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Night Vision equipment is electronically enhanced optical device that enable us to see in near-total darkness.
Night vision devices consist of two major types: light amplification (or intensification) and thermal (infrared). Most consumer night vision equipment is light amplifying devices. This technology takes the small amount of light that's in the surrounding area (such as moonlight or starlight), 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 go through the channels, they strike the channel walls and thousands more electrons are released. These multiplied electrons then bounce off of a phosphor screen which converts the electrons back into photons and let's you see an impressive nighttime view even when it's really dark. The image will now be a clear green-hued amplified re-creation of the scene you were observing.
How do Night
Vision Devices operate?
Night
vision devices are similar to video cameras. Instead of focusing
the image on the film plane or CCD (video chip), the objective
lens focuses the image on one end of a light intensifier
tube. There it is turned into electrons, amplified, and accelerated
past a field-forming electrode to a phosphor-covered screen
where the image is inverted and focused by static electricity. The
phosphors glow brightly where struck by electrons, the same principle
by which fluorescent lights brighten a room. The observer looks at
the screen through an optical eyepiece
or eyepieces and sees the image.
A Night Vision phosphor screen is purposefully
colored green because the human eye can differentiate more shades
of green than other phosphor colors.
Night
Vision Device Buyer Guide
When choosing a night
vision device, the first and most important question that a person
needs to ask is, what is it going to be used for? Not all night
vision devices are made the same. Each device is usually designed
and engineered for specific function.
In general, night
vision devices are widely used for among others:
- Law enforcement and security
- Self-defense
- Hunting
- Camping and hiking
- Wildlife viewing
- Boating and maritime
The three primary technical factors one needs to consider when choosing
a model are gain, range, and image quality.
If you plan to use the device around the home and yard, select a scope
with moderate gain. Since you will usually
be looking at items which are usually less than 100 meters away, a
short objective lens with moderate
magnification is appropriate.
Gain
Can you see the viewed object in pitch-black conditions? How much
detail can you see? Since a night
vision device amplifies existing light, darker natural conditions
make it more difficult to produce a crisp image with good contrast.
Therefore, the moon and starlight act as natural amplifiers for night
vision devices while most are pre-equipped with hi power IR
illuminators. The IR
illuminator acts as an additional "flashlight" for the night
vision device, to give you high quality resolution
even when natural light sources are absent.
If you live in a well-lighted urban area, the surrounding artificial
light will give you plenty of illumination for using our affordable
night vision monocular
or binoculars.
Range
A night
vision device's range is generally a function of its gain,
magnification, and resolution.
As a rule, a powerful lens will give you higher magnification
for viewing far off objects, but it also decreases the amount of light
captured. The optimal combination is a high-speed lens with magnification
below 5x. High gain is required when viewing
distant objects, and plays less a role when viewing objects up close.
Night
vision binoculars are best geared for professional applications
requiring deep range. For hunters, night
vision rifle scopes and spotting
scopes give you the best tandem of gain
and magnification required for
hitting moving objects.
Image Quality
Image quality is dependent on the quality of resolution,
contrast, and distortion in images
produced by night
vision devices. Night
vision devices produce a green monochrome image which is typically
sharpest in the center and fuzzier around the perimeter. Good resolution
will give you the ability to distinguish details of far off objects.
High quality contrast will allow you to see objects against like color
backgrounds. Low distortion is reflective
of the minimized quantity of traditional "black
spots" which sometimes appear on the device's lens (a natural
phenomenon in the production process).
In most night
vision goggles for example, magnification
is sacrificed (1.0 magnification
is the industry standard) for wide fields of
view and sharp, crisp image quality.
Ergonomics
Size, weight and ease of use are important considerations. Lightweight devices are more comfortable during extended viewing. Since you will be using the device in the dark, the switches and controls should be positioned logically and be easy to use.
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