JP2025013027A - Underwater detection device, underwater detection method and program - Google Patents

Abstract

To provide an underwater detection device, a method for underwater detection, and a program which can smoothly and properly estimate fish catches.SOLUTION: An underwater detection device 10 includes: a fish quantity index calculation unit 11c for calculating a fish quantity index on the basis of an electrical signal output from plural ultrasonic transducers; an image generation unit 11b for generating a display image including information related to the fish quantity index; and a corrected value reception processing unit 11d for receiving the input of a corrected value for correcting the fish quantity index. The fish quantity index calculation unit 11c corrects the calculation formula of the fish quantity index on the basis of the input corrected value.SELECTED DRAWING: Figure 3

Description

The present invention relates to an underwater detection device for detecting underwater targets, an underwater detection method for detecting underwater targets, and a program for causing a computer to execute a function for detecting underwater targets.

Underwater detection devices that detect underwater targets are known. This type of underwater detection device transmits ultrasonic waves into the water, receives the reflected waves, calculates the echo intensity from each position in the water, and displays a three-dimensional distribution of the echo intensity (echo image) on a screen.

For example, an underwater detection device transmits umbrella-shaped transmission waves along a conical surface from a transmitter/receiver having multiple ultrasonic transducers, and receives the reflected waves with the transmitter/receiver. From the electrical signals output from each ultrasonic transducer of the transmitter/receiver upon receiving the reflected waves, multiple receiving beams are formed by beamforming that are arranged in the circumferential direction on the conical surface, and a receiving signal is generated for each receiving beam. From the receiving signals thus generated, an echo image according to the scanning range of the receiving beams is generated and displayed.

The following Patent Document 1 describes an underwater detection system that generates an echo image by transmitting multiple types of transmission waves with different beam widths. In this underwater detection system, a reception signal is generated for each transmission wave with a different beam width, and an echo image is generated for each generated reception signal.

Patent No. 6722521

Experienced fishermen can estimate the amount of fish caught by referring to the echo images. However, it is difficult for inexperienced fishermen to make this estimate properly. Furthermore, even experienced fishermen find it difficult to concentrate on making this estimate while steering. These problems can be solved by adding a function to the underwater detection device that estimates and displays the total weight of fish within the detection range.

The calculation formula for this estimation may generally include parameters related to the transmission and reception of waves from the underwater detection device, as well as parameters such as the target strength of individual fish. However, it is usually difficult for fishermen to grasp these parameters. Furthermore, the target strength of individual fish differs depending on the fish species, and may also change depending on the sea area and season. Therefore, it is difficult for fishermen to input these parameters appropriately into the underwater detection device to accurately estimate the catch volume.

In view of these problems, the present invention aims to provide an underwater detection device, an underwater detection method, and a program that can smoothly and accurately estimate fish catches.

The first aspect of the present invention relates to an underwater detection device. The underwater detection device according to this aspect includes a fish quantity index calculation unit that calculates a fish quantity index based on electrical signals output from a plurality of ultrasonic transducers, an image generation unit that generates a display image including information related to the fish quantity index, and a correction value reception processing unit that receives input of a correction value for correcting the fish quantity index, and the fish quantity index calculation unit corrects the calculation formula for the fish quantity index based on the correction value.

According to the underwater detection device of this embodiment, the calculation formula for the fish quantity index is corrected based on a correction value input by a user such as a fisherman. In general, a user can easily estimate the amount of fish (e.g., tons) that he or she has caught, and therefore can smoothly and appropriately input a correction value for correcting the displayed fish quantity index to the actual amount of fish. Therefore, the calculation formula for the fish quantity index can be corrected based on the input correction value so as to approach the actual amount of fish caught. This correction process therefore allows the amount of fish caught to be estimated smoothly and appropriately.

In the underwater detection device according to this embodiment, the calculation formula includes a fish quantity correction coefficient, the correction value is a correction magnification, and the fish quantity index calculation unit can be configured to calculate the fish quantity index by multiplying the fish quantity correction coefficient by the correction magnification as the new fish quantity correction coefficient.

According to this configuration, each time a correction factor is input by the user, the correction factor is accumulated and a new fish quantity correction coefficient is set. This allows the user to repeatedly input the correction factor, thereby bringing the fish quantity index closer to the fish quantity that corresponds to the user's rough estimate. This makes it possible to smoothly and appropriately display the fish quantity index according to the user's fishing ground, fish species, and season.

In this configuration, the calculation formula may be an original calculation formula consisting of a first formula including the weight per fish to be caught, the target strength, the intensity of the transmitted wave, and the receiving sensitivity of the transducer, and a second formula not including these, in which the first formula is replaced with a formula consisting of an approximate value of the first formula and the fish quantity correction coefficient.

According to this configuration, the calculation formula takes into account the weight and target strength of the fish to be caught, the strength of the transmitted waves, and the receiving sensitivity of the transducer, so that the fish quantity index can be calculated with high accuracy using this calculation formula. In addition, because the first formula containing these parameters is replaced with a term consisting of the approximate number of the first formula and a fish quantity correction coefficient, the user can smoothly correct the calculation formula with a correction multiplier according to their own fish quantity estimate without having to know these parameters. This allows the user to smoothly bring the displayed fish quantity index closer to their own fish quantity estimate. Therefore, the user can properly display a fish quantity index that is close to their own catch.

In the underwater detection device according to this aspect, the display image may be configured to include the current value of the fish quantity index calculated by the fish quantity index calculation unit.

With this configuration, the user can ascertain the amount of fish at their current location from the fish abundance index value.

The display image may also be configured to include a time series graph of the fish quantity index calculated by the fish quantity index calculation unit.

With this configuration, the user can see from the graph the changes in fish abundance on the ship's route so far. This allows the user to easily understand the locations where fish should be caught.

Alternatively, the display image may be configured to include an image of multiple positions along the ship's wake, with information indicating the fish abundance index value at each position.

This configuration also allows the user to understand the changes in fish abundance on the ship's route so far. This allows the user to smoothly understand the locations where fish should be caught.

The underwater detection device according to this aspect further includes a target area reception processing unit that receives a designation of a target area within the search range for which the fish quantity index is to be calculated, and the fish quantity index calculation unit can be configured to calculate the fish quantity index for the designated target area.

With this configuration, the user can specify a target area, such as an area that the user should pay attention to or an area that can be enclosed by a purse seine net, and the fish quantity indicator for that target area can be displayed. Therefore, the user can smoothly proceed with catching fish based on the displayed fish quantity indicator.

A second aspect of the present invention relates to an underwater detection method executed by an underwater detection device. The underwater detection method according to this aspect includes the steps of calculating a fish quantity index based on electrical signals output from a plurality of ultrasonic transducers, generating a display image including information related to the fish quantity index, and accepting input of a correction value for correcting the fish quantity index, and the step of calculating the fish quantity index corrects a calculation formula for the fish quantity index based on the correction value.

