金属圆柱腔体中使用非均一背景增强微波断层成像

Enhancing microwave tomography in a circular metallic chamber by an inhomogeneous background

针对基于圆柱金属腔体的微波断层成像系统,提出了一种利用非均一背景增强系统获取目标信息能力的方法.该方法通过在腔体内放置已知物体构成非均一背景,这样不但能利用背景的先验信息,而且可以增加等效辐射源对目标进行探测.首先,利用矩量法计算圆柱金属腔体内非均一背景的格林函数和离散积分算子,并对离散积分算子进行奇异值谱和条件数分析,在理论上证明该方法的可行性;然后,利用基于有限元的对比源逆成像法对均一背景、有耗非均一背景和无耗非均一背景三种情况进行仿真研究;最后对仿真结果进行了误差分析和比较.仿真结果表明,该方法可以提高反演收敛速度和结果准确度,有耗非均一背景略优于无耗非均一背景.该方法可以在不改变硬件系统和算法的情况下得到更准确的反演结果,可应用于医学成像与工业无损探测.

Microwave tomography is enhanced by using an inhomogeneous background. In this paper, the measurement region is located in a circular perfect electrical conductor （PEC） chamber where a known object is placed inside the imaging domain as an inhomogeneous background. This can not only make use of the prior information about the background, but also increase the equivalent radiation source for the target detection. The Green function of a circular PEC chamber with inhomogeneous background is obtained using the method of moments. Based on the Green functions for both homogeneous and inhomogeneous background in circular PEC chamber, the properties of the radiation operators are analyzed by comparing the condition numbers and the singular value spectra. Simulations are carried out in homogeneous, lossless inhomogeneous and lossy inhomogeneous backgrounds respectively, and the relative errors are discussed. The results show that using inhomogeneous background can improve the convergence rate and accuracy, and the lossy inhomogeneous background produces better results than the lossless one. In addition, it can enhance the inversion results without changing the microwave tomography system, which can be used in the medical imaging and industrial nondestructive detection.