A New Ultrasonic Imaging System by Using a Rotating Random Phase Disk and Power Spectral and Third Order Correlation Analysis
A new ultrasonic imaging system which uses neither scanning of a receiver nor beam forming by a phased array is presented. The fundamental idea is the transformation of the spatial distribution of wave intensity, which is the object to be reconstructed as the image, into temporal information by using a rotating random phase disk placed just behind the object and the analyses of the signal detected by a fixed receiver placed far from the disk. It is shown that the power spectrum of the signal is the shadow of the object on the plane which includes the point detector and the plane parallel to the object plane. Moreover if the 3rd order correlation function of the signal is calculated, this value gives directly the required reconstructed image of the object, provided that a point source is placed near the obj ect. A complete system with random phase disk made of acryl and operating at 3 MHz with FFT algorithm of a mini-computer is constructed. The theoretical discussions by using spectral representation of the wave field and resolution analyses as well as reconstructed images are presented. Although most of the results have been submitted as papers in JASA, Refs. 1 and 2, comprehensive discussions are given in this article.
KeywordsWave Field Ultrasonic Wave Random Phase Object Plane Power Spectrum Analysis
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