三种降采样成像策略的性能优化以及与传统傅里叶望远镜的比较

Performance optimization of three down-sampling imaging strategies and their comparison with the conventional Fourier telescope

为了获得成像质量较好且成像时间较少的新型傅里叶望远镜成像策略,本文比较了三种降采样成像策略(压缩感知方法 (CS)、低频全采样方法 (LF)和变密度随机采样方法 (VD))与传统傅里叶望远镜(FT)在图像质量和成像时间上的差异.分析方法如下:利用传统FT外场实验所获得的目标频谱数据作为基础,三种降采样方法 (LF, VD和CS)分别按照各自的采样模式和重构方法实现目标图像的重构;通过直观观察和Strehl比两种方法比较三种降采样方法与传统FT在图像质量上的差异;通过分析成像时间的组成要素,初步比较三种降采样方法与传统FT在成像时间上的差异.分析表明:1)压缩感知方法的图像质量优于其他两种降采样方法 (LF和VD),但略低于传统成像结果; 2)压缩感知方法在成像质量上略低于传统FT,但在成像时间上却明显小于传统FT; 3)分析中采用的外场数据均含噪声,这说明上述三种降采样重构过程对噪声有较好的鲁棒性.综合上述分析结果可以看出,基于压缩感知的傅里叶望远镜(CS-FT)是在实际含噪情况下可大幅减少成像时间的优良成像策略.

In order to obtain a new imaging strategy of the Fourier telescope(FT)with a better imaging quality and a less imaging time,we optimize and compare three down-sampling imaging strategies in this paper:the compressed sensing method(CS),the low-frequency full sampling method(LF)and the variable-density random sampling method(VD),which are different from the traditional Fourier telescope in both of the image quality and the imaging time.The analytical methods are as follows:based on the target’s spectral data obtained from the field experiment of traditional FT,three down-sampling methods(LF,VD and CS)are used to reconstruct the target’s images according to their own sampling modes and reconstruction methods,respectively;the differences between the three down-sampling methods and the traditional FT regarding the image quality are compared by the instinctive observation and the Strehl ratio;based on the analysis of the imaging time,the differences between the three down-sampling methods and the traditional FT regarding the imaging time are preliminarily compared.The analysis shows that:1)the image quality of the compressed sensing method is better than that of the other two down-sampling methods(LF and VD),slightly lower than that of the traditional imaging;2)although the image quality of the compressed sensing method is slightly lower than that of the traditional FT,its imaging time is much lower than that of the traditional FT;3)the field data used in the analysis contain noises,which means that the reconstruction methods of the above three down-sampling strategies have a better robustness to the noises.Based on the above results,it can be seen that the Fourier telescope based on compressed sensing(CS-FT)is an excellent imaging strategy which can greatly reduce the imaging time in the condition with actual noises.