JP6192946B2 - Underwater detection method and underwater detection device - Google Patents

Description

  The present invention relates to an underwater detection method and an underwater detection device that transmit an ultrasonic pulse signal in water and generate 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.

  Patent Document 2 discloses an underwater detection device for suppressing a range side lobe caused by the seabed (the range side lobe will be described later). In this underwater detection device, a suppression range (suppression candidate range) is determined based on two peak hold values (a forward movement peak hold value and a backward movement peak hold value). Then, the signal in the predetermined range in the pulse compression signal is determined to be a signal corresponding to the range side lobe based on the comparison with the second threshold which is a predetermined value, and the suppression process is performed.

JP 2005-249398 A Patent No. 5074299

  FIG. 17 is a diagram illustrating a time waveform (waveform along the depth direction) of a reception signal obtained by reflection on a target when pulse compression is used.

  However, when pulse compression is used, as shown in FIG. 17, 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.

  Further, as in Patent Document 2, if a signal in a predetermined range in a pulse compression signal is determined to be a signal corresponding to a range side lobe based on a comparison with a second threshold that is a predetermined value, the following problem occurs. .

  An echo of a target (for example, a fish with a bottom) to be excluded from suppression is displayed so as to overlap a range side lobe of a target (for example, the sea floor) having a very high signal level in the vicinity of the target. The signal level of the range side lobe decreases as it moves away from the main lobe in the depth direction. Therefore, when the second threshold is set to a predetermined value as in Patent Document 2, there is a risk that an echo desired to be excluded from suppression is erroneously suppressed and a risk that a range side lobe desired to be suppressed is not appropriately suppressed.

  An object of the present invention is to appropriately suppress a range side lobe caused by a target with a high signal level of an echo such as the seabed.

To solve the above SL problem, underwater detection method according to an aspect of the invention, a pulse compression signal to pulse compression the received signal obtained from the reflected echo of the ultrasonic pulse signal frequency-modulated and transmitted into the water A step of generating, a step of detecting a plurality of local peak positions that are depth positions of the depth of the local peak in the pulse compression signal, and a range of each depth set based on each local peak position, and setting a suppression candidate range to be suppressed candidate sidelobes, among the data points of the pulse compression signal in each of said suppression candidate range, the signal level is based on the range side lobe approximate waveform of the ultrasonic pulse signal a step of suppressing the signal level of the small data points, than the set suppression exclusion determination threshold Te, put to each of said suppression candidate range Each of the depth ranges in which the signal level is equal to or higher than the suppression exclusion determination threshold is set as a suppression exclusion range that is outside the range sidelobe suppression candidate, and the step of suppressing the signal level includes a plurality of The signal level of the pulse compression signal is suppressed in a plurality of suppression ranges excluding the suppression exclusion range among the suppression candidate ranges.

  In addition, the local peak mentioned above is a local peak (maximum point) in a pulse compression signal. Specifically, when attention is paid to a certain point of the pulse compression signal, the signal level at the point is the signal level of both the point on the shallower side and the point on the deeper side than the point. If it is higher, the point is called a local peak.

Good Mashiku, the underwater detection method, the signal level at the suppression candidate range, the depth range of said suppression exclusion determination threshold above, the step of setting the suppression exclusion range of the suppression candidates out of the range sidelobes Further, in the step of suppressing the signal level, the signal level of the pulse compression signal is suppressed in a suppression range excluding the suppression exclusion range in the suppression candidate range.

Further preferably, the in the step of setting the suppression exclusion range, the suppression exclusion range is a predetermined range over a shallowest position further from the shallow side in the depth range of said suppression exclusion determination threshold value or higher, and the deep range Is set to include at least one of a predetermined range from the deepest position to the deeper side.

Good Mashiku, the underwater detection method further comprises a step of setting the local peak position detection range the a depth range of the local peak position is detected.

More preferably, the underwater detection method includes a step of detecting, in the pulse compression signal, a reference position that is a depth position at which the signal level is equal to or higher than a reference position detection threshold before and after the depth from the shallow side to the deep side. Further, in the step of setting the local peak position detection range, a predetermined depth range extending from the reference position to a side deeper than the reference position is set as the local peak position detection range, and the suppression candidate range is In the setting step, a predetermined range extending from the local peak position to a side shallower than the local peak position is set as the suppression candidate range.

In further preferably, the underwater detection method further comprises a step of setting the reference position detection threshold based on the pulse compressed signal.

Further preferably, in the step of setting the reference position detection threshold from the noise level calculated on the basis of the pulse compressed signal is a predetermined level higher level is set as the reference position detection threshold.

Good Mashiku, in the step of detecting the local peak position, a plurality of the local peak position is detected, in the step of setting the suppression candidate range, a plurality of the suppression corresponding to each of the plurality of local peak position In the step of setting a candidate range and setting the suppression exclusion range, a plurality of suppression exclusion ranges corresponding to each of the plurality of suppression candidate ranges are set, and in the step of suppressing the signal level, the plurality of suppressions The signal level of the pulse compression signal is suppressed for each of the plurality of suppression ranges corresponding to each of the candidate ranges.

Further preferably, in the step of detecting the local peak position, a plurality of the local peak position toward the shallower side of the water depth to the deep side is detected in order, a plurality of detected in the order of the local peak position If the signal level at the predetermined local peak position is equal to or lower than the signal level at the local peak position detected immediately before the predetermined local peak position, the predetermined local peak position is not detected and the predetermined local peak position is not detected. If the signal level at the position is higher than the signal level at the local peak position detected immediately before the predetermined local peak position, the predetermined local peak position is detected.

Good Mashiku, the underwater detection method, the said local peak position detected in the step of detecting the local peak position, the based on the range side lobe approximate waveform of an ultrasonic pulse signal, the suppression exclusion determination threshold The method further includes the step of setting.

Good Mashiku is range side lobe approximate waveform of the ultrasonic pulse signal is a waveform signal level decreases toward the deep side to the shallow side at least part of the depth range.

Good Mashiku, in the step of suppressing the signal level, so that the signal level of the pulse compression signal within the suppression range is the noise level and the same level in the vicinity of the shallowest depth of the side position in the suppression candidate range Repressed.

Further preferably, the underwater detection method, the includes within suppression range further step of calculating a suppression limits an upper limit value of the signal level of the pulse compression signal, in the step of suppressing the signal level, the suppression The signal level is suppressed so that the signal level of the pulse compression signal within the range does not exceed the suppression limit value.

