JP6529689B2 - Observation apparatus and observation method - Google Patents

Description

  The present invention relates to an observation apparatus and an observation method for observing an object embedded in a road surface or the like.

2. Description of the Related Art An observation device for observing the state inside a dielectric using the nature as waves of electromagnetic waves transmitted through the dielectric has been known. Since this observation device can perform nondestructive observation, it can perform mine detection, resource exploration, and the like.
For example, Patent Document 1 describes a method of searching for a cavity generated in the ground using an electromagnetic wave radar. In this method, when electromagnetic waves are irradiated to a target surface in which the presence of a cavity is expected to be generated in order to improve the accuracy of searching for the cavity, time-series data is acquired by acquiring reflected wave data of the electromagnetic wave in time series The unnecessary reflected wave data is removed from the

JP, 2015-197434, A

In the cavity thickness search method described in Patent Document 1, in order to remove unnecessary waves using time-series data of reflected waves when unnecessary waves are generated, the position where the unnecessary waves are generated is specified by the above-mentioned time-series data There is a need.
However, in the observation system of the embedded object, the electromagnetic wave irradiated to the observation target is scattered at various places other than the embedded object, so it is very difficult to specify the position where the unwanted wave is generated. Can not observe the target with high resolution.

  This invention solves the said subject, and it aims at obtaining the observation apparatus and observation method which can observe a target with high resolution by suppressing an unnecessary wave.

An observation device according to the present invention includes a preprocessing unit, a high resolution processing unit, an unnecessary wave suppression processing unit, and a target detection processing unit. The pre-processing unit corrects the contrast by removing a direct current component from wave data in which an electromagnetic wave irradiated and scattered on a dielectric to be observed is represented by a two-dimensional image. The high resolution processing unit performs high resolution on the wave data processed by the pre-processing unit. The unnecessary wave suppression processing unit converts the wave data processed by the high resolution processing unit into data in the frequency space, and suppresses unnecessary waves of the wave data converted into the frequency space. The target detection processing unit detects a signal according to a target inside the dielectric from the wave data in which the unnecessary wave is suppressed by the unnecessary wave suppression processing unit. Further, non Yonami suppression unit, a high resolution has been wave data Fourier transform the data in frequency space by the high resolution processing section, among the frequency components of the wave data in the frequency space, frequency components lower than the threshold value Are removed as unwanted waves and then inverse Fourier transformed to real space data. Moreover, the goal detection processing unit calculates a target detection threshold from the band on the frequency corresponding to the azimuth axis of the threshold value and the target, among the signals indicating the wave data, induced a signal exceeding the goal detection threshold It is detected as a signal according to the target inside the collector.

  According to the present invention, the resolution of the wave data of the electromagnetic wave irradiated and scattered to the dielectric is increased and then the unnecessary wave is suppressed. Therefore, it is possible to suppress the unnecessary wave and observe the target with high resolution.

It is a figure which shows the example of observation using the observation apparatus which concerns on Embodiment 1 of this invention. FIG. 2 is a block diagram showing a functional configuration of the observation device according to Embodiment 1. FIG. 3A is a block diagram showing a hardware configuration that implements the function of the observation device according to Embodiment 1. FIG. 3B is a block diagram showing a hardware configuration that executes software that implements the functions of the observation device according to Embodiment 1. 5 is a flowchart showing an operation of the observation device according to Embodiment 1. FIG. 2 is a diagram showing an outline of observation of wave data in the first embodiment. It is a flowchart which shows operation | movement of a pre-processing part. It is a flowchart which shows operation | movement of a resolution enhancement process part. It is a figure which shows the example of the wave data by which high resolution was carried out. It is a flowchart which shows operation | movement of an unnecessary wave suppression process part and a target detection process part. It is a figure showing an outline of unnecessary wave suppression. 5 is a diagram showing an example of final observation data by the observation device according to Embodiment 1. FIG.

