Study On Aero-optical Aberrations Measurement And Distorted Images Correction In Imaging Guidance

When vehicle searching target with imaging guidance in supersonic or hypersonic,the aero-optical effect resulting from the reaction between vehicle and freestream is the main factor that restrict the accuracy.Precisely,it is the influence to light transferring that makes the target images distorted,so that affects the guidance accuracy.so it is important to study the influence of aero-optical effect to light transferring,in another word,to study the light wavefront distortion.And also,it is a key step to correct the distortion target image with distortion light wavefront.In current work,the distorted wavefront measuring technique was studied in experiment method.A new wavefront sensing technique was finished in this work,valid testing was studied with a optical lens.To correct the distortion target imaging,a new theory was proposed innovatively in this thesis,and also a kind of new method that calculating geometry OTF(Optical Transfer Function)was studied,and then distortion target image was corrected with numerical image correction method.Firstly,the study object of aero-optical effect,method in distortion wavefront testing and image correction were introduced in detail.The research status of them also was studied in this chapter.Secondly,considering the requirement of aero-optics wavefront testing,some indispensable equipment were introduced.A supersonic(hypersonic)tunnel that could produce free stream of a low noisy and turbulivity was introduced,and the flow parameters were introduced precisely.To study the influence of different dimension structure to light transferring,a technique called NPLS(Nanoparticle-based Planar Laser Scattering,NPLS)that can measure fine structure of a section in supersonic 3D flow field was introduced in this thesis,which also have high spatiotemporal resolution.And the NPLS system can be used to test wavefront,and it can be compared with another new wavefront testing technique.Another new wavefront testing technique-BOS-WS(BOS-based Wavefront Sensor)was studied in the work,spatiotemporal resolution and sensitivity of two kinds model of BOS-WS was studied in experiments,and found that schlieren model have a higher precision,appropriate layout parameter should be chosen when use BOS-WS to test wavefront in aero-optics.Finally,two kinds of methods to correct distorted image was studied in the thesis.(1)image filtering method based on optic transfer function(OTF).In the work,a image filtering theory that based on OTF was introduced precisely,and then proposed a kind of new method that calculate geometry OTF quickly,and also calculate the wave OTF with OPD tested by BOS-WS.(2)numerical image correction method was also studied,and found that it works in correcting the deviation of object in the images.