为了验证三角形和四边形准则的二值逻辑反投影(Binary Logic Back Projection,BLBP)算法在超声层析成像重建过程中的可行性,以超声层析成像的重建区域中同时含有圆柱形和椭圆柱形障碍物为例,利用COMSOL对成像区域内存在障碍物的声场进行仿真,得到声场声压分布。然后,通过提取和处理所获取的声压分布,获得信号矩阵。最后,将信号矩阵代入二值逻辑反投影算法进行图像重建。仿真结果表明:当入射波的波长λ远小于障碍物的尺寸时,声衍射的现象并不明显。重建结果表明:两种准则在几何近似理论下可行,且四边形准则的效果优于三角形准则。
In order to verify the feasibility of the Binary Logic Back Projection(BLBP) algorithm of triangular and quadrilateral criteria in ultrasonic tomography reconstruction, a typical UPT reconstruction area, which simultaneously contains a cylindrical obstacle and an elliptic cylindrical obstacle, is taken as an example. COMSOL is used to make simulation of sound field when the obstacles exist, and an acoustic pressure distribution is obtained. Then, by extracting and processing the obtained sound pressure distribution, a signal matrix is formed. Finally, the signal matrix is substituted into the binary logic back projection algorithm for image reconstruction. It could be clearly observed that the effect of diffraction is insignificant from the computation results when the wavelength of the incident wave is smaller than the size of the obstacle. The reconstruction results show that the two criteria are feasible under the geometric acoustic, and the reconstructed quality of the quadrilateral criterion is better than that of the triangular one.