Wu Yong, Hui Mei, Li Weiqian, Liu Ming, Dong Liquan, Kong Lingqin, Zhao Yuejin
Opt Express. 2021 Mar 29;29(7):10249-10264. doi: 10.1364/OE.420512.
Optical synthetic aperture imaging system has grown out the quest for higher angular resolution in astronomy, which combines the radiation from several small sub-apertures to obtain a resolution equivalent to that of a single filled aperture. Due to the discrete distribution of the sub-apertures, pupil function is no longer a connected domain, which further leads to the attenuation or loss of the mid-frequency modulation transfer function (MTF). The mid-frequency MTF compensation is therefore a key focus. In this paper, a complete mid-frequency compensation algorithm is proposed, which can extract and fuse the frequency of different synthetic aperture systems and monolithic aperture systems according to their special MTF characteristics. The dimensions of the monolithic aperture and optical synthetic aperture system are derived, and the longest baseline of the monolithic aperture is much smaller than that of the optical synthetic aperture system. Then the separated spatial frequency information is extracted and synthesized according to the spatial frequency equivalence point. Finally, the full-frequency enhanced image is recovered by using improved Wiener-Helstrom filter, which adopts specific parameters based on different sub-aperture arrangements. The mid-frequency MTF of Golay-3 increases from 0.12 to 0.16 and that of Golay-6 increases from 0.06 to 0.18. Both the simulation and experiment prove that the proposed method not only realizes the spatial resolution determined by the longest baseline of the optical synthetic aperture system, but also successfully compensates its mid-frequency MTF.
光学合成孔径成像系统源于天文学中对更高角分辨率的追求，它将几个小的子孔径的辐射组合起来，以获得与单个填充孔径相当的分辨率。由于子孔径的离散分布，光瞳函数不再是一个连通域，这进一步导致中频调制传递函数（MTF）的衰减或损失。因此，中频MTF补偿是一个关键重点。本文提出了一种完整的中频补偿算法，该算法可以根据不同合成孔径系统和整体孔径系统的特殊MTF特性来提取和融合它们的频率。推导了整体孔径和光学合成孔径系统的尺寸，且整体孔径的最长基线远小于光学合成孔径系统的最长基线。然后根据空间频率等效点提取并合成分离的空间频率信息。最后，使用改进的维纳 - 赫尔斯托姆滤波器恢复全频率增强图像，该滤波器根据不同的子孔径排列采用特定参数。Golay - 3的中频MTF从0.12提高到0.16，Golay - 6的中频MTF从0.06提高到0.18。仿真和实验均证明，所提出的方法不仅实现了由光学合成孔径系统最长基线确定的空间分辨率，还成功补偿了其中频MTF。
