JPH07260462A - Method and apparatus for formation of space standing waves as well as microwave measuring apparatus using the space standing wave formation apparatus - Google Patents

Abstract

PURPOSE:To obtain a space standing wave formation apparatus in which the S/N ratio and the phase resolution of space standing waves can be enhanced. CONSTITUTION:The space standing wave formation apparatus is provided with a waveguide 16 which transmits millimeter waves and on which a slot antenna 18 has been installed, with a wave-transmitting-and-receiving horn 17, for a sqaure resonator, which is attached to the waveguide 16 and which has a first reflecting face 17a installed around the antenna 18 and with a reflecting horn 22, for the square resonator, which is arranged in the radiation direction of electromagnetic waves of the horn 17 so as to have the central axis line C of the antenna 18 in common and which has a second reflecting face 22a faced with the first reflecting face 17a. Then, the distance between both reflecting faces is set at a distance of [(lambda/2)Xn] [ where lambdarepresents the wavelength of the electromagnetic waves and (n) represents a positive integer]. Thereby, a specific wavelength which is resonated with the wave-transmitting- and-receiving horn 17 and the reflecting horn 22 out of the millimeter waves is reflected repeatedly between both reflecting faces, the energy of space standing waves at the specific wavelength is stored, and the amplitude of the space standing waves is amplified.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and a device for forming a spatial standing wave of an electromagnetic wave having a wavelength of a microwave, particularly a millimeter wave, and a thickness of a material to be inspected by using the spatial standing wave forming device. The present invention relates to a microwave measuring device that detects a measurement target such as a dielectric constant.

[0002]

2. Description of the Related Art A spatial standing wave is a standing wave formed by mutual interference between a traveling wave and a reflected wave in the space, and the space in which the standing wave interferes with communication, for example, is generally
Such spatial standing waves are considered unfavorable. However, the present applicant has developed a device for measuring the thickness of a dielectric material by utilizing such a standing wave treated as an obstacle, and has already filed as Japanese Patent Application No. 3-340538.

In the device according to the present application, a structure for forming a spatial standing wave is such that an electromagnetic wave transmitter 1 for transmitting a millimeter wave electromagnetic wave and an electromagnetic wave sensor 2 for receiving the electromagnetic wave are arranged side by side as shown in FIG. The metal reflector 4 is arranged in front of them with a space for disposing the test material 3 that allows the test material 3 to be taken in and out. Further, the electromagnetic wave transmitter 1 has a taper type transmission horn 1a whose cross-sectional area gradually increases toward the reflection plate 4, and the electromagnetic wave sensor 2 also has a taper-shaped receiving horn whose cross-sectional area gradually increases toward the reflection plate 4. It has a wave horn 2a.

In this structure, the millimeter wave radiated from the wave transmission horn 1a of the electromagnetic wave transmitter 1 toward the reflection plate 4 is reflected by the reflection plate 4 and received by the electromagnetic wave sensor 2 through the reception horn 2a. Therefore, the electromagnetic wave transmitter 1
Due to the interference of the plane wave traveling wave from the reflector 4 to the reflector 4 and the plane wave reflected wave from the reflector 4 to the electromagnetic wave sensor 2, a spatial standing wave is generated between the sending sensors 1 and 2 and the reflector 4. Is formed.

When a material 3 to be inspected, such as a plate-shaped dielectric, is inserted parallel to the wave front of the standing wave in the space standing wave thus formed in the space, the material of the material 3 to be inspected Since the propagation velocity of the electromagnetic wave is slowed by the molecules of, the phase of the spatial standing wave is proportionally shifted. Therefore, the device according to Japanese Patent Application No. 3-340538 detects the shift amount of the phase, and based on the detected shift amount and the known permittivity of the test material 3, The thickness of the material 3 to be inspected is calculated.

[0006]

The phase shift amount is detected by detecting the position of the antinode of the spatial standing wave based on the measurement of the electric field energy (standing wave power) of the formed spatial standing wave. Is done. However, in the conventional configuration, since the mutual interference between the traveling wave and the reflected wave forming the spatial standing wave is only once, the energy accumulation of the spatial standing wave is small. In other words, the amplitude of the spatial standing wave is small.

