| 摘要 |
PURPOSE: To measure the distance to an object without receiving any influence of the amplitude of received signals by outputting transmitting signals containing a phase modulating point after converting the signals into ultrasonic waves, by finding the distance based on the time from the transmission of the transmitting signals to the reception of the phase modulating point of the received signals composed of reflected waves, and then, by changing the amplification degree of a reception circuit in accordance with the amplitude of the received signals. CONSTITUTION: A transmitting circuit section 12 outputs transmitting signals (a) containing a phase modulating point (x) and an ultrasonic transducer 86 converts the signals (a) into ultrasonic waves U. The waves U are reflected by an object 84 to be measured and return to the transducer 86 and the transducer 86 converts the waves U into received signals (b) and supplies the signals (b) to a reception circuit section 14. A time measuring section 16 measures the time (t) from the outputting timing of the signals (a) from the section 12 to the inputting timing of the point (x) of the signals (b) to the section 14. A distance calculating section 18 finds the distance D between the transducer 86 and the object D from D=(t×v)/2 (where, v is the acoustic velocity). A variable gain adjusting section 191 adjusts the amplification degree A of the section 14 in accordance with the amplitude of the signals (b). Therefore, the influence of the magnitude of the amplitude of the signal (b) can be eliminated.
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