used in aviation because of the benefits they offer. NVDs help to increase the nighttime awareness for pilots. While it does not really convert night into day, it does allow pilots to see things that they would not normally be able to see with the naked eye.
NVDs also help to decrease the possibility of collision of the aircraft with man-made structures or terrains significantly and helps to increase flying safety in the night.
NVDs are being used increasingly by nature enthusiasts and hunters to maneuver safely through the woods in the dark. The NVD allows you to see the nocturnal animals that are not active during the day.
The night vision devices allow you to watch out for the game you prefer to hunt in the dark and identify it before taking a shot. NVDs help to enhance the experience of nighttime hunting making it more enjoyable without making use of other light sources such as flashlights, etc. that will only scare away the animals.
If you are after a predator which is a nuisance but is also very cunning, such as a coyote, using a high-quality NVD allows you to hunt the animal more easily at night, as you can venture into the woods or fields and spot them easily at night when they are active.
A good night vision goggle is a great accessory to have for a good nighttime hunting experience and it also can help to keep you safe when you enter and exit the hunting area. Also, with an NVD, you can be sure about the target you are going to take down and distinguish it from a domestic animal or a human.
Homes and farms can benefit largely by investing in a night vision device that can help in increased safety, apart from being useful for recreational purposes. NVDs allow you to see more clearly in the case of power outages or if you hear strange noises in your backyard, you can check it out safely with the help of your NVD.
NVDs also can be useful to monitor your livestock and view the backyard creatures that may visit you after dark or you can simply use the device for a bit of stargazing. NVDs allow to see more clearly and at a greater distance compared to using a flashlight.
Also, the NVD allows you to observe the animals or people from inside your home safely without being detected and you can also record what you see.
NVDs are great equipment that can be used at night in both natural, as well as the urban environment. They can be worn very easily and you can also mount the device on your helmet and go handsfree.
NVDs are great devices for exploring and will allow you to see clearly even in complete darkness and if you are out camping or on a trek, you can view the landmarks and features around you for a better orientation. You can also use your NVD to explore your neighborhood at night and get a surreal experience of the various objects and spaces around you.
While playing Airsoft, there are many times that you may encounter low light conditions, which makes playing difficult. Typically, to help in such conditions, players make use of weapon-mounted or handheld flashlights.
However, using NVDs can help to give you a greater advantage over your competition and you can see clearly without being detected by your opponent.
Types Of Night Vision Gear
Here are the most common:
NV goggles are meant to be worn when you’re moving or walking around at night. They offer hands-free operation in low-light conditions. As they need a mounting system to be used effectively, you require a helmet or some type of a mounting system to keep the goggles in place over your eyes. Night vision is quite popular and affordable too.
Night vision goggles cover both your eyes and come together in the middle where you can see a single image. Since your vision is confined, this can affect your depth perception as your peripheral vision is limited. NV goggles do not have an option to magnify things. Night vision goggles are usually used for nighttime hunting, a game of paintball at night, etc.
Night vision binoculars are quite similar to regular binoculars and have 2 eyepieces and front lenses along with a night vision intensifier tube. A night vision binocular makes use of only one intensifier tube and so it does not offer a greater range or performance than a monocular.
However, since you are making use of both your eyes, the NV binocular offers a more comfortable viewing experience. However, compared to an NV monocular, the binocular is more expensive and heavier too.
Since the NV binocular offers both night vision, as well as magnification, it is an excellent device for navigation on both, land and sea. NV binoculars are also very useful for professional and personal security.
NV monoculars are very lightweight and compact devices that have a single objective and one eyepiece. You can use a monocular as a handheld device, but it can also be weapon or head mounted. A key benefit of a monocular is that one eye is always adjusted according to the ambient lighting.
This is especially useful if you are moving continuously from dark to light where night vision is not needed. Monoculars are widely used for security purposes, such as to inspect property, when you need to use it for just a few minutes.
Night vision cameras essentially work either by amplifying the dim visible light such as starlight or moonlight or they work by making use of infrared radiations that cannot be seen by the naked eye.
NV cameras are great equipment that allow you to take pictures or shoot videos in the dark. This is especially useful for nighttime wildlife photography. NV cameras are also used for security purposes and they make use of IR light to illuminate the objects in the dark.
Are Night Visions Goggles Allowed For Hunting In My State?
Many states in the US have particular rules about making use of night vision devices for hunting and these rules vary often. While some states have specific date ranges where you can hunt at night, other states ban hunting completely, while other states ban hunting of certain animals.
When we speak of hunting, it mainly refers to game animals; however, vermin hunting if not regulated regarding the use of NV devices or nighttime hunting.
In states such as Alabama, the use of night vision for hunting is unlawful, whereas, in Alaska there are no specific rules about the use of night vision for hunting as long as it is within the specified time limit and in the specified months. South Dakota allows the use of night vision for hunting, but only for certain animals.
Some of the states that allow nighttime hunting with the use of NV devices are Arkansas, Florida, Georgia, Iowa, Indiana, Connecticut, Louisiana, Illinois, Idaho, Kentucky, Nebraska, Maine, Montana, Michigan, Maryland, Missouri and Massachusetts.
Since the laws vary quite a bit in each place, it is a good idea to check your local laws before you actually go out hunting with an NV device.
How To Take Care Of Your NV Equipment And Maintain It
Night vision devices are quite expensive and hence you must follow a few steps and take care of your NV equipment.
Night vision devices have become very popular in the recent years and have several applications and have found their uses among both professionals and civilians.
There are a huge range of night vision devices available both at stores locally, as well as online, not to mention that they are quite expensive too, which makes buying the right NV device a difficult choice. Our detailed buying guide can help to guide you about the best night vision device that is most suitable for your requirement.