JP2019203699A - Noise reduction device of underwater image sonar, noise reduction method, and noise reduction program - Google Patents

Abstract

To display only an underwater actual object.SOLUTION: A noise reduction device processes a reception image from an underwater image sonar of a cross-fan beam system in which a plurality of wave transmission elements and a plurality of wave reception elements cross at 90° relative to each other and are mounted as a linear array, and then outputs a display image to be displayed on a display. The reception image is composed of a plurality of pixels in a first direction and a second direction orthogonal to each other. The noise reduction device has two-dimensional noise average processing means to remove, from the reception image, first direction noise and second direction noise orthogonal to each other, generated due to at least one of vibration between the plurality of wave transmission elements, vibration between the plurality of wave reception elements, and the case of leakage of electromagnetic induction noise into a wiring connecting the plurality of wave transmission elements and the plurality of wave reception elements with an electrical circuit, and then to output the display image.SELECTED DRAWING: Figure 4

Description

  The present invention relates to an underwater image sonar noise reduction device, and more particularly, to a cross fan beam type underwater image sonar noise reduction device.

  As is well known in this technical field, sonar is a general term for devices that detect underwater objects, the state of the seabed, and the like using sound waves that propagate in water. Sonar is roughly classified into active sonar that emits sound waves and passing sonar that captures sound waves emitted by objects. An active sonar is a device corresponding to a radar in a radio wave region, and obtains information on an object using echo localization. On the other hand, passive sonar is a device for analyzing sound emitted from a certain distant object and obtaining information about the object.

  In sonar, a transducer is used. The transducer performs mutual conversion between acoustic energy and electrical energy. The transmitter converts electrical energy into acoustic energy (oscillates sound waves). The receiver converts acoustic energy into electrical energy (listens). These conversions are performed by magnetostriction or piezoelectric effect (including electrostriction).

  Next, the basic principle of the cross fan beam system used in the active sonar will be described.

  A fan beam means a fan-shaped acoustic beam. The multi-beam transmitter and receiver are fixed to the ship bottom or the like so as to be orthogonal to each other. A fan beam is emitted from the transmitter toward the bottom of the sea. Orthogonal receivers also wait for reflection in a fan-shaped beam shape. As a result, the measured values at the respective intersections are obtained, which is called a cross fan beam.

  Various underwater image sonars of the cross fan beam system have been proposed.

  For example, Patent Document 1 discloses a ship detection device in which a sonar using a cross fan beam is fixed and arranged on a water bottom such as a navigation point of a ship in order to detect a ship. In the ship detection device disclosed in Patent Document 1, a transmitting element array and a receiving element array, each of which is a sonar transmitter / receiver at the bottom of the water, intersect each other in a 90 ° relationship, and a plurality of cross It arrange | positions so that a fan beam may be formed in a sea surface direction.

  Patent Document 2 includes transmission elements (X direction x1 to xi, Y direction y1 to yj) arranged in the X (horizontal) direction and the Y (vertical) direction, and converts the transmission waveform into an acoustic signal, respectively. A transmitter is disclosed. Each array element of the transmitter radiates transmission sound (acoustic signal) into water in the transmission beam direction based on a predetermined scanning procedure in a two-dimensional space by controlling the transmission beam direction in the X direction and the Y direction. To do. The plurality of transmission elements are configured as a cross fan beam system composed of one row in each horizontal / vertical direction.

  As each of the transmitting element and the receiving element disclosed in Patent Documents 1 and 2, for example, an electrostrictive vibrator is used.

  On the other hand, techniques for reducing noise have also been proposed.

  For example, Patent Document 3 discloses a passive sonar device including a signal detection circuit having a noise averaging processing unit that averages noise based on frequency domain data from each receiving unit.

  Patent Document 4 discloses a sonobuoy signal processing apparatus including a signal detection circuit having a noise average processing unit that calculates an average level of noise based on frequency domain data from each frequency analysis circuit.

  In Patent Document 3 and Patent Document 4, since the target noise is a sound wave generated by an object other than the target object outside the sonar device, it is called “exogenous noise”.

JP 2004-012237 A JP 2006-064524 A JP-A-8-184661 Japanese Patent Laid-Open No. 10-048307

  As described above, when an electrostrictive vibrator is used as each of the transmitting element and the receiving element, the cross fan beam type underwater image sonar includes a plurality of transmitting electrostrictive vibrators and a plurality of receiving electrostrictive vibrations. The children intersect with each other in a 90 ° relationship and are mounted with high density as a linear array.

  However, it is difficult to completely block vibration between individual electrostrictive vibrators. Further, when the distance between the electric wires connecting the individual electrostrictive vibrators and the electric circuit is shortened due to the miniaturization of the linear array, electromagnetic induction noise may leak into the signal and be superimposed on the wiring such as the electric wires. As a result, a cross-shaped noise as shown in FIG. 1 may be displayed as a received image RI that is an underwater image on the display of the sonar device. 1A shows an example of an actual underwater image (received image) RI, and FIG. 1B is an explanatory diagram of the underwater image (received image) RI.

  In the example of the underwater image (received image) RI shown in FIG. 1, the first underwater object signal 3 and the second underwater object signal 4 that should be originally displayed are the vertical noise 1 and the horizontal noise 2 in the water. This is noise that is displayed even though no object is present.

  The noise generated here is referred to as “endogenous noise” because it is noise caused by the device itself in the cross fan beam type underwater image sonar.

