JP2009204508A - Underwater sensor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an underwater sensor, sensing a fish school near the water surface without being influenced by a tailing signal, and displaying an echo from the bottom of the sea and an echo from the fish school distributed to a depth away from the water surface which is not affected by the tailing signal in a color which corresponds to the original signal strength. <P>SOLUTION: This underwater sensor includes a tailing signal removing range control part 12 for optimally controlling the depth range to which the tailing signal removal processing is conducted, and tailing signal removal processing in a tailing signal removing part 6 is limited to the depth range affected by the tailing signal. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an underwater detection apparatus using ultrasonic waves such as a fish finder or an acoustic sounding instrument mounted on a ship.

  The underwater detection device emits ultrasonic waves from the transducer attached to the hull to the water, receives the echoes that are reflected from the fish school and the bottom of the water, and displays the underwater information. Equipment. For example, in the case of a fish finder, echoes from the water are displayed on the display unit with different colors according to the signal intensity. As an example, a strong echo returning from a school of fish having a high reflection intensity or a bottom of the water is displayed in reddish brown, and a weak echo returning from a school of fish having a low reflection intensity is displayed in blue or green.

  In such an underwater detection apparatus, since both transmission and reception operations are performed by one transducer, an unnecessary signal such as ringing appears immediately after transmitting an ultrasonic wave. Hereinafter, this signal is referred to as a “tail signal”. FIG. 7 is a diagram for explaining the trailing signal. FIG. 7A shows a signal waveform of an ultrasonic wave transmitted from the transmitter / receiver, where a transmission signal indicated by a solid line is followed by a trailing signal indicated by a broken line. This tailing signal is generated due to reflection of the transmission signal in the transducer and the frequency characteristics of the band-limited element. FIG. 7B shows a signal waveform received by the transducer. Transmission / reception at the transducer is switched by the transmission / reception switching unit, but the transmission signal leaks from the transmission / reception switching unit to the reception circuit because the power of the transmission signal is very large. For this reason, a signal having the same waveform as that of the transmission signal appears in the reception signal, as indicated by a one-dot chain line in FIG. The broken line is the above-described tail signal immediately after transmission, and the solid line is the echo signal reflected by the target in water.

  When the tail signal as described above is generated, the tail signal video 24 appears on the screen 8a of the display unit as shown in FIG. 20a and 20b are fish school images, 21 is a water bottom image, 22 is a water depth scale, and 23 is an oscillation line indicating an ultrasonic wave transmission position. Here, the image 24 of the tail signal is a striped color image composed of, for example, three layers of reddish brown, yellow, and blue in order from the top. For this reason, the image 20b of the surface fish school near the water surface is covered with the image 24 of the tail signal, making it difficult to see. In some cases, the image 20b of the surface fish school is completely hidden and may not be visible.

  As a countermeasure against this, the present applicant has proposed an underwater detection device that can detect a school of fish near the water surface without being affected by a tailing signal in Japanese Patent Application Laid-Open No. 2006-170926.

The underwater detection device of Patent Document 1 is provided with a tail signal removal unit that removes a tail signal from a received signal including a tail signal and an echo signal so that a school of fish close to the water surface can be detected. As shown in FIG. 2, when the received signal at the same sampling point Sn is arranged in time series for a plurality of transmission / reception periods, the tail signal removal unit of the underwater detection device of Patent Document 1 As shown in FIG. 2 (b), the sampling values randomly change at every transmission as shown by a1, a2, a3, and a4. Focusing on the fact that it can be regarded as a steady state with little fluctuation, it is configured to remove the tail signal by a low-pass filter or a high-pass filter. (Δt in FIG. 2 indicates the sampling interval.)

JP 2006-170926 A

  However, the underwater detection device described in Patent Document 1 has an excellent effect of removing a tail signal and detecting a school of fish near the water surface, but has the following problems.

