Patent ID: 8583381

Claim:
An ultrasonic propagation time measurement system, comprising: an electromagnetic wave transmission unit which sends out an electromagnetic wave signal indicative of transmission timing; a unit which generates an ultrasonic driving signal by modulating ultrasonic based on a pseudo random signal whose self-correlativity is high simultaneously with sending of said electromagnetic wave signal; an ultrasonic transmission unit which sends out an ultrasonic signal driven by the ultrasonic driving signal; an electromagnetic wave reception unit which detects said electromagnetic wave signal; an ultrasonic reception unit including an ultrasonic detection unit which detects said ultrasonic signal sent, an amplification unit for a signal detected by said ultrasonic detection unit, a filtering unit for a signal passed through said amplification unit and a unit which converts a signal passed through said filtering unit into a digital signal; a frequency determination unit having an FFT or equivalent function for a digital signal generated by said ultrasonic reception unit; a band attenuation filtering unit which attenuates, centered around a digital signal frequency determined by said frequency determination unit, only a frequency band of a detected ultrasonic signal determined in advance by attenuation determined in advance; and a data processing unit which calculates, with the same waveform as a waveform of said ultrasonic driving signal as a model waveform, a value of correlation between an ultrasonic signal outputted from said band attenuation filtering unit and the model waveform and detects a main peak of the calculated correlation value to calculate an ultrasonic propagation time from a time of detection of said electromagnetic wave signal and a time point of detection of the main peak.