How Does Night Vision Work?

Before buying a device suitable for viewing at night,Phosphor screen: The image that you see is actually
you have to find out how night vision works. In thisnot the physical object itself, but a projected, amplified
article you will be introduced to topics like "amplificationelectronic image on a phosphor screen (like a green,
of light", "infrared illuminator" and "phosphor screen".monochrome TV screen), which glows with a green
Once you've familiarized yourself with these topics,colour. This is perfect, since the human eye can
you will understand the concept.distinguish more shades of green than any other
Night vision devices come in goggles, scopes,colour. You cannot see in colour with a night vision
monoculars and binoculars. In this article I will focus onlydevice.
on monoculars (only one objective lens) and binoculars.The eyepiece then magnifies the image for you to
The only technology which will be considered, is thesee.
intro-level known as Generation 1. Generations 2-4 areThe phosphor screens are not forever, but they will
highly sophisticated and used only in specialized niches,last for 1500-2500 hours - which is an awfully long time
like the military and security.for a non-professional user. However, this also means
Primary object of these devices: Unlike binoculars, theythat you should think twice before buying a used
are primarily intended to make it possible for you todevice, unless you know exactly how the previous
see in the dark, not to magnify distant objects or seeowner used it.
objects far away. For this reason night vision devicesIn addition to this, wrong use could also harm your
have low magnification, like 4x.device. They are supposed to be used in low light
Amplification of light: Being able to see at night is basedconditions. They do their job with the help of extremely
on the fact that there's always some light available atlight sensitive components. They will suffer damage or
night (from the moon, stars or from artificial sources).lose useful life when used in daylight or when
Night vision devices are sophisticated electro-optical"overloaded" by strong artificial light like flashlights,
devices that utilize the available light, by amplifying itheadlights or spotlights.
with a special tube to make seeing in the dark possible.Black spots on image area: The tubes used by this
Infrared illuminator: All quality instruments of this sorttype of device are never flawless, and every
have a trick up their sleeves. They provide extra lightintensifier tube will have blemishes to some degree.
(infrared) when the available light is not enough to getThese blemishes translate into scattered black spots
a bright image. They do that with infrared illuminatorson the image area. This is where price comes into the
(or accept supplementary IR illuminators). This illuminatorframe. Cheap devices will have more and bigger black
casts a virtually invisible infrared ray at the object atspots than the more expensive ones. The fewer and
which you are looking, the objective lenses of thesmaller the blemishes, the better the quality and
binoculars pick up the extra (infrared) light along withtherefore the higher the price.
the visible light which is available and this then results inYou should now know how does night vision work:
a brighter image.Available light is amplified, additional light is supplied by
All in all, the amount of light gain varies from 15,000 tothe infrared illuminator and the image is projected onto
40,000 times, depending on the quality of the this typea phosphor screen, which you then see through the
of instrument. The more light gained, the brighter theeyepiece.
image.