振动声成像系统分辨率研究

本文从振动声成像的基本原理出发，通过引入点扩展函数PSF和定义轴向响应函数ARF，研究了由凹球面聚焦换能器分割而成的一种典型共焦换能器参数对振动声成像系统侧向分辨率和轴向分辨率的影响。计算研究表明：增大凹球面换能器的口径、减小几何焦距和提高中心频率均可以提高系统的侧向分辨率和轴向分辨率；但改变凹球面换能器的分割比例对两种分辨率影响不尽相同。综合考虑超声换能器激励、聚焦性能以及产生的辐射力效果等因素，则换能器应按等辐射面积原则分割为宜。文中还分析了介质的声衰减系数对实际轴向分辨率的影响。

Resolution of a vibro-acoustography system

The effect of parameters of a typical confocal transducer, which is made from dividing a concave focusing transducer into two concentric parts, on the transverse and axial resolutions of a vibro-acoustography system is studied theoretically by introducing the point spread function (PSF) and defining the axial response function (ARF) based on the basic principle of vibro-acoustography. The computation analysis indicates that increasing the aperture of the concave focusing transducer, decreasing it's geometric focal length or raising it's central working frequency can improve the transverse and axial resolutions of the system simultaneously, but changing the dividing proportion of the transducer affects the two kinds of resolution differently. On compromisingly considering several factors including the exciting mode, the focusing ability and the radiation force effect, the concave focusing transducer should be divided into two equal-area parts. The effect of the acoustic attenuation coefficient of the media on the actual axial resolution have also been discussed.