JP6737464B2 - Test system, waveform simulator device, test method and program - Google Patents

Description

The present invention relates to a test system, a waveform simulator device, a test method and a program.

In recent years, underwater sonar uses a multi-channel piezoelectric oscillator array as a transducer to create a narrow directional beam, and steers the beam at any angle to search for a target in each direction. ..
Normally, an electric signal transmitted to a wave transmitter configured using a piezoelectric vibrator and an electric signal received from a wave receiver are subjected to filter, sampling rate conversion, bit depth conversion, signal processing, integration in a signal processor. Calculation, processed using four arithmetic operations. Here, the wave transmitter is a device that transmits a sound wave in water. A wave receiver is a device that receives sound waves in water.
Each signal processing block included in the signal processor has parameters for determining a processing operation. The optimum value of the parameter is to connect a transducer and a signal processor (hereinafter referred to as actual transducer) that are close to those used or actually used for implementation, arrange them in water, and generate an image. It is normal to tune the signal processing system while arranging a target suitable for the operation in water and checking an output screen (hereinafter referred to as a sonar screen) generated by performing an operation close to an actual one.

FIG. 13 is a conceptual diagram of an example of connections used in tuning a general signal processing system.

The signal processing system 1-1 is a system for generating a sonar image for the target object 1-9 existing in the water in the water tank 1-7. The water tank 1-7 is a water tank for forming an underwater sound field for transmitting and receiving waves. The water tank must have sufficient dimensions so that the pulsed sound waves transmitted from the wave transmitter will not be reflected by the wall of the water tank within the receiving time.
The signal processing system 1-1 shown in FIG. 13 includes a transmission signal generation unit 1-2, a transmission I/F 1-3, a reception I/F 1-4, a reception processing unit 1-5, and an image generation unit 1. -6 and. Further, the water tank 1-7 has a wave transmitter 1-8 and a wave receiver 1-10.
The transmission signal generation unit 1-2 generates a signal to be transmitted. The transmission signal generation unit 1-2 is a digital transmission waveform desired by a tuning operator by software operating on a processor such as a DSP (Digital Signal Processor), an FPGA (Field-Programmable Gate Array), and a CPU (Central Processing Unit). (Sine wave, chirp signal, etc.). The transmission waveform must be a pulse whose time width is set to be short so that it can be regarded as a free play space in which reflection can be sufficiently ignored in transmission and reception in water, which will be described later.
The transmission I/F 1-3 converts the digital signal waveform generated by the transmission signal generation unit 1-2 into an analog waveform and then amplifies the voltage/power. Specifically, the transmission I/F 1-3 converts the digital signal waveform generated by the transmission signal generation unit 1-2 into an analog waveform using a D/A (Digital/Analog) converter, and a power amplifier (amplifier). ) Is used to finally amplify to the voltage and power required by the transmitter and transmit it to the transmitter 1-8 via the plug, connector and cable.
The reception I/F 1-4 has an interface function for electrically receiving the reception signal acoustically converted by the wave receiver 1-10. The reception I/F 1-4 includes a plug, a connector, a cable, a low noise preamplifier, an A/D (Analog/Digital) converter, and the like. The reception I/F 1-4 finally outputs the reception signal as a digital signal to the reception processing unit 1-5 at the subsequent stage.
The reception processing unit 1-5 performs signal processing on the digital signal transmitted from the reception I/F 1-4. The signal processing performed by the reception processing unit 1-5 includes filter processing, sampling rate conversion, bit depth conversion, directivity synthesis, TS (Target strength) conversion, TVG (Time Varied Gain) correction, and the like. By this signal processing, the digital signal sent from the reception I/F 1-4 is converted into the pixel value of the image.
The image generator 1-6 displays a sonar image. An image to be displayed is generated based on the pixel value data generated by the reception processing unit 1-5.
The wave transmitter 1-8 radiates a transmission waveform as a sound wave to the target 1-9. The underwater transmitter is generally composed of a piezoelectric element in many cases.
The target object 1-9 is a target object (object) to be imaged by the sonar, and reflects the transmitted sound wave to the receiver. The target 1-9 is preferably tuned by preparing targets of various shapes from a simple shape to a complicated shape and from the largest dimension assumed in the specifications to the smallest dimension. In reality, the targets 1-9 that can be prepared are limited due to the size of the water tank 1-7 and the manual labor.
The wave receiver 1-10 receives the reflected sound wave from the target 1-9.
In the form shown in FIG. 13, it is assumed that the tuning is performed in an indoor water tank, but the tuning work may be performed at sea in order to perform the tuning under conditions closer to the actual usage environment. ..

FIG. 14 is a diagram showing an example of a frame in which the transmitter 1-8 and the receiver 1-10 shown in FIG. 13 are installed. Here, the case where the multi-narrow beam method is adopted as the beam method transmitted by the transmitter 1-8 will be described as an example.

The frame 2-1 shown in FIG. 14 has a cavity inside and can be designed to store an electronic circuit board. The frame 2-1 can also store a board whose ends are the transmission I/F 1-3 and the reception I/F 1-4 shown in FIG. 13, for example. The frame 2-1 is made of a metal such as duralumin, stainless steel, or titanium.
It is assumed that the wave transmitter 1-8 has a plurality of channels of piezoelectric elements arrayed in the longitudinal direction (left-right direction in FIG. 14). On the rear surface of the frame 2-1 on which the wave transmitter 1-8 is mounted, the wave is transmitted so that it can be connected to the transmission I/F1-3 via the transmission I/F1-3 and the cable shown in FIG. A container connector 2-4 is provided. The surface side of the frame 2-1 comes into contact with water in water, but this surface is molded with urethane or the like so that water does not enter the inside of the frame 2-1 and the wave transmitter 1-8. It is waterproof.
The wave receiver 1-10 has the same structure as the wave transmitter 1-8. The array direction of the wave receivers 1-10 is perpendicular to the wave transmitters 1-8 (vertical direction in the figure). In the example shown in FIG. 14, the wave transmitters 1-8 and the wave receivers 1-10 are Are arranged in an L shape. Further, on the rear surface of the frame 2-1 on which the wave receiver 1-10 is mounted, the reception I/F1-4 shown in FIG. 13 and the reception I/F1-4 can be connected via a cable or the like. A wave receiver connector 2-5 is provided.

