| 摘要 |
<P>PROBLEM TO BE SOLVED: To provide an ultrasonic device in which ultrasonic waves of a plurality of frequencies can be transmitted or received by a single element and the element is easy to design. <P>SOLUTION: An ultrasonic device includes: a piezoelectric element which constitutes a transmitting element and a receiving element and vibrates in a thickness direction and of which the acoustic impedance is Z1; an acoustic member of which the acoustic impedance is Z2 smaller than that of the piezoelectric element; drive signal generating means which generates a drive signal of a predetermined frequency for vibrating the transmitting element; and change means for instructing the drive signal generating means to change the frequency of the drive signal in accordance with a preset switching condition. The drive signal generating means is then provided to generate a plurality of drive signals of which the frequencies are different from each other in such a manner that the single transmitting element transmits and the single receiving element receives a plurality of ultrasonic waves of which the wavelengths are different from each other, meeting λ=4×Ta/(2n-1) ((n) is a positive integer, λn is a wavelength at a time when an ultrasonic wave of a frequency fn is propagated inside the acoustic member), when a thickness of the acoustic member is defined as Ta. <P>COPYRIGHT: (C)2012,JPO&INPIT |