Hereinafter, in order to explain the present invention in more detail, embodiments for carrying out the present invention will be described according to the attached drawings.
Embodiment 1
FIG. 1 is a diagram showing an observation example using an observation device 1 according to Embodiment 1 of the present invention.
As shown in FIG. 1, the observation device 1 is incorporated in the radar device 1a and mounted on a movable body such as a truck 1b. The user A moves the carriage 1 b in the azimuth direction (x-axis direction).
The radar apparatus 1a irradiates an electromagnetic wave beam in a direction orthogonal to the azimuth direction toward a dielectric such as a road surface at an irradiation angle Δθ, and receives scattered waves in the dielectric.
When an embed or cavity is present inside the dielectric, the electromagnetic wave scatters at the interface of the dielectric and scatters at the interface of the embed or the cavity. The radar device 1 a generates a two-dimensional image representing an electromagnetic wave scattered on the dielectric side and outputs the two-dimensional image to the observation device 1. Hereinafter, this two-dimensional image is called wave data. The observation device 1 observes a buried object or a cavity inside a dielectric using wave data input from the radar device 1a.

FIG. 2 is a block diagram showing a functional configuration of the observation device 1. As shown in FIG. 2, the observation device 1 includes a wave data storage unit 2, a preprocessing unit 3, a high resolution processing unit 4, an unnecessary wave suppression processing unit 5, a target detection processing unit 6, and an output data storage unit 7. .
The wave data storage unit 2 is a storage unit that stores the wave data input from the radar device 1a. The wave data stored in the wave data storage unit 2 is transferred to the pre-processing unit 3.
The preprocessing unit 3 removes the DC component from the wave data transferred from the wave data storage unit 2 and corrects the contrast. For example, the preprocessing unit 3 removes the DC component in the slant range direction from the wave data, subsequently removes the DC component in the azimuth direction, and performs contrast correction. By applying these pretreatments, the attenuation of the wave when the electromagnetic wave passes through the dielectric is corrected.

The high resolution processing unit 4 performs high resolution on the wave data processed by the pre-processing unit 3.
For example, the high resolution processing unit 4 converts the wave data subjected to the pre-processing into data in the frequency space, compensates the wave front of the wave data into a spherical shape in the frequency space, and orthogonalizes the wave transmission direction. It is converted into real space data after applying Stolt interpolation.
The unnecessary wave suppression processing unit 5 converts the wave data that has been subjected to the high resolution processing by the high resolution processing unit 4 into data in the frequency space, and suppresses unnecessary waves of the wave data converted into the frequency space.
For example, the unnecessary wave suppression processing unit 5 removes the frequency component lower than the threshold from the frequency components of the wave data in the frequency space obtained by Fourier transforming the wave data, and performs inverse Fourier transform to data in real space. Do. The threshold is set based on the center frequency, the beam width, and the irradiation interval of the electromagnetic wave irradiated to the dielectric.

The target detection processing unit 6 detects a signal according to a target in the dielectric from the wave data in which the unnecessary wave is suppressed by the unnecessary wave suppression processing unit 5.
For example, the target detection processing unit 6 detects a signal whose intensity exceeds the target detection threshold from the signal indicated by the wave data after the unnecessary wave is suppressed, and generates binarized data from the detected signal.
The binarized data is output data of the target detection processing unit 6. The target detection threshold is calculated based on the threshold used for the unnecessary wave suppression process.
The output data storage unit 7 is a storage unit that stores output data input from the target detection processing unit 6.

The wave data storage unit 2 and the output data storage unit 7 may be realized by an external storage device provided separately from the observation device 1. In this configuration, the wave data from the radar device 1a is stored in the wave data storage unit 2 in the external storage device, and the observation device 1 reads out the wave data from the external storage device. Further, the output data obtained by the observation device 1 is stored in the output data storage unit 7 in the external storage device.
That is, in the observation device 1 according to the first embodiment, the wave data storage unit 2 and the output data storage unit 7 are not essential components and may be omitted.

FIG. 3A is a block diagram showing a hardware configuration for realizing the function of the observation device 1. FIG. 3B is a block diagram showing a hardware configuration that executes software for realizing the functions of the observation device 1. In FIGS. 3A and 3B, the input storage device 100 is a storage device that stores data to be input to the observation device 1, and is the wave data storage unit 2 shown in FIG.
The output storage device 101 is a storage device that stores output data generated by the observation device 1 and is the output data storage unit 7 shown in FIG.

