JP2005249398A - Metering fish finder and fish body length metering method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a metering fish finder capable of elongating the detection distance, while keeping simple body separation accuracy high. <P>SOLUTION: This fish finder is provided with an FM transmission waveform generation part 4 for generating an FM signal waveform, and a correlation processing part 5 constituted of a matched filter. An ultrasonic wave 11 is transmitted from a transducer 1 into the water by using an FM transmission signal generated from the FM transmission waveform generation part 4, and, when an echo 12 from a target 13 is received, correlation processing of the received signal is performed by the correlation processing part 5, and a signal having a compressed pulse width is taken out. The detection distance can be elongated by elongating the transmission pulse width at the transmission time, and the received signal having the short pulse width can be taken out at the reception time, to thereby improve echo resolution, and to separate each simple fish accurately. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a measuring fish finder and a fish length measuring method using a split beam system.

In order to investigate the amount of resources in the sea, a measuring fish finder using an acoustic technique has been used conventionally. In this measuring fish finder, the ratio of the sound pressure level of the ultrasonic wave transmitted from the transducer and the sound pressure level of the echo reflected back from the fish, that is, the reflection strength TS (Target Strength) is obtained. The body length of the fish is calculated from the obtained reflection intensity TS. It is known that the relationship of the following equation is established between the reflection intensity TS and the fish body length L.
TS = 20logL + 20logA (1)
Here, A is a coefficient determined by the signal frequency and the fish type.

  In order to calculate the fish length L by the above equation (1), it is necessary to accurately measure the value of the reflection intensity TS. However, the reception sensitivity of the transducer differs depending on the direction, and the sensitivity with respect to the sound axis direction is maximum, and the reception sensitivity decreases as it deviates from this direction. For this reason, even if it is a fish with the same body length, since the receiving level in a transmitter / receiver differs with the position (azimuth | direction), the fish body length calculated | required from reflection intensity TS becomes a different value. Therefore, it is necessary to detect the direction in which the echo arrives by some method and correct the value of the reflection intensity TS according to the direction. Therefore, in order to detect this azimuth, a split beam system is generally widely used in measuring fish finders.

FIG. 10 is a diagram for explaining the direction detection principle in the split beam type fish finder. When the phase difference between the signals received by the two transducers of channel 1 (ch1) and channel 2 (ch2) is φ, the angle of arrival of the echo is θ, and the center-to-center distance between channels 1 and 2 is d. In the meantime, the following equation holds.
φ / k = dsinθ (2)
Here, k is a wave number, and k = 2π / λ (λ: wavelength of ultrasonic waves).
Therefore, from equation (2)
θ = sin ⁻¹ (φ / kd) (3)
Therefore, if the center distance d of the transmitter / receiver is known from the equation (3), the arrival angle θ of the echo, that is, the azimuth can be calculated by measuring the phase difference φ of the received signal. Then, according to the calculated arrival angle θ, the directivity characteristic of the transducer is corrected, and the reflection intensity TS ₀ obtained from the echo is converted into an accurate reflection intensity TS. When the directivity characteristic of the transducer is D (θ), the reflection intensity TS is expressed by the following equation.
TS = D (θ) ² · TS ₀ (4)
By correcting the reflection intensity TS in this way, the fish length L can be accurately obtained from the equation (1).

  FIG. 7 is an electric block diagram of a conventional measuring fish finder 200 using the split beam method. Reference numeral 50 denotes a transmitter / receiver having channels CH1 to CH4 divided into four, and transmits ultrasonic waves 51 into the water, and returns ultrasonic echoes 52 that are reflected by the target fish 53 and returned. Reception is performed by vibrators (not shown) provided in channels CH1 to CH4. Reference numerals 61 to 64 denote transmission / reception units connected to the channels CH1 to CH4 of the transducer 50, respectively, and a transmission circuit that supplies a transmission signal to the transducer of each channel of the transducer 50 and reception by each transducer. A receiving circuit that performs processing such as amplification on the echo signal and a transmission / reception switching circuit that switches between transmission and reception operations. Reference numeral 70 denotes an arithmetic processing unit which gives a transmission command to the transmission / reception units 61 to 64 at a predetermined timing and analyzes the echo signals received by the transmission / reception units 61 to 64 to calculate the fish length L. I do. Reference numeral 80 denotes a display unit composed of a liquid crystal display or the like, which displays fish length data calculated by the arithmetic processing unit 70, a fish school image, and the like on the screen.

