JP6078246B2 - Underwater detection device, underwater detection method, and underwater detection program - Google Patents

Description

  The present invention relates to an underwater detection device that transmits an ultrasonic pulse signal in water and generates underwater detection data from echoes of a school of fish and echoes of the sea bottom.

  In a fish finder which is one of the underwater detection devices, an improvement in detection distance is required so that a fish school at a deeper depth can be detected. In order to extend the detection distance, it is preferable to increase the pulse length (transmission pulse length) of the ultrasonic pulse signal. However, if the transmission pulse length is increased, the reflected echo from a target such as a school of fish or the seabed also becomes longer, and the distance resolution of the underwater detection data decreases.

  As a means for suppressing the decrease in distance resolution, for example, in Patent Document 1, the ultrasonic pulse signal is frequency-modulated, and the correlation processing between the received echo signal and the replica waveform of the transmitted ultrasonic pulse signal is performed. Thus, means for pulse-compressing a received signal based on an echo signal is described. As a result, the pulse length of the received signal is shortened, so that a decrease in distance resolution can be suppressed even if the pulse length of the ultrasonic pulse signal is increased.

JP 2005-249398 A

  FIG. 14 is a diagram illustrating a time waveform (a waveform along the depth direction) of a received signal reflected by a target when pulse compression is used.

  However, when pulse compression is used, as shown in FIG. 14, the received signal obtained by reflection on the target has a high-level main lobe generated at the position of the target and Thus, false images called range side lobes are generated at positions before and after in the time direction (depth direction).

  In particular, when a range sidelobe is generated by a target with a very high echo signal level, such as the sea floor, an underwater detection image in which a target with a low signal level exists in the vicinity of the target with a high signal level. End up. Thereby, the false image by the range side lobe may be mistaken for a detection target such as a school of small fish. In addition, the range side lobe results in a detection image in which a target whose signal level is relatively high in the range side lobe does not appear. As a result, the bottomed school of fish near the seabed cannot be visually recognized on the detection image.

  An object of the present invention is to realize an underwater detection apparatus that suppresses a range side lobe caused by a target having a high signal level of an echo such as the seabed and generates detection data with higher accuracy.

  The present invention provides a pulse compression unit that generates a pulse compression signal by pulse-compressing a received signal obtained from a reflection echo of a frequency-modulated ultrasonic pulse signal, and performs detection by performing range sidelobe suppression processing on the pulse compression signal. The present invention relates to an underwater detection device including a range sidelobe suppression unit that generates data, and has the following characteristics. The range sidelobe suppression unit includes a suppression range setting unit, a suppression exclusion range setting unit, a suppression value setting unit, and a suppression calculation unit. The suppression range setting unit determines the suppression range based on the pulse compression signal. The suppression exclusion range setting unit uses the signal level of the pulse compression signal at a plurality of depth positions within a predetermined range deeper than the suppression range and the range sidelobe approximate waveform of the ultrasonic pulse signal to determine the exclusion range. Set the threshold. The suppression exclusion range setting unit determines the suppression exclusion range based on the comparison result between the threshold for determining the exclusion range and the signal level of the pulse compression signal. The suppression value setting unit determines the suppression value using the signal level of the pulse compression signal within the suppression range and the signal level of the pulse compression signal outside the suppression range. The suppression calculation unit performs a calculation to suppress the signal level of the pulse compression signal in the suppression range excluding the suppression exclusion range with the suppression value.

  In this configuration, the suppression exclusion range can be set appropriately, and the suppression range can be set appropriately even if the suppression exclusion range is included. As a result, the range side lobe suppression process can be appropriately executed in the range to be suppressed (range of the range side lobe only).

  Further, in the underwater detection device of the present invention, the suppression range setting unit has a pulse compression signal on the side shallower than the target position, where the signal level of the pulse compressed signal at the target position is not less than the first threshold based on the signal level of the main lobe. When the signal level is less than the first threshold value, the target position is set to the end point on the deep side of the suppression range. The suppression range setting unit sets the depth range of the suppression range from the ultrasonic pulse signal.

  In this configuration, the end point on the deep side of the suppression range can be detected only with two signal levels arranged in the depth direction, and the suppression range setting process can be simplified and speeded up.

  Further, in the underwater detection device of the present invention, when the suppression range setting unit detects a signal level higher than the signal level of the end point on the deep side of the suppression range within the suppression range, only the side deeper than the detection point is detected. To the suppression range.

  In this configuration, even if a large target (such as a school of fish) exists within the set detection range, the echo range of the large target is excluded from the suppression range. Thereby, the signal level of the echo of the large target is not suppressed while suppressing the range side lobe.

  In the underwater detection device of the present invention, the suppression exclusion range setting unit sets a threshold for determining the exclusion range from the representative value of the signal level of the pulse compression signal in the predetermined range deeper than the suppression range.

  In this configuration, since the threshold for determining the exclusion range is set according to the signal level of the pulse compression signal, the suppression exclusion range can be accurately detected.

  In the underwater detection device of the present invention, the suppression exclusion range setting unit has, as a representative value, a predetermined number of signals having a higher signal level out of the signal levels of the pulse compression signals in a predetermined range deeper than the suppression range. Use the average level.

