基于Zernike模型系数优化的椭球型窗口光学系统像差校正

Aberration correction for ellipsoidal window optical system based on Zernike mode coefficient optimization

传统的半球形窗口难以满足高速飞行器气动力学的需求,采用流线型外表面的非球面光学窗口技术应运而生.这种窗口会随着扫描视场角的变化产生大量动态像差,校正这类像差成为高速飞行器光电成像系统发展的关键问题.对于扫描视场为±60°的椭球形窗口光学系统,研究了静态校正和无波前探测器的自适应光学技术相结合的大扫描视场像差校正方法.设计时,首先以减少系统像差种类为导向,进行初始结构设计,消除五阶Zernike像差,从而减少后续自适应优化控制变量数.利用Zernike多项式系数与变形镜驱动器电压之间的转换矩阵,将优化变量由140个驱动器电压减少至Zernike多项式2—9项系数.最后利用基于Zernike模型的遗传算法对变形镜面形进行控制,校正残余像差.仿真结果表明,各典型扫描视场点的优化速度提升95%以上,且光学像质接近衍射极限.该优化方法不仅可以修正异形光学窗口引起的像差,同时还能够校正光学系统装调、加工时引起的误差,具有较强的实用性.

The traditional window of high-speed aircraft is hemispherical,and the aberration produced by such a window is constant.However,the hemispherical window is difficult to meet the requirements of a high speed flight of aircraft.Aspheric windows are usually used to replace hemispherical windows to increase the aerodynamic performance.However,the aspheric window will introduce dynamic aberrations that fluctuate with the change of scanning field-of-view(FOV),which becomes the key issue of the development of optoelectronic imaging systems for high-speed aircraft.For the ellipsoidal window optical system with scanning FOV of±60°,an aberration correction method in large FOV combined with the static correction and non-wavefront-sensor adaptive optical correction is studied.In the initial optical structure design,the types of system aberration are reduced and the fifth-order Zernike aberration is eliminated during initial aberration correction,thus,the number of the subsequent adaptive optimization control variables is reduced.According to the characteristics of the deformable mirror,the driving voltage of the driver is generally taken as a variable of the genetic algorithm.However,when the deformable mirror used has many units,too many variables will directly lead the optimization speed of the algorithm to greatly decrease.So,according to the aberration characteristics of the ellipsoidal optical window,using the conversion matrix between the Zernike polynomial coefficients and the voltages of the deformable mirror driver,the optimization variable is reduced from 140 driver voltages to 2−9 Zernike stripe polynomial coefficients in number.Finally,the genetic algorithm based on Zernike model is used to control the shape of the deformable mirror and correct the residual aberration.Taking 2−9 Zernike mode coefficients,2−16 Zernike mode coefficients and 140 driver voltages as the variables of genetic algorithm respectively,the optimization generations of genetic algorithm under different variables are obtained.The simulation results show that the optimization speed of each typical scanning field of view is increased more than 95%by changing the variable from 140 driver voltages to 2−9 Zernike mode coefficients,and the imaging quality is close to the diffraction limit.This optimization method can not only correct the aberrations caused by the special-shaped optical window,but also compensate for the error caused by processing and aligning the optical system.