  The vertical and horizontal cross-shaped noises 1 and 2 indicate the vibration between the electrostrictive vibrators of the X-direction receiving electrostrictive vibrator array and the Y-direction electrostrictive vibrator array shown in FIG. Occurs when it cannot be sufficiently shut off.

  In the case of a small cross fan beam type underwater image sonar, the arrangement interval of the electrostrictive vibrators is as short as 10 mm or less. For this reason, it is difficult to completely remove the leakage of vibration between the electrostrictive vibrators.

  In the cross fan beam type underwater image sonar, intrinsic noise that becomes a virtual image that does not exist may leak into the analog electrical signal (received image) RI input from the electrostrictive transducer array for reception. Therefore, it is a problem in the cross fan beam type underwater image sonar to realize a technique for removing the intrinsic noise.

  That is, when the cross fan beam type underwater image sonar disclosed in Patent Document 1 and Patent Document 2 is miniaturized, a plurality of electrostrictive transducers for transmission and a plurality of electrostrictive transducers for reception are linear. It is mounted with high density as an array. For this reason, it may be difficult to completely block vibration between the individual electrostrictive vibrators. When the received image from the underwater image sonar is displayed as it is (without any signal processing) on the display as a display image, a vertical or horizontal noise component (endogenous noise) may appear in the display image. This longitudinal noise and lateral noise (endogenous noise) are not natural underwater noise (exogenous noise). For this reason, there is a problem that it is very difficult to remove vertical noise and horizontal noise (endogenous noise) by signal processing.

  Therefore, when putting the cross-fan-beam underwater image sonar into practical use, a processing device that removes longitudinal noise and lateral noise (intrinsic noise) while leaving the reverberant sound reflected by the actual object in the water. Is required.

  On the other hand, the noise averaging process disclosed in Patent Document 3 and Patent Document 4 is merely a one-dimensional noise averaging process for removing the exogenous noise from the input frequency domain data. In other words, the type of noise (exogenous noise) targeted by Patent Document 3 and Patent Document 4 is completely different from the noise (endogenous noise) to be removed in the present invention.

  An object of the present invention is to provide an underwater image sonar noise reduction device, a noise reduction method, and a noise reduction program that solve the above-described problems.

  As one aspect of the present invention, a noise reduction device includes a cross-fan beam type underwater device in which a plurality of transmitting elements and a plurality of receiving elements intersect each other in a 90 ° relationship and are mounted as a linear array. A noise reduction device for processing a received image from an image sonar and outputting a display image for display on a display device, wherein the received image is composed of a plurality of pixels in a first direction and a second direction orthogonal to each other. And configured to connect vibrations between the plurality of transmitting elements, vibrations between the plurality of receiving elements, and the plurality of transmitting elements and the plurality of receiving elements and an electric circuit from the received image. Two-dimensional noise averaging processing means for removing the first direction noise and the second direction noise that are caused by at least one of the cases where electromagnetic induction noise leaks into the wiring to be output and outputting the display image Have

  As another aspect of the present invention, a noise reduction method includes a cross-fan beam type underwater device in which a plurality of transmitting elements and a plurality of receiving elements intersect each other in a 90 ° relationship and are mounted as a linear array. A noise reduction method for processing a received image from an image sonar and outputting a display image for display on a display device, wherein the received image is composed of a plurality of pixels in a first direction and a second direction orthogonal to each other. And configured to connect vibrations between the plurality of transmitting elements, vibrations between the plurality of receiving elements, and the plurality of transmitting elements and the plurality of receiving elements and an electric circuit from the received image. Two-dimensional noise averaging processing step for removing the first direction noise and the second direction noise, which are caused by at least one of the cases where electromagnetic induction noise leaks into the wiring to be connected, and outputting the display image including.

  As another aspect of the present invention, a noise reduction program includes a cross-fan beam type underwater device in which a plurality of transmitting elements and a plurality of receiving elements intersect each other in a 90 ° relationship and are implemented as a linear array. A noise reduction program for processing a received image from an image sonar by a computer and outputting a display image for display on a display device, wherein the received image includes a plurality of first and second directions orthogonal to each other. A plurality of transmitting elements, and a plurality of transmitting elements, and a plurality of receiving elements and an electric circuit. A two-dimensional noise that outputs the display image by removing the first direction noise and the second direction noise that are orthogonal to each other caused by at least one of electromagnetic induction noise leaking into the wiring connecting The averaging procedure, causes the computer to perform.

  According to the present invention, it is possible to remove only the first directional noise and the second directional noise that are orthogonal to each other and display only the signal of an object that actually exists in water.

It is a figure which shows the example of the underwater image (received image) received with the cross fan beam type underwater image sonar of related technology. It is a figure which shows the example of the square received image used for the signal processing of the underwater image sonar of a cross fan beam system in order to demonstrate the principle of this invention. It is a figure which shows the example of the display image obtained by removing noise from the received image shown in FIG. 1 by the signal processing by this invention. It is a block diagram which shows the structure of the sonar apparatus containing the noise reduction apparatus which concerns on the 1st Embodiment of this invention. 5 is a flowchart for explaining the operation of the noise reduction apparatus shown in FIG. 4. It is a block diagram which shows the structure of the sonar apparatus containing the noise reduction apparatus which concerns on the 2nd Embodiment of this invention. It is a flowchart for demonstrating operation | movement of the noise reduction apparatus shown in FIG.

[Principle of the Invention]
In order to facilitate understanding of the present invention, the principle of the present invention will be described first.