FIG. 15 is a structural conceptual diagram of a vibrator commonly used for a wave transmitter and a wave receiver. The upper part of FIG. 15 is a cross-sectional view with the array direction as a normal line, and the lower part is an overall view in which 40 channels are arrayed. Here, as an example of the internal structure of the piezoelectric vibrator of the wave transmitter and the wave receiver, a case of a composite piezoelectric vibrator will be described as an example.
The mold 3-1 is a mold for maintaining the waterproofness of the entire wave transmitter/receiver, and a material such as urethane is used.
A composite oscillator is formed by alternately arranging the resin layers 3-2 and the piezoelectric ceramics 3-4. By using the composite vibrator, the acoustic impedance can be suppressed to be lower than that of a single piezoelectric ceramic. Therefore, such a structure is advantageous for acoustic impedance matching matching with water. In addition, it becomes easy to design a water pressure resistance when a large water pressure is applied in the sea. Further, in the example shown in FIG. 15, the piezoelectric ceramic is polarized in the vertical direction of the cross-sectional view and used as a vertical vibrator.
The matching layer 3-3 is a matching layer used for facilitating matching of acoustic impedance between the piezoelectric ceramics 3-4 and the mold 3-1. Generally, a hard resin material such as epoxy or polyimide is used for the matching layer 3-3. Here, the acoustic impedance of the piezoelectric ceramics 3-4 alone is
The degree of acoustic impedance of water
Therefore, when the piezoelectric ceramics 3-4 alone and the mold 3-1 are in direct contact with each other, the acoustic impedance at an intermediate level, that is, the acoustic impedance, is gradually reduced, that is,
It is necessary to interpose the matching layer 3-3 having a certain acoustic impedance with a wavelength of λ[m] at a predetermined frequency and a thickness of λ/4[m]. However, in the case of the composite type vibrator, since the acoustic impedance is a fraction of that of the piezoelectric ceramics 3-4 alone, the matching layer 3-3 may be unnecessary.
The backing first layer 3-5 and the backing second layer 3-6 are backing layers for preventing elastic waves from leaking to the back surface. By combining the low-impedance backing first layer 3-5 and the high-impedance backing second layer 3-6, multiple reflection occurs between the oscillator and the backing second layer 3-6, and the back surface is transmitted to the back surface. To prevent the escape of elastic waves.
The wire 3-7 and the connector 3-8 are for electrically connecting the piezoelectric ceramics 3-4.

Here, the multi-narrow beam method will be described.
The multi-narrow beam method scans a plurality of beams of transmitted and received waves in different directions (often orthogonal to each other) and forms a grid to determine whether or not a target is present at each point of the grid. This is a method of judging by the level of the reflected sound wave.
First, formation of a transmission/reception beam at a specific frequency will be described. Beam formation in free space is completely common to both transmitting and receiving. It is based on the reversibility of electroacoustic transformation and the fundamental solution of partial differential equations in free space (including elliptic partial differential equations such as Helmholtz equation describing a stationary sound field), that is, the mathematical reciprocity of the Green's function Guaranteed.

Now, normally, the drive voltage applied to the multi-channel array oscillator is applied by multiplying the weighting of the voltage to each channel in the vicinity of the resonance frequency of the oscillator. Examples of weighting functions include the Turkey window and the Chebyshev window.

FIG. 16 is a diagram illustrating an example of the relationship between the coordinates and the filter coefficient using the Chebyshev window. FIG. 16 shows the Chebyshev window (sidelobe attenuation ratio −60 dB) calculated using Equation 1 for 40 channels.
here,
Is. Formula 2 is the m-th order Chebyshev polynomial, and s is the attenuation ratio of the side lobe to the main lobe.

The voltage weighting characteristic 4-1 shown in FIG. 16 is an example of the Chebyshev window. Further, beam steering (moving the direction of the main lobe) is performed with respect to a desired steering angle θ, where the center distance d between the transducer channels, the sound velocity c, and the total number of transducer channels N are n channels. For the oscillator,
This can be achieved by giving a time delay of.

17(a) to 17(c) are diagrams showing the distribution of the vibration velocity amplitude and the vibration velocity phase when the transducer of 40 channels was vibrating uniformly. 17A to 17C show the absolute value and phase of the vibration velocity immediately above each channel vibrator of the outermost mold layer enclosing the vibrator, assuming that the vibration of the vibrator is uniform. .. FIG. 17A shows the distribution 5-1 of the vibration velocity amplitude and the vibration velocity phase when the beam steering is set to 0 deg. FIG. 17B shows the distribution 5-2 of the vibration velocity amplitude and the vibration velocity phase when the beam steering is set to 30 deg. FIG. 17C shows a distribution 5-3 of the vibration velocity amplitude and the vibration velocity phase when the beam steering is set to 60 deg.

18(a) to 17(c) are diagrams showing calculation results of the far field directivity of sound pressure produced by the velocity distributions shown in FIGS. 17(a) to 17(c). FIG. 18A shows a far-field directional characteristic 6-1 when the beam steering generated by the vibration velocity distribution shown in FIG. 17A is 0 deg. FIG. 18B shows a far-field directional characteristic 6-2 when the beam steering 30 deg produced by the vibration velocity distribution shown in FIG. 17B is used. FIG. 18C shows a far-field directional characteristic 6-3 when the beam steering 60 deg produced by the vibration velocity distribution shown in FIG. 17C is used.

As can be seen from the characteristics shown in FIGS. 17(a) to 17(c) and FIGS. 18(a) to 17(c), the beam formation of the transmitted/received waves and the beam steering are weighted (shading) of each transducer. And the delay time between each channel. If the beam steering is performed in 1 deg steps, the sound wave radiation direction surface can be decomposed in the steering direction by a distance grid corresponding to 1 deg. Therefore, if the wave transmitter and the wave receiver are arranged orthogonally to each other as shown in FIG. 14, the space in the sound wave radiation direction can be decomposed into an orthogonal lattice shape. The sound wave radiated from the wave transmitter is received as a strong reflected sound is returned only from the direction in which the target object is present. Therefore, the reaction as the target can be confirmed on the grid corresponding to the transmitting/receiving steering position of the target in the azimuth direction as viewed from the transmitter/receiver.

FIG. 19 is a diagram showing a scan conceptual diagram in the multi-narrow beam system.
As shown in FIG. 19, the beam steering direction is described as follows.
・Left → Right: Transmitted beam steering direction ・Up → Down: Received beam steering direction

In addition, the amplitude component of the reflected wave from the target object is evaluated by frequency analysis, or the signal component of the reflected wave from the target object is digitally calculated at a sampling rate sufficiently smaller than the carrier frequency. A pseudo signal generator that generates a pseudo signal in a carrier frequency band has been considered (for example, see Patent Documents 1 and 2).

JP, 04-254780, A Japanese Patent Laid-Open No. 05-215840

In the technique described above, in order to obtain an accurate sonar screen, optimization tuning using a large number of parameters is required. There is a problem that it takes a lot of time and cost to tune the signal processing system by constructing the measurement system each time using such a large number of parameters.

An object of the present invention is to provide a test system, a waveform simulator device, and a test method that solve the above problems.

