基于时间反转声学理论的超声相控阵超分辨率成像方法

在超声相控阵检测领域,常规成像方法遵守瑞利准则,其成像分辨率受到波长限制。研究时间反转多信号分类(Time Reversal-MUltiple SIgnal Classification, TR-MUSIC)方法,在保持超声波工作频率不变且不影响系统探测深度的前提下,可提高成像分辨率,实现超分辨率成像。通过全矩阵采集方法获取被测对象的超声阵列数据；利用平面B扫描和TR-MUSIC方法处理数据,得到二维和三维超声图像；依据图像特征评估被测对象内部状况。实验选取加工不锈钢试块作为被测对象,搭建超声相控阵检测系统,在试块内部加工6个直径为1 mm、可视为点散射体的相邻贯通孔作为缺陷。实验表明,TR-MUSIC方法能够区分并定位这6个相邻点散射体,而平面B扫描方法则不能。因此,基于时间反转声学理论的TR-MUSIC方法可以提高成像分辨率,改善超声图像质量。

Super resolution imaging method using ultrasonic phased array based on the time reversal acoustic theory

The imaging methods in the field of ultrasonic phased array abide by the Rayleigh criterion and its resolution is limited by ultrasonic wavelength. The time reversal with multiple signal classification, termed TR-MUSIC(time reversal-multiple signal classification), has been introduced to improve the resolution and achieve super resolution imaging under the premise of keeping the ultrasonic working frequency unchanged and maintaining the detection depth of the system. The ultrasonic array data from the test object can be captured via full matrix capture process. Then the data was post-processed by plane B scan as well as TR-MUSIC to obtain the 2-D and 3-D ultrasonic images. The test object was assessed according to the imaging results. A block of steel with six 1mm-diameter side drilled holes, which can be considered as point-like targets, has been machined as the test object. Furthermore, the detection system of ultrasonic phased array has also been built. It is shown that TR-MUSIC can distinguish and locate these targets while the method of plane B scan fails. Therefore, the TR-MUSIC based on the theory of time reversal can increase the imaging resolution, and improve the quality of ultrasonic image.