JPH0321500Y2 - - Google Patents

Description

[Detailed Description of the Invention] (Industrial Field of Application) The present invention relates to a device that processes ultrasonic echoes reflected from a fish to display the length of the fish.

(Prior art) Fish finders are well known, which emit ultrasonic waves into the sea from an ultrasonic transducer installed on the side or bottom of a fish boat, process the echoes from fish schools, and display fish school information. It is. The use of this fish finder makes it easy to detect and track fish schools in the sea, but it has been impossible to measure fish body length.

(Problem to be solved by the invention) As mentioned above, with conventional devices, it is impossible to measure the body length of a school of fish, so even if a school of fish is detected, it is difficult to judge whether or not to capture the school of fish. Hard to reach. For this reason, fishing nets are often cast on schools of small-sized fish that are not targeted for fishing, and in such cases, the nets become clogged with fish, making it extremely troublesome to remove them. There was a problem that I had to work on.

This invention was made in order to solve the above-mentioned conventional problems, and its purpose is to easily determine the body length of a school of fish, thereby making it possible to reliably judge whether or not it is appropriate to catch a school of fish. An object of the present invention is to provide a body length display device.

(Means for solving the problems) In order to achieve the above object, the present invention is configured as follows. In other words, the present invention consists of an ultrasonic transducer that emits ultrasonic waves into the water, receives echoes from fish, converts the received ultrasonic signals into electrical signals, and outputs them; A propagation attenuation correction circuit that corrects the amount of propagation attenuation so that the amplitude of the echo output signal from a single fish is constant regardless of the depth, and the output signal from the propagation attenuation correction circuit is added to the output signal from the wave transmitter. This is a fish length display device that includes a calculator that calculates the fish length and a display that displays the fish length based on the calculated value of the calculator.

(Function) In the present invention having the above configuration, the fish length is displayed on the display as follows. First of all, regarding the species of fish in a school, it is rare for different species of fish to be mixed together, and it is usually a single species that forms a school, and it is almost certain based on water temperature, season, area, records of fish finders, etc. You can make a judgment based on that.

The ultrasonic waves emitted from the transducer into the water are reflected along the entire length of the fish, and the reflected waves (echoes) are received by the ultrasonic transducer and converted into electrical signals. In this case, assuming that there is no attenuation in the ultrasonic waves propagating in water, the reflection level of the reflected wave at the reception position matches the complete reflection level at the reflection position near the fish.

However, in reality, the propagation of ultrasonic waves in water is attenuated, so the level of the reflected waves at the receiving position differs depending on the depth of the fish, even if the length of the fish is the same. Therefore,
In the present invention, the propagation attenuation of the reflected wave is corrected by the propagation attenuation correction circuit so that the same reflection level is obtained for the same fish body length even if the depth is different.

Then, the arithmetic circuit calculates the fish body length based on the corrected signal, and adds this calculated value to the display. Then, the display records or displays the fish length based on this calculated value.

Therefore, the operator can accurately know the length of the fish school by looking at the display on the display, and can immediately judge whether or not it is appropriate to capture the fish school. In this case, the fish length is determined not by focusing on the reflected image from the school of fish among those recorded or displayed as an image, but by focusing on the images of individual fish scattered around the image of the school of fish.

(Example) Hereinafter, an example of the present invention will be described based on the drawings. FIG. 1 shows a block diagram showing the configuration of an embodiment of the present invention. As shown in the figure, the fish body length display device of this embodiment includes a transmitter 1, a receiver 2, a transducer 3, an arithmetic unit 4, and a color cathode ray tube display 5.

The transmitter 1 applies a drive pulse (electrical pulse) to the transducer 3 in synchronization with a synchronization signal sent from an arithmetic unit 4, which will be described later.

The transducer 3 receives the drive pulse, excites the vibrator, and emits ultrasonic waves 6a into the water.

This ultrasonic wave 6a hits the entire fish 7 as a target object and is reflected, and the reflected wave 6b (echo) is received by the transducer 3. In this case, the reflection level of the reflected wave 6b at the reception position is subject to propagation attenuation in the water, so it is lower than the reflection level at the reflection position (position near the fish 7), that is, the complete reflection level without attenuation. The transducer 3 receives the reflected wave that has undergone propagation attenuation, converts it into an electrical signal, and applies the received signal to the receiver 2. The receiver 2 has a propagation attenuation correction circuit 8 and an amplification circuit 9. The propagation attenuation correction circuit 8 performs propagation attenuation correction of the received signal, and the amplification circuit 9 performs signal amplification. In this embodiment, the received signal propagation attenuation correction circuit 8 is a TVG (Time Varied Gain).
It is composed of a circuit that corrects the underwater propagation attenuation of the reflected wave to create a received signal whose level does not change depending on the depth. here
TVG means time-varying gain, that is, the amplification gain changes over time.
A TVG circuit is a circuit in which the amplification gain increases over time in each transmission period to compensate for attenuation due to distance to a reflecting target.

As is well known, there are two types of propagation attenuation: diffusion attenuation and absorption attenuation, and correction of diffusion attenuation is performed on the received signal value.
This is achieved by adding 40Logr, and the absorption attenuation correction is achieved by adding 20αrloge to the received signal value. Here, r means the distance between the transducer 3 and the fish 7, and α means the absorption attenuation coefficient. The reason is as follows.