The test system of the present invention is
Based on the transmission signal and the arrangement coordinates of the transmitter and the physical constants, a transmitted sound field simulator for calculating a transmitted sound field,
Based on the transmitted sound field calculated by the transmitted sound field simulator, the arrangement coordinates of the transmitter and the physical constants, a target object simulator for calculating the reflected sound field far field generated by the target object surface,
A receiver sound field simulator that calculates the receiver sound field by applying unit vibration speeds to multiple points on the receiver,
Reflected sound field far field calculated by the target simulator, based on the received sound field calculated by the received sound field simulator, a received sound pressure integrated calculation unit for calculating a directivity function to the target object,
A received sound wave time waveform conversion unit that calculates a time waveform of a received wave based on the directivity function calculated by the received sound pressure integrated calculation unit.
In addition, the waveform simulator device of the present invention,
Based on the transmission signal and the arrangement coordinates of the transmitter and the physical constants, a transmitted sound field simulator for calculating a transmitted sound field,
Based on the transmitted sound field calculated by the transmitted sound field simulator, the arrangement coordinates of the transmitter and the physical constants, a target object simulator for calculating the reflected sound field far field generated by the target object surface,
A receiver sound field simulator that calculates the receiver sound field by applying unit vibration speeds to multiple points on the receiver,
Reflected sound field far field calculated by the target simulator, based on the received sound field calculated by the received sound field simulator, a received sound pressure integrated calculation unit for calculating a directivity function to the target object,
A received sound wave time waveform conversion unit that calculates a time waveform of a received wave based on the directivity function calculated by the received sound pressure integrated calculation unit.
Further, the test method of the present invention,
Based on the transmission signal and the arrangement coordinates of the transmitter and the physical constants, the process of calculating the transmitted sound field,
Based on the transmitted sound field, the arrangement coordinates of the transmitter and the physical constants, a process of calculating a reflected sound field far field produced by the target surface,
A process of calculating a received sound field by giving unit vibration speeds to a plurality of points of a receiver,
Based on the reflected sound field far field and the received sound field, a process of calculating a directivity function to the target object,
A process of calculating the time waveform of the received wave is performed based on the calculated directivity function.
Further, the program of the present invention is
A program for causing a computer to execute,
Based on the transmission signal, the arrangement coordinates of the transmitter and the physical constants, a procedure for calculating the transmitted sound field,
Based on the transmitted sound field and the arrangement coordinates of the transmitter and the physical constants, a procedure for calculating a reflected sound field far field produced by the target surface,
A procedure for calculating the received sound field by applying unit vibration speeds to multiple points on the receiver,
Based on the reflected sound field far field and the received sound field, a step of calculating a directivity function to the target,
And a procedure of calculating a time waveform of the received wave based on the calculated directivity function.

As described above, in the present invention, a highly accurate sonar screen can be easily obtained.

It is a figure which shows 1st Embodiment of the test system of this invention. It is a figure which shows the outline|summary of arrangement|positioning of the wave transmitter, the target object, the seabed, and the wave receiver which the wave reception waveform simulator system shown in FIG. 1 simulates. It is a figure which shows an example of the vibration speed given to a wave-transmitter surface. In the multi-narrow beam system, it is a diagram showing the correspondence between the vibration velocity applied to the wave transmitter surface and the sonar image. It is a figure which shows the wave transmission (wave reception) surface in an xyz coordinate system. It is a figure which shows the reference image data which the reference image production|generation part shown in FIG. 1 produced, and an example of the area which detected the target object. It is a figure which shows an example of a mode of the target object which exists in a coordinate system. It is a figure which shows an example of a sonar screen when the attenuation ratio of the side lobe with respect to the main lobe is 90 dB. It is a figure which shows an example of a sonar screen when the attenuation ratio of the side lobe with respect to the main lobe is 60 dB. It is a figure which shows an example of a sonar screen when the attenuation ratio of the side lobe with respect to the main lobe is set to 30 dB. Image S / N ratio calculating evaluation unit shown in FIG. 1, using the equation 29 to equation 34 is a graph showing the results of calculating the SN _avr and SN _max. It is a figure which shows the 1st modification of the test system of this invention. It is a figure which shows the 2nd Embodiment of the test system of this invention. 12 is a flowchart for explaining an example of a test method in the test system shown in FIG. 11. It is a conceptual diagram of an example of the connection used in the tuning of a general signal processing system. FIG. 14 is a diagram showing an example of a frame in which the transmitter and the receiver shown in FIG. 13 are installed. It is a structure conceptual diagram of the vibrator commonly used for a wave transmitter and a wave receiver. It is a figure which shows an example of the relationship between the coordinate using a Chebyshev window, and a filter coefficient. It is a figure which shows distribution of a vibration velocity amplitude and a vibration velocity phase when beam steering is set to 0 deg. It is a figure showing distribution of vibration velocity amplitude and vibration velocity phase when beam steering is set to 30 deg. It is a figure showing distribution of vibration velocity amplitude and vibration velocity phase when beam steering is set to 60 deg. FIG. 18 is a diagram showing a far-field directional characteristic when the beam steering generated by the vibration velocity distribution shown in FIG. 17A is 0 deg. FIG. 18 is a diagram showing a far-field directional characteristic when the beam steering 30 deg produced by the vibration velocity distribution shown in FIG. 17B is used. FIG. 18 is a diagram showing a far-field directional characteristic when the beam steering 60 deg produced by the vibration velocity distribution shown in FIG. 17C is used. It is a scanning conceptual diagram in a multi-narrow beam system.

INDUSTRIAL APPLICABILITY The present invention makes it possible to easily perform parameter tuning and debugging of a signal processor for generating various images in acoustic tomography in underwater exploration and underwater sonar without an actual transducer. We propose a sonar signal processing tester.

Embodiments of the present invention will be described with reference to the drawings.
(First embodiment)

FIG. 1 is a diagram showing a first embodiment of a test system of the present invention. As shown in FIG. 1, this embodiment has a signal processing system 8-1, a received wave simulator system 8-7, and an image evaluation system 8-15.

As shown in FIG. 1, the signal processing system 8-1 includes a transmission signal generation unit 8-2, a transmission I/F 8-3, a reception I/F 8-4, a reception processing unit 8-5, and an image generation. Parts 8-6.
The transmission signal generator 8-2 generates a signal to be transmitted. The transmission signal generation unit 8-2 generates a desired digital transmission waveform (sine wave, chirp signal, etc.) desired by the tuning operator by software running on a processor such as DSP, FPGA, CPU. The transmission waveform must be a pulse whose time width is set to be short so that it can be regarded as a free-floating space in which reflection can be sufficiently ignored during transmission and reception in water.
The transmission I/F 8-3 converts the digital signal waveform generated by the transmission signal generation unit 8-2 into an analog waveform and then amplifies the voltage/power. Specifically, the transmission I/F 8-3 converts the digital signal waveform generated by the transmission signal generation unit 8-2 into an analog waveform using a D/A converter, and uses a power amplifier (amplifier), Finally, the voltage and power required by the transmitter are amplified and transmitted to the receiving waveform simulator system 8-7 which simulates the transmitter.
The reception I/F 8-4 has an interface function for electrically receiving a signal which is the received sound pressure time waveform transmitted from the received waveform simulator system 8-7. The reception I/F 8-4 includes a plug, a connector, a cable, a low noise preamplifier, an A/D converter and the like. The reception I/F 8-4 finally outputs the reception signal as a digital signal to the reception processing unit 8-5 in the subsequent stage.
The reception processing unit 8-5 performs signal processing on the digital signal sent from the reception I/F 8-4. The signal processing performed by the reception processing unit 8-5 includes filter processing, sampling rate conversion, bit depth conversion, directivity synthesis, TS conversion, TVG correction, and the like. By this signal processing, the digital signal transmitted from the reception I/F 8-4 is converted into the pixel value of the image.
The image generation unit 8-6 transmits the sonar image to the image evaluation system 8-15. At this time, the image generation unit 8-6 generates an image to be displayed based on the pixel value data generated by the reception processing unit 8-5 and transmits it to the image evaluation system 8-15.

