基于管状声学超透镜的聚焦成像研究

发布时间：2018-08-31 13:50

【摘要】：声子晶体利用其独特的负折射特性能够实现对声波的聚焦,这一奇特的物理现象引起了广大科研工作者的关注。在海洋探索,开发和防卫上,利用声学聚焦可以实现高分辨率成像声呐;医学上,声学聚焦能够为治疗肿瘤提供更安全有效的治疗手段,声学聚焦技术的应用具有很大的技术优势和实用价值,利用声学物理透镜实现声波的聚焦是更先进的科技前沿,所以声学透镜的理论与设计有极其重要的研究价值。本文在局域共振型声子晶体、负折射理论等相关知识的基础上,结合声学聚焦技术的应用前景、声透镜发展现状和声成像的需要,提出并设计了一种新型的管状声学超透镜结构并建立了其简易模型;详细的阐释了声波在声子晶体中的传输过程以及负折射的形成;通过分析声子晶体元胞振动特性得出了负折射形成的理想频率范围,运用层多散射法得出了透镜的能带结构图,最终利用COMSOL Multiphysics软件模拟了近场点声源在理想频率下通过不同厚度的管状声学超透镜后的声波传输和聚焦情况,得到了透射率和反射率的关系曲线,确定了最佳成像效果时透镜的厚度;并且在理想厚度下,模拟了不同入射频率下管状声学超透镜的聚焦效果,得到了半峰全宽(FWHM)曲线,确定了最佳入射频率。在仿真结果中,都观察到入射波和出射波的波形基本接近,弥散现象很弱,仿真结果与理论达成了很好的一致,很好的验证了该管状声学超透镜可以对近场点声源实现良好的聚焦成像。
[Abstract]:Phononic crystals can focus acoustic waves with their unique negative refraction characteristics. This strange physical phenomenon has attracted the attention of many researchers. In ocean exploration, development and defense, high-resolution imaging sonar can be achieved by using acoustic focusing; in medicine, acoustic focusing can provide a safer and more effective treatment for tumors. The application of acoustic focusing technology is of great technological advantage and practical value. It is a more advanced technology frontier to focus acoustic waves with acoustic physical lenses. So the theory and design of acoustic lenses are of great research value. Based on the application prospect of acoustic focusing technology, the development status of acoustic lens and the need of acoustic imaging, a new tubular acoustic superlens structure is proposed and designed, and its simple model is established. The ideal frequency range of the negative refraction is obtained. The band structure of the lens is obtained by using the layer multiple scattering method. Finally, the transmission and focusing of the near-field sound source through a tubular acoustic superlens with different thickness are simulated by using COMSOL Multiphysics software. The optimum thickness of the lens is determined by the curve, and the focusing effect of the tubular acoustic superlens is simulated under the ideal thickness at different incident frequencies. The FWHM curve is obtained and the optimum incident frequency is determined. The simulation results are in good agreement with the theory, which proves that the tubular acoustic superlens can achieve good focusing imaging for near-field acoustic sources.
【学位授予单位】：中北大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：O735;TH74

【相似文献】