  In the present invention, noise averaging processing is added to signal processing for a received image obtained from a cross fan beam type underwater image sonar. By this noise averaging process, the vertical and horizontal noises peculiar to the cross fan beam type underwater image sonar are reduced, and only an underwater object is displayed. Here, the vertical direction is also referred to as a first direction, and the horizontal direction is also referred to as a second direction.

  Specifically, a square received image RI composed of pixels arranged in the X axis (horizontal direction) 5 and the Y axis (vertical direction) 6 shown in FIG. 2 will be described as an example.

  The received image shown in FIG. 2 has 121 pixels in the X-axis direction 5 and 121 pixels in the Y-axis direction 6, and is a received image RI that is composed of 121 squared 14,641 pixels as a whole.

  First, the noise reduction device calculates a vertical average value (AX (0 to 120)) of luminance values of pixels in the Y-axis direction 6 for each X-axis value as an analysis in the X-axis direction 5 of the received image RI. To do.

  Next, the noise reduction device calculates the average value (AX (0 to 120)) of the received image RI in the X-axis direction 5 and calculates the overall average value (AVE) of the brightness of the entire received image RI. .

  Next, the noise reduction device calculates the horizontal average value (AY (0 to 120)) of the luminance values of the pixels in the X-axis direction 5 for each Y-axis value as an analysis in the Y-axis direction 6 of the received image RI. To do.

  Next, in order to remove the vertical noise 1 in the Y-axis direction 6 from the received image RI, the noise reduction device divides the pixel (x, y) at an arbitrary coordinate by the vertical average value AX (x). Then, the ratio XSN (x, y) between the average value of the pixel (x, y) and the Y-axis direction 6 is calculated. As a result of this calculation, the average value of the Y-axis direction average value AX (x) of the pixel data having a high luminance of the pixels in the Y-axis direction 6 such as the longitudinal noise 1 in FIG. The value of (x, y) is close to 1.

  The noise reduction apparatus performs this calculation for all pixels, and removes the vertical noise 1 while leaving the first underwater object signal sound 3 and the second underwater object signal sound 4 of FIG.

  Next, in order to remove the lateral noise 2 in the X-axis direction 5 from the received image RI, the noise reduction device performs the lateral average for the luminance value XSN (x, y) of the pixel (x, y) at an arbitrary coordinate. Divide by the value AY (y). Then, a ratio YSN (x, y) between the average value of the pixel (x, y) and the X-axis direction 5 is calculated. As a result of this calculation, the average value of the average value AY (y) in the X-axis direction of the pixel data having a high luminance in the X-axis direction 5 such as the lateral noise 2 in FIG. The value of (x, y) is close to 1.

  The noise reduction apparatus performs this calculation for all the pixels, and removes the lateral noise 2 while leaving the first underwater object signal sound 3 and the second underwater object signal sound 4 of FIG.

  In this way, the noise reduction apparatus divides the luminance value of the pixel (x, y) at an arbitrary coordinate by the average value in the Y-axis direction (vertical direction) and then averages in the X-axis direction (horizontal direction). Divide by value. Thereby, as shown in FIGS. 3A and 3B, the noise reduction apparatus removes the vertical noise 1 and the horizontal noise 2, and the first underwater object signal 3 and the second underwater object signal 4. Can be displayed on the display.

  As described above, there is a usage example in the above-mentioned Patent Documents 3 and 4 for the noise averaging process.

  In the noise averaging process in Patent Documents 3 and 4, one-dimensional noise averaging process is performed on the input frequency domain data in passive sonar in order to remove external noise.

  On the other hand, in the noise averaging process in the present invention, two-dimensional noise averaging processes in the vertical and horizontal directions are performed on the input image data in order to remove intrinsic noise. As a result, the application range of noise averaging processing in active sonar is expanded.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. The configurations described in the following embodiments are merely examples, and the technical scope of the present invention is not limited thereto.

[Embodiment 1]
With reference to FIG. 4, the noise reduction apparatus 8 which concerns on the 1st Embodiment of this invention is demonstrated.

  The noise reduction device 8 is provided between the underwater image sonar 7 and the display 13.

  The underwater image sonar 7 is, for example, mounted as a linear array in which a plurality of transmitting elements and a plurality of receiving elements intersect with each other at a 90 ° relationship as disclosed in Patent Document 1 above. It consists of an underwater image sonar with a cross fan beam system. Each of the plurality of transmitting elements and the plurality of receiving elements is composed of an electrostrictive vibrator. The arrangement interval of the electrostrictive vibrators is 10 mm or less.

  The noise reduction device 8 processes the received image RI from the underwater image sonar 7 and outputs a display image for display on the display device 13. As shown in FIG. 2, the received image RI is composed of a plurality of pixels in a first direction (vertical direction) 6 and a second direction (horizontal direction) 5 that are orthogonal to each other.

  The noise reduction device 8 uses, from the received image RI, vibration between a plurality of transmitting elements, vibration between a plurality of receiving elements, and wiring that connects the plurality of transmitting elements, the plurality of receiving elements, and an electric circuit. The first direction noise (vertical noise) 1 and the second direction noise (lateral noise) 2 that are caused by at least one of the cases where electromagnetic induction noise leaks and are orthogonal to each other are removed, and the display image D1 2D noise average processing means (described later) for outputting (see FIG. 3).

  The noise reduction device 8 includes a vertical direction average value calculation processing unit 9, a horizontal direction average value calculation processing unit 10, a vertical direction noise average processing unit 11, and a horizontal direction noise average processing unit 12.

