Introduction

Welcome! This page is meant to help newcomers find their way around the world of night vision.

Therefore it is only fair to say the information below is intended to give an easy overview and general outline of some of the science, terminology, function and peripherals.

While this means an experienced night vision enthusiast might (and probably will) find statements and information that is inaccurate, we ask these readers for understanding based on the intended nature of this page.

What is Night Vision?

What is light?

Not even physicists can actually tell you what light is. If you ask them, they will probably start talking about how light is both a wave and a particle, or neither.

When thinking about light in the context of night vision, it is best to think of it as particles travelling at the speed of light, where each particle has a frequency which defines which color it is.

Besides the visible spectrum of light there is a whole range of other wavelengths, for example the infrared spectrum. Infrared has a lower frequency than visible light. Night vision usually is most sensitive to near-infrared light. This type of light is often used in light sources when the unaided eye should not be aware of it, like security cameras or motion tracking.

Light will have a varying success of reflecting from surfaces and under night vision reflected light is what you most likely will be relying on when using night vision. That light might originate from the moon, the stars, human civilization (street lights, buildings, airports) or of course illuminators.

What does an analog night vision device do?

At its most simple it allows you to see in the dark, thousands of times brighter than the naked eye can. Obviously there is quite some technical detail going on within the device. Here is a simplified explanation with correlating links to a more in-depth descriptions of how this works.

As mentioned in the previous section light particles travel at different wavelengths. Night vision recieves an extended range of wavelengths compared to human eyes and particularly in the infrared spectrum. These wavelengths enter the device as light particles (scientific term is photons). These photons will be converted to electrons by what is called a photocathode.

Now that the light has been converted to electrons these electrons will be multiplied and accelerated, for example by using a microchannel plate. Then the electrons need to be converted back into visible light by using a phosphor screen. The electrons react with the phosphor screen which produces photons again, but now in a single wavelength that is visible to the human eye. So now we can see a produced image. Which is several thousand times brighter than what we’d see with the naked eye.

What does a digital night vision device do?

A digital night vision device will act much like your phone camera, except that it will generally have a larger sensor that has its Infrared filter removed. The whole process after the light hitting the sensor is all digital and the amplification of light is also done digitally. Currently the digital technology is way behind analog options. However these digital devices often do have onboard options to record video without the need of extra attachments and during normal use. Also there are some digital photographic cameras that have had their infrared filters removed to be more viable for use in astronomy and particularly low-light subject photography.

Applications

History

Whilst night vision devices have been primarily used for avionic applications after its invention, which was around 1929 in Hungary, the earliest adopters of night vision was the German Wehrmacht in the later years of WW2. With the ongoing war and the subsequent cold war, many other countries encountered the devices and so the "arms race" to see in the dark began to ramp up.

But widespread use of night vision would take many years yet. The aviation field has been a strong driving force in the developments and new technological discoveries that later have been adopted for military use.

These days it is employed on a way larger scale and some units across the world are all deployed with night vision. Night vision devices made their way over to hollywood, gaming and other media. With this wider spread of screentime the popularity of these devices is increasing. With technological improvements and widespread use the manufacturers obviously have been producing more and more devices meaning that the second hand market also has seen a steady growth. Both because functional image intensifier tubes that don't deliver enough for military contracts are sold on to distributors as well as complete units are being phased out in favor of newer and even higher performance units.

Applications of night vision

As mentioned before it was primarily used for military operations but the technology is currently implemented in various ways. Helicopter pilots, individual soldiers, tanks, boats, drones and more. For civilian uses we can clearly see a wide employment in scientific research, astronomy, wildlife observation, hunting and any other recreational use in the dark.

Buying and owning night vision devices

Things to look out for

When starting to look around to get yourself a device there are obviously a few considerations to make. As mentioned this technology goes back almost a 100 years so not all devices are made equal. A good reminder for first time buyers is to consider what they want to do with the device and look into which devices fulfil these criteria sufficiently.

Price is not always the perfect indicator: there are very expensive and modern devices that will outperform all others while there are also collectors items that are expensive because of their rarity or pristine condition but still do not preform as well as the newest and latest. It’s not uncommon that devices of these two very different natures have similar price-tags.

Besides looking at different specs and models its very important to set realistic expectations on the device you want to get. In the following paragraphs there will be a few points to consider and research before starting your actual search.

