GENERAL OVERVIEW:
Click on the image to your right to watch the new "How Night
Vision Works Video producted by ITT Industries. Night Vision technology
consists of two major types: image intensification (light amplification)
and thermal
imaging (infrared).
Most consumer night vision products are
light amplifying devices. Light amplification is less expensive than thermal, however, higher-end and more effective night vision tubes can become more expensive. Light amplification technology takes the
small amount of light, such as moonlight or starlight, that is in
the surrounding area, and converts the light energy (scientists
call it photons), into electrical energy (electrons). These electrons
pass through a thin disk that's about the size of a quarter and
contains over 10 million channels. As the electrons travel through
and strike the walls of the channels, thousands more electrons are
released. These multiplied electrons then bounce off of a phosphor
screen which converts the electrons back into photons and lets you
see an impressive nighttime view even when it's really dark.
 All
image intensified night vision products on the market today have
one thing in common: they produce a green
output image. Like the one your see to your right - >>.
But that's where the similarities end.
In the night vision world there are generations
that reflect the level of technology used. The higher the generation,
the more sophisticated the night vision technology.
Generation 0 - The earliest
(1950's) night vision products were based on image coversion,
rather than intensification. They required a source of invisible
infrared (IR) light mounted on or near the device to illuminate
the target area.
Generation 1 - The "starlight
scopes" of the 1960's (Vietnam Era) have three image intensifier
tubes connected in a series. These systems are larger and heavier
than Gen 2 and Gen 3. The Gen 1 image is clear at the center
but may be distorted around the edges. (Low-cost Gen 1 imports
are often mislabeled as a higher generation.
Generation 2 - The microchannel
plate (MCP) electron multiplier prompted Gen 2 development in
the 1970s. The "gain" provided by the MCP eliminated
the need for back-to-back tubes - thereby improving size and
image quality. The MCP enabled development of hand held and
helmet mounted goggles.
Generation
3 - Two major advancements characterized development
of Gen 3 in the late 1970s and early 1980s: the gallium arsenide
(GaAs) photocathode and the ion-barrier film on the MCP. The
GaAs photocathode enabled detection of objects at greater distances
under much darker conditions. The ion-barrier film increased
the operational life of the tube from 2000 hours (Gen 2) to
10,000 (Gen 3), as demonstrated by actual testing and not extrapolation.
Generation
4 - Myth vs. Fact
Some say that generation (Gen) 4 is the most advanced night vision you can buy. This is not the case. To dispel this myth, let's start with the basics. There are four Generations of night vision; however, they are Gen 0-3, not Gen 1-4. Historically, the U.S. Army has defined each Generation of night vision. In the late 90's the Army did define Gen 4 as the removal of the ion barrier film creating a "filmless" tube. This new advancement was to reduce halos while increasing sensitivity, signal-to-noise ratio (SNR) and resolution, for overall improved performance. While performance was improved, the lack of an ion barrier in Gen 4 tubes led to high failure rates, ultimately leading the U.S. Army to recant the existence of Gen 4 definition. Recognizing the high failure rates of Gen 4 tubes, ITT chose to improve upon the existing Gen 3 technology and create a "thin-filmed" tube. By keeping the protective ion barrier, but greatly reducing its thickness, ITT was able to maintain the reliability of Gen 3 while—at the same time—delivering on the Army's performance requirements intended for Gen 4. This innovation resulted in the production of the Gen 3 thin-filmed tube, which is now the highest performing Gen 3 tube available. Not long after, the gated power supply was added and the PINNACLE® tube was born. The Generation 3 PINNACLE® tube is the most advanced night vision manufactured to date.
See also: Night Vision Terminology
When discussing night vision technology, you also
may hear the term "Omnibus" or "OMNI". The U.S.
Army procures night vision devices through multi-year/multi-product
contracts referred to as "Omnibus" - abbreviated as "OMNI".
For each successive OMNI contract, ITT has provided Gen 3 devices
with increasingly higher performance. ( See range detection chart
directly below) Therefore, Gen 3 devices may be further defined
as OMNI 3, 4, 5, etc. Current Omnibus contract as of 2006 is OMNI VII.
If you're using night vision to find a lost person
in the woods(rescue), to locate boats or buoys on the water (surveillance), to stargaze
into the wilderness, you need Generation 3 because it creates the
best images when there is very little ambient light. Generation
2 may be the choice in situations with higher levels of ambient
light like a city type environment, however, the cost difference between and good Generation 2 system and a Generation 3 may not be worth the lost opportunity to use the NVD (night vision device) in different environments.
KEY GENERATION DEVELOPMENTS:
Expected Operating Life (in hours)
Beyond
outperforming all previous technologies, corresponding improvements
in reliability have been equally dramatic. GEN III intensifiers
have a useful operating life of 10,000+ hours, making tube replacement
virtually unnecessary. The intensifier tube normally represents
75% of the overall system cost.
There are three important
attributes for judging performance. They are: sensitivity, signal-to-noise,
and resolution. As the customer, you need to know about these three
characteristics to determine the performance level of a night vision
system. See also: ITT Night Vision
Sensitivity, or photoresponse,
is the image tube's ability to detect available light. It is usually
measured in "µA/lm," or microamperes per lumen.
That's why many of our products do not come with standard IR illuminators.
With many applications illuminators aren't necessary. Some manufacturers
put IR illuminators on their products in order to get acceptable
performance under low light conditions.
Signal-to-noise
(SNR) plays a key role in night vision performance. The microchannel plate
is used to transfer a signal from input to output, a lot like a high-end
stereo gives you quality sound. It's akin to rabbit's feet on your old TV, when you move them to dial in the signal. With night vision, it's how the MCP is able to transfer signals inside of the image intensifier tube to give you the final product, i.e. the amplified image.
Resolution
is the third major consideration when purchasing night vision. This
is the ability to resolve detail in your image. Some manufacturers
put magnified optics in their systems to give the illusion that
they have high resolving systems. In the trade-off, field of view
is sacrificed. Some models give the option of higher magnification
so you can have it if you want it, not because your system needs
it to function effectively. Most of Morovision's products offer
a uniquely formulated phosphor to create the highest contrasting
images, therefore generating the highest resolution products available
to the consumer.
Distance and Magnification Charts:
*Chart based on night vision system with 1x lens. Recognition range will increase when greater magnification is used.
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Characteristics of Night Vision
Textures, Light and Dark
Objects that appear light during the day but have a dull surface
may appear darker, through the night vision unit, than objects that
are dark during the day but have a highly reflective surface. For
example, a shiney dark colored jacket may appear brighter than a
light colored jacket with a dull surface.
Depth Perception
Night vision does not present normal depth perception.
Fog and Rain
Night vision is very responsive to reflective ambient light; therefore,
the light reflecting off of fog or heavy rain causes much more light
to go toward the night vision unit and may degrade its performance.
Honeycomb*
This is a faint hexagonal pattern which is the result of the manufacturing
process.
Black Spots*
A few black
spots throughout the image area are also inherent characteristics
of all night vision technology. These spots will remain constant
and should not increase in size or number. See example below of
an image with black spots.
*
Do not be concerned if you see this feature-it is an inherent characteristic
found in light amplification night vision systems that incorporate
a microchannel plate in the intensifer.
See also: How to Buy Night Vision Equipment
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