斐索型合成孔径望远镜实时共相检测与闭环共相控制联合研究

For the ground-based Fizeau optical synthetic aperture telescope, the co-phasing error should be measured in real time and corrected by closed-loop controlling because of the atmospheric turbulence effect，and the co-phasing error should be steadily controlled in one tenth of the wavelength. The existing co-phasing detecting methods have their own limitations and shortcomings, and have weak connection with co-phasing correction controlling, which is difficult to meet the current application requirements. Thus a joint optimization method that applied real-time co-phasing detecting and closed-loop co-phasing controlling method was proposed for correcting dynamic piston error. The research includes a polynomial fitting direct co-phasing detecting method based on the peak ratios of the dispersed interferogram，an indirect co-phasing detecting method based on the object function of the peak ratios of the dispersed interferogram，a positive-negative sign and value estimating method for piston error and a real-time co-phasing controlling method by combining co-phasing detecting and closed-loop co-phasing correction. This project plans to investigate the proposed co-phasing detecting and closed-loop controlling method by theoretical study, numerical simulations and conducting laboratory experiments with the purpose of enhancing their accuracy, stability and real-time performance, and accelerating the application of them into practice. Results from this research have the potential to provide new way and effective reference for deeper co-phasing system designs of larger diameter Fizeau optical synthetic aperture telescope in future.

地基斐索型合成孔径望远镜会受到大气湍流的影响，需要对共相误差进行实时检测与闭环校正，且将共相误差稳定控制在十分之一波长范围内。现有共相检测方法存在着各自的局限性和不足之处，且与共相校正控制关联性差，难以满足当前应用需求。提出针对动态变化相位平移误差的实时共相检测与闭环共相控制联合优化方法。具体包括基于色散干涉条纹峰值比的多项式拟合直接共相检测方法、基于色散干涉条纹峰值比目标函数值的间接共相检测方法、相位平移误差正负性与大小判定方法以及将共相检测与闭环共相校正相联合的实时共相控制方法。本项目从理论分析、数值模拟以及多平台实验验证三方面着手，对提出的实时共相检测与闭环共相控制联合优化方法进行深入研究，以提高闭环共相控制的精度、稳定性和实时性，加快共相方法在实际系统中的应用，最终为大口径斐索型合成孔径望远镜共相系统的研制提供技术参考。

斐索型合成孔径望远镜依据像面干涉成像原理，能对点目标、扩展目标以及运动目标实时成像，其最大优点是基线短，结构紧凑，不需要大行程的延迟线和光程差补偿，充分利用基线实现频率域覆盖。斐索型合成孔径望远镜实现高分辨率成像的关键是保持各子望远镜或子镜到焦面的光程差近乎一致，由此保证各子光束在焦面上同位相相干叠加，且共相误差必须稳定控制在十分之一个波长范围内。首先开展了四棱锥波前传感器在空间斐索型合成孔径望远镜共相中的研究，充分发挥该传感器光能利用率高、灵敏度高、测量效率高的优势（可以对几十、几百个子镜同时测量），提出了一种空间稀疏孔径望远镜共相控制装置及控制方法，完成了理论分析与实验验证；在开展的实验中利用四棱锥波前传感器对两个孔径间的共相平移误差进行探测，采用本项目提出的光瞳像标定方法，实现了双孔径光瞳像的高精度标定，标定精度优于1个像素；实现了共相误差的稳定闭环校正，最终的误差被控制在16纳米的范围内。提出了一种拼接望远镜系统色散共相检测波长标定方法，完成了理论分析与实验，获得了优于1nm的波长标定精度；在此基础上，对该波长标定方法进行了进一步优化，新的标定方法大幅度提高了波长标定效率。提出了一种实时共相检测与闭环共相控制联合优化方法，完成了仿真分析与实验验证，针对初始值为30微米左右的平移误差，只需经过几次的迭代校正，相位平移误差被校正到20纳米范围内。本项目选题为当前大望远镜研制的前沿与热点问题，重要意义还在于：本项目研究的实时共相检测与闭环共相控制联合优化方法无疑将会对我国的光干涉检测技术及天文仪器等的发展起到很大的促进作用，为未来更大口径空间光干涉望远镜的研制提供技术方案参考。尤其是子镜间相位检测与控制技术还可以扩展到未来的月基、空间干涉望远镜以及长基线干涉阵列望远镜的研究之中。