逆时偏移成像具有高精确性和适应复杂介质的优势，但该方法存在计算效率低、数据存储量大以及噪声的问题。为了解决这些问题使用FDTD（Finite-Difference Time-Domain，时域有限差分）算法计算地埋目标的波场数值，并实现电磁波场的逆时偏移成像，再使用波场分离技术和拉普拉斯滤波对成像算法进行改进。

针对波场数值模拟问题，通过构建TF-SF（Total Field-Scatter Field, 总场-散射场）边界模拟地埋环境下的平面波引入，并使用FDTD算法计算地埋目标波场数值，设置反射波接收点得到不同尺寸、材质、土壤介质等情况下地埋目标的回波信号，并分析了目标回波的变化情况与电磁波在介质中的传播规律，表明了FDTD算法能够快速计算地埋目标的波场数值。

针对地埋目标的成像问题，使用FDTD算法对源波场和接收波场分别进行波场延拓，并利用互相关成像条件完成对地埋目标的逆时偏移成像。同时，针对成像中存在的噪声问题，深入分析噪声产生的原因，使用波场分离技术与拉普拉斯滤波对算法进行改进，并测试了改进算法对地埋目标结构模型的成像效果，再分析了不同材质、土壤介质、信号脉宽等情况下地埋目标的成像特征，仿真结果证明：使用波场分离技术结合拉普拉斯滤波的方法改进后的算法能够分辨出不同情况下地埋目标的位置，并且当信号脉冲宽度为2ns时，陶瓷目标轮廓清晰，金属目标上方反射明显，表明改进后的算法能有效抑制低频噪声的影响，相较于传统逆时偏移成像算法提高了成像质量。

将改进的基于FDTD的逆时偏移成像算法应用到考古文物探测中，构建了三种不同类型的地埋文物模型，仿真结果证明：改进后的算法可以识别干黏土中夯土层上下层界面的轮廓，能够识别器物的材质、位置和瓷器的轮廓，表明改进后的算法可以为实际考古探测提供理论参考。

Inverse time migration imaging has the advantages of high accuracy and adaptability to complex media, but this method has some problems such as low computational efficiency, large data storage and noise. In order to solve these problems, FDTD (Finite-Difference time-domain) algorithm is used to calculate the wave field value of the buried target and realize the inverse Time migration of the electromagnetic wave field. Then wave field separation technology and Laplace filter are used to improve the imaging algorithm.

To solve the numerical simulation problem of wave Field, TF-SF (Total field-scatter Field) boundary is constructed to simulate the introduction of plane waves in buried environment, and FDTD algorithm is used to calculate the buried target wave field values. The echo signals of buried targets with different sizes, materials and soil media are obtained by setting the receiving points of reflected waves, and the changes of target echoes and the propagation law of electromagnetic waves in the media are analyzed, which shows that FDTD algorithm can quickly calculate the wave field value of buried targets.

In order to solve the imaging problem of buried targets, FDTD algorithm is used to extend the source wave field and the received wave field respectively, and the inverse time migration imaging of buried targets is completed by using cross-correlation imaging conditions. At the same time, in view of the noise problems existing in imaging, the causes of noise were deeply analyzed, the algorithm was improved by using wave field separation technology and Laplace filter, and the imaging effect of the improved algorithm on the structure model of buried targets was tested, and the imaging characteristics of buried targets under different materials, soil media, signal pulse width and other conditions were analyzed. The simulation results showed that: The improved algorithm using wave field separation technology and Laplace filtering method can distinguish the location of buried targets in different cases. When the signal pulse width is 2ns, the outline of the ceramic target is clear, and the reflection above the metal target is obvious, indicating that the improved algorithm can effectively suppress the influence of low frequency noise, and improve the imaging quality compared with the traditional inverse time migration imaging algorithm.

The improved inverse time migration imaging algorithm based on FDTD is applied to the archaeological relic detection, and three different types of buried relic models are constructed. The simulation results show that: The improved algorithm can identify the contours of the interface between the upper and lower layers of rammed soil in dry clay, and can identify the material and position of objects and the contours of porcelain, which indicates that the improved algorithm can provide theoretical reference for practical archaeological exploration.

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