  Each function of the preprocessing unit 3, the resolution enhancement processing unit 4, the unnecessary wave suppression processing unit 5 and the target detection processing unit 6 in the observation device 1 is realized by a processing circuit. That is, the observation device 1 includes a processing circuit for performing these functions. The processing circuit may be a dedicated hardware or a central processing unit (CPU) that executes a program stored in the memory.

When the processing circuit is the dedicated hardware processing circuit 102 shown in FIG. 3A, the processing circuit 102 may be, for example, a single circuit, a composite circuit, a programmed processor, a parallel programmed processor, an application specific integrated circuit (ASIC). , FPGA (Field-Programmable Gate Array) or a combination thereof.
The respective functions of the preprocessing unit 3, the resolution enhancement processing unit 4, the unnecessary wave suppression processing unit 5 and the target detection processing unit 6 in the observation device 1 may be realized by processing circuits, respectively, It may be realized by a processing circuit.

  When the processing circuit is the processor 103 shown in FIG. 3B, each function of the preprocessing unit 3, the high resolution processing unit 4, the unnecessary wave suppression processing unit 5 and the target detection processing unit 6 is software, firmware, or software and firmware It is realized by the combination of The software and firmware are written as a program and stored in the memory 104.

The processor 103 implements each function by reading and executing a program stored in the memory 104. That is, the observation device 1 includes the memory 104 for storing a program that is to be executed as a result of the processing of steps ST1 to ST4 shown in FIG. 4 when executed by the processing circuit.
Also, these programs cause a computer to execute the procedure or method of the preprocessing unit 3, the resolution enhancement processing unit 4, the unnecessary wave suppression processing unit 5 and the target detection processing unit 6.

  Here, the memory is, for example, non-volatile or volatile semiconductor memory such as RAM (Random Access Memory), ROM (Read Only Memory), flash memory, EPROM (Erasable Programmable ROM), EEPROM (Electrically EPROM), etc., magnetic disk , Flexible disks, optical disks, compact disks, mini disks, DVDs (Digital Versatile Disks), etc.

In addition, the functions of the preprocessing unit 3, the resolution enhancement processing unit 4, the unnecessary wave suppression processing unit 5, and the target detection processing unit 6 are partially realized by dedicated hardware and partially realized by software or firmware. You may For example, the preprocessing unit 3 and the high resolution processing unit 4 realize their functions by a dedicated hardware processing circuit, and for the unnecessary wave suppression processing unit 5 and the target detection processing unit 6, the processor 103 stores in the memory 104. By executing the stored program, the function is realized.
In this way, the processing circuit can realize the above-described functions by hardware, software, firmware or a combination thereof.

Next, the operation will be described.
FIG. 4 is a flow chart showing the operation of the observation apparatus 1 and shows a series of processes from the pretreatment of wave data to detection of a target embedded object.
First, the preprocessing unit 3 preprocesses the wave data transferred from the wave data storage unit 2 (step ST1). The pre-processing includes removal of DC components in the slant range direction, removal of DC components in the azimuth direction, and contrast correction. Details of these processes will be described later with reference to FIGS. 5 and 6.

  Next, the high resolution processing unit 4 performs high resolution on the wave data preprocessed by the preprocessing unit 3 (step ST2). The resolution enhancement processing includes Fourier transform of wave data, compensation of wave front of wave data, Stolt interpolation, and inverse Fourier transform. Details of these processes will be described later with reference to FIGS. 7 and 8.

  The unnecessary wave suppression processing unit 5 converts the wave data processed by the high resolution processing unit 4 into data in the frequency space, and then suppresses the unnecessary wave (step ST3). For example, among frequency components of wave data converted into data in the frequency space, frequency components lower than the threshold are removed as unnecessary waves. The details of the unnecessary wave suppression process will be described later with reference to FIGS. 9 and 10.