  The vertical direction average value calculation processing unit 9 is also called a first direction average value calculation unit. The vertical direction average value calculation processing unit 9 analyzes the received image RI in the second direction (X-axis direction) 5 as the first direction that is the luminance average value of the pixels in the first direction (Y-axis direction) 6. The average value (Y-axis direction average value) and the overall average value of the received image RI are obtained.

  The lateral direction average value calculation processing unit 10 is also called a second direction average value calculation unit. The horizontal direction average value calculation processing unit 10 analyzes the received image RI in the first direction (Y-axis direction) 6 as a second direction that is an average luminance value of pixels in the second direction (X-axis direction) X. An average value (X-axis direction average value) is obtained.

  The vertical noise average processing unit 11 is also referred to as a first direction noise average processing unit. The vertical noise average processing unit 11 divides the received image RI of the same second direction coordinate by the first direction average value (Y-axis direction average value) to obtain a first divided image, and this first division The image is multiplied by the overall average value, and an image from which the first direction noise (longitudinal noise) 1 has been removed is output.

  The lateral noise average processing unit 12 is also called a second direction noise average processing unit. The lateral noise average processing unit 12 divides the image of the same first direction coordinate from which the first direction noise has been removed by the second direction average value (X-axis direction average value) to obtain a second divided image. The display image from which the second direction noise (lateral noise) has been removed is output by multiplying the second divided image by the overall average value.

  Therefore, the combination of the vertical average value calculation processing unit 9, the horizontal direction average value calculation processing unit 10, the vertical noise average processing unit 11, and the horizontal noise average processing unit 12 is the above two-dimensional noise average processing means. Work as.

[Description of Operation of Embodiment 1]
Next, the operation of the noise reduction device 8 for active sonar will be described with reference to FIG.

  FIG. 5 is a flowchart showing an operation of removing the longitudinal noise 1 and the lateral noise 2 that are intrinsic noises from the image data (received image) RI output from the underwater image sonar 7.

  Since the operation of the underwater image sonar 7 has already been described in Patent Document 1 and Patent Document 2, description thereof will be omitted.

  The noise reduction device 8 inputs the received image RI, which is image data (x, y) composed of pixels shown in FIG. 2, for example, from the underwater image sonar 7 (step S101). When the input image data is displayed on the display unit 13 as it is, the received image RI includes a vertical noise 1, a horizontal noise 2, a first underwater object signal 3 and a second underwater object signal 4 as shown in FIG. Assume that the image data is included.

Subsequently, the vertical average value calculation processing unit 9 performs the luminance of the pixel in the vertical direction 1 for each X coordinate as a vertical average value calculation process on the received image RI which is the input image data (x, y). Is calculated (step S102). For example, when the received image RI is the image data shown in FIG. 2, there are 121 X-axis data from “0” to “120” in the X-axis direction 5. On the other hand, the vertical average value calculation processing unit 9 calculates the vertical average value AX (x) for each of 121 coordinates in the X-axis direction 5 by the following formula 1.

Further, the vertical average value calculation processing unit 9 calculates the overall average value AVE of the entire image data by the following formula 2.

Subsequently, the horizontal direction average value calculation processing unit 10 calculates the horizontal direction average value of the luminance of the horizontal pixel for each Y coordinate as the horizontal direction average value calculation processing for the input image data (x, y). Calculate (step S103). For example, when the received image RI is the image data shown in FIG. 2, there are 121 Y-axis data from “0” to “120” in the Y-axis direction 6. On the other hand, the horizontal direction average value calculation processing unit 10 calculates the horizontal direction average value AY (y) for each 121 coordinates in the Y-axis direction 6 by the following formula 3.

Subsequently, the vertical noise average processing unit 11 applies the same X coordinate image data (x, y) to the input image data (x, y) as the vertical noise average processing according to the following equation (4). The first divided image is obtained by dividing by the vertical average value AX (x), and the first divided image is multiplied by the overall average value (AVE) of the entire image data to obtain the image data XSN (x , y) is calculated (step S104). By this calculation, the image data XSN (x, y) becomes a value obtained by multiplying the ratio with the average value in the vertical direction by the average value of the entire image data, and the vertical noise 1 that increases the average value in the vertical direction is removed. Image.

Subsequently, the horizontal noise average processing unit 12 performs the same Y as the horizontal noise average processing on the image data (image from which the vertical noise 1 has been removed) XSN (x, y) by the following formula 5. The coordinate image data XSN (x, y) is divided by the lateral average value AY (y) to obtain a second divided image, and the entire average value (AVE) of the entire image data is further added to the second divided image. ) To calculate image data YSN (x, y) (step S105). By this calculation, the image data YSN (x, y) becomes a value obtained by multiplying the ratio with the average value in the horizontal direction by the average value of the entire image data, and the horizontal noise 2 that increases the average value in the horizontal direction is removed. Image (ie, display image) DI.

  Finally, the noise reduction device 8 has the image data YSN (x, y) from which the vertical noise 1 is removed by the vertical noise average processing unit 11 and the horizontal noise 2 is removed by the horizontal noise average processing unit 12. Is displayed on the display 13 (step S106).

  For example, even if the original image data (x, y) is image data (received image RI) including longitudinal noise 1 and lateral noise 2 as shown in FIG. 1, longitudinal noise 1 as shown in FIG. The image data YSN (x, y) (display image DI) from which the lateral noise 2 has been removed can be displayed on the display 13.