When a sound wave with acoustic output Io travels a distance r, it undergoes diffusion loss and absorption loss, and its intensity becomes Io·e ^- 〓 ^r / r ² (where α is the absorption coefficient) in the case of spherical diffusion. If there is a single fish with an equivalent cross-sectional area σ at this distance, its reflection intensity is expressed as Io・e ^- 〓 ^r /r ²・σ. Using this as a virtual sound source, the sound source retraces the same path. reaches the receiver. Therefore, the reflection intensity Ie at the receiver surface is: Ie＝Io・e ^- 〓 ^r / r ²・σ・e ^- 〓 ^r / r ² = Ioσe ^-2 〓 ^r / r ⁴
...(1) So, in the case of a single fish, it is inversely proportional to the fourth power of the distance. Then, if we take the logarithm of equation (1) and multiply it by 10 in decibels (dB), we get 10logIe=10logIoσ−20αrloge−40logr…(2) Therefore, regardless of the distance r, an output with a constant amplitude can be obtained. Therefore, it is only necessary to increase the gain by 40logr and 20αrloge. The received signal corrected in this way will have the same amplitude regardless of the depth if the fish is of the same species and body length. This corrected received signal is amplified by an amplifier circuit 9 and applied to the arithmetic unit 4 as a corrected received signal.

Arithmetic unit 4 generates a synchronization signal and sends the synchronization signal to transmitter 1 as described above. On the other hand, in response to the corrected received signal, the fish length is calculated as follows. First, as a preprocess for calculating the fish body length, the reflectance t _s of the ultrasonic waves reflected from the fish 7 is determined.

Since the corrected received signal value is a value that is not affected by depth and is determined only by the length of the fish, the reflectance t _s is determined by the value of the corrected received signal and each of the following known values, That is, using each value of the ultrasonic transmission level (the value of the transmission level of the transducer 3), the receiving sensitivity of the transducer 3, the directivity function of the ultrasound, the gain of the receiver 2, etc. It can be easily obtained using a well-known calculation formula. In this case, in this embodiment, the reflection level is determined using the beam at the central axis of the ultrasonic beam bundle emitted from the transducer 3, so the directivity function of the ultrasonic wave is 1, which facilitates calculation.

By the way, the fish body length L of the fish 7 and the previously determined reflectance t _s have the following relationship.

t _s =aL ² ...(1) where a is a coefficient.

Therefore, the fish body length L is L=√ _s (2), and the fish body length L can be obtained by calculating this equation (2).

Here, the coefficient a is a coefficient determined by the fish species,
Determined by experiment. For example, the coefficient value for mackerel is 2.5×10 ⁻³ and for yellowtail is 3.3×10 ⁻³ . Normally, the habitat of fish is determined by water depth, water temperature, sea area, season, etc., so it is easy to identify the fish species.
The value of can be easily given.

Next, the calculated value of the fish body length L determined by equation (2) is added to the color cathode ray tube display 5 of the fish finder, and the fish image on the screen is colored in accordance with the fish body length L. It's becoming like that.

That is, the color cathode ray tube display 5 is provided with a coloring circuit that changes the color depending on the strength of the signal, that is, the magnitude of the calculated value of the fish body length L. By passing the signal (calculated value) through the coloring circuit, a color corresponding to the calculated value is assigned.

As a result, as shown in FIG. 2, the image of the fish 7 projected on the color cathode ray tube display 5 displays a color corresponding to the fish body length L, so that the fish body length L can be determined just by looking at this image. This makes it possible to immediately judge whether or not it is appropriate to catch a school of fish.

In this case, the reflection level and the coefficient a of the above equation (1)
The value of L varies depending on the species of fish, so even if the color is the same on the screen, the length L of the fish varies depending on the species of fish.

Therefore, in this embodiment, the colors C ₁ , C ₂ , C ₃ , C ₄ and C ₅ represent each fish species (sardines, mackerel, mackerel,
The standard fish body length L for three types of tuna) is shown, and by comparing this calibration display and the image, it is possible to immediately know the fish body length L for each fish species.

For example, if the fish species in the image in Figure 2 is mackerel,
The image of mackerel A is labeled with the color C ₄ , so the length of the fish is 16 cm, and the image of mackerel B is labeled with the color C ₂ , so it can be seen that the length of the fish is 32 cm.

Although the above embodiment is configured so that the fish body length L can be recognized by viewing a color cathode ray tube display image, the present invention is not necessarily limited to this, and for example, the fish body length L calculated by the calculator 4 can be recognized by a recording type. The display may be configured to display numbers, graphs, or any other format that can be read at a glance.

(Effects of the invention) Since the present invention has the structure and operation described above, it is possible to know the length of the fish just by looking at the display on the display, and this makes it possible to determine the suitability of catching a school of fish (fishing net It is possible to effectively judge the suitability of dropping
It is possible to greatly improve the efficiency of fishing operations.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing the configuration of an embodiment of the present invention, and FIG. 2 is an operational explanatory diagram showing a display example of a color cathode ray tube display. 1... Transmitter, 2... Receiver, 3... Transducer/receiver, 4... Arithmetic unit, 5... Color cathode ray tube display, 6a... Ultrasonic wave, 6b... Reflected wave, 7...
Fish, 8... Propagation attenuation correction circuit, 9... Amplification circuit,
C ₁ - C ₅ ... Color, A, B ... Image of mackerel.

Claims (1)

[Scope of utility model registration request] An ultrasonic transducer that emits ultrasonic waves into the water, receives echoes from fish, converts the received ultrasonic signals into electrical signals, and outputs the signals output from the ultrasonic transducer. A propagation attenuation correction circuit that corrects the amount of propagation attenuation so that the amplitude of the echo output signal from a single fish is constant regardless of depth, and an operation that calculates the fish body length based on the output signal of this propagation attenuation correction circuit. 1. A fish body length display device comprising: a fish body length display device; and a fish body length display device that displays a fish body length based on a value calculated by a computing device.