| 摘要 |
PROBLEM TO BE SOLVED: To provide a sonar and an underwater detection method which enable a reduction of a bad influence owing to an ultrasonic wave transmitted from a sonar of another vessel. SOLUTION: A cylindrical transducer 1 is divided into twelve regions A1-A12 and keeps a plurality of unillustrated vibrators arranged circumferentially on the surface at equal intervals. In a certain detection cycle as shown in (a), a vibrator in each region A1-A12 is driven respectively by a signal of a frequency f1-f12 different by azimuths, and an ultrasonic wave of the frequency f1-f12 is transmitted in each azimuth D1-D12. In an ultrasonic wave receiving period, a frequency is selected for each azimuth D1-D12 differently, and a reception beam B1-B12 having a directivity principal axis in each azimuth D1-D12 is repeatedly formed. By analyzing each reception beam B1-B12, a shoal of fish or the like is detected. In the next detection cycle as shown in (b), frequencies f1-f12 different by azimuths are allotted to the regions A1-A12 in another mode different from (a). COPYRIGHT: (C)2006,JPO&NCIPI
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