The underwater detection method according to this aspect can achieve the same effects as the underwater detection device according to the first aspect.

A third aspect of the present invention is a program that causes a computer of an underwater detection device to perform the following functions: calculate a fish quantity index based on electrical signals output from a plurality of ultrasonic transducers; generate a display image including information related to the fish quantity index; and accept input of a correction value for correcting the fish quantity index, and the function of calculating the fish quantity index includes a function of correcting a calculation formula for the fish quantity index based on the correction value.

The program according to this aspect can achieve the same effects as the underwater detection device according to the first aspect.

As described above, the present invention provides an underwater detection device, an underwater detection method, and a program that can smoothly and accurately estimate fish catches.

The effects and significance of the present invention will become clearer from the description of the embodiment shown below. However, the embodiment shown below is merely an example of how the present invention can be put into practice, and the present invention is in no way limited to the embodiment described below.

FIG. 1 is a diagram showing a schematic diagram of an underwater searching performed by an underwater detection device according to an embodiment. FIG. 2 is a diagram illustrating a schematic view of underwater exploration by an underwater detection device according to an embodiment. FIG. 3 is a block diagram showing the configuration of an underwater detection device according to an embodiment. FIG. 4 is a diagram illustrating an example of an echo image displayed on a display unit according to the embodiment. FIG. 5 is a diagram illustrating a schematic diagram of a propagation state of a transmission pulse and its reflected wave (reflected pulse) on one beam axis according to an embodiment. 6A and 6B are diagrams each showing a schematic diagram of an orthogonal coordinate system having two axes representing the beam number and the sample number according to an embodiment. FIG. 7 is a flowchart showing a process for receiving a fish quantity correction factor according to the embodiment. FIG. 8 is a diagram showing an example of a fish quantity correction magnification acceptance screen according to the embodiment. FIG. 9 is a flowchart showing a process for displaying the fish quantity index according to the embodiment. FIG. 10 is a diagram illustrating an example of a display image of information related to fish quantity indexes according to an embodiment. FIG. 11 is a diagram illustrating an example of a fish quantity calculation region receiving screen according to the embodiment. FIG. 12 is a diagram showing an example of a display image including information related to the fish quantity index according to the modified example. FIG. 13 is a diagram showing an example of a display image including information related to the fish quantity index according to another modified example.

Embodiments of the present invention will be described below with reference to the drawings. For convenience, the drawings are appropriately labeled with mutually orthogonal X, Y and Z axes. The X-axis and Y-axis directions are horizontal, and the Z-axis direction is vertical. The positive X-axis direction is the direction in which the ship moves.

Figures 1 and 2 are schematic diagrams showing how underwater detection is performed by the underwater detection device 10.

In Figures 1 and 2, φ is the azimuth angle centered on the transducer 13 installed on the bottom of the ship S1, and θ is the tilt angle of the scanning plane SP1 (described below) relative to the horizontal plane (X-Y plane).

The underwater detection device 10 is equipped with a transducer 13 installed on the bottom of a vessel S1, such as a fishing boat. The underwater detection device 10 transmits a pulse of sound waves (transmission pulse) from the transducer 13, and receives sound waves (echoes) reflected (backscattered) by objects such as fish present in the water with the same transducer 13. The underwater detection device 10 detects objects present in the water based on the echoes received by the transducer 13.

The transducer 13 is equipped with a large number of ultrasonic transducers. When transmitting, each ultrasonic transducer converts the input electrical signal into a sound wave and emits it, and when receiving, it converts the incoming sound wave into an electrical signal and outputs it. Typically, the transducer 13 is cylindrical, with several hundred ultrasonic transducers regularly arranged on its side.

Here, the area to be detected by the underwater detection device 10 is a conical surface. The axis of this conical surface coincides with the central axis of the transducer 13 (here, the Z-axis). This conical surface is called the scanning surface SP1, and the apex and axis of this scanning surface SP1 are called the origin and the scanning axis, respectively. The origin coincides with the position of the transducer 13, and the scanning axis extends vertically downward from this origin. Here, the scanning axis coincides with the Z-axis. The angle that the scanning surface SP1 makes with the horizontal plane (X-Y plane) is the tilt angle θ mentioned above.

As shown in FIG. 1, when transmitting, the underwater detection device 10 transmits a transmission beam TB1 with maximum intensity on the scanning plane SP1 over the entire circumference. This transmission beam TB1 has an intensity distribution that is symmetrical with respect to the scanning axis (Z-axis in FIG. 1), and its vertical width is relatively narrow.

As shown in FIG. 2, when receiving waves, the underwater detection device 10 forms multiple reception beams RB1 with maximum sensitivity on the scanning plane SP1. The reception beams RB1 are formed by performing beamforming processing on the electrical signals output from multiple ultrasonic transducers arranged in the transducer 13.

Each receiving beam RB1 is a pencil beam that is narrow in both the vertical and horizontal directions and has the same directivity. A straight line that passes through the origin and faces the direction in which the sensitivity of the receiving beam RB1 is maximum is the beam axis of each receiving beam RB1. Multiple receiving beams RB1 are formed in a line at regular angular intervals in the direction of the azimuth angle φ around the entire circumference of the scanning plane SP1. The underwater detection device 10 converts the intensity of the sound waves received by each receiving beam RB1 into color and displays it as an image (echo image).

Figure 3 is a block diagram showing the configuration of the underwater detection device 10.

The underwater detection device 10 comprises a control unit 11, a memory unit 12, a transducer 13, a transmission processing unit 14, a reception processing unit 15, a transmission/reception switching unit 16, a display unit 17, a display processing unit 18, an input unit 19, and an input processing unit 20. The transducer 13 is installed on the bottom of the ship S1 as described above, and the other components such as the control unit 11 are installed in the wheelhouse of the ship S1, etc.

The control unit 11 includes an arithmetic processing circuit such as a CPU (Central Processing Unit) and executes the control processing described below using a program stored in the memory unit 12. The memory unit 12 includes a storage medium such as a ROM (Read Only Memory), a RAM (Random Access Memory), and a hard disk. The memory unit 12 stores a program for the control unit 11 to execute the control processing.

As described above, the transducer 13 has multiple ultrasonic transducers 13a. During each transmission and reception period (ping), the transducer 13 transmits ultrasonic waves as the transmission beam TB1 in FIG. 1, and receives the reflected waves at each ultrasonic transducer.

The transmission processing unit 14 outputs a transmission signal for transmitting ultrasonic waves to the transducer 13 via the transmission/reception switching unit 16 in response to control from the control unit 11. The transmission signal is a signal that vibrates at a predetermined amplitude for a fixed period of time, as shown in FIG. 3. During one transmission of the transmission beam TB1, this transmission signal is supplied to each ultrasonic transducer 13a of the transducer 13 via the transmission/reception switching unit 16. As a result, ultrasonic waves corresponding to the transmission signal are transmitted from each ultrasonic transducer 13a, as shown in FIG. 3. The ultrasonic pulse transmitted during one transmission is called a transmission pulse.