[Description of Effects of First Embodiment]
Next, the effect of the first embodiment will be described.

  The first embodiment of the present invention described above has the following effects.

  The first effect is that, in the display of the cross fan beam type underwater image sonar, the longitudinal noise and the lateral noise, which are intrinsic noises, are removed, and only the signal of an object that actually exists in the water can be displayed.

  The second effect is that, in the display of the cross fan beam type underwater image sonar, the luminance gradation level of the background is normalized by the average value of the entire screen, and can be displayed with a constant luminance gradation even if the underwater noise level changes. It is.

  Each unit of the noise reduction device 8 according to the first embodiment may be realized using a combination of hardware and software. In the form of a combination of hardware and software, for example, by operating hardware such as a control unit such as a CPU (central processing unit) based on a noise reduction program stored in a ROM (read only memory). Each part is realized as various means. Further, the noise reduction program may be recorded on a recording medium and distributed. The noise reduction program recorded on the recording medium is read into the memory via wired, wireless, or the recording medium itself, and operates the control unit and the like. Examples of the recording medium include a magnetic disk such as a hard disk, an optical disk such as a CD-ROM (compact disc read only memory) and a DVD (digital versatile disc), a magneto-optical disk (MO), and a semiconductor memory. Examples thereof include devices.

  If the first embodiment is described in another expression, a computer that operates as the noise reduction device 8 is based on a noise reduction program stored in the ROM, and a vertical average value calculation processing unit 9 and a horizontal average value calculation. This can be realized by operating as the processing unit 10, the vertical noise average processing unit 11, and the horizontal noise average processing unit 12.

[Embodiment 2]
With reference to FIG. 6, a noise reduction device 8A according to a second embodiment of the present invention will be described.

  The illustrated noise reduction device 8A is the same as the noise reduction device 8 shown in FIG. 4 except that processing operations in the vertical noise average processing unit and the horizontal noise average processing unit are different as will be described later. It has a structure and operates. Therefore, the reference signs 11A and 12A are assigned to the vertical noise average processing unit and the horizontal noise average processing unit, respectively.

  The noise reduction apparatus 8A according to the second embodiment not only removes the vertical noise 1 and the horizontal noise 2 by simple noise averaging processing, but also the first underwater object signal 3 and the second underwater object signal 4. A process for emphasizing a signal having a high luminance in the image data is added.

[Description of Operation of Embodiment 2]
Specifically, as shown in FIG. 7, the following processing is added in the vertical noise averaging process in step S <b> 104 and the horizontal noise averaging process in step S <b> 105 in FIG. 5.

First, the vertical noise average processing unit 11A performs vertical average processing on image data (x, y) having the same X coordinate according to the following equation as vertical noise average processing for the input image data (x, y). Dividing by the value AX (x), the first divided image XSN (x, y) is calculated (step S201). By this calculation, the image data XSN (x, y) becomes a ratio value with respect to the average value in the vertical direction, and becomes an image from which the vertical noise 1 that increases the average value in the vertical direction is removed.

Next, when the first divided image XSN (x, y) has a ratio exceeding a certain threshold (eg, 1.1) (“> threshold” in step S202), the vertical noise average processing unit 11A calculates the ratio. Signal emphasis processing is performed for emphasis, and the entire average value (AVE) of the entire screen is multiplied (step S203). As signal enhancement processing, a method of squaring a ratio XSN (x, y) as shown in the following equation 7 or a method of multiplying a predetermined coefficient K as shown in the following equation 8 can be considered.

Next, regardless of whether or not the first divided image XSN (x, y) exceeds or exceeds the threshold value, the vertical noise average processing unit 11A calculates the value of XSN (x, y) as shown in Equation 9 below. Is multiplied by the average value (AVE) of the entire screen, and XSN (x, y) is converted from a ratio to a luminance value (step S204).

The lateral noise average processing unit 12A performs image data XSN (x, y) of the same Y coordinate as the following equation 10 as the lateral noise average processing for the input image data (x, y). A second divided image YSN (x, y) is calculated by dividing by the horizontal average value AY (y) (step S205). By this calculation, the image data YSN (x, y) becomes a ratio value with respect to the average value in the horizontal direction, and an image from which the horizontal noise 2 that increases the average value in the horizontal direction is removed is obtained.

Next, when the second divided image YSN (x, y) has a ratio exceeding a certain threshold (eg, 1.1) (“> threshold” in step S206), the lateral noise average processing unit 12A calculates the ratio. Signal emphasis processing is performed for emphasis, and the average value (AVE) of the entire screen is multiplied (step S207). As signal enhancement processing, a method of squaring the ratio YSN (x, y) as shown in the following equation 11 or a method of multiplying the ratio by a predetermined coefficient K as shown in the following equation 12 can be considered.

Next, regardless of whether the second divided image YSN (x, y) exceeds or does not exceed the threshold value, the lateral noise average processing unit 12A calculates YSN (x, y) as shown in Equation 13 below. The value is multiplied by the average value (AVE) of the entire screen, and YSN (x, y) is converted from a ratio to a luminance value (step S208).

[Description of Effects of Second Embodiment]
Next, the effect of the second embodiment will be described.

  The second embodiment of the present invention described above has the following effects.

  The first effect is that, in the display of the cross fan beam type underwater image sonar, the longitudinal noise and the lateral noise, which are intrinsic noises, are removed, and only the signal of an object that actually exists in the water can be displayed.