The target detection processing unit 6 detects a signal corresponding to the embedded object in the dielectric from the wave data processed by the unnecessary wave suppression processing unit 5 (step ST4). Among the signals indicated by wave data in which unnecessary waves are suppressed, a signal having an intensity exceeding the target detection threshold is detected as a target signal.
Details of the target detection process will be described later with reference to FIGS. 9 to 11.

FIG. 5 is a diagram showing an outline of observation of wave data, and shows an outline of wave data observation by the radar device 1a shown in FIG. In the observation system 10, the dielectric to be observed is a space 21 having a dielectric constant ε _{r, 1} . The transceivers 11 to 14 included in the radar device 1a are disposed in the space 20 having a dielectric constant ε _{r, 0} (ε _{r, 0} <ε _{r, 1} ) lower than the dielectric constant ε _{r, 1} of the space 21. . An area 22 indicated by a broken line is an area including the inside of the dielectric space 21 in which the embedded material 24 is embedded. The buried object 24 has a dielectric constant ε _{r, 2} .

The transmitters / receivers 11 to 14 emit pulsed electromagnetic waves 15 to 18 toward the space 21.
In the region 22, the electromagnetic waves 15 to 18 are scattered at the interface 23 between the space 20 and the space 21 having different dielectric constants, and are scattered at the interface 25 between the space 21 and the embedded object 24 having different dielectric constants. The transceivers 11 to 14 receive the electromagnetic waves 15 to 18 scattered at the boundary surfaces 23 and 25.
The radar device 1 a generates two-dimensional data (wave data) indicating electromagnetic waves scattered at the boundary surfaces 23 and 25 based on the received information of the electromagnetic waves 15 to 18 and outputs the two-dimensional data to the observation device 1.
Although FIG. 5 shows the case where the radar device 1a observes using a plurality of transceivers arranged in the x-axis direction, the radar device 1a is configured such that one transceiver is arranged in the azimuth direction (x-axis direction in FIG. The observation may be performed while moving to.

Next, the details of the pre-processing will be described.
FIG. 6 is a flowchart showing the operation of the preprocessing unit 3.
When the wave data transferred from the wave data storage unit 2 is input, the preprocessing unit 3 removes the DC component in the slant range direction from the input wave data (step ST1a).
For example, in consideration of the case where the wave data s (x, t) is fixed-point data, the preprocessing unit 3 determines the DC component s _{DC, t} (x, t) in the slant range direction by the following equation (1) Estimate using). Subsequently, the preprocessing unit 3 removes the DC component s _{DC, t} (x, t) in the slant range direction from the wave data s (x, t) using the following equation (2).
In the following equation (1), T _PRI is a pulse repetition period at which the radar device 1 a transmits an electromagnetic wave. In the following equation (2), wave data s _{0, t} (x, t) is wave data from which the DC component s _{DC, t} (x, t) has been removed.

Next, the preprocessing unit 3 removes the direct current component in the azimuth direction from the wave data from which the direct current component s _{DC, t} (x, t) has been removed (step ST 2 a). For example, in consideration of the case where wave data s (x, t) is fixed-point type data, the preprocessing unit 3 considers the direct current component s _{DC, x} (x, t) in the azimuth direction into the following equation (3) Use to estimate. The preprocessing unit 3 uses the following equation (4) to remove the direct current component in the slant range direction from the wave data s _{0, t} (x, t), and the direct current component s _{DC, x} (x, t) in the azimuth direction. Remove
In the following formula (3), L _x is the opening length in the azimuth direction. In the following equation (4), the wave data s _{0, t, x} (x, t) is wave data obtained by removing the DC component in the slant range direction and the DC component in the azimuth direction.
The x axis [-L _x / 2, L _x / 2] is the azimuth direction, the t axis [0, T _pri ] is the slant range direction, and the z axis [-L _z / 2, L _z / 2] is the azimuth direction. It is an elevation direction.