One of the first things to consider:

Be aware that some devices need an IR-lamp (illuminator is the technical term) emitting a beam of infrared light to function while others rely solely on available environmental light.

Emitting light is in some cases (for example in more "tactical" implementations) unfavourable but for surveiling your front door or observing animals in the dark without disturbing them it is more than sufficient. If emitting light is not an issue for you, you can look at earlier generations of devices as these will most often be cheaper compared to more advanced technology. An example of device that performs well enough in these situations is first generation digital night vision, often present in entry-level night vision hunting scopes.

If you do not want to emit light or don't wish to carry a whole set of IR lamps to see your surroundings then you would want to look at Gen. 2 or later.

These will be more expensive than Gen. 1 or digital units, depending on their quality and condition.

There is no shame in getting a Gen. 1 device if this suits your needs, there is no shame in just getting Gen. 2 instead of the newest: It all depends on your use case and the possibility to spend as much or as little money as needed.

Types of night vision devices

Binocular

Commonly referred to as ”binos” among enthusiasts. This device consists of two separate image intensifiers (tubes or digital sensors) in parallel and so allows users maintain a sense of depth perception. An added bonus of binocular units is the relative ease of getting used to them as opposed to a monocular device. These units are, as a rule, more expensive than units operating from a single tube.

Biocular

This device uses one amplifier but display its displayed image to both eyes of the user by a system of mirrors and prisms. This will help them adapt quicker and have a better sense of depth than a monocular. The effect of ”stereo vision” is however more inaccurate than binocular units. It is sometimes shortened to ”biocs” among enthusiasts.

Monocular

This type of device (referred to as ”mono” in everyday conversations) uses one amplifier and displays its image to one eye. They take longer to adjust to than both of the above types but it has the practical advantage that one eye will be quicker to adapt to brighter lights where a night vision device is not needed. This is the most common type entering the market these days alongside binoculars. Most likely this is what beginner purchasers end up getting.

Other types

While definetly rarer on the civilian market there are other categories and setup possibilities. For expediency we will leave these alone for the scope of this introduction.

Mounting Capabilities

There are many different accessories for mounting your nightvision device. It could be for astronomical purposes, for hands free movement or for photography.

Hands free movement

The most common and preferred method for handsfree movement is to mount the night vision device to a helmet, head harness or a "skullcrusher". To use a helmet or head harness it is typically required that they should come with an adapter plate / shroud. If present, it is possible to add a wide array of flip up night vision mounts from brands such as Wilcox or Norotos. In case of a monocular, you typically have to combine a mount together with an arm that holds the device in front of one eye.

Taking care of your gear

Care, maintenance, dos & don’ts

• Always remove the battery after use.
• Use only quality lithium batteries if you can, however alkalines are fine in a pinch.
• Use microfiber cloths with a cleaning solution, camera cleaning pens, or wet lens wipes.
• If your night vision goggle (or NVG) is wet from rain or has been out in sub-zero temp it is recommended to let it dry and/or reach room temp at an even pace before closing it up in its storage case to avoid condensation forming.
• Store your NVG with the lens cap on, in a dark and dry place.
• Turn your device off and use a protective lens cap when entering a brightly lit area.
  • Even a turned off device can develop blemishes when the lens is exposed to very bright light, e.g. (reflected) sunlight.
• Do not shine lasers (visual or ir-spectrum) into your NVG regardless of whether it is on or off.
• Do not open your NVG housing, and expose its internals, while batteries are plugged in.
• Consult a knowledgeable person before attempting to fix or modify your devices or accessories, there might be far less risky or delicate fixes available.
• It is highly recommended to also get sacrificial lenses to protect the actual lenses of your device.

Legality

In most countries, night vision technology falls under the category of dual-use items, meaning with both military and civilian purpose. Many countries impose laws specific to this category.

Always educate yourself on the laws that apply for the country you buy and own your equipment in, as well as import / export laws when buying or selling internationally, or when travelling.

For country specific information see Category:Country.

Glossary

Below is a work-in-progress list of technical terms, lingo and expressions one will likely encounter. For more in-depth information, follow the links.