Further preferably, in the step of suppressing the signal level for each signal level of the pulse compressed signal is one of a depth position of more than the suppression limit value within the suppression range, the signal level at each depth position The signal level is suppressed by dividing every predetermined value.

Good Mashiku, said the step of calculating a suppression limit value, the suppression limit value based on the noise level of a predetermined range including the depth position of the shallowest side in the suppression candidate range is calculated.

To solve the above SL problem, underwater detection system according to an aspect of the invention, a pulse compression signal to pulse compression the received signal obtained from the reflected echo of the ultrasonic pulse signal frequency-modulated and transmitted into the water a pulse compression unit to be generated, a plurality of local peak positions the depth position of the water depth of the local peaks in the pulse compression signal, the local peak position detector for detecting the respective set of each said local peak position as a reference the depth range, and the suppression candidate range setting unit for setting a suppression candidate range to be suppressed candidate range sidelobes, among the data points of the pulse compression signal in each of said suppression candidate range, the signal level the ultrasonic pulse The signal level of the data point that is smaller than the suppression exclusion judgment threshold set based on the approximate range sidelobe waveform of the signal And suppression processing section which applies the signal level in each said suppression candidate range, the suppression exclusion determination each depth range equal to or larger than the threshold value, the range side lobe suppression exclusion range setting unit for setting a suppression exclusion range of the suppression candidates outside The suppression processing unit suppresses the signal level of the pulse compression signal in a plurality of suppression ranges excluding the suppression exclusion range among the plurality of suppression candidate ranges.

  According to the present invention, it is possible to appropriately suppress a range side lobe caused by a target having a high signal level of an echo such as the seabed.

It is a block diagram which shows the structure of the underwater detection apparatus which concerns on embodiment of this invention. It is a block diagram which shows the structure of a range side lobe suppression part. It is a flowchart which shows operation | movement of an underwater detection apparatus. It is a flowchart illustrating a process of setting the local peak detection range Z _P. It is a wave form chart showing an example of pulse compression data, and is a figure for explaining standard position detection threshold ThE1. A diagram showing an enlarged predetermined range in the depth direction in FIG. 5 is a diagram for explaining detection of a local peak P _A to P _C. It is a figure which expands and shows a part of FIG. FIG. 7 is a diagram for explaining suppression candidate ranges Z _{A to} Z _C and suppression exclusion determination thresholds ThE2 _{A to} ThE2 _C in the pulse compression data shown in FIG. 6. FIG. 7 is a diagram for explaining a suppression exclusion range EXZ _B and a suppression range Z _B ′ in the pulse compression data shown in FIG. 6. It is a flowchart which shows the process of suppressing a range side lobe. FIG. 7 is a diagram for describing setting of a suppression limit value _{ELMTB in} the pulse compression data shown in FIG. 6. It is a figure which shows the detection data after range side lobe suppression with the pulse compression data shown in FIG. It is a flowchart which shows operation | movement of the underwater detection method which concerns on a modification. It is a flowchart for demonstrating the suppression process of the range side lobe in the underwater detection method which concerns on a modification. It is a wave form diagram which shows an example of pulse compression data, Comprising: It is a figure for demonstrating suppression of the range side lobe in the underwater detection method which concerns on a modification. It is a flowchart for demonstrating the suppression process of the range side lobe in the underwater detection method which concerns on a modification. It is a figure which shows an example of 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 and an underwater detection method according to an 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.

[Constitution]
FIG. 1 is a configuration diagram of an underwater detection device 10 according to an 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, is composed of a transmission pulse length corresponding to the maximum detection distance (maximum detection depth), and 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 transducer 100 receives an echo signal ERx obtained by reflecting the ultrasonic pulse signal STx on the seabed 901 and the fish 902 in the water. 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 receiving amplifier performs amplification 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 suppressing unit 70 suppresses the range side lobe included in the pulse compression data and generates detection data.

  The display processing unit 80 performs TVG processing on the detection data, and detects a detection image based on the signal level of the detection data after the TVG processing (corresponding to the amplitude value of the pulse compression signal after range side lobe suppression). Display on the display screen.

[Configuration of Range Sidelobe Suppression Unit]
Next, a specific configuration of the range side lobe suppressing unit 70 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 reference position detection unit 71, a local peak detection unit 72 as a local peak position detection unit, a suppression candidate range setting unit 73, a suppression exclusion range setting unit 74, and a suppression processing unit 75. It has.

The reference position detection unit 71 detects a reference position D _REF that is a depth position where the signal level of the pulse compression data is equal to or higher than the reference position detection threshold ThE1 before and after moving from the shallow side to the deep side.

The local peak detection unit 72 detects a local peak position that is a depth position of the underwater depth of the local peak in the pulse compression signal. In the present embodiment, the local peak detector 72 has a predetermined local peak P _X (X = A, B, of the local peaks of the pulse compression data in a predetermined range extending from the reference position D _REF to the deep side. ...) is detected.

Specifically, the local peak detecting unit 72 sequentially detects the local peak P _X from the reference position P _REF towards the deep side of the depth. The local peak detector 72 does not detect the predetermined local peak when the signal level of the predetermined local peak is equal to or lower than the signal level of the local peak detected immediately before the predetermined local peak. On the other hand, the local peak detecting unit 72, the signal level of the predetermined local peak is higher than the signal level of the local peaks detected immediately before said predetermined local peak, detecting the predetermined local peak P _X. Local peak detecting unit 72, as the local peak _{P X,} said local peak _P local peak position is the depth position of the _{X D X (X = A,} B, ...), and the local peaks _{P X} signal level _{E X} of the (X = A, B,...) Is detected.

The suppression candidate range setting unit 73 sets the depth range set based on the local peak position D _X as a suppression candidate range Z _X that is a range side lobe suppression candidate. In the present embodiment, the suppression candidate range setting unit 73 uses the local peak position D _X detected by the local peak detection unit 72 as a reference, and sets a predetermined range that is shallower than the local peak position D _X as the suppression candidate range Z. Set as _X (X = A, B,...). The predetermined range used here is set based on, for example, the waveform of the range side lobe estimated from the transmitted ultrasonic pulse signal.

The suppression exclusion range setting unit 74 sets a range in which the signal level of the pulse compression data in the suppression candidate range Z _X is equal to or greater than the suppression exclusion determination threshold ThE2 _X (X = A, B,...) As a non-range sidelobe suppression candidate. The suppression exclusion range EXZ _X (X = A, B,...) Is set. In the present embodiment, the suppression exclusion range setting unit 74 sets a range in which the signal level in the suppression candidate range Z _X is equal to or greater than the suppression exclusion determination threshold ThE2 _X (X = A, B,...) As the suppression exclusion range EXZ _X. To do. Suppression exclusion range setting unit 74, sets the suppression exclusion determination threshold The2 _X, based on the signal level E _X of the local peak P _X found in a local peak detecting unit 72, the range side lobe approximate waveform of a pulse compressed data To do.

