Research On Imaging Effect Of Hypersonic Infrared Seeker

With the continuous improvement of the combat mode and the complexity of the combat environment in modern warfare,there are higher requirements for the flight speed and strike accuracy of the existing high-speed aircraft or traditional air-to-air missiles and air-to-ground missiles.Due to the continuous improvement of the seeker’s flying speed,the aero-optical effect caused by aerodynamic friction is becoming more and more serious.Under the condition of hypersonic speed,the aero-optical effect has even become a key factor restricting the detection performance of the high-speed infrared seeker.The research on aerooptical effects mainly includes wind tunnel experiments and computer simulations.Among them,wind tunnel experiments have disadvantages such as low efficiency and high cost,while computer simulation can establish a reasonable model to study all the aero-optical effects under various attack and defense conditions.characteristics,thereby greatly reducing the cost of research.In this paper,the calculation of the aero-optical effect is completed through computer simulation.The final simulation calculation results can be used to study the imaging characteristics of the infrared guidance system under hypersonic conditions,and provide a good support for the subsequent optimal design of the infrared seeker.The specific research work is as follows:(1)Modeling and simulation of hypersonic outer flow field.In this paper,the external flow field simulation models of the hemispherical fairing and ellipsoidal fairing are established by commercial software,and the aerodynamic flow field data under different flight conditions are calculated.The refractive index data and spectral radiation data of the fluid region and the solid region are accurately calculated through the flow field data,which provides a good data support for the subsequent ray tracing algorithm.(2)Discussion on engineering calculation method of aero-optical effect.Aiming at the shortcomings of low accuracy or poor adaptability of traditional ray tracing algorithms,a ray tracing algorithm based on 3D cellular automata was improved to adapt to any surface fairing,any field of view and line of sight direction.The algorithm starts from the ray equation and calculates the aero-optical transmission effect and the aero-optical radiation effect combined with the refractive index gradient.The basic idea is to discretize the overall research area into a cell space with extremely high precision,formulate the movement rules of photons in the cell space according to the light transmission rules,obtain the overall propagation path of the light,and then combine the radiation calculation theory to calculate each light after research.The radiant energy after the area is superimposed,and finally the exit position of the light on the image surface,the optical path difference and the radiant energy distribution are obtained.The new algorithm has strong flexibility and expansibility while ensuring the calculation accuracy and efficiency,and can meet most of the aero-optical effects of hypersonic external flow field research.(3)Imaging simulation and evaluation of aero-optical effects.Using the image plane data obtained by ray tracing combined with the imaging simulation model,the infrared imaging results of the aero-optical effect under different flight conditions,different cell sizes and different detection bands are simulated,and the simulation results are evaluated with the SSIM image quality assessment method.analyze.The results show that the main factors affecting the aero-optical effect are flight height,flight speed,light incident direction and cell size,etc.The detection band mainly affects the grayscale information of the final image.