In the active infrared night vision device, the infrared searchlight is usually installed near the receiver. When illuminating the long-distance target, the searchlight axis is very close to the optical axis of the instrument. When the light beam irradiating the target passes through the atmosphere, it is scattered by the atmosphere, and part of the scattered radiation enters the observation system back, which is backscattering. Backscattering creates an additional background on the instrument image plane that reduces image contrast and clarity. In poor visibility conditions, this effect becomes a fundamental limiting factor for the imaging performance of active infrared night vision devices.

 

In terms of alleviating the influence of backscattering, the use of narrow beam searchlights and making the optical axis of the observation system as far as possible away from the optical axis of the searchlight will have a certain effect, but their implementation often affects the practicability of the system.