Suppression processing section 75, the suppression range excluding the suppression exclusion range EXZ _X from the suppression candidate range _{Z X Z X '(X =} A, B, ...) in the signal level of the pulse compressed data suppression limit value _{E LMTX} above and The signal level is suppressed so as not to occur. Thereby, the suppression process part 75 produces | generates detection data.

[Underwater detection method]
FIG. 3 is a flowchart for explaining the underwater detection method according to the present embodiment. Below, it demonstrates using the waveform shown in FIG.5 and FIG.6 as pulse compression data used as the process target by the underwater detection method.

  The underwater detection device 10 performs drive signal generation control so as to transmit the frequency-modulated ultrasonic pulse signal STx (step S1). The underwater detection device 10 receives the echo signal ERx of the ultrasonic pulse signal STx and generates a reception signal (step S2). The underwater detection device 10 performs pulse compression processing on the received signal to generate pulse compression data (step S3).

Next, in step S4, the local peak of the pulse compression data is depth range to be detected, the local peak detection range Z _P is set. Figure 4 is a flow chart illustrating the steps in step S4 in detail, is a flow chart showing the process of setting the local peak detection range Z _P.

In step S4, the reference position detection unit 71 sets a reference position detection threshold ThE1. Specifically, the reference position detection unit 71 calculates an average value (noise level) of the pulse compression data for each depth region divided at equal intervals in the depth direction (step S41). Next, in step S42, the reference position detection unit 71 sets the average value having the smallest value among the pulse compression data of each region for which the average value is calculated as the first offset value E _OFF1 . In step S43, the reference position detection unit 71 sets a level higher than the first offset value E _OFF1 by a predetermined level ΔE1 as the reference position detection threshold ThE1.

In the present embodiment, as shown in FIG. 5, the average value of the deepest region among the depth regions divided at equal intervals is the minimum value. Therefore, the average value of the region is set as the first offset value E _OFF1, and a level higher by ΔE1 than the first offset value E _OFF1 is set as the reference position detection threshold ThE1. In the present embodiment, the predetermined level ΔE1 is a level difference value between the peak level of the main lobe and the peak level of the range side lobe. Thereby, a range side lobe can be suppressed appropriately.

Next, the reference position detection unit 71 detects the reference position D _REF using the reference position detection threshold ThE1. FIG. 6 is an enlarged view of the predetermined range in the depth direction in FIG. 5, and is a diagram for explaining the detection of the reference position D _REF , the local peak detection range Z _P and the local peaks P _{A to} P _C. It is. FIG. 7 is an enlarged view of a part of FIG. 6 for explaining the detection of the reference position _DREF .

  In step S44, the reference position detection unit 71 compares the signal level E (n) of a point of interest (n) in the depth direction with the reference position detection threshold ThE1. When the signal level E (n) of the attention point (n) is equal to or higher than the reference position detection threshold ThE1 (YES in step S45), the process of step S46 is performed. On the other hand, when the signal level E (n) of the target point (n) is lower than the reference position detection threshold ThE1 (NO in step S45), the target point of interest moves to the deeper side (step S48), The signal level of the point of interest is compared again with the reference position detection threshold ThE1 (step S44). Then, steps S45, 48 and S44 are repeated until the signal level of the attention point moving to the deep side becomes equal to or higher than the reference position detection threshold ThE1.

  Before the step S48 is performed, it is determined in step S51 whether or not the depth position of the point of interest (n) is the end of the pulse compression data. When the depth position of the point of interest (n) is not the end of the pulse compression data (NO in step S51), the point of interest moves to the deeper side. On the other hand, when the depth position of the attention point (n) is the end of the pulse compression data (YES in step S51), this flow ends.

When the signal level E (n) of the attention point becomes equal to or higher than the reference position detection threshold ThE1 (YES in step S45), the reference position detection unit 71 receives the attention point n that is one shallower than the attention point (n) in step S46. The signal level E (n−1) of −1 is compared with the reference position detection threshold ThE1. When the signal level E (n−1) is lower than the reference position detection threshold ThE1 (YES in step S47), the reference position detection unit 71 determines the depth position of the signal level E (n) as the reference position in step S49. Set as D _REF (see FIG. 7). Then, in step S50, the predetermined range of the deep side from the reference position _{D REF} is set as a local peak detection range _{Z P} (see FIG. 6).

  In step S47, when the signal level E (n-1) is equal to or higher than the reference position detection threshold ThE1 (No in step S47), the point of interest is moved to one deeper side (step S48), and the signal of the point of interest The level is compared with the reference position detection threshold ThE1 again (step S44).

Next, in step S5, the local peak P _X (local peak position D _X and signal level E _X ) of the pulse compression data is detected in the local peak detection range Z _P set as described above. Specifically, the local peak detecting unit 72 detects local peaks in order from the reference position _PREF toward the deeper side in step S5. Here, when the signal level of the predetermined local peak is equal to or lower than the signal level of the local peak detected immediately before the predetermined local peak, the local peak detection unit 72 does not detect the predetermined local peak. On the other hand, the local peak detecting unit 72, the signal level of the predetermined local peak is higher than the signal level of the local peaks detected immediately before said predetermined local peak, detecting the predetermined local peak P _X.

Step S5 will be described with reference to FIG. In step S5, the local peak detector 72 sequentially detects local peaks from the reference position _DREF toward the deeper side. Local peak detector 72, for the first local peak P _A, since the local peaks detected just before is not present, to detect the local peak P _A. Next, for the local peak P _B , the local peak detection unit 72 has a signal level E _B of the local peak P _B higher than the signal level E _A of the local peak P _A detected immediately before. Peak P _B is detected. On the other hand, the local peak detecting unit 72, the local peak P _Z, since the signal level of the local peak P _Z is less than or equal to the signal level E _B of the local peak P _B detected immediately before, the local peak P _Z Is not detected. In this manner, in the present embodiment, the local peak detecting unit 72 detects the three local peaks P _A to P _C shown in FIG.

Next, in step S6, suppression candidate range setting unit 73 sets a suppression candidate range _{Z X.} In the present embodiment, as shown in FIG. 8, the suppression candidate range setting unit 73, a predetermined range over a shallow side from the local peak P _A to P _C, respectively, set as the suppression candidate range Z _A to Z _C . In the present embodiment, the predetermined range is set based on the waveform of the range side lobe estimated from the transmitted ultrasonic pulse signal.

