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| Night vision devices gather
existing ambient light (starlight, moonlight or
infra-red light) through the front lens. This
light, which is made up of photons goes into a
photocathode tube that changes the photons to
electrons. The electrons are then amplified to a
much greater number through an electrical and
chemical process. The electrons are then hurled
against a phosphorus screen that changes the
amplified electrons back into visible light that
you see through the eyepiece. The image will now
be a clear green-hued amplified re-creation of
the scene you were observing. |
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|
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| 1. Front Lens |
4. High Voltage Power Supply |
| 2. Photocathode |
5. Phosphorus Screen |
| 3. Microchannel plate |
6.
Eyepiece | |
 |
| A Night Vision Device can be
either a 1st, 2nd, 3rd or 4th generation unit.
What this stands for is what type of light
intensifier tube is used for that particular
device The light intensifier tube is the heart
and soul of an NVD. |
1st
generation is currently the most popular
type of night vision in the world. Utilizing the
basic principles described earlier, a 1st
generation will amplify the existing light
several thousand times letting you clearly see
in the dark. These units provide a bright and
sharp image at a low cost, which is perfect,
whether you are boating, observing wildlife, or
providing security for your home. You may notice
the following when you are looking through a 1st
gen unit
- A slight high-pitched whine when the unit is
on.
- The image you see may be slightly blurry
around the edges. This is known as Geometric
Distortion.
- When you turn a 1st gen off it may glow
green for some time.
- These are inherent characteristics of a 1st
gen and are normal.
|
 |
 2nd generation is primarily
used by law enforcement or for professional
applications. This is because the cost of a 2nd
gen unit is approximately $500.00 to $1000.00
more then a 1st gen. The main difference between
a 1st and a 2nd generation unit is the addition
of a micro-channel plate, commonly referred to
as a MCP. The MCP works as an electron amplifier
and is placed directly behind the photocathode.
The MCP consists of millions of short parallel
glass tubes. When the electrons pass through
these short tubes, thousands more electrons are
released. This extra process allows 2nd
generation units to amplify the light many more
times then 1st generation giving you a brighter
and sharper image. |
 |
 3rd
generation By adding a sensitive chemical,
gallium arsenide to the photocathode a brighter
and sharper image was achieved over 2nd
generation. An ion barrier film was also added
to increase tube life. Gen. 3 provides the user
with good to excellent low light
performance. |
 |
 4th
Generation / Gated Filmless tubes: 4th
generation / Gated Filmless technology
represents the biggest technological
breakthrough in image intensification of the
past 10 years. By removing the ion barrier film
and "Gating" the system Gen 4 demonstrates
substantial increases in target detection range
and resolution, particularly at extremely low
light levels. |
The use of filmless technology and
auto-gated power supply in 4th generation image
intensifiers result in:
- Up to 100% improvement in photoresponse.
- Superb performance in extremely low light
level (better S/N and EBI)
- At least triple high light level resolution
(a minimum of 36 lp/mm compared to 12 lp/mm)
|
|
| With significant improvement in contrast
level and in performance under all light
conditions, 4th generation represents the top of
the line performance in the night vision market.
Note: The term 4th generation is used/accepted
among Night Vision manufactures to describe
gated filmless tubes. However, this designation
is widely debated and is currently referred to
as Filmless & Gated image intensifiers by
the US Military. |
 |
 |
 |
Gen 4
technology improves night operational
effectiveness for military users of night vision
goggles and other night vision devices. The
filmless MCP provides a higher signal-to-noise
ratio than Gen 3, resulting in better image
quality (less scintillation) under low-light
conditions. The gated power supply further
improves image resolution under high light
conditions, and the reduced halo minimizes
interference from bright light sources. These
improvements also substantially increase the
detection range of the systems.
| |
 |
 |
Gen 3 Omni IV |
Gen 4 |
% Improvement |
| Photoresponse (µA/Im) |
1800 |
1800 |
- |
| Signal-to-Noise
Ratio |
21.0 |
25.0(ground) |
20% Higher |
| 26.0(air) |
24% Higher |
| Resolution(lp/mm) |
64 |
64 |
- |
| Halo(mm) |
1.25 |
0.75 |
40% smaller |
| Reliability(hours) |
10,000 |
10,000 |
- | |
 |
RANGE
IMPROVEMENT
|
| Relative direction
ranges |
| PVS-7 System |
| Overcast Starlight Conditions
(-1x10E-5 tc) |
| Vehicle Size Target, 30%
Contrast |
 | |
 |
 |
Gen 2 |
SuperGen 2 |
Gen 3 OMNI I and II |
Gen 3 OMNI III |
Gen 3 OMNI IV |
Gen IV |
| Detection Range (m) |
170 |
270 |
240 |
290 |
360 |
430 |
% Improvement over Gen
II |
0% |
60% |
40% |
70% |
110% |
153% | |
|
| Gen IV technology is not
currently available for export.
|
|
|
All Starlight scopes need some
light to amplify. This means that if you were in
complete darkness you could not see. Due to this
we have a built in infra-red illuminator (IRI)
on all of our scopes. Basically what an IRI does
is throw out a beam of infra-red light that is
near invisible to the naked eye but your NVD can
see it. This allows you to use your scope even
in total darkness. The IRI works like a
flashlight and the distance you can see with it
will be limited. We do use the most powerful
eye-safe illuminator on the market. This allows
our IRI to extend out to 100 yards However,
because of the power at a short distance the IRI
may cover only 40-60% of the viewing area.
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There are many different variables
that can effect the distance that you can see
with a Night Vision device. First, what are you
trying to see? Are you looking for another boat
on the water or are you looking for a rabbit in
the woods? The larger the object the easier it
is too see. Plus, are you trying to see details
(what we call recognition range) or are you just
trying to see if something is there or maybe you
will just see movement but won't be able to 100%
determine who or what it is. This is called
detection range. Second. Another variable is
lighting conditions. The more ambient light you
have (starlight, moonlight, infrared light) the
better and further you will be able to see You
can always see further on a night where the moon
and stars are out then if it is cloudy and
overcast. We typically state that you can tell
the difference between a male and a female or a
dog and a deer at about 75 to 100 yards.
However, if you were looking across an open
field and there was a half moon out you could
see a barn or a house 500 yards away.
Remember, that the purpose of an NVD is to
see in the dark not necessarily a long ways like
a binocular. |
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|
As you look through a night vision
device you may notice black spots on the screen.
A NVD is similar to a television screen and
attracts dust and dirt. Typically these spots
can be cleaned. However, this may also be a spot
in the tube itself. This is normal. Most tubes
will have some spots in them. These black spots
will not affect the performance or reliability
of the night vision device. |