First, there is a problem that the image of the seabed (21 in FIG. 8) is displayed in a color different from normal. Since the echo from the seabed contains a certain amount of stationary component, the tail signal removal unit removes the stationary component of the echo from the seabed, resulting in a weakening of the signal strength of the echo from the seabed. The seabed will be displayed in a different color. The fisherman determines and uses the bottom of the seabed (for example, whether the seabed is rock or sand) based on the image of the seabed of the underwater detection device. Then, the image of the seabed that should be displayed in a color corresponding to a strong echo would be displayed in a color corresponding to a weak echo, and the fisherman may make a mistake about the bottom sediment quality .

Secondly, since the echo from the fish school also includes a certain amount of steady component, the underwater detection device described in Patent Document 1 is distributed in the depth range away from the water surface and is not affected by the tail signal. There is a problem that the signal intensity of the echo from the fish school (20b in FIG. 8) is weakened by removing the stationary component by the action of the tail signal removal unit. The fisherman uses the signal strength of echoes from each fish school in the water, that is, the display color of the fish school, to judge the fish quantity of the fish school. In the underwater detection device described in Patent Document 1, the echo from the fish school Even if it is a strong echo, it will be displayed in a color corresponding to a weaker signal, and there is a risk that the fisherman will misjudg the fish quantity of the fish school. In addition, when the echo from the school of fish is originally weak, it may not be displayed as an image and the school of fish may be missed.

The present invention has been made to overcome the above-mentioned problems of the prior art, can detect a school of fish near the water surface without being affected by the tail signal, and echo from the seabed, For the purpose of providing an underwater detection device capable of displaying echoes from a school of fish distributed in a depth range away from the surface of the water that is not affected by a tail signal in a color corresponding to the original signal intensity. Yes.

The underwater detection device of the present invention emits an ultrasonic wave into water based on a transmission signal output from the transmission unit and a transmission signal given from the transmission unit, and receives an echo reflected in the water and converts it into an electrical signal. A transmitter / receiver, an electric signal converted by the transmitter / receiver to extract a received signal in a predetermined frequency band, and an A / A for converting the received signal extracted by the receiver to a digital signal Digital conversion is performed by the D conversion unit, a tailing signal removal range control unit that determines a processing range for performing the trailing signal removal processing based on predetermined information, and outputs a control signal related to the processing range, and the A / D conversion unit A tailing signal removal unit that outputs the received signal by executing a tailing signal removal process based on a control signal output from the tailing signal removal range control unit, and a signal output from the tailing signal removal unit Signal A detection unit for performing a detection process is characterized by comprising: a display processing unit that generates a display signal based on the signal output from the detection section, the.

In the embodiment of the present invention, the information for determining the processing range in which the tailing signal processing in the tailing signal removal range control unit is to be performed is information regarding the pulse length and / or frequency of the transmission signal. It is desirable to include.

In the embodiment of the present invention, the information for determining the processing range in which the tailing signal processing is to be performed in the tailing signal removal range control unit may include information on the type of transducer.

  According to the present invention, it is possible to detect a school of fish near the water surface without being affected by the tailing signal, and it is distributed in a depth range away from the water surface which is not affected by the echo from the seabed or the tailing signal. An underwater detection device capable of displaying echoes from a fish school in a color corresponding to the original signal intensity is realized.

