Patent ID: 7355322

Claim:
An ultrasonic transducer, comprising: a fixed electrode; a vibrating film placed opposite to a surface of the fixed electrode and having a conducting layer; a member that holds the fixed electrode and vibrating film; the fixed electrode including: a driving-use fixed electrode receiving an AC signal to drive the ultrasonic transducer at a desired amplitude, and a detecting-use fixed electrode formed to detect an amplitude of the vibrating film; and a control unit that controls the AC signal applied to the driving-use fixed electrode based on a comparison of the magnitude of the amplitude of the vibrating film detected by the detecting-use fixed electrode and the amplitude of an input signal received by the control unit so that the amplitude of the vibration of the vibrating film approximates the amplitude of the input signal, wherein when an alternating current (AC) signal is applied between the fixed electrode and the conducting layer of the vibrating film, the ultrasonic transducer generates an ultrasonic wave.