Fish finder capable of discriminating sizes of fish

• US 4,081,783 A
• Filed: 09/22/1976
• Issued: 03/28/1978
• Est. Priority Date: 09/26/1975
• Status: Expired due to Term

• Current Assignee: Keisuke Honda
• Original Assignee: Keisuke Honda
• Inventors: Honda, Keisuke
• Primary Examiner(s): Farley, Richard A.
• Application Number:
  US05/725,392
• Time in Patent Office: 552 Days
• Field of Search: 340/3 R, 340/3 F, 343/5 SA
• US Class Current: 367/101
• CPC Class Codes: F02B 2075/025 two
• CPC Class Codes: G01S 15/02 using reflection of acoustic waves G01S15/66 takes precedence
• CPC Class Codes: G01S 15/96 for locating fish

Abstract

The present invention discloses a fish finder wherein one transducer is used to generate both high- and low-frequency ultrasonic waves which are simultaneously emitted and the electrical signal representative of the reflected high- or low-frequency ultrasonic waves is extracted by the signal representative of the reflected low- or high-frequency ultrasonic waves, thereby discriminating the sizes of fish detected.

Claims

1. A fish finder capable of discriminating the sizes of fish, comprising:

a single transducer capable of transmitting and receiving high- and low-frequency ultrasonic sound waves simultaneously, one of said high- and low-frequency ultrasonic sound waves being emitted with a wide beam angle while the other of said waves is emitted with a narrow beam angle;

receivers for processing the high- and low-frequency echo signals received by said transducer,

a subtractor circuit for subtracting the received echo signal corresponding to the narrow beam angle from the received echo signal corresponding to the wide beam angle, and

a recorder for recording the output from said subtractor circuit comprising echo signals corresponding to images of fish of desired size.

2. A fish finder as set forth in claim 1 wherein the high-frequency ultrasonic sound waves are emitted at a narrow beam angle while the low-frequency ultrasonic waves are emitted at a wide beam angle;

and the reflected low-frequency ultrasonic sound waves are subtracted from the reflected high-frequency ultrasonic sound waves, thereby discriminating individual fish and schools of fish of small size.

3. A fish finder capable of discriminating the sizes of fish, comprising:

a single transducer capable of transmitting and receiving high- and low-frequency ultrasonic sound waves simultaneously,

receivers for processing the high- and low-frequency signals received by said transducer,

a subtractor circuit for subtracting one of said received high- and low-frequency signals from the other of said signals,

means for determining when the received low-frequency signal has an amplitude exceeding a predetermined threshold value, and for thereupon detecting and differentiating said received signal and adding the resulting detected and differentiated signal to the output of the subtractor circuit to provide a signal enhancing the sea bottom, and

a recorder for recording said enhanced signal.