Our aStore

How to choose a night vision device

Author: admin
Filed under: Buyer's Tips, Uncategorized, night vision
Date: Apr 15,2008

It is very important to note that affordable night vision optical systems require some light to work. This can be moonlight, artificial ‘ambient’ light or artificial infra-red light.

Image intensifying night vision devices are by far the widely used. The other type is thermal imaging, which ’sees’ only areas of heat on a body, or which have been left behind by some event or thing. Image intensification is also referred to as gain multiplication.The ‘trick’ with night vision goggles, monoculars and binoculars is that they collect infrared and visible light with the objective lens and focuses it on a battery powered image intensifier, which amplifies the signal as follows:

a photo-cathode inside the tube absorbs the light energy and converts it into electrons
the ‘image’ formed by the energized electron strikes a phosphor screen
the phosphor screen fluoresces, forming an image that the user sees through the eyepiece(s)
Note: the phosphor screen is colored green because the human eye can differentiate more shades of green than other colors, thereby providing very a realistic ‘gray scale’-like image.

Selection criteria 1: Light Amplification

As can be expected, the major difference between various ‘grades’ (and prices) of night vision devices is the quality and sophistication of the intensifier tube:

Generation 1

These instruments have medium gain values giving good images, and their intensifiers are made up of simple electrostatic tubes, which are able to amplify available light by 500-20,000 times. They work more or less as described above.

While Gen-1 night vision devices cost less and are almost always larger and heavier than instruments from the other categories, don’t turn your nose up at them because they’re ‘only’ Gen-1 (there was a generation 0 ). If you don’t have a big budget, and do not need to use your night vision device in very dark environments, then they make good financial sense. Note that Generation 1 night vision devices’ utility can be greatly expanded when infrared illuminators are used - even when there is ZERO ambient light present.

Generation 2

These are smaller, lighter and more energy efficient. are generally smaller in size and weight and use noticeably less current. These devices have microchannel plate added under the image intensifier, which ‘pre-amplifies’ the available light signal and thereby significantly improves light amplification - approximately 20,00-75,000 times amplification.

These are by far our most highly recommended grade if you can afford them - much harder to ‘outgrow’ than Gen-1.

Generation 3

These are very costly devices, and are naturally suited for those people whose lives (or livelihoods) depend on night vision, e.g. law enforcement, military, security personnel and even researchers.

As with anything, there are always enthusiasts that want to buy the ‘best’, and spend a lot of cash on Generation-4, which are full military-spec. We would only recommend those if money is not a problem

Selection criteria 2: Intended use

Night vision devices are frequently used for:

spelunking
scouting games
camping and exploration
observing wildlife
hunting
police surveillance
nighttime security

Once you are sure about what you will be using your device for, and what the worst operational conditions would be, you will need to consider: gain, range and image quality. In our experience, the latter two are primarily determined by the former, which is determined by the Generation/grade. Another thing to consider is whether you will be able to use an infrared illuminator (built-in or accessory), since they drastically improve range and image quality. Infrared illuminators are probably well suited for cave exploration, while they may not be for law enforcement tactical operations. Its quite easy to decide, but you must give it some thought.

While tempting, it is quite difficult to suggest a hard and fast formula for selecting a night vision device, so we’ll offer an example instead:

Some friends of ours are ardent paintball enthusiasts. Recently, they discovered that practicing for their ‘war games’ competitions at night while wearing night vision goggles is not only great fun, but really improved their competitiveness during the day. These guys may actually be onto something and it sounds like great fun, but we cringe at the thought of paint getting all over such fine devices (they claim it does not)! Certainly more exciting than a “Dinner in the Dark Party”, where guests wear night vision goggles while dining!

How we used their needs to recommend a night version device:

low light operation
no infrared illuminators
‘hands-free’
± only 75m range needed
very good clarity
wide angle view

We recommended ATN NVG7 Generation 2 Night Vision Goggles, since a Generation 1 device would not work well on very dark nights. Given how well those are working for the paintballers, we would recommend the same for law enforcement and security/surveillance personnel that may have to use their night vision devices during a tactical operation. Of course, if there is a bigger budget, then Gen-3 would be better - not for paint-balling though! Too expensive and sacrilegious …

Note: less magnification generally results in brighter, clearer images. Choose the lowest magnification you can live with.

In ending, we would like to comment on monoculars. It is our opinion that while monoculars are quite a bit cheaper than binoculars, they are too tiring on the eyes when used for extended periods. If you’re going to buy a handheld device, then we recommend buying binoculars over monoculars.