| 摘要 |
PURPOSE:To widen the band of an ultrasonic wave easily with high precision by setting the pulse width of at least one of burst waves consisting of a pulse group for exciting and driving applied to the piezoelectric element of a transducer different from others. CONSTITUTION:A pulse transmitting circuit 6 transmits a burst signal S1 consisting of a pulse group responding to the control signal of a circuit 14. The pulse width of this wave S1 is set different with time; t1>Tp>t2,t3=t4= Tp, and t5<Tp (Tp: the half period of the natural frequency of an ultrasonic wave determined by shape and thickness of the piezoelectric element), where t1-t5 are the pulse width varying from the beginning of the transmission successively. The width t1 is made longer than oscillation Tp to oscillate the piezoelectric element and give inertia, the width t2 is shortened to increase the frequency and excite and drive oscillation with the same widths t3 and t4 with the oscillation Tp, and the width t5 is shortened to provide dumping effect. Consequently, the frequency component of the ultrasonic wave is widened in band to reduce trailing of the ultrasonic wave. Thus, excellent picture quality is obtained from the shallow part to the deep part of an object. |