The reception processing unit 15 receives the electrical signals output by each ultrasonic transducer 13a of the transmitter/receiver 13 upon receiving the reflected ultrasonic waves via the transmission/reception switching unit 16, and performs amplification and noise removal (bandpass filter) processing on the received electrical signals. The reception processing unit 15 outputs the electrical signals that have been subjected to these processes to the control unit 11.

When transmitting the transmission beam TB1, the transmission/reception switching unit 16 outputs the transmission signal output from the transmission processing unit 14 to the transducer 13 (ultrasonic transducer 13a), and outputs the electrical signal output from the transducer 13 (ultrasonic transducer 13a) to the reception processing unit 15 for a certain period of time from the timing when the transmission of the transmission beam TB1 is completed.

Note that while FIG. 3 illustrates one transmission processing unit 14 and one reception processing unit 15, the above-mentioned processing in the transmission processing unit 14 and reception processing unit 15 is performed for each ultrasonic transducer 13a arranged in the transmitter/receiver 13. Therefore, the control unit 11 receives individual electrical signals that have been amplified and subjected to noise removal processing from the electrical signals output from each ultrasonic transducer 13a. When these electrical signals are input to the control unit 11, they are converted by an A/D converter into digital signals with a predetermined sampling period.

The display unit 17 includes a display such as a liquid crystal display. The display processing unit 18 causes the display unit 17 to display a predetermined image in response to control from the control unit 11. The input unit 19 includes input means such as operation keys and a mouse. The input processing unit 20 outputs a signal corresponding to an operation on the input unit 19 to the control unit 11 in response to control from the control unit 11. The display unit 17 and the input unit 19 may be configured as a liquid crystal panel in which a touch panel is superimposed on a liquid crystal display.

In this embodiment, the functions of the reception signal generating unit 11a, the image generating unit 11b, the fish quantity index calculating unit 11c, the correction value receiving processing unit 11d, and the target area receiving processing unit 11e are provided to the control unit 11 by the program stored in the memory unit 12.

The reception signal generating unit 11a performs beamforming on the electrical signals (digital signals) output from each ultrasonic transducer 13a to form the reception beam RB1 in FIG. 2, and generates a reception signal corresponding to the sound waves incident on the transducer 13 from the beam axis direction (the direction of a predetermined azimuth angle φ and tilt angle θ) of each reception beam RB1. Furthermore, the reception signal generating unit 11a performs band limiting and envelope detection processing on the reception signals in each beam axis direction to obtain an envelope signal in each beam axis direction.

The band limiting process is a process for extracting the frequency components of the transmission signal output from the transmission processing unit 14. This process is performed when the transmission signal output from the transmission processing unit 14 is a signal with a constant frequency (CW signal).

On the other hand, if the transmission signal output from the transmission processing unit 14 is not a constant frequency signal (CW signal) but a frequency modulated chirp signal (FM signal), the reception signal generating unit 11a performs matched filter processing on the reception signal in each beam axis direction instead of band limiting processing. The reception signal generating unit 11a then performs envelope detection processing on the signal after matched filter processing to obtain the envelope signal in each beam axis direction.

The envelope signal thus acquired is a signal indicating echo intensity (sound wave strength) that changes according to the time elapsed from the transmission timing of the transmission beam TB1 (ultrasound wave). Here, the time elapsed from the transmission timing corresponds to the distance from the transducer 13 in each beam axis direction. The control unit 11 acquires the echo intensity at each distance position in each beam axis direction from the echo signal of each received beam by associating the time elapsed from the transmission timing with the distance. The echo intensity is acquired with a predetermined distance resolution.

The image generator 11b generates an echo image that displays the echo intensity at each distance position in each beam axis direction on a predetermined color scale. The image generator 11b outputs the echo images generated for each ping to the display processor 18 in sequence. As a result, the echo image updated for each ping is displayed on the display unit 17. In addition, the image generator 11b generates a display image that includes information about the fish quantity index, as described below.

Figure 4 is a schematic diagram showing an example of an echo image displayed on the display unit 17.

In the mode for displaying echo images, the screen of the display unit 17 is divided into left and right areas A1 and A2. Of these, echo image P10 is displayed in area A1. Here, echo image P10 is displayed as an image of the ship S1 as seen from directly above. An image P11 of the ship S1 is placed at the center of echo image P10, and furthermore, the track P12 of the ship S1 thus far is shown. Also included in echo image P10 is a straight line P13 indicating the direction of the ship's bow.

Furthermore, in echo image P10, a range at a certain distance from the position of the ship (image P11) is shown by circular boundaries P14, P15, and P16. The diameters of boundaries P14, P15, and P16 are, for example, 200 m, 400 m, and 600 m. In echo image P10, the above-mentioned echo intensity is displayed using a predetermined color scale. For convenience, in FIG. 4, the range where the echo intensity is high is hatched. For example, the hatched range P17 is the range where the echo intensity is high. The hatched range is the range where a school of fish may be present.

Area A2 is divided vertically into several sections, and each section displays information indicating the current position of ship S1 (longitude, latitude), the water temperature at the current position, and a graph showing the change in water temperature over time. For convenience, the display of these images in area A2 has been omitted in Figure 4.

By referring to the echo image P10, users such as fishermen can ascertain the presence of a school of fish around the vessel S1. The echo image P10 in FIG. 4 displays the echo intensity of a so-called layered school of fish. That is, a school of fish may form a narrow layer in the vertical direction and be widely distributed in the horizontal direction. Furthermore, each fish in this school may swim with their heads facing in roughly the same direction. Such a school is a layered school of fish.

When the ship S1 is located above the layered school of fish, the echo image P10 shows an echo intensity called an "eight pattern" as shown in FIG. 4. In the example of FIG. 4, it can be estimated that the individual fish that make up the layered school of fish are pointing their heads almost parallel to the bow direction. That is, in this case, on the starboard and port sides of the ship S1, the ultrasonic waves transmitted from the transducer 13 are incident perpendicularly to the sides of the fish, so the reflected waves (backscattered waves) from the fish are relatively strong. On the other hand, on the bow and stern sides of the ship S1, the sound waves are incident parallel to the sides of the fish, so the reflected waves from the fish are weak. Therefore, in such a case, the echo image P10 shows clear responses from the school of fish in two areas that are symmetrical to the ship, as shown in FIG. 4.

This phenomenon is well known to fishermen. Experienced fishermen can estimate the tonnage of fish caught from these figure-of-eight responses.

However, it is difficult for inexperienced fishermen to make this estimation properly. Even experienced fishermen find it difficult to concentrate on making this estimation while steering. This problem can be solved by adding a function to the underwater detection device 10 that not only displays the echo image P10, but also estimates and displays the total weight of fish present within the detection range.