  In this configuration, a specific means for setting the threshold for determining the exclusion range is shown. By using this means, the range side lobe is prevented from entering the suppression exclusion range, and the target echo range is excluded from the suppression. Can be set to ensure that the range is entered.

  In the underwater detection device of the present invention, the suppression value setting unit determines the suppression value using the signal level of the pulse compression signal within the suppression range and the signal level of the pulse compression signal outside the suppression range.

  In this configuration, the suppression value is determined from the signal level within the suppression range, that is, the signal level of the range side lobe, and the signal level outside the suppression range, that is, the noise level. Thereby, the suppression value which suppresses a range side lobe appropriately can be set.

  In the underwater detection device of the present invention, the suppression value setting unit obtains an offset value for setting the suppression value from the ratio between the signal level of the pulse compression signal within the suppression range and the signal level of the pulse compression signal outside the suppression range. Set. The suppression value setting unit determines a suppression value from the offset value and the range sidelobe approximate waveform of the ultrasonic pulse signal.

  In this configuration, it is possible to set a suppression value corresponding to the shape of the range side lobe for the reception state. Thereby, the range side lobe within the suppression range can be appropriately suppressed.

  In the underwater detection device of the present invention, the suppression value setting unit sets the offset value to the allowable maximum value when the offset value exceeds the allowable maximum value based on the main lobe.

  In this configuration, an upper limit can be set for the suppression value, thereby preventing an excessive suppression process from being performed.

  Further, in the underwater detection device of the present invention, the suppression value setting unit has one or more predetermined values when the signal level of the pulse compression signal within the suppression range is lower than the signal level of the pulse compression signal outside the suppression range. Set to the offset value.

  With this configuration, the offset value can be prevented from becoming unnecessarily small. At this time, an appropriate value close to 1 may be set. Thus, a lower limit can be set for the suppression value, and an appropriate suppression value can be set even when the external environmental noise is large.

  In the underwater detection device of the present invention, the range sidelobe approximate waveform is set by an exponential function based on the ultrasonic pulse signal.

  This configuration shows a specific setting example of the range sidelobe approximate waveform, and an appropriate approximate waveform can be set by using an exponential function.

  According to the present invention, it is possible to suppress only the range side lobe caused by a target having a high echo level and to generate highly accurate detection data.

1 is a configuration diagram of an underwater detection device 10 according to a first embodiment of the present invention. 3 is a block diagram showing a configuration of a range side lobe suppressing unit 70. FIG. It is a wave form diagram for demonstrating the setting means of a suppression range. It is a wave form diagram for demonstrating the setting means of a suppression exclusion range. It is a wave form diagram for demonstrating the setting means of a suppression value. It is a figure (waveform diagram) which shows the signal level of the pulse compression data along the depth direction after suppression calculation. It is a flowchart which shows the suppression method of the range side lobe of this embodiment. It is a flowchart which shows the setting flow of the suppression range Zone (s). It is a flowchart which shows the setting flow of suppression exclusion range ExZone (s). It is a flowchart which shows the setting flow of suppression value SS (i). It is a flowchart which shows the 2nd setting flow of suppression range Zone (s). It is a figure (waveform diagram) which shows the signal level of the pulse compression data along the depth direction before and after suppression when the second setting flow of the suppression range Zone (s) is used. It is a flowchart which shows the 2nd setting flow of suppression value SS (i). It is a figure which shows the time waveform (waveform along the depth direction) of the received signal obtained by reflecting on the target at the time of using pulse compression.

  An underwater detection device, an underwater detection method, and an underwater detection program according to a first embodiment of the present invention will be described with reference to the drawings. In this embodiment, a fish finder is shown as an example of the underwater detection device. However, the configuration of this embodiment can be applied to other underwater detection devices such as scanning sonar.

  FIG. 1 is a configuration diagram of an underwater detection device 10 according to the first embodiment of the present invention. The underwater detection device 10 includes a transmission unit 20, a transmission / reception switching unit 30, an AD conversion unit 40, a pulse compression unit 50, a detection unit 60, a range sidelobe suppression unit 70, a display processing unit 80, and a transducer 100.

  The transmission unit 20 generates a drive signal for transmitting an ultrasonic pulse signal from the transducer 100. The drive signal is generated so that the ultrasonic pulse signal has the following specifications. The ultrasonic pulse signal is composed of a predetermined carrier frequency and is composed of a transmission pulse length corresponding to the maximum detection distance (maximum detection depth). The carrier frequency is modulated so as to sweep within a predetermined frequency range in the pulse section. Yes.

  The transmission unit 20 outputs a drive signal to the transducer 100 via the transmission / reception switching unit 30 based on a preset transmission cycle.

  The transducer 100 is attached to the bottom of a ship, for example. The transducer 100 is excited by a drive signal and transmits an ultrasonic pulse signal STx. At this time, the transducer 100 transmits the ultrasonic pulse signal STx so that the vertical downward direction of the ship is the central direction of directivity and has a predetermined directivity angle.

  The transmitter / receiver 100 receives an echo signal ERx in which the ultrasonic pulse signal STx is reflected from the seabed 901 or an underwater fish (or school of fish) 902. The transducer 100 outputs a received signal to the AD conversion unit 40 via the transmission / reception switching unit 30.

