Through-transmission ultrasonic imaging of sub-surface defects using non-contact laser techniques
Through-transmission ultrasonic imaging of sub-surface defects using non-contact laser techniques
复制标题
使用非接触式激光技术对亚表面缺陷进行透射超声成像
DOI：
10.1016/0143-8166(92)90007-t
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发表时间：
1992
期刊：
影响因子：
--
通讯作者：
Q. Shan
中科院分区：
文献类型：
--
作者：
R. Dewhurst;Q. Shan
采用非接触式激光组合系统进行了透射超声无损检测。高功率（~ 2 MW）激光脉冲用于在金属样品中产生纵向脉冲。在到达远表面时，用50 cm的共焦法布里-珀罗干涉仪检测超声。干涉仪分析了反向散射激光的散斑，因此可以从只有机械加工的样品中进行测量。信噪比足够好，可以进行二维扫描，产生人工缺陷的光学图像。为了改善图像质量，考虑样品表面反射率的变化对信号进行归一化。还使用中值滤波。实验结果表明，该系统可获得直径为4 mm的钻孔图像，分辨率为± 0.5mm。
Through-transmission ultrasonic NDT measurements have been performed with a non-contact laser combination system. High power (~2MW) laser pulses were used for the generation of longitudinal pulses in metallic samples. On reaching the far surface, ultrasound was detected with a50cm confocal Fabry-Perot interferometer. The interferometer analysed speckle from back-scattered laser light so that measurements could be made from samples with only a machine finish. Signal-to-noise ratios were sufficiently good for two-dimensional scans to be performed, producing optical images of artificial defects. For improved image quality, signals were normalised taking into account changes in sample surface reflectivity. Median filtering was also used. Results show that images of4-mm diameter drill holes can be obtained with resolutions of±0·5mm.