Research On The Fast Location And Recognition Of Scattering Source In Ultrasound CT Imaging By Virtual Phased Array

Recently, ultrasonic testing technology by phased array has gradually become a research hotspot of nondestructive testing at home and abroad. Ultrasonic testing technology by phased array is such a testing technique, in which dynamic focusing and high-speed scan can be carried out by controlling phase delay to ultrasonic array transducer and obtaining flexible and controllable synthesis waves. In this paper, principles of ultrasonic testing by phased array are studied theoretically and experimentally. Compared with ultrasound reflection mode CT, ultrasound transmission mode CT, ultrasonic diffraction mode CT techniques based on the linear CT theory, this paper applies a new method of nonlinear ultrasound CT to anisotropic materials, which overcomes the assumption of current linear propagation of ultrasound CT and weak scattering. This method is mainly based on each array element of phased array focused transducer that generating and receiving data respectively.This paper takes advantage of the method of space-time compression, which makes ultrasonic array signals(wave trains) received by virtual phased array transform to two-dimensional grayscale of time-location, and projects it onto time-position. According to the study of the characteristics of one-dimensional gray projection, we can identify the existence of scattering interface rapidly and confirm the rough position of signals caused by scattering interface on time axis. Based on the method above, we distinguish the signal of each interface. And we can adopt the traditional method and the wavelet transform to extract characteristics, and take them as the input target vectors of BP neural network. Through the training and learning on BP neural network, scattering sources were identified. Finally, the regional image that we emphasized is obtained through data processing software and signal analysis ,which based on the study of processing methods of the signal by virtual phased array and the characteristics of ultrasound CT imaging by phased array. The experiment result of the IIW shows that the improved method of space-time compression has been put forward in the paper is feasible and valid in the fields of fast location,recognition and imaging.