Further, in the conventional structure, since the electromagnetic wave transmitters / sensors 1 and 2 are provided in close proximity to each other, when these and the reflection plate 4 approach each other at a short distance, the electromagnetic wave transmitter / sensors. Due to the parallax between the first and second transmitting horns 1a and the receiving horns 2a, the phase of the spatial standing wave in the distance direction tends to be blurred.

Moreover, in addition to various harmonics and harmonics being superposed on the electromagnetic wave radiated from the electromagnetic wave transmitter 1, the wave transmission horn 1a of the electromagnetic wave transmitters / sensors 1 and 2 is added.
Since diffracted waves are generated at the openings of the receiving horn 2a and the receiving horn 2a and are superposed on the spatial standing wave, the spatial standing wave is easily distorted.

Moreover, the electromagnetic wave sensor 2 having the taper type receiving horn 2a has a poor conversion efficiency of the electric field energy of the spatial standing wave of the receiving horn 2a. For these reasons, in the conventional configuration, the S / N ratio of the spatial standing wave to be formed is low and the phase resolution is not good (by the way, in the conventional configuration, the spatial standing wave due to the electromagnetic wave having a wavelength of 6 millimeter waves is generated. Phase resolution is about 50 μm when converted to distance
Was the limit, and could not be less than that. ), And accordingly, there is a problem that the phase shift amount cannot be detected accurately.

The first object of the present invention is to obtain the S / N of a spatial standing wave.
An object of the present invention is to obtain a spatial standing wave forming method and apparatus capable of improving the ratio and phase resolution. A second object of the present invention is to obtain a microwave measuring device capable of detecting a measurement target of a test material with high accuracy by using a spatial standing wave forming device capable of achieving the first object. .

[0011]

In order to achieve the first object, the spatial standing wave forming method according to claim 1 of the present invention is provided in a waveguide for transmitting an electromagnetic wave having a microwave wavelength. An electromagnetic wave radiated from the antenna is defined by a reflecting surface around the slot antenna and a reflector provided in the electromagnetic wave radiating direction of the antenna so as to face the reflecting surface substantially orthogonal to the central axis of the antenna. It is characterized in that a spatial standing wave is created by repeatedly reflecting between the reflecting surface and the reflector.

Similarly, in order to achieve the first object,
A spatial standing wave forming device according to claim 2 of the present invention transmits an electromagnetic wave having a wavelength of a microwave, and a waveguide provided with a slot antenna at an intermediate portion in an axial direction, and attached to the waveguide. A first reflecting surface that is provided around the slot antenna and is substantially orthogonal to the central axis of the antenna, and a cross-sectional shape in which one end is open and the other end is continuous with the first reflecting surface and is orthogonal to the central axis. The first is constant
A cavity-resonance type wave transmitting / receiving horn having a cylindrical portion, and a reflection having a second reflecting surface which is arranged in the electromagnetic wave radiation direction of the wave transmitting / receiving horn and which is substantially orthogonal to the central axis line and faces the first reflecting surface. It is equipped with a body.

Further, in order to achieve the second object, a microwave measuring apparatus according to a third aspect of the present invention is a waveguide in which a slot antenna is provided at an axially intermediate portion, and one end of the waveguide. An electromagnetic wave transmitter that is connected to the section to supply an electromagnetic wave having a microwave wavelength to the waveguide, a first reflecting surface that is provided around the slot antenna and is orthogonal to the central axis of the antenna, and one end is open. And a cavity resonance type transmission / reception horn having a first cylindrical portion whose other end is connected to the first reflection surface and has a constant cross-section substantially orthogonal to the central axis, and between the transmission / reception horn. A reflector having a second reflecting surface, which is arranged in the electromagnetic wave radiation direction of the wave transmitting / receiving horn with a space for arranging a material to be inspected, and is provided substantially orthogonal to the central axis, and the other end of the waveguide. The electromagnetic wave sensor connected to the A wave tube, the transmission / reception horn, the reflector, the electromagnetic wave transmitter, and the electromagnetic wave sensor, a carriage, and a carriage moving means for moving the carriage back and forth along the central axis. Sensor for detecting the amount of movement of the space, a controller for detecting an antinode or a node of the spatial standing wave formed between the first and second reflectors based on the output from the electromagnetic wave sensor, and this control From the output of the section and the output of the distance sensor to find the amount of phase shift of the space standing wave with the presence or absence of the test material to the test material disposition space,
A calculation unit for calculating a measurement target of the test material based on the shift amount is provided.