  The AD conversion unit 40 samples the analog reception signal at a predetermined time interval and generates digital reception data. In general, a reception amplifier is disposed in front of the AD conversion unit 40. The reception amplifier performs amplification processing including TVG processing on the received signal.

  The pulse compression unit 50 performs cross-correlation processing between the received data and the replica waveform of the ultrasonic pulse signal, and generates and outputs pulse compression data (the “pulse compression signal” of the present invention). The detection unit 60 detects pulse compression data using a known detection method and outputs the pulse compression data to the range side lobe suppression unit 70.

  The range side lobe suppression unit 70 generates detection data by suppressing the range side lobe included in the pulse compression data, although a specific configuration and a range side lobe suppression method will be described later. The display processing unit 80 displays on the display screen a detection image in which color tone and luminance are set based on the signal level of detection data (corresponding to the amplitude value of the pulse compression signal after range side lobe suppression).

  Next, a specific configuration of the range side lobe suppressing unit 70 and a range side lobe suppressing method will be described. FIG. 2 is a block diagram showing a configuration of the range side lobe suppressing unit 70. As shown in FIG.

  The range sidelobe suppression unit 70 includes a suppression range setting unit 71, a suppression exclusion range setting unit 72, a suppression value setting unit 73, and a suppression calculation unit 74.

  The suppression range setting unit 71 sets the suppression range based on the signal level at each depth position of the pulse compression data. FIG. 3 is a waveform diagram for explaining suppression range setting means. FIG. 3 is a diagram illustrating the signal level of the pulse compressed data along the depth direction.

  The suppression range setting unit 71 sequentially compares the signal level (amplitude level) of the data at each depth position of the pulse compression data with the first threshold ThE1 along the depth direction. The first threshold ThE1 is set based on the peak level of the main lobe of the pulse compression data when the ultrasonic pulse signal to be transmitted is reflected at a predetermined depth on a large target (in this case, the seabed). For example, when the ultrasonic pulse signal is set so that the peak level becomes a predetermined A value, a value attenuated by a predetermined B value from the A is set as the first threshold ThE1. At this time, the B value may be appropriately set in consideration of the set position of the seabed and the TVG gain correction amount.

  The suppression range setting unit 71 has a signal level E (n) at a position in the depth direction (attention position (n)) that is equal to or higher than the first threshold ThE1 and is adjacent to the attention position (n) in the direction of shallow depth. When it is detected that the signal level E (n−1) of the matching position (n−1) is less than the first threshold ThE1, the target position (n) is set to the end point on the deep side of the suppression range Zone (s).

  The suppression range setting unit 71 sets a predetermined depth direction range from the detected target position (n) to the shallow side as the suppression range Zone (s). At this time, the range in the depth direction set in the suppression range Zone (s) can be set based on the estimation result because the waveform of the range side lobe can be estimated from the transmitted ultrasonic pulse signal.

  The suppression range setting unit 71 notifies the set suppression range Zone (s) to the suppression exclusion range setting unit 72, the suppression value setting unit 73, and the suppression calculation unit 74.

  The suppression exclusion range setting unit 72 compares the second threshold ThE2 for setting the suppression exclusion range with the signal level Ez (i) of each point (i), and suppresses the suppression exclusion range ExZone within the suppression range Zone (s). Set (s). FIG. 4 is a waveform diagram for explaining the suppression exclusion range setting means. FIG. 4 is a diagram illustrating a signal level of pulse compression data along the depth direction.

  The suppression exclusion range setting unit 72 sets a predetermined depth range as the offset determination range Zone (r) with the deepest position of the suppression range Zone (s) as a reference point.

  The suppression exclusion range setting unit 72 extracts a predetermined number of high signal levels Ez (i) from the signal level Ez (i) at each point (i) in the offset determination range Zone (r), and obtains the representative value Ezr. calculate. For example, the suppression exclusion range setting unit 72 calculates an average value as the representative value Ezr.

  The suppression exclusion range setting unit 72 calculates the offset value Eoff by subtracting the subtraction value ΔEz for offset setting from the calculated representative value Ezr. The offset setting subtraction value ΔEz can be set, for example, from the amplitude of the ultrasonic pulse signal to be transmitted or the peak level of the main lobe.

  The suppression exclusion range setting unit 72 sets a second threshold value ThE2 composed of a predetermined function obtained by shifting the amplitude level by the offset value Eoff. At this time, the suppression exclusion range setting unit 72 uses, as the predetermined function, for example, an exponential function with the position in the depth direction as the bottom and the coefficient set appropriately. As shown in FIG. 14, the range side lobe tends to increase in signal level as it approaches the main lobe, and is set with the intention that the signal level increases rapidly as the main lobe approaches. Is.

  By using such an exponential function, it is possible to set the second threshold ThE2 that approximates the envelope (change tendency) of the peak of the signal level of the range side lobe. In addition to the exponential function, other functions may be used as long as they can approximate the envelope of the signal level peak of the range sidelobe along the depth direction.

  The suppression exclusion range setting unit 72 compares the signal level Ez (i) of the pulse compression data with the second threshold ThE2 at each point (i) in the suppression range Zone (S). The suppression exclusion range setting unit 72 sets the point (i) as the suppression exclusion range ExZone (s) if the signal level Ez (i) of the pulse compression data is higher than the second threshold ThE2.