The received waveform simulator system 8-7 is one in which the inside of the water tank 1-7 shown in FIG. 13 is replaced with a simulator for optimization tuning. The wave reception waveform simulator system 8-7 uses predetermined physical constants, a wave transmitter, a wave receiver, and coordinate information of a target object based on the transmission signal of each channel transmitted from the signal processing system 8-1. , Generate a reception waveform to be input to the reception I/F 8-4. As shown in FIG. 1, the received wave simulator system 8-7 includes a transmitted sound field simulator 8-8, a target object simulator 8-9, a received sound field simulator 8-10, and a received sound pressure integrated calculator 8-. 11, a received sound wave time waveform converter 8-13, and a reference image generator 8-14. The received waveform simulator system 8-7 may be one device (waveform simulator device) including these components.
Here, the transmitted sound field simulator 8-8, the target object simulator 8-9, the received sound field simulator 8-10, and the received sound pressure integrated calculation unit 8-11 configure a Fourier domain simulator 8-12. .. The Fourier domain simulator 8-12 sequentially calculates a single frequency component within a predetermined calculation band, and finally calculates a frequency component within the band. The received sound wave time waveform conversion unit 8-13 converts the calculation result regarding all frequency components in the band output from the received sound pressure integrated calculation unit 8-11 into a time waveform after considering the causality of the inverse Fourier transform. To do. Further, in all calculations inside the received wave simulator system 8-7, it is assumed that the target is sufficiently far from the transmitter/receiver in comparison with the wavelength (more than twice the Rayleigh distance). Boundary calculation is performed. Even in actual sonar, it is mostly used at a distance that can be regarded as a far field. Therefore, such assumptions and approximations are possible. Each component of the received wave simulator system 8-7 can be constructed by software on a processor such as one CPU, DSP, FPGA or the like, or each can be constructed by different processors. It is also possible to do so. The Fourier domain simulator 8-12 divides it into a single Fourier component and performs calculation on all Fourier components within a predetermined band. This Fourier domain simulator performs loop or parallel calculation in the Fourier transform domain so as to calculate the received sound pressure of each channel of the receiver for each beam steering angle of the transmitted wave.
The transmitted sound field simulator 8-8 calculates the far field of the transmitted sound field based on the transmission signal transmitted from the transmission I/F 8-3, the arrangement coordinate information of the transmitter, and the physical constants such as the underwater sound velocity. To do.
The target object simulator 8-9 is a distant reflected sound field created by the surface of the target object based on the transmitted sound field calculated by the transmitted sound field simulator 8-8, the arrangement coordinate information of the transmitter and the physical constants such as the underwater sound velocity. Calculate the world.
The received sound field simulator 8-10 calculates the received sound field created by the receiver on the target object. The receiving sound field simulator 8-10 calculates the sound field by giving a unit vibration velocity to each point or each channel of the receiver, and calculates the sound field using the reciprocity of the Green's function. The received sound field is obtained by interpreting it as a function.
The received sound pressure integrated calculation unit 8-11 inputs the calculation result of the target object simulator 8-9 and the calculation result of the received sound field simulator 8-10, and integrates the sound pressure received by each channel of the receiver. calculate. The received sound pressure integrated calculation unit 8-11 collects and arranges the sound pressure calculation results received by the respective channels of the receiver for the frequency components within the entire band. As an actual calculation, the received sound pressure integrated calculator 8-11 performs a huge matrix calculation.
The received sound wave time waveform converter 8-13 calculates the time waveform of the received sound wave using inverse Fourier transform based on the data sent from the Fourier domain simulator 8-12.
The reference image generation unit 8-14 generates reference image data generated only by the data inside the received wave simulator system 8-7.

The image evaluation system 8-15 evaluates the quality of the image data generated by the signal processing system 8-1 based on the time waveform generated by the received wave simulator system 8-7. The image evaluation system 8-15 is a system that determines the quality of an image when various parameter settings are changed with reference to a certain parameter setting (transceiver shading window coefficient or the like). The image evaluation system 8-15 has an image S/N ratio calculation evaluation unit 8-16.
The image S/N ratio calculation/evaluation unit 8-16 is an image S/N ratio calculation/evaluator, and includes the standard image data generated by the reference image generation unit 8-14 and the signal processing system 8- which is the evaluation target. 1 is compared with the image data generated, and the S/N ratio of the image is calculated and evaluated based on the definition described later.

FIG. 2 is a diagram showing an outline of the arrangement of the wave transmitter, the target object, the sea bottom, and the wave receiver simulated by the wave reception waveform simulator system 8-7 shown in FIG.

The wave transmitter surface 9-1 outputs an incident sound. In the following description, the suffix of the point on the transmitter surface 9-1 is represented by j.
The target 9-2 is a target to be searched. In FIG. 2, it is shown as a suitable ellipsoid. The suffixes on the target 9-2 and the sea bottom 9-4 are represented by i.
The hidden surface 9-3 of the sea bottom by the target is the hidden surface of the target 9-2 to the sea bottom 9-4. In addition to this, there is also a hidden surface that makes a point on the target 9-2 at another point, but it is omitted in FIG. The hidden surface will be briefly described in the item of the target object simulator described later.
The wave receiver surface 9-5 receives the reflected sound reflected from the target object 9-2. The suffix of the point on the receiver surface 9-5 is represented by k. The wave transmitter surface 9-1 and the wave receiver surface 9-5 may be on the same plane or on different planes.

The detailed operation of each simulator (or calculation unit) in the received waveform simulator system 8-7 shown in FIG. 1 will be described below. Note that the mathematical expressions used in the following description are explained using analytical expressions (integral symbols, etc.) for continuous functions, but in implementation work such as software coding in an actual system, replacement is necessary in consideration of discrete processing. Becomes

FIG. 3 is a diagram showing an example of the vibration velocity applied to the wave transmitter surface.
In FIG. 3, assuming that the wave transmitter 1-8 shown in FIG. 14 is used as a wave transmitter, a grid mesh of 80×2 or more is prepared, and the vibration velocity is given only to 40×1 channel of the grid mesh. To do. The filled part is an image of the part given the vibration velocity distribution. It is set to generate a mesh grid by dividing one channel into 2×2 grids or more. The Chebyshev window shown in FIG. 16 is assumed for the vibration velocity distribution to be set.

FIG. 4 is a diagram showing a correspondence between a vibration velocity applied to a wave transmitter surface and a sonar image in the multi-narrow beam method. When one column in the vertical direction is assigned to the transmitting beam steering direction, one Fourier component on the sonar image corresponds to one transmitter vibration velocity distribution. The decomposition of the received beam steering direction assigned in the lateral direction into each angle is performed by directivity synthesis in the reception processing of the signal processing system 8-1.

