【摘要】 动态聚焦超声换能器，由６个不同面积、等间距、等宽度的同心圆环和中心圆片组成的平面换能器作为声发射基阵，通过改变辐射孔径和每个辐射圆环的电激励信号延迟时间，实现动态聚焦；同时，保证各聚焦处声强一致．作者利用声辐射原理和傅里叶光学变换，推导出聚焦声场声压分布表达式，设计出换能器的具体结构参数．结果表明，该系统聚焦范围大，在７７～１５７ｍｍ之间分６档可调．聚焦换能器近场声束较宽，不同聚焦处波束宽度在４．９～３．０ｍｍ范围内变化．通过计算机模拟仿真，取得和理论设计要求一致的结果．更多还原

【Abstract】 In order to carry out activation hematoporphyrin with ultrasound for anticancar, the dynamic focusing ultrasound transducer is studied. The transducer is considered as acoustic transimission array, which consists of six equal step and width annular elements and the center elements. By changing transimission aperture and adjusting delayed time of electric signals applied to every transmission elements, not only can the varible focal length be obtained, but a also the same acoustic power can be kept in every focusing position. A formula which is convenient for numerical calculation of acoustic pressure on the focusing plane is derived with the principle of acoustic radiation and Fourier optics. The system of focusing range is bigger, which has six focal length between 77mm and 157mm. Near field beamwidth of the focusing transducer is varible between 4.9～3.0 mm. Calcaulatd results by computer are in very good agreement with the theoretical design.更多还原