night vision by nightvision4u.com
Selloff4u
All About Night Vision Determining the difference between night vision
devices is not an easy task.
What is Night Vision and how does it work?
night vision allows the user to see objects and surroundings even
under the darkest conditions. Simply put the unit collects ambient
light, or uses light from an infrared illuminator, the intensifier
tube electronically amplifies this light and projects a green image on
the screen for the user to see.
1. How does night vision work?
The objective lens collects light that you cannot see with your naked
eye and focuses it on the image intensifier.
The intensifier amplifies the light many hundred or thousand times.
2 a. What is the difference between Generation 1, 2, and 3 night
vision devices?
night vision devices of all generations are evaluated based on a
universal rating system.
The three main criteria are System Light Gain, System Resolution, and
Photosensitivity.
- System light gain evaluates how many times a night vision unit is
amplifying the available light.
- System Resolution reveals information regarding the sharpness and
clarity of the amplified image.
- Photosensitivity determines the minimum light level and type of
light needed in order to function properly.
Gen. 1 Gen. 2 Gen. 3
Image Intensifier Light Amp. 300-900 20,000-30,000 20,000-30,000
System Light Amplification <1,000 <6,000 <6,0000
Resolution in the center, ln/mm 25-30 30-68 45-68
Resolution on the edge ln/mm 15-20 30-68 <45-68
2 b. How to tell Gen. 2 (or 3) from Gen. 1 device: Quick Rule of
thumb:
Turn off the unit. If it shuts off immediately - it is a Gen. 2 unit.
If the image remains for some time - it's a Gen. 1 unit.
2 c. Other companies claim to have products with 10,000, 20,000,
40,000 light amplification etc. Why?
The best US made 3rd. gen. devices that cost $10,000 USD have a 3,000
system light amplification. Anybody claiming higher is not telling the
truth and simply misleading the customers, who have no practical way
to verify those figures.
3. Why are domestic products so much more expensive ?
- Our products are made in Russia, where material and labor is much
cheaper than in the USA
- The only way to compare is Apples for apples- Gen. 2 US. made versus
Gen. 2 Russian made. US. is more expensive.
4. Can night vision equipment be used in daytime?
NEVER expose the opened objective lens of an active unit in daylight.
During the day objective lenses must be covered by caps.
There is a tiny hole in the cap to provide enough light for day time
operation. The unit may be turned on during daytime but the lenses
must be covered by caps.
NEVER aim an active unit at intense light sources (i.e. lights,
headlamps, campfires, the moon, etc.). This may damage the image
intensifier.
5. Why do I see some black or white spots in the viewer?
These are the cosmetic blemishes in the image intensifier which do not
affect the performance or reliability of a night vision device and
some number of varying sizes are inherent in the manufacturing
processes.
They can also be dirt or debris between the lenses which should be
removed by careful cleaning if the system is designed with
interchangeable optics.
6. Why do all night vision equipment have a small magnification?
Consider the distance you will need and the overall area you are
observing or searching. For most surveillance or search applications,
the higher the magnification or narrower the field of view, the
greater the number of times you need to scan an area to avoid missing
important objects or events. Usually a 1:1 lens with a 40- field of
view provides optimal performance. For long range observation or
weapon sight applications, the amount of magnification needed will
vary; however, be sure to consider the other performance
characteristics of the device; as the magnification increases, field
of view decreases and the F number increases, all reducing the amount
of light captured. Consequently, you will need an image tube with
excellent performance at very low-light levels and /or
high-performance lenses. Another factor involves the versatility of a
device if it is used in situations that may require different
magnification. How easily and quickly can the magnification be
changed? Is it necessary to open the system to install the optics? In
some cases, this may be inescapable, and the susceptibility of
internal components to damage should be considered.
7. Is night vision legal?
Yes, for all devices. Possession of a night vision device conforms
with Federal Firearms Regulations, as of February, 1993. However, use
of a weapon sight for hunting may be limited or illegal in your state.
Check with your local authorities.
8. Will it make me blind if I look at a bright object ?
This only happens in the movies. In real life, all of our devices have
automatic brightness control. The unit will adjust the output
according to the incoming light, and will shut itself off if
necessary.
9. I have heard it is unsafe to look into the Infra Red illuminator.
Is it ?
There is some base to this rumor. Many military night vision devices
utilize Lasers in their Illuminators, and some of them might not be
safe.
All of our products use low power infra red diodes, identical to the
ones used in T.V. remote controls, which are absolutely safe.
What To do and Not to do:
NEVER take the unit apart. This device contains high voltage, which
may be hazardous to your health!
NEVER expose the opened objective lenses of a unit to daylight. (Note:
1st generation units will still remain active for a few minutes after
switching the unit off). During the day, caps must cover objective
lenses. There is a tiny hole in the lens caps to provide enough light
for daytime operation. You can turn the unit on in the daytime, but
the caps must be on the lenses.
NEVER aim an active unit at intense light sources (i.e. lights,
headlamp, campfires, the moon, etc.) It will not make you blind like
in the movies, but it will harm the unit.- NEVER reverse the polarity
of a battery.
NEVER connect the unit to external power sources.
ALWAYS keep the objective lenses covered when not in use.
ALWAYS store in a warm dry place when not in use.
ALWAYS remove battery when not in use for a long period of time.
Glossary of terms:
Image Intensifier Tubes: Collects and amplifies light, which is then
displayed so the image can be seen by the viewer.
binoculars Vs. Monoculars: A night vision monocular is for use with
one eye and contains one image intensifier tube. A night vision
binocular is for use with both eyes and contains two image intensifier
tubes.
Generations: The qualities of different night vision systems are
graded by generations. Simply put, Gen 1 was developed first, but is
still in production because it is still sufficient for the average
consumer and the cost is affordable. Gen 2 came next considerably
increasing the quality of the image intensifier tube. Gen 3 followed
with an even better tube. Following this, some companies decided to
develop the Gen 2 technology and that leaves what is now referred to
as Gen 2+, which is consistently compared on par with Gen 3.
Infrared Illuminator: Allows for optimal use even in no light
conditions, completely eye safe, it gives off a light your eye cannot
see but that is received by the night vision device.
Resolution: measured in line pairs per millimeter (lp/mm) it is the
clarity or quality of the image seen on the screen. The higher the
number, the better the image quality. However, buyer beware, these
numbers are often inflated by some companies because it is impossible
for the average consumer to test this measurement
Magnification in night vision: Higher is not always better, and this
is one of the cases. The higher the magnification the lower the
brightness. Therefore with night vision you want a fairly low
magnification, after all you are trying to see in the dark not see
something far away.