  The second effect is that in the display of the cross fan beam type underwater image sonar, the luminance gradation level of the background is normalized by the average value of the entire screen, and the luminance of a part of the image is high even if the underwater noise level changes. The part can be highlighted.

  Each unit of the noise reduction device 8A according to the second embodiment may be realized using a combination of hardware and software. In the form of a combination of hardware and software, for example, by operating hardware such as a control unit such as a CPU (central processing unit) based on a noise reduction program stored in a ROM (read only memory). Each part is realized as various means. Further, the noise reduction program may be recorded on a recording medium and distributed. The noise reduction program recorded on the recording medium is read into the memory via wired, wireless, or the recording medium itself, and operates the control unit and the like. Examples of the recording medium include a magnetic disk such as a hard disk, an optical disk such as a CD-ROM (compact disc read only memory) and a DVD (digital versatile disc), a magneto-optical disk (MO), and a semiconductor memory. Examples thereof include devices.

  To describe the second embodiment in another expression, a computer that operates as the noise reduction device 8A is based on the noise reduction program stored in the ROM, and the vertical direction average value calculation processing unit 9 and the horizontal direction average value calculation. This can be realized by operating as the processing unit 10, the vertical noise average processing unit 11A, and the horizontal noise average processing unit 12A.

  Note that the present invention is not limited to the above-described embodiment as it is, and can be embodied by modifying the constituent elements without departing from the scope of the invention in the implementation stage. Various inventions can be formed by appropriately combining a plurality of components.

  For example, in the above embodiment, the case where each of the plurality of transmitting elements and the plurality of receiving elements is composed of an electrostrictive vibrator is described as an example. However, in the present invention, the vibrator is electrostrictive vibration. Not limited to children. That is, the present invention includes, in addition to the electrostrictive vibrator, vibration between a plurality of transmitting vibrators, vibration between a plurality of receiving vibrators, a plurality of transmitting elements, a plurality of receiving elements, and an electric circuit. The present invention is also applicable to the case where noise (intrinsic noise) is generated due to at least one of cases where electromagnetic induction noise leaks into the wiring connecting the two. Further, in the above embodiment, the case where the arrangement interval of the electrostrictive vibrators is 10 mm or less is described as an example. However, the present invention relates to leakage of vibration between vibrators, and a plurality of transmission elements and The present invention is applicable to an underwater image sonar having transducers with an arrangement interval that cannot completely eliminate leakage of electromagnetic induction noise in a wiring connecting a plurality of receiving elements and an electric circuit.

  While the present invention has been described with reference to the embodiment, the present invention is not limited to the above embodiment. Various changes that can be understood by those skilled in the art can be made to the configuration and details of the present invention within the scope of the present invention.

  A part or all of the above-described embodiment can be described as in the following supplementary notes, but is not limited thereto.

(Appendix 1)
A plurality of transmitting elements and a plurality of receiving elements intersect with each other at a 90 ° relationship and are mounted as a linear array, and process a received image from a cross fan beam type underwater image sonar, and display A noise reduction device that outputs a display image for display on the display, wherein the received image is composed of a plurality of pixels in a first direction and a second direction orthogonal to each other;
Electromagnetic induction from the received image to vibration between the plurality of transmitting elements, vibration between the plurality of receiving elements, and wiring connecting the plurality of transmitting elements and the plurality of receiving elements to an electric circuit Two-dimensional noise averaging processing means for outputting the display image by removing the first direction noise and the second direction noise, which are caused by at least one of the cases where noise leaks, which are orthogonal to each other,
Noise reduction device.

(Appendix 2)
The noise reduction device according to appendix 1, wherein each of the plurality of transmitting elements and the plurality of receiving elements is composed of an electrostrictive vibrator.

(Appendix 3)
The noise reduction device according to appendix 1 or 2, wherein an interval between the plurality of transmitting elements and the plurality of receiving elements is 10 mm or less.

(Appendix 4)
The two-dimensional noise average processing means includes
First direction average value calculating means for obtaining a first direction average value that is a luminance average value of pixels in the first direction and an overall average value of the received image as an analysis in the second direction with respect to the received image. When,
Second direction average value calculating means for obtaining a second direction average value, which is a luminance average value of pixels in the second direction, as the analysis in the first direction with respect to the received image;
The received image of the same second direction coordinate is divided by the first direction average value to obtain a first divided image, the first divided image is multiplied by the overall average value, and the first direction First direction noise averaging processing means for outputting an image from which noise has been removed;
The image of the same first direction coordinate from which the first direction noise is removed is divided by the second direction average value to obtain a second divided image, and the second divided image is multiplied by the overall average value. A second direction noise average processing means for outputting the display image from which the second direction noise has been removed;
The noise reduction device according to any one of appendices 1 to 3, comprising:

(Appendix 5)
The first directional noise averaging processing means applies an image obtained by performing signal enhancement processing to the first divided image when the first divided image has a ratio exceeding a predetermined threshold. Multiplying the overall average value to output an image from which the first direction noise has been removed,
The second direction noise average processing means is obtained by performing the signal enhancement processing on the second divided image when the second divided image has a ratio exceeding the predetermined threshold. Multiplying the image by the overall average and outputting the display image;
The noise reduction device according to appendix 4.