Next, in step S7, the suppression exclusion range setting unit 74 sets the suppression exclusion range EXZ _X. Specifically, the suppression exclusion range setting unit 74 sets the suppression exclusion determination threshold ThE2 _X , and suppresses the range in which the signal level of the pulse compression data in the suppression candidate range Z _X is equal to or greater than the suppression exclusion determination threshold ThE2 _X. Set as range EXZ _X.

In the present embodiment, as described above, the range in which the signal level of the pulse compression data in the suppression candidate range Z _X is suppressed negative determination threshold The2 _X above, is set as the suppression exclusion ranges EXZ _X, which Not limited to. For example, the suppression exclusion range EXZ _X includes a predetermined range extending from the shallowest position to the shallower side in a range that is equal to or greater than the suppression exclusion determination threshold ThE2 _X , and a predetermined range extending from the deepest position to the deeper side in the depth range. You may make it include at least any one of these. In this way, the suppression exclusion range EXZ _X, can be widened than in the case of setting only to the extent that the suppression exclusion determination threshold The2 _X above. Therefore, it is possible to avoid the waveform included in the suppression exclusion range EXZ _{X from} becoming too steep, and to make the waveform natural.

Range in the present embodiment, the suppression exclusion range setting unit 74, in step S7, the signal level of the pulse compressed data in the suppression candidate range Z _A is to be suppressed negative determination threshold The2 _A more corresponding to the suppression candidate range Z _A Is set as a suppression exclusion range EXZ _{A that} is outside the range sidelobe suppression candidates. Similarly, the suppression exclusion range setting unit 74 sets suppression exclusion ranges EXZ _B and EXZ _C corresponding to the suppression candidate ranges Z _B and Z _B in step S7.

FIG. 9 is a diagram for explaining the setting of the suppression exclusion range. Hereinafter, the setting of the suppression exclusion range EXZ _B corresponding to the suppression candidate range Z _B will be described. Suppression exclusion range setting unit 74, in step S7, the suppression exclusion determination threshold The2 _B, set on the basis of a signal level E _B of the local peak P _B, in the range side lobe approximate waveform of a pulse compressed data.

Specifically, the suppression exclusion range setting unit 74 uses the point where the signal level is lower than the local peak P _B by a predetermined level ΔE2 as a reference point, and the deepest point in the range sidelobe approximate waveform matches the reference point. the waveform is set as the suppression exclusion determination threshold The2 _B. In this embodiment, ΔE2 is set to the same value as ΔE1 described above.

In the present embodiment, a waveform as shown in FIG. 9 is set as the range sidelobe approximate waveform. Specifically, as a range sidelobe approximate waveform, a range from the deepest point Pt ₁ to a predetermined point Pt ₂ on the shallow side is set to a constant value, and a predetermined point Pt ₃ on the shallower side from the point Pt _2. In the range extending over, a waveform is set such that the signal level gradually decreases from the deep side to the shallow side. Specifically, from the point Pt ₂ to the point Pt ₃ , an exponential function with the position in the depth direction as the bottom and the coefficient set appropriately is used.

Suppression exclusion range setting unit 74, in step S7, compares the signal level of each point of the pulse compressed data in the suppression candidate range Z _B, and suppression exclusion determination threshold The2 _B. If the signal level at each point is equal to or greater than the suppression exclusion determination threshold ThE2 _B , the suppression exclusion range setting unit 74 includes the point in the suppression exclusion range EXZ _B (see FIG. 9).

Then, the suppression exclusion range setting unit 74, for the suppression candidate range _{Z A} and _{Z C,} as in the case described above, setting the suppression exclusion range EXZ _A and EXZ _C corresponding to each of the suppression candidate range _{Z A} and _{Z C} (Not shown).

Finally, in step S8, range side lobe suppression processing is performed. In step S8, the signal level of the pulse compression signal in the suppression range Z _X ′ is suppressed so as to be approximately the same as the noise level near the shallowest depth position in the suppression candidate range Z _X. Specifically, in step S8, the suppression processing unit 75 sets a suppression limit value E _LMTX . The suppression processor 75, as pulse compression data is not the suppression limit value E _LMTX or in suppression range Z _{X 'excluding} the suppression exclusion range EXZ _X from the suppression candidate range Z _X, the signal level of the pulse compressed data Repress.

In the present embodiment, in step S8, the suppression processing unit 75 sets a suppression limit value E _LMTA corresponding to the suppression range Z _A ′ obtained by removing the suppression exclusion range EXZ _A from the suppression candidate range Z _A. And the suppression process part 75 suppresses the signal level of pulse compression data so that pulse compression data may not become more than the suppression limit value _ELMTA . Similarly, the suppression processing unit 75 sets suppression limit values E _LMTB and E _LMTC corresponding to the suppression ranges Z _B ′ and Z _C ′, respectively, and the pulse compression data does not _{exceed the} suppression limit values E _LMTB and E _LMTC. As described above, the signal level of the pulse compression data is suppressed.

FIG. 10 is a flowchart showing in detail the process in step S8. FIG. 11 is a diagram for explaining the setting of the suppression limit value _ELMTX . Hereinafter, suppression of pulse compression data in the suppression candidate range Z _B will be described using one of the three suppression candidate ranges, specifically, the suppression candidate range Z _B as an example, with reference to FIGS. .

First, the suppression processing unit 75 sets a suppression limit value _ELMTB . Specifically, suppression processing section 75, the shallowest end side relative to the predetermined depth and a predetermined depth range of the shallow side from the end portion, the deep from the end portion side in the suppression candidate range Z _B a range, respectively, and the first region _{Z 1} and a second region _{Z 2} (see FIG. 11). Then, for each region of the first region Z ₁ and a second region Z _2, calculates the average value of the pulse compression data (noise level) (step S81), the average value of the lower of the average second The offset value E is _OFF2 . In step S82, the suppression processing unit 75 sets a value that is higher _than the second offset value E _OFF2 by a predetermined level as the suppression limit value E _LMTB .

Next, the suppression processing unit 75 compares the signal level at each point in the suppression range Z _B ′ with the suppression limit value E _LMTB and reduces the signal level at each point based on the comparison result.

