基于周期结构负反射的远场增强成像研究

Research on far-field enhanced imaging based on negative reflection of periodic structure

远场高分辨率成像是近几年来声学和光学领域的研究焦点之一,倏逝波无法在介质中传播成为将高分辨率成像带入远场的最大困难.本文提出了一种均匀排列的散射钢柱构成的超构散射体成像方式,利用周期结构负反射现象将倏逝波信息转化为可传播波来增强成像.有限元数值模拟被用来研究和验证该方案的可行性,结果显示波长3.4 mm的声波可以在20 cm外的远场获得大约0.6个波长的成像分辨能力.通过减小散射体的晶格常数有希望达到更高分辨率成像.

Far-field high resolution imaging is one of the research focus in the field of acoustics and optics in recent years. The greatest di？culty for high resolution imaging in the far field is the evanescent waves not being able to propagate in the medium. A kind of scatterers composed of uniformly spaced steel columns is presented in this work. Negative reflection of periodic structure can change the evanescent waves to the waves that can propagate to enhance imaging. A finite element simulation has been used to study and verify the feasibility of the scheme. Results show that with the sound wave of 3.4 mm wavelength one can obtain an imaging resolution of about 0.6 wavelength in the far field of 20 cm. We further note that by reducing the lattice constant of scatterers a higher far-field resolution imaging can be hopefully reached.