Ultrasonic Real-time Imaging Using Acoustic Fourier Transform

本研究的目的是1.开发了利用超声波对被检体进行傅立叶变换（Acoustic Fourier Transform），并在计算机上通过快速傅立叶逆变换进行重建的新方法.为了验证该方法的可行性，对光学法透明的玻璃、不锈钢以及火焰、泥浆、雾中的物体进行了实验重建，制作了反射式声傅里叶变换系统。发射接收器阵列的前端布置有目标和参考源，发射接收器阵列在一个发射器的圆周上布置有多个接收器。这里，这些元件被布置成使得它们可以在相同的周界上。然后，通过参考波和来自物体的反射波（物体波）的干涉，可以在接收器阵列处获得物体的傅立叶变换。此外，该方法还决定用计算机产生的参考信号电加到电路上，代替在目标附近设置一个参考源。该系统采用脉冲回波法测量物体的距离，自动调焦，调节计算机产生的参考信号的延迟量，并以丙烯酸纤维制成的物体（几何简单图形、字母字符）为例进行了光学透明物体的重建，以烟雾中的物体为例进行了最终环境下物体的重建。实验结果表明，该方法能够有效地重建出物体的轮廓，并验证了该方法的有效性。我们可以在大约20秒内完成所有的处理，使用个人电脑的CPU的奔腾133兆赫。

The purpose of this research is1. Development of the new method that performs Fourier Transform of the object by the ultrasound (Acoustic Fourier Transform) and reconstructs the object by Inverse Fast Fourier Transform in the computer.2. Experiment of reconstructionabout the glass, the stainless steel, which are transparent by the optical method, and the object in the flame, the mud, the mist, which is called the ultimated environment, for the verification of this method.We made the reflection type Acoustic Fourier Transform system. An object and a reference source are arranged in the front of the transmitter-receiver array which arranged many receivers in the circumference of one transmitter. Here, these elements are arranged sot that they may be on the same perimeter. Then, Fourier Transform of the object can be obtained at the receiver array by interference of the reference wave and the reflection wave from the object (the object wave). Moreover, in this method, it was decided with the system that the reference signal made in the computer was electrically added on the circuit for the substitute of arranging a reference source in the neighborhood of the object. And, automatical focusing, which measured a distance to the object by the pulse echo method, was included to adjust the delay quantity of the reference signal made in the computer.Using this system, we reconstructed the object (geometrical easy figures, alphabet characters) made of the acrylic fiber as an example of the optical transparent object, and the object in the smoke as an example of the object under the ultimated environment. As a result, each object was reconstructed sufficiently, and the validity of this method was confirmed. We could perform all of the processing in about 20 seconds using the personal computer which had the CPU of Pentium 133MHz.