In step S83, the suppression processing unit 75 compares the signal level E (n) at the point of interest n with the suppression limit value _ELMTB . In the present embodiment, when the process of step S83 is first performed, the deepest point in the suppression range Z _B ′ is set as the attention point. When the signal level E (n) is lower than the suppression limit value E _LMTB (NO in step S84), the suppression processing unit 75 does not _{perform the} suppression process for the _target point n and sets the depth position of the _target point to one. Move to the shallow side (step S86). If the shallowest point in the suppression range Z _B ′ is set as the attention point, and the signal level at that point is lower than the suppression limit value E _LMTB , the depth position of the attention point is moved to one deeper side. May be.

On the other hand, when the signal level E (n) is _{equal to} or greater than the suppression limit value _ELMTB (YES in step S84), the suppression processing unit 75 divides the predetermined value ΔE3 from the signal level E (n) at the point of interest n, and after the division Is set to a new signal level E (n) at the point of interest n (step S85). In the present embodiment, the predetermined value ΔE3 is a noise PP value (Peak-to-Peak value) in the pulse compression data.

After that, the suppression processing unit 75 returns to Step S83 and compares the newly set signal level E (n) with the suppression limit value _ELMTB . When the signal level E (n) is lower than the suppression limit value _ELMTB (NO in step S84), the suppression processing unit 75 moves the depth position of the point of interest to the shallower side (step S86), and the signal level If E (n) is _{equal to} or greater than the suppression limit value _ELMTB (YES in step S84), the predetermined value ΔE3 is again divided from the signal level E (n). Thus, the above-described division processing is performed at each point until the signal level at each point becomes equal to or less than the suppression limit value _ELMTB .

When the point of interest reaches the end point of the suppression range Z _B ′, specifically, the shallowest point in the suppression range Z _B ′ (YES in step S87), the suppression processing in the suppression processing unit 75 ends.

The suppression processing section 75, the suppression as described above, is also performed for the suppression range Z _{A 'and} Z _C'.

  FIG. 12 is a diagram illustrating pulse compression data before suppression processing and detection data that is pulse compression data subjected to suppression processing. As shown in FIG. 12, in the pulse-compressed data before performing the suppression processing as described above, the echo of the fish with a bottom is somewhat difficult to discriminate due to the range side lobe of the echo at the bottom of the sea. On the other hand, since the signal level of the range side lobe is reduced by performing the suppression process as described above (see the thick line waveform in FIG. 12), it becomes easy to identify the echo of the fish with a bottom.

[effect]
As described above, in the underwater detection method according to the present embodiment, the suppression candidate range Z _X comprising the suppression candidate range side lobe, the signal level of the pulse compression signal is suppressed. Thereby, the range side lobe can be suppressed. Further, in the suppression candidate range Z _X , the signal level of the data point smaller than the suppression exclusion determination threshold ThE2 _X set based on the range sidelobe approximate waveform of the ultrasonic pulse signal is suppressed. Thereby, the range side lobe can be suppressed while maintaining the signal level of the desired echo.

  Therefore, in the underwater detection method of the present embodiment, range side lobes due to targets with high echo signal levels such as the seabed can be appropriately suppressed.

Moreover, in the above-described underwater detection method, the suppression candidate range Z _X is set to the local peak P _X of the pulse compressed signal to the reference. In this way, the range side lobe of the main lobe having the local peak P _X can be surely included in the suppression candidate range Z _X , so that the range side lobe can be prevented from leaking from the suppression candidate range Z _X. This allows appropriately setting the suppression candidate range Z _X.

Further, in the underwater detection method, for the depth range of the set suppression exclusion determination threshold The2 _X or on the basis of the range side lobe approximate waveform of an ultrasonic pulse signal, the signal level is not suppressed. Thus, for example, as disclosed in Patent Document 2, the second threshold value (corresponding to the suppression exclusion determination threshold The2 _X according to this embodiment) compared with the case that is set at a predetermined value, the desired echo incorrectly Thus, it is possible to reduce the risk of being included in the suppression range Z _X ′ and the risk that the range side lobes that are originally unnecessary remain without being suppressed.

Further, in the above-described underwater detection method sets a range where suppression of the range side lobe is not performed as the suppression exclusion range EXZ _X, suppression candidate range Z _X suppression range excluding the suppression exclusion range EXZ _X from Z _{X ',} The signal level of the pulse compression signal is suppressed. As a result, the range in which the range side lobe is desired to be suppressed is appropriately narrowed down as the suppression range Z _X ′, and the range side lobe suppression process can be performed on the range.

Further, in the above-described underwater detection method, the local peak detection range Z _P of local peak position D _X is the depth position of the local peak P _X is detected is set. This eliminates local peaks that do not need to suppress the range side lobe (for example, local peaks at extremely shallow depth positions), thereby reducing signal processing time.

In the underwater detection method, the reference position D _REF is set that is a depth position at which the signal level is equal to or higher than the reference position detection threshold ThE1 before and after moving from the shallow side to the deep side. Then, a predetermined depth range over a deeper side than the reference position D _REF is set as a local peak detection range Z _P. Thus, it is possible to detect a local peak P _X above desired signal levels of the echo, further, you can set the desired suppression candidate range Z _X corresponding to the local peak P _X. Further, since it is not necessary to perform signal processing for the local peak below the reference position detection threshold ThE1, the signal processing time can be shortened.

  In the underwater detection method, the reference position detection threshold ThE1 is set based on the pulse compression data. Thereby, an appropriate reference position detection threshold ThE1 based on the pulse compression data can be set.

In the underwater detection method, the reference position detection threshold ThE1 is set to a level higher by a predetermined level ΔE1 than the first offset value E _OFF1 calculated based on the pulse compression signal. As a result, the reference position detection threshold ThE1 can be appropriately set without being affected by the noise level that changes depending on the surrounding environment.

Further, in the underwater detection method, a plurality of suppression range corresponding to each of the plurality of local peaks _{P A ~P C Z A'~Z C} ' is set, the suppression range _{Z A'~Z C'} for the signal level Is suppressed. Thereby, even when there are a plurality of echoes whose range side lobes are to be suppressed, these range side lobes can be appropriately suppressed.

  In the underwater detection method, the local peak is detected so that the signal level increases from the shallow side to the deep side.

For example, when suppressing the seaside range side lobe that occurs near the echo of a fish near the sea floor (a fish located slightly shallower than the sea floor), the range side lobe may be suppressed as follows. Specifically, if the range side lobe caused by the echo of the sea floor with a high signal level located on the shallow side is suppressed, the range side lobe caused by the echo of the sea floor with a low signal level located on the deep side is not suppressed. May be. Therefore, by detecting the local peak P _X as described above, it is possible to shorten the signal processing time.