  FIG. 8 is a flowchart showing the operation of the above-described measuring fish finder 200. In step S <b> 11, the transmission / reception units 61 to 64 receive a transmission command from the arithmetic processing unit 70 and output a transmission signal to the transducer 50, and the transducer of the transducer 50 is excited by this signal to generate the ultrasonic wave 51. Is sent underwater. The transmission signal at this time is a pulse (burst signal) having predetermined time widths t1 and t2 as shown in FIG. 9 (a) or (b). This pulse consists of a sine wave signal of a continuous wave (a waveform whose frequency does not change with time) and the frequency of the sine wave signal is, for example, 38 KHz. In step S <b> 12, the echo 52 that is reflected back from the ultrasonic wave 51 transmitted underwater is received by the transmitter / receiver 50, and is transmitted to the transmission / reception units 61 to 64. The waveform of the reception signal at this time is basically the same waveform as the transmission signal shown in FIG.

  By the way, echoes from single fish and echoes from multiple fish in a flock are different in signal level even if they are the same length fish of the same fish species. In order to accurately measure the fish length, it is necessary to separate the echo signal of a single fish from the echo signals of multiple fish. Therefore, in step S13, the received signal output from the transmission / reception units 61 to 64 is analyzed by the arithmetic processing unit 70, so that the single separation process is performed. In the following step S14, the reflection intensity TS is calculated from the sound pressure level of the transmission signal and the sound pressure level of the reception signal (echo). Here, based on the above-described split beam principle, the reflection intensity TS corrected in accordance with the echo arrival angle obtained from the phase difference of the received signals is calculated. In this case, since the channel of the transmitter / receiver 50 is divided into four, the arrival angle of the echo from the front / rear and the left / right directions with respect to the traveling direction of the ship is measured by selecting the channel.

  When the reflection intensity TS is calculated, the fish length L of the target 53 is calculated according to the equation (1) in step S15. Next, in step S <b> 16, display data for displaying the calculated fish length L data in a graph is generated by the arithmetic processing unit 70. At this time, display data for displaying an image of the school of fish is also generated based on the received echo signal. In step S17, using the generated display data, the fish length L is displayed on the display unit 80 together with the fish school image in a graph.

The split beam type measuring fish finder as described above is described in, for example, the following patent documents.
JP-A-6-160522 JP 2000-46946 A JP 2002-82155 A

In the conventional measuring fish finder 200, since the transmission signal is a continuous wave as described above, the following problems occur.
In order to increase the accuracy of the single separation, it is necessary to increase the resolution of the echo. Therefore, it is required to use a pulse having a short time width t1 as shown in FIG. 9A as the transmission signal. However, when a short pulse is used, a filter with a wide reception band is necessary to faithfully extract the echo signal by the transmission / reception units 61 to 64. However, since the power of the short pulse is small, the reception band is widened. Then, the S / N ratio is greatly reduced, and echoes from the deep field cannot be detected accurately, making it difficult to increase the detection distance. On the other hand, when a pulse having a long time width t2 as shown in FIG. 9B is used, since the power is large, the detection distance can be made long. On the other hand, since the pulse width is long, the resolution of the echo is lowered. However, it becomes difficult to separate single fish.

  As described above, the conventional method has a problem that the detection distance does not increase when the accuracy of the single separation is increased using a short pulse, and the accuracy of the single separation decreases when the detection distance is extended using a long pulse. there were.

  The present invention solves the above-mentioned problems, and an object of the present invention is to provide a measuring fish finder capable of extending the detection distance while maintaining high accuracy of single unit separation.

  The measuring fish finder of the present invention has FM transmission signal generation means for generating a transmission signal having a time width T1 composed of FM (frequency modulation) signals, and a channel divided into a plurality of parts, and is generated by the FM transmission signal generation means. A transmitter / receiver that receives the transmitted signal and transmits ultrasonic waves underwater, and receives ultrasonic echoes reflected back from the fish, and a reception signal received by the transmitter / receiver. Correlation processing is performed by comparing with a signal, and a correlation processing means for extracting a received signal corresponding to a reference signal and having a time width T2 shorter than the time width T1 of the transmission signal is extracted by the correlation processing means Analyzing the received signal, single unit separation means for detecting the reception signal of the single fish, and calculating the reflection intensity based on the reception signal of the single fish detected by the single unit separation unit, and calculating the fish length from the obtained reflection intensity Calculating means for calculating, and a display means for displaying the fish length data calculated by the calculating means.

