Anyone who watches CNN has probably seen video footage from the military's use of Night Vision technology. Night vision used by the military in recent years processes very low light levels, especially in the near-infrared (IR) or ultraviolet light bands, to produce an image.
Night vision devices were introduced during the Second World War, initially for use by the pilots of airplanes. The technology has significantly advanced in the ability to amplify light. Initial devices could amplify light by 1000 times, but current technology can amplify light by more than 50,000 times.
One important difference between military and most civilian night vision systems is the concept of passive versus active. Military night-vision systems use passive techniques. Active night-vision systems project IR light that is not visible to the naked eye, but if one were wearing night vision goggles, it would be like looking at a beacon. This would be counter-productive for military applications. On the battlefield, a soldier utilizing an active IR source is called a target.
Security cameras, and most other non-military night vision systems, utilize an IR Illuminator that projects a beam of near-infrared light. This beam reflects off objects back to the lens of the night vision sensor. The most common IR Illuminators used in security cameras today are banks of IR LEDs. With an active IR system, the range will be proportionate to the magnitude of the emitted IR light. Because active infrared night vision systems produce high levels of infrared light, the resulting images are typically higher resolution than passive vision technologies.