Finally, the preprocessing unit 3 corrects the contrast of the wave data (step ST3a). Thereby, the attenuation of the wave data when the electromagnetic wave passes through the dielectric is corrected.
For example, in consideration of the attenuation of the wave data s _{0, t, x} (x, t) when passing through the dielectric, the pre-processing unit 3 calculates the contrast correction function s _{CNT, t,} shown in the following equation (5) Define _x (x, t). Next, the preprocessing unit 3 performs contrast correction on the wave data s _{0, t, x} (x, t) using the following equation (6).
In the following formula (5), T _obs is all azimuth time (slow time).
In the following equation (6), the wave data s _PRE (x, t) is wave data subjected to the above-described contrast correction.

Next, the details of the high resolution processing will be described.
FIG. 7 is a flowchart showing the operation of the high resolution processing unit 4.
The high resolution processing unit 4 performs two-dimensional fast Fourier transform (hereinafter, referred to as two-dimensional FFT) on the wave data s _PRE (x, t) using the following equation (7) (step ST 1 b) . In the following equation (7), the wave data S _PRE (k _x , kt) is wave data in the frequency space, and c is the velocity of light.

Next, the high resolution processing unit 4 performs so-called azimuth batch compression to compensate the wave front of the wave data into a spherical shape in the frequency space (step ST2b). For example, the resolution enhancement processing unit 4 performs azimuth batch compression on the wave data S _PRE (k _x , kt) according to the following equation (8). By the azimuth batch compression, the wave fronts of the wave data S _PRE (k _x , k) are aligned, and wave data S _BULK (k _x , k) obtained by focusing the image of the wave data is obtained. However, in the following equation (8), R ₀ is a focus distance, and is defined by, for example, the following equation (9). k _z is a wave number defined by the following equation (10).

Subsequently, the high resolution processing unit 4 performs the Strot interpolation to orthogonalize the wave transmission direction of the wave data S _BULK (k _x , k) (step ST3 b).
Sutoruto interpolation is a process of converting the wave data _S BULK _(k x, _k) a wave-space _(k x, k) in the _(k x, k _z) in. The wave data S _SAR (k _x , k _z ) is wave data obtained by the Stolt interpolation.

The high resolution processing unit 4 performs two-dimensional inverse fast Fourier transform (hereinafter referred to as two-dimensional IFFT) on the wave data S _SAR (k _x , k _z ) using the following equation (11) (Step ST4b). In the following equation (11), the wave data I _SAR (x, z) is wave data in the real space. In the following equation (11), IFFT is performed in two dimensions in the azimuth direction (x axis) and the elevation direction (z axis) with respect to the wave data S _SAR (k _x , k _z ).

FIG. 8 is a diagram showing an example of the high resolution wave data I _SAR (x, z), and the wave data I _SAR (x, z) is described as wave data 26. The wave data 26 is, for example, data obtained by observing the region 22 shown in FIG. The image showing the unwanted wave signal B1 in the wave data 26 is due to the scattered wave at the boundary surface 23 shown in FIG. 5, and the image showing the buried object signal A1 in the wave data 26 is shown in FIG. It originates in the scattered wave in the interface 25. The images showing the unnecessary wave signals B1 to B5 in the wave data 26 are caused by the scattered waves other than the embedded object signal A1, and are images spread in layers in the azimuth direction.

The buried object signal A1 is a signal caused by the electromagnetic wave scattered by the buried object or the cavity. Therefore, the image represented by the embedded object signal A1 exists in the image of the wave data in a sufficiently narrow region, that is, locally, as compared with the image represented by the unnecessary wave signals B1 to B5 spread in layers.
The observation apparatus 1 according to the first embodiment performs unnecessary wave suppression processing described later with reference to FIGS. 9 and 10 to the wave data to generate unnecessary waves other than the embedded object signal A1 such as the unnecessary wave signals B1 to B5. Suppress This improves the detection efficiency of the buried object.

In particular, the high resolution processing unit 4 performs two-dimensional Fourier transformation on the wave data preprocessed by the pre-processing unit 3, performs azimuth batch compression on the converted wave data, and further the wave transmission direction Implement so-called two-dimensional synthetic aperture processing that implements interpolation to orthogonalize.
As a result, the locality of the wave is improved, the position estimation accuracy of the embedded object is improved, and it becomes possible to observe even the unnecessary wave with high resolution.

