| 摘要 |
<P>PROBLEM TO BE SOLVED: To determine an output to acquire a desired level of an ultrasonic element in a short time. <P>SOLUTION: When ultrasonic wave transmission starts with the drive of the ultrasonic wave transmission element (S201), an absolute value of a difference between a drive frequency (transmission signal) output from a frequency modulation circuit and a frequency of the final received signal input from a frequency recognition circuit is compared with a preset allowable error α (S202), when the frequency difference is equal to or exceeding the allowable error α, the drive frequency is compared with the frequency of the final received signal (S203), when the drive frequency is smaller than the frequency of the final received signal, the drive frequency is increased by Δf (S204), on the other hand, when the drive frequency is equal to or larger than the frequency of the final received signal, the drive frequency is reduced by Δf (S205), further, the drive frequency is compared with the frequency of the final received signal, and when the absolute value of the difference between the both becomes smaller than the allowable error α, the double-feed detection is performed (S206). <P>COPYRIGHT: (C)2012,JPO&INPIT |
