Generation 0
The original night binoculars system created by the United States Army and used in World War II and the Korean War, these NVDs use active infrared. This means that a projection unit, called an IR Illuminator, is attached to the night binoculars. The unit projects a beam of near-infrared light, similar to the beam of a normal flashlight. Invisible to the naked eye, this beam reflects off objects and bounces back to the lens of the night binoculars. These systems use an anode in conjunction with the cathode to accelerate the electrons. 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 projected by the device.
Generation 1
Next we move away from active infrared, using passive infrared instead. Once dubbed Starlight by the U.S. Army, these night binoculars use ambient light provided by the moon and stars to allow 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. These night binoculars 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
Generation 2 night binoculars is a big step up due to major improvements. 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 the micro channel plate to the image-intensifier tube. Since the MCP 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
This generation is currently used by the U.S. military. While there are no substantial changes in technology from Generation 2, these night binoculars have even better resolution and sensitivity. This is because the photo cathode is made using gallium arsenide, which is very efficient at converting photons to electrons. Additionally, the MCP is coated with an ion barrier, which dramatically increases the life of the tube.
Generation 4
Generation 4 technology shows significant overall improvement in both low and high level light environments.
The removal of the ion barrier from the MCP that was added in Generation 3 technology reduces the background noise and thereby enhances 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 night binoculars to respond to a fluctuation in lighting conditions in an instant. This capability is a critical advance in NVD systems where it allows the NVD user to quickly move from high light to low light environments without any halting effects. With the new, gated power feature, the change in lighting wouldnt have the same impact; the improved NVD would respond immediately to the lighting change.
Generation 0 or Generation 1 technology is your lower end units and may be disappointing if you expect the sensitivity of the devices used by professionals. Generation 2, Generation 3 and Generation 4 night binoculars are typically expensive to purchase, but they will last if properly cared for. Also, any NVD can benefit from the use of an IR Illuminator in very dark areas where there is almost no ambient light to collect.
