In the Night-vision Monitoring System, it is visible light the common illuminant for camera. But with the shortcoming of unhide, disturb the resident and easy exposure the monitor target, infrared videography technology, a hidden and scientific method which is a invisible light source to camera, replace to visible light at the present time.
There are Passive Infrared videography technology and active Infrared videography technology. The former use the theory, any substance radiate infrared ray above absolute zero (-273℃) , the higher temperature they has, the more infrared ray they radiate. The application of this theory is the thermal infrared imager. But he cost of this kind of infrared camera is very expensive, they only use for military or some special occasion.
And the active infrared camera technology use infrared light radiating to illuminance (Main infrared ray) and achieve night-vision monitoring. Work with the common low light intensity black and white camera, Day & night camera or infrared low light intensity color camera to sense surrounded scenery and the infrared light reflected back. With mature technology, economy, stable, active infrared camera technology becomes the main stream of night-vision monitoring.