JPH09113630A - Locator for buried object - Google Patents

Abstract

PROBLEM TO BE SOLVED: To eliminate the undesired wave easily at the time of locating various objects, e.g. a pavement, by handling the reflected wave from a boundary face as an undesired wave to be removed in addition to the reflected wave from the surface of pavement. SOLUTION: An electromagnetic pulse wave transmitted toward a pavement through a transmission circuit 1 and a transmission antenna 2 is partially reflected on the surface of pavement 22a and on the boundary face 23a. The remainder reaches a buried object 21 and reflected therefrom before being received by a receiving antenna 3. The received pulse is converted through a receiving circuit 4 into a low frequency band signal. The receiving signal has a waveform containing undesired waves, e.g. the surface reflected wave and boundary surface reflected wave. An undesired wave selection circuit 52 selects a waveform approximate to a receiving undesired wave, as an undesired waveform, from the waveforms stored in an undesired wave storing circuit 51 and delivers the selected undesired wave to an undesired removing circuit 53. The circuit 53 subtracts the undesired waveform selected by the circuit 52 from the output waveform of the circuit 4 to output the receiving waveform only of the buried object 21. Consequently, undesired wave can be removed easily from each object to be located.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a buried object exploration device, and more particularly to a buried object exploration method for exploring buried objects buried in a ground or a structure by a radar system using a pulsed electromagnetic wave having a narrow pulse width. It relates to the device.

[0002]

2. Description of the Related Art A buried object exploration device for exploring buried objects buried in the ground, concrete structures, etc. using a radar system is well known, but briefly explained is pulsed electromagnetic waves on the ground surface. The antennas for transmitting and receiving are transmitted close to each other, and electromagnetic waves with a narrow pulse width are transmitted from the ground surface to the ground. When there is a buried object in the ground, the reflected wave reflected by this buried object is received (hereinafter also referred to as the received wave). Therefore, by displaying the reflected wave from the time of transmission, Information on the position, shape, and strength of the waves can be used to identify the presence or absence of an embedded object, the depth of the embedded object, and what the embedded object is. In addition, as a disclosed technique related to this type of device, a patent application relating to the applicant of the present application, JP-A-1-
297582, "Underground exploration device", Japanese Patent Laid-Open No. 3-1
No. 15806, “Method of measuring thickness in laminated structure” and the like.

When using such a radar system to search for a buried pipe buried under a paved road whose surface is paved, for example, it is well known that the receiving antenna actually receives the signal. The reflected wave is the reflected wave that is received from the pavement surface after the transmitted wave and then reflected from the boundary surface between the pavement and the roadbed below (hereinafter referred to as the back surface reflected wave). Will be received, and then the received wave reflected by the buried object will be received. In this case, if the buried depth of the buried object is deeper than a certain level, the received wave from the buried object can be received as a separate waveform due to the difference in the reception time, and the image can be displayed. If the received wave is displayed as a series of combined waveforms and the pavement is thin, the surface reflected waves are also displayed as a combined series of waveforms, making it easy to identify the buried object. Disappear. Therefore, there is a demand for a technique for removing unnecessary waves such as the above-mentioned front surface reflected wave and back surface reflected wave from the received waveform and independently displaying only the received wave from the buried object.

FIG. 4 is a diagram showing an outline of a conventional buried object exploration device having a structure for removing unnecessary waves, which is disclosed in the above-mentioned Japanese Patent Laid-Open No. 1-297582, and FIG. 5 is obtained by the device shown in FIG. It is a figure which shows the outline of each waveform which is shown, 1 is a transmitting circuit, 2 is a transmitting antenna, 3 is a receiving antenna, 4 is a receiving circuit, 5 is a memory circuit, 6 is an arithmetic circuit, 7 is a display circuit, 20 Is a concrete structure, and 21 is a buried structure.
The pulsed electromagnetic wave transmitted from the transmitting antenna 2 toward the concrete structure 20 is reflected by the buried object 21, is received by the receiving antenna 3, is converted into a low frequency band signal by the receiving circuit 4, and is displayed on the display circuit 7. Is displayed.

