| 摘要 |
PURPOSE:To suppress error in the decision of ultrasonic propagation time difference by determining a mutual correlation function of pulses based on the pulse interval of ultrasonic multiple reflection echo. CONSTITUTION:When a measurement is made while varying the ultrasonic transmitting/receiving frequency, a mutual correlation function variable with different frequencies is obtained. The correlation function exhibits a steep peak at a point where the phases match each other and thereby propagation time difference can be determined easily. The mutual correlation functions are then stored in a correlation function memory 60 while switching the frequency of a probe 10 and correlation operation results are added at a correlation function adder 70 upon finish of measurement. |
