合成孔径(SA)波束形成方法可以实现发射和接收的双向动态聚焦,有效提高成像分辨率,在多阵元相控阵超声内镜系统中有着广泛的应用前景。但由于其单阵元发射能量小,使得回波信号较弱、易受噪声干扰,导致图像的信噪比(SNR)较差。为此,提出一种新的成像算法,将以线性调频信号为载波的巴克码(Barker码)激励方法与合成孔径波束形成方法相结合(LFM Barker SA),利用线性调频信号的宽带特性和Barker编码的自相关特性来弥补合成孔径方法在成像SNR上的不足,同时进一步提升图像的分辨率。经FieldⅡ软件仿真实验表明,与单脉冲激励的合成孔径(Pulse SA)算法相比,LFM Barker SA算法下的图像SNR提升10 dB,轴向分辨率从0.60 mm提升至0.38 mm,实验结果验证了该算法的可行性。

The synthetic aperture (SA) beam forming can realize bidirectional dynamic focusing in both transmission and receiving, so it improves the imaging resolution effectively and will be widely used in the multi-element phased array ultrasonic endoscope system. However, because of the low transmission energy of the single element, the echo signals are weak and could be influenced by noise easily, thus the signal-noise ratio (SNR) of the image is relatively poor. A new imaging algorithm is proposed, which combines the Barker coded excitation using the linear frequency modulated carrier with the synthetic aperture beam forming (LFM Barker SA). The broadband of linear frequency modulated signal and the autocorrelation of Barker can remedy the SNR of synthetic aperture beam forming, and the proposed algorithm improves the imaging resolution further. The simulation results with FieldⅡ software show that the LFM Barker SA algorithm improves the SNR about 10 dB and increases the axial resolution from 0.60 mm to 0.38 mm, compared with the Pulse SA algorithm. The experimental result verifies the feasibility of this algorithm.