  Thus, by setting the second threshold ThE2 that approximates the waveform of the range side lobe, the echo of the target existing in the range side lobe can be accurately detected, and the range including the echo of the target Can be reliably set to the suppression exclusion range ExZone (s). At this time, for example, when a predetermined threshold is set with a predetermined offset for the range sidelobe suppression range Zone (s) as conventionally performed, a target with a high echo level (signal level) is Even if it can be detected, a target with a low echo level (signal level) cannot be detected and may be included in the suppression range Zone (s). However, by using the second threshold ThE2 that approximates the peak envelope of the range side lobe as in this embodiment, the target in the range side lobe is reliably detected without being affected by the signal level. be able to.

  The suppression exclusion range setting unit 72 may set not only the detected point but also a predetermined depth range including the point as the suppression exclusion range ExZone (s). Thus, by setting the suppression exclusion range ExZone (s) to have a predetermined width in the depth direction, the boundary between the suppression exclusion range ExZone (s) and the suppression range Zone (S) in the waveform after the suppression process Can be alleviated.

  The suppression value setting unit 73 determines the signal level Ez (i) at a plurality of points (i) within the suppression range Zone (s) and the signal level Ez (j) at a plurality of points (j) outside the suppression range Zone (s). The suppression value SS (i) is calculated using the set offset value Moff. FIG. 5 is a waveform diagram for explaining suppression value setting means. FIG. 5 is a diagram illustrating the signal level of the pulse compression data along the depth direction.

  The suppression value setting unit 73 calculates representative values of the signal levels Ez (i) at a plurality of points (i) within the suppression range Zone (s). Specifically, the suppression value setting unit 73 has a predetermined number of signal levels Ez (i) n on the side having the lowest signal level among the signal levels Ez (i) at all points in the suppression range Zone (s). To extract. The suppression value setting unit 73 calculates the average value MMF1 of the extracted signal levels Ez (i) n as a representative value.

  The suppression value setting unit 73 calculates representative values of the signal levels Ez (j) at a plurality of points (j) outside the suppression range Zone (s). Specifically, the suppression value setting unit 73 has a predetermined number of signal levels on the side with the lowest signal level among the signal levels Ez (j) at each point (j) on the side shallower than the suppression range Zone (s). Ez (j) m is extracted. The suppression value setting unit 73 calculates the average value MMF2 of the extracted signal levels Ez (j) n as a representative value.

  The suppression value setting unit 73 sets a value obtained by dividing the average value MMF1 by the average value MMF2 as an offset value Moff.

  The suppression value setting unit 73 sets a suppression value SS (i) at each point (i) in the suppression range Zone (s) using a predetermined function whose amplitude level is shifted by the offset value Moff. At this time, the suppression exclusion range setting unit 72 uses, as the predetermined function, for example, an exponential function with the position in the depth direction as the bottom and the coefficient appropriately set, as in the second threshold ThE2.

  By performing such processing, a suppression value SS whose value is set from the external environment, that is, the amplitude level of the noise and the amplitude level of the range side lobe and whose value changes with a characteristic approximate to the peak envelope of the range side lobe. (I) can be set. Thereby, an appropriate value and the suppression value SS (i) of the characteristic can be set.

  The suppression calculation unit 74 outputs pulse compression data at each position (i) in the suppression range Zone (s) excluding the suppression exclusion range ExZone (s) set by the suppression range setting unit 71 and the suppression exclusion range setting unit 72. The signal level Ez (i) is suppressed by the suppression value SS (i) set by the suppression value setting unit 73. For example, the suppression calculation unit 74 subtracts the suppression value SS (i) from the signal level Ez (i) at each position (i).

  The suppression calculation unit 74 outputs the pulse compression data subjected to the suppression calculation to the display processing unit 80 as detection data.

  FIG. 6 is a diagram (waveform diagram) showing the signal level of the pulse compressed data along the depth direction after the suppression calculation. As shown in FIG. 6, the signal level of the range side lobe is suppressed by performing the above-described processing. Further, the target echo existing within the range side lobe is not suppressed, and the original signal level is maintained. As described above, by using the configuration and processing of the present embodiment, detection data in which the range side lobe is effectively suppressed can be generated without suppressing the echo of the target existing in the range side lobe. .

  In the above description, the example in which the range side lobe suppression processing is realized by each functional unit has been described. However, the drive signal generation process for transmitting the ultrasonic pulse signal STx, the pulse compression process for the received signal based on the echo signal ERx, and the range sidelobe suppression process for the pulse compressed signal (pulse compressed data) are programmed. It can also be stored in a storage means and read and executed by a computer.

  FIG. 7 is a flowchart showing the range side lobe suppression method of this embodiment.

  The underwater detection device performs drive signal generation control so as to transmit the frequency-modulated ultrasonic pulse signal STx (S101). The underwater detection device receives the echo signal ERx of the ultrasonic pulse signal STx and generates a reception signal (S102). The underwater detection device performs pulse compression processing on the received signal to generate pulse compression data (S103).