  In the fish length measuring method of the present invention, the transmission signal having the time width T1 composed of the FM signal is provided to a transducer having a plurality of divided channels, and ultrasonic waves are transmitted from the transducer to the water. And a step of receiving an ultrasonic echo reflected back from the fish by the transducer, and performing a correlation process by comparing the received signal received by the transducer with a predetermined reference signal. A step of extracting a reception signal corresponding to the signal and having a time width T2 shorter than the time width T1 of the transmission signal, and a step of analyzing the reception signal extracted by the correlation processing to detect a reception signal of a single fish And calculating the reflection intensity based on the received signal of the single fish and calculating the fish length from the obtained reflection intensity.

  A feature of the present invention resides in that an FM signal whose frequency changes with time is used as a transmission signal, and only a predetermined signal is extracted from an echo by correlation processing at the time of reception. By doing this, at the time of transmission, the time width (pulse width) of the transmission signal can be increased to increase the detection distance, and at the time of reception, a reception signal with a short time width (pulse width) can be extracted. Pulse compression improves echo resolution, and single fish can be separated with high accuracy.

  In the present invention, the correlation processing means is typically composed of a matched filter. The matched filter calculates the degree of coincidence between the received signal received by the transducer and the reference signal by a product-sum operation, and extracts a received signal having a time width T2 based on the calculation result. When a matched filter is used, signal detection is performed by taking in not only signal level information but also phase information by product-sum operation, so that signal detection accuracy is improved compared to signal detection based only on level. Can do.

  Further, as a means for separating a single fish, a method for determining that the received signal is due to a single fish when the amplitude of the received signal is equal to or greater than a certain value and the time width near the peak value is within a certain range. Can be adopted. According to this, since it is determined whether or not it is a single fish from two conditions of amplitude and time width, it is possible to reliably detect a single fish and to improve the accuracy of single separation.

  In a preferred embodiment of the present invention, the display means displays a mark representing a single fish on the screen in correspondence with the position of each single fish based on the reception signal of the single fish detected by the single separation means. In the conventional measuring fish finder, since such a mark was not displayed, it was impossible to determine in which part of the school the fish were separated. For example, when single separation is performed inside a dense fish school, a plurality of targets are measured as one target, so that an error in measuring the fish length increases. In this case, the reliability of data obtained by measuring the fish length can be determined if the target separated by itself can be confirmed on the video, but since such video is not displayed on the screen in the past, this determination is not possible. It was possible. In the present invention, the above-mentioned problem is solved by displaying a single fish mark corresponding to the position of the fish. For example, if a large number of single fish marks are displayed in the periphery of a school of fish that can be easily separated, this is evidence that the single separation has been performed normally, and it can be determined that the reliability of fish length data is high. On the other hand, if a large number of single fish marks are displayed in the center of the school of fish that should not be able to separate the fish, it is determined that the fish body length data is not reliable because the fish has not been separated normally. it can.

  When displaying a single fish mark as described above, a selection means for selecting a fish length range on the screen is provided, and only the single fish mark belonging to the fish length range selected by this selection means is displayed on the screen. You may do it. According to this, it is possible to easily know in which region a single fish of a certain size is distributed. Moreover, you may make it display the mark from which a display mode differs according to the magnitude | size of a single fish. Also in this case, it is possible to easily know in which region a single fish of a certain size is distributed.

  According to the present invention, since an FM signal is used as a transmission signal and a specific signal is extracted by performing correlation processing at the time of reception, the detection distance can be increased by a transmission signal having a long time width (pulse width). In addition, the resolution can be increased by pulse compression by correlation processing, and single unit separation can be performed with high accuracy.

  FIG. 1 is an electric block diagram showing an embodiment of a measuring fish finder 100 according to the present invention. In the figure, reference numeral 1 denotes a transmitter / receiver having channels CH1 to CH4 divided into four, which transmits ultrasonic waves 11 in water and echoes of ultrasonic waves reflected by a target fish 13 and returned. 12 is received by a vibrator (not shown) provided in each of the channels CH1 to CH4. The transmitter / receiver 1 transmits in-phase ultrasonic waves from the transducers of all the channels CH1 to CH4 when transmitting the ultrasonic waves 11, and when receiving the echo 12, the set of the channels CH1 and CH2 and the channels CH3 and CH4. Echoes from the front / rear and left / right directions are received by the set and the set of channels CH1 and CH4 and the set of channels CH2 and CH3. Reference numerals 21 to 24 denote transmission / reception units connected to the channels CH1 to CH4 of the transmitter / receiver 1, respectively, and a transmission circuit for supplying a transmission signal to the transducer of each channel of the transducer 1 and reception by each transducer. A receiving circuit that performs processing such as amplification on the echo signal and a transmission / reception switching circuit that switches between transmission and reception operations. An arithmetic processing unit 3 includes an FM transmission waveform generation unit 4, a correlation processing unit 5, a single unit separation unit 6, a data calculation unit 7, and a display control unit 8.