As shown in FIG. 3, the calculation method of the far-field directivity function of the sound pressure when the vibration velocity distribution S _j exists in the plane area Λ is shown below. First, consider the velocity potential created by all points ∪ΛS _j on the sound source plane at the target and the point P _i on the sea bottom 9-4 in FIG.
In Equation 5, r _ij is the point S _i on the sound source plane, target and distance of a point P _i on the seabed, ds is small area of the points S _i on the sound source plane, v _i is the particle velocity to be set Yes, Λ is the entire area of the sound source plane. As will be described later, the actual calculation is performed by the far-field calculation by the two-dimensional Fourier transform, and the formula 5 is not used for the calculation. By the two-dimensional Fourier transform, the integral calculation of Expression 5 is executed including the coordinate conversion from the rectangular coordinate system to the spherical coordinate system, which is efficient in executing the numerical calculation. From the basic theory of linear acoustics, the velocity potential that a particle velocity distribution on a certain plane generally creates at an arbitrary point that is sufficiently distant from the sound source plane is expressed by the following equation with coordinate transformation from a rectangular coordinate system to a spherical coordinate system. 6 is calculated by a two-dimensional Fourier transform.
Here, v _i is the particle velocity at a point on the plane sound source, r ₀ is the distance from the center of the sound source plane to the observation point, Cartesian coordinates on the xy plane sound source, k is the wave number, and θ and φ are respectively shown in FIG. It is the angle formed by the normal vector of the indicated sound source plane and the xy axes. V(·,·) is the two-dimensional Fourier transform of the sound source distribution of the plane sound source. In numerical calculation, the important point is that the far-field directivity is a factor indicating distance attenuation in Equation 5.
And the directional function
It means that it can be factored into and calculated. Since both can be calculated independently, the calculation amount of far calculation can be saved. This is important in the calculation processing in the present invention described later. This is a directional function
This is because a high-speed calculation by a two-dimensional FFT (Fast Fourier Transform) can substitute the enormous Equation 4 in which each sound field created at a certain observation point is obtained by integral calculation. ..
By the above calculation, the sound field created by the transmitter is calculated at an arbitrary point.

The target simulator 8-9 creates the mesh grid of the target and the sea bottom shown in FIG. When creating the mesh grid of the target, list the hidden surfaces that the target makes on the sea floor and the hidden surfaces created by the points on other targets in advance, from each point of the transducer, It needs to be removed from the reflected wave calculation described below. Here, like the normal image processing, the hidden surface can be calculated by using perspective projection calculation using homogeneous coordinates (four-dimensional space coordinates), and thus detailed processing thereof will not be described here.
Subsequently, the target simulator 8-9 calculates the velocity potential of the incident wave on the target and the sea bottom by performing fitting approximation to each point of the mesh grid on the target and the sea bottom. The target object simulator 8-9 calculates the velocity potential of the reflected wave by multiplying the velocity potential of the incident wave by the reflection coefficient.
The velocity potential of the reflected wave on the target and the surface of the sea bottom can be calculated using the incident angle with respect to the reflecting surface and the acoustic impedance between the incident medium and the reflecting object. In the following, points on the target object are described by adding "1" to the subscript as in (i ₁ ) and by adding "2" in the subscript as at (i ₂ ) for points on the sea floor. It will be explained as what is done. Suffixes and parentheses are used only for legibility, and there is no difference in meaning from subscript suffixes.
The position vector of each point (node) of the target is set with the center point of the sound source plane as the origin.
And the normal vector to the tangent plane calculated at each target point is
And the sound velocity and acoustic impedance in water are c ₁ and Z ₁ (c ₁ =1500 m/s, Z ₁ =1.5×10 ⁶ Pa·s/m), and the sound velocity and acoustic impedance in the target object are c ₂ , Z ₂ (c ₂ =6000 m/s, Z ₁ =46.4×10 ⁶ Pa·s/m) and the reflection phase constant (constant) determined by the target object is γ _trg , The conditions for the incident angle of the sound wave and the hidden surface are as follows.
Further, the velocity potential reflectance of the target object is calculated using the following equation 8 of the incident angle to the target object. Further, the reflection coefficient τ _trg (i) of the velocity potential at each point of the target object and the sea bottom is calculated by using Expression 9 by multiplying the area ΔS(i) assigned at the reflection point.

The receiving sound field simulator 8-10 uses the two-dimensional Fourier transform to actually calculate the velocity potentials created by all the points ∪ΓP _i on the target and the sea bottom at the points R _k on the receiving surface. Execute. However, the long-distance sound field calculation by the two-dimensional Fourier transform can calculate only the sound field created by the sound source arranged on the plane. Therefore, the received sound field simulator 8-10 utilizes the reciprocity of the Green's function. The receiving sound field simulator 8-10 gives a delta function of Dirac analytically to the area η corresponding to each channel of the sound receiving surface, and gives a unit velocity for each channel in the actual numerical processing, and Calculate the propagator (Green's function) to the point P _i . Then, the received sound field simulator 8-10 uses the reciprocity of the Green's function to obtain the Green's function from each point P _i to the point R _k on the sound receiving surface.
That is, the Green's function for the point k on the region η corresponding to a certain channel is
Can be calculated as However, δ(kεη) represents a Dirac delta function whose value is 0 outside the region η, and Γ represents the entire region of the sound receiving surface.

The received sound pressure integrated calculation unit 8-11 calculates the Green's function G(k,i) calculated using Expression 10 and the reflection coefficient τ _trg (i) at P _i calculated using Expression 9 and Expression 5 By multiplying the velocity potential Φ _i calculated using, the velocity potential Ψ _k created at the point k on each channel of the sound receiving surface is given by
And calculate. However, Ω is the entire area of the target and the sea bottom. The two-dimensional Fourier transform is applied only to the expression 10, and cannot be applied to the expression 5, and the following integral calculations (1) to (3) are executed as they are.
FIG. 5 is a diagram showing a transmitting (receiving) surface in the xyz coordinate system. FIG. 5 shows the wave transmission (reception) surface 12-1 and the angles φ and θ of the coordinate system 12-2.
(1) A Dirac delta function, that is, a numerical value of 1 discretely is given to each region corresponding to one channel having a sound receiving surface, and a Green function to the target and the sea bottom is calculated. Specifically, by fitting a polynomial that can calculate the Green's function for any distant point, the coefficient information matrices Kφ and Kθ for the angles φ and θ shown in FIG. 5 are obtained. The matrix K is a (fitting order)×(number of channels) matrix.
(2) From the Green's functions (matrix Kφ and Kθ) obtained in (1) above and the distance-dependent factors in Equation 6, the directivity function to all points ∪ΓP _i on the target and the seabed is calculated and reflected. It is multiplied by the velocity potential.
(3) All the velocity potentials calculated in (2) above are added together to be converted into sound pressure, and the sound pressure is received by the sound receiving channel.
Hereinafter, the above (1) to (3) will be described using mathematical expressions. Regarding the fitting coefficient information of the Green's function, assuming that the fitting order is n−1 and the number of channels is k, the matrices Kφ and Kθ are as follows.
Here, if the polar coordinates are (φ(j), θ(j), r(j)), the factors depending on the angles φ and θ of the velocity potential on the sound receiving channel and the distance are as follows. ..
Therefore, η is the propagation loss in the water, and a vector summarizing velocity potentials for k channels calculated on a certain node on the target.
To
Then, a vector summarizing the l-th Fourier component of the velocity potential for k channels received by each receiver channel.
Is
Can be calculated. The upper left subscript t represents the transpose of the matrix.

