中文摘要：

传统超声成像方法如合成孔径聚焦技术、超声衍射时差法，只能确定缺陷的位置，无法对整个缺陷形貌进行成像。逆时偏移方法基于波动方程、有限元或有限差分等方法计算声源的正延拓声场分布和接收回波的逆时延拓声场分布，并对其采用互相关等成像条件，可以成像缺陷的形貌。针对平底狭缝铝块试样，采用多阵元超声换能器扫描，将接收数据用于成像，并与合成孔径聚焦技术的成像比较，结果很好验证了逆时偏移成像方法的优越性。

英文摘要：

Traditional ultrasonic imaging methods, such as the synthetic aperture focusing technique and the time of flight diffraction, can find the position of a defect. However, it cannot image shape and appearance of the defect. The reverse time migration （RTM） method based on wave equation and implying the cross-correlation imaging condition between source propagation field and back-propagation field, which are calculated from measuring data by using finite element or finite differential method, can image shapes and appearances of defects. A multi-elements transducer is used to scan aluminum sample with a slot in our experiment. Comparing with synthetic aperture focusing technique, RTM imaging results show that it is a method superior to traditional one.