The Application of the Phase Method in Visualizing Ultrasonic Waves

概要

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Ultrasonic waves propagating in a transparent medium can be considered optically as a sort of phase grating. Therefore, the method of phase microscopy may be applied to the image formation of ultrasonic waves. We have studied theoretically and experimentally the application of the phase method in visualizing ultrasonic waves and confirmed the effect of the method for the improvement of the visibility of the image. In the usual Schlieren method for visualizing ultrasonic waves, the zeroth order diffraction image is perfectly screened, while in our method the image receives a proper absorption and phase retardation by the phase plate placed in the diffraction plane. According to the theoretical calculations, the phase retardation for the maxium visibility of the image of progressive waves with the stroboscopic illumination is $\pi/2$ and the optimum absorption varies with the intensity of the waves. In both cases of the usual method and the present phase method, the theoretical curves are compared with the experimental results, showing a considerable agreement between them. Further, the fine structures in the images are seen with the increase of sound intensity.
INSTITUTE OF PURE AND APPLIED PHYSICSの論文
1953-01-25