| 摘要 |
<P>PROBLEM TO BE SOLVED: To provide an ultrasonic generation unit that emits an ultrasonic wave having a plane wavefront. <P>SOLUTION: In a cMUT 100, a bottom portion 120 having a disc-shaped lower electrode 122 is formed on a base plate 110, and a hollow cylindrical support portion 130 is formed on the bottom portion 120. On the support portion 130, a top portion 140 is formed that includes a ring-shaped upper electrode 142 and a nonconductive vibration mass portion 144 that is formed on a side of an axis C of the upper electrode 142. When alternating voltage is placed between the lower electrode 122 and the upper electrode 142, electrostatic attraction acts on portions where the lower and upper electrodes 122 and 142 face each other. The vibration mass portion 144 has greater rigidity, and is therefore less deformable, than other portions. Thus, the top portion 140 vibrates with an outer edge portion including the upper electrode 142 curved and a central portion including the vibration mass portion 144 maintaining a planar shape. Therefore, the cMUT 100 emits an ultrasonic wave having a plane wavefront and good directivity. <P>COPYRIGHT: (C)2012,JPO&INPIT |