  The underwater detection device compares the signal level with the first threshold ThE1 at each position along the depth direction, detects the main lobe side edge of the range side lobe of the pulse compression data, and sets the suppression range Zone (s). Set (S104). A more specific setting flow of the suppression range Zone (s) will be described later with reference to FIG.

  The underwater detection device sets a second threshold value ThE2 for detection of an exclusion range that approximates the waveform of the range side lobe, and the suppression exclusion range from the second threshold value ThE2 and the signal level at each position within the suppression range Zone (s). ExZone (s) is set (S105). A more specific setting flow of the suppression exclusion range ExZone (s) will be described later with reference to FIG.

  The underwater detection device sets a suppression value SS (i) that approximates the waveform of the range side lobe (S106). A more specific setting flow of the suppression value SS (i) will be described later with reference to FIG.

  The underwater detection device performs sidelobe suppression calculation by suppressing the signal level E (i) with the suppression value SS (i) at each position within the suppression range Zone (s), and generates detection data (S107). .

  Next, a method for setting the suppression range Zone (s) will be described with reference to FIG. FIG. 8 is a flowchart showing a setting flow of the suppression range Zone (s).

  The underwater detection device acquires the signal level E (n) of the target position (n) and compares it with the first threshold ThE1 (S401). The first threshold ThE1 is set based on the peak level of the main lobe by the ultrasonic pulse signal as described above.

  When the signal level E (n) at the target position (n) is equal to or higher than the first threshold ThE1 (S402: YES), the underwater detection device has a signal level E (n) that is one shallower than the target position (n). -1) and the first threshold ThE1 are compared (S403).

  When the signal level E (n) of the target position (n) is less than the first threshold ThE1 (S402: NO), the underwater detection device moves the target position one position to the deeper side (S410). Then, the signal level at the new target position is compared with the first threshold ThE1 (S401).

  When the signal level E (n−1), which is one shallower than the target position (n), is lower than the first threshold ThE1 (S404: YES), the underwater detection device sets the target position (n) to the range side lobe. Is detected as an end point position on the main lobe side (S405).

  The underwater detection device sets the end point on the deeper side as the end point and sets the shallow predetermined range as the suppression range Zone (s) (S406).

  By using such processing, it is possible to set the suppression range Zone (s) that is the range of the range side lobe to be suppressed by simple processing without using complicated processing.

  In the above-described method, an example in which the target position is sequentially moved from the shallow side to the deep side has been described. However, the target position may be moved from the deep side to the shallow side. As described above, the suppression range Zone (s) is set by the end point on the deep side. Therefore, the amount of processing can be reduced by performing the above processing from the deep side.

  Next, a method for setting the suppression exclusion range ExZone (s) will be described with reference to FIG. FIG. 9 is a flowchart showing a setting flow of the suppression exclusion range ExZone (s).

  When the underwater detection device sets the suppression range Zone (s) as described above, the underwater detection device sets the offset determination range Zone (r) deeper than the suppression range Zone (s). The underwater detection device sets a predetermined depth range as an offset determination range Zone (r) using an end point on the deeper side of the suppression range Zone (s) as a reference point. More specifically, for example, the underwater detection device sets the offset determination range Zone (r) so as to include the main lobe peak. The peak of the main lobe can be detected from, for example, the highest depth position of the signal level Ez (i).

  The underwater detection device acquires the signal level Ez (i) at each position (i) within the offset determination range Zone (r). The underwater detection device sorts the signal levels Ez (i) at a plurality of positions and extracts a predetermined number (for example, n) of signal levels Ez (i) n from the highest level (S501).

  The underwater detection device calculates an average value of the signal levels Ez (i) n as the representative value Ezr of the predetermined number n of extracted signal levels Ez (i) n. The underwater detection device calculates an offset value Eoff by subtracting a subtraction value ΔEz for offset setting from the representative value (average value) Ez. The offset setting subtraction value ΔEz can be set, for example, from the amplitude of the ultrasonic pulse signal to be transmitted or the peak level of the main lobe.

  The underwater detection device sets a sidelobe approximation function using an exponential function in which a predetermined coefficient is set with a depth as a base. The underwater detection device sets the second threshold ThE2 at each position by offsetting the side lobe approximation function with the offset value Eoff (S502). As a result, the second threshold ThE2 that approximates the waveform of the range side lobe as shown in FIG. 4 and is higher than the amplitude level of the range side lobe by a predetermined amplitude level can be set.

  The underwater detection device compares the signal level Ez (i) with the second threshold ThE2 at each position (i) in the suppression range Zone (s) (S503).

  If the signal level Ez (i) is higher than the second threshold ThE2 (S504: YES), the underwater detection device sets this position as the suppression exclusion range ExZone (s) (S505). If the signal level Ez (i) is equal to or lower than the second threshold ThE2 (S504: NO), the underwater detection device does not set this position as the suppression exclusion range ExZone (s).

  The underwater detection device continuously executes the comparison process for all positions in the suppression range Zone (s) until the comparison process is completed (S506: NO → S503).

  When the comparison process is completed for all positions in the suppression range Zone (s) (S506: YES), the underwater detection device suppresses from the suppression range Zone (s) set in the flow shown in FIG. The suppression range Zone (s) is determined so as to exclude the exclusion range ExZone (s) (S507).