  The two-dimensional synthetic aperture processing is an Omega-K method, but is not limited thereto. For example, the range Doppler method or the back projection method may be used. Although Stroll interpolation is performed in step ST3b, for example, sinc interpolation or cubic interpolation may be performed.

  In step ST4b of FIG. 7, IFFT is applied to wave data in two dimensions in the azimuth direction (x-axis) and elevation direction (z-axis) to obtain wave data 26 after the two-dimensional synthetic aperture processing is performed. The The processing in step ST4b may be omitted, and instead, the FFT in the azimuth direction performed in step ST1b may be performed as the IFFT in the elevation direction.

Next, details of the unnecessary wave suppression process and the target detection process will be described.
FIG. 9 is a flowchart showing the operation of the unnecessary wave suppression processing unit 5 and the target detection processing unit 6. The unnecessary wave suppression processing unit 5 performs FFT in the azimuth direction on the wave data I _SAR (x, z) input from the high resolution processing unit 4 (step ST1 c). Thereby, wave data of real space is converted to data of frequency space.
For example, the unwanted wave suppression processing unit 5 performs the FFT in the azimuth direction according to the following equation (12) on the wave data I _SAR (x, z) to generate the wave data S _SAR (k Convert to _x , z).

上記低周波数成分が、図８に示した層状に広がりをもつ不要波信号Ｂ１〜Ｂ５である。
波動データＳ_{ＳＡＲ，ＲＥＭＯＶＥ}（ｋ_ｘ，ｚ）は、波動データＳ_ＳＡＲ（ｋ_ｘ，ｚ）からカットオフ周波数ｆ_ｘ以下の低周波数成分を除去した後の波動データである。The unnecessary wave suppression processing unit 5 applies a high pass filter (HPF) to the wave data S _SAR (k _x , z) in the azimuth frequency space (step ST2 c).
For example, by applying the HPF represented by the following equation (13), the unnecessary wave suppression processing unit 5 determines a low frequency component (| or less than the HPF cutoff frequency f _x from the wave data S _SAR (k _x , z) Remove k _x | ≦ f _x ). The cutoff frequency f _x is a threshold for unnecessary wave suppression.

The low frequency components are the unnecessary wave signals B1 to B5 having a layer-like spread shown in FIG.
The wave data S _{SAR, REMOVE} (k _x , z) is wave data after removing low frequency components below the cutoff frequency f _x from the wave data S _SAR (k _x , z).

The HPF process described above utilizes the uncertainty principle of the Fourier transform.
For example, as shown in FIG. 10, the unwanted wave signal that spreads in layers in real space has a lower frequency and a narrower band in frequency space than a buried object signal that exists locally in real space.
On the other hand, the embedded object signal present locally in real space is wider in frequency space than the unwanted wave signal that spreads in layers in real space. Therefore, FFT is performed on the wave data on the x-axis in the azimuth direction to convert it into data in the frequency space, and an HPF is applied which cuts off the cutoff frequency or less specified on the frequency axis. As a result, it is possible to suppress an unnecessary wave having a frequency lower than that of the buried object signal.

The cutoff frequency f _x used in the HPF processing of step ST 2 c is calculated by the unnecessary wave suppression processing unit 5 based on the radar device information. The radar apparatus information includes the center frequency, the beam width and the irradiation interval of the electromagnetic wave irradiated to the dielectric.
For example, the unnecessary wave suppression processing unit 5 calculates the aperture length L _x in the azimuth direction based on the radar device information, and calculates the cutoff frequency f _x from the following equation (13-1).
The unnecessary wave suppression processing unit 5 sets the cutoff frequency f _x calculated in this manner to the HPF (step ST3 c). Further, the unnecessary wave suppression processing unit 5 outputs the cutoff frequency f _x to the target detection processing unit 6.

