Night Vision Device
Do any of you have a night vision device (NVD)?
There are many applications for a night vision device including uses for the military, law enforcement, security, surveillance, hunting, wildlife observation, navigation, hidden-object detection, entertainment, and more.
Although a night vision device will be an expensive addition to one’s supply of preparedness goodies, a night vision device could prove itself invaluable under some circumstances.
Here is some information how NVD’s work, and the differences in technology of the various generations (GEN-0,1,2,3,4…)
How Night Vision Works
A night vision device is an image enhancement technology system. It relies on a special tube, called an image-intensifier tube, which collects and AMPLIFIES any available visible and infrared light (which the eye cannot detect alone).
A lens captures ambient light and some near-infrared light. The gathered light is sent to an image-intensifier tube. In most night vision devices, the power supply for the image-intensifier tube is from batteries. The tube outputs a high voltage, about 5,000 volts, to the image-tube components.
The image-intensifier tube has a photocathode, which is used to convert the photons of light energy into electrons.
As the electrons pass through the tube, they are amplified by a factor of thousands.
At the end of the image-intensifier tube, the electrons hit a screen coated with phosphors (which provides the image) and is viewable via another lens. These phosphors create the green image that has come to characterize night vision.
Night Vision Devices (NVD’s) have been around for more than 40 years and are categorized by generation. Each substantial change in night vision device technology establishes a new generation.
Generation-0 Night Vision
GEN-0 The original night-vision system created by the United States Army and used in World War II and the Korean War, these NVDs use active infrared.
An IR (Infrared) Illuminator is attached to the NVD which projects out a beam of infrared light, similar to the beam of a normal flashlight, to ‘light up’ the area in front. This infrared light is invisible to the naked eye, but this beam reflects off objects and bounces back to the lens of the NVD.
These original systems (tubes) use an ‘anode’ and a ‘cathode’ to accelerate the electrons; but the problem with that approach is that the acceleration of the electrons distorts the image and greatly decreases the life of the tube. Another major problem with this technology in its original military use was that it was quickly duplicated by hostile nations, which allowed enemy soldiers to use their own NVDs to see the infrared beam being projected by the device.
Generation-1 Night Vision
GEN-1 The next generation of NVDs moved away from active infrared, using passive infrared instead. Once dubbed Starlight by the U.S. Army, these NVDs use ambient light provided by the moon and stars to augment the normal amounts of reflected infrared in the environment.
This means that they did not require a source of projected infrared light. This also means that they do not work very well on cloudy or moonless nights. Generation-1 NVDs use the same image-intensifier tube technology as Generation 0, with both cathode and anode, so image distortion and short tube life are still a problem.
Generation-2 Night Vision
GEN-2 Major improvements in image-intensifier tubes resulted in Generation-2 NVDs. They offer improved resolution and performance over Generation-1 devices, and are considerably more reliable.
The biggest gain in Generation 2 is the ability to see in extremely low light conditions, such as a moonless night. This increased sensitivity is due to the addition of a ‘microchannel’ plate to the image-intensifier tube. Since this plate actually increases the number of electrons instead of just accelerating the original ones, the images are significantly less distorted and brighter than earlier-generation NVDs.
Generation-3 Night Vision
GEN-3 Currently used by the U.S. military. While there are no substantial changes in the underlying technology from Generation 2, these NVDs have even better resolution and sensitivity.
The photo cathode is made using gallium arsenide, which is very efficient at converting photons to electrons, providing better resolution and sensitivity. Additionally, the micro-channel plate is coated with an ion barrier, which dramatically increases the life of the tube.
Generation-4 Night Vision
GEN-4 The military dropped the term, GEN 4, and instead refers to the technology as GEN 3 with “filmless” and “gated” tubes. The technology shows significant overall improvement in both low- and high-level light environments.
The ion barrier that was added to the micro-channel plate in the previous generation was removed to reduce the background noise and enhance the signal to noise ratio. Removing the ion film actually allows more electrons to reach the amplification stage so that the images are significantly less distorted and brighter.
The addition of an automatic gated power supply system allows the photocathode voltage to switch on and off rapidly, thereby enabling the NVD to respond to a fluctuation in lighting conditions in an instant. This capability is a critical advance in NVD systems, in that it allows the NVD user to quickly move from high-light to low-light (or from low-light to high-light) environments without any halting effects. For example, when someone turns on a light nearby, the new, gated power feature, the change in lighting wouldn’t have a negative impact; the improved NVD would respond immediately to the lighting change.
Many of the so-called “bargain” night-vision scopes use Generation-0 or Generation-1 technology, and may be disappointing if you expect the sensitivity of the devices used by professionals.
Generation-2, Generation-3 and Generation 4 NVD’s are expensive to purchase, but “you get what you pay for”.
The night vision device is designed in two basic packages; a monocular or a binocular. Naturally, a binocular NVD will cost lots more, but they enable a depth of field which you can’t get from a single monocular.
Some monocular NVD’s are rated to withstand the G-forces of a given rifle and can be attached to some platforms.
Curious to hear from anyone who has their own experiences with a night vision device…