Algorithms And Implementation Of Opptical Transmission In Aerodynamic Thermal Environment

When a high-speed aircraft with infrared imaging detection system is flying at high speed in the atmosphere,the flow field around the high-speed aircraft is extremely squeezed because of its fast flying speed.In this extreme environment,shock waves and other complex flow field changes occur near the head of the high-speed aircraft,which causes optical fluctuation of refractive index.At the same time,due to the intense interaction between the head cover and the air,the temperature and pressure in the head area of the high-speed aircraft change dramatically,which makes the optical head cover of the high-speed aircraft produce obvious refractive index changes and changes.When the high-speed vehicle imagines the target,the target beam deflects and diffuses due to the flow field area of the sharp change of the refractive index.The optical head cover of the high-speed vehicle's head,due to the remarkable refractive index and deformation,further makes the wavefront into the optical system produce greater distortion and reduces the imaging and recognition of the target by the imaging system.By studying the flow field at hypersonic speed and the phase modulation law of the high-speed aircraft hood to the incident wavefront,the wavefront coding of the imaging detection system can be designed,and the detection accuracy of the imaging system can be improved.In this paper,the distribution of refractive index,refractive index gradient and deformation of the hood of hypersonic high-speed vehicle in thermal environment are studied,and the aero-optical transmission model suitable for most optical windows is established.The main research contents include:(1)Research on the calculation model of optical transmission.By analyzing the limitations of optical transmission algorithm based on reconstructed slice grid,a data fusion model of external flow field and hood is established.Based on the assumption of local uniformity of refractive index gradient of external flow field and hood in aerothermal environment,a linear interpolation algorithm of refractive index gradient is proposed,and an aero-optical transmission model suitable for various types of optical windows is established.(2)Study on the external flow field and refractive index gradient and deformation distribution of optical hood of high-speed aircraft in aerothermal environment.According to Gladstone-Dale formula,the refractive index field of the flow field around the optical head cover is calculated.The refractive index distribution of the head cover is calculated according to the thermo-optic effect.The refractive index gradient,refractive index gradient change index of the head cover and the external flow field are analyzed.The uniformity of the refractive index gradient in the local area is proved,and the deformation distribution of the head cover is analyzed.(3)Verification of optical transmission model and study of optical transmission characteristics of rotary symmetric head cover.The correctness of the optical transmission model is verified by the uniform refractive index plate and the optical wedge,and the calculation error is analyzed.Then,the optical transmission simulation of five kinds of face masks with aspect ratio of 2 is carried out based on the model,and the influence of the model on the imaging quality is analyzed.