Next, the unnecessary wave suppression processing unit 5 performs IFFT processing in the azimuth direction on the wave data S _SAR (k _x , z) in which the unnecessary wave is suppressed (step ST4 c). Thereby, wave data in frequency space is converted to data in real space.
For example, the unnecessary wave suppression processing unit 5 performs an IFFT according to the following equation (14) on the wave data S _{SAR, REMOVE} (k _x , z) of the azimuth frequency space in which the unnecessary wave is suppressed. , The unnecessary wave is converted into suppressed wave data I _{SAR, REMOVE} (x, z).
The unnecessary wave suppression processing unit 5 outputs, to the target detection processing unit 6, the wave data I _{SAR, REMOVE} (x, z) in which the unnecessary wave is suppressed and the cutoff frequency f _x calculated in step ST3c.

In step ST1c and step ST4c shown in FIG. 9, FFT and IFFT only in the azimuth direction are performed, in order to efficiently suppress unnecessary waves spreading in layers in the azimuth direction with low load.
In the case where an unwanted wave that spreads in layers in the elevation direction (z axis) is to be suppressed, a two-dimensional FFT in the elevation direction and a two-dimensional IFFT may be performed in the processing of steps ST1c and ST4c.

The target detection processing unit 6 calculates a threshold T for target detection according to the following equation (15) and the following equation (16) using the cutoff frequency f _x input from the unnecessary wave suppression processing unit 5 (step ST1 d). A _x is a power loss coefficient of the buried object signal, and is calculated according to the following equation (16). B _x indicates a band on a frequency corresponding to the azimuth axis (x axis) of the embedded object 24 shown in FIG. T _ori is an initial threshold in initial setting, and for example, in wave data after amplitude normalization, if the initial threshold T _ori is 2, it corresponds to a standard deviation 22.

The target detection processing unit 6 detects only the signal exceeding the target detection threshold T among the wave data of the real space in which the unnecessary wave is suppressed (step ST2 d). For example, the target detection processing unit 6 outputs a signal [I _{SAR, REMOVE} (x, z) exceeding the threshold T among the signals indicated by the wave data I _{SAR, REMOVE} (x, z) of the real space in which the unnecessary wave is suppressed. ≧ T] is detected. Thus, binarized data I _BINARI (x, z) is obtained.

FIG. 11 is a diagram showing an example of final observation data by the observation device 1. The observation data is the _binarized data I _BINARI (x, z) obtained by the target detection processing unit 6.
In FIG. 11, the binarized data 27 is binarized data I _BINARI (x, z), which corresponds to the observation data of the region 22 shown in FIG. The buried object signal A2 is a signal obtained by performing the target detection process by suppressing unnecessary waves from the buried object signal A1 in the wave data 26 shown in FIG. The unnecessary wave signals B6 and B7 in the binarized data 27 are signals having frequencies higher than the cutoff frequency f _x and are unnecessary waves which are not suppressed and remain.
The image area indicating the buried object signal A2 in the binarized data 27 is narrower than the image area of the buried object signal A1 in the wave data 26. This is because the low frequency component of the embedded object signal which becomes a wide band in the frequency domain is removed by suppressing the unnecessary wave, and a power loss occurs.

As described above, in the observation device 1 according to the first embodiment, the preprocessing unit 3 removes the DC component from the wave data in which the electromagnetic wave emitted and scattered by the dielectric to be observed is represented by a two-dimensional image. , Correct the contrast. The high resolution processing unit 4 performs high resolution on the wave data processed by the pre-processing unit 3. The unnecessary wave suppression processing unit 5 converts the wave data processed by the high resolution processing unit 4 into data in the frequency space, and suppresses unnecessary waves of the wave data converted into the frequency space. The target detection processing unit 6 detects a signal according to a target in the dielectric from the wave data in which the unnecessary wave is suppressed by the unnecessary wave suppression processing unit 5.
After the resolution of the wave data is increased, the unnecessary wave remaining in the wave data is suppressed, so that the unnecessary wave caused by other than the embedded object can be suppressed, and the detection efficiency of the embedded object can be enhanced.

  In the observation device 1 according to the first embodiment, the unnecessary wave suppression processing unit 5 Fourier-transforms the wave data that has been subjected to the high resolution processing by the high resolution processing unit 4 into data in the frequency space, and the frequency of the wave data in the frequency space Among the components, frequency components lower than the threshold are removed as unnecessary waves and then inverse Fourier transformed into data in real space. As a result, it is possible to suppress unnecessary waves remaining in the wave data from among the high-resolution wave data.

