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Ultra-long-distance infrared laser night vision system is composed of high-power semiconductor laser LD, driving controller, optical beam expanding and collimating lens, camera and its long focal length lens, transmission system and monitor, etc. High-power semiconductor laser LD, driven and controlled by high current, emits invisible infrared rays to illuminate the photographed target object. However, because the laser beam is thin and has high brightness, it is necessary to expand and illuminate the infrared beam to the target scene in the monitored range through the optical beam expansion collimating lens according to the distance and range of the monitored long-distance target. After being reflected by the infrared object, it enters the long focal length lens of the camera and is imaged on the photosensitive surface.
Because the infrared light wave transmission technology is transmitted in the air medium, its transmission quality is greatly affected by the weather. Generally, sunny days have the least impact on transmission quality, while rain, snow and foggy days
have greater impact on transmission quality. At present, to solve this problem, higher power LD tubes, more advanced optical devices and multiple beams are generally used. In fact, the ultra-long distance infrared laser night vision system is mainly affected by the absorption and scattering of particles and fog in the air, and the synchronous pulse distance gating technology can solve this problem well. Distance gating technology, first, there must be pulse laser beam irradiation technology, that is, the emitted laser is controllable pulse type; Second, there should be an enhanced CCD that can be turned on and off at a high speed, and its switching speed can reach several hundred ns, and it should keep strict synchronization with the laser beam pulse. In this way, the observer can select a specific observation distance, thus easily eliminating the interference of strong scattered light and reflected light generated by water droplets, fog, snow, dust and the like in other distances.
The visible light wavelength that human eyes can see is 0.78μm and 0.38μm from long to short, and its color arrangement is red, orange, yellow, green, cyan, blue and purple in turn. Light with shorter wavelength than purple light is called ultraviolet
light, and light with longer wavelength than red light is called infrared light. Using the infrared light source, it can emit infrared rays invisible to the naked eye to illuminate the photographed object. After the infrared rays are reflected by the object, they enter the lens and image on the CCD. At this time, images invisible to the naked eye can be photographed in dark environment. At present, the infrared light sources widely used in the market include LED infrared lamps, micro-array LED infrared lamps, halogen filter infrared lamps, etc. However, these infrared lamps have some limitations in irradiation distance, power consumption, efficiency and so on, and are not suitable for night vision monitoring over 1km. Therefore, this system must be illuminated by near-infrared high-power semiconductor laser light source. We choose domestic semiconductor laser diode LD, whose wavelength is 808nm, and its power is 1W-10W according to the required distance.
Ultra-long-distance infrared laser night vision system can be widely used in places that need long-distance night vision monitoring, such as border defense night vision monitoring, coastal defense night vision monitoring, maritime long-distance monitoring, flood control long-distance monitoring, forest fire prevention lookout monitoring, urban environmental detection long-distance monitoring, oil field night monitoring, seawall long-distance monitoring, public security night monitoring, prison wall night monitoring, railway and train airport all-weather monitoring, etc. The monitoring of military facilities, military offices, military stations and other occasions often only monitors a specific area, so it is generally adopted to install fixed-focus night vision devices at specific locations, and according to the number of monitored objects, multiple night vision devices can be installed or zoom night vision devices can be used. In addition, the ultra-long distance infrared laser night vision system can be used as a vehicle-mounted night vision system, which consists of three parts: front-end image signal acquisition, intermediate transmission of video signals and control signals, and image control center.
