| 摘要 |
PURPOSE:To obtain the ultrasonic wave beam converged on a line, by applying electric signal having a given phase difference to the reed screen type electrodes of a plurality having uniform period. CONSTITUTION:On the surface of the piezoelectric substance 3, a plurality of reed screen type electrodes 4a, 4b, 4c,... are provided lengthwise the electrode finger, constituting the electrode group 10. The period of each read screen type electrode (distance between the electrode fingers of each phase) is made uniform and a given phase difference is given to electric signal fed to the reed screen type electrodes, then the phase of the ultrasonic wave caused is different to each electrode and the beam can be converged on the line F in parallel with the X axis as a whole. As the condition of the phase difference, taking m as an integer, omegao as angular frequency of electric signal, Vw as the sound velocity in liquid, Yn as the distance from the reference point of the n-th reed screen electrode, DELTA(Yn) as the phase of electric signal fed to the n-th reed screen type electrode, it can be achieved by satisfying the euqation -1, taking (y,x) as the coordinate. |