  The FM transmission waveform generation unit 4 is a block that generates a waveform of an FM (frequency modulation) signal used as a transmission signal, and constitutes FM transmission signal generation means in the present invention together with the transmission / reception units 21 to 24. The correlation processing unit 5 is a block that performs correlation processing by comparing the received signal received by the transducer 1 with a predetermined reference signal and extracts a predetermined received signal. Configure the means. The single separation unit 6 is a block for separating the reception signal of the single fish from the reception signal extracted by the correlation processing unit 5, and constitutes a single separation means in the present invention. The data calculation unit 7 is a block that calculates the reflection intensity based on the reception signal of the single fish detected by the single unit separation unit 6 and calculates the fish body length from the obtained reflection intensity. Configure. The display control unit 8 is a block that generates display data for displaying the fish length data calculated by the data calculation unit 7 and the image of the school of fish, and controls the display thereof. Reference numeral 9 denotes a display unit composed of a liquid crystal display or the like, which displays fish length data, fish school images, and the like on the screen. The display unit 9 constitutes display means in the present invention.

  Note that the functions of the FM transmission waveform generation unit 4, the correlation processing unit 5, the single unit separation unit 6, and the data calculation unit 7 are actually realized by software processing by the microcomputer that constitutes the calculation processing unit 3. Of course, each of the blocks 4 to 7 can be configured by hardware without using software.

  Next, the operation of the weighing fish finder 100 having the above configuration will be described. The FM transmission waveform generation unit 4 generates an FM transmission signal waveform as shown in FIG. 2A and outputs the waveform to the transmission / reception units 21 to 24. This FM transmission signal is a pulse having a time width T1 composed of a frequency-modulated sine wave burst signal. As an example, the FM transmission signal is a signal obtained by applying a modulation of ± 2 KHz to a carrier having a frequency of 38 KHz. That is, the frequency of the FM transmission signal continuously changes from 40 KHz to 36 KHz during the time width T1 (the frequency gradually decreases with time). The transducer of the transducer 1 is excited by this signal, and transmits ultrasonic waves 11 having the same waveform as in FIG.

  When the pulse of the ultrasonic wave 11 transmitted into the water is reflected by the target fish 13 and returns as the echo 12, the echo 12 is received by the transducer 1 and sent to the transmission / reception units 21 to 24. The waveform of the reception signal at this time is basically the same waveform as the transmission signal shown in FIG. 2A as shown in FIG. However, in reality, the received signal contains a lot of noise due to the effects of echoes and propeller noise from floating substances in the water, and the ideal waveform as shown in FIG. For convenience, the received signal and the transmitted signal are treated as the same waveform. In the transmission / reception units 21 to 24, processing such as filtering and amplification is performed on the received signal, and the output is given to the correlation processing unit 5.

  The correlation processing unit 5 is composed of a matched filter. FIG. 3A is a diagram illustrating the principle of correlation processing using a matched filter. FIG. 3A (a) shows a reference signal, which is a chirp signal whose frequency decreases with time. The waveform data of this reference signal is stored in advance in a memory (not shown). FIG. 3A (b) is a signal to be compared with the reference signal, specifically, a reception signal output from the transmission / reception units 21 to 24 (that is, an input signal of the correlation processing unit 5).

  In the correlation processing, the product sum of the level of the received signal and the level of the reference signal at each time point is calculated while slightly shifting the phases of the reference signal (a) and the received signal (b). FIG. 3A shows a state of product-sum operation at a certain point in time, where multiplication is performed with the level value of the received signal level value reference signal at a predetermined sampling interval, and the products X1, X2,. Add over. Then, the value of the added value X1 + X2 +... + Xn is used as a correlation output. FIG. 3B shows the state of product-sum operation at another time point. In this case as well, the level of the received signal is multiplied by the level value of the reference signal at a predetermined sampling interval, and the products Y1, Y2, and Y2 are multiplied. ... Yn is added over the sampling interval. The value of the added value Y1 + Y2 +... + Yn is used as a correlation output.

