Night vision devices can be defined as electro-optical devices which are comprised of IR image intensifier tube enclosed in a protective casing with a certain type of mounting system. Many NVD’s can also include IR illuminators as well as telescopic lenses which take the form of night vision monoculars, binoculars, goggles or scopes. It is important to make the distinction between NVDs and Night Glasses because they are not just optical devices.
As far as the range of use for of night vision devices goes, they are mostly utilized by the military and law enforcement. However, in recent years they have become much more widely available for civilian use in night vision filming or photography, hunting and different sport activities like night hunting or paintball. The portable night vision cameras have more recently found their place as features on motor vehicles.
Types of NVDs
Night-vision goggles offer a hands-free option in low-light vision environments. Most of them have no magnification options. There are many uses for night-vision goggles, like hunting under the veil of night, or enjoying a night time paintball tournament.
Binoculars offer a great combination of night vision and magnification. What this means is that the night-vision binoculars can magnify the view with realistic depth perception. This feature makes them the perfect tool for navigation on both land and sea. Another great use for night-vision binoculars is for either personal or professional security reasons.
When it comes to night-vision monoculars, they are both lightweight and designed for fitting perfectly in one’s pocket. They are mostly used for security reasons, usually for inspecting a property and only for a few minutes at a time. An example of an affordable option for night vision monoculars would be Sightmark Ghost Hunter 2×24, with high quality image and resolution.
The sole purpose of night vision cameras is to enable taking pictures or making videos in the dark. This is a great piece of equipment for nocturnal wildlife observation.
The most common use of night-vision glasses is while driving at night or in foggy weather. They are also great for reducing the glare from oncoming headlights.
Night Vision Methods
There are two basic night vision methods:
This method is used in situations when there is barely any starlight or moonlight, so the night-vision device takes the small amount available and enhances it enough to allow better vision. Additionally, it also uses light at the low end of the light spectrum not noticeable to the naked eye. This process can be done either actively – with an infrared light source located in the device, or passively – by filtering colors and relying totally on ambient light.
With thermal imaging, the heat that objects, animals or people give off appears as light at the upper end of the infrared light spectrum, which is not visible to the naked eye. What thermal imaging night vision actually does is detect this heat and create an image with it. These images are called thermograms.
Generations and why they are important
Like all technology, night vision equipment has evolved significantly over the years. The performance to price ratio has gotten lesser, making way for several generations of night vision equipment. Generation is used for rating most commercially available night vision equipment, like night vision goggles, binoculars and monoculars. It is also used as a point of comparison for the level of technology incorporated into each specific unit.
Gen 1 Night Vision
Generation 1 optics were developed in the 1960’s and first introduced during the Vietnam War. They are currently the least expensive pieces of night vision equipment available on the market. Gen 1 night vision products include night vision goggles, binoculars and monoculars with this technology.
As far as specifications for Generation 1 devices go, each one employs a vacuum tube with photo cathode sensitivity of 120-280 microamperes per lumen and light amplification of 120-900 times the ambient light. The resolution with Gen 1 devices is 20-38 line-pairs per millimeter in the center of the image, while the maximum range goes up to 80m.
It is important to mention that Gen 1 night vision goggles and devices are not suitable for photography, because they often have a drop in quality around the edges of the image. However, they have numerous practical applications and due to their affordable price they are quite popular among night vision enthusiasts.
Generation 1+ Night Vision
Generation 1+ tubes offer a further improvement of the Gen 1 tubes with a fiber optic plate installed at the front or the back of the tube, allowing for a drastic improvement when it comes to the image resolution, preventing distortion at the edges. They provide a light amplification of 900-1,000 times and the sensitivity increases to nearly 300 microamperes per lumen. A great example of a Gen 1+ device are Armasight Vega Night Vision Goggles Gen 1+.
Gen 2 Night Vision
The Gen 2 devices differ from Gen 1 and 1+ because they use an electron amplifier – the Micro Channel Plate (MCP). Currently on the market there are two types of the intensifier tubes with MCP available – the 25mm and 18mm. Basically, the larger the diameter the more efficient the tube is. Still, it is important to keep in mind that it also needs a larger night vision unit.
As far as Generation 2 specification goes, the light amplification is set at around 20,000 to 30,000 times, making them very efficient in low light conditions. The fact that they have very little distortion makes them a good match for video or still cameras. It is important to mention that they have an increased sensitivity of 300-320 microamperes per lumen and also an increased tube longevity, double the Gen 1 and 1+ have (Gen 2 4,000-5,000 hours, Gen 1 and 1+ – 2,000-2,500)
Considering the higher cost of the Gen 2 night vision equipment, it is mostly used by law enforcement or other professional services.
Generation 2+ Night Vision
Generation 2+ devices are equipped with automatic gain control that helps regulate the brightness of the image depending on the outside light conditions. Another great feature of Gen 2+ units is flash protection and an image which is virtually distortion-free even at the edges. Until recently, this type of night vision units was used only by the military. However, they have now become more widely commercially available.
