聚焦超声声场中的散射体成像方法

在实验室条件下,研究了聚焦超声声场中的散射体成像问题。将一个纽扣作为散射体置于一聚焦换能器所产生的声场中,以频率为1.17MHz的脉冲信号经功率放大后激励聚焦换能器,声波作用于纽扣后发生散射,借助于三维自动扫描系统和PVDF膜片水听器,测量得到了散射声场中前三次谐波的声场分布,膜片水听器敏感元件有效尺寸为1mm。利用角谱法反演了散射体所在处的声场,通过与散射体实际的形状特征进行比较,发现反演的结果与散射体特征吻合良好,由此得出结论,在信噪比足够大的情况下,利用聚焦声场所产生出的高次谐波,可以得到分辨率较高的成像效果。

Scatter imaging in focused ultrasonic field

Under laboratory conditions,the problem on scatters imaging in focused ultrasonic field is studied.A fastener as a scatter is put in the acoustic field of a focused transducer,and inspirit with tone burst signals of 1.17MHz.The field distributions of the first three harmonics are measured by using a 3D automatic scanning system and a PVDF membrane hydrophone,in which the size of the active element is about 1mm.The acoustic field where the fastener lies is calculated with the angular spectrum method.The results are in good agreement with the shape character of the fastener.The conclusion is drawn that high quality imaging can be obtained by utilizing the harmonics wave in focus field as long as the signal to noise ratio is satisfied.