| 摘要 |
PROBLEM TO BE SOLVED: To provide an ultrasonic wave detector for adjusting a driving frequency of a transmission side ultrasonic wave sensor by feedback control in a paper feeder. SOLUTION: This paper feeder has the ultrasonic wave detector 1 for detecting a double feed by using an ultrasonic wave. The ultrasonic wave detector 1 has the transmission side ultrasonic wave sensor 17, a driving IC 13 for supplying a driving signal to the transmission side ultrasonic wave sensor 17, a reception side ultrasonic wave sensor 18 oppositely arranged by sandwiching a carrying passage in the transmission side ultrasonic wave sensor 17 and the paper feeder and control means 11, 12 and 16 for controlling the driving IC 13 so that the driving frequency of a driving signal matches to a resonance frequency of the transmission side ultrasonic wave sensor 17 based on an ultrasonic wave received by the reception side ultrasonic wave sensor 18. COPYRIGHT: (C)2004,JPO
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