  In the observation device 1 according to the first embodiment, the unnecessary wave suppression processing unit 5 sets the above-mentioned threshold value based on the central frequency, the beam width and the irradiation interval of the electromagnetic wave irradiated to the dielectric. Thereby, it is possible to appropriately suppress unnecessary waves caused by things other than the buried object.

  In the observation device 1 according to the first embodiment, the target detection processing unit 6 calculates the target detection threshold T from the above threshold, and among the signals represented by the wave data, signals exceeding the target detection threshold are included in the dielectric. As a signal according to the Thereby, the signal according to the target can be detected accurately.

  In the scope of the invention, the present invention can modify any of the components of the embodiment or omit any of the components of the embodiment.

  Since the observation apparatus according to the present invention can observe the target with high resolution by suppressing unnecessary waves generated inside the dielectric, it is possible to perform landmine exploration, underground object exploration such as underground cavities, and the inside of a structure. It is suitable for diagnosis and the like.

  DESCRIPTION OF SYMBOLS 1 observation device, 1a radar device, 1b truck, 2 wave data storage unit, 3 preprocessing unit, 4 high resolution processing unit, 5 unnecessary wave suppression processing unit, 6 target detection processing unit, 7 output data storage unit, 10 observation System, 11 to 14 transceivers, 15 to 18 electromagnetic waves, 20, 21 spaces, 22 areas, 23, 25 boundaries, 24 embedded objects, 26 wave data, 27 binarized data, 100 storage devices for input, 101 for output Storage, 102 processing circuits, 103 processors, 104 memories.

Claims (3)

A preprocessing unit that removes a DC component from wave data represented by a two-dimensional image of electromagnetic waves emitted and scattered by a dielectric, and correcting contrast;
A high resolution processing unit for increasing the resolution of wave data processed by the pre-processing unit;
An unnecessary wave suppression processing unit that converts the wave data processed by the high resolution processing unit into data in a frequency space and suppresses unnecessary waves of the wave data converted into the frequency space;
A target detection processing unit that detects a signal according to a target inside the dielectric from wave data in which the unnecessary wave is suppressed by the unnecessary wave suppression processing unit;
The unnecessary wave suppression processing unit Fourier-transforms the wave data that has been subjected to high resolution processing by the high resolution processing unit into data in a frequency space, and among frequency components of wave data in the frequency space, frequency components lower than a threshold value Remove it as an unwanted wave and then inverse Fourier transform it into real space data,
The target detection processing unit calculates a target detection threshold from a band on a frequency corresponding to the threshold and the target azimuth axis, and among signals indicated by wave data, a signal exceeding the target detection threshold is dielectrically detected. An observation device characterized by being detected as a signal corresponding to a target inside the body. The unnecessary wave suppression processing unit calculates an azimuth opening length as a radar device that moves while irradiating the dielectric with an electromagnetic wave, and sets the threshold value using the azimuth opening length. The observation device described. The preprocessing unit removing a direct current component from wave data represented by a two-dimensional image of electromagnetic waves emitted and scattered on a dielectric, and correcting the contrast;
Increasing resolution of wave data processed by the pre-processing unit;
The unnecessary wave suppression processing unit converts the wave data processed by the high resolution processing unit into data of a frequency space, and suppresses unnecessary waves of the wave data converted into the frequency space;
The target detection processing unit detects a signal according to a target inside the dielectric from the wave data in which the unnecessary wave is suppressed by the unnecessary wave suppression processing unit;
The unnecessary wave suppression processing unit Fourier-transforms the wave data that has been subjected to high resolution processing by the high resolution processing unit into data in a frequency space, and among frequency components of wave data in the frequency space, frequency components lower than a threshold value Remove it as an unwanted wave and then inverse Fourier transform it into real space data,
The target detection processing unit calculates a target detection threshold from a band on a frequency corresponding to the threshold and the target azimuth axis, and among signals indicated by wave data, a signal exceeding the target detection threshold is dielectrically detected. An observation method characterized by detecting as a signal according to a target inside the body.

Images