[0014]

In the spatial standing wave forming method according to the first aspect,
The electromagnetic wave is radiated from a slot antenna provided in a waveguide that transmits an electromagnetic wave having a microwave wavelength, and the electromagnetic wave (traveling wave) is reflected toward the slot antenna by a reflector provided in the radiation direction of the slot antenna. Further, the electromagnetic wave (reflected wave) reflected by the reflector is reflected as a traveling wave toward the reflector by the reflection surface around the slot antenna. In this way, the electromagnetic waves radiated from the antenna are repeatedly reflected between the reflecting surface and the reflector to cause mutual interference, thereby forming a spatial standing wave in the space between the reflecting surface and the reflector. You can Therefore, the spatial standing wave is amplified by the repeated mutual interference, and the amplitude thereof can be increased.

In the structure of the spatial standing wave forming device according to the second aspect, the slot antenna of the waveguide leaks an electromagnetic wave having a microwave wavelength transmitted in the waveguide to the outside.
The transmitting / receiving horn resonates the standing wave of the target wavelength among the electromagnetic waves radiated from the slot antenna, leaks other frequency components, and gives the directivity toward the reflector in the free space as a traveling wave. It radiates and its first reflecting surface reflects the electromagnetic waves incident on it. The second reflecting surface of the reflector reflects the electromagnetic wave incident on the second reflecting surface as a reflected wave toward the transmitting / receiving horn.

Therefore, the electromagnetic waves radiated from the slot antenna can be repeatedly reciprocated with the first and second reflecting surfaces as nodes, and the number of times of mutual interference between the traveling wave and the reflected wave can be increased. The amplitude of the spatial standing wave standing between the faces can be increased. Further, it is possible to select only a standing wave having a target wavelength for which a spatial standing wave is desired to be generated by the resonance.

Moreover, since the transmission / reception horn is used for both transmission and reception of electromagnetic waves, there is no parallax in transmission / reception, and the transmission horn and the reception horn are arranged side by side to generate a diffracted wave at the opening of the horn. It can be reduced to half compared to the one.

Further, since the first tubular portion of the transmitting / receiving horn does not change in its cross-sectional shape, the efficiency of converting the electric field energy of the spatial standing wave into the receiving power is higher than that of the tapered one. As described above, according to the spatial standing wave forming device of the second aspect, only a specific wavelength can be selected by the resonance in the spatial resonance type transmission / reception horn, and other wavelengths are less likely to be superposed on it. Moreover, the S / N of the spatial standing wave can be formed by forming the spatial standing wave with large amplitude without parallax.
The ratio and phase resolution can be improved.

In the microwave measuring apparatus according to the third aspect, the waveguide, the transmitting / receiving horn, and the reflector constitute the spatial standing wave forming apparatus according to the second aspect, and one end of the waveguide. From the electromagnetic wave of the microwave wavelength supplied by the electromagnetic wave transmitter to form a spatial standing wave of large amplitude by selecting a specific wavelength, and the electromagnetic wave sensor receives the spatial standing wave, Detects standing wave power.

Further, the carriage moving means moves the carriage on which the space standing wave forming device is mounted, and the distance sensor detects the movement amount of the carriage. The control unit detects the antinode or node of the spatial standing wave based on the output from the electromagnetic wave sensor,
The output of the distance sensor at the time of this detection is read. The calculation unit determines, from the outputs of the control unit and the output of the distance sensor (the antinodes of the spatial standing wave or the positions of nodes, etc.), the antinodes of the spatial standing wave depending on the presence or absence of the test material in the spatial standing wave or The shift amount of the position of the node or the like, that is, the shift amount of the phase of the spatial standing wave is detected, and the measurement target of the test material is calculated based on this shift amount.

For example, in the case of measuring the thickness of the dielectric material as the material to be inspected, a calculation according to a predetermined formula is performed by using the deviation amount and the permittivity known in advance in the material to be inspected as parameters, and The thickness of the test material is calculated and the measurement is completed.

In the measurement by such a microwave measuring device, the phase shift can be easily detected with the improvement of the S / N ratio and the phase resolution of the spatial standing wave, as described above, and therefore, the test object can be detected. The measurement target of the material can be detected with high accuracy.

[0023]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT An embodiment of the present invention will be described below with reference to FIGS. FIG. 1 is a diagram showing the structure of a microwave measuring apparatus for measuring the thickness of a dielectric material according to an embodiment of the present invention, in which a carriage indicated by 11 slides a guide (not shown). It is movably installed. The carriage 11 is adapted to be moved in the AB direction in FIG. 1 by the carriage moving means 12.