(Appendix 6)
The noise reduction device according to any one of appendices 1 to 5, and
The cross fan beam underwater image sonar;
The indicator;
A sonar device comprising:

(Appendix 7)
A plurality of transmitting elements and a plurality of receiving elements intersect with each other at a 90 ° relationship and are mounted as a linear array, and process a received image from a cross fan beam type underwater image sonar, and display A noise reduction method for outputting a display image for display on the display, wherein the received image is composed of a plurality of pixels in a first direction and a second direction orthogonal to each other,
Electromagnetic induction from the received image to vibration between the plurality of transmitting elements, vibration between the plurality of receiving elements, and wiring connecting the plurality of transmitting elements and the plurality of receiving elements to an electric circuit A two-dimensional noise averaging process step of outputting the display image by removing the first direction noise and the second direction noise, which are caused by at least one of cases where noise leaks, and which are orthogonal to each other;
Noise reduction method.

(Appendix 8)
The two-dimensional noise averaging processing step includes:
A first direction average value calculating step for obtaining a first direction average value that is a luminance average value of pixels in the first direction and an overall average value of the received image as an analysis in the second direction with respect to the received image. When,
A second direction average value calculating step for obtaining a second direction average value which is a luminance average value of pixels in the second direction as the analysis of the first direction with respect to the received image;
The received image of the same second direction coordinate is divided by the first direction average value to obtain a first divided image, the first divided image is multiplied by the overall average value, and the first direction A first direction noise averaging process step of outputting an image from which noise has been removed;
The image of the same first direction coordinate from which the first direction noise is removed is divided by the second direction average value to obtain a second divided image, and the second divided image is multiplied by the overall average value. A second direction noise averaging process step of outputting the display image from which the second direction noise has been removed;
The noise reduction method according to appendix 7, comprising:

(Appendix 9)
The first directional noise averaging processing step applies an image obtained by performing signal enhancement processing to the first divided image when the first divided image has a ratio exceeding a predetermined threshold. Multiplying the overall average value to output an image from which the first direction noise has been removed,
The second direction noise averaging processing step is obtained by performing the signal enhancement processing on the second divided image when the second divided image has a ratio exceeding the predetermined threshold. Multiplying the image by the overall average and outputting the display image;
The noise reduction method according to appendix 8.

(Appendix 10)
A plurality of transmitting elements and a plurality of receiving elements intersect each other in a 90 ° relationship and are mounted as a linear array, and the received image from the cross fan beam type underwater image sonar is processed by a computer, A noise reduction program for outputting a display image for display on a display device, wherein the received image is composed of a plurality of pixels in a first direction and a second direction orthogonal to each other,
Electromagnetic induction from the received image to vibration between the plurality of transmitting elements, vibration between the plurality of receiving elements, and wiring connecting the plurality of transmitting elements and the plurality of receiving elements to an electric circuit A two-dimensional noise averaging process for outputting the display image by removing the first direction noise and the second direction noise that are orthogonal to each other caused by at least one of the cases where noise leaks is provided to the computer. Noise reduction program to be executed.

(Appendix 11)
The two-dimensional noise averaging processing procedure is performed on the computer.
A first direction average value calculation procedure for obtaining a first direction average value, which is a luminance average value of pixels in the first direction, and an overall average value of the received image as an analysis in the second direction for the received image. When,
A second direction average value calculation procedure for obtaining a second direction average value that is a luminance average value of pixels in the second direction as the analysis in the first direction for the received image;
The received image of the same second direction coordinate is divided by the first direction average value to obtain a first divided image, the first divided image is multiplied by the overall average value, and the first direction A first directional noise averaging process for outputting a noise-removed image;
The image of the same first direction coordinate from which the first direction noise is removed is divided by the second direction average value to obtain a second divided image, and the second divided image is multiplied by the overall average value. A second direction noise averaging process for outputting the display image from which the second direction noise has been removed;
The noise reduction program according to appendix 10, wherein:

(Appendix 12)
In the first directional noise averaging processing procedure, when the first divided image has a ratio exceeding a predetermined threshold, the computer performs signal enhancement processing on the first divided image. The resulting image is multiplied by the overall average value to output an image from which the first direction noise has been removed,
In the second direction noise averaging processing procedure, when the second divided image has a ratio exceeding the predetermined threshold, the signal enhancement processing is performed on the second divided image. Multiplying the image obtained by applying the overall average value to output the display image;
The noise reduction program according to attachment 11.

DESCRIPTION OF SYMBOLS 1 Longitudinal noise 2 Lateral noise 3 1st underwater object signal 4 2nd underwater object signal 5 X-axis (horizontal direction)
6 Y-axis (vertical direction)
7 Underwater Image Sonar 8, 8A Noise Reduction Device 9 Vertical Average Value Calculation Processing Unit 10 Horizontal Direction Average Value Calculation Processing Unit 11, 11A Vertical Noise Average Processing Unit 12, 12A Horizontal Noise Average Processing Unit 13 Display RI Received Image DI display image

Claims (10)