In the received sound wave time waveform conversion unit 8-13, if the velocity potential created for each channel is calculated for each of the Fourier components in the calculated band using Equation 18 below, the time is calculated by the inverse Fourier transform. The response is calculated. That is, assuming that the sound source surface is fixed on a plane, the two-dimensional coordinates
The vibration velocity of the point represented by
Is the vibration velocity distribution
An array in which each is further arranged corresponding to the angular frequency ω
Becomes That is, assuming that the number of two-dimensional grids m×n on the sound source surface is the number of elements of ω,
Becomes Therefore, in order to calculate the time response for the arbitrary waveform, the calculation procedure is as in the following (1) to (3).
(1) Regarding the matrix for the angular frequency of Expression 19 shown below, according to Expressions 11 to 18, the received sound pressure integrated calculation unit 8-11 or the received sound wave time waveform conversion unit 8-13 is used for each receiving surface of the sound receiving surface. Calculate the sound pressure received by a sound channel. In the discrete calculation, it is not necessary to calculate the entire Nyquist frequency band, but the velocity potentials of the sound receiving channels are calculated only for the frequency band that gives the signal, and the velocity potentials of all the channels are calculated outside the signal band. Should be 0.
(2) The result of (1) above is inverse Fourier transformed to calculate the time response.
(3) In the time response calculated in (2) above, the non-causal part (left half) response is deleted and only the right half is adopted as the actual received sound pressure waveform.
In the following, the suffix is defined as follows. This definition differs from the one described above. Time sequence
Is defined as
Defined as the number of transmission pings
It is defined as. As a result of the calculation in (1) above, the result of summarizing the responses in the Fourier transform domain received by each sound receiving channel.
Is the result of arranging Equation 17 in the frequency sequence as follows. Of Equation 17
Is a vector in which the sound pressures of the sound receiving channels for the l-th Fourier component are arranged, so the result of summarizing all frequency responses
Is a matrix consisting of channel k and the number of frequency vector elements l.
Assuming a plane wave because it is distant, the velocity potential of Expression 19 is converted into sound pressure as follows using a Hadamard product of a matrix in which column vectors of each frequency vector are arranged in the row direction by the number of channels k. ..
Here, ρ is the mass density of water, and c is the speed of sound in water.
Sound pressure waveform in the time domain
Is the k-th column vector of Equation 20. The received sound wave time waveform converter 8-13
Should be taken out and converted into a time domain signal by the inverse Fourier transform (in the case of discrete signal calculation, the integration section has positive and negative Nyquist frequencies).
One element in this
Is the same number of elements l as the vector for the time sequence. here,
Is calculated as a bilaterally symmetric linear-phase impulse response depending on the calculation method using Expression 21. This is a result of imposing causality by time-shifting the impulse response which is symmetrical with respect to the axis at time 0 and symmetrical in positive and negative times. However, the actual received wave of the sonar is only the right half, that is, the waveform of the portion where there is no reflection response before time 0, so the left half must be discarded.
Calculated in this way
Is the wave-received sound pressure waveform of the k-th receiver of one transmission ping.

By performing the above calculation for all the transmission pings, the data ξ finally output from the received sound wave time waveform conversion unit 8-13 is calculated. ξ is a three-dimensional array composed of three suffixes of the time sequence 1, the number of receiving channels k, and the number of transmission pings n, as described below.
Digital data calculated using Equation 22
Is D/A converted and sent to the signal processing system 8-1 to be inspected as the output of the received wave simulator system 8-7.

The reference image generation unit 8-14
A standard sonar image can be generated by performing a standard directivity combining process on the data of 1 ping. The calculation for generating a standard sonar image performed by the standard image generation unit 8-14 will be described below.
Of the two-dimensional array of transmission ping numbers n
If you write down again in the form of a matrix,
Becomes
Fourier transformed for each channel, that is, for each column,
Then,
Becomes Next,
The angles of the th beam steering are combined into a column vector and the following is defined.
Here, from Equation 24 and Equation 25, the sonar image pixel value of the nth transmitted beam steering (ping) and the mth received beam steering becomes a scalar value,
Becomes The reference sonar image is generated by arranging and imaging all the sonar image pixel values κ _mn .
The signal processing system 8-1 to be optimized also generates sonar image data using a method similar to the above. However, the signal processing system 8-1 also needs to perform a rapid process on-line for data streaming sent from an actual transceiver. In addition, the signal processing system 8-1 performs a calculation method while executing decimation of data sampling, bit rate conversion, and numerical precision conversion (double precision to single precision, etc.) due to restrictions such as the size and heat generation amount of the device itself. Also needs to be simplified. Therefore, the quality of data deteriorates. Therefore, the reference image data
Is preferably generated within the received waveform simulator system 8-7.

The image evaluation system 8-15 has an image S/N ratio calculation evaluation unit 8-16. The image S/N ratio calculation/evaluation unit 8-16 uses the reference image data.
Is used as a reference, the actual data actually processed by the signal processing system 8-1 and transmitted to the image S/N ratio calculation/evaluation unit 8-16 is evaluated in the form of S/N ratio. Image data processed by the signal processing system 8-1
Then,
When,
And are matrices or arrays of the same size. The calculation method and procedure of the S/N ratio are performed as described in (1) and (2) below.
(1) Definition of target existence area: In defining the S/N ratio, first, the area where the target exists on the image data.
And a nonexistent area
And
It is necessary to calculate from.

FIG. 6 is a diagram showing an example of the reference image data generated by the reference image generation unit 8-14 shown in FIG. 1 and an area in which the object is detected. Reference image data shown in FIG.
In the area where the target object exists, the level of the reflected wave becomes large as shown by the bright part of the reference image data 13-1 in FIG. Therefore, the target existence determination matrix
Is provided, and 1 is assigned to the level equal to or higher than the predetermined threshold T level, and 0 is assigned to the level less than the predetermined threshold T level, whereby the target object existing area and the non-existing area can be clearly indicated. That is,
Therefore, the determination result from the equation 28 is the reference image target object detection area 13-2 shown in FIG. The bright part indicates the area where the target exists.
(2) Image data calculated under different conditions
about
By using the average value E _avr and the maximum value E _{max of} the area where the target is present, the average value N _avr and the maximum value N _{max of the} area where the target is not present, and the respective ratios as S/N ratio, SN _{Calculate avr} and SN _max as _follows: That is, for the average value,
Becomes Also, regarding the maximum value,
Becomes here,
Is the Hadamard product of the matrix and the superscript bar
Indicates the inversion of logic. _{Larger values} of SN _avr and SN _max are preferable because the sharpness of the sonar image is good. Therefore, the signal processing system is optimized by searching for conditions under which these two S/N ratios become large.

FIG. 7 is a diagram showing an example of a state of a target object existing in the coordinate system. The target object 14-1 shown in FIG. 7 is an ellipsoidal target object, and the radius in each direction is 10 m (x-axis direction)×30 m (y-axis direction)×5 m (z-axis direction), and its center is The coordinates are (x, y, z)=(20, -10, -50). Here, the depth direction is the negative direction of the z axis. The sea bottom surface 14-2 is a surface of the sea bottom that measures the target object 14-1, and its center coordinates are (x, y, z)=(0, 0, -55), and a square of 200 m square. is there.

8A to 8C are examples of sonar screens when the Chebyshev filter described in Equations 1 to 3 is set in the transducer and the attenuation ratio of the side lobe to the main lobe is changed. FIG. FIG. 8A is a diagram showing an example of a sonar screen when the attenuation ratio of the side lobe to the main lobe is 90 dB. FIG. 8B is a diagram showing an example of a sonar screen when the attenuation ratio of the side lobe to the main lobe is 60 dB. FIG. 8C is a diagram showing an example of a sonar screen when the attenuation ratio of the side lobe to the main lobe is 30 dB. In addition, the reference image data used as a reference in the calculation of the image S/N ratio calculation evaluation unit 8-16 shown in FIG.
The reference image target detection area is shown in FIG. As shown in FIGS. 8A to 8C, it can be seen that when the sidelobe attenuation ratio of the Chebyshev filter is reduced, particularly, when it is reduced to 30 dB, the sharpness of the sonar image is reduced.

