Types of Night Vision

Night vision allows you to see in low-light conditions when the amount of ambient light available is not enough for your naked eyes to see.
There are three types of night vision technologies that are in use today: Image intensified night vision, digital night vision and thermal vision. Each has its advantages and disadvantages and choosing the right night vision device depends entirely on what you want to use it for.

Image intensified night vision uses Image Intensifier Tubes (IITs) that amplify the ambient light between 1 000 and 30 000 times. IITs are divided into different "Generations" based on the technology used in them, namely Generation 1, Generation 2, Generation 3 and Gen 3 FLAG. These night vision generations differ in their low-light sensitivity and resolution. To put it in perspective Gen 1 will amplify the light about 1 000x, Gen 2 around 20 000x and Gen 3 more than 30 000x. In South Africa civilians are only allowed to purchase night vision up to Gen 2. Gen 3 and above is only available to the military, law enforcement as well as users in the possesion of an end user certificate.

Advantage: Good low light sensitivity (Gen 2 is much better than Gen 1). Can see further than what an IR illuminator can shine. Can work without an IR illuminator so it won't give away your position.
Disadvantage: Expensive. Effectiveness depends on the amount of ambient light that is available. It still needs some light to be able to see. Can be damaged by bright light. 

Digital night vision is a new type of night vision that uses a digital camera CCD or CMOS sensor that is sensitive to near-infrared light (790 nm - 940 nm). It is essentially a digital camera that does not have an infrared (IR) cutoff filter in front of the sensor. If you opened up a digital camera and removed the IR filter then you would be able to use it as a digital night vision camera. Digital night vision does not amplify the ambient light and instead relies on IR illuminators to see in the dark. An IR illuminator is a type of flashlight or LED that only emits light in the infrared range. This light is invisible to humans but the night vision can see it. Without an IR illuminator digital night vision is very poor.

Advantage: Cheap night vision, IR illuminators will allow you to see in complete darkness even in shadows. Digital night vision won't be damaged by bright light.
Disadvantage: Poor low light sensitivity. Can only see well as far as the IR illuminator can shine. Most IR illuminators produce a red glow in the device so it is possible for other people to see you when it is on.

Thermal vision is the ultimate night vision technology. Thermal vision uses a type of sensor called a Microbolometer Focal Plane Array to detect the difference in temperature of objects. All warm objects give off thermal radiation or far-infrared light and thermal vision can detect this energy in the range of 8 - 15 µm. This means that thermal vision can see in complete darkness and people or animals will stand out much more that the background so it is easy to spot them. It is very difficult to hide away from thermal vision making it ideal for law enforcement, security and military use. Due to the advanced nature of thermal vision there are restrictions on the quality of the devices that a civilian can buy.

Advantage: Needs no light to operate. Works during the day and night. Super easy to spot animals and people hiding in bushes. 
Disadvantage: Very expensive.

 

HOW IMAGE INTENSIFIED NIGHT VISION WORKS

Image intensified night vision uses image Intensifier Tubes (IITs) that amplify the small amount of visible light that is available many thousands of times so that it is brighter and you can see it.
Image intensifiers are made from Glass or Glass-Ceramic tubes with a Photo-cathode in the front, a Micro Channel Plate in the middle, and a Phosphor screen at the back.
Light enters the night vision device through the lens and is focused on to the photocathode which converts the light photons into electrons. A high voltage is applied across the tube which then accelerates the electrons. In the middle of the tube is a Micro Channel Plate (MCP) which is a thin wafer disc made of millions of tiny fiber optic tubes. These tubes are at a slight angle so that when the electrons hit the plate they bounce off the inside of the tubes. When the electrons strike the MCP they multiply thousands of times. The now amplified electrons travel and hit the phosphor screen at the back of the tube which converts the electrons back into photons. The phosphor screen produces an intensified image of what the device is looking at, which is usually green in colour but can also be black & white in some IITs which is called White Phosphor.

 

Types of Night Vision

 

Night Vision Monoculars

Night vision monoculars are single-tube, single-eye devices that can be used as handheld night vision or if the device is a multi-purpose night monocular with 1x magnification it can also be used as night vision goggles. Most NV monoculars have a magnification of 3x or 5x. Higher magnifications are rare because the higher the magnification the less light enters the device which reduces the overall effectiveness of the night vision. Monocular type night vision is the most common design because it uses only one lens and one tube making it the most affordable night vision. Most people want to have night vision binoculars because they are used to using daytime binoculars and don't want squint when looking through a monocular. When using a night vision monocular you don't need to close your one eye to see properly. The light from the night vision shining in your one eye is much brighter than the light reaching your unaided eye so your brain only provides you with the image that you see in the device. This means that you can look through the night vision monocular with both eyes open. Another advantage of a monocular is that your one eye will remain dark adapted so you will still be able to see around you when you stop looking through the night vision, with binoculars both eyes will become light adapted and night blind when you stop looking through the device. It will take several minutes for your eye to re-adapt to the dark. Night vision monoculars can also be used with a camera adapter mount that can attach to a camera or video camera which will allow you to do night photography. 

