Night vision goggles (NVG)

Night vision goggles (NVG) are a form of optical equipment that allows you to see in the dark. They are most often used by the military.

There are two common types of night vision goggles:

Passive night vision goggles — these pick up any light in the given area and amplify it several thousand times using an image intensifier. Working by the photoelectric effect. As a photon collides with a detector plate, the metal ejects several electrons that are then amplified into a cascade of electrons that lights up a phosphor screen. Often a dim star in the sky is enough to illuminate an entire field. This type is commonly used for war reporting, making the picture green. The color green is chosen because the human eye is most sensitive and able to discern the most shades in green.

Two American soldiers pictured during the Iraq War, 2003Active night vision goggles — these project infrared light (the same type used by a remote control), and produce an image from the light reflected back. These goggles may require an image enhancer to amplify the light. The feature is commonly found on home video cameras, as it suits most consumers' needs for seeing in the dark. Pointing a television remote control at this type of system produces a glaringly bright image.
There are currently goggles that combine both of these technologies to create images that are almost as clear as day. In addition to goggles, night vision technology is also used in rifle scopes, security cameras, binoculars, etc.

Using a Night Vision Device

Using a Night Vision Device by James Hunt


It's difficult to see in the dark. Unless there's some light peeking in through the window or from under a door, our vision is compromised. If we wait a little while, our night vision kicks in, allowing us to see somewhat better. It's not enough that we can read in the dark, but it should be enough to keep us from stumbling into furniture or tripping over the carpet. Sometimes though, our human night vision isn't enough and we need a little help.

That's where technology kicks in. Thanks to science we can use night vision to do all sorts of things. With the proper equipment we can hunt, take pictures or even fight wars in the dark. We can also perform surveillance and search and rescue missions.

Here's how it works: Your night vision product will take existing light and amplify it through an objective lens, which then focuses on an image intensifier. A photocathode located inside the intensifier converts the photon energy into electrons. The electrons in turn strike a phosphor screen creating a viewable image. In reality it looks like you're watching television on a green screen.

Atmospheric conditions can affect night vision. For instance, if it's cloudy, foggy, or overcast, night vision can be compromised. The clearer the night, the farther one will be able to see with night vision technology. It should also be noted that night vision shouldn't be magnified, as light is lost during the magnification process making it more difficult to see.

Night vision devices include: - Cameras - Binoculars - Scopes for firearms - Goggles

If you think that using a night vision device on a frequent basis might be harmful, you couldn't be more wrong. Night vision products are no more harmful than a television or movie screen. It doesn't emit radiation or other harmful rays and there's no reason for it to cause blindness.


About the Author
James Hunt has spent 15 years as a professional writer and researcher covering stories that cover a whole spectrum of interest. Read more at www.night-vision-central.info

Night Vision: Not Just An Ordinary Spy Device

Night Vision: Not Just An Ordinary Spy Device by Robert Thatcher


At the mention of night vision devices, images can come to mind like spy and action movies, soldiers scouring an area with the device at night, helicopters hovering overhead aiding the police in tracking fugitives or detectives using the device to spy on people they were assigned to track.

Night vision devices are actually light enhancing and thermal imaging tools. It makes a particular subject visible by the warmth it emits or observable by using limited light. It enhances a spectral range making the viewer see lights and images that would otherwise have been invisible to the bare human eye. The normal human eye is capable to seeing images that are confined to a certain electromagnetic spectrum that the brain interprets. Night vision devices may use another source of light that enhances images enabling the user to detect objects that improves the detection capacity of the normal eye.

In theory the human eye can see these weaker sources of lights but the brain has a way of filtering out these lights that we are only capable of seeing a very limited number of photons. With the aid of a night vision device, these photons intensified by the photo multiplier tube enables us to see different colors of lights in a subject. When seen though and NVD, an image that is nearly invisible becomes observable.

Many animals have this capacity to see through the dark. Animals that can hunt at night uses a larger optical aperture, an improved composition in the retina, optics that are more photo-efficient that enables them to use weak lights and see better in the dark.

Night vision devices that most people are familiar with are the night vision goggles. This night vision device has an image intensifier that converts weak lights from the near infrared spectrum to visible images that enables the eye to see objects as far as 200 feet in near complete darkness. This night vision device displays a green image because the peak sensitivity of the human vision is near the green range. It also uses two different technologies depending on your choice of the night vision device.

One uses the Image enhancement where the night vision device enables the viewer to see images by collecting tiny amounts of light that may already be imperceptible and amplifying it to make the image visible. The other is through thermal imaging where the heat emitted by the subject is used and translated into images. The principle is that hotter objects tend to transmit more light than the cooler ones like stones and trees.

Night vision devices were originally intended for military use to aid them in tracking down an opponent at night. It has evolved now into many different uses.

Lately night vision devices are finding use outside of the military and police detection work. When you are out camping, night vision devices could prove very helpful. Businesses have also been installing night vision devices within and without their properties to enable them to observe if something has been touched or changed during the night. Night vision devices are also proving to have invaluable aid in detecting soil that have been disturbed, buried objects, footprints and almost anything that needs to be determined in instances where there is very limited lighting.

Some of the more common applications for the night vision devices are entertainment, hidden-object detection, hunting, law enforcement, military, navigation, security, surveillance and wildlife observation


About the Author
Robert Thatcher is a freelance publisher based in Cupertino, California. He publishes articles and reports in various ezines and provides night vision resources on www.about-night-vision.info.