基于FPGA的超声动态聚焦延时参数压缩算法  

Time Delay Parameter Compression Algorithm of Ultrasonic Dynamic Focusing Based on FPGA

作　　者：王平[1] 梁家祺 WANG Ping;LIANG Jiaqi(School of Electrical Engineering,Chongqing University,Chongqing 400044,China)

机构地区：[1]重庆大学电气工程学院,重庆400044

出　　处：《电声技术》2022年第3期59-66,共8页Audio Engineering

摘　　要：超声成像是一种被广泛使用的无损检测手段,超声聚焦是超声成像的重要环节,延时叠加算法是超声聚焦最基础的波束形成算法。为了得到更好的成像质量,焦点随探测深度变化而变化的动态聚焦方法逐渐取代了传统的定点聚焦方法,然而该方法在现场可编程逻辑门阵列(Field Programmable Gate Array,FPGA)的实现中遇到了聚焦延时参数数据量过于庞大的问题,使得现有的实现方案只能采用传统的定点聚焦方法。为了解决这个问题,提出一种基于误差约束的超声延时参数压缩算法,通过对探测区间进行分段,将动态聚焦中聚焦延时参数相近的焦点分为一段,用统一的聚焦延时参数代表该段区间所有焦点的聚焦延时参数,靠算法将统一参数和实际参数的误差值约束在一定范围内,对原来的聚焦延时参数进行压缩处理,在文章例子中压缩比达到了2.548‰。为了减小近场的盲区,算法引入了动态孔径技术,在近场聚焦时关闭部分外侧阵元,随着聚焦深度增加,阵元逐渐恢复开启直到所有阵元都恢复开启。使用动态孔径技术后,未开启阵元的聚焦延时参数便成为无用的冗余数据,鉴于此,在新提出的结合动态孔径的超声延时参数压缩算法中对聚焦延时参数的数据量进一步压缩,压缩比达到了0.717‰,有效缓解了聚焦延时参数的存储压力。Ultrasonic imaging is a widely used nondestructive testing method. Ultrasonic focusing is an important part of ultrasonic imaging. Delay and Sum(DAS) is the most basic beamforming algorithm in ultrasonic focusing. In order to obtain better imaging quality,the dynamic focusing with the change of focus with the detection depth replaces the traditional fixed-point focusing. However, this method encounters the problem of too large amount of focus delay parameter data in the implementation of Field Programmable Gate Array(FPGA), so that the existing implementation schemes can only use the traditional fixed-point focusing. In order to solve this problem, an ultrasonic delay parameter compression algorithm based on error constraint is proposed in this paper. By segmenting the detection interval, the focus with similar focus delay parameters in dynamic focusing is divided into one segment, and the unified focus delay parameters represent the focus delay parameters of all focus in this segment, the error values of the unified parameters and the actual parameters are constrained within a certain range by the algorithm, and the original focusing delay parameters are compressed. In the example of the article, the compression ratio reaches 2.548‰. In order to reduce the near-field blind area, the dynamic aperture technology is introduced into the algorithm. When focusing in the near-field, some outer array elements are closed. With the increase of focusing depth, the array elements gradually return to open until all array elements return to open. After using the dynamic aperture technology, the focusing delay parameters of the array element without opening become useless redundant data. In view of this,in the newly proposed ultrasonic delay parameter compression algorithm combined with dynamic aperture, the data amount of focusing delay parameters is further compressed, and the compression ratio reaches 0.717‰, which effectively alleviates the storage pressure of focusing delay parameters.

关 键 词：现场可编程逻辑门阵列(FPGA) 超声成像 动态聚焦 数据压缩 

分 类 号：TN912[电子电信—通信与信息系统]