The calculation formula for this estimation may generally include parameters related to the transmission and reception of waves by the underwater detection device 10, as well as parameters such as the target strength of individual fish. However, it is usually difficult for fishermen to grasp these parameters. Furthermore, the target strength of individual fish differs depending on the fish species, and may also change depending on the sea area and season. Therefore, it is extremely difficult for fishermen to input these parameters appropriately into the underwater detection device 10 to accurately estimate the catch volume.

To solve this problem, in this embodiment, the underwater detection device 10 is equipped with a function that allows for smooth and accurate estimation of the fish catch. This function is executed by the fish quantity index calculation unit 11c, the correction value reception processing unit 11d, and the target area reception processing unit 11e shown in Figure 3. These processes are described below.

<Fish Quantity Index Calculation Section>
The fish quantity index calculation unit 11c calculates a fish quantity index that can be an index of the total weight of fish contained in the target area based on the electrical signals output from the multiple ultrasonic transducers 13a installed in the transducer 13. The fish quantity index is calculated using a predetermined calculation formula. The process of deriving this calculation formula will be explained below while showing various parameters.

(1) Target strength The strength of a fish's reflection of sound waves is expressed as target strength. Target strength is defined as the ratio (the former divided by the latter) of the strength of the reflected wave at a position a unit distance away from the object to the strength of the sound wave incident on the object. In the following, the unit distance is represented by _r0 , which is defined as 1 m.

(2) Pseudo Target and Pseudo Fish Quantity If the average weight and the average target strength of the individual fish contributing to the generation of the echo image P10 are represented by W and _Ts , respectively, a point target whose weight and target strength are equal to the average values W and _Ts , respectively, is called a pseudo target.

Here, we assume that it is possible to generate "echoes identical to those generated by the fish that contribute to the generation of the echo image P10" by placing any number of pseudo targets at any position on the scanning plane SP1 in Figures 1 and 2. The sum of the weights of these pseudo targets is called the pseudo fish amount corresponding to the sonar response.

(3) Formulation of the quantity of artificial fish (3-1) Equation of target strength _Ts The relationship between the strength of the sound transmitted by the transducer 13 and the received signal resulting from a "dummy target located on the beam axis" is explained below along the sound wave propagation process. Here, it is assumed that the distance _rt between the transducer 13 and the artificial target is sufficiently large compared to the size of the transducer 13.

First, consider the sound pressure of the transmission pulse at a position _r0 away from the origin of the scanning plane SP1 in Fig. 1. Generally, sound intensity is defined as the energy passing through a unit area per unit time, and is proportional to the square of the effective value of the sound pressure. The amplitude of the sound pressure of the transmission pulse increases from zero, reaches a maximum value, and then attenuates to zero. Therefore, the maximum intensity of the transmission pulse is proportional to "the square of the effective value of the sound pressure at the time when the amplitude reaches a maximum value."

In the following, the intensity of the acoustic pulse is defined by this square value, and it is assumed that the sound pressure changes as a sine wave in any one cycle of the transmission pulse. _With these definitions and assumptions, the intensity _I0 of the transmission pulse is expressed as _I0 = ^P2max /2, where _Pmax is the maximum value of the sound pressure amplitude. In the following, 1 μPa (micropascal) is used as the unit of sound pressure.

Figure 5 is a schematic diagram showing the propagation state of a transmitted pulse and its reflected wave (reflected pulse) along one beam axis.

The transmitted pulse is attenuated by spherical divergence and absorption while propagating from the origin to the pseudo target. If the absorption coefficient (the degree of attenuation of sound waves per unit distance) is a [dB/m], the intensity _I1 of the transmitted pulse incident on the pseudo target is expressed by the following equation.

This pulse is reflected by the pseudo target and propagates toward the origin as a reflected pulse. The intensity _I2 of the reflected pulse at a position a unit distance _r0 away from the pseudo target is expressed by the following equation, based on the definition of the target strength _Ts described above.

The strength of the reflected pulse incident on the transducer 13 is expressed by the following equation, similar to equation (1) above.

As described above, in the underwater detection device 10, the electric signal from the ultrasonic transducer 13a is amplified by an amplifier and band-limited by an analog filter in the reception processing unit 15 of FIG. 3. Next, the underwater detection device 10 samples this processed signal with an A/D converter when it is input to the control unit 11 to generate a digital signal. The underwater detection device 10 then forms a reception beam RB1 from the digital signal corresponding to a predetermined group of ultrasonic transducers, and generates a signal (reception signal) corresponding to the sound wave received by the transducer 13 by each reception beam RB1. After processing each reception signal with a band-limiting filter, a pulse compression filter, etc., the underwater detection device 10 generates an envelope signal that is a signal equal to the instantaneous amplitude of the signal. In the following, this envelope signal is treated as a dimensionless quantity.

The sound pressure waveform of the acoustic pulse signal incident on the transducer 13 is distorted by the process of converting it into an electric signal and the processing performed thereafter. However, since these conversions and processing can generally be assumed to be linear and time-invariant, the ratio of the maximum instantaneous amplitude of the acoustic pulse signal to the maximum envelope signal is constant regardless of the distance _rt to the pseudo target or the target strength _Ts of the pseudo target. Hereinafter, this ratio (the latter divided by the former) is referred to as the reception sensitivity, and is represented by the parameter k. The unit of reception sensitivity is 1/μPa.

The maximum value _Amax of the envelope signal of the reflected pulse when it enters the transducer 13 and the intensity _I3 of the reflected pulse are related by the following equation:

Solving this for the target strength _Ts gives:

(3-2) Normalized Amplitude Data Each receiving beam RB1 is assigned a beam number j according to the azimuth angle φ of its beam axis. For example, the beam number j of the receiving beam RB1 pointing toward the stern direction in a plan view is set to j=0, and further, the clockwise direction in a plan view is set to positive, and the beam numbers j=1, 2, 3, ... are assigned to each receiving beam RB1 in order of increasing angle between the stern direction (reference direction) and the beam axis direction. In this case, if the total number of receiving beams RB1 is 128, the beam numbers j of the receiving beams RB1 pointing toward the port direction, bow direction, and starboard direction are 32, 64, and 96, respectively.

Furthermore, a sample number n is assigned to each sampling time of the envelope signal in chronological order. The start time of transmission of the transmission beam TB1, i.e., the moment when the leading edge of the transmission pulse is emitted from the transducer 13, is set as the reference time, and the sample number at this time is set to n = 0.

The envelope signal obtained by one transmission is composed of multiple digital data by the above sampling. The sampling period for this sampling may be the same as the sampling period of the A/D converter described above, or may be different from this sampling period.

If data generated by receive beam RB1 with beam number j and sample number n is represented as A(j, n), A'(j, n) defined by the following equation is called normalized amplitude data.

Here, _rn is the distance from the origin to the position corresponding to the time _tn at which the nth data is sampled. In other words, when a false target is located at a distance _rn from the origin, the leading edge of the reflected pulse from this false target is sampled as the nth data. If the sampling frequency is _fs , then _tn = n/ _fs , and so _rn is defined by the following equation, where c is the speed at which sound waves propagate.

