Infrared light is a kind of light with invisible wavelength. Generally, there are the following three methods to generate this invisible light.

　　①, directly use incandescent lamp to emit infrared light. Then install a visible light filter on the lamp to filter out the visible light so that only the invisible infrared rays are emitted

　　②. Use infrared light-emitting diodes or diode arrays to generate infrared light. This device generates infrared light through the recombination of electrons and holes in a gallium arsenide semiconductor

　　③, infrared laser diode (LD) can also be used as infrared light source. However, it needs to excite or pump electrons in a lower energy state to a higher energy state, and maintain the stimulated radiation infrared light by reversing the distribution of a large number of particles and resonating.

　　 The first light source is thermal infrared light source. Its biggest advantage is that it can be made into a relatively large power and a larger irradiation angle, so the irradiation distance is long. Its biggest disadvantage is that it contains visible light components, that is, there is a red storm, and its service life is short. If you work 10 hours a day, 5,000 hours can only be used for more than a year. If you consider insufficient heat dissipation, the life span is even shorter. In order to improve the life of the infrared lamp, it is necessary to adopt a light-controlled switch circuit when using it to reduce its working time. In addition, a delay switch circuit is added to prevent interference from ambient light.

　　 The second type is an infrared lamp composed of a semiconductor gallium arsenide light-emitting diode array, especially an array-type integrated light-emitting chip infrared pair tube developed and produced using new technology. The light output of LED-Array reaches 800mw-1000mw, becoming a substitute for ordinary diodes. The half-power angle of the infrared pair tube is 10-120° (variable angle).

　　 Because the infrared pair tube is a highly integrated diode, the volume is only a penny, and it can evenly illuminate the entire indoor space, with a lifespan of up to 50,000 hours. It was originally used in aviation aircraft. In recent years, due to the development of the civil night monitoring market, LED has gradually moved to the mass market and has become the most extensive ideal choice for night monitoring.

　　 Infrared diodes and infrared pairs of tubes eliminate thermal infrared light sources, but for the monitoring of ultra-long-distance scenes above 1km, infrared LD light sources must be selected. Because the semiconductor laser has the characteristics of higher brightness and strong directionality than the LED.