Research And Implementation Of Two-dimensional Ultrasound Imaging System Based On Sparse Array

Ultrasound imaging for its safe, fast, convenient and harmless characteristics, is widely used in medical detection and industrial inspection, and provides great convenience for the detection and diagnosis of lesions of products. Conventional ultrasound imaging systems mostly use multiple scans of the transmit receive mode, imaging frame rate is low, also in order to improve the imaging quality and array element number is needed to increased, which increases the cost of the system. In this paper, in order to reduce the complexity of simplified imaging system the system cost and improve the system of imaging frame rate for the purpose of realizing two-dimensional sparse array imaging, at the same time, the hardware system of sparse ultrasound imaging is also designed.This paper first introduces the composition of new ultrasonic imaging system, in which ultrasonic transducer array arrangement, the transmit signal selection, channel separation method and final imaging methods were summarized in this paper, based on Gold code modulation and linear frequency modulation wave and sparse array of BP artifacts elimination imaging method, in this paper, the FPGA is also designed as the control core of the 16 channel sparse array ultrasound imaging front-end system hardware circuit.On the traditional system, Receiving and sending focus makes the imaging rate become very slow. In this paper a sensor array and emission orthogonal signal is used and, simultaneously and independently receive array element receives the echo signal of transmitting and receiving, combined with subsequent channel separation technology can be through a closed time data required to complete the imaging. Eight emission array element and eight receiving array elements, through the array optimization can be virtualized 64 space with a virtual array, which are through the perf 16 element array rational allocation of 64 element array performance by sparse transducer array. Channel separation technology needs to transmit the signal with good orthogonality, so the combination of Gold code and linear frequency modulation signal has a good self correlation and cross correlation characteristics.Based on the analysis of the traditional B scan imaging method, this paper proposes a BP imaging algorithm which is suitable for sparse array. BP imaging algorithm can effectively present the real information of the target when the target point is less, and the image will become stronger with the increase of the target point. In this paper, through the analysis of the process of BP algorithm, it is concluded that the imaging artifacts are generated by multiple targets arc superimposed, and at the same time, the scattering intensity of different targets can also increase the artifacts. In order to solve the imaging artifact problem, this thesis, by means of imaging threshold judgment on the overall system, combined with imaging channel channel number of the threshold to judge, two judgments is used to eliminate the influence of artifacts of imaging, the imaging simulation by Jason's body membrane model, indicating the validity of the imaging algorithms.Based on the study of sparse array imaging key technology, this paper also introduce the hardware design and the sparse array imaging system. Sparse array ultrasonic imaging front-end system consists of FPGA main control module, H bridge power amplifier module, LPF (Low Pass Filter) module, USB communication module, receiving module, transformer and transducer components. At the same time on the actual hardware system for signal emission test, receiver channel echo test and TGC module gain change detection, let the follow-up system for more complex signal processing system.