There are advantages and disadvantages with night vision devices. I'll go through both area and not lean more advantages than disadvantages. Just having the ability to see in the dark is the point of greatest of all advantage. When you read on you will see that the night visions main objective was for the army, so I'll spend most of my time in this area.
Engineers and scientists Communications-Electronics Command (CECOM) Night Vision and Direction Electronics Sensors (NVESD) of the US Army have discovered ways to capture available electromagnetic radiation outside that portion of the visible spectrum to the human eye and they have developed equipment to enable the American soldier to fight well at night as during the day and "night is ours." night vision devices that provide night fighters with the ability to see, maneuver and shoot at night or during periods of reduced visibility. The Army uses two different types of night vision devices - and thermal image intensifiers. Intensifying-imaging devices based on light amplification and must have some light available. These devices may amplify the available light from 2,000 to 5,000 times. Thermal-looking infrared (FLIR) detectors - sometimes called "sensors" - work by detecting the temperature difference between an object and its environment. FLIR Systems are installed on some vehicles and helicopters.
Night vision goggles are electro-optical devices that enhance (or amplify) existing light instead of relying on its own light source. Image intensifiers capture ambient light and amplify it thousands of times by electronic means to display the battlefield to a soldier via a phosphor screen, such as night vision goggles. This ambient light comes from the stars, the moon or sky glow from distant manmade sources, such as cities. The devices are sensitive to a broad spectrum of light, of the visible to infrared (invisible). Users are not seen through night vision goggles, you look at amplifies the electronic image on a phosphor screen.
Light enters the night vision goggles through an objective lens and hits a cathode powered by a high power load from mains photo. The energy charge is accelerated through a vacuum inside the intensifier and strike a phosphor screen where the image is focused. The eyepiece magnifies the image.
A soldier can conduct his combat missions without any active illumination sources using only image intensifiers. The main advantages of image intensifiers as night vision devices are their small size, light weight, low power requirements and low cost. These attributes have enabled image intensifier goggles for individual applications headband soldier and led to hundreds of thousands of night vision goggles to be procured by the US Army. Research and development continues today on image intensifiers in the areas of spectral response of longer wave length, increased sensitivity, wider fields of view and higher resolution.
The view through night vision devices can be much like looking through a tunnel. Normal field of vision is about 190 degrees - but that is cut at 40 degrees with night vision devices. That side - or "peripheral" - the vision that is used, and the dangers that often is seen is just not there. To adjust for that you must constantly turn your head to look for the dangers on each side of the body that can not be seen in its narrow field of view. Usually both eyes (binocular vision) are used to collect the signals to help estimate the distance and depth of abject. However, with night vision devices that you are essentially using one eye (monocular) vision, which can pose real problems. For example, when you are using NVDs and lets see two objects of different sizes that are side by side, the largest object seems closer. Seeing overlapping objects through a night vision device, which is before "appears" to be closer - perhaps much more than what is true. In addition, some of the objects seen through night vision goggles may seem farther away than they really are. The reason for this is that we tend to associate the loss of sharpness of detail with distance. On the other hand, a light source that is not part of a terrain feature can look closer than it really is. It is important to be aware of these potential problems and users to night vision goggles tend to overestimate underestimate the distance and depth.
The eyes need time to adjust from day to night vision. That's why you can barely see when you walk into a dark movie theater during the day - eyes need time to adjust to the dark. The same is true with night vision goggles. Basically you're getting a bad opinion days, so when your night vision goggles is removed, the eyes need time to adjust to the dark. The amount of time it takes depends on how long you have been using night vision goggles. Most people reach about 75 percent dark adaptation within 30 seconds of the removal of glasses. This is especially important to consider if you are using your night vision goggles and binoculars - basically to raise their eyes and then lower them.