Research On The Aero-thermal Effects By3-D Analysis Model Of The Optical Window Of The Infrared Imaging Guidance

Researches on hypersonic vehicles have been a hotspot in the field of aerospacebecause of the pursuits for higher speed by human being. Infrared imaging guidance isplaying a very important role in modern warfare. When an IR imaging guided missile isflying in the air at high speed, its optical dome suffers from serious aero-optic effectsbecause of air flow. The turbulence around the dome and the thermal effects of the opticalwindow would cause disturbance to the wavefront from the target. Therefore, detectedimages will be biased, dithered and blurred, and the capabilities of the seeker for detecting,tracking and recognizing are weakened.Given all that, the aero-optic effects must be controlled and corrected. The correctionmay include turbulent flow control, image restoration, dome design, refrigeration andphotoelectric correction methods according to the causes of aero-optic effects. In this paper,a kind of the photoelectric correction method---adaptive optics (AO) utilizing real-timewavefront correction is analyzed. Studies have been taken on the influence of laminar andturbulent flow outside the IR window on ray propagation. By comparing with differenttypes of adaptive optics systems, the image sharpening AO system is determined for thefinal correction scheme.Also In this paper, methods for calculating the aero-dynamical force and heat flux aswell as methods for thermal and structural analysis with Heat Transfer and ElasticMechanics are introduced. By studying the aero-thermal effects and aero-thermal radiationeffects of the optical window, the3-D analysis model of the optical window is establishedby using finite element method. The direct coupling analysis is employed as a solvingstrategy. The variation regularity of the temperature field is obtained. For light withdifferent incident angles, the influence on the ray propagation caused by windowdeformation is analyzed with theoretical calculation and optical/thermal/structuralintegrated analysis method respectively.Last but not the least, computer simulation of an image sharpening AO system basedon SPGD is studied.The SPGD algorithm is realized in MATLAB, and an AO system is modeled in optical design code ZEMAX. Communication between MATLAB and ZEMAXis established via DDE technique. MATLAB computes the control voltage and sends it toZEMAX; ZEMAX alters the shape of the deformable mirror (DM) according to thereceived voltage, and calculates the point spread function (PSF) data, which is then sentback to MATLAB. This iteration goes on and on, until the termination condition is satisfied.