Applying Plane Wave Imaging Technology in Ultrasonic Nondestructive Testing

Along with such advantages as high resolution over the entire area of reflector image reconstruction and the ability to produce images taking into account the reflection from and transformation of wave type at the boundaries of a test object, reconstruction of reflector images by the digital antenna focusing (DFA) method has several disadvantages, including a large volume of measured echo signals, long image reconstruction time, and an insufficiently high energy of ultrasonic waves introduced into the test object. Plane wave imaging (PWI) combines the benefits of phased antenna array (PAA) and DFA technologies. In the PWI mode, all elements of the antenna array (AA) operate when a plane wave is emitted (as in the PAA mode), which makes it possible to increase the energy introduced into the test object, and echo signals are recorded by all elements of the AA (as in the DFA mode). Reflector images are reconstructed by the SAFT method. To produce an image, one can use the number of emitted plane waves less than the number of elements in the antenna array, thus decreasing the volume of measured echoes. Transferring calculations into the domain of spatial sectors allows improving the performance of reconstructing the images of reflectors. Model experiments have shown the positive and negative aspects of producing the images of reflectors by the PWI method compared to the DFA technique both with and without a wedge.