为提高工业超声显微镜的成像分辨率，需要用高灵敏度的超声聚焦换能器。本文对研制的聚焦换能器的等效电路进行了理论分析，利用Matlab软件，数值模拟了聚焦换能器沿轴线方向辐射的脉冲聚焦声场，讨论了聚焦换能器的脉冲声场特性。采用特殊工艺研制压电晶片，用环氧树脂和钨粉的混合物作背衬，由此研制的主频为20 MHz宽带窄脉冲有源自聚焦换能器，在实际检测中回波仅有一个波形，缺陷的成像分辨率达0.4 mm。

High sensitivity transducers are essential in improving the image resolution of industrial ultrasonic microscopes. The equivalent circuits of the ultrasonic focused transducer are analysed by Mason's equivalent circuit, the pulse focused sound fields are simulated with Matlab in the direction of the focused transducer axis，and the results are compared with the sound fields of circle flat transducer. The transducing piezoid is developed with special technologies, and with the mixture of epoxide and tungsten powder for backing, the ultrasonic transducers enjoy good qualities of narrow pulse, higher sensitivity, higher resolution, among others. In applications, the returning wave of broadband narrow pulse focused transducer (with center frequency of 20 MHz) is merely of one waveform and the image resolution for flaws in testing multi-layer composite materials reaches up to 0.4 mm.