Further, in the above-described underwater detection method, a signal level E _X of the detected local peaks P _X, wherein on the basis of the range side lobe approximate waveform of an ultrasonic pulse signal, suppressing negative determination threshold The2 _X is set. Thus, the range side lobe approximate waveform, it is possible to properly offset in the signal level direction, it can be set suppression exclusion determination threshold The2 _X better.

In the underwater detection method, the approximate range sidelobe waveform of the ultrasonic pulse signal is a waveform in which the signal level decreases from the deep side to the shallow side in at least a part of the depth range. As shown in FIG. 17, the signal level of the range side lobe gradually decreases with distance from the main lobe. Therefore, the suppression exclusion determination threshold ThE2 _X can be appropriately set by setting the range sidelobe approximate waveform to a waveform in which the signal level decreases from the deep side to the shallow side in at least a part of the depth range. .

In the underwater detection method, an exponential function is used as the range sidelobe approximate waveform with the position in the depth direction as the bottom and the coefficient set appropriately. By using such an exponential function, it is possible to set the suppression exclusion determination threshold ThE2 _X that approximates the envelope (change tendency) of the signal level peak of the range sidelobe, and thus more appropriate suppression exclusion determination threshold ThE2 _X can be set.

In the underwater detection method, the signal level of the pulse compression signal in the suppression range Z _X ′ is suppressed so as to be approximately the same as the noise level near the shallowest depth position in the suppression candidate range Z _X. As a result, the range side lobe can be suppressed to the same level as the surrounding noise level, so that the detection data can have a natural waveform.

In the underwater detection method, the signal level of the pulse compression data within the suppression range Z _X ′ is suppressed so as not to exceed the suppression limit value E _LMTX . As a result, the data in the suppression exclusion range EXZ _X (bottom fish echo) can be displayed so as to protrude from the data (noise) in the suppression range Z _X ′, so that the bottom fish echo can be easily identified. Become.

In the underwater detection method, in the pulse compression data in the suppression range Z _X ′, the signal level at each depth position is divided by a predetermined value. Thereby, the data in the suppression range Z _X ′ can be shaped like a natural noise.

In the underwater detection method, the suppression limit value E _LMTX is calculated based on the noise level in a predetermined range including the shallowest depth position in the suppression candidate range Z _X. Accordingly, data after suppressing process in the suppression range Z _{X 'can} be suppressed from becoming excessively higher than the ambient noise level. Therefore, it is possible to prevent the data in the suppression exclusion range EXZ _X (bottom fish echo) from being obscured by the data (noise) in the suppression range Z _X ′.

Further, in the above underwater detection system, together with the range side lobe due to the high target object of the echo signal level of the sea bottom or the like can be appropriately suppressed, it can be appropriately set the suppression candidate range Z _X.

  As mentioned above, although embodiment of this invention was described, this invention is not limited to these, A various change is possible unless it deviates from the meaning of this invention.

(1) In the above embodiment, the detected local peaks P _X is such that the signal level increases toward the shallow side to deep side, although detecting the local peak P _X, but this shall, it may detect all local peaks in the local peak detection range Z _P.

(2) In the above embodiment, it detects the local peak P _X in the local peak detection range Z _P, but this shall may detect all local peaks in the pulse compression data. In this case, it is possible to omit the setting of setting the reference position D _REF local peak detection range Z _P.

(3) In the above embodiment, the reference position detection threshold ThE1 is set to the first offset value E _OFF1 that is the smallest of the average values of the regions divided at equal intervals in the depth direction, and the first offset value E _A value higher than the _OFF1 by the predetermined level ΔE1 is set as the reference position detection threshold ThE1, but this is not restrictive. For example, the average value calculated at a predetermined depth range may be a first offset value E _OFF1, also the minimum value in the pulse compressed data may be first offset value E _OFF1.

  (4) In the above embodiment, the reference position detection threshold ThE1 is set based on the pulse compression data, but is not limited to this and may be a fixed value.

(5) Further, in the above embodiment, the suppression candidate range Z _X is set as the suppression candidate range Z _A as a predetermined range extending from the local peak position D _X to the shallow side. Z _X may be set based on the local peak position D _X. For example, a position shallower than the local peak position D _X by a predetermined position may be used as a reference, a predetermined range extending from the reference to the shallower side may be set as a suppression candidate range, and further, a predetermined range extending from the local peak position D _X to the shallower side, and Both the predetermined range extending to the deep side may be set as the suppression candidate range.

(6) In the above embodiment, the suppression exclusion determination threshold The2 _X, and a bottom position in the depth direction, but is set based on the exponential function to set the coefficient as appropriate, but this shall, ultrasonic pulses It may be based on the approximate range sidelobe waveform of the signal. For example, suppression exclusion determination threshold The2 _X may be set based on a function that approximates the envelope of the peaks of the signal level of the range sidelobes along the depth direction. Specifically, the function may be a linear function approximated to the envelope, or may be a stepped function approximated to the envelope. Further, for example, suppression exclusion determination threshold The2 _X may be set based on the sine wave.

(7) In the above embodiment, the suppression limit value E _LMTX is based on the shallowest end portion of the suppression candidate range Z _X as a reference, a predetermined range on the shallow side from the end portion, and a predetermined range on the deep side from the end portion. Although it is calculated based on the average value of each range, this is not restrictive. For example, the suppression limit value E _LMTX may be calculated based on an average value of a predetermined range including the end portion or the entire range of pulse compression data.

(8) In the embodiment described above, the signal level point equal to or higher than the suppression limit value E _LMTX in the suppression range Z _X ′ is divided by the noise _PP value so as not to exceed the suppression limit value E _LMTX. However, the present invention is not limited to this, and division may be performed for each predetermined value other than the noise P-P value.

(9) In the above embodiment, the suppression limit value E _LMTX is set, and each point is suppressed so that the signal level at each point in the suppression range Z _X ′ does not exceed the suppression limit value E _LMTX . This is not the case. For example, each point that is a candidate for suppression is set so as to be included between a predetermined range on the higher signal level and a predetermined range on the lower signal level with reference to a predetermined level (noise level, etc.) Also good. That is, even if the suppression limit value E _LMTX is not calculated, the signal level of the pulse compression data in the suppression range Z _X ′ is approximately the same as the noise level near the shallowest depth position in the suppression candidate range Z _X. Any suppression method may be used.

  (10) FIG. 13 is a flowchart showing the operation of the underwater detection method according to the modification. In the underwater detection method according to the present modification, among the data points of the pulse compression signal in the suppression candidate range, the data level of the data point is smaller than the suppression limit value for the data point whose signal level is smaller than the suppression exclusion determination threshold. It is suppressed so as not to become.

