CHARACTERISTICS MEASURING APPARATUS FOR ULTRASONIC VIBRATION DETECTING SENSOR

PURPOSE:To enable the measurement of characteristics of a sensor for ultrasonic wave detection at a high accuracy free from the effect of characteristics of an ultrasonic wave generator, by controlling a driving circuit with a laser sensor so that the displacement of the sensor for detecting ultrasonic waves reaches a desired value. CONSTITUTION:A sensor 4 for detecting ultrasonic vibration is put tightly on an ultrasonic wave generating surface 2 of an ultrasonic wave generator 1. On the other hand, in a laser sensor 5, a laser beam R is divided into two, a part R1 thereof is directed onto the sensor 4 and the reflected light R3 is introduced to a beam splitter 10. The other part R2 thereof is sent to an acoustic modulator 11 to shift the frequency thereof. The beam merged and interfered with the beam R3 in the beam splitter 10 and after converted 15 into an electrical signal, it is sent to a demodulator 17 to output a vibration waveform of the sensor 4. A control circuit 18 controls an ultrasonic wave generator driving circuit 3 on the basis of an output of the sensor 5 so that displacement of the sensor 4 reaches a desired value, and then the generator 1 is driven. An electric output of the sensor 4 is measured with a characteristics measuring device 19 and thus, frequency characteristic of the sensor 4 is obtained by varying the frequency of the measuring device 19.