Night vision goggles use an electro optical imaging device which is able to detect both visible and near infrared energy sources and then is able to intensify these energy sources further in order to provide a visible image for viewing at night. Sometimes people will often refer to them as NVG's instead. Today's night vision goggles can either be held by a person in their hands or be mounted on to a helmet. Although the general public are able to obtain and use these night vision devices, more often than not they are used by law enforcement agencies and the military. Initially these devices were used by the military forces during the Vietnam war and have gone through many stages of development since then and currently the US Military are now using a 4th generation version of the ones originally developed. The prices of these night vision goggles can cost as little as a couple of hundred dollars to some of them costing around $6,000. However there are some 3rd generation goggles which are of a very high quality and can cost less than a $1,000 and are more widely available to the general public than the 4th generation ones are. There are two kinds of night vision goggles in use today and these are the passive and active. Passive night vision goggles are able to pick up any light within the immediate area where the person using them is located and then magnify this light several times over by use of the image intensifier. You will often see this type of night vision being used when reporters are reporting from a war zone and the pictures that you seen on the TV in front of you will have a green tint to it. The reason why green is used in most night vision devices is because the human eye is very sensitive and is able to discern things more clearly when it comes in various shades of green. Plus using green helps the user's eyes to readjust more quickly once the goggles have been removed compared to other colors that have been tried. The other type are active night vision goggles. They project an infrared light (the same which you will find in your TV or satellite remote control). They then produce an image to the user's eye because of the light that has been reflected back. However in order for these to be really effective an image enhancer may be required to amplify the light further. Today this kind of night vision device is often used in home video cameras and is certainly the most suitable for us to use in order for us to see adequately in the dark at night. But it should be noted that there are some night vision goggles which actually combine the two methods together.
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