PURPOSE: To provide a fish detection side-looking sonar relatively inexpensive and capable of searching for such a kind of fish as distributed in the relatively shallow sea. ;CONSTITUTION: Three to six ultrasonic echo sounder transducers la to 1d are mounted on a shaft rotated with a revolving motor M, with ultrasonic transmission directions kept different by θ/n, where θ is an angle between 180 and 160 degrees, and 'n' stands for the number of ultrasonic echo sounder transducers. Then, the motor M is driven and each of the transducers 1a to 1d on the shaft is rotated by θ/n at every preset angle. An ultrasonic wave is transmitted from each of the transducers 1a to 1d in the direction of a cross sectional area across a ship at each angle, and each reflected wave is received. Then, the reflected wave so received is processed in a signal processing section on board the ship, and the distribution of an object such as fish along the ship's right and left directions as well as the ship's downward direction is shown on a display means such as CRT.;COPYRIGHT: (C)1996,JPO
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