If the time width (pulse width) of the transmitted pulse is τ, the time when the trailing edge of the reflected pulse is sampled is t _n + τ, and the distance from the origin of the corresponding position is r _n + (cτ/2). In the following, we assume that the difference between these distances is sufficiently small compared with the distance from the origin to the pseudo target. That is, we assume the following relationship:

At this time, as can be seen from equations (5) and (6), the square value of the maximum value _A'max of the normalized amplitude data A'(j,n) coincides with the target strength _Ts .

(3-3) Amplitude Data Space Here, we define an orthogonal coordinate system with the beam number j and sample number n as its two axes. Figures 6(a) and 6(b) are diagrams that show this orthogonal coordinate system. For convenience, a 17 x 17 grid (cell) is shown in Figures 6(a) and 6(b), but the number of grids (cells) in reality is significantly greater than this.

The position of each grid (cell) on the vertical and horizontal axes indicates the position of the respective numbers on the vertical and horizontal axes. The numbers on the vertical and horizontal axes increase by one each, so the vertical and horizontal widths of each cell are both 1. With the horizontal coordinate being the beam number j and the vertical coordinate being the sample number n, the above-mentioned normalized amplitude data A'(j,n) is assigned to the cell located at point (j,n). The collection of normalized amplitude data arranged in this manner is called the amplitude data space. In contrast, the underwater space that is the target of detection by the underwater detection device 10 is called the real space.

(3-4) Point spread coefficient It is assumed that there is a false target at a position in real space corresponding to point P1 in Fig. 6(a). In this case, in the amplitude data space, normalized amplitude data caused by this false target (target) is generated behind point P1 (upper side in Fig. 6(a)). In Fig. 6(a), these cells are shown by hatching. In this way, the region (region in the amplitude data space) where normalized amplitude data is generated due to the target is called the echo region.

The vertical width of the echo region is determined by the time width of the transmit pulse. The horizontal width of the echo region is determined by the beam width of the receive beam. The normalized amplitude data values of each cell in the echo region generally have non-uniform values depending on the envelope waveform of the transmit pulse and the beam pattern of the receive beam.

In any cell in the echo region, the squared value of the normalized amplitude data is proportional to the target strength _Ts . Therefore, the sum of the squared values of the normalized amplitude data in the echo region is also proportional to the target strength _Ts .

Now consider a point target with a target strength _Ts of 1. By definition of normalized amplitude data, the maximum value of normalized amplitude data attributable to this target is 1. The sum of the squared values of this normalized amplitude data is called the point spread coefficient, which is represented by V _units .

From the proportionality relationship given above and the definition of the point spread coefficient V _unit , the following relationship is obtained:

(Lemma A)
For a single false target, the sum of the squared values of its normalized amplitude data divided by the point spread coefficient V _unit is equal to the target strength T _s of the false target.

(3-5) Sum of target strength _Ts As shown in Fig. 6(b), consider the case where there are two false targets in the orthogonal coordinate system that defines the amplitude data space, and the echo areas generated by these false targets partially overlap. Focus on one cell included in this overlap. In Fig. 6(b), this cell is filled in black.

In addition, the following discussion will be made with the received signal as a complex envelope signal. When a false target exists at only one of points P1 and P2, the complex envelopes generated in this black cell are respectively _A1e ^+jθ1 and _A2e ^+jθ2 . If the instantaneous amplitude when both exist simultaneously is _A12 , its square value is expressed by the following equation.

The distance between the transducer 13 and each individual fish changes between the time when the underwater detection device 10 transmits a transmission pulse and the time when it transmits the next pulse. The amount of this change can be assumed to vary randomly by more than about 1/4 of the wavelength of the transmission wave. Therefore, if _the average value ^A2av of the squared instantaneous amplitudes obtained by multiple transmissions is calculated ^{, the} value approximately equals _A12 + _A22 .

Similarly, if the echo areas of any number of pseudo targets overlap, the following relationship holds:

(Lemma B)
The squared values of normalized amplitude data at coordinates where echoes from multiple false targets overlap are averaged over multiple transmissions and are approximately equal to the sum of the squared values of normalized amplitude data generated by each false target.

The following relationship can be obtained from the above Lemma A and Lemma B.

(theorem)
In a region (region in amplitude data space) including all echoes from the group of false targets, the sum of the squared values of the normalized amplitude data is divided by the point spread coefficient V _unit , and the quotient is averaged over multiple transmissions to obtain a value that is approximately equal to the sum of the target strengths Ts of the group of false targets.

(3-6) Calculation Formula for Simulated Fish Quantity As can be seen from the above definition of simulated fish quantity and the above theorem, in order to obtain the simulated fish quantity, _Qq defined by the following formula may be averaged over multiple transmissions of the transmission pulse.

The symbol Σ in equation (12) means the sum of all (j, n) pairs that are processed in one ping of the transmitted and received waves.

(4) Definition of fish quantity index In the above formula (12), the strength of the transmission pulse _I0 and the square of the receiving sensitivity ^k2 are parameters specific to each underwater detection device 10, and it is difficult for ordinary fishermen to obtain their accurate values. In addition, the value of the target strength _Ts is obtained by substituting the body length of the collected fish into an empirical formula, but this calculation is not easy for ordinary fishermen. On the other hand, it is easy for fishermen to roughly estimate the amount of fish caught (in tons).

The fish quantity index calculation unit 11c in FIG. 3 calculates the fish quantity index Q defined by the following formula as an approximation of the pseudo fish quantity. The fish quantity index calculation unit 11c then outputs the calculated value of the fish quantity index Q, or the value obtained by averaging the value of the fish quantity index Q over multiple transmissions, to the image generation unit 11b, which then displays it on the display unit 17.

The coefficient _C0 is an approximation of W/( _2I0 · ^k2 · _Ts ). This approximation may be a value obtained by substituting the values of W and _Ts for a representative fish and the design values of _I0 and k for the underwater detection device 10, or may be a value determined in advance so that the fish quantity index Q closely matches the catch amount estimated by the fisherman or the actual catch amount.

The coefficient C _cor is a fish quantity correction coefficient. A fish quantity correction magnification factor input by a user such as a fisherman is reflected in this fish quantity correction coefficient C _cor . That is, until a fish quantity correction magnification factor is input for the first time, the fish quantity index calculation unit 11c sets the fish quantity correction coefficient C _cor to an initial value of 1 and calculates the fish quantity index Q. Furthermore, every time a fish quantity correction magnification factor is input, the fish quantity index calculation unit 11c updates the value of the fish quantity correction coefficient C _cor using the following formula.
"New C _cor " = "Fish amount correction magnification" x "Old C _cor "
That is, the fish quantity index calculation unit 11c calculates the fish quantity index Q by multiplying the fish quantity correction coefficient C _cor immediately before the correction factor is input by the fish quantity correction factor, and sets the result as a new fish quantity correction coefficient C _cor .

