There are three types of night vision devices: active infrared night vision devices, low-light night vision devices, and thermal imaging night vision devices. night vision ，The first and third types of night vision devices mainly use the principle of infrared light, while the second type mainly uses the principle of low light.

How does night vision allow people to spot enemies hidden in the dark? Active infrared night vision device adopts active attack strategy. It uses an infrared searchlight to emit infrared light, and when it hits a distant target, it is immediately reflected back.

According to the power of the infrared searchlight, the observation range is also different. This kind of night vision device has low cost and mature technology, so it was very popular in the early days. But it has an Achilles heel. It has to actively emit infrared rays, so it is easy to be discovered by the enemy's infrared detectors and expose itself. With the development of human night vision technology, this night vision device has been gradually replaced.

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