Cobra Night Vision Frequently Asked Questions
1. How does night vision technology work?
Night Vision scopes and binoculars are electro-optical devices that intensify
(or amplify) existing light instead of relying on a light source of their own.
The devices are sensitive to a broad spectrum of light, from visible through
infrared. An accessory illuminator can increase the light available at the
infrared end of the spectrum by casting a beam of light that is not visible to
the human eye.
You do not look "through" a Night Vision product, you look at the
amplified electronic image on a phosphor screen.
Light enters the Night Vision product through an objective lens and strikes a
photo cathode that has a high-energy charge from the power supply. The energy
charge accelerates across a vacuum inside the intensifier and strikes a phosphor
screen (like a TV screen) where the image is focused. The eyepiece magnifies the
2. Why are the projected images always green using night vision
A Night Vision phosphor screen is purposefully colored green because the
human eye can differentiate more shades of green than other phosphor colors.
3. What is the main difference between Russian made and US made Night
The large majority of Gen. 1 and Gen. 1+ night vision products sold in the US
are of Russian origin, packaged and branded locally, usually by large optical
manufacturers. The United States produces primarily Gen 2 and Gen 3 night vision
technology, which is employed by and large by the military and other
governmental organizations, and far out of the reach of most consumersí
budget. Russia is the largest producer of Gen 1 and Gen 1+ image intensifiers in
the world. Russian made night vision equipment, which also owes its origins to
the Defense Industry, has always enjoyed a reputation of being among the best
quality in the world.
4. What is the effective viewing range of a Night Vision Device?
It varies anywhere from 30 to 300 meters [900 feet]. The maximum viewing
distance depends on the conditions of use. Overcast conditions, fog, rain etc.
may reduce the effective distance of a night vision viewer. An Infrared
illuminator will increase your viewing range, especially in enclosed spaces like
a warehouse, garage or other enclosed parameters.
5. Can I use a Night Vision device in extremely low light, or absolutely
no light conditions?
Yes. While it is true that your Night Vision device needs some available
light to work, it is still possible to see a bright image in low light or no
light conditions with the use of an Infrared Illuminator, which can be either
built-in or attached to the device. On most of our products, the Infrared
Illuminator is either standard, or available as an option.
6. Which Night Vision product would you recommend for a first-time
Either the Ghost with detachable IR or the Spirit.
7. What type of light source can be harmful to a Night Vision Device?
Your night vision device is designed to be used to assist your viewing in the
dark. It may be harmful and will likely damage the device if you use it during
the daytime or whenever there is sufficient light to see the object. Also keep
in mind that strong direct light, such as projectors, car headlamps, strong
flashlights and so on, may be harmful to your night vision unit if you direct
you device at the source of these intense lights.
8. Can a Night Vision device and/or Infrared Illuminator be harmful to an
All our Night Vision Optics products comply with FDA and international
regulations in terms of safety for an electronic device, similar to other
electronic devices such as televisions, and radios. Individuals with sensitive
eyes such as those who experience eye fatigue while watching television, may
experience the same sort of fatigue if they use their night vision viewer for a
9. Are Night Vision products waterproof?
In general no. Exposure to water and other liquids and even high humidity may
damage night vision devices that are not specifically protected against these
elements. All our models are weather resistant, which means they can
withstand short exposure to light rain or high humidity conditions.
10. Do you ship internationally?
We ship to a number of international locations, inclusive of Canada, Western
Europe, Australia and New Zealand, Japan, Hong Kong and other countries.
11. What type of batteries do Night Vision Optics devices use, and how
long will they last?
Night Vision devices use commonly available batteries, such as 1,5V AA
type, 9Volt square type, or 3V Lithium type. Generally the device will last up
to 20-40 hours of continuous use if the Infrared Illuminator is in OFF position.
If used with the IR Illuminator, expect 30-40% less operating time.
