| 摘要 |
PURPOSE:To effectively correct the attenuation of the echo signal dependent on frequencies regardless of the difference in the acoustic characteristics with each part of the testee bodies by detecting the attenuation characteristics of ultrasonic waves in accordance with the actual echo signal from an ultrasonic vibrator, controlling the oscillation frequency of a variable frequency oscillation means in accordance therewith an subjecting the echo signal to frequency conversion. CONSTITUTION:The output signal of a BPF 7 is supplied to an A/D converter 40 as well by which the signal is converted to a digital signal. This signal is stored into a memory 41. The reception signal read out of the memory 41 is subjected to FFT computation in a microcomputer 43 of an FFT processing section 42 and is converted to the data corresponding to a central frequency. This data is stored into a memory 44. The data of the central frequency corresponding to this ultrasonic sound ray is read out by a reading out control circuit 45 and is converted to an analog voltage signal by a D/A converter 46. The oscillation frequency of a VCO 30 is controllable according to the ultrasonic attenuation characteristic of a testee body if the oscillation frequency of the VCO 30 of a DC-AC detection section 8 is controlled in accordance with this analog voltage signal. The effective correction of the attenuation of the received echo signal which depends on the frequency is, therefore, possible regardless of the difference in the acoustic characteristics with each of the testee bodies and the always highest pulse compression effect is obtd. |
