| 摘要 |
PURPOSE:To decide the sort of fish based upon the display of the outline of a target and the display of a level difference and to grasp the density or the like of the target with a certain probability by using pulses having different pulse width each other as ultrasonic pulses having high and low frequency levels and controlling the overlap of receiving pulse signals. CONSTITUTION:A pulse having a prescribed width t1 is transmitted from a pulse generating difficult 3 to form a high frequency pulse. On the other hand, a pulse having a prescribed width t2 is generated from a circuit 6 after being delayed by a short period t0 through a delay circuit 5 to from a low frequency pulse by an oscillation circuit 7. In receiving signals sent from the same target, the pulse width t2 is overlapped to the approximately center of the pulse width t1. The period superposed at the extraction of the difference between both the pulses is outputted as a difference level through a subtractor 12 and a level/color conversion circuit 13 and the leading edge E1 and trailing edge E2 of the pulse t1 are left as they are. Consequently, the outline of the signal can be displayed and the sort of the fish can be also decided. |
