基于图像聚焦度评估的穿透成像自聚焦理论与实验研究

Through medium with unknown parameters has been the fatal problem that constraints the application and development of the subsurface imaging technology all along. Autofocus is the most potential technology to solve the problem. Since the practical complex scene for subsurface penetrating radar, the through medium has multi-parameters with wide range. To achieve stable autofocus is difficult. So the autofocus theory and method is to be studied for two kinds of image with distinct space characteristics coming from ground penetrating radar and holographic subsurface radar, based on the evaluation of image focusing metric. All sorts of focusing function are to be analyzed and evaluated by the sufficient experimental data, and the focusing function with good performance is to be selected. To discover the intrinsic mechanism, characteristic and validity of autofocus, the reasonable model of the medium and target is constructed and the autofocus theoretical analysis of different subsurface imaging method is carried out. By taking advantage of experimental study and theoretical analysis results, some robust and efficient autofocus methods is proposed for no medium parameter constraint. Project research will promote the development and application of the subsurface imaging technology, and lay a foundation for the formation of subsurface imaging autofocus theory and method.

介质参数未知一直是制约穿透成像技术应用和发展的致命问题，自聚焦是解决这个问题最有潜力的技术。由于穿透雷达的实际应用场景复杂，穿透介质的参数变化大，参数多，实现稳定自聚焦困难。为此针对探地雷达和全息穿透雷达的两类空间图像特点，开展基于图像聚焦度评估的自聚焦理论与方法研究。在充分的实验数据基础上，完成图像聚焦度函数的实验分析评估，并且筛选和构建具有良好性能的聚焦度函数。构建合理的介质和目标模型，分析不同穿透成像方法自聚焦的内在机理和特性，进行自聚焦有效性的理论分析。基于实验研究和理论分析的结果，研究提出稳健、高效的自聚焦方法，实现无介质参数约束的良好自聚焦。项目研究能够有力推动穿透成像技术的发展和实用化，为形成系统的穿透成像自聚焦理论和方法奠定基础。

针对合成孔径穿透成像技术的不足，以未知介质参数的复杂媒质中隐蔽目标的穿透成像技术发展和应用为背景，利用实验室自主研发的HSR设备和GPR设备完成了大量的实验数据采集；在穿透成像技术的基础上，结合杂波抑制技术和自聚焦成像理论，从实验和理论分析开展了基于图像聚焦度评估的自聚焦穿透成像的基础研究，包括适用于穿透成像的聚焦度函数研究和实验验证、不依赖于介质参数的自聚焦穿透成像方法、基于图像幅度和最小化的自聚焦方法、盲反卷积的快速自聚焦穿透成像方法、基于谱域滤波的曲面自聚焦成像方法、基于空间域滤波的曲面介质自聚焦成像方法和基于回归分析的曲面介质自聚焦成像方法；为提高自聚焦成像效果，研究了关键的数据预处理方法，包括校正天线方向图影响的雷达成像数据预处理方法和基于小波分析和主成分分析的探地雷达自适应杂波抑制方法；对三维的自聚焦成像方法开展了初步的创新性研究，并取得初步的成果。