| 摘要 |
PROBLEM TO BE SOLVED: To provide a push-pull-type electrostatic ultrasonic transducer with an aim for improving the electro-acoustic energy conversion efficiency. SOLUTION: A push-pull-type electrostatic ultrasonic transducer includes a first electrode 10A, having a through hole 14, a second electrode 10B having a through hole forming a pair with the through hole of the first electrode, and a vibration film 12 held between a pair of electrodes composed of the first and the second electrodes and having a conductive layer 121 to which a direct-current bias voltage is applied, and holds the pair of electrodes and the vibration film. Ifλis the wavelength of the carrier wave, having a frequency shifted as a predetermined amount of frequency from the resonance frequency, which is the mechanical resonance frequency of the vibration film, thickness (t) of each of the pair of electrodes is set to (λ/4)×n or roughly (λ/4)×n (whereλis the wavelength of the ultrasonic wave, (n) is a positive odd number), and an alternating-current signal, which is a modulated wave, obtained by modulating the carrier wave in the ultrasonic frequency band with a signal wave in an audible frequency band, is applied between the pair of electrodes. COPYRIGHT: (C)2007,JPO&INPIT |
