Weighted Conical Type Limited-Diffraction-Beam Transducers for High-Resolution Ultrasound Imaging

本课题的研究目的是研制一种具有锥形辐射面的新型高分辨率超声成像有限衍射光束换能器。本项目得到的结果如下：(1)提出了离散加权结构，这将有利于加权锥形换能器的制造。由离散加权的分锥组成的分锥换能器的声场与连续加权的全锥换能器的声场基本相同。(2)研究了一种简单实用的实现加权锥形换能器的方法，即通过在换能器上形成均匀宽度的窄电极条，对振动区域进行消去。(3)采用1-3连通的压电复合材料制备了一种加权锥形换能器，其机电耦合系数大于PVDF薄膜。结果表明，压电复合材料较大的机电耦合系数可使换能器的灵敏度提高7 dB以上。(4)通过b模成像的初步实验证明，在大深度上可以保持高分辨率。

The purpose of this research project is to develop a new type of limited-diffraction-beam transducer which has a conical radiation surface for high-resolution ultrasound imaging. The results obtained in this project are as follows :(1)Discretely weighted structures have been presented that will facilitate the fabrication of weighted conical transducers. Divided conical transducers composed of a segmented cone with discrete weighting can create sound fields almost the same as those for the continuously weighted complete conical transducers.(2)A simple and practical method of realizing weighted conical transducers have been examined that uses apodisation on the vibration area by forming narrow electrode strips of a uniform width spreading radially on the transducer.(3)A weighted conical transducer has been fabricated using a piezoelectric composite with 1-3 connectivity that has the electromechanical coupling coefficient larger than that of a PVDF film. It has been shown that the large electromechanical coupling coefficient of the piezocomposite material increases the transducer sensitivity by 7 dB or more.(4)It has been demonstrated through preliminary experiments with B-mode imaging that high resolution is maintained over a large depth.