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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。
Due to the discrete exit pupil wavefront of the sub-aperture synthetic optical imaging system, the imaging features are different from the conventional optical system. Comparing the image quality evaluation methods of two kinds of sub-aperture synthetic optical imaging systems, one is to directly use the integral exit pupil wavefront parameters measured by the interferometer to fit the Zernike polynomials, and obtain the modulation transmission of the optical system through fast Fourier transform Function; and the other is to directly calculate the system modulation transfer function of the diffracted direct integral of the exit-pupil wavefront complex image amplitude distribution in the image plane. For the discrete exit pupil wavefront, fitting the Zernike polynomial inevitably have a greater error, the resulting modulation transfer function and the actual measured values are quite different. A three-mirror imaging optical system was designed and fabricated. On the basis of this, the ZYGO GPI interferometer was used to verify and compare the characteristics of image quality calculated by the two methods. The results show that the sub-exit pupil wave direct diffraction integral superposition method is more accurate, but the calculation is large, and to obtain higher image quality evaluation accuracy, we should use more suitable for the expression of discrete irregular shape sub-pupil wavefront function.