FIG. 1 is a block diagram of a fish detector 100 which is an embodiment of the underwater detector according to the present invention. 1 is a transmitter / receiver that emits ultrasonic waves into the water and receives echoes reflected in the water and converts them into electrical signals. 2 is a transmission / reception switching unit that switches the operation of the transmitter / receiver 1 between transmission and reception. Is a transmission circuit (transmission unit) that outputs a transmission signal of a predetermined frequency and a predetermined pulse length to the transmitter / receiver 1, 4 receives an electrical signal converted by the transmitter / receiver 1, and extracts a reception signal of a predetermined frequency band A receiving circuit (receiving unit). 5 is an A / D converter (A / D converter) that samples the received signal taken out by the receiving circuit 4 at a predetermined time interval and converts it into a digital signal, and 12 is based on the transmission frequency, the transmission pulse length, etc. A trailing signal removal range control unit that determines a depth range (processing range) in which the trailing signal removal process is to be performed, and 6 indicates a trailing signal included in the received signal for the depth range determined by the trailing signal removal range control unit 12. A trailing signal removing unit that removes and outputs the received signal as it is for other depth ranges, 7 is a detection circuit (detecting unit) that performs a detection process on the echo signal output from the trailing signal removing unit 6, 8 Is a display unit (display processing unit) that generates a display signal based on the output signal of the detection circuit 7 and displays underwater information. The display unit 8 may be provided integrally with the main body of the fish finder 100 or may be provided separately. In the latter case, the display unit 8 is connected to the main body of the fish finder 100 via a network such as a LAN.

  The trailing signal removal range control unit 12 determines a depth range (processing range) to be subjected to the trailing signal removal processing based on the transmission frequency, the transmission pulse length, and the like of the transmission signal. The tail signal removal processing is performed for the depth range, the tail signal removal processing is not performed for the other depth ranges, and the control signal is output so that the input from the A / D converter 5 is output as it is.

In general, the following can be said about the range of the trailing signal. First, as for the start position of the tailing signal, the start of the tailing signal is delayed as the transmission pulse length increases at the position where the transmission pulse ends. Also, the length (duration) of the tail signal is determined by the characteristics of the transducer and system (transmission / reception circuit) that constitute the transducer, and depends on the type of transmission / reception device and the transmission frequency.

The relationship between the transmission frequency, the transmission pulse length, and the processing range is obtained experimentally in advance and stored in the memory 13 in the trailing signal removal range control unit 12. The trailing signal removal range control unit 12 acquires information on the transmission pulse length of the transmission signal and the transmission frequency according to the detection range set by the user in a setting unit (not shown), and stores the information in the memory 13. Based on the relationship between the transmission pulse length, the transmission frequency, and the processing range, the processing range for performing the trailing signal removal process is determined.

The data for determining the processing range stored in the memory 13 may be data corresponding to the type of transmitter / receiver (unique ID number of the transmitter / receiver) in addition to data corresponding to the transmission pulse length and transmission frequency. good. In this way, the tail signal removal range control unit 12 performs each transmission / reception based on information on the transmitter / receiver 1 acquired by a predetermined means such as manual input or a known automatic identification function of the transmitter / receiver. The processing range corresponding to the device can be set, and the tail signal removal processing can be appropriately executed even when the transducer is replaced.

Further, when a tailing signal due to reflection at the bottom of the ship is generated due to the installation state of the transducer 1, the processing range stored in the memory 13 is fixed at a short distance regardless of the transmission frequency and the transmission pulse length, for example. It should be set to a specific range. In addition, the setting of the removal range of the trailing signal may be appropriately adjusted by the user by the setting unit.

Note that the signal is often saturated during the period in which the transmission signal leaks into the receiving unit (the portion indicated by the alternate long and short dash line in FIG. 7B). It is difficult to extract the signal. Whether or not to include this part in the tailing signal processing range is arbitrary, but if this part is excluded from the tailing signal removal processing range, the circuit scale of the tailing signal removal unit 6 can be reduced, which is advantageous in terms of cost. is there.

In the present embodiment, the trailing signal removal unit 6 includes a low-pass filter 9 and a difference calculator 10. The low-pass filter 9 is composed of an FIR filter or an IIR filter, and outputs from the A / D converter 5 for a received signal belonging to a depth range for performing the trailing signal removal processing given from the trailing signal removal range control unit 12. Whether the tail signal and echo signal included in the received signal are superimposed, and only the tail signal is extracted and output, and the operation is stopped for the depth range where the tail removal process is not performed. A signal with a signal strength of 0 is output. Then, the difference calculator 10 calculates and outputs the difference between the output of the A / D converter 5 and the output of the low pass filter 9.

