The development process of night vision device
The earliest generation - the earliest night vision systems were developed by the US military, and they were used on the battlefields of World War II and the Korean War. These NVD systems used active infrared technology. This means that an emitting unit called an infrared radiation source must be attached to the NVD. The unit emits a beam of near-infrared light, similar to the beam emitted by a normal flashlight. Such beams cannot be seen by the naked eye, they bounce off the object and return to the NVD's lens. This system connects the anode to the cathode to accelerate electrons. The problem with this approach is that the acceleration of the electrons distorts the image, and it also greatly reduces the lifetime of the pipeline. When this technology was first used in the military, there was another major problem: the enemy could copy the system in a short time, which allowed enemy soldiers to use their NVD system to see the infrared beam emitted by the device .
First Generation - This generation of NVDs abandoned active infrared technology in favor of passive infrared technology. This kind of NVD can use the ambient light emitted by the moon and stars to amplify the reflected infrared rays around it, so it was once called starlight by the US military. This means they do not require an infrared emitting source. It also means they don't work as well on cloudy or moonless nights. The first generation of NVD uses the same image intensifier tube technology as the 0th generation, and also relies on the cathode and anode for electron acceleration, so there are still problems of image distortion and short tube life.
Second Generation - A major advance in image intensifier tube technology led to the second generation of NVDs. They have higher resolutions than first-generation devices, better performance, and better reliability. The biggest takeaway from second-generation technologies is their ability to generate images in extremely low-light conditions, such as on a moonless night. Sensitivity is increased because of the image intensifier tube attached to the microchannel plate. Because MCPs increase the number of electrons rather than just accelerating them, image distortion is significantly reduced and brightness is higher than previous generations of NVDs.
Third Generation - The U.S. military currently employs third-generation technology. Although its principle is not substantially different from the second generation, the resolution and sensitivity of this generation of NVD are better. That's because its photocathode is made of gallium arsenide, a substance that helps improve the efficiency with which photons are converted into electrons. In addition, MCP is also covered with an ion barrier layer, which can effectively increase the life of the pipeline.
The fourth generation - the fourth generation technology we usually refer to is also called "no film threshold" technology. Generally speaking, the performance of this generation system has been greatly improved in both strong light and low light environments.