  The correlation processing unit 5 outputs a signal having a level corresponding to the degree of coincidence between the received signal and the reference signal. The level of the signal output from the correlation processing unit 5 increases as the matching degree increases, and the level of the signal output from the correlation processing unit 5 decreases as the matching degree decreases. In the case of FIG. 3A, since the degree of phase matching between the reference signal and the received signal is low, the value of the correlation output becomes small. In the case of FIG. 3B, the phase of the reference signal and the received signal matches, so that the correlation output The value of is the maximum. Thus, according to the correlation processing, the signal detection is performed by taking not only the signal level information but also the phase information by the product-sum operation, so that the signal detection accuracy is improved compared to the case where the signal detection is performed based only on the level. Can be increased.

  By performing the correlation process as described above, a received signal corresponding to the reference signal as shown in FIG. 2C is extracted from the matched filter. This reception signal is a burst signal similar to the transmission signal, but is composed only of a signal in the same band (for example, near 38 KHz) as the reference signal, and signals in other bands are cut. That is, the time width (pulse width) T2 of the reception signal is shorter than the time width (pulse width) T1 of the transmission signal. In this way, as a result of correlation processing by the matched filter, the received signal output from the correlation processing unit 5 is pulse-compressed, so that the resolution of the echo is improved, and the single fish is accurately separated by the single separation unit 6 described below. Can do. Note that the output signal of the matched filter shown in FIG. 2C actually includes a signal of a very small level over the same section as T1 in a section other than T2, but this signal is practically used. Since it can be ignored, it can be considered that the pulse width is actually compressed from T1 to T2.

  For example, when the carrier frequency is 38 KHz, when the conventional continuous wave has 10 pulses in one pulse section and the FM wave of the present invention (frequency sweep width 3.8 KHz), the one pulse section has 1000 waves. The resolution is the same. Therefore, when the SN ratio of 10 waves and 1000 waves is compared, it can be seen that 1000 waves are improved by 10 log (1000/10) = 20 dB, and the detection distance is extended by adopting the method of the present invention.

  In FIG. 2, the level of the FM transmission signal is constant over the time width T1, but the effect of side lobes on the received signal by performing envelope processing using an appropriate window function, for example, a Hanning window. Can be suppressed.

  The reception signal pulse-compressed by the correlation processing unit 5 is given to the single separation unit 6. The single separation unit 6 analyzes the reception signal and detects the reception signal of the single fish. This principle will be described with reference to FIG. FIG. 4 shows the envelope waveform of the received signal extracted by the correlation processing unit 5.

  In the present embodiment, it is determined whether or not it is a single fish based on the amplitude and time width of the received signal. That is, when both of the following two conditions are satisfied, it is determined that the fish is a single fish.

The first condition is that the amplitude of the received signal is greater than or equal to the threshold value P in FIG. The second condition is that the time width near the peak value of the received signal is within a certain range. That is, in FIG.
T−τ <t <T + τ (5)
Is to satisfy. Here, t is a time width at a level lower than the peak value of the amplitude of the received signal by a certain level α, T is a time width of the reference signal in the matched filter (corresponding to T2 in FIG. 2C), and τ is T The adjustment time width is determined in advance according to the value. The adjustment time width τ can be arbitrarily set by the user. A waveform W1 in FIG. 4 is a waveform of a reception signal of a single fish and satisfies the first and second conditions. The waveform W2 is a waveform of a received signal by echoes from floating substances other than fish, and the peak value of the amplitude is smaller than the threshold value P and does not satisfy the first condition. A waveform W3 is a waveform of a reception signal by echoes from a plurality of fish that form a flock, and the peak value of the amplitude is larger than the threshold value P, but the time width of the signal is long and the second condition is the expression (5) Because it does not satisfy, it is distinguished from single fish.

  In this way, in this embodiment, since it is determined whether or not it is a single fish from the two conditions of the amplitude and time width of the received signal, it is possible to reliably detect a single fish and to improve the accuracy of single separation. Can be improved.

である。また、（７）式のａ、ｂ、ｃは送受波器１の指向特性より算出される係数である。このように、反射強度ＴＳの計算にあたっては、受信信号の位相差から得られるターゲットの方位（エコー到来角）に応じて補正された反射強度ＴＳが算出される。そして、反射強度ＴＳが求まると、前記（１）式により魚体長Ｌが算出される。また、データ演算部７は、魚体長のほか、受信信号に基づいて魚群の分布状態も算出する。 The data of the reception signal of the single fish analyzed by the single separation unit 6 is sent to the data calculation unit 7. The data calculation unit 7 first calculates the reflection intensity TS based on the data obtained from the single separation unit 6, and then calculates the fish body length from the reflection intensity TS. It is known that the reflection intensity TS is calculated by the following equation.
TS = 20 log ₁₀ (SIG) -G + TVG + Bt (θr, θp)
+ Br (θr, θp) −SL−Me (6)
Here, SIG is the level of a received signal of a single fish, G is a reception gain, TVG is a variable time gain that varies depending on the distance to the target, Bt (θr, θp) is a transmission directivity correction term depending on the target direction, Br (Θr, θp) is a correction term for the reception directivity according to the target orientation, θr is the orientation of the target in the roll direction, θp is the orientation of the target in the pitch direction, SL is the level of the transmission signal, and Me is the received sound pressure sensitivity. The directivity correction terms Bt (θr, θp) and Br (θr, θp) are calculated by the following equations.
y = −ax ³ −bx ² −cx (7)
here,