  By performing such processing, a threshold value approximated to the envelope of the range sidelobe peak can be set. For this reason, even if a target such as a school of fish exists in the suppression range Zone (s), the range of the target can be detected and set to the suppression exclusion range ExZone (s). As a result, it is possible to prevent the target existing in the suppression range Zone (s) from being suppressed by the suppression process described later.

  By performing such processing, a target with a low echo level that is difficult to detect when the threshold is simply set to a constant value (a target with a signal level slightly higher than the envelope of the peak of the range sidelobe). ) Can also be detected more reliably and set to the suppression exclusion range ExZone (s).

  In this flow, an example in which only the detected position is set as the suppression exclusion range ExZone (s) has been shown. However, as described above, a predetermined depth range including the detection position is set as the suppression exclusion range ExZone (s). It may be set.

  Next, a method for setting the suppression value SS (i) will be described with reference to FIG. FIG. 10 is a flowchart showing a setting flow of the suppression value SS (i).

  When the suppression range Zone (s) is set as described above, the underwater detection device acquires the signal level Ez (i) at each position (i) within the suppression range Zone (s). The underwater detection device sorts the signal levels Ez (i) at a plurality of positions, and extracts a predetermined number (for example, m) of signal levels Ez (i) m from the lowest level. The underwater detection device calculates an average value MMF1 of the signal levels Ez (i) m as a representative value of the predetermined number m of signal levels Ez (i) m extracted (S601).

  The underwater detection device acquires a signal level Ez (j) at each position (j) shallower than the suppression range Zone (s). The underwater detection apparatus sorts signal levels Ez (j) at a plurality of positions, and extracts a predetermined number (for example, m) of signal levels Ez (j) m from the lowest level. The underwater detection device calculates an average value MMF2 of the signal levels Ez (j) m as a representative value of the extracted number m of signal levels Ez (j) m (S602).

  Note that the number of extractions in S601 and S602 may be the same as or different from the number of extractions when the above-described suppression exclusion range ExZone (s) is set.

  The underwater detection device calculates an offset value Moff from the average value MMF1 and the average value MMF2 (S603). For example, specifically, the underwater detection device calculates the offset value Moff by dividing the average value MMF1 by the average value MMF2.

  The underwater detection device sets a sidelobe approximation function using an exponential function in which a predetermined coefficient is set with a depth as a base. The underwater detection device sets the suppression value SS (i) at each position by offsetting the side lobe approximation function with the offset value Moff (S604).

  By performing such processing, the suppression value SS (i) approximated to the envelope of the range sidelobe peak can be set to an appropriate value.

  In the above-described method, the case where there is no position in the suppression range Zone (s) whose signal level is higher than the end point position on the deeper side of the suppression range Zone (s) has been described as an example. In consideration of the presence of the following, the following processing may be used.

  FIG. 11 is a flowchart showing a second setting flow of the suppression range Zone (s).

  The setting of the presupposed suppression range Zone (s) is the same, and the suppression range Zone (S) of a predetermined range is set in the depth direction by the same flow as the flow of FIG. 8 described above (S421).

  The underwater detection device compares the signal level E (n) at the end position detected for setting the suppression range Zone (S) with the signal level Ez (i) at each position in the suppression range Zone (S). At this time, the underwater detection device compares the signal levels in the order closer to the end point position.

  When the underwater detection device detects that the compared signal level Ez (i) is higher than the signal level E (n) at the end point position (S423: YES), the underwater detection range is set to a range shallower than this position. Excluded from (S) (S424). Then, the comparison is not made for each position shallower than this position, and only the range deeper than this position is determined to be the suppression range Zone (S) (S426).

  When the underwater detection device detects that the compared signal level Ez (i) is equal to or lower than the signal level E (n) at the end point position (S423: NO), the underwater detection device performs the same at the next position adjacent to the shallower side. Make a comparison. Here, if the compared signal level Ez (i) continues to be equal to or lower than the signal level E (n) at the end point position, the underwater detection device continues the comparison until the confirmation is completed at all positions S425: NO → S422). If the signal level Ez (i) is equal to or lower than the signal level E (n) at the end point position at all positions in the suppression range Zone (S) (S425: YES), the underwater detection device has the same flow as FIG. The suppression range Zone (s) set in (1) is used as it is.

  By using such processing, when there is a very high signal level such as a large school of fish in the suppression range Zone (s), the range can be excluded from the suppression range Zone (s). . Thereby, there is no need to set an extra suppression exclusion range ExZone (s), and the range sidelobe suppression process can be simplified and speeded up. Moreover, even if such a very high signal level fish school exists in the range of the range side lobe, it can be left in the detection data (on the detection image) without being suppressed.

  FIG. 12 is a diagram (waveform diagram) showing signal levels of pulse compression data along the depth direction before and after suppression when the second setting flow of the suppression range Zone (s) is used.

  As shown in FIG. 12, when the predetermined range shallower than the end position on the main lobe side of the range side lobe is set as the suppression range Zone (s), there is a large target in the suppression range Zone (s). Even so, the signal level of the large target is not suppressed. Since the range of the large target is not included in the suppression range Zone (s), the range of the suppression calculation is kept to a minimum and the speed of the suppression calculation can be increased.

