Why is it that night vision devices are afraid of strong light?
There are many types of night vision devices, but they basically consist of an optical system, a variable image tube or a low-light tube, a power supply and a power supply system. Of course, active infrared night vision devices must also be equipped with infrared searchlights, in which the variable image tube or low-light tube is the "heart" of the night vision device. The variable image tube can convert the invisible infrared image into a visible image, while the low-light tube can enhance the weak light tens of thousands or even hundreds of thousands times, making it detectable by the human eye.
Night vision devices are afraid of strong light because the image change tube and low-light tube are afraid of strong light. Taking the variable image tube as an example, when infrared light shines on the photocathode of the variable image tube, the photocathode emits electrons. Under the action of the high-voltage field (16 to 21 kV) and the electron lens, the electrons accelerate toward the fluorescent screen, causing the fluorescent screen to Displays a visible target image. The more light signals the variable tube receives, the more electrons are emitted. The light signals emitted by the fluorescent screen are stronger, and the images seen are brighter. They are basically proportional. However, if the external light is too strong, the number of electrons emitted by the photocathode will stop increasing to a certain extent, that is, it will be saturated, and the target will not be visible clearly. If too strong light suddenly strikes, it may burn out the photocathode of the tube and prevent it from emitting electrons. Of course, nothing can be seen.
Although the night vision device takes certain measures to prevent strong light, its effect is limited, so it must be operated strictly according to the regulations when using it. When encountering strong light or calibrating the target during the day, put on the objective lens cover or turn off the power switch. Proper use of night vision devices can extend their service life and avoid unnecessary damage, thereby giving full play to the role of night vision devices.
