There are two different methods used by night vision equipment for visibility in darkness :
1) Thermal Imaging : This method uses the heat emitted by objects to its advantage and shows that to the viewer. The infrared light is detected by infrared-detectors and a detailed temperature pattern is created (Thermogram). The thermogram is converted into electrical signals which are then sent to a signal processing unit. The processed signals are sent to a display where the image is shown.
2) Light Amplification : This is a more commonly used method. In this method, small amounts of light in the surrounding area are converted into electrical energy. Electrons pass through a thin disk, and are multiplied, these electrons bounce off a phosphor screen which converts them back to light. This light is what the viewer sees and enables the viewer to see in the dark.
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