Ultrasonic Phased Array Imaging Method Based On Multi - Scattering Model

Abstract

With the development of ultrasonic technology, ultrasonic wave plays an increasingly important role in the field of nondestructive testing. Among all kinds of ultrasonic nondestructive testing technologie, ultrasonic phased array is widely used because of its high accuracy and flexibility. However, due to the existence of rayleigh limit, ordinary ultrasonic phased array technology cannot recover the space frequency greater than 2K, so it is impossible to achieve the resolution less than half of the wavelengthof the super-resolution. In this paper, we introduce a method to realize super resolution imaging in multi-band phased array.In this method, the damage is detected by multiple phased arrays, and the received signals are processed by specific algorithms to obtain super-resolution imaging. The signal is excited by M exciter and then received by N receiver. The total signal can form an M*N matrix. After singular valuedecomposition of the collected signal matrix,T significant eigenvalues can be obtained. The T significant eigenvalues represent the number of injuries. The singular vector after singular value decomposition contains the information of noise space. The number of eigenvalues in the signal space is the number of damage. Using the randomness of noise subspace, special algorithm can be used to restore the spatial frequency greater than 2K to achieve super-resolution imaging.The more elements in this method, the more accurate and complicated it is. As long as the smallest value of M and N is greater than the number of injuries, each injury can be successfully distinguished under super resolution. Therefore, the appropriate number of matrix elements should be selected for different damages.