激光超声的多模式合成孔径聚焦成像仿真分析

Simulation analysis of multi-mode synthetic aperture focusing technique based on laser ultrasound

针对激光超声体波在检测材料内部缺陷时反射信号弱、信噪比较差的问题,提出了一种基于激光超声的多模式合成孔径聚焦成像方法。通过耦合激光激发超声方向性、干涉仪探测超声方向性、超声波与缺陷作用后声场分布方向性得到声场灵敏度图,再根据声场灵敏度图和不同模式波的传播特性预测不同位置分布缺陷的最佳成像模式波,从而使用多模组合的合成孔径聚焦成像方法对缺陷成像。使用有限元方法对该成像过程进行数值模拟来验证其可行性,成像结果与理论预测一致。采用这一缺陷成像方法可减小盲区,消除伪像,从而提高图像质量。

To deal with the weak reflection signal and poor signal to noise ratio in the detection of internal defects via laser ultrasound, we proposed a multi-mode synthetic aperture focusing technique(SAFT) based on laser ultrasound. By coupling the directivity of laser exciting ultrasound, interferometer detecting ultrasound and ultrasonic filed interacting with defects, we can obtain the sensitivity image, then based on the sensitivity image and characteristic of different waves, the most suitable mode for defects in different locations can be determined. Finally, using the multi-mode combination SAFT to image defects. This imaging method is simulated numerically by the finite element method to verify its feasibility, simulation results coincide well with the theoretical prediction. The proposed imaging method can reduce blind areas, eliminate fake images and improve the image quality.