Golay3型光学稀疏孔径系统退化图像的频率信息提取及合成研究
Frequency Extraction and Degraded Image Synthesis for Golay3 Type Optical Sparse-Aperture Systems
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摘要: 利用组成星座的小卫星,分别携带分离的子望远镜和合光成像望远镜,构成Fizeau型光学综合孔径干涉系统,实现高分辨率的面源目标成像是当前的研究热点之一。这种光干涉成像系统,由于稀疏度较大,UV覆盖不全,即空间频率采样不连续,表现为系统光学传递函数有零值存在。要克服UV覆盖不全的影响,获得等效的大孔径望远镜成像效果,需要改变子孔径的空间排布,获得不同基线条件下的图像,进行空间频率信息的提取和合成,最后采用逆滤波的方法达到提高图像质量的目的。在分析单子孔径传递函数与系统传递函数关系的基础上,优化子孔径的排布方式,采用不同的频域滤波器将不同基线获得的图像中信噪比高的频率区域提取出来进行合成,再变换到空域并进行逆滤波处理,得到改善的合成图像。仿真结果显示,当得到的干涉图信噪比较低时,该方法可以有效地提高合成图像的质量。Abstract: A Fizeau-typesparse-aperture imaging system made of a constellation of telescope-bearing satellites can potentially achieve extremely high resolution. But in such a system, the Modulation Transfer Function (MTF) usually contains a zero value. This means that the system fails to acquire a particular spatial frequency. To overcome this problem, we acquire multiple degraded images by repeatedly changing the sub-aperture configuration and then synthesize their spatial frequencies to create a single improved image. We first analyze the MTFs between each individual sub-aperture and the whole sparse aperture system. Then, we design new sub-aperture configurations that acquire more spatial frequency and use frequency-domain filters to extract the high-SNR part from each degraded image. Finally, we synthesize these frequencies before image reconstruction. Our results demonstrate that this method effectively improves the quality of the final synthesized image by obtaining as much spatial frequency information from all degraded images as possible.