Night Vision Equipment
A night vision device is an optical instrument that allows images to be produced in levels of light approaching total darkness. They are most often used by the military and law enforcement agencies, but are available to everyone. The unit includes an image intensifier tube, a protective and most likely water-resistant housing, and some type of mounting system.
Night vision devices gather existing ambient light (starlight, moonlight or infra-red light) through the front lens. This light, which is made up of photons is then changed to electrons which are then amplified through an electrical and chemical process. The electrons are then hurled against a phosphorus screen that changes the amplified electrons back into visible light that you see through the eyepiece. The resulting image will now be a clear green-hued amplified re-creation of the scene you were observing.
A night vision device is an optical instrument that allows images to be produced in levels of light approaching total darkness. They are most often used by the military and law enforcement agencies, but are available to everyone. The unit includes an image intensifier tube, a protective and most likely water-resistant housing, and some type of mounting system.
night vision devices gather existing ambient light (starlight, moonlight or infra-red light) through the front lens. This light, which is made up of photons is then changed to electrons which are then amplified through an electrical and chemical process. The electrons are then hurled against a phosphorus screen that changes the amplified electrons back into visible light that you see through the eyepiece. The resulting image will now be a clear green-hued amplified re-creation of the scene you were observing.
A Night Vision Device can be either a 1st, 2nd or 3rd generation unit. What this stands for is what type of light intensifier tube is used for that particular device. The light intensifier tube is the heart and soul of an NVD. The classification was initially introduced by the US manufacturers through the US government. European manufacturers do not abide by it
First generation devices are currently the most popular type of night vision in the world and are passive devices that rely on ambient light and not an infra red source. A first generation device will amplify the existing light several thousand times letting you clearly see in the dark. These units provide a bright and sharp image at a low cost, which is perfect, whether you are boating, observing wildlife, or providing security for your home. They are though quite bulky and require moonlight to operate properly.
Second generation devices are used by law enforcement or for professional applications. This is because the cost of a second gen unit is approximately $500.00 to $1000.00 more than a first generation device. They feature a much improved image intensifier resulting in a much brighter image, especially around edges of the lens. This leads to increased illumination in low ambient light environments, such as on moonless nights.
Third generation is the latest in night vision technology. By adding a sensitive chemical, gallium arsenide to the photocathode a brighter and sharper image was achieved. In addition, the inside of the device is coated with an ion barrier film for increased tube life. However, it is much more expensive. A third generation device is likely to cost more than $3000.00.
Fourth generation devices (Classified differently by the US Military) differ from third generation allowing the device to adapt instantaneously to changing light conditions. They also have significant improvement in contrast level and in performance under all light conditions, and consequently represent the top of the line performance in the night vision market. Price will also reflect this.
Infra-Red Illuminators
All scopes the above need some form of light to amplify either from the stars or moon. In complete darkness you would not be able to see. Many devices therefore have an in built infra-red illuminator. They work by sending out a beam of infra-red light that is not really visible to the naked eye but the device can see it. This allows the device to operate in total darkness. But just like a flashlight beam, the distance you can see with it will be limited by the strength of the infra red beam, usually a maximum of 100 yards with the most powerful types.
How Far Can You See
There are many things that can affect the distance that a night vision device will be of use. Obviously the larger the object, the easier it will be to see. A boat in the water will be much easier to spot than a rabbit in the undergrowth. Also you need to consider how much detail are you trying to see? Often you will be able to detect movement but not determine exactly what moved. Lighting conditions will also affect how far you can see. You will see amuch greater distance under a full moon than say a new moon and a lot more than a cloudy night when there is hardly a star in the sky. Most devices at an economic price will allow you to differentiate between a man and a woman or a dog and a deer at up to 100 yards but you will also probably see a something as large as a barn or hose at 500 yards over open fields.
The purpose of the device is to see in the dark not to act as a pair of binoculars or sniper’s sight.
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