Next, the operation of the fish finder 100 of FIG. 1 will be described. When a transmission signal having a predetermined pulse length and a predetermined frequency output from the transmission circuit 3 is applied to the transmitter / receiver 1 via the transmission / reception switching unit 2, the transducer (not shown) of the transmitter / receiver 1 is driven, Sound waves are launched into the water. The emitted ultrasonic wave is reflected by a target such as an underwater fish school or the bottom of the water, and is received by the transducer 1 as an echo. The transducer 1 converts the received echo into an electrical signal and outputs it to the receiving circuit 4 via the transmission / reception switching unit 2. The receiving circuit 4 amplifies the input signal and extracts a signal in a predetermined frequency band. The reception signal output from the reception circuit 4 is given to the A / D converter 5.

  The A / D converter 5 samples the output signal of the receiving circuit 4 at a predetermined time interval in synchronization with the transmission signal, and converts (quantizes) it into a digital signal. The reception signal digitally converted by the A / D converter 5 is input to the trailing signal removal unit 6. In the trailing signal removal unit 6, the following processing is performed.

  The received signal input to the trailing signal removal unit 6 is input to the low-pass filter 9 and also input to the difference calculator 10. The low-pass filter 9 performs low-pass filter processing independently for each sampling point of equal depth over a plurality of transmissions / receptions belonging to the depth range where the tailing signal processing is performed based on the instruction of the trailing signal removal range control unit 12. The sampling point belonging to the depth range not subjected to the trailing signal removal process is stopped without being processed, or a signal corresponding to a signal intensity of 0 is output.

FIG. 3 shows a specific configuration example of the low-pass filter 9. 30 is a filter element provided corresponding to each sampling point, 31 is a selection circuit for selecting one of the plurality of filter elements 30, and 32 is one of the plurality of filter elements 30 or a signal having a signal strength of 0 is stored. This is a selection circuit for selecting one from the memory 33. Sampling data belonging to the depth range for which the tailing signal removal processing is performed is input to one of the filter elements 30 corresponding to each sampling point by the selection circuit 31 and subjected to low-pass filter processing (for example, moving average processing). Output from the selection circuit 32. As a result, the trailing signal component is extracted from the data in the depth range to be subjected to the trailing signal removal process. When sampling point data that does not belong to the trailing signal removal range is input, the selection circuit 32 selects the memory 33 and the low-pass filter 9 outputs data corresponding to a signal strength of 0.

Note that it is not necessary to provide the filter elements 30 for all the sampling points, and it is only necessary to provide as many filter elements 30 as necessary for the trailing signal removal process. As a result, the circuit scale of the trailing signal removal unit 6 can be reduced, and the product cost can be reduced.

  The signal output from the trailing signal removal unit 6 is given to the detection circuit 7. In the detection circuit 7, the envelope data of the echo signal is extracted by a known detection process. The output of the detection circuit 7 is sent to the display unit 8. In the display unit 8, a display signal is generated, and underwater information such as a fish school image based on the echo signal is displayed on the display screen in a color corresponding to the signal intensity.

  FIG. 4 shows an example of underwater information displayed on the screen 8 a of the display unit 8. 20a and 20b are fish school images based on echoes reflected from the fish school, 21 is a water bottom picture based on echoes reflected at the bottom of the water, 22 is a water depth scale, and 23 is an oscillation line indicating the transmission position of the ultrasonic waves. In the present invention, since the tail signal is removed by the tail signal removal unit 6 in the depth range where the tail signal processing is performed, the image 24 of the tail signal in FIG. 8 does not appear in FIG. Therefore, the image 20b of the surface fish school near the water surface is clearly displayed. In addition, the seabed 21 and the school of fish 20a away from the water surface are displayed in a color corresponding to the original signal intensity, and are used for judgment of the seabed sediment and the quantity of fish.

