Why Infrared Night Vision Images are Green, Not Red (Infrared Spectrum)?

Objects above absolute zero radiate energy. The lower the temperature, the longer the wavelength. At room temperature, this radiation is typically infrared. When the temperature reaches around 800 degrees Celsius, the radiation becomes visible light, which is why iron glows red when heated. We cannot see infrared light, but it is still radiated at night. People and the surrounding trees have different temperatures, and therefore radiate infrared light with different wavelengths.

The principle of an infrared night vision device is to convert the infrared light that we cannot see with our naked eyes into visible light. Because the radiated infrared light is very weak, the converted visible light is also very weak. The image appears green because our eyes are most sensitive to green light, and green light is less tiring to the eyes, which helps us see the weak light more clearly. Moreover, the difference between red light and green light is only the wavelength, which is easy to convert. The process is as follows: dim image at night → photocathode (converts photons into electrons) → microchannel plate (increases the number of electrons through high voltage) → fluorescent screen (electrons hit a screen with a phosphor coating). Therefore, the scenes seen by infrared night vision devices are mostly green.