In this way, the fish quantity correction factor input by the user is reflected in the fish quantity correction coefficient C _cor , so that the calculation formula (13) for the fish quantity index Q can be corrected to approach the actual catch amount based on the input fish quantity correction factor. Therefore, by repeatedly inputting the fish quantity correction factor, the user can bring the fish quantity index Q closer to the fish quantity that corresponds to the user's rough estimate. Therefore, the fish quantity index Q that corresponds to the user's fishing ground, fish species, and season can be displayed smoothly and appropriately on the display unit 17.

The above formula (13) is stored in the storage unit 12 of Fig. 3, and the updated fish quantity correction coefficient _Ccor is also updated and stored in the storage unit 12 as needed. The control unit 11 calculates the fish quantity index Q using the above formula (13) and the updated fish quantity correction coefficient _Ccor stored in the storage unit 12 through the function of the fish quantity index calculation unit 11c, and causes information related to the fish quantity index Q to be displayed on the display unit 17 through the function of the image generation unit 11b. This process will be described later with reference to Fig. 9.

(5) Calculation Formula for Point Spread Coefficient V _unit Below, a supplementary explanation will be given regarding the calculation formula for the point spread coefficient V _unit .

The pulse width of the transmission pulse, the beam width of the reception beam, and the tilt angle are represented by τ, ψ, and θ, respectively. Here, the beam width ψ is defined as "the beam width in a plane tangent to the scanning plane SP1 at the beam axis," and it is assumed that the beam width ψ does not depend on the tilt angle θ. The arbitrarily selected reference values for the sampling frequency f _s , the pulse width τ, and the beam width ψ are represented by f _s0 , τ ₀ , and ψ ₀ , respectively. The value of the point spread coefficient V _unit at the tilt angle θ=0° corresponding to these reference values is represented by V ₀ .

In this case, the point spread coefficient V _unit at any f _s , τ, ψ, and θ is expressed by the following equation.

For example, if the sampling interval (1/f _s ) is proportional to the pulse width τ of the transmit pulse and the beamwidth of the receive beam can only take values φ ₀ , then the point spread coefficient V _unit can be expressed as a function of θ as V _unit =V ₀ /cos θ.

(6) Setting of fish quantity correction factor Fig. 7 is a flow chart showing the process of receiving the fish quantity correction factor. This process is performed by the control unit 11 using the function of the correction value reception processing unit 11d in Fig. 3.

When the user finds that the fish quantity index calculated by the above formula (13) differs from the total weight of the fish that the user actually caught, the user inputs an instruction to input a fish quantity correction factor via the input unit 19 in order to correct this discrepancy. In response to this input instruction, the control unit 11 causes the display unit 17 to display a correction factor acceptance screen for inputting the fish quantity correction factor, and accepts the input of the fish quantity correction factor from the user (S11).

Figure 8 shows an example of the fish quantity correction multiplier reception screen 100.

The fish quantity correction magnification reception screen 100 includes a rectangular magnification input area 101, a button 102 for confirming the input, and a button 103 for returning to the screen. When the user clicks on the magnification input area 101 via the input unit 19, a drop-down display of magnification options is displayed below the magnification input area 101, arranged vertically. The options are, for example, values ranging from 0.1 to 2.0 in increments of 0.1. The user selects the desired magnification from the displayed options. The selected magnification is then displayed in the magnification input area 101. In the example of FIG. 8, a magnification of 1.1 has been selected.

The user can change the fish quantity correction multiplier by clicking the multiplier input area 101 again. After inputting the fish quantity correction multiplier in this way, the user clicks button 102. This confirms the input of the fish quantity correction multiplier. If the user clicks button 103 without clicking button 102, the input operation of the fish quantity correction multiplier is cancelled.

Returning to Fig. 7, when the user confirms the input of the fish quantity correction factor (S12: YES), the control unit 11 sets the value obtained by multiplying the fish quantity correction factor _Ccor before input by the input fish quantity correction factor as a new fish quantity correction factor _Ccor (S13). This updates the fish quantity correction factor _Ccor . On the other hand, when the user cancels the input operation without confirming the input of the fish quantity correction factor (S12: NO), the control unit 11 ends the process of Fig. 7 without updating the fish quantity correction factor _Ccor .

<Display of fish abundance index>
9 is a flow chart showing the process of displaying the fish quantity index. This process is performed by the control unit 11 using the functions of the image generating unit 11b and the fish quantity index calculating unit 11c in FIG.

When the display process of the fish quantity index is started, the control unit 11 judges whether or not the fish quantity correction coefficient C _cor has been updated by the process of Fig. 7 (S21). If the fish quantity correction coefficient C _cor has been updated (S21: YES), the control unit 11 sets the updated fish quantity correction coefficient C _cor in the above formula (13) (S22). If the fish quantity correction coefficient C _cor has not been updated (S21: NO), the control unit 11 skips step S22 and proceeds to step S23.

After that, when the transmission and reception period (one ping) ends and the data necessary for calculating the fish quantity index Q is collected (S23: YES), the control unit 11 uses the function of the fish quantity index calculation unit 11c to calculate the fish quantity index Q using the above formula (13) (S24). The control unit 11 then uses the function of the image generation unit 11b to generate a display image including information related to the calculated fish quantity index Q (S25), and causes the generated display image to be displayed on the display unit 17 (S26).

When the process for the current ping is thus completed, the control unit 11 judges whether or not the operation for displaying information on the fish quantity index Q has been completed by the user's operation (S27). If this display operation has not been completed (S27: NO), the control unit 11 returns the process to step S21 and executes the same process. If the process of Fig. 8 is executed in parallel with the process of Fig. 9 and the fish quantity correction coefficient C _cor is updated (S21: YES), the updated fish quantity correction coefficient C _cor is applied to the above formula (13) (S22), and the processes from step S23 onwards are executed.

In this way, the control unit 11 repeatedly executes the processes of steps S21 to S26 until the display operation of the information related to the fish quantity index Q is completed (S27: NO). This causes the display of the information related to the fish quantity index Q to be updated for each ping. Thereafter, when this display operation is completed (S27: YES), the control unit 11 ends the process of FIG. 9.

Figure 10 is a diagram showing an example of a display image 110 of information related to the fish quantity index Q.

The display image 110 includes a current fish quantity index Q value 111 calculated by the function of the fish quantity index calculation unit 11c in step S24 of FIG. 9, and a time series graph 112 of the fish quantity index Q calculated so far. The current fish quantity index Q value 111 may be the current fish quantity index Q value itself, or it may be the average value of the fish quantity index Q values calculated over a certain period of time from the present. The same is true for the fish quantity index Q value at each time on the graph 112.

The horizontal and vertical axes of graph 112 are time (units: minutes) and fish quantity index (units: tons), respectively. The current time is set at the right end of the horizontal axis, and the further to the left the time goes back in time. Here, graph 112 shows the change in the value of the fish quantity index from the present up to 20 minutes ago.