The waveform actually received by the receiving antenna 3 is as it is, as described above, in the concrete structure 20.
The surface reflected waves reflected by the surface 20a of the
Since the series of waveforms is as shown by No. 201, the buried object 21 cannot be easily specified as it is. Therefore, in this conventional device, the storage circuit 5 and the arithmetic circuit 6 are provided, and an unnecessary wave that is expected to be received when the storage circuit 5 does not have the buried object 21, that is, a surface as shown by 202 in FIG. The reflected waveform (converted into a low frequency) is stored, and the arithmetic circuit 6 performs an operation of subtracting the stored unnecessary waveform 202 from the waveform 201 actually received by the waveforms to obtain the buried object 2
Only the received waveform 203 from 1 is displayed on the image.

Unwanted waveform 2 stored in the storage circuit 5 in advance
02 is considered to have a uniform waveform at any position when the exploration target is the concrete structure 20,
It suffices to store only one waveform as the unnecessary waveform 202, which is an artificially created pseudo waveform or a monitor waveform obtained by monitoring an appropriate concrete structure, and the arithmetic circuit 6 automatically calculates the unnecessary waveform 202. It is configured to do.

[0007]

In the conventional buried object exploration apparatus as described above, the unnecessary wave can be removed relatively accurately from the concrete structure or the like, but the unnecessary wave can be removed from other parts such as the paved road. There is a problem that it is difficult.

That is, since the relative permittivity of a concrete structure is almost constant in any concrete, and therefore there is no great difference in the surface reflected waves that are generated, it is sufficient to perform the operation of subtracting the same unnecessary waveform. The relative permittivity differs greatly depending on the type and size of gravel used in the material. In addition, as described above, when the back surface reflected wave is also generated from the paved road and the thickness of the pavement is not uniform, the depth of the back surface reflected wave generated differs depending on the survey position, and only one stored waveform is stored. Therefore, it is not possible to uniformly remove unwanted waves on paved roads. Although it is possible to store a plurality of waveforms in the storage circuit 5 in the conventional device, there is no means for determining which of the stored plurality of waveforms matches the actual unwanted wave. Therefore, even in this case, it is difficult to remove unnecessary waves from the paved road.

The present invention has been made to solve the above problems, and an object of the present invention is to provide a buried object exploration apparatus capable of easily removing unnecessary waves in various exploration targets such as paved roads.

[0010]

The buried object exploring apparatus according to the present invention is a buried object which transmits a pulsed electromagnetic wave to an object to be searched and receives a reflected wave to search for an embedded object buried in the object to be searched. In the exploration device, unnecessary wave storage means for storing a plurality of expected unnecessary waves in order to remove unnecessary waves other than the reflected waves from the buried object, the received reflected wave and the unnecessary wave storage means A plurality of waveforms stored in the unnecessary wave selecting means for selecting the waveform closest to the unnecessary wave existing in the received reflected wave from the unnecessary wave storing means, and the unnecessary wave selecting means from the received reflected wave. Equipped with an unnecessary wave removing device that removes unnecessary waves other than the reflected waves from the buried object by performing a calculation to draw the waveform selected by, and the exploration target is a double structure such as a pavement layer of a paved road and a roadbed. , The pavement surface (general In addition to the reflected wave from the double structure surface (called surface reflected wave), the reflected wave from the pavement layer and the roadbed (generally speaking, the double structure back surface) (called the back surface reflected wave) ) Are treated as unnecessary waves to be removed.

Further, in the comparison between the reflected wave received by the unnecessary wave selecting means and the plurality of waveforms stored in the unnecessary wave storage means, the comparison is made only in the portion where the characteristic of the unnecessary wave of each waveform appears. Is characterized by. Further, the comparison between the reflected wave received by the unnecessary wave selection means and the plurality of waveforms stored in the unnecessary wave storage means is made from the reception time point of each waveform to the portion where the characteristic of the back surface reflected wave appears. In particular, when it is assumed that the buried depth of the buried object is shallow, the comparison is performed up to the first cycle of each waveform.