A plurality of transmitting elements and a plurality of receiving elements intersect with each other at a 90 ° relationship and are mounted as a linear array, and process a received image from a cross fan beam type underwater image sonar, and display A noise reduction device that outputs a display image for display on the display, wherein the received image is composed of a plurality of pixels in a first direction and a second direction orthogonal to each other;
Electromagnetic induction from the received image to vibration between the plurality of transmitting elements, vibration between the plurality of receiving elements, and wiring connecting the plurality of transmitting elements and the plurality of receiving elements to an electric circuit Two-dimensional noise averaging processing means for outputting the display image by removing the first direction noise and the second direction noise, which are caused by at least one of the cases where noise leaks, which are orthogonal to each other,
Noise reduction device. The two-dimensional noise average processing means includes
First direction average value calculating means for obtaining a first direction average value that is a luminance average value of pixels in the first direction and an overall average value of the received image as an analysis in the second direction with respect to the received image. When,
Second direction average value calculating means for obtaining a second direction average value, which is a luminance average value of pixels in the second direction, as the analysis in the first direction with respect to the received image;
The received image of the same second direction coordinate is divided by the first direction average value to obtain a first divided image, the first divided image is multiplied by the overall average value, and the first direction First direction noise averaging processing means for outputting an image from which noise has been removed;
The image of the same first direction coordinate from which the first direction noise is removed is divided by the second direction average value to obtain a second divided image, and the second divided image is multiplied by the overall average value. A second direction noise average processing means for outputting the display image from which the second direction noise has been removed;
The noise reduction device according to claim 1, comprising: The first directional noise averaging processing means applies an image obtained by performing signal enhancement processing to the first divided image when the first divided image has a ratio exceeding a predetermined threshold. Multiplying the overall average value to output an image from which the first direction noise has been removed,
The second direction noise average processing means is obtained by performing the signal enhancement processing on the second divided image when the second divided image has a ratio exceeding the predetermined threshold. Multiplying the image by the overall average and outputting the display image;
The noise reduction device according to claim 2. The noise reduction device according to any one of claims 1 to 3,
The cross fan beam underwater image sonar;
The indicator;
A sonar device comprising: A plurality of transmitting elements and a plurality of receiving elements intersect with each other at a 90 ° relationship and are mounted as a linear array, and process a received image from a cross fan beam type underwater image sonar, and display A noise reduction method for outputting a display image for display on the display, wherein the received image is composed of a plurality of pixels in a first direction and a second direction orthogonal to each other,
Electromagnetic induction from the received image to vibration between the plurality of transmitting elements, vibration between the plurality of receiving elements, and wiring connecting the plurality of transmitting elements and the plurality of receiving elements to an electric circuit A two-dimensional noise averaging process step of outputting the display image by removing the first direction noise and the second direction noise, which are caused by at least one of cases where noise leaks, and which are orthogonal to each other;
Noise reduction method. The two-dimensional noise averaging processing step includes:
A first direction average value calculating step for obtaining a first direction average value that is a luminance average value of pixels in the first direction and an overall average value of the received image as an analysis in the second direction with respect to the received image. When,
A second direction average value calculating step for obtaining a second direction average value which is a luminance average value of pixels in the second direction as the analysis of the first direction with respect to the received image;
The received image of the same second direction coordinate is divided by the first direction average value to obtain a first divided image, the first divided image is multiplied by the overall average value, and the first direction A first direction noise averaging process step of outputting an image from which noise has been removed;
The image of the same first direction coordinate from which the first direction noise is removed is divided by the second direction average value to obtain a second divided image, and the second divided image is multiplied by the overall average value. A second direction noise averaging process step of outputting the display image from which the second direction noise has been removed;
The noise reduction method according to claim 5, comprising: The first directional noise averaging processing step applies an image obtained by performing signal enhancement processing to the first divided image when the first divided image has a ratio exceeding a predetermined threshold. Multiplying the overall average value to output an image from which the first direction noise has been removed,
The second direction noise averaging processing step is obtained by performing the signal enhancement processing on the second divided image when the second divided image has a ratio exceeding the predetermined threshold. Multiplying the image by the overall average and outputting the display image;
The noise reduction method according to claim 6. A plurality of transmitting elements and a plurality of receiving elements intersect each other in a 90 ° relationship and are mounted as a linear array, and the received image from the cross fan beam type underwater image sonar is processed by a computer, A noise reduction program for outputting a display image for display on a display device, wherein the received image is composed of a plurality of pixels in a first direction and a second direction orthogonal to each other,
Electromagnetic induction from the received image to vibration between the plurality of transmitting elements, vibration between the plurality of receiving elements, and wiring connecting the plurality of transmitting elements and the plurality of receiving elements to an electric circuit A two-dimensional noise averaging process for outputting the display image by removing the first direction noise and the second direction noise that are orthogonal to each other caused by at least one of the cases where noise leaks is provided to the computer. Noise reduction program to be executed. The two-dimensional noise averaging processing procedure is performed on the computer.
A first direction average value calculation procedure for obtaining a first direction average value, which is a luminance average value of pixels in the first direction, and an overall average value of the received image as an analysis in the second direction for the received image. When,
A second direction average value calculation procedure for obtaining a second direction average value that is a luminance average value of pixels in the second direction as the analysis in the first direction for the received image;
The received image of the same second direction coordinate is divided by the first direction average value to obtain a first divided image, the first divided image is multiplied by the overall average value, and the first direction A first directional noise averaging process for outputting a noise-removed image;
The image of the same first direction coordinate from which the first direction noise is removed is divided by the second direction average value to obtain a second divided image, and the second divided image is multiplied by the overall average value. A second direction noise averaging process for outputting the display image from which the second direction noise has been removed;
The noise reduction program according to claim 8, wherein: In the first directional noise averaging processing procedure, when the first divided image has a ratio exceeding a predetermined threshold, the computer performs signal enhancement processing on the first divided image. The resulting image is multiplied by the overall average value to output an image from which the first direction noise has been removed,
In the second direction noise averaging processing procedure, when the second divided image has a ratio exceeding the predetermined threshold, the signal enhancement processing is performed on the second divided image. Multiplying the image obtained by applying the overall average value to output the display image;
The noise reduction program according to claim 9.

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