Ultrasonic super resolution imaging for sizing of extended target in solid

In this paper, phase-coherent multiple signal classification (PC-MUSIC), the typical ultrasonic super resolution imaging method, has been utilized to image and sizing the extended target in solid. Firstly, an experimental ultrasonic array system has been built to collect the real data from the test object via full matrix capture (FMC) process, and the data can be time-gated to extract the scattered signals related with the extended target. Secondly, the scattered signals are post-processed by PC-MUSIC over a given frequency bandwidth to obtain the ultrasonic image with high resolution. Lastly, a sizing method based on ultrasonic image, via calculating the −6 dB main lobe width, is proposed to assess the length of extended target, and its error is also calculated. The experiment has been implemented on a block of Al with a 10 mm long slot, larger than the ultrasonic wavelength at the central frequency of array. Experimental results show that PC-MUSIC considering phase information in the imaging process can correctly assess the length of extended target under some dimension of signal subspace.