  In FIG. 12, the shallow side of the large target (large fish school or the like) is not particularly illustrated, but a range side lobe similarly occurs in the range on the shallow side of the large target. The above-described processing can be applied to such a range, and appropriate range side lobe suppression processing can be performed.

  In the above description, the example in which the offset value Moff is calculated by dividing the average value MMF1 by the average value MMF2 in setting the suppression value SS (i). In this method, the average value MMF2 (low-level echo average value shallower than the suppression range Zone (s) (average value of external environmental noise)) is the average value MMF1 (low-level echo of the suppression range Zone (s)). If it is smaller than the average value), the offset value Moff is set to an appropriate value. In normal sea conditions, this relationship is not particularly problematic, but by using the following processing, an appropriate offset value Moff can be set more reliably.

  FIG. 13 is a flowchart showing a second setting flow of the suppression value SS (i). Steps S601 and S602 for calculating the average values MMF1 and MMF2 are the same as those in FIG.

  If the average value MMF1 is larger than the average value MMF2 (S611: YES), the underwater detection device divides the average value MMF1 by the average value MMF2 to calculate an offset value Moff (= MMF1 / MMF2) (S612).

  When the underwater detection device calculates the offset value Moff by division, the underwater detection device compares the offset value Moff with a preset maximum offset value Mmax. If the offset value Moff is equal to or less than the maximum offset value Mmax (S614: NO), the underwater detection device applies the offset value Moff as it is as an offset of the sidelobe approximation function, and sets the suppression value SS (i) ( S604).

  If the offset value Moff is larger than the maximum offset value Mmax (S614: YES), the underwater detection device sets the offset value Moff to the maximum offset value Mmax (S615). Then, the offset value Moff consisting of the maximum offset value Mmax is applied to the offset of the sidelobe approximation function, and the suppression value SS (i) is set (S604). As described above, when the offset value Moff by division becomes larger than the maximum offset value Mmax, the offset value becomes unnecessarily high when the external environmental noise is extremely small by applying the maximum offset value Mmax. Can be prevented. Further, even if a target exists in the suppression range Zone (s) and the average value MMF1 increases, the offset value Moff can be limited by the maximum offset value Mmax, so that the offset value can be prevented from becoming unnecessarily high. . Thereby, an appropriate suppression value SS (i) can be set.

  If the average value MMF1 is equal to or less than the average value MMF2 (S611: NO), the underwater detection device sets the offset value Moff to a predetermined value Mcc (Mcc ≧ 1) (S613). At this time, the predetermined value Mcc may be set to a predetermined value close to 1. Then, the offset value Moff consisting of the predetermined value Mcc is applied to the offset of the sidelobe approximation function to set the suppression value SS (i) (S604). Thus, by setting the offset value Moff to the predetermined value Mcc when the average value MMF1 is smaller than MMF2, it is possible to prevent the offset value Moff from becoming unnecessarily high even when the external environmental noise is large. . Thereby, an appropriate suppression value SS (i) can be set.

  In the above description, the average value is used as the representative value. However, other statistical calculation values such as the median value, the maximum value, and the minimum value may be used as appropriate.

10: Ultrasonic transceiver
20: transmitter
30: Transmission / reception switching unit,
40: AD converter,
50: Pulse compression unit,
60: detector
70: Range side lobe suppression unit,
71: Suppression range setting unit,
72: suppression exclusion range setting section,
73: Suppression value setting unit,
74: Suppression calculation unit,
80: display processing unit,
100: transducer
901: Undersea, 902: School of fish

Claims (9)