12. Does a high magnification device lend itself to better night vision
Not always. While a high magnification device in a lot of cases will increase
the viewing distance, image gain and resolution are key factors to quality
viewing. If a night vision binocular has a high magnification, of 7 times for
example, but a low resolution and image gain, then the object viewed from a far
off distance will be cloudy and dark. It is best to choose a night vision device
with a good combination of high image gain, high resolution [23 lin./mm and up]
and good magnification [2.0 or better].
13. What is the warranty-coverage on Night Vision products?
Every Night Vision Optics Dot Com device comes with a 12-month warranty on
parts and labor. For additional questions, consult your owner's manual.
14. Is it really safe to purchase online using my credit card?
Yes. Our secure server software (SSL) is the industry standard and the best
software available today for secure e-commerce transactions. It encrypts all of
your personal information, including credit card number, name, and address, so
that it cannot be read as the information travels over the Internet.
How Night Vision Works
People have numerous requirements to be able to see at
night, and powerful illumination systems have been available since the first
lighthouse went into service at Eddystone Rock, near Plymouth, Devon in November
1698. However, the drawback with all systems, until just prior to the Second
World War, was that they were simply methods of illumination, with the obvious,
and frequently very dangerous drawback, that everyone could see the source and
origin of the light. For this reason it became imperative during World War ll
that a solution be found for battlefield use, if a decisive advantage was to be
achieved by one side gaining the ability to operate at night.
This breakthrough came about in 1936, when the first
active Infra Red system was developed using a silver photocathode. These systems
were very bulky and extremely primitive by todayís standards, but at the time,
they represented a major military advantage. Active infrared systems continued
in use until the late 1970ís in some countries, but NATO forces were phasing
them out by the late 1960ís to be replaced by image intensifiers. The main
drawback of Active Infra Red systems was that to operate they required powerful
Infra Red Lamps, which meant that the range was restricted by the performance of
the lamp. In addition, although Infra Red light is not visible to the naked eye
(other than a very dull red glow if you are close to the lamp), a major problem
could arise during military use should both sides utilize Active Infra Red
systems, in that each side can see the light emitted by the others Infra Red
Lamp. Hence, you are back to square one. With the source of the light easily
identifiable the system is rendered virtually useless, and probably lethal, as
you would only have to shoot at the lamp to take out the person holding it. It
was at this point that new technology was urgently required, and Image
Intensifiers or Starlight Scopes were developed.
The advantage of these systems was that Infra Red Lamps
were no longer required, and for this reason they are referred to as Passive
Night Vision devices. The principle of operation, is that they pick up whatever
ambient light is available from the moon and stars, and amplify it so that the
signal is strong enough to energize a sensitive screen. In the case of the
earlier systems known as First Generation, or GEN1 (large numbers of which are
still manufactured today), the principle of operation involved a light amplifier
consisting of three elements enclosed in a vacuum tube.
The elements are: 1. The Photocathode 2. A Microchannel
Plate 3. A Phosphor screen.
The photocathode receives particles of light, known as
photons, through the front lens of the device which it then converts into
The microchannel plate consists of a cluster of Micro
Channels. The actual number of microchannels varies, but runs into several
millions, and are sometimes referred to as Rods. As the electrons travel through
the plate, bouncing several times against the walls of the channel, they are
accelerated and more electrons are created. This means that if one electron
enters the plate, thousands will exit the channel and hit the phosphor screen,
they then exit the screen as photons producing the green image, familiar to all
night vision equipment users, which is visible through the eyepiece.
It is this process which brings us to the important
subject that divides the good units from the bad, and that is the degree of Gain
provided by the tube. Although the following explanation is simplified to avoid
baffling you with unnecessary technical details, we hope that it will help you
to understand the difficulties encountered by the manufacturers of the tubes.
