傅里叶望远镜对实际有纵深目标成像的研究

Study on target imaging with varying depth by Fourier telescope

为了实现傅里叶望远镜对有纵深的真实目标高分辨率成像,利用成像基本公式,采用先直观定性分析后计算机定量仿真的方式开展研究。原理分析得出米级纵深目标的回波最大延迟时间差为6.7 ns。定性分析指出信号周期远大于6.7 ns时,傅里叶望远镜可以对米级纵深目标成像;信号周期约为6.7 ns或则更小时,成像质量将严重下降。定量分析先给出回波最大延迟与信号周期比从0至1/8范围内的重构图像结果和Strehl值的比较,得出延迟与周期之比小于1/32时还能获得可识别目标重构图像的结论。然后再比较分块数分别为2、4和8时重构图像结果及Strehl值,得出在满足信号周期远大于最大延迟条件下,目标纵深变化对成像无影响的结论。通过对纵深在10 m以内目标的仿真研究,得出外差频率低于466 k Hz的信号可重构出可识别的目标图像的结论。

In order to realize high-resolution target imaging with varying depth by Fourier telescope,the basic imaging equations are used and the study is proceeded with the method of intuitively qualitative analysis at first,and then with the method of computer-aided quantitative analysis. The longest echo time delay of targets with meter-order depth is 6. 7 ns according to principle analysis. Qualitative analysis points out that Fourier telescope can image targets of meter-order depth when the signal period is far longer than 6. 7 ns; and the imaging quality will decline when the signal period is about 6. 7 ns or shorter. Quantitative analysis has compared the reconstructed results and Strehl values when the ratios of largest echo delay and signal period are between 0 and 1 /8,and identified reconstructed target images can be obtained when the ratio is smaller than 1 /32. After that,the reconstructed results and Strehl values have been compared when the segments are 2,4 and 8,and then the varying depth of target has no effect on imaging when the signal period is far longer than largest delay. The identified image can be reconstructed by signals when heterodyne frequency is less than 466 k Hz according to the simulation of targets with depth less than 10 meters.