Research On Dynamic Aberration Correction Method Of Airborne Conformal Optical System Based On Lens Array

The outer surface of the conformal optical window is consistent with the contour of the aircraft,which can significantly reduce the flight resistance,the reflection cross section of the airborne radar,and enhance the stealth effect of the aircraft.However,the shape of the conformal optical window and the installation method will result in a large dynamic aberration that varies with the look angle after the imaging beam passing through the conformal optical window,which seriously reducing the imaging quality of the system.At present,there are tow main methods that can correct the dynamic aberration of the conformal optical window including the dynamic correction method and the static correction method.The dynamic correction method can realize the correction of dynamic aberrations in a large scanning field of view,but this method requires complicated support of the system structure,which is not conducive to the stability of the overall structure.In contrast,the static correction method can ensure the stability of the optoelectronic system,but can only correct the dynamic aberrations of the small scanning field of view.As a result,the static correction is not suitable for the airborne conformal optical system with large scanning field of view.In this study,by analyzing the aberration characteristics of the conformal optical window,a static correction method based on the lens array is proposed to realize the aberration correction of the conformal optical window with a large scanning field of view.The main contents of this research are as follows:(1)Firstly,the initial structure of the conformal optical system is established,then the on-axis aberration composition of each look angle of the system is studied,and the astigmatism is obtained as the main aberration of the system.Based on this conclusion,the characteristic of the astigmatism of the system in the full field of view could be further analyzed,the analysis result is that the size and direction of the astigmatism change dynamically with the look angle.(2)With regard to the characteristics of the dynamic aberration of the conformal optical window,a method of correcting aberrations by channels is proposed.The scanning and imaging process of the conformal optical system is regarded as separate imaging for each look angle,and the dynamic aberration correction of the conformal window is transformed into the static aberration correction of each channel.An airborne conformal optical aberration correction system based on a fixed correction plate and a lens array corrector is designed.The fixed correction plate is placed in front of the imaging lens,and it is scans with the imaging lens to balance the dynamic aberrations of the conformal optical window at various look angles.The lens array corrector is implanted in front of the image plane,and each lens unit is corresponded to a scanning imaging channel.The parameters of each lens unit are independently optimized,so that the aberrations of each imaging channel are corrected respectively.The design results show that this static correction method can reduce the dynamic aberration of the conformal optical window to within ± 1? within the range of ± 42°scanning field of view.(3)In order to simplify the structure of the optical system,a static correction method of using the inner surface of the conformal optical window and the lens array corrector is proposed.By analyzing the aberration characteristics of the inner and outer surfaces of the conformal optical window,a conformal optical system is designed.By optimizing the inner surface of the conformal optical window and the lens array corrector,the dynamic aberration of the conformal optical window is corrected to within ± 1? within the scanning field of view range of ± 42°.The design results show that this method does not add any movable components,and can effectively reduce the dynamic aberration of the conformal optical system with a large scanning field of view.