JPH11264869A - Permittivity measuring method and device therefor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make determinable the permittivity of a dielectric by projecting electromagnetic wave to the dielectric, receiving reflection wave for a buried reflector, image-processing obtained two-dimensional plane data and changing parameters corresponding to wave transmission velocities. SOLUTION: The permittivity measuring device 1 is put on the ground or concrete surface being a dielectric and a microwave is emitted from a sensor part 2 toward underground. The reflection wave of an object 6 buried underground is operated for processing with an operation processor 3 and two-dimensional display image data and three-dimensional display image data sliced in the depth direction are indicated on a display 4. Here, the wavelength transmission velocity ν of radar wave as a factor to obtain the burying depth Z0 of the object 6 of an underground radar is obtained from ν=2×Z0 /t (t: return time of reflection wave of the object 6) with the operation processor 3. This wavelength transmission velocity ν is changed as parameter and a wavelength transmission velocity ν where an image is most clearly obtained is selected. The permittivity εr is obtained by ν=c/√ εr (c: light velocity) in the operation processor 3.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a dielectric constant measuring method and a dielectric constant measuring apparatus.

[0002]

2. Description of the Related Art Underground radars are used to impinge on the ground or into concrete or the like by using impulse radar waves, receive reflected waves of the waves, and examine, for example, the structure of a stratum.

When analyzing received data, the depth differs even if the reflection time is the same, if the relative permittivity (easiness of transmission of radio waves) of the substance through which the radar wave passes is different. The dielectric constant of vacuum is 8.854 × 10 ^-12 [Farad / m]
, Which is the smallest value among substances. The relative permittivity is a value indicating how many times the permittivity of another substance is higher than the permittivity of the vacuum, and the relative permittivity of the vacuum is 1.

Therefore, if the relative permittivity in the ground or concrete can be known in advance, an accurate depth can be obtained, but the permittivity in the ground where a variety of substances are present can be accurately determined. Since it is impossible to know, the depth was estimated by assuming an approximate relative permittivity for the actual depth. The relative dielectric constants in this case are concrete (dry state) 4 to 10, concrete (wet state) 10 to 20, asphalt (dry state) 2 to 4, asphalt (wet state) 6 to 12
Was used.

[0005]

However, the range of the estimated value of the relative permittivity is extremely wide as described above, and is only a reference value.

For this reason, there has been a problem in measurement accuracy in the underground radar survey.

An object of the first invention according to the present application is to provide a dielectric constant measuring method capable of accurately knowing a dielectric constant.

An object of a second invention according to the present application is to provide a dielectric constant measuring device capable of accurately measuring a dielectric constant.

[0009]

A dielectric constant measuring method for realizing the object of the first invention according to the present invention is to project an electromagnetic wave into a dielectric and reflect a reflected wave from a reflector embedded in the dielectric. Image processing is performed on the data of the two-dimensional plane including the depth direction obtained by receiving, and changing a parameter corresponding to the wavelength propagation speed of the data, from the parameter when the image of the reflector becomes the sharpest. The dielectric constant of the dielectric is determined.

A dielectric constant measuring apparatus for realizing the object of the second invention according to the present application is a two-dimensional plane including a depth direction obtained by receiving a reflected wave from a reflector embedded in a dielectric. Image display means for processing and displaying data, and a change means for changing a parameter corresponding to the wavelength propagation speed of the data, and changing an image displayed on the image display means based on the parameter, The dielectric constant of the dielectric is obtained from the parameter when the image of the reflector displayed on the image display means becomes sharpest.

[0011]

DESCRIPTION OF THE PREFERRED EMBODIMENTS (First Embodiment) FIG. 1 shows a first embodiment of the present invention.

FIG. 1 is a perspective view of a schematic configuration of a dielectric constant measuring device.

