Research On Measurement Technology Of Atmospheric Isoplanatic Angle Based On Triple Loop Apodization Mirror

The existence of turbulence affects the transmission of high-energy laser,leading to the attenuation of the power density of the target surface at the receiving end,the reduction of the power price of laser weapon,and the failure to achieve the expected target striking effect.It reduces the detection accuracy of laser radar and other equipment,interferes with the guidance weapon to obtain true and accurate data,and leads to the decrease of its strike accuracy.In addition,in optical communication,the bit error rate will increase,the signal-to-noise ratio will decrease,and the communication performance will decrease.Turbulence also disrupts the coherence of the beam,resulting in a decrease in the resolution of the imaging system,which affects optical engineering applications such as astronomical siting and adaptive optical correction.In order to meet the requirements of atmospheric environment information,turbulence changes need to be detected based on the measurement requirements of atmospheric environment characteristic parameters.Atmospheric isoplanatic angle is one of the basic parameters describing atmospheric optical turbulence.Aiming at the problem of how to obtain accurate and effective turbulence intensity change information from isoplanatic angle data and improve the measurement accuracy of isoplanatic angle,The corresponding isoplanatic angle and its measurement technology are studied.Based on the three-ring apodization mirror,this paper studies the measurement technology of atmospheric isoplanatic angle.The main work is as follows:1.The development status of atmospheric isoplanatic angle measurement at home and abroad is introduced in detail.This paper describes the influence of atmospheric turbulence on the transmission of light waves in the atmosphere.Based on the atmospheric optical turbulence,the formation mechanism of atmospheric turbulence,atmospheric turbulence effect and some common turbulence profile models are described.Two optical turbulence parameters,atmospheric coherence length and atmospheric isoplanatic angle,are introduced.2.Based on the generalized Hufnagel-Valley model,the theoretical relationship between the atmospheric coherence length and the atmospheric isoplanatic angle is derived.A method for inversion of atmospheric refractive index structure constant profile is presented by using atmospheric dry length and atmospheric isoplanatic angle data as inputs.The correctness of the theoretical formula and the feasibility of the method are verified.Based on several Hufnagel-Valley models,the influence of atmospheric turbulence intensity on isoplanatic angle and atmospheric coherence length is simulated and analyzed.The effects of isoplanatic angle and atmospheric coherence length on the atmospheric turbulence changes in the near earth,middle and upper air are investigated.The results show that the isoplanatic angle can reflect the atmospheric turbulence changes in the upper air more effectively than the atmospheric coherence length.3.The isoplanatic angle measurement system based on three-ring apodization mirror is built,and the isoplanatic angle is measured by star scintillation method.The design principle of apodization mirror is introduced,and the three-ring apodization mirror is designed.The advantages of three-ring apodization mirror are verified by simulation.The design process of optical receiving subsystem is described,and the equipment selection and function of imaging,control and data acquisition subsystem are introduced.4.The data of the isoplanatic angle are obtained and the experimental results are analyzed by using the successfully constructed isoplanatic angle measurement system.At the same time,based on the measured isobaric angle and atmospheric coherence length data,the turbulence profile during the measurement period is inversed and the correlation analysis is carried out.Through the study of the atmospheric isoplanatic angle and its measurement technology,we can better explore the variation law of atmospheric turbulence and provide parameter basis for the analysis of atmospheric environmental characteristics.It not only meets the requirements of project construction,but also provides data support for astronomical site selection decision,system design of laser transmission engineering,adaptive optical correction,etc.It has important engineering application value.