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How Does Night Vision Work?
How Night Vision Works - Night Vision Technology
These optics basically consist of two different technologies.Thermal technology which detects heat differences and image intensification (traditional green night vision) which amplifies available light. For most applications image intensification is the best choice as it gives clearer more detailed images, is more widely available and user friendly, and is much less expensive when comparing the same quality image intensification device to the same quality thermal device. Please see our Thermal vs Night Vision for a more through comparison of these two technologies.
Here we will explain how night vision works. The traditional green, light amplification night vision technology works by gathering the small amount of available light, (starlight, moonlight, or infrared light) through the night vision objective lens. This light then enters a gallium arsenide photocathode tube that takes the light energy called photons and converts it into electrical energy called electrons. To create the amplification these few electrons pass through a special disk shaped device about the size of a quarter called a microchannel plate. This microchannel plate has millions of tiny channels inside that that via an electrical and chemical process cause the few electrons that enter it to strike the walls of the tiny channels and release thousands more electrons. These thousands of new electrons exit the microchannel plate and travel through a phosphor screen which converts the electrons back into photons which is visible light. This visible light is the end product that travels through the eyepiece to your eye and is viewed in a bright greenish hued amplification of the original scene you were viewing.
This process described above is a description of how Generation 3 technology works. It is important to understand that Gen 1 technology does not have the microchannel plate that is responsible for a very large portion of the light amplification. Gen 2 units do have microchannel plates so they create a great boost of light amplification however they do not have the same protective films or ion barrier on the microchannel plates that is standard on Gen 3 equipment. The absence of this ion barrier shortens the life span of the Gen 2 image tube. Gen 2 also uses an older cheaper tri-alkali photocathode rather than the newer more effective gallium arsenide photocathode used in Gen 3 which improves low light performance and increases detection distances.