It is important to mention that all Gen 2+ tubes are Russian-made because the US switched from Gen 2 directly to Gen 3. Russian legislation states that the maximum sensitivity allowed for export outside of Russia is 350 microamperes per lumen.
Gen 3 Night Vision
Gen 3 Autogated is used by both US military and special forces. Gen 3 is currently the best on the market but not very budget-friendly. When it comes to the advantages provided by Generation 3, they include: 300 yard plus ranges, best resolutions, most effective low-light performance and the longest life expectancy – 10,000+ hours along with a high level of reliability and durability.
Gen 4 Night Vision
The Generation 4 night vision technology is still quite new and not officially accepted by the military. Another term used for Gen 4 units is filmless and gated image intensifiers. Filmless because of the ion barrier film added to the Gen 3 image-intensifiers has been removed allowing for clearer images. Gated refers to the power supply, making it possible for the night vision unit to be used during daytime, along with the improved image resolution and minimized halo that appears due to the bright light sources.
Naturally, all these modifications lead to a substantial increase in the price range, bringing it to around five to six thousand dollars for Gen 4 monoculars in the US.
Night vision basic specifications
Some of the basic specifications for most night vision products are:
Resolution – can be defined as the ability of an image intensifier (resolution measured in line pairs per millimeter) or night vision system (measured in cycles per milliradian) to distinguish between objects close together. The image intensifier resolution remains constant while the system resolution can be affected. In the same night vision device, like night vision goggles, the resolution can differ when measured at the center of the image and at the edges.
Magnification and FOV – when deciding on magnification and FOV it is important to take into account the distance that you need as well as the size of the area that is going to be observed and searched. For optimal performance use a 1:1 lens with a 400 FOV.
Spectrum – Human vision is confined to a small portion of the electromagnetic spectrum – visible light. What the enhanced spectral range provides the viewer with is the ability to take advantage of the non-visible sources of electromagnetic radiation – near-infrared or ultraviolet radiation. The ultraviolet region extends from 100 to 400 nm with the near-ultraviolet nominally 300 to 400 nm, while the visible portion of the spectrum can extend from 400 to 750nm. On the other hand, the infrared region extends from 750 to 2xlO5 nm with the near-infrared nominally 750 to 2,500 nm.
Weather Resistance – one of the most important specifications when it comes to night vision systems is their ability to operate under various environmental conditions. The night vision units that have been built to U.S. mil specifications can withstand almost any environmental conditions. The most common issue for such units as night vision goggles is internal fogging which tends to reduce visibility. That is why the ability to resist humidity and moisture is so important.
Size, Weight and Ease of Operation: These three factors might be considered the most important when it comes to choosing the right night vision units, because if a unit is not comfortable to hold and easy to operate it will be of little benefit to the user. How does this apply to night vision devices – well, if the user needs to be mobile while using night vision goggles then they should choose a smaller, lighter model. On the other hand, if the device is intended for viewing from a static position, a larger model is a more suitable option. Regardless of the model, switches and focus control have to be positioned in such a manner that they can easily be adjusted.
Power source – batteries: All night vision devices made for civilian use are powered by batteries – alkaline or lithium. So when buying a pair of night vision goggles, users should always take into consideration the additional costs that come from restocking batteries. While cheaper and easier to get alkaline batteries are less durable, lithium batteries provide longevity and they can be bought at chemist/camera shops.
Top 5 Performance Factors for Night Vision Devices
- 1. Clarity – Clarity is directly connected with the resolution, which we have dealt with in the previous section. The relation is quite simple – since the resolution is measured with lines per millimeter, the higher the lines the greater the quality will be.
- Range – when dealing with night vision scopes, it is important to know the necessary recognition range. Regardless of all the technological advances, night vision technology has still not reached the point where it can function as a rifle scope, having the ability to see over hundreds of yards. The total range is not nearly as important as the recognition range of a night vision scope. Most manufacturers release recognition ranges for different lighting conditions like full moon, quarter moon, starlight only, or overcast. Naturally the range decreases as the amount of light decreases, since night vision quality depends on the available light.
- Ergonomics – with night vision devices, the higher the magnification the bigger and heavier the optics. For freedom of movement and comfort, use a lighter optic while heavy optics are meant for static observations.
- Durability – if you are about to spend several hundred or even thousand dollars on a piece of night vision equipment, it needs to be a long term investment. So before deciding on the make and model, consider the following features: is it waterproof (if not, do not use it in rain and snow) than check the quality of the electronic parts since they are most likely to break, and finally the optics – for example, some can withstand a 300 Win Mag, others cannot.
- Infrared Illuminators (IR) – when buying a night vision device, one should always pay attention if it has an infrared illuminator, or the option to have one attached. The purpose of an infrared illuminator is to shine an infrared light, making the night vision brighter. This addition is especially useful in situations where there is a total lack of light. It is important to mention that IRs have a limited range, depending on their size.
Is Night Vision Legal?
In the US, purchasing and selling any type of night vision equipment is considered legal. The only exception is for night time hunting – in this case it is advisable to consult the regulation of each state.