The structure and working principle of active infrared night vision device

In the past, night reconnaissance required the use of artificial light sources (flash lights, flares, lasers, etc.) to illuminate targets and take pictures, or use radar to conduct night reconnaissance. Modern night vision technology can achieve reconnaissance in low-light environments (moonlight, starlight, and atmospheric glow are collectively referred to as night skylight).

Active infrared night vision devices are very similar to active radars. They rely on their own artificial infrared light source to emit light in the near-infrared band to illuminate the target. At the same time, they receive the infrared rays reflected by the target and convert it into a visible image through an infrared image tube. Its composition includes:

Infrared searchlight is an infrared light source or an incandescent light optical system equipped with an infrared filter. It has an objective lens and an eyepiece. The objective lens is placed in front of the variable image tube to collect the received infrared rays and enter the variable image tube. The eyepiece is placed in the variable image tube. Later, the image on the fluorescent screen of the variable tube is enlarged for easy observation.

The infrared image tube is the heart part of the equipment. There are photocathode, electronic lens and fluorescent screen in the vacuum tube. The silver oxide cesium material on the inner surface of the input window of the variable image tube emits electrons outward when illuminated by infrared rays of wavelength, affecting the density of electrons emitted from various parts of the photocathode, thereby forming an electronic image corresponding to the input infrared image; the electron lens is a cylinder The metal cathode operates at a relatively high positive voltage, forcing the electrons emitted by the photocathode to accelerate and gather at the corresponding point on the fluorescent screen, forming a strong visible light electron fluorescence image; the power supply provides the required voltage and current for the instrument.

Active infrared night vision devices have the characteristics of mature technology, low cost, and good observation effects; they have their own light source and are not affected by ambient lighting conditions. They can achieve greater contrast and are easy to distinguish between targets and backgrounds, and tanks coated with green camouflage and green vegetation. The operating distance is related to the emitted infrared power. Generally, the detection distance of a 30-watt infrared searchlight is 200 to 300 meters. However, it is easy to be discovered by enemy infrared detectors. When using it, you must strengthen concealment (such as turning on the phone intermittently, changing positions frequently) to reduce the chance of exposure.

Infrared rays cannot be sensed and distinguished by the human eye, but night vision equipment is used to convert infrared rays into visible light that humans can detect to achieve night vision. Convert infrared rays into electrical signals, and then convert them into light signals visible to the human eye through the luminous body. This is how active infrared night vision devices work.

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