[0012]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a diagram showing a device configuration example of an embodiment of the present invention. In the figure, 1 is a transmission circuit, 2 is a transmission antenna, 3 is a reception antenna, 4 is a reception circuit, 51 is an unnecessary wave storage circuit, and 52. Is an unnecessary wave selection circuit, 53 is an unnecessary wave removal circuit, 7 is a display circuit, 8 is a switch circuit, 21 is a buried object, 22 is a pavement layer, 22a is a pavement surface, 23 is a roadbed,
Reference numeral 23a indicates a boundary surface between the pavement layer 22 and the roadbed 23.

The unnecessary wave storage circuit 51 corresponds to the storage circuit 5 of the conventional device, but is configured to store a plurality of waveforms (converted to low frequencies). The plurality of waveforms stored in the unnecessary wave storage circuit 51 may be artificially created pseudo waveforms, but for accuracy, the switch circuits 8 are operated instead of the pseudo waveforms. The monitor waveform acquired by monitoring is stored.

The undesired wave selection circuit 52 receives the undesired wave from the plurality of waveforms stored in the undesired wave storage circuit 51 from the waveform received by the receiving antenna 3 and converted into the low frequency band signal by the receiving circuit 4. Select a waveform that approximates the unwanted wave of. In selecting this waveform, an appropriate waveform cannot be selected by comparing the waveforms as they are. That is, since the received wave and the like are combined in the received waveform in addition to the unnecessary wave,
This is because if the received waveforms are compared as they are, the wrong waveform may be selected. Therefore, in the present embodiment, the waveforms are selected by comparing only the portions where the features of the unwanted waveforms appear between the waveforms.

FIG. 2 is a diagram for explaining unnecessary waves on the paved road. In the figure, reference numeral 204 is the paved surface 22.
a surface reflected wave from a, 205 a back surface reflected wave from the boundary surface 23a, 206 a surface reflected wave 204 and a back surface reflected wave 205
And represent the unwanted waves that are combined and received. When the pavement is thin, unnecessary waves such as 206 in FIG. 2 are received, but the front surface reflected wave 204 and the back surface reflected wave 205 are S in FIG.
The feature is that they are combined in the first cycle indicated by 1. Further, when the buried object 21 has a shallow burial depth, the influence of the received wave from the buried object 21 appears from the second cycle.

Therefore, in the unnecessary wave selection circuit 52 of the present embodiment, when selecting an unnecessary waveform, the first cycle of the waveform received via the receiving antenna 3 and the receiving circuit 4 and the unnecessary wave storage circuit 51 are stored. The plurality of waveforms are compared with the first cycle, and the waveform having the smallest difference is selected.
By performing such a selection method, the buried object 21
An appropriate waveform can be selected in a short time without causing an error due to the influence of the received waveform from.

The unnecessary wave removing circuit 53 is a circuit corresponding to the conventional arithmetic circuit 6, and performs an operation of subtracting the unnecessary wave selected by the unnecessary wave selecting circuit 52 from the received waveform by the waveforms, and then from the buried object 21. Only the received waveform of is output. The selection of the unwanted waveform to be removed here is usually 1 in one measurement.
However, if the survey range is wide or if the pavement condition is not constant, the procedure is performed once for each reception operation.

Next, the operation of the apparatus shown in FIG. 1 will be described. Part of the pulsed electromagnetic wave transmitted toward the paved road via the transmission circuit 1 and the transmission antenna 2 is part of the paved surface 2
It is reflected by 2a and the boundary surface 23a, further reaches the embedded object 21, is reflected by the embedded object 21, is received by the receiving antenna 3, and is converted into a low frequency band signal by the receiving circuit 4. The waveform actually received is a waveform including an unnecessary wave such as a front surface reflected wave and a back surface (boundary surface) reflected wave as shown by 207 in FIG. 3, and the receiving circuit removes the unnecessary wave from the waveform 207. The output from 4 is input to the unnecessary wave selection circuit 52 and the unnecessary wave removal circuit 53.