Term(s)	Abbreviation(s)	Description
Image Intensifier Tube Image Intensifier	IIT I²	The core component of a night vision device. When focused, low light shines into it on one side, the phosphor screen on the other side will show an intensified image.
Signal-to-Noise Ratio	SNR	A number that indicates how good an image intensifier is at producing a clear (noise-free) image from a dark scene.
Resolution	Res.	A number that indicates how sharp the image produced by an image intensifier is.
Gain		A measurement of how bright the output image produced by an image intensifier is.
Fixed Gain		An image intensifier with fixed gain does not offer the user a method of gain adjustment.
External Gain Adjustment Circuit Manual Gain	EGAC	A component of some image intensifiers that allows the user to adjust the gain manually. Especially useful for monocular devices to allow reducing discomfort of only one eye being exposed to the bright output image.
Autogain		An image intensifier with autogain attempts to keep the output brightness constant throughout different lighting conditions. Modern image intensifiers both with fixed or with manual gain usually have some form of autogain. Thus, the term autogain is often used interchangably with fixed gain.
Gating Autogating	AG	Autogating is a method used by most modern image intensifiers to avoid overloading and as such damaging their internals when exposed to bright lights.
Chickenwire		Black straight lines that can form hexagonal or square patterns. Defect of the fiber optical output.
Fixed Pattern Noise	FPN	A hexagonal pattern made of black or white lines. Most Gen. 2 and Gen. 3 image intensifiers exhibit FPN in very high light and some also in low light. It is an artifact of how the MCP is constructed and no cause for worry.
Generation	Gen.	A number that denotes the technological generation of an image intensifier.
Date of Manufacture	DOM
Field of View	FOV	In night vision, FOV refers to how much of the user's field of vision is covered by the (usually circular) output image. Higher FOV requires less head movement to observe a scene.
Green Phosphor	GP	An image intensifier with green phosphor produces a monochrome green output image on the phosphor screen.
White Phosphor	WP	An image intensifier with green phosphor produces a monochrome white output image on the phosphor screen. Sometimes with a blueish or greenish tint, depending on the manufacturer.
Blemish	Blem	Completely dark areas of varying sizes and shapes in the output image where an image intensifier "burned out"., usually due to exposure to very bright light, e.g. lasers. Blemishes are permanent.
Burn-in Burn		Similar to blemishes, except that the areas aren't completely dark, but instead just less bright than the rest of the image, usually due to exposure to very bright light. Burn-ins are a precursor to blemishes, usually due to shorter or less intense exposure to the light source. Burn-ins can sometimes be partially or fully reverted by using blackboxing or whiteboxing.
Blackboxing		A method of stimulating the peculiar ”self-healing” process that some image intensifiers have been found to have, where the image intensifier is left running for extended periods of time in a completely dark enclosure.
Whiteboxing		Similar to blackboxing, except that the image intensifier is pointed at a uniformly bright surface, e.g. a wall lit up by a flashlight. Should be performed only as a last resort.
Emission Emission Point	EP	Permanent damage to an image intensifier manifesting itself in a single point or area in the image that is constantly bright. Emission points can get worse over time and thus image intensifiers with EPs should be avoided.
Ghosting		A temporary bright spot in the output image of an image intensifier caused by exposure to a very bright source which usually disappears after some minutes of operation. Ghosting is an indicator that prolonged or more severe exposure to the light source can lead to burn-in or blemishes.
Streaks		Dark or light streaks that form behind sources of light moving in the output image of an image intensifier. Only visible in some image intensifiers, they disappear very quickly. For many Gen. 3 image intensifiers they occur most easily during the first few minutes of operation. Autogating usually removes the streaks.
Scintillation		Bright spots which occur on the  image screen randomly in space and time.
Spot		A single black point in the output image, usually a defect introduced during manufacturing.
Peppering		Multiple tiny spots, can look like a darker cloudy area, usually a defect introduced during manufacturing.
Zone 1/2/3		A method to describe where on the output image an imperfection lies. Zone 1 is the inner 1/3 of the image, Zone 3 is only the outer edge of the image, and Zone 2 is the rest inbetween.
Going To Air		When there is a leak in the vacuum contained inside of the image intensifier a shadow will slowly start creeping into the output image of an image intensifier, either just from one side (like a waning moon) or from all sides. This process can be very fast or very slow. A tube that is "going to air" should be avoided, as it's irreversible and will mean total failure of the image intensifier at some point in the future.