| 摘要 |
PURPOSE:To obtain the same effect as done by the reduction in the wave transmission time, by performing a wave transmission with the second frequency during the trailing period immediately after the wave transmission with the first frequency. CONSTITUTION:A trigger pulse generation circuit 1 outputs a pulse (a) with the pulse width t1 and the same pulse (c) after (t1+dt) thereof. Two oscillation circuits 2 with the respective oscillation frequencies of f1 and f2 perform oscillation separately with the frequencies of f1 and f2 based on the pulses (a) and (c) during the period of transmission thereof. An oscillator 3 having the resonance frequencies f1 and f2 is excited by an oscillation signal to transmit ultrasonic waves sequentially. Receiving circuits 4 and 5 has a filter for separating the reflected wave from a target object as inputted through the oscillator 3 and displays 6 signals of various frequency signals according to a desired display pattern. With such an arrangement, when the tailing (damping oscillation) period is represented by t2 with dt<<t2-dt<t2, the time necessary for the transmission can be reduced roughly by the trailing time t2 as compared with the necessary time 2(t1+t2) for the normal second transmission.
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