Specifically, the underwater detection method according to the present modification differs from the underwater detection method according to the above embodiment, and step S7 for setting the suppression exclusion range EXZ _X is omitted as shown in FIG. Then, the above-described embodiment the step S7 in done have suppression exclusion determination threshold The2 _X settings have been carried out separately in a step S9. Thereafter, as will be described in detail later, range side lobe suppression processing different from that in the above embodiment is performed. In the following, differences from the above embodiment will be mainly described, and description of steps similar to those of the above embodiment will be omitted by giving the same reference numerals in the drawings or by quoting the same reference numerals. To do.

  In the underwater detection method according to this modification, the steps until the suppression candidate range is set, that is, the steps from Step S1 to Step S6, are performed in the same manner as in the above embodiment. By performing steps S1 to S6, a suppression candidate range that is a range sidelobe suppression candidate is set in the pulse compression data.

  Next, in step S9, a suppression exclusion determination threshold is set. The suppression exclusion determination threshold is set based on the local peak signal level and the range sidelobe approximate waveform of the pulse compression data, as in step S7 of the above embodiment. In addition, this step S9 may be performed before step S6 or may be performed in parallel with step S6.

Next, in step S10, range side lobe suppression processing is performed. FIG. 14 is a flowchart showing in detail the process in step S10. FIG. 15 is a waveform diagram showing an example of pulse compression data, and is a diagram for explaining the step S10. The pulse compression data shown in FIG. 15 is the same as that shown in FIG. That is, three suppression candidate ranges are set for the pulse compression data shown in FIG. 15, and range side lobe suppression processing is performed for each suppression candidate range. Hereinafter, with reference to FIGS. 14 and 15, suppression of pulse compression data in the suppression candidate range Z _B will be described using one of the three suppression candidate ranges, specifically, the suppression candidate range Z _B as an example. .

  Step S10 is obtained by adding several steps to each step (see FIG. 10) in step S8 of the above embodiment.

First, in step S10, the first region Z ₁ and a second region Z ₂ as in the case of the embodiment is set, the average value is calculated for each area (step S81). Thereafter, the lower the average value of is set as a second offset value _{E OFF2,} predetermined level higher values from the second offset value _{E OFF2} is set as the suppression limit value _{E LMTB} (step S82).

Next, in step S11, the signal level E of the target point n (n) and the suppression exclusion determination threshold The2 _B are compared. In the present embodiment, when the process of the first step S11 is performed, the point of the deepest side in the suppression candidate range Z _B is set as a target point. When the signal level E of the target point (n) is equal to or greater than the suppression exclusion determination threshold The2 _B (YES in step S12), the the target point is suppression processing is not performed is determined to suppress excluded. Then, the depth position of the attention point moves to the shallower side (step S86). When the shallowest point in the suppression candidate range Z _B is set as the attention point, and the signal level at that point is equal to or greater than the suppression exclusion determination threshold ThE2 _B , the depth position of the attention point is moved to the deeper side. May be.

When the signal level E (n) is lower than the suppression exclusion determination threshold The2 _B (NO in step S12), the next in step S83, the signal level E (n) and the suppression limit value _{E LMTB} are compared. When the signal level E (n) is lower than the suppression limit value E _LMTB (NO in step S84), the suppression process is not performed for the attention point n, and the depth position of the attention point moves to one shallower side.

On the other hand, when the signal level E (n) is _{equal to} or greater than the suppression limit value _ELMTB (YES in step S84), the suppression process is performed for this attention point. Specifically, a predetermined value ΔE3 is divided from the signal level E (n) at the point of interest n, and the signal level E (n) after the division is set to a new signal level E (n) at the point of interest n. (Step S85). In this modification as well, as in the case of the above embodiment, the predetermined value ΔE3 is set as the PP value of noise in the pulse compression data.

Then, the process returns to step S83, the newly set signal level E (n) is compared with the suppression limit _{E LMTB,} when the signal level E (n) is lower than The2 _B (NO in step S84), the point of interest When the signal level E (n) is _{equal to} or greater than the suppression limit value _ELMTB (YES in step S84), the signal level E (n) is again set to the predetermined value ΔE3. Is divided. As a result, the above-described suppression processing (division processing) is performed until the signal level at the point becomes equal to or less than the suppression limit value _ELMTB .

The end point of the target point suppression candidate range Z _B, specifically, when it reaches the shallowest side point in the suppression candidate range Z _B (YES in step S87), the suppression process is terminated. The suppression process as described above is similarly performed for the suppression candidate ranges Z _A and Z _C.

The suppression process at each point will be described with reference to FIG. When the target point is _{P 1,} in step S12, the signal level of the point _{P 1} is determined to be suppressed exclusion determination threshold The2 _B above (YES in step S12). Therefore, for the P _1, suppression processing is skipped.

When the target point is _{P 2,} in step S12, the signal level of the point _{P 2} is determined to be lower than the suppression exclusion determination threshold The2 _B (NO in step S12), the process proceeds to step S83, the signal level of the point _{P 2} Is compared with the suppression limit _ELMTB . Then, the signal level of the point _{P 2} is determined to be lower than the suppression limit _{E LMTB} (NO in step S84). Thus, with respect to P _2, suppression processing is not performed.

When the attention point is P _3, it is determined that the signal level of the point P ₃ is lower than the suppression exclusion determination threshold ThE2 _B (NO in step S12), and then is determined to be _{equal to} or higher than the suppression limit value E _LMTB. (YES in step S84). Therefore, for the point P _3, the suppression process is performed. Specifically, for the point _{P 3,} until the signal level E of the point P3 is less than the suppression limit _{E LMTB,} performed repeatedly divide by Derutai3. This allows the signal level of the point _{P 3} below suppression limit _{E LMTB.}

  As described above, even if the above-described suppression processing is performed in the suppression range without setting the suppression exclusion range and the suppression range as in the present modification, the signal level of the echo of the seabed or the like is the same as in the above embodiment. Range side lobes due to high targets can be appropriately suppressed.

(11) FIG. 16 is a flowchart showing the operation of the underwater detection method according to the modification. The underwater detection method according to the present modification differs from that shown in FIG. 14 in that the signal level is lower than the suppression exclusion determination threshold ThE2 _B and is _{equal to} or greater than the suppression limit value E _LMTB for each point of the pulse compression data within the suppression range. In this case, the same suppression process as that described above is performed. Even in this case, as in the case of the underwater detection method according to the above-described modification, among the data points of the pulse compression signal in the suppression candidate range, the signal of the data point for the data point whose signal level is smaller than the suppression exclusion determination threshold value. It can be suppressed so that the level does not exceed the suppression limit value.