  FIG. 5 is a block diagram of a fish finder 200 according to another embodiment of the present invention. In the figure, the same parts as those in FIG. In the present embodiment, the trailing signal removal unit 6 is configured by a high-pass filter 11 instead of the low-pass filter 9 and the difference calculator 10 of FIG. The rest of the configuration is the same as in FIG. The high-pass filter 11 includes an FIR filter and an IIR filter. Based on the control signal given from the trailing signal removal range control unit 12, the high-pass filter 11 applies A / For a depth range in which the tail signal is output by removing the tail signal from the received signal on which the tail signal and the echo signal are superimposed, which is output from the D converter 5, and the tail signal is not removed. The received signal is output as it is.

FIG. 6 shows a specific configuration example of the high-pass filter 11. Reference numeral 40 denotes a filter element provided corresponding to each sampling point, and reference numerals 41 and 42 denote selection circuits for selecting one of the plurality of filter elements 40 or a path 43 through which the received signal passes. The sampling data in the depth range for which the tailing signal removal process is performed is input to one of the filter elements 40 corresponding to each sampling point by the selection circuit 41, subjected to a high-pass filter process, and then output from the selection circuit 42. As a result, the tail signal is removed from the data in the depth range to be subjected to the tail signal removal process. When sampling point data that does not belong to the trailing signal removal range is input, the selection circuits 41 and 42 select the path 43 through which the received signal passes, and the high-pass filter 11 outputs the received signal as it is. The

Note that it is not necessary to provide the filter elements 40 for sampling points at all depths. As a result, the circuit scale of the trailing signal removal unit 6 can be reduced, and the product cost can be reduced.

In the above embodiment, the case where the present invention is applied to a fish finder has been described as an example. It can be applied to various underwater detection devices such as a net recorder.

It is a block diagram of the fish finder which is one Embodiment of this invention. It is the figure which showed the waveform of the signal input into a receiving circuit. It is the figure which showed the specific structure of the low-pass filter. It is an example of the underwater information displayed on a display part. It is a block diagram of the fish finder by other embodiments of the present invention. It is the figure which showed the specific structure of the high pass filter. It is a figure explaining a tailing signal. It is an example of the underwater information displayed on the display part of the conventional fish finder.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Transmitter / receiver 2 Transmission / reception switching part 3 Transmission circuit 4 Reception circuit 5 A / D converter 6 Trailing signal removal part 7 Detection circuit 8 Display part 9 Low pass filter 10 Difference calculator 11 High pass filter 12 Trailing signal removal range control part 30, 40 Filter element 31, 32, 41, 42 Selection circuit 100, 200 Fish finder

Claims (3)

A transmission unit that outputs a transmission signal;
A transmitter / receiver that emits ultrasonic waves into water based on a transmission signal given from the transmitter, receives echoes reflected in water, and converts them into electrical signals;
A receiving unit that processes the electrical signal converted by the transducer and extracts a received signal in a predetermined frequency band;
An A / D converter that converts the received signal extracted by the receiver into a digital signal;
A tailing signal removal range control unit that determines a processing range for performing a tailing signal removal process based on predetermined information and outputs a control signal related to the processing range;
A tailing signal removal unit that executes a tailing signal removal process on the basis of a control signal output by the tailing signal removal range control unit with respect to the reception signal digitally converted by the A / D conversion unit;
A detection unit that performs detection processing on the signal output from the trailing signal removal unit;
An underwater detection device comprising: a display processing unit that generates a display signal based on a signal output from the detection unit. The underwater detection device according to claim 1,
The underwater detection device characterized in that the predetermined information includes information related to a pulse length and / or a frequency of the transmission signal. In the underwater detection device according to claim 1 or 2,
The underwater detection device, wherein the predetermined information includes information related to a type of the transducer.

Images