These problems centre not just on the continual need for development to increase
the gain, but also on image definition, which, to a great extent depends on the
number of channels that can be packed into the Microchannel Plate. It is for
this reason that the manufacturers produce several types of microchannel plate,
the main two being 18mm & 25mm, with the 25mm plate being capable of
carrying considerably more channels. The main difference between Generation II
and Generation III systems, (we will cover GEN. II + later) lies in the tubes,
and the front end or third element, the Photocathode. It is this component that
determines how many of the photons will be converted into electrons. In the
systems employing the very latest technology (GEN.III), sodium potassium cesium
antimonide (tri-alkali), is replaced by gallium arsenide, which is sensitive to
infrared radiation (with wavelengths of up to 9 microns). In addition, it is
important to bear in mind that with all night vision systems, each electron
impact in the microchannels, generates gas ions which move back to the
photocathode and impair its efficiency. However, in the case of GEN. III
systems, the gallium arsenide photocathode can sustain the loss resulting from
the build up of an ion barrier film. The less advanced GEN. II systems, using
sodium potassium cesium antimonide tubes (tri-alkali), cannot deal with this
build up and the performance is impaired.
SECOND GENERATION PLUS (GEN. II+).
Second Generation Plus is an enhanced version of the
earlier second Generation devices, but capable of operating further into the
infrared spectrum than GEN.II. However, as the designation implies, it is less
sophisticated than GEN. III, in that it evolved just prior to the change from
Tri-alkali tubes to gallium arsenide, which took place with the development of
Third Generation technology. GEN.II+ does offer a useful performance increase
over GEN. II systems, but is becoming less common since the development of third
generation equipment. The reason being, that in terms of price, they are not
much cheaper than third generation alternatives, but still suffer with most of
the drawbacks of the older technology.
IMAGE INTENSIFIERS AND INFRA RED LAMPS.
Although image intensifiers, regardless of generation,
all utilize available light, they cannot see in certain situations. The
following are just a few examples: in shadow, underneath leaf covered trees, in
barns and out buildings, between piles of materials in a yard, inside cars and
lorries, underground car parks etc. To summarize, if an area is pitch black with
no ambient light at all no intensifier will be able to intensify light that
doesnít exist. It is rather like playing a blank CD, you can turn up the
volume as much as you like, but the amplifier canít amplify something that is
not there. The principle with Night Vision Devices is exactly the same, and for
this reason infrared lamps still have a vital role. Firstly, they are
comparatively cheap, bearing in mind that American Police type lamps cost around
£50, and even 1,000.000 candle power lamps, which give incredible performance,
are under £200. They are therefore the cheapest way to get massive increases in
performance. For example, if you paid £1000 for a system and £200 for a
1,000.000 candle power lamp, you would have the performance of a system costing
several thousand pounds more. The only time you would hit a serious problem
would be if someone else was using a scope, and the lamp advertised your
position. Secondly, there is the problem of no go areas. An Infra Red lamp opens
up these areas effectively, and for this reason you should consider having some
sort of infra red illuminator to hand in case itís needed, or to assist the
scope on a night when thick cloud restricts moon and starlight.
We now come to the various types of illuminator which
basically consist of two options. Laser Illuminators and Infrared Lamps. Both
are highly effective, but our personal recommendation is that you opt wherever
possible for a lamp. As a rule, the range is greater, and in addition it will
not generally damage the eye if you look directly at it, whereas some lasers can
actually cause retina damage if you look straight at them. These lasers are what
is simply termed in the industry as non-eye safe. A reputable dealer will
generally know what is, and what is not eye safe on the market. For obvious
reasons it is an area where certainty is crucial, especially if children are
involved, as due to the fact that no pain is suffered, people can be unaware
that they have damaged their eyes until it is too late.
THERMAL IMAGERS (TI).
Thermal imaging is the latest type of equipment, and
whilst it performs a similar function to an image intensifier, in other ways it
has certain very distinct advantages. Firstly, it solves the problem mentioned
earlier, that when in zero light situations an image intensifier cannot operate
without the help of infra red light Although this is acceptable in civilian
circumstances, it poses great difficulties on the battlefield. Infra red lamps
are completely out of the question in this area, and thermal imaging wins hands
down, not only because it can operate in Zero light conditions, but it can also
operate in fog, smoke, snow and even when camouflage nets have been used to
conceal men and tanks.
HOW IT WORKS.