The user can grasp the fish quantity at the current location from the fish quantity index value 111 included in the display image 110, and can further grasp the transition of the fish quantity on the ship's route so far from the graph 112. This allows the user to smoothly grasp the state of the schools of fish and the positions where fish should be caught.

The display image 110 of FIG. 10 may be arranged in one of the divided areas of area A2 on the screen of FIG. 4. Alternatively, the display image 110 of FIG. 10 may be displayed overlapping the echo image P10 on the screen of FIG. 4 so as not to overlap the echo image P10 as much as possible. In this case, the display image 110 may be switched between being displayed and being erased in response to an operation from the user.

<Setting the fish quantity calculation area>
The range in which the fish quantity index is calculated using formula (13) may be limited by the user from the entire range scanned in one ping to a predetermined range. For example, when the user is engaged in purse seine fishing, the range in which the fish quantity index is calculated may be limited to the range that can be enclosed by the purse seine (for example, a range with a radius of 200 m from the user's ship).

Figure 11 shows an example of the fish quantity calculation area reception screen 120.

The control unit 11 performs the process of accepting the fish quantity calculation area using the function of the target area acceptance processing unit 11e in FIG. 3. Using this function, the control unit 11 displays the fish quantity calculation area acceptance screen 120 in FIG. 11 in response to the user's operation to set the calculation area.

The fish quantity calculation area reception screen 120 includes a rectangular range input area 121, a button 122 for confirming the input, a button 123 for returning to the screen, and a button 124 for manual setting. The range input area 121 is an area for inputting the radius of a circle centered on the ship when viewed from directly above the ship.

When the user clicks on the range input area 121 via the input unit 19, range selection candidates are displayed in a caption below the range input area 121. The selection candidates are, for example, values ranging from 200 m to 800 m in increments of 50 m. The user selects the desired range from the displayed selection candidates. The selected range value is then displayed in the range input area 121. In the example of Figure 11, a range with a radius of 200 m centered on the ship is selected.

The user can change the fish quantity calculation range by clicking range input area 121 again. After inputting the fish quantity calculation range in this way, the user clicks button 122. This confirms the input of the fish quantity calculation range. If the user clicks button 123 without clicking button 122, the input operation of the fish quantity calculation range is canceled.

To set an arbitrary range, the user operates button 124. This causes an image including boundary lines P14 to P16, similar to the echo image P10 in FIG. 4, to be displayed. The user uses the input unit 19 to draw a line on this image enclosing the desired range, and operates the confirm button. This causes the range enclosed by this line to be confirmed as the fish quantity calculation range.

The control unit 11 (fish quantity index calculation unit 11c) performs the process of step S24 in FIG. 9, using the range thus set by the user as the calculation range. That is, it performs the process of step S24 using data in the range set by the user from the amplitude data space shown in FIG. 6(a). For example, as shown in FIG. 11, if a range of 200 m radius from the ship is set as the fish quantity calculation range, it performs the process of step S24 using data included in the range of sample numbers on the vertical axis corresponding to 0 to 200 m.

In this way, by limiting the fish quantity calculation range, the user can display information about the fish quantity index Q for the range in which the user intends to catch fish. This allows the user to smoothly proceed with fishing.

Effects of the embodiment
According to the above embodiment, the following effects can be achieved.

As shown in FIG. 3, the underwater detection device 10 includes a fish quantity index calculation unit 11c that calculates the fish quantity index Q based on electrical signals output from multiple ultrasonic transducers 13a, an image generation unit 11b that generates a display image including information related to the fish quantity index Q, and a correction value reception processing unit 11d that receives input of a correction value (correction multiplier) for correcting the fish quantity index Q. The fish quantity index calculation unit 11c corrects the above formula (13), which is the calculation formula for the fish quantity index Q, based on the input correction value.

According to this configuration, the fish quantity correction coefficient C _cor in the above formula (13) is corrected based on a correction value (correction factor) input by a user such as a fisherman. Generally, a user can easily estimate the amount of fish (e.g., tons) that he or she has caught, and therefore can smoothly and appropriately input a correction value for correcting the displayed fish quantity index Q to the actual amount of fish. Therefore, the calculation formula for the fish quantity index Q can be corrected based on the input correction value so as to approach the actual catch amount. This correction process therefore allows the fish catch amount to be smoothly and appropriately estimated.

As described above, equation (13), which is a formula for calculating the fish quantity index Q, includes the fish quantity correction coefficient _Ccor , and the correction value for correcting equation (13) is the correction magnification. The fish quantity index calculation unit 11c calculates the fish quantity index Q by multiplying the previous fish quantity correction coefficient _Ccor by the correction magnification as the new fish quantity correction coefficient _Ccor .

By repeatedly inputting the correction factor, the user can bring the fish quantity index Q closer to the fish quantity that corresponds to the user's rough estimate. This allows the fish quantity index Q to be displayed smoothly and appropriately according to the user's fishing grounds, fish species, and season.

Here, equation (13) for calculating the fish quantity index Q is obtained by replacing the original equation (12) consisting of a first equation including the weight W and target strength _Ts of the fish to be caught, the intensity _I0 of the transmitted wave, and the receiving sensitivity k of the transducer 13, with a second equation that does not include these, by an equation consisting of an approximation of the first equation (coefficient _C0 ) and a fish quantity correction coefficient _Ccor .

In this way, the fish quantity index Q can be calculated with high accuracy by the formula (13), which is a calculation formula for the fish quantity index Q, since the weight W and target strength _Ts of the fish to be caught, the strength _I0 of the transmission wave, and the receiving sensitivity k of the transducer 13 are taken into consideration. Furthermore, since the first formula including these parameters is replaced with a term consisting of the approximate number (coefficient _C0 ) of the first formula and the fish quantity correction coefficient _Ccor as described above, the user can smoothly correct the calculation formula by a correction factor according to his/her own fish quantity estimate without knowing these parameters. This allows the user to smoothly bring the displayed fish quantity index Q closer to his/her own fish quantity estimate. Therefore, the user can properly display the fish quantity index Q that is close to his/her own catch.

As shown in FIG. 10, the display image 110 includes the current fish quantity index Q value 111 calculated by the fish quantity index calculation unit 11c. This allows the user to understand the amount of fish at the current location from the fish quantity index value 111.

The display image 110 also includes a graph 112 of a time series of the fish quantity index Q calculated by the fish quantity index calculation unit 11c. This allows the user to understand the changes in the fish quantity on the ship's route so far from the graph 112. This allows the user to smoothly understand the location where fish should be caught.

As shown in FIG. 3, the underwater detection device 10 further includes a target area reception processing unit 11e that receives a designation of a target area within the search range for which the fish quantity index Q is to be calculated, and as described with reference to FIG. 11, the fish quantity index calculation unit 11c calculates the fish quantity index Q for the designated target area.