FIG. 9 is a diagram showing a result of calculation of SN _avr and SN _max by the image S/N ratio calculation evaluation unit 8-16 shown in FIG. 1 using Formulas 29 to 34. As shown in FIG. 9, it can be seen that SN _avr and SN _max decrease as the sidelobe attenuation ratio of the Chebyshev filter is decreased.

Note that the image S/N ratio calculation evaluation unit 8-16 may perform evaluation using only one of SN _avr and SN _max .

The wave transmitter/receiver may be configured using a piezoelectric vibrator or a magnetostrictive element that is not a composite type.

From the above results, it can be seen that the sidelobe attenuation ratio of the Chebyshev filter becomes clearer as the sonar image becomes larger by about 90 dB in the directivity and arrangement of the signal processing system and the transceiver of this example. Although the above is an example of simple parameters, it is possible to quantitatively search for optimum sonar image generation conditions by performing similar calculation evaluation.
(Modification)

FIG. 10: is a figure which shows the 1st modification of the test system of this invention.
The transmission signal generation unit 17-2, the transmission I/F 17-3, the reception I/F 17-4, the reception processing unit 17-5, and the image generation unit 17-6 included in the signal processing system 17-1 illustrated in FIG. These are the same as the transmission signal generation unit 8-2, the transmission I/F 8-3, the reception I/F 8-4, the reception processing unit 8-5, and the image generation unit 8-6 shown in FIG. 1, respectively. Further, the Fourier domain simulator 17-12 and the received sound wave time waveform converter 17-13 included in the received wave simulator system 17-7 are respectively the Fourier domain simulator 8-12 and the received sound wave time waveform shown in FIG. It is the same as the converter 8-13. Further, the transmitted sound field simulator 17-8, the target object simulator 17-9, the received sound field simulator 17-10, and the received sound pressure integrated calculation unit 17-11 included in the Fourier domain simulator 17-12 are shown in FIG. 1, respectively. It is the same as the transmitted sound field simulator 8-8, the target object simulator 8-9, the received sound field simulator 8-10, and the received sound pressure integrated calculation unit 8-11 included in the Fourier domain simulator 8-12.
The image evaluation system 17-15 shown in FIG. 10 has an image S/N ratio calculation evaluation unit 17-16. The image S/N ratio calculation/evaluation unit 17-16 is an image S/N ratio calculation/evaluator, and based on a reference image 17-14 generated by the signal processing system 17-1 using a certain condition, the image evaluation system is used. Image evaluation is performed at.

Note that the first embodiment may be premised on connection with a transducer using a piezoelectric vibrator or a magnetostrictive vibrator. Further, it may be premised on a connection with a wave transmitter/receiver, which makes it possible to scan a narrow directional beam mechanically or electronically.
(Second embodiment)

FIG. 11 is a diagram showing a second embodiment of the test system of the present invention. As shown in FIG. 11, this embodiment includes a transmitted sound field simulator 100, a target object simulator 101, a received sound field simulator 102, a received sound pressure integrated calculation unit 103, and a received sound wave time waveform conversion unit 104. doing.
The transmitted sound field simulator 100 calculates the transmitted sound field based on the transmission signal, the arrangement coordinates of the transmitter, and the physical constants. The target object simulator 101 calculates the far field of the reflected sound field produced by the surface of the target object based on the transmitted sound field calculated by the transmitted sound field simulator 100, the arrangement coordinates of the transmitter, and the physical constants. The received sound field simulator 102 calculates the received sound field by applying unit vibration speeds to a plurality of points on the receiver. The received sound pressure integrated calculator 103 calculates the directivity function to the target object based on the reflected sound field far field calculated by the target simulator 101 and the received sound field calculated by the received sound field simulator 102. The received sound wave time waveform conversion unit 104 calculates the received time waveform based on the directivity function calculated by the received sound pressure integrated calculation unit 103.

The test method in the test system shown in FIG. 11 will be described below.

FIG. 12 is a flow chart for explaining an example of the test method in the test system shown in FIG.
First, the transmitted sound field simulator 100 calculates the transmitted sound field based on the transmission signal, the arrangement coordinates of the transmitter, and the physical constants (step S1). Subsequently, the target object simulator 101 calculates the reflected sound field far field generated by the target object surface based on the transmitted sound field calculated by the transmitted sound field simulator 100, the arrangement coordinates of the transmitter, and the physical constants (step). S2). Further, the received sound field simulator 102 calculates the received sound field by giving unit vibration speeds to a plurality of points on the receiver (step S3). Either of the processing of step S2 and the processing of step S3 may be performed first.
Subsequently, the received sound pressure integrated calculation unit 103 determines a directivity function to the target object based on the reflected sound field far field calculated by the target object simulator 101 and the received sound field calculated by the received sound field simulator 102. Calculate (step S4). The received sound wave time waveform converter 104 calculates the time waveform of the received wave based on the directivity function calculated by the received sound pressure integrated calculator 103 (step S5).

In this way, by simulating the wave transmitter and the wave receiver, it is possible to easily obtain an accurate sonar screen.

The processing performed by each component provided in the above-described test system may be performed by a logic circuit manufactured according to the purpose. Further, a computer program (hereinafter, referred to as a program) in which the processing content is described as a procedure is recorded in a recording medium readable by a test system, and the program recorded in the recording medium is read into the test system and executed. May be The recording medium readable by the test system is a removable recording medium such as a floppy (registered trademark) disk, a magneto-optical disk, a DVD (Digital Versatile Disc), a CD (Compact Disc), and a Blu-ray (registered trademark) Disc. In addition to the medium, it refers to a memory such as a ROM (Read Only Memory) and a RAM (Random Access Memory) built in the test system, an HDD (Hard Disc Drive), and the like. The program recorded on this recording medium is read by a CPU (Central Processing Unit) provided in the test system, and the same processing as that described above is performed under the control of the CPU. Here, the CPU operates as a computer that executes the program read from the recording medium in which the program is recorded.

