子孔径合成光学成像系统像质评价研究

由于子孔径合成光学成像系统出瞳波前离散,成像特征有异于常规光学系统.对比了两种子孔径合成光学成像系统的像质评价方法,其一是直接利用干涉仪实测获得的整体出瞳波面参量,拟合成泽尼克多项式,通过快速傅里叶变换获得光学系统的调制传递函数;其二是对子出瞳波面在像面复振幅分布的衍射直接积分叠加计算系统调制传递函数.对于离散出瞳波前,拟合的泽尼克多项式不可避免有较大误差,由此计算获得的调制传递函数与实际测量值有较大区别.设计并制造了一个三子镜合成的成像光学系统,在此基础上用ZYGO GPI干涉仪验证并对比了使用两种方法对像质计算的特点.结果表明,子出瞳波面直接衍射积分叠加法的精度更高,但计算量大,且要获得更高的像质评价精度,应使用更适于表达离散不规则形状子出瞳波前的波函数.

Image Quality Evaluation for Segmented Mirror Synthetic Aperture Optics

Exit pupil wavefront of the segmented mirror synthetic aperture optics (SAO) is discrete, which is much different from traditional systems. Two methods are used to evaluate SAO systems imaging. One is to get the exit pupil wavefront by interferometer and fit it into Zernike polynomial directly, then use the way of fast Fourier translation (FFT) to get system′s modulation transfer function (MTF); the other is to integral the sub-exit-pupil′s wavefront respectively, and calculate the complex amplitude distribution of each sub-mirror′s, and overlap them in image plane, then get the MTF. As the fitted Zernike polynomial of exit pupil wavefront cannot express the discrete wavefront accurately, the former way is much different from the reality system. A segmented mirror system with three sub-mirrors primary is built, and the wavefront is obtained by ZYGO GPI interferometer, include overall exit pupil wavefront and each sub-exit-pupil wavefront. The two methods are compared, and the result shows the latter way is more precise but complex, and need much more computation; especially, the other more precise polynomial should be used to express the exit-puil wavefront of abnormity figuration sub-mirror, can we get the more rensonable resnlt.