拼接镜面合成孔径光学系统的像质评价

Imaging quality of segmented mirror synthetic aperture optics

拼接镜面合成孔径光学系统的出瞳波前是离散的,需要同时引入波象差和衍射光学理论来拟合最佳高斯参考球面,计算出瞳波前和波象差,并通过对像面的衍射积分,评估系统像质。对比了两种像质评估的方法:其一是直接利用干涉仪实测获得的整体出瞳波面参数拟合Zernike多项式衍射直接积分法计算像面复振幅分布,其二是对子出瞳波面衍射直接积分在像面的复振幅进行叠加。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 GPIXP干涉仪对两种方法计算的像质进行了验证和对比。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;在衍射极限附近,前者的拟合精度也能满足像质的定性评估要求,且计算量较小。

The exit pupil wavefront of a segmented mirror Synthetic Aperture Optics（SAO） is discrete, and different from traditional system. To evaluate imaging quality, the theory of wave aberration and diffraction optics should be introduced simultaneously. By using the diffraction integral, two methods are used to evaluate imaging quality,one way is to fit the exit pupil wavefront to Zernike polynomial directly to calculate the complex amplitude distribution, and the other way is to calculate the complex amplitude distribution of each sub-exit-pupil individually, and overlap them in image plane. A segmented mirror system with three sub-mirrors was built, and the wavefront was obtained by ZYGO GPIXP interferometer, including overall exit pupil wavefront and each sub-exit-pupil wavefront. By comparing the two methods,the result shows that the latter is more precise but complex; the former is more simple and can satisfy the required precision, when the system exit pupil wavefront is near the diffraction limit.