Research On Mid-Wave Infrared Forest Fire Monitoring And Pre-Warning System Using Point Sensors

Forest fire is a forestry disaster worldwide which will cause losses to forest natural resources and bring great damage to ecosystem once happened.Therefore,building an effective and reliable forest fire monitoring system to detect and warn forest fire is an important work of forest fire prevention.With the widely use of infrared imaging technology in forest fire prevention,the forest fire surveillance systems are developing towards the direction of intelligence and informationization,combined with video observation,fire spot identification and localization.It is of great theoretical value and practical significance to study low-cost and high sensitivity infrared forest fire monitoring and pre-warning system and related principles and key technologies.One of the main forest fire identification methods at present is to detect and warn the incipient fire spot with high temperature,whose radiation characteristic is the basis of infrared detection.Research on the radiation features of fire targets is beneficial for improving the recognition rate of infrared system.For the mission of detecting infrared signals of long-distance forest fire target under actual environmental conditions,the infrared system needs to be of good performance.Thus,the simulation analysis and discussion about the effect of radiation properties,optical system,detector and other factors on the performance of infrared system can provide technical foundation and analyzing method for the design optimization and testing of infrared system.On the contrary,based on the gas infrared imaging technology,detecting the high concentration of carbon dioxide plume generated at the early stage of forest fire can be used as a supplementary means to identify and judge the fire situation earlier.In this paper,based on the summary and evaluation of the current status of domestic and international research and development of infrared forest fire monitoring and gas infrared imaging technology,we have conducted an in-depth study of its theory and key technologies.The main contents of this thesis are as follows:1.Investigate the fire spot radiation intensity equation in details,perform numerical calculations and analyze the factors that affects from the perspective of target radiation properties.Focusing on the performance parameter of infrared imaging system,derived from the definition of the system noise equivalent temperature difference(NETD),the effects of bandwidth,forest fire radiation features and detector integration time on NETD is simulated and analyzed.The equation of the infrared imaging system detection distance estimation for point origin target is given,based on which the fire detection capability of a given system under different NETD and atmospheric conditions is simulated.2.The radiative transfer model theory of infrared imaging technology for gas leakage is studied,and simulate the effects of gas concentration,target gas temperature and background temperature on gas imaging detection.For the problem of requiring temperature difference between gas and background in the traditional method,a gas detection method is proposed by calculating the radiation energy difference of the dualbackground spots with difference temperature on the gas path.The calculation process of gas concentration estimation is given.The trend of radiation energy change in the reference band is used to distinguish the temperature change of background points and correct the response value.In addition,an infrared imaging gas detection system is built with a mid-wave infrared focal plane detector to realize the detection and concentration estimation of carbon dioxide,and the feasibility of the method is verified.3.The forest fire monitoring and pre-warning system adopts the design form of object-scanning and coaxial-two-mirror reflective optical system.The design of dualband infrared optical system based on the point source detector is accomplished,the overall size of the optical system is optimized.The key technologies involved,such as the scanning scheme,were analyzed.By conducting forest fire monitoring experiments on indoor and outdoor infrared radiation target,the system completed the forest fire spot detection function at a maximum distance of 5km with a low leakage rate.