It is. Further, a, b, and c in the equation (7) are coefficients calculated from the directivity characteristics of the transducer 1. Thus, in calculating the reflection intensity TS, the reflection intensity TS corrected in accordance with the target direction (echo arrival angle) obtained from the phase difference of the received signals is calculated. When the reflection intensity TS is obtained, the fish length L is calculated by the above equation (1). In addition to the fish body length, the data calculation unit 7 also calculates the distribution state of the school of fish based on the received signal.

  Next, the display control unit 8 generates display data for displaying the calculated fish length L data in a graph and display data for displaying a fish school image. The display control unit 8 outputs these data to the display unit 9 and displays the data on the screen of the display unit 9. FIG. 5A shows a display example on the screen 9 a of the display unit 9. On the screen 9a, a fish length graph 32, a single fish mark 33, a water depth scale 35, and the like are displayed along with underwater images such as a fish school image 31 and a water bottom image 34. The fish school image 31 is an image obtained based on the ultrasonic echo reflected by the fish, and is displayed by being divided into colors according to the strength of the echo.

  The fish body length graph 32 is a bar graph representing the frequency distribution of the fish body length, where the vertical axis represents the fish body length and the horizontal axis represents the distribution ratio. A number “645” indicated by 36 in the graph indicates the total number of single fish detected. The fish body length graph 32 represents the body length distribution of fish existing within the range of the frame 37 shown on the screen 9a. The frame 37 is movable and variable in size by an operation on an operation unit (not shown). By designating a range with the frame 37, the fish length graph 32 in an arbitrary range can be displayed. When the frame 37 is not displayed, the fish length graph 32 for the fish existing in the entire range of the screen 9a is displayed.

  The single fish mark 33 is a mark displayed corresponding to the position of each single fish based on the reception signal of the single fish detected by the single separation unit 6, and one “+” mark represents one single fish. Represents. In the figure, for the sake of convenience, the single fish mark 33 is drawn sparsely, and the size of the mark is exaggerated, but actually, this mark 33 is displayed as densely as the number of single fish, and the size is very small. ing. As can be seen from FIG. 5A, the single fish mark 33 tends to be displayed concentrated on the periphery of the fish school image 31. This is because it becomes more difficult to separate a single fish toward the center of the school of fish. However, in the conventional measuring fish finder, since such a single fish mark 33 was not displayed, it was impossible to determine in which part of the fish group the single fish was separated. For example, when single separation is performed inside a dense fish school, a plurality of targets are measured as one target, so that an error in measuring the fish length increases. In this case, the reliability of data obtained by measuring the fish length can be determined if the target separated by itself can be confirmed on the video, but since such video is not displayed on the screen in the past, this determination is not possible. It was possible. However, when the single fish mark 33 is displayed in correspondence with the position of each single fish, for example, as shown in FIG. 5A, when a large number of single fish marks 33 are displayed at the periphery of the school of fish that can be easily separated. This is evidence that the single unit separation is normally performed, and it can be determined that the reliability of the data of the fish length graph 32 is high. On the other hand, when a large number of single fish marks 33 are displayed at the center of the school of fish that should not be separable from each other, the single segregation is not performed normally, and the reliability of the data of the fish length graph 32 is not achieved. Can be judged as low.

  In FIG. 5A, all detected single fish marks 33 are displayed in the frame 37, but the range of the fish length is selected, and only the single fish mark 33 belonging to the selected fish length range is displayed. May be. FIG. 5B shows an example of the screen 9a in this case. In FIG. 5B, reference numeral 38 denotes a cursor as selection means displayed on the screen 9a, which can be moved up and down by an operation on the operation unit. Here, 35 to 45 cm is selected as the fish length range by the cursor 38, and only a single fish mark 33 having a fish length of 35 to 45 cm is displayed in the frame 37 of the screen 9 a. According to this embodiment, it can be known at a glance to which region a single fish of a certain size is distributed. In addition, when a large number of single fish marks 33 are displayed in the center of the school of fish, the fish 38 is narrowed down to a small range with the cursor 38, and data that has been processed by mistake as many fish in the center of the school of fish. Can be removed so that the single fish mark 33 is not displayed in the center of the school of fish. This makes it possible to obtain highly reliable fish length data.

