Ultrasonic Real-time Imaging Using Acoustic Fourier Transform

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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.