有限角度水浸超声检测空间复合成像

为降低噪声及伪影对水浸B扫成像的影响,提高成像分辨率及对比度,研究了一种适用于水浸检测的有限角度空间复合成像方法。控制不同入射角,实现角域回波信号的采集,采用希尔伯特变换对回波信号进行包络处理,考虑水与工件的声学差异,通过修正渡越时间偏差及折射路径偏差对有限角度内的回波信号进行重构,实现空间复合成像。以钢试块的水浸超声检测为例,对入射角为-7°、-5°、-3°、-1°、0°、1°、3°、5°、7°的回波信号进行空间复合成像,成像结果表明相对于普通B扫查成像,其成像信噪比及对比度噪声比平均分别提高了9.1 d B、5.6 d B,成像横向分辨率平均提高了17.6%,为水浸超声检测提供了一种高精度B扫成像方法。

Limited-angle Spatial Compound Imaging for Immersion Ultrasonic Testing

To reduce the effects of noise and artifacts on immersion ultrasonic B-scan testing and improve imaging resolution and contrast ratio, a limited-angle spatial compound imaging method is proposed which is suitable for immersion ultrasonic testing. Firstly, angular domain echo signal was collected under different incident angles and enveloped by Hilbert transform. Then, considering the acoustic difference between water and the specimen, the limited-angle echo signal was reconstructed by correcting the transit time deviation and the refraction path change. Finally, the spatial compound imaging was achieved. Taking the immersion ultrasonic testing of steel block for an example, spatial compound imaging was realized when the echo signal was under different limited-angle of-7°,-5°,-3°,-1°,0°,1°,3°,5°,7°. The imaging results show that comparing with conventional B-scan imaging, the Signal to Noise Ratio and Contrast to Noise Ratio of spatial compound imaging are increased by an average of 9.1 dB and 5.6 dB respectively, the imaging lateral resolution is increased by an average of 17.6%. It provides a high-precision B-scan imaging method for immersion ultrasonic testing.