Reference numeral 1 denotes a dielectric constant measuring device which can be carried by holding a handle 1a. The dielectric constant measuring device 1 includes a sensor unit 2, an arithmetic processing unit 3,
The display unit 4 is provided. Dielectric constant measuring device 1
Is placed on the ground or concrete surface, which is a dielectric, projects microwaves from the sensor unit 2 toward the ground, for example, and emits a microwave from an object 6 buried in the ground, which is a dielectric. Two-dimensional (longitudinal section) display image data (referred to as B scan) sliced in the depth direction by processing the reflected wave (referred to as A-scan) in the computing unit 3;
The display unit 4 displays three-dimensional display image data (referred to as C-scan).

The sensor section 2 has a sensor 5 which reciprocates along a direction indicated by an arrow by a reciprocating drive mechanism (not shown).

[0015] In this sensor 5 is very small electromagnetic sensors, an oscillator for outputting an impulse by step waveform in a wide range of 1GH _Z ~10GH _Z, oscillated from the oscillation unit, the reflected wave from the buried object 6 A receiving unit for receiving,
It is composed of a circuit incorporated on a substrate, a battery (not shown), and the like, and outputs data from the receiving unit to the arithmetic processing unit 3.

The arithmetic processing unit 3 inputs the information collected by the receiving unit of the sensor 5 to the data capturing unit via the A / D converter, and stores the information in the memory.

All the data in the memory is corrected by the data correction unit when the scanning of the sensor 5 is completed.

In the present embodiment, the sensor 5 can receive the reflected wave while reciprocating in the direction of the arrow, so that the entirety of the dummy object 6 can be captured with high accuracy. Since the reflected wave from the depth Δd is received when moving a distance of Δx from, the reflected wave arrived through a distance of √ (Δx ² + Δd ² ) is actually received. Perform processing for correction.

The data corrected by the data correction section is:
The background processing unit performs processing for removing surface reflected waves (reflection from the ground surface for the underground). The oscillated one-pulse electromagnetic wave is strongly reflected on the surface of the ground, and the intensity of the reflected wave varies depending on the situation in the ground. Electromagnetic sensor 1
The receiving unit receives the reflected wave with the depth direction in the ground as a time axis and outputs it as detection information.

Therefore, the background processing unit calculates the sum of the received information for each pulse, compares the averaged value with each data, and outputs only different portions.

That is, since the surface reflected waves have almost the same waveform, the surface reflected waves are canceled out and only various reflected waves in the ground are extracted. As a result, the speed of subsequent two-dimensional and three-dimensional image processing is greatly reduced.

All information in a predetermined area processed by the background processing unit is image-processed by an ABI (array beam imaging) processing unit, and is displayed on the display unit 4 in a display state as shown in FIG. .

Here, the wavelength propagation velocity (ν) of the radar wave is a factor for obtaining the burial depth of the object in the underground radar. As shown in FIG. 2, the wavelength propagation velocity (ν) is given by ν = 2 · z ₀ / t from the buried depth (Z ₀ ) of the object and the reciprocating travel time (t) of the reflected wave from the object 6. Given.

Therefore, the wavelength processing speed can be immediately obtained by detecting the round trip time (t) of the object reflected wave in the arithmetic processing unit 3.

The permittivity (ε _r ) is given by ν = c / √ε _r in relation to the wavelength propagation speed. Here, c is the speed of light.

However, since the dielectric constant of soil, which is a dielectric, varies depending on the location of the object to be measured, the dielectric, for example, the dielectric constant in the ground, in data obtained by scanning with a sensor is unknown.

On the other hand, since the obtained data includes the wavelength propagation speed as one of the factors, when the factor corresponding to the wavelength propagation speed is changed as a parameter, the obtained data is obtained at a wavelength propagation speed commensurate with the dielectric constant. The resulting image is the sharpest. That is, the intensity of the reflected wave at the wavelength propagation speed is the strongest.

Therefore, in the present embodiment, the approximate wavelength propagation speed, that is, the approximate permittivity is input to the arithmetic processing unit 3 using a keyboard or the like, and the image on the display unit 4 is observed each time (the iterative image method and the Figure 3)
(B), when it is determined that the image of the object 6 is the sharpest as compared with (a) and (c) of FIG. Is determined as the dielectric constant of the place underground.

