Research Of Phased Array Ultra-Sonic Imaging Optimization

Ultrasonic testing technology is widely used in medical ultrasound, transportation, pressure vessel etc. It is characteristic of the ultrasonic phased array, such as good ability to control beam, high sensitivity and large detection range. The synthetic aperture technique is a kind of post processing technology, which can make the synthesis of large aperture with small aperture, form the focusing signal to improve the imaging quality and it has the char-acteristics that the azimuth resolution is independent of detection depth and the working wavelength. With the increasing demand of testing, the routine ultrasonic phased array de-tection can’t meet the need, so a method combining the synthetic aperture technique and ul-trasonic phased array has become the hot spot of research.In this thesis, in order to improve the quality, two kinds of window function will be used as the optimization factors, which are the direction of arrival of window function (DOA) and radiation of far field approximation of window function, respectively. And a comparative study of phased array ultrasonic focusing model with and without optimization, and analyz-ing the characteristics of phased array beam, verified by experiments.Based on Field Ⅱ, the SF model is simulated and the imaging is verified by the simula-tion experiment. Following, analyzed the model of DAS and SF, formed the beam, and in-troduced the direction of arrival of window function and radiation of far field approxima-tion of window function. It’s clear that the optimization with DOA is best to suppress side lobe with peak dropped to -100dB and the other window is the second to -89dB in experi-ments and analysis.Finally, simulations based on Field Ⅱ and experiments based on Multi2000 of M2M about the two windows of DOA and radiation of far field approximation of window function will be done. The results show that these two kinds of optimization methods had improved the imaging depth of phase array ultrasonic imaging with synthetic focusing method. And compared with conventional SF method, the method optimized with DOA increased the de-tection rate, up to 92%. The results of the actual size of defects using the radiation of far field approximation window function optimization are more accurate, and the maximum er-ror of the defect size decreased from 67.53% to 21.37%.