A pulse compression unit that generates a pulse-compressed signal by pulse-compressing a reception signal obtained from a reflected echo of a frequency-modulated ultrasonic pulse signal;
A range sidelobe suppression unit that generates detection data by performing range sidelobe suppression processing on the pulse compression signal, and an underwater detection device,
The range side lobe suppressor is
A suppression range setting unit that determines a suppression range based on a pulse compression signal;
A threshold for determining the exclusion range is set using the signal level of the pulse compression signal at a plurality of depth positions in the predetermined range deeper than the suppression range and the range sidelobe approximate waveform of the ultrasonic pulse signal. A suppression exclusion range setting unit that determines a suppression exclusion range based on a comparison result between the threshold for determining the exclusion range and the signal level of the pulse compression signal;
A suppression value setting unit that determines a suppression value based on a signal level of the pulse compression signal within the suppression range;
A suppression operation unit that performs an operation to suppress the signal level of the pulse compression signal in the suppression range excluding the suppression exclusion range with the suppression value,
The suppression value setting unit includes:
In the signal level of the pulse compression signal at a plurality of positions within the suppression range, a predetermined number of signal levels are extracted from the lowest level, and a first representative value is calculated from the extracted signal level,
In the signal level of the pulse compressed signal at a plurality of positions outside the suppression range, a predetermined number of signal levels are extracted from the lowest level, and a second representative value is calculated from the extracted signal level,
An offset value is calculated by dividing the first representative value by the second representative value,
If the offset value is less than or equal to the maximum offset value, the suppression value is determined from the offset value and a range sidelobe approximate waveform of the ultrasonic pulse signal,
If the offset value is larger than the maximum offset value, the suppression value is determined from the maximum offset value and a range sidelobe approximate waveform of the ultrasonic pulse signal ,
Underwater detection device. The underwater detection device according to claim 1,
The suppression range setting unit includes:
When the signal level of the pulse compressed signal at the target position is equal to or higher than the first threshold based on the signal level of the main lobe, and the signal level of the pulse compressed signal on the shallower side than the target position is lower than the first threshold, Set the attention position to the end point on the deep side of the suppression range,
An underwater detection device that sets a depth range of the suppression range from the ultrasonic pulse signal. The underwater detection device according to claim 2,
The suppression range setting unit includes:
An underwater detection device that, when detecting a position of a signal level higher than the signal level of an end point on the deeper side of the suppression range within the suppression range, sets only the side deeper than the detected position as the suppression range. An underwater detection device according to any one of claims 1 to 3,
The suppression exclusion range setting unit
An underwater detection apparatus that sets a threshold for determining the exclusion range from a representative value of the signal level of the pulse compression signal in a predetermined range deeper than the suppression range. The underwater detection device according to claim 4,
The suppression exclusion range setting unit
An underwater detection apparatus that uses, as the representative value, an average value of a predetermined number of signal levels having a higher signal level among signal levels of the pulse compression signal in a predetermined range deeper than the suppression range. An underwater detection device according to any one of claims 1 to 5 ,
The suppression value setting unit includes:
An underwater detection device that sets the offset value to a predetermined offset value of 1 or more when the offset value is smaller than 1. The underwater detection device according to any one of claims 1 to 6 ,
The underwater detection device, wherein the range sidelobe approximate waveform is set by an exponential function based on the ultrasonic pulse signal. A pulse compression step of generating a pulse compression signal by pulse-compressing a reception signal obtained from a reflection echo of a frequency-modulated ultrasonic pulse signal;
A range side lobe suppression step of generating detection data by performing range side lobe suppression processing on the pulse compression signal, and an underwater detection method,
The range side lobe suppression step includes
A suppression range setting step for determining a suppression range based on the pulse compression signal;
A threshold for determining the exclusion range is set using the signal level of the pulse compression signal at a plurality of depth positions in the predetermined range deeper than the suppression range and the range sidelobe approximate waveform of the ultrasonic pulse signal. A suppression exclusion range setting step of determining a suppression exclusion range based on a comparison result between the threshold for determining the exclusion range and the signal level of the pulse compression signal;
A suppression value setting step of determining a suppression value based on a signal level of the pulse compression signal within the suppression range;
Have a, a suppression operation step for performing an operation for suppressing the signal level of the pulse compression signal of the suppression range excluding the suppression exclusion range in the suppression value,
The suppression value setting step includes:
In the signal level of the pulse compression signal at a plurality of positions within the suppression range, a predetermined number of signal levels are extracted from the lowest level, and a first representative value is calculated from the extracted signal level,
In the signal level of the pulse compressed signal at a plurality of positions outside the suppression range, a predetermined number of signal levels are extracted from the lowest level, and a second representative value is calculated from the extracted signal level,
An offset value is calculated by dividing the first representative value by the second representative value,
If the offset value is less than or equal to the maximum offset value, the suppression value is determined from the offset value and a range sidelobe approximate waveform of the ultrasonic pulse signal,
If the offset value is larger than the maximum offset value, the suppression value is determined from the maximum offset value and a range sidelobe approximate waveform of the ultrasonic pulse signal ,
Detection method in water. A pulse compression process for generating a pulse compression signal by pulse-compressing a reception signal obtained from a reflected echo of a frequency-modulated ultrasonic pulse signal;
An underwater detection program for causing a computer to perform range side lobe suppression processing for generating detection data by performing range side lobe suppression processing on the pulse compression signal,
The computer
As the range side lobe suppression processing,
A suppression range setting process for determining a suppression range based on a pulse compression signal;
A threshold for determining the exclusion range is set using the signal level of the pulse compression signal at a plurality of depth positions in the predetermined range deeper than the suppression range and the range sidelobe approximate waveform of the ultrasonic pulse signal. A suppression exclusion range setting process for determining a suppression exclusion range based on a comparison result between the exclusion range determination threshold value and the signal level of the pulse compression signal;
A suppression value setting process for determining a suppression value based on a signal level of the pulse compression signal within the suppression range;
Performing a suppression calculation process for performing a calculation to suppress the signal level of the pulse compression signal in the suppression range excluding the suppression exclusion range with the suppression value,
In the suppression value setting process,
In the signal level of the pulse compression signal at a plurality of positions within the suppression range, a predetermined number of signal levels are extracted from the lowest level, and a first representative value is calculated from the extracted signal level,
In the signal level of the pulse compressed signal at a plurality of positions outside the suppression range, a predetermined number of signal levels are extracted from the lowest level, and a second representative value is calculated from the extracted signal level,
An offset value is calculated by dividing the first representative value by the second representative value,
If the offset value is less than or equal to the maximum offset value, the suppression value is determined from the offset value and a range sidelobe approximate waveform of the ultrasonic pulse signal,
If the offset value is larger than the maximum offset value, the suppression value is determined from the maximum offset value and a range sidelobe approximate waveform of the ultrasonic pulse signal,
Water in the detection program.

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