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一般超声回波检测、时间反转和逆时偏移技术,都不能将界面附近的目标(缺陷)检测出来。这是因为目标反射波和界面(或底面)反射波相重叠的缘故。虽然改进的时间反转法(即换元的时间反转法)能够区别目标和界面(或底面),但还是不能定位。本文提出一种时间反转和逆时偏移混合方法。分析和仿真结果表明该方法不但能够鉴别出层状介质中的目标,而且可以定位。对于多个目标,也能给出其位置分布图。特别地,本文方法对于分层介质中的缺陷和浅海海底下的目标检测和定位具有重要的潜在价值。
General ultrasonic echo detection, time reversal and inverse time migration techniques, can not be detected near the interface target (defect). This is because the target reflected wave and the interface (or bottom surface) reflected wave overlap. Although the improved time reversal method (ie, the time reversal method of commutation) can distinguish between the target and the interface (or the bottom surface), it can not be located. This paper presents a hybrid method of time reversal and inverse time offset. The analysis and simulation results show that this method not only can identify the target in layered media, but also can locate. For multiple targets, but also given its location map. In particular, the proposed method has important potential for detecting defects in layered media and for detecting and locating targets under shallow seas.