Synthetic Aperture Focusing Technique Used In Ultrasonic Phased Array

Synthetic aperture focusing technique(SAFT) is one of approach to ultrasound imaging data, which can be synthesized in a larger aperture with a small aperture, and the resolution does not vary with depth and location. It can simplify the hardware system effectively, too. With the title “SAFT used in ultrasonic phased array”, the thesis studies the fundamental principle of ultrasonic phased array, and focuses on the implement of SAFT in time domain and frequency domain. Which may offer a new project for phase array detection, also has practical significance for academic value and reference in application and improvement by SAFT. The research has been supported by the national major scientific instrument and equipment development special(No. 2013YQ230575) funded.This paper analyses the basic principle of phased array synthetic aperture imaging, and the simulation model was established in the time domain and frequency domain respectively, presents the applications of correlation analysis of SAFT and RDA.finally, a simulation software was make to realize algorithms simulation.research work includes several aspects as follow:(1) The basic principles of ultrasound phased array work is describe, the same as simulation model of the ultrasonic field. Sound pressure distribution was research on axis and surface respectively. What is more, an orthogonal experimental was designed to obtain the best combination of factors, which affect the distribution of sound pressure. The coordinate transformation technology for digital imaging also be conduct, including neighbor interpolation, bilinear interpolation and cubic linear interpolation algorithm. Finally, an improvement interpolation algorithm based on linear interpolation was found to filled pixels.(2) According to the transmitting and receiving signals have a good correlation, we put forward a advanced algorithm based on correlation analysis, combining with the wave packet decomposition theory.using the decomposition coefficient come from decomposition,detector can judge defects,witch expand the scope of application of SAFT; the advanced algorithm has higher resolution compared with the traditional.(3) The paper also present the fundamental principle of code excitation using in ultrasonic, and focus on encoding and decoding technology includeing: pulse compression, the range migration correction(RCMC). Finally, a multi point defects simulation was found to imitate the process of encoding and decoding.(4) Basing on all the algorithms mentioned above, three GUI interfaces have been developed: real data display and processing, sound field and inspect simulation based on field II, R-D algorithm simulated. Showing and processing real data can be done by the software, appending Filed II simulation.Experiment prove that SFAT based on correlation analysis and R-D algorithm can quickly produce focusing imaging with a satisfactory resolution.