How Night Vision Works
Night vision scopes and binoculars amplify existing light, allowing you to see in conditions too dark for the naked eye. Available light (photons) is collected by the objective lens and focused on the image intensifier. Inside the intensifier, a photocathode is "excited" by the light and converts the photon energy into electrons. These electrons accelerate across an electrostatic field inside the intensifier and strike a phosphor screen ( like a green monochrome TV screen) which emits an image that you can see. It is the acceleration of electrons which provides gain and enhances the image.

Night vision systems improve your ability to see in low-light conditions, but they cannot provide a useful image in complete darkness, where there is no available light to amplify. For use in caves, warehouses or any other location where no ambient light is available, an accessory infrared illuminator is required. The illuminator provides a light source for the system to amplify. An infrared illuminator is handy, even in conditions where a small amount of light is available, as it can provide enhanced imaging capability in very-low-light conditions and improve consistency of performance as the user moves from low to very-low-light locations. Many night vision devices available include IR illuminators.
 
Gen I
1st Generation is currently the most popular type of night vision in the world. Utilizing the basic principles described above, a 1st generation will amplify the existing light several thousand times letting you see clearly in the dark. These units provide a bright and sharp image at low cost, which is perfect, whether you are boating, observing wildlife or providing security for your home.
You may notice the following when looking through a 1st gen unit:

• A slight high pitched whine when the unit is on.
• The image you see may be slightly blurry around the edges. This is known as Geometric Distortion.
• When you turn a 1st gen off it may glow green for some time.

These are inherent characteristics of a 1st gen and are normal.
 
Gen II
2nd Generation is primarily used by law enforcement or for professional applications. This is because the cost of a 2nd gen unit is a lot higher than a 1st gen unit. The main difference between a 1st and 2nd gen unit is the addition of a micro-channel plate, commonly referred to as an MCP. The MCP works as an electron amplifier and is placed directly behind the photocathode. The MCP consists of millions of short, parallel glass tubes. When the electrons are released. This extra process allows 2nd generation units to amplify a light many more times than 1st generation giving you a brighter and sharper image.
 
How far can you see?
There are many different variables that can effect the distance that you can see with a night vision device. First, what are you trying to see? Are you looking for another boat on the water or are you looking for a rabbit in the woods?
The larger the object, the easier it is to see. Plus, are you trying to see details ( what we call recognition range) or are you just trying to see if something is there or maybe you will just see movement but wont be able to 100% determine who or what it is. This is called detection range. Second, another variable is lighting conditions. The more ambient light you have (starlight, moonlight, infrared light) the better and farther you will be able to see. You can always see further on a night where the moon and stars are out than if it was cloudy and overcase. We typically state that you can tell the difference between a male and a female or a dog and a deer at about 75-100 yards. However, if you were looking across an open field and there was a half moon out you could see a barn or a house 500 yards away. Remember that the purpose of a night vision device is to see in the dark not necessarily a long way like a binocular.
 
Black spots on the screen?
As you look through a night vision device you may notice black spots on the screen, a NVD is similar to a television screen and attracts dust and dirt. Typically these spots can be cleaned. However, this may also be a spot in the tube itself. This is normal. Most tubes will have some spots in them. These black spots will not affect the performance or the reliability of a night vision device.