Night vision is becoming more and more common for a variety of applications. The drastic improvements in night vision technology over the past decade has made the products available today some of the most important equipment available to military and law enforcement…but how does it work? Night Vision Devices consist of several main parts: an objective lens, an eyepiece, a power supply and an image intensifier tube (Photocathode Tube). Night vision devices gather existing ambient light (starlight, moonlight or infra-red light) through the front lens. This light, which is made up of photons goes into a photocathode tube that changes the photons to electrons.