Thermal imaging works in the visible band of 0.4 to 0.7
Microns, and from 0.7 to 12 Microns in the infra red spectrum. Although thermal
imagers have been around for some time, it is only recently that they have
become a potential rival for the latest image intensifiers. This is because
until the current solid state models were developed, all thermal imageries
required a cooling system which was usually in the form of a nitrogen or
compressed air cooling bottle. Therefore they were extremely bulky, and due to
this restriction caused by size and weight, they were only suitable for tripod
mounting, fixed surveillance positions or reconnaissance. The way in which the
new models score is that they are uncooled, and having dispensed with the bulky
gas bottles that are no longer required, they have become portable. For example,
the Pilkington Lite weighs only 3.5kg. Also, with the new systems now being
solid state technology, they are easier to manufacture in large numbers, and
much less fragile than their predecessors.
For certain applications a thermal imager is vastly
superior to an image intensifier, in that it can find a person under snow, and
troops and vehicles hiding under trees. Methods do exist to defeat it, but it is
difficult. The best battlefield defence is a special smokescreen created by
firing salvos from 66mm projectors fitted to AFV hulls. These projectors use M76
grenades which produce a smokescreen of hot fragments that descend slowly and
can be topped up with more salvos. Special camouflage nets that dissipate heat
slowly can also be used, these are sold by Barracuda in Sweden, and Bridport in
The drawback at the current time of thermal imaging is
cost. With a basic system at around £10,000, thermal imaging is expensive,
especially when you consider an excellent image intensifier is only a fraction
of this cost. It must also be considered, that as with any system, it is only as
good as the operator behind it. As range increases people and cars simply become
a hot blob. For this reason, we believe it will be some time before thermal
imaging takes over from a good image intensifier in civilian applications, but
it definitely has its place, especially for tracking fugitives in open country,
or finding adults or children lost in remote areas.
It has become clear that third generation image
intensifiers are probably the final generation, and from here on we will just
see technical improvements, rather than the emergence of third plus or fourth
generation systems. The most likely future developments will go down the route
of combining thermal imagers and image intensifiers into one unit. This is
probably out of the question at the moment, as the system would be too bulky and
we donít yet have the technology to get it right. However, the ability to
alternate from one technology to the other at the flick of a switch would be a
huge breakthrough, and the logical path to follow. For this reason it seems a
virtual certainty that light weight combined systems will be in production
within 10 years, or perhaps sooner if circumstances demand it.
Generation 2 - Usually an S-25 (extended red) photocathode (with photosensitivity of 240-400 uA/lm) with a microchannel plate
(MCP) to achieve gain. Normally uses fibre-optic inversion. Gen II tubes provide good performance in low light levels and exhibit
very low distortion making them well suited for use with video or still cameras. They are equipped with automatic gain control,
flash protection and feature edge-to-edge definition. Resolution in the centre varies between 30-35 Ip/mm. They are more tolerant
of urban lighting than Gen 3 systems.
Generation 2+ - Based on Gen 2 tube technology, but has enhanced photocathode sensitivity (typical photosensitivity of 500-
600+ uA/lm). Resolution in the centre varies between 35-45 Ip/mm.
SuperGen - Based on Gen 2 tube technology, but with further enhanced photocathode sensitivity (photosensitivity of 600-700+
uA/lm). Resolution in the centre varies between 45-60 Ip/mm.
Generation 3 - Uses gallium-arsenide for the photocathode and a microchannel plate for gain. The microchannel plate is also
coated with a protective ion barrier film to increase tube life. Can produce more than 800 uA/lm in the 450 to 950 nanometer
(near-infrared) region of the spectrum. Gen 3 provides very good to excellent low-light-level performance and long tube life. Mil-
spec Gen 3 tubes show virtually no distortion. Resolution in the centre varies between 32-64 Ip/mm. Current US spec is Omnibus
4. In almost all countries where they can be sold, Gen 3 systems are limited to strictly military use.
Generation 4 - It now appears that the US may be classifying Omnibus 5 tubes as Gen 4 because they have been able to do away
with the protective ion barrier inherent in Gen 3 systems.