| 摘要 |
PURPOSE:To facilitate an easy manufacture of the high molecular piezoelectric substance and at the same time reduce the variance of the performance property of each ring, by securing an uneven high molecular piezoelectric substance and also setting the head between the convex and concave areas to lambda/2 substantially (lambda: lenght of ultrasonic wave with using frequency). CONSTITUTION:The back electrodes/reflecting plates 2 the concentric ring parts 2a-2d of which are convex and concave to each other in their forms are laminated on the upper surface of the supporter 1, and furthermore the high molecular piezoelectric substance film 3 and the surface electrode 4 are laminated successively to adhere close to the convex and concave areas of the plate 2. The head between the convex and concave areas of the electrode 4, i.e., the difference between the codes T and B in the figure is set substantially to 1/2 the sound wavelength lambda in the propagation medium and with the using frequency. As a result, the difference lambda can be secured for the distance to the focus O of the adjacent ring to give a shift equivalent to one wavelength. Thus a mutual strengthening is secured for the sound waves at the focus O even though the electrodes may be driven in the same phase. In addition, the electrodes in series will do with no split. As a result, the manufacture can be facilitated for the high molecular piezoelectric substance, at the same time reducing the variance among the rings. |
