抄録
Theoretical calculations are performed on the image formations of superposed ultrasonic waves. Instead of the usual method developed by Hiedemann and others for visualizing ultrasonic waves, the more general phase method are applied to the visualization. In this method, the zeroth order diffraction image subjects a proper absorption and a phase retardation by the phase plate placed in the diffraction plane, instead of being perfectly screened. From the expressions for the image formation, the image shapes are obtained, and the relation between the visibility of the images and the characteristics of the phase plate is investigated. As to the image formation of surperposed ultrasonic waves, Willard discussed the case in his paper, "Improved Methods for Measuring Ultrasonic Velocity", but it is shown that appreciable errors occur from his simple consideration with the increase of sound intensity in comparison with the present exact theory. This matter will be experimentally verified in the next report.