  INDUSTRIAL APPLICABILITY The present invention can be widely applied as an underwater detection method and an underwater detection apparatus that transmit ultrasonic pulse signals in water and generate underwater detection data from echoes of fish schools or seabed echoes.

DESCRIPTION OF SYMBOLS 10 Underwater detection apparatus 50 Pulse compression part 70 Range sidelobe suppression part 72 Local peak detection part (local peak position detection part)
73 the suppression candidate range set 75 suppression unit 74 suppresses exclusion range setting unit _{D X (D A, D B} , D C) local peak position _{EXZ X (EXZ A, EXZ B} , EXZ C) suppression exclusion ranges P _X (P _{A, P} B, _P C) local peak _{Z X (Z A, Z B} , Z C) suppression candidate range _{Z X '(Z A',} Z B ', Z C') suppression range

Claims (14)

A step of pulse-compressing a reception signal obtained from a reflected echo of a frequency-modulated ultrasonic pulse signal transmitted into water to generate a pulse-compressed signal;
Detecting a plurality of local peak positions that are depth positions of the depth of the local peak in the pulse compression signal; and
Setting each depth range set based on each local peak position as a suppression candidate range to be a range sidelobe suppression candidate; and
Among the data points of the pulse compression signal in each of said suppression candidate range, the signal level is, the ultrasonic pulse signal of the range side lobe is smaller than the suppression exclusion determination threshold set based on the approximate waveform data points, the signal A step of suppressing the level ;
Setting each depth range in which the signal level in each suppression candidate range is equal to or greater than the suppression exclusion determination threshold as a suppression exclusion range that is not a range sidelobe suppression candidate; and
Including
In the step of suppressing the signal level, the signal level of the pulse compression signal is suppressed in a plurality of suppression ranges excluding the suppression exclusion range among the plurality of suppression candidate ranges. . The underwater detection method according to claim 1 ,
In the step of setting the suppression exclusion range, the suppression exclusion range is determined from the shallowest position in the depth range that is equal to or greater than the suppression exclusion determination threshold, the predetermined range from the shallowest side, and the deepest position in the depth range. An underwater detection method, characterized in that the underwater detection method is set to include at least one of a predetermined range over a deeper side. In the underwater detection method according to claim 1 or 2 ,
An underwater detection method, further comprising the step of setting a local peak position detection range that is a depth range in which the local peak position is detected. In the underwater detection method of Claim 3 ,
In the pulse compression signal, the method further includes a step of detecting a reference position that is a depth position at which the signal level is equal to or higher than a reference position detection threshold before and after moving from the shallow side to the deep side of the underwater depth,
In the step of setting the local peak position detection range, a predetermined depth range from the reference position to a deeper side than the reference position is set as the local peak position detection range,
The underwater detection method, wherein in the step of setting the suppression candidate range, a predetermined range extending from the local peak position to a side shallower than the local peak position is set as the suppression candidate range. The underwater detection method according to claim 4 ,
An underwater detection method, further comprising the step of setting the reference position detection threshold based on the pulse compression signal. The underwater detection method according to claim 5 ,
An underwater detection method, wherein in the step of setting the reference position detection threshold, a level higher than a noise level calculated based on the pulse compression signal by a predetermined level is set as the reference position detection threshold. The underwater detection method according to any one of claims 1 to 6 ,
In the step of detecting the local peak position, a plurality of the local peak positions are detected in order from the shallow side of the underwater depth to the deep side, and a predetermined local peak among the plurality of local peak positions detected in order is detected. When the signal level at the peak position is equal to or lower than the signal level at the local peak position detected immediately before the predetermined local peak position, the predetermined local peak position is not detected, and the signal level at the predetermined local peak position is The underwater detection method, wherein the predetermined local peak position is detected when the signal level is higher than the signal level at the local peak position detected immediately before the predetermined local peak position. The underwater detection method according to any one of claims 1 to 7 ,
The method further includes the step of setting the suppression exclusion determination threshold based on the signal level at the local peak position detected in the step of detecting the local peak position and the range sidelobe approximate waveform of the ultrasonic pulse signal. An underwater detection method characterized by In the underwater detection method according to any one of claims 1 to 8 ,
The range side lobe approximate waveform of the ultrasonic pulse signal is a waveform in which a signal level decreases from a deep side to a shallow side in at least a part of a depth range. The underwater detection method according to any one of claims 1 to 9 ,
In the step of suppressing the signal level, the signal level of the pulse compression signal within the suppression range is suppressed to be approximately the same as the noise level near the shallowest depth position in the suppression candidate range. An underwater detection method characterized by The underwater detection method according to claim 10 ,
A step of calculating a suppression limit value that is an upper limit value of the signal level of the pulse compression signal within the suppression range;
In the underwater detection method, in the step of suppressing the signal level, the signal level is suppressed so that the signal level of the pulse compression signal within the suppression range does not exceed the suppression limit value. The underwater detection method according to claim 11 ,
In the step of suppressing the signal level, the signal level at each depth position is divided by a predetermined value for each of the pulse compression signals within the suppression range whose signal level is a depth position equal to or greater than the suppression limit value. And the signal level is suppressed by the underwater detection method. The underwater detection method according to claim 11 or 12 ,
In the underwater detection method, in the step of calculating the suppression limit value, the suppression limit value is calculated based on a noise level within a predetermined range including a shallowest depth position in the suppression candidate range. A pulse compression unit that generates a pulse compression signal by pulse-compressing a reception signal obtained from a reflected echo of a frequency-modulated ultrasonic pulse signal transmitted into water;
A local peak position detector for detecting a plurality of local peak positions which are depth positions of the depth of the local peak in the pulse compression signal;
A suppression candidate range setting unit that sets each depth range set based on each local peak position as a suppression candidate range that becomes a suppression candidate for a range sidelobe;
Among the data points of the pulse compression signal in each of said suppression candidate range, the signal level is the ultrasonic pulse signal of the range side lobe approximates less data points than the suppression exclusion determination threshold set based on the waveform, the signal level of and the suppression processing unit to suppress,
A suppression exclusion range setting unit that sets each depth range in which the signal level in each suppression candidate range is equal to or greater than the suppression exclusion determination threshold as a suppression exclusion range that is not a range sidelobe suppression candidate;
With
The underwater detection device, wherein the suppression processing unit suppresses the signal level of the pulse compression signal in a plurality of suppression ranges excluding the suppression exclusion range among a plurality of suppression candidate ranges .

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