The whole or part of the exemplary embodiments disclosed above can be described as, but not limited to, the following supplementary notes.
(Appendix 1)
Based on the transmission signal and the arrangement coordinates of the transmitter and the physical constants, a transmitted sound field simulator for calculating a transmitted sound field,
Based on the transmitted sound field calculated by the transmitted sound field simulator, the arrangement coordinates of the transmitter and the physical constants, a target object simulator for calculating the reflected sound field far field generated by the target object surface,
A receiver sound field simulator that calculates the receiver sound field by applying unit vibration speeds to multiple points on the receiver,
Reflected sound field far field calculated by the target simulator, based on the received sound field calculated by the received sound field simulator, a received sound pressure integrated calculation unit for calculating a directivity function to the target object,
A received sound wave time waveform converter that calculates a time waveform of a received wave based on the directivity function calculated by the received sound pressure integrated calculator.
(Supplementary Note 2) A reference image generation unit that generates a reference image based on the directivity function calculated by the received sound pressure integrated calculation unit,
An image S/N ratio calculation evaluation unit that evaluates an image generated based on the time waveform of the received wave calculated by the received sound wave time waveform conversion unit based on the reference image generated by the reference image generation unit. The test system according to Appendix 1, which has.
(Supplementary Note 3) The image S/N ratio calculation/evaluation unit uses the reference image as a reference, and the SN (Signal-) of the image generated based on the received time waveform calculated by the received sound wave time waveform conversion unit. The test system according to Note 2, wherein evaluation is performed by calculating a Noise) ratio.
(Supplementary note 4) The test system according to any one of supplementary notes 1 to 3, wherein the received sound pressure integrated calculation unit calculates the directional function using a Green's function.
(Supplementary Note 5) The transmitted sound field simulator calculates the transmitted sound field using Fourier transform,
The received sound field simulator uses Fourier transform to calculate the received sound field,
The test system according to any one of appendices 1 to 4, wherein the received sound wave time waveform converter calculates the time waveform of the received wave using an inverse Fourier transform.
(Supplementary note 6) A transmitted sound field simulator for calculating a transmitted sound field based on a transmission signal, a placement coordinate of a transmitter, and a physical constant,
Based on the transmitted sound field calculated by the transmitted sound field simulator, the arrangement coordinates of the transmitter and the physical constants, a target object simulator for calculating the reflected sound field far field created by the target surface,
A receiver sound field simulator that calculates the receiver sound field by applying unit vibration speeds to multiple points on the receiver,
Reflected sound field far field calculated by the target simulator, based on the received sound field calculated by the received sound field simulator, a received sound pressure integrated calculation unit for calculating a directivity function to the target object,
A waveform simulator device comprising: a received sound wave time waveform conversion unit that calculates a received time waveform based on the directivity function calculated by the received sound pressure integrated calculation unit.
(Supplementary Note 7) A process of calculating a transmitted sound field based on the transmission signal, the arrangement coordinates of the transmitter, and the physical constants,
Based on the transmitted sound field, the arrangement coordinates of the transmitter and the physical constants, a process of calculating a reflected sound field far field produced by the target surface,
A process of calculating a received sound field by giving unit vibration speeds to a plurality of points of a receiver,
Based on the reflected sound field far field and the received sound field, a process of calculating a directivity function to the target object,
A test method for performing processing of calculating a time waveform of a received wave based on the calculated directivity function.
(Appendix 8)
Based on the transmission signal, the arrangement coordinates of the transmitter and the physical constants, a procedure for calculating the transmitted sound field,
Based on the transmitted sound field and the arrangement coordinates of the transmitter and the physical constants, a procedure for calculating a reflected sound field far field produced by the target surface,
A procedure for calculating the received sound field by applying unit vibration speeds to multiple points on the receiver,
Based on the reflected sound field far field and the received sound field, a step of calculating a directivity function to the target,
A program for executing a procedure for calculating a time waveform of a received wave based on the calculated directivity function.

8-1, 17-1 Signal Processing System 8-2, 17-2 Transmission Signal Generation Unit 8-3, 17-3 Transmission I/F
8-4, 17-4 Receive I/F
8-5, 17-5 Reception processing unit 8-6, 17-6 Image generation unit 8-7, 17-7 Receiving waveform simulator system 8-8, 17-8, 100 Transmit sound field simulator 8-9, 17 -9,101 Target simulator 8-10,17-10,102 Received sound field simulator 8-11,17-11,103 Received sound pressure integrated calculation unit 8-12,17-12 Fourier domain simulator 8-13,17 -13,104 Received sound wave time waveform conversion unit 8-14 Reference image generation unit 8-15,17-15 Image evaluation system 8-16,17-16 Image S/N ratio calculation evaluation unit 9-1 Transmitter surface 9-2, 14-1 Target 9-3 Sea-bed hidden surface by target 9-4, 14-2 Sea-bottom 9-5 Receiver plane 12-1 Transmitting (receiving) plane 12-2 Coordinate system 13-1 Reference Image Data 13-2 Reference Image Target Object Detection Area 17-14 Reference Image

Claims (8)

Based on the transmission signal and the arrangement coordinates of the transmitter and the physical constants, a transmitted sound field simulator for calculating a transmitted sound field,
Based on the transmitted sound field calculated by the transmitted sound field simulator, the arrangement coordinates of the transmitter and the physical constants, a target object simulator for calculating the reflected sound field far field generated by the target object surface,
A receiver sound field simulator that calculates the receiver sound field by applying unit vibration speeds to multiple points on the receiver,
Reflected sound field far field calculated by the target simulator, based on the received sound field calculated by the received sound field simulator, a received sound pressure integrated calculation unit for calculating a directivity function to the target object,
A received sound wave time waveform converter that calculates a time waveform of a received wave based on the directivity function calculated by the received sound pressure integrated calculator. The test system according to claim 1,
Based on the directivity function calculated by the received sound pressure integrated calculation unit, a reference image generation unit that generates a reference image,
An image S/N ratio calculation evaluation unit that evaluates an image generated based on the time waveform of the received wave calculated by the received sound wave time waveform conversion unit based on the reference image generated by the reference image generation unit. Having a test system. The test system according to claim 2,
The image S/N ratio calculation/evaluation unit uses the reference image as a reference to calculate the SN (Signal-Noise) ratio of the image generated based on the time waveform of the received wave calculated by the received sound wave time waveform conversion unit. A test system that evaluates by calculating. The test system according to any one of claims 1 to 3,
The received sound pressure integrated calculator is a test system for calculating the directional function using a Green's function. The test system according to any one of claims 1 to 4,
The transmitted sound field simulator uses Fourier transform to calculate the transmitted sound field,
The received sound field simulator uses Fourier transform to calculate the received sound field,
The received sound wave time waveform conversion unit is a test system for calculating a time waveform of the received wave using an inverse Fourier transform. Based on the transmission signal and the arrangement coordinates of the transmitter and the physical constants, a transmitted sound field simulator for calculating a transmitted sound field,
Based on the transmitted sound field calculated by the transmitted sound field simulator, the arrangement coordinates of the transmitter and the physical constants, a target object simulator for calculating the reflected sound field far field created by the target surface,
A receiver sound field simulator that calculates the receiver sound field by applying unit vibration speeds to multiple points on the receiver,
The reflected sound field far field calculated by the target simulator, and the received sound field calculated by the received sound field simulator, the received sound pressure integrated calculation unit for calculating the directivity function to the target object,
A waveform simulator device comprising: a received sound wave time waveform conversion unit that calculates a received time waveform based on the directivity function calculated by the received sound pressure integrated calculation unit. Based on the transmission signal and the arrangement coordinates of the transmitter and the physical constants, the process of calculating the transmitted sound field,
Based on the transmitted sound field, the arrangement coordinates of the transmitter and the physical constants, a process of calculating a reflected sound field far field produced by the target surface,
A process of calculating a received sound field by giving unit vibration speeds to a plurality of points of a receiver,
Based on the reflected sound field far field and the received sound field, a process of calculating a directivity function to the target object,
A test method for performing processing of calculating a time waveform of a received wave based on the calculated directivity function. On the computer,
Based on the transmission signal, the arrangement coordinates of the transmitter and the physical constants, a procedure for calculating the transmitted sound field,
Based on the transmitted sound field and the arrangement coordinates of the transmitter and the physical constants, a procedure for calculating a reflected sound field far field produced by the target surface,
A procedure for calculating the received sound field by applying unit vibration speeds to multiple points on the receiver,
Based on the reflected sound field far field and the received sound field, a step of calculating a directivity function to the target,
A program for executing a procedure for calculating a time waveform of a received wave based on the calculated directivity function.