In FIG. 3, (a) to (c) show images displayed on the display unit, (d) to (f) show images based on analog information at that time, and (e) shows the most case. The peak is sharp and the reflection level is the highest. In contrast, (d)
Although the peak level is high in (5), the peak is not so sharp, and in (f), the peak level is low.

It should be noted that the judgment that the images with different wavelength propagation velocities (dielectric constants) are the sharpest is made by visual observation, but may be automatically performed.

(Second Embodiment) Measurement of Dielectric Constant of Soil The dielectric constant of soil is unknown because there are various factors that affect the dielectric constant, such as the presence of water and the ratio of soil components being different. It can be said that there is. Therefore, the dielectric constant of soil is usually shown as a range.

In such a case, in this embodiment, the optimum wavelength propagation velocity (ν) is obtained by using the iterative image method.
Is determined, and the dielectric constant of the soil is determined from the wavelength propagation velocity (ν).

(Third Embodiment) Measurement of Dielectric Constant of Reinforced Concrete When the dielectric constant of reinforced concrete is measured by the above-described iterative image method, the position of the reinforcing bar is unknown. Is displayed. Then, the wavelength propagation speed is determined by the iterative image method while observing the display image, and the dielectric constant is obtained.

(Fourth Embodiment) The dielectric constant measuring apparatus shown in FIG. 1 can be used also as an underground radar.
When exploring an underground object with an accurate permittivity that is known by this underground radar, if there is no difference between the permittivity of the target and the surrounding material, for example, in dry sand When a plastic object is buried in the sand, it is easy to search for the plastic object by spraying water on the sand to increase the dielectric constant.

[0035]

According to the dielectric constant measuring method and the measuring apparatus according to the present invention, it is possible to measure the dielectric constant easily and accurately.

[Brief description of the drawings]

FIG. 1 is a schematic diagram of a dielectric constant measuring apparatus according to a first embodiment of the present invention.

FIG. 2 is a schematic diagram showing a measuring method by the dielectric constant measuring device of FIG.

3 (a) to 3 (c) show display states on a display unit in FIG. 1,
(D) to (f) show the analog signals.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Dielectric constant measuring device 2 Sensor part 3 Operation processing part 4 Display part 5 Sensor 6 Object (reflector)

Claims (6)

[Claims] 1. A two-dimensional plane data including a depth direction obtained by projecting an electromagnetic wave into a dielectric and receiving a reflected wave from a reflector buried in the dielectric is subjected to image processing. And changing the parameter corresponding to the wavelength propagation speed of the above, and obtaining the permittivity of the dielectric from the parameter when the image of the reflector becomes sharpest. 2. The dielectric constant measurement method according to claim 1, wherein the reflected wave is received while moving the projection position of the electromagnetic wave in a direction orthogonal to a depth direction. 3. The dielectric constant measuring method according to claim 1, wherein the parameter is a virtual dielectric constant. 4. An image display means for processing and displaying data of a two-dimensional plane including a depth direction obtained by receiving a reflected wave from a reflector embedded in a dielectric, and a wavelength of the data. Means for changing a parameter corresponding to the propagation speed, and changing the image displayed on the image display means based on the parameter, wherein the image of the reflector displayed on the image display means is the sharpest. A dielectric constant of the dielectric from the parameter when the dielectric constant is measured. 5. A sensor unit for projecting a radar wave from a transmitting unit into a dielectric and receiving a reflected wave at a receiving unit, and the sensor unit including a reflected wave from a reflector embedded in the dielectric. Image display means for image-processing and displaying data on a two-dimensional plane including a depth direction, and changing a parameter corresponding to the wavelength propagation speed of the data, and displaying an image to be displayed on the image display means based on the parameter. Changing means for changing the dielectric constant, wherein the dielectric constant of the dielectric is obtained from the parameter when the image of the reflector displayed on the image display is sharpest. 6. A dielectric constant measuring apparatus according to claim 1, wherein said radar means transmits and receives radar waves while moving said sensor means in a direction orthogonal to a radar wave projection direction.