In this paper, at first a brief survey of ultrasonic holographic techniques is presented and as a concrete example of holographic imaging system our method which makes use of the diffraction of light by ultrasonic waves is described in detail and then the problems about the usefulness and the future of the ultrasonic holography are discussed.
The special feature of our method lies on the fact that it can provide a reconstructed image in real time without phase reference. This comes from the fact the amplitude and phase distribution of +1st order light diffracted by ultrasonic waves is proportional that of ultrasonic waves. This relation appears to be useful not only in the area of ultrasonic imaging but in the area of real-time optical processing.
Comparing the principles of ultrasonic holography with that of acoustical visualization techniques which includes pulse-echo method as well as conventional imaging method, we reach the conclusion that feature of ultrasonic holography lies on coherent data processing of detected signal. From this point of view, we discuss the practical role of ultrasonic holography and new feasibility of the ultrasonic holography, that is, coherent data processing of pulse-echo.
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