Night vision devices – Clear vision even in the dark
Night vision devices are used to improve or enable visual perception in twilight or darkness. Most devices are residual light amplifiers that intensify the remaining ambient light. Night vision devices are used primarily by the police and the military. Hunters, naturalists and, increasingly, private individuals are also among their users.
How night vision devices work
Image intensifier
An image intensifier uses existing, usually rather weak light to generate a bright image. Sources can include moonlight and starlight as well as lighting from a nearby town. The residual light from the targeted object is directed through a very fast lens into an image intensifier tube and amplified many times over. The targeted object then appears clearly visible in bright green light.
Infrared illumination
However, image intensifiers are ineffective when there is complete darkness. In this case, the additional infrared illumination is used, provided the device is equipped with such a function. Infrared light is not visible to the human eye
Generations of night vision devices
Today’s night vision devices in circulation can be divided into three generations. They differ primarily in the degree of light amplification and in terms of service life. Devices of newer generations are also significantly more expensive than older ones. The very first devices, which were produced from around 1940, are still classified as Generation 0.
First generation:
Light amplification of 1,000 to 8,000 times with a service life of around 2,000 hours. The first devices were introduced around 1950. This is the simplest and at the same time most affordable type of night vision device. An infrared illuminator is usually included and is used in complete darkness. However, it can only be used over relatively short distances.
Second generation:
Light amplification of 15,000 to 60,000 times with a service life between 2,000 and 15,000 hours. Market launch took place in 1960. Due to the higher light amplification, second-generation night vision devices are suitable for significantly greater distances. This is due to a microchannel plate located behind the photocathode and equipped with countless glass tubes. As a result, the image produced is both brighter and sharper. With most devices, a two- to two-and-a-half-fold magnification is possible.
Third generation:
Light amplification of at least 40,000 times with a service life of more than 10,000 hours. First introduced in the US Army in 1982. These devices use photocathodes with additional chemical gallium arsenides, which enable an even brighter and sharper image. Due to patent regulations and an export ban by the US government, third-generation night-vision devices are not available in Germany. However, there are now second-generation devices (“generation two plus” and “two super plus”) which, in terms of image sharpness, brightness and noise, come close to the third generation.
There is now also a fourth generation of night vision devices. However, this is reserved exclusively for military use and is not available on the market. These devices use digital signal processors for image processing and optimization. The image data is generated by special ebCCD sensors (electron bombarded charge-coupled device).
Questions: Night vision devices
Why is night vision green?
The green display is used in image intensifiers. Here, existing but weak light (e.g. from stars) is amplified. During operation, the blue component of the light is shifted into the green spectrum and the red component into the infrared range, which is why the image always appears green. However, there are now also devices on the market that work with an image intensifier tube that produces a black-and-white image, which is even more contrast-rich and makes long-term observation more comfortable.
When was the night vision device invented?
The first image intensifiers were developed around 1940, and the first infrared image converters probably date from 1934.