  Moreover, you may make it display the mark from which a display mode differs according to the magnitude | size (fish body length) of a single fish. An embodiment in this case is shown in FIG. 5C. In (a), the size of the single fish mark 33 is varied according to the size of the fish. Moreover, in (b), the kind of the single fish mark 33 is varied according to the size of the fish. In addition, a method of changing the color or luminance of the single fish mark 33 according to the size of the single fish is also conceivable. Even in this way, it is possible to know at a glance which region a single fish of a certain size is distributed.

  FIG. 6 is a flowchart showing the operation of the weighing fish finder 100 described above. In step S1, based on the FM signal waveform generated by the FM transmission waveform generation unit 4, an FM transmission signal having a time width T1 as shown in FIG. In step S2, the transmitter / receiver 1 receives the echo reflected by the target and returning. In step S3, the received signal of FIG. 2B is subjected to correlation processing by a matched filter in the correlation processing unit 5, and a received signal having a time width T2 as shown in FIG. In step S4, according to the method of FIG. 4, the extracted reception signal is analyzed by the single separation unit 6, and the reception signal of the single fish is detected. In step S5, the data calculation unit 7 calculates the reflection intensity TS according to equation (7) based on the data of the reception signal of the single fish. In step S6, the data calculation unit 7 calculates the fish body length based on the reflection intensity TS using the equation (1). In step S <b> 7, the display control unit 8 generates display data such as the fish length graph 32 and the fish school video 31. In step S8, display as shown in FIGS. 5A and 5B is performed on the screen 9a of the display unit 9 by the data generated by the display control unit 8. FIG.

  In the embodiment described above, an example in which correlation processing is performed using a matched filter has been described. However, correlation processing may be performed using means other than the matched filter.

  In the above embodiment, a signal whose frequency gradually decreases with time is used as the FM signal, but a signal whose frequency gradually increases with time can also be used.

In addition, each embodiment regarding the display of the single fish mark 33 described with reference to FIGS. 5A to 5C is only an FM type measurement fish finder including the FM transmission waveform generation unit 4 and the correlation processing unit 5 as illustrated in FIG. In addition, it can be applied to a general measuring fish finder (for example, FIG. 7). In this case, the following embodiment can be considered.
(1) Transmitting ultrasonic waves into the water, analyzing the echoes of the ultrasonic waves that come back after being reflected by the fish, and detecting the single fish, calculating the fish length of the single fish, and calculating the calculated fish body length data Is displayed on the screen together with an underwater image, a mark representing a single fish is displayed on the screen in correspondence with the position of each single fish.
(2) A transmitter / receiver that transmits ultrasonic waves underwater and receives ultrasonic echoes reflected back from the fish, and a single unit that detects a received signal of a single fish from the received signals received by the transmitter / receiver A measuring fish finder comprising: separation means; computing means for calculating a fish body length from a reflection intensity obtained based on a reception signal of the single fish; and display means for displaying data on the fish body length calculated by the computing means The display means displays on the screen a mark representing the single fish in correspondence with the position of each single fish based on the reception signal of the single fish detected by the single fish separation means.
(3) In the measurement fish finder of (1) or (2), the measuring fish finder includes selection means for selecting a fish length range on the screen, and only a single fish mark belonging to the fish length range selected by the selection means Is displayed on the screen.
(4) In the measuring fish finder according to any one of (1) to (3), the mark is displayed in a different display mode according to the size of a single fish.

It is the electric block diagram which showed embodiment of the measurement fish finder based on this invention. It is a wave form diagram of the signal in the measurement fish finder of the present invention. It is a figure explaining the principle of the correlation process using a matched filter. It is a figure explaining the principle of the correlation process using a matched filter. It is a figure explaining the principle of single-piece | unit separation. It is an example of a display on the screen of a display part. It is another example of a display in the screen of a display part. It is another example of a display in the screen of a display part. It is the flowchart which showed the operation | movement of the measurement fish finder of this invention. It is an electric block diagram of the conventional measurement fish finder. It is the flowchart which showed the operation | movement of the conventional measurement fish finder. It is a wave form diagram of the transmission signal in the conventional measurement fish finder. It is a figure explaining the direction detection principle in a split beam type measurement fish finder.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Transmitter / receiver 3 Operation processing part 4 FM transmission waveform generation part 5 Correlation processing part 6 Single-unit separation part 7 Data operation part 8 Display control part 9 Display part 11 Ultrasonic wave 12 Echo 13 Fish (target)
21-24 Transmitting / Receiving Unit 31 Fish School Video 32 Fish Length Graph 33 Single Fish Mark 38 Cursor 100 Weighing Fish Detector CH1-CH4 Channel L Fish Length

