Why are night vision goggles afraid of strong light?
There are various types of night vision devices, but they are basically composed of optical systems, image tubes or micro tubes, power supplies, and power supply systems. Of course, active infrared night vision devices also need to be equipped with infrared searchlights, and the image converter or low light tube is the "heart" of the night vision device. Image tubes can transform invisible infrared images into visible ones, while low light tubes can enhance weak light by tens of thousands or even hundreds of thousands of times, making it visible to the human eye.
Night vision devices are afraid of strong light because the image converter and low light tube are afraid of strong light. Taking the image converter as an example, when infrared light is irradiated on the photocathode of the image converter, the photocathode emits electrons. Under the action of a high voltage field (16-21 kV) and an electron lens, the electrons accelerate towards the fluorescent screen, causing it to display a visible target image. The more light signals the image converter receives, the more electrons it emits, the stronger the light signal emitted by the fluorescent screen, and the brighter the image it sees. They are basically proportional. But if the external light is too strong, the number of electrons emitted by the photocathode does not increase to a certain extent, that is, saturation occurs, and the target cannot be seen clearly. If too strong light suddenly hits, it may also burn out the photocathode of the tube, making it unable to emit electrons, and of course, nothing can be seen.
Although night vision devices have taken certain measures to prevent strong light, their effectiveness is limited, so they must be operated strictly according to regulations when in use. When encountering strong light or daytime target calibration, the objective lens cover should be worn or the power switch should be turned off. Proper use of night vision equipment can prolong its service life and avoid unnecessary damage, thus fully utilizing the function of night vision equipment.