 

Night Vision Binoculars

Night vision binoculars have two image intensifier tubes and two lenses. They are used for long range observation over extended time periods. The advantage of binoculars is that it gives you depth perception and you can keep both eyes open more comfortably. The added depth perception isn't a big improvement over monoculars because with night vision the image clarity is not very high compared to daytime binoculars. The additional cost, size and weight of binocular night vision makes more suitable for static observation. The use of two IITs makes the price of binoculars twice that of monoculars.

 

Night Vision Bi-oculars

Night vision bi-oculars are also refered to as binoculars but they have one tube and one lens but two eyepieces. This gives you the ability to use both eyes when looking through the night vision without any distractions. Bi-oculars are more afforable because they only use one tube and one lens. They don't give any depth perception but this isn't an issue when using the devices for observation because you don't need to be able to judge depth at long ranges. 

 

Night Vision Goggles

Night vision goggles are available in 1x magnification monocular, bi-ocular or binocular configurations. Each has its own advantages and disadvantages.

Monocular goggles are single-tube, single-eye devices and they are by far the most commonly used type of night vision by militaries throughout the world. They are small, lightweight, cheap, multi-functional, and won't make the user night blind in both eyes. You can look through the device with one eye and still keep you other eye open for added peripheral vision and situational awereness. Multi-purpose mono goggles can be mounted behind a red dot or holographic weapons sight allowing you to use it as a night vision rifle scope. NV goggles will have a standard 1x magnification lens with the widest field of view (FOV) possible so that you can see where you are walking. Most night vision goggles based on the US Military PVS-14 or PVS-7 night vision systems will allow you to screw on a 3x A-focal lens or 5x A-focal lens to the front of the 1x magnification lens so that you can use it as a long range night vision device.

Bi-ocular goggles are single-tube, dual-eye devices usually based on the US Military AN/PVS-7 night vision goggles design. The advantage is that having both eyes looking through the device and not distracted you can focus better on what's in front of you. This does however limit your field of view down to about 40° and means that the user will have to scan around with their head in order to see what is going on around them. The single-tube, dual eye PVS-7 type devices are being phased out by militaries in favour of the multi-purpose PVS-14 goggles.

Binocular night vision goggles are dual-tube, dual-eye devices usually based on the US Military AN/PVS-15 night vision goggles design. Dual tube night vision goggles give the user depth perception so it can be used for night driving and pilots that fly aircraft at night. These devices are double the price of single-tube night vision devices because they have two IITs instead of one. 

 

Night Vision Rifle Scopes

Night vision riflescopes are weapons mountable night vision scopes that have an aiming recticle within the field of view. They are designed for shooting only and are not meant to be used as a handheld night vision. NV rifle scope magnifications are usually 3x, 4x or 5x but can go up to 10x. The larger the magnification the larger the lenses need to be. Night vision rifle scope lenses must be very strong to withstand the recoil from the rifle and as a result the lenses of high magnification scopes tend to be quite heavy, to the point that they can become too cumbersome for "walk and stalk" hunting. In South Africa night vision rifle scopes that have image intensifiers in them are not for sale to civilians. It is not illegal to own image intensified night vision but you can no longer buy it. Military customers that are interested in buying a night vision rifle scope can contact us for more information. Digital night vision rifle scopes are for sale to anyone.

 

Clip-on Night Vision Scopes

Clip-on night vision scopes, also called Day/Night scopes, are designed to be mounted in front of existing daytime rifle scopes or other optics like monoculars or binoculars. These devices simply clip-on to the front of your scope and allows you to convert your daytime scope into a night vision scope without the need to re-zero. Image intensified clip-on scopes are also not for sale to civilians.

 

HOW THERMAL VISION WORKS

Thermal vision allows you to see the heat given off by warm objects, people and animals. Thermal vision works by using a microbolometer sensor which can detect long-wave infrared light that is radiated by all objects. A microbolometer works by detecting and measuring the slight temperature differences of the heat of the objects and then displays this information as an image on a LCD screen for you to see.

A microbolometer is a uncooled thermal detector that can detect the long-wave infrared light given off by objects in the wavelength range of 8 - 14 μm. The infrared light used in IR illuminator and IR lasers for night vision is near-infrared light with wavelengths between 800 and 940 nm, which is much closer to the visible light spectrum.

A microbolometer is a silicon chip with pixels arranged in a focal plane array similar to that of camera CCD or CMOS sensors except that the pixels can measure the energy of the infrared light that hits it. Each pixel looks like a small table with two legs. The legs of the pixel are thermally insulated but are electrically conductive. When infrared light hits the pixel it warms it up which then changes the electrical resistance of the pixel. Sophisticated circuitry behind the chip measures the resistance of every pixel and then combines this data to form an image which is then displayed to the user.

Thermal vision works during the day and night and requires no ambient visible light or IR illuminators to work. It is a passive system which only gathers thermal radiation and emits no light which makes it idea for covert observation and hunting.Thermal vision rifle scopes are the best night vision scopes that you can get but they are costly

It is virtually impossible for a person or animal to hide from thermal vision. The heat given off by a person or animal is much more than that of the surroundings and therefore the person glow much brighter and will be easily spotted an almost any environment.

If you have any night vision related questions please feel free to call in on 021 851 32 84 and ask for our night vision specialists.

Thermal Vision Microbolometer