Claims (11)

FM transmission signal generation means for generating a transmission signal having a time width T1 composed of an FM (frequency modulation) signal;
A transmission / reception wave having a channel divided into a plurality of parts, receiving an transmission signal generated by the FM transmission signal generation means, transmitting an ultrasonic wave in water, and receiving an ultrasonic echo reflected by a fish And
Correlation processing is performed by comparing the received signal received by the transducer with a predetermined reference signal, and a signal corresponding to the reference signal and having a time width T2 shorter than the time width T1 of the transmission signal is received. Correlation processing means for extracting a signal;
Analyzing the received signal extracted by the correlation processing means, and detecting a single fish received signal;
A calculation means for calculating the reflection intensity based on the reception signal of the single fish detected by the single separation means, and calculating the fish body length from the obtained reflection intensity;
Display means for displaying the fish length data calculated by the computing means;
Weighing fish finder characterized by having. The measuring fish finder according to claim 1,
The correlation processing means comprises a matched filter, calculates the degree of coincidence between the received signal received by the transducer and the reference signal by a product-sum operation, and extracts the received signal having the time width T2 based on the calculation result. Weighing fish finder characterized by that. In the measuring fish finder according to claim 1 or 2,
The single unit separating means determines that the received signal is due to a single fish when the amplitude of the received signal is a certain level or more and the time width near the peak value is within a certain range. Fish finder. In the measurement fish finder according to any one of claims 1 to 3,
The measuring fish finder according to claim 1, wherein the display means displays on the screen a mark representing a single fish corresponding to the position of each single fish based on the reception signal of the single fish detected by the single fish separation means. In the measurement fish finder according to claim 4,
Comprising a selection means for selecting a range of fish length on the screen;
The measuring fish finder according to claim 1, wherein the display means displays only a single fish mark belonging to the range of the fish body length selected by the selection means on the screen. In the measurement fish finder according to claim 4 or 5,
The weighing fish finder according to claim 1, wherein the display means displays the mark in a different display mode according to the size of a single fish. Applying a transmission signal having a time width T1 composed of FM signals to a transducer having a plurality of divided channels, and transmitting ultrasonic waves from the transducer into the water;
Receiving ultrasonic echoes reflected back from the fish at the transducer; and
Correlation processing is performed by comparing the received signal received by the transducer with a predetermined reference signal, and a signal corresponding to the reference signal and having a time width T2 shorter than the time width T1 of the transmission signal is received. Extracting a signal;
Analyzing the received signal extracted by the correlation process to detect a received signal of a single fish;
Calculating the reflection intensity based on the received signal of the single fish and calculating the fish length from the obtained reflection intensity;
A fish length measuring method comprising: By transmitting ultrasonic waves into the water and analyzing the echoes of the ultrasonic waves that are reflected back from the fish, the single fish is detected, the body length of the single fish is calculated, and the calculated fish length data is displayed in the underwater image. In the measuring fish finder that is displayed on the screen with
A measuring fish finder, wherein a mark representing a single fish is displayed on the screen in association with the position of each single fish. A transmitter / receiver that transmits ultrasonic waves underwater and receives echoes of ultrasonic waves reflected back from the fish, and a single separation means for detecting a received signal of a single fish from the received signals received by the transmitter / receiver; In the measuring fish finder provided with a calculation means for calculating the fish length from the reflection intensity obtained based on the reception signal of the single fish, and a display means for displaying the data of the fish length calculated by the calculation means,
The measuring fish finder according to claim 1, wherein the display means displays on the screen a mark representing a single fish corresponding to the position of each single fish based on the reception signal of the single fish detected by the single fish separation means. In the measurement fish finder according to claim 8 or 9,
A measuring fish finder having a selection means for selecting a fish length range on the screen, and displaying only a single fish mark belonging to the fish length range selected by the selection means on the screen. In the measuring fish finder according to any one of claims 8 to 10,
A measuring fish finder that displays the mark in a different display mode according to the size of a single fish.

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