This allows the user to specify a target area, such as an area that the user should pay attention to or an area that can be enclosed by a purse seine net, and display the fish quantity index Q for that target area. This allows the user to smoothly proceed with catching fish based on the displayed fish quantity index Q.

<Example of change>
In the above embodiment, the display image 110 in FIG. 10 is shown as an example of a display image including information related to the fish quantity index Q, but the display image is not limited to this.

For example, as shown in FIG. 12, plots P18 may be added at regular intervals on the ship's wake P12 in the echo image P10, and the value of the fish quantity index Q (in tons) at the position (time) of each plot P18 may be added to the right of the plot P18. Alternatively, as shown in FIG. 13, circular marks P19 with a diameter corresponding to the value of the fish quantity index Q at each position may be superimposed at regular intervals on the ship's wake P12. In this case, the value of the fish quantity index Q at that point may also be added near each circle.

These display images also allow the user to understand the changes in fish abundance along the ship's route so far. This allows the user to easily understand the locations where fish should be caught.

Alternatively, a time series graph may be displayed in which the horizontal axis of FIG. 10 is modified to the distance traveled (accumulated distance traveled). The speed of a boat during fish search is not necessarily constant. In contrast, if the horizontal axis of the time series graph is the distance traveled (accumulated distance traveled), when a user refers to this graph and wishes to return to a location where a promising fish quantity index value was generated, the user can easily estimate that location based on the distance traveled (accumulated distance traveled) on the horizontal axis of the graph.

In the above embodiment, the fish quantity correction coefficient C _cor is corrected by a correction factor, but the correction value for correcting the fish quantity correction coefficient C _cor is not limited to this. For example, a numerical value added to or subtracted from the fish quantity correction coefficient C _cor may be used as the correction value for the fish quantity correction coefficient C _cor .

In addition, the screen for accepting the fish quantity correction multiplier is not limited to the fish quantity correction multiplier acceptance screen 100 shown in FIG. 8, but may be an acceptance screen of other configurations. Similarly, the screen for accepting the designation of the fish quantity calculation area is not limited to the fish quantity calculation area acceptance screen 120 shown in FIG. 11, but may be an acceptance screen of other configurations.

The control unit 11 may further include a function that allows the user to set multiple fish quantity correction coefficients _Ccor according to, for example, fish species, fishing grounds, etc. In this case, the control unit 11 causes the storage unit 12 to store the fish quantity correction coefficients _Ccor set by the user in association with the fish species or fishing grounds. In the process of applying the fish quantity correction coefficient _Ccor , the control unit 11 causes the display unit 17 to display selection candidates for fish species or fishing grounds, and applies the fish quantity correction coefficient _Ccor associated with the fish species or fishing ground selected by the user via the input unit 19 to the calculation formula (13) to calculate the fish quantity index Q. This allows the user to obtain the fish quantity index Q adapted to the fish species and fishing grounds that he or she wishes to catch, and thus allows the user to proceed with fishing more smoothly. In this case, correction is performed by the fish quantity correction magnification (correction value) for each fish quantity correction coefficient _Ccor .

In the above embodiment, the fish quantity index calculation unit 11c and the like are realized as functions of the control unit 11 provided by the program stored in the memory unit 12, but these do not necessarily have to be realized as functions provided by the program stored in the memory unit 12. For example, one or more of these functions may be configured by hardware that integrates an FPGA (field-programmable gate array) or logic circuits.

In the above embodiment, an underwater detection device 10 that transmits and receives waves along the conical scanning surface SP1 is shown, but the present invention may be applied to an underwater detection device 10 that transmits and receives waves in other ways. The transmitter for transmitting waves and the receiver for receiving waves may be arranged separately. A calculation formula other than equation (13) may be used to calculate the fish quantity index Q. In this case, the calculation formula only needs to include a fish quantity correction coefficient that is corrected by a correction value input by the user.

In addition, various modifications of the embodiments of the present invention are possible within the scope of the claims.

REFERENCE SIGNS LIST 10 Underwater detection device 11 Control unit 11b Image generation unit 11c Fish quantity index calculation unit 11d Correction value reception processing unit 11e Target area reception processing unit 12 Memory unit 13 Transmitter/receiver 13a Ultrasonic transducer 110 Display image 111 Fish quantity index value 112 Graph P12 Track P18 Plot P19 Mark

Claims (9)

a fish quantity index calculation unit that calculates a fish quantity index based on electrical signals output from a plurality of ultrasonic transducers;
an image generating unit that generates a display image including information about the fish quantity index;
a correction value reception processing unit that receives an input of a correction value for correcting the fish quantity index,
The fish quantity index calculation unit corrects the calculation formula for the fish quantity index based on the correction value.
An underwater detection device characterized by: 2. The underwater detection device according to claim 1,
The calculation formula includes a fish quantity correction coefficient,
the correction value is a correction magnification,
The fish quantity index calculation unit calculates the fish quantity index by multiplying the fish quantity correction coefficient by the correction magnification as the new fish quantity correction coefficient.
An underwater detection device characterized by: 3. The underwater detection device according to claim 2,
The calculation formula is a formula obtained by replacing an original formula consisting of a first formula including the weight of each fish to be caught, the target strength, the intensity of the transmitted wave, and the receiving sensitivity of the transducer, with a second formula not including these, by a formula consisting of an approximate value of the first formula and the fish quantity correction coefficient.
An underwater detection device characterized by: 2. The underwater detection device according to claim 1,
The display image includes the current value of the fish quantity index calculated by the fish quantity index calculation unit.
An underwater detection device characterized by: 2. The underwater detection device according to claim 1,
The display image includes a time series graph of the fish quantity index calculated by the fish quantity index calculation unit.
An underwater detection device characterized by: 2. The underwater detection device according to claim 1,
The display image includes an image in which information indicating the value of the fish quantity index at a plurality of positions aligned on the ship's wake is added to each of the positions.
An underwater detection device characterized by: 2. The underwater detection device according to claim 1,
A target area receiving processing unit is further provided for receiving a designation of a target area within the search range that is to be used for calculating the fish quantity index,
The fish quantity index calculation unit calculates the fish quantity index for the specified target area.
An underwater detection device characterized by: An underwater detection method performed by an underwater detection device, comprising:
Calculating a fish quantity index based on electrical signals output from the plurality of ultrasonic transducers;
generating a display image including information about the fish abundance index;
and receiving an input of a correction value for correcting the fish quantity index;
The step of calculating the fish quantity index includes correcting a calculation formula for the fish quantity index based on the correction value.
An underwater detection method comprising: The underwater detection device's computer
A function of calculating a fish quantity index based on electrical signals output from a plurality of ultrasonic transducers;
generating a display image including information about the fish abundance index;
and receiving an input of a correction value for correcting the fish quantity index.
A program, wherein the function of calculating the fish quantity index includes a function of correcting a calculation formula for the fish quantity index based on the correction value.

Images