Can night vision goggles be used normally during the day?

It is generally said that night vision devices cannot be used during the day, but what I want to say today is that not all night vision devices cannot be used during the day. Whether the night vision device can be used during the day depends on the specific type of night vision device.

1. Why night vision devices cannot be used during the day

Generally speaking, everyone says that night vision devices cannot be used during the day. This statement is somewhat inaccurate. It should be said that low-light night vision devices cannot be used during the day. Low-light night vision devices are image-increasing tube night vision devices. This type of night vision device is afraid of strong light during the day.

Before analyzing the answer to this question in detail, let’s first understand how low-light night vision devices work.

The working principle of the low-light night vision device: When ambient light enters the night vision device through the objective lens of the night vision device, the first thing it encounters is something called a photocathode. Photons shine up, electrons fly out, and light is converted into electricity. Under the influence of the electric field, the electrons continue to move forward. The second layer is called a microchannel plate. There are many small channels evenly distributed on it. Each channel is more than ten micrometers long. The channels are more than ten micrometers apart and the channels are inclined at 8 degrees. This is a magical place. After electrons enter, they will collide with the channel. Each collision will knock out more electrons. New electrons will continue to collide forward. The effect is that one electron goes in and tens of thousands of electrons rush out. , so the signal is greatly enhanced. The electron army continues to rush to the third layer under the action of the electric field, and the third layer is the fluorescent screen. As long as the electrons are hit, they will emit fluorescence, and the electricity will turn back into light, and we can see the enhanced image.

So why are low-light night vision devices afraid of strong light during the day and cannot be used normally during the day?

The low-light night vision device consists of four main components: objective lens, image intensifier, eyepiece, and power supply. The image intensifier tube is the core component of the low-light night vision device. Low-light night vision devices are afraid of strong light because the image intensifier and low-light tube are afraid of strong light. Taking the image intensifier as an example, when infrared light irradiates the photocathode of the image intensifier, 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 image intensifier receives, the more electrons it emits. The light signals emitted by the fluorescent screen are stronger, and the image seen is brighter. They are basically proportional to each other. 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, so nothing can be seen.

At this point, the answer to why low-light night vision devices cannot be used during the day has been very clear. So why do some people say that "night vision devices can be used normally during the day"?

2. Why can night vision devices be used during the day?

In fact, saying that night vision devices can be used during the day is also a misunderstanding of the concept of night vision devices. The night vision devices this statement refers to should be digital night vision devices and thermal imaging night vision devices (also called infrared thermal imaging cameras), and it does not represent all types of night vision devices. The low-light night vision device mentioned above cannot be used during the day. Digital night vision devices and thermal imaging night vision devices rely on image detectors to work and do not rely on image intensifier tubes. These two types of night vision devices can be used 24 hours a day and night. So a more accurate statement is that digital night vision devices and thermal imaging night vision devices can be used during the day.

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