The unnecessary wave selection circuit 52 selects a waveform similar to the actually received unnecessary wave as the unnecessary waveform 208 from the waveforms stored in the unnecessary wave storage circuit 51 as described above, and this unnecessary waveform 208 Unnecessary waveform removing circuit 53
To the output circuit 207 from the receiving circuit 4 and subtracting the unnecessary waveform 208 to calculate the difference between the waveforms to obtain the desired received waveform 209, which is output to the display circuit 7 and displayed on the display circuit.

In the above-described embodiment, only the case where the selection of the unnecessary waveform is compared in the first period is described. However, the pavement layer is thick, and the surface reflected wave and the back surface reflected wave are combined in the first period. In such a case, the comparison is made up to the period when the characteristic of the back surface reflected wave appears. Further, in the above-described embodiment, the exploration of the buried object buried under the paved road has been described, but it goes without saying that the buried object buried in the laminated structure or the like can be similarly searched.

[0021]

As described above, the buried object exploration apparatus of the present invention can easily remove different unnecessary waves in various objects to be inspected, and can accurately inspect the buried object. In particular, there is an effect that it is possible to accurately perform an exploration for an object buried under a double structure such as under a paved road and having a shallow burial depth.

[Brief description of the drawings]

FIG. 1 is a diagram showing a device configuration of an embodiment of the present invention.

FIG. 2 is a diagram for explaining an outline of unnecessary waves on a paved road.

FIG. 3 is a diagram showing an outline of each waveform obtained by the device shown in FIG.

FIG. 4 is a diagram showing an example of a conventional device of this type.

5 is a diagram showing an outline of each waveform obtained by the device shown in FIG.

[Explanation of symbols]

 1 transmitting circuit 2 transmitting antenna 3 receiving antenna 4 receiving circuit 7 display circuit 8 switch circuit 21 buried object 22 pavement layer 23 roadbed 51 unwanted wave memory circuit 52 unwanted wave selecting circuit 53 unwanted wave removing circuit 204 front reflected wave 205 back reflected wave 206 Unwanted wave 207 Received waveform 208 Unwanted waveform 209 Desired received waveform

Claims (3)

[Claims] 1. An embedded object exploration device that transmits a pulsed electromagnetic wave to an object to be searched and receives a reflected wave to search for an embedded object buried in the object to be searched, except for reflected waves from the object. In order to remove the waves, the unwanted wave storage means for storing a plurality of expected unwanted waves in the waveform is compared with the received reflected wave and the multiple waveforms stored in the unwanted wave storage means, and the received reflection is received. The unnecessary wave selecting means for selecting the waveform closest to the actual unnecessary wave from the unnecessary wave storing means, and the operation of subtracting the waveform selected by the unnecessary wave selecting means from the received reflected wave are performed from the buried object. If the exploration target is a double structure such as a pavement layer and a roadbed of a paved road, the paved surface (generally referred to as a double structure Reflected wave from surface) In addition to the waves), the reflected waves from the pavement layer and the roadbed (generally speaking, the back surface of the double structure) (called back surface reflected waves) are treated as unnecessary waves to be removed. The buried object exploration device. 2. The comparison between the reflected wave received by the unwanted wave selecting means and the plurality of waveforms stored in the unwanted wave storage means should be made only in the portion where the characteristics of the unwanted wave of each waveform appear. The buried object exploration apparatus according to claim 1, wherein: 3. The comparison between the reflected wave received by the unnecessary wave selecting means and the plurality of waveforms stored in the unnecessary wave storage means is a portion where the characteristic of the back surface reflected wave appears from the reception time point of each waveform. 2. The buried object exploration apparatus according to claim 1, wherein the buried object exploration device is compared up to the first cycle of each of the waveforms, especially when it is assumed that the buried object is buried shallowly. .