The carriage moving means 12 includes a ball screw (not shown) which is engaged with the carriage 11 and extends in the moving direction of the carriage 11, and a stepping motor or DC servo connected to one end of the screw. It is formed by including a drive source such as a motor. Carriage 11 by carriage moving means 12
The moving amount is about 0.5 mm to several tens of mm, and the moving amount is a distance sensor 13 such as an operating transformer or a magnet scale.
It is detected by.

An electromagnetic wave transmitter 14, an electromagnetic wave sensor 15, a waveguide 16, and a cavity resonance type transmitting / receiving horn 17 are mounted on the carriage 11. The electromagnetic wave transmitter 14 is
It is a millimeter wave generator that generates and transmits microwaves, especially electromagnetic waves having a wavelength of 1 to 10 mm, that is, millimeter waves. The electromagnetic wave transmitter 14 is connected to one end of a waveguide 16. The use of millimeter waves is effective for making a small measuring device because its wavelength is small. The electromagnetic wave sensor 15 is composed of an ultra-sensitive electric power meter, and is connected to the other end opening of the waveguide 16.

The waveguide 16 is a tube made of a metal conductor, and its cross section has a rectangular cross section or a rectangular cross section as shown in FIG. A slot antenna 18 for radiating a millimeter wave electromagnetic wave transmitted through the waveguide 16 to the outside of the waveguide 16 is provided on one side wall of an axially intermediate portion of the rectangular waveguide 16. . The antenna 18 is made of a slit as shown in FIG. 3, and its length is half the wavelength λ of the millimeter wave electromagnetic wave.

As shown in FIG. 1, a circulator 19 made of a ferrite magnet is built in the waveguide 16 so as to face the slot antenna 18 at an axially intermediate portion. The circulator 19 has a circular shape in plan view, and its magnetic force causes an electromagnetic wave supplied from the electromagnetic wave transmitter 14 and transmitted in the waveguide 16 to the electromagnetic wave sensor 15 as shown by a dotted arrow in FIG. In order to direct the electromagnetic waves incident from the outside through the slot antenna 18 as described later through the inside of the waveguide 16 to the electromagnetic wave sensor 15 as shown by the chain double-dashed line in FIG. It is provided in.

As shown in FIGS. 1 and 3, the transmission / reception horn 17 for giving directivity to electromagnetic waves shares the central axis line of the slot antenna 18 (shown by the one-dot chain line C in FIG. 1) and shares the antenna 18 therewith. Is attached to one side wall of the waveguide 16. The horn 17 is made of a metal conductor and has a first reflecting surface 17a and a first tubular portion 17b. The first reflecting surface 17a is provided substantially orthogonal to the central axis A, for example, in parallel with the wavefront of a plane wave-like traveling wave radiated from the slot antenna 18, and the slot antenna 18 is opened at the center thereof. There is. Therefore, the first reflecting surface 17 a is provided around the slot antenna 18 so as to surround the antenna 18.

The first reflecting surface 17a may be inclined with respect to the central axis C (the propagation axis of the electromagnetic wave) within a range of 90 ° to ± 10 °, and even in such an intersecting state, it is "substantially orthogonal". Be included in the concept. Then, even at these intersecting angles of ± 10 °, a spatial standing wave described later can be established by mutual interference between the new light wave and the reflected wave, which was confirmed by the experiment according to the present invention.

The first tubular portion 17b has a tubular structure in which one end is opened and the other end is provided, for example, integrally and continuously with the first reflecting surface 17a, and the cross-sectional shape orthogonal to the central axis C is constant. Is doing. Therefore, due to the first cylindrical portion 17b, the wave transmitting / receiving horn 17 has a not-tapered one-end open type cylindrical structure. The cross section of the first tubular portion 17b may be square, rectangular, circular, oval or the like, but in particular, in the present embodiment, in order to secure a larger first reflecting surface 17a under the same width or diameter condition, FIG.
It has a square cross section as shown in FIG.

The length D of the first cylindrical portion 17b extending along the central axis C is set to a length that resonates with the wavelength to be selected and used, for example, a length approximate to one side of a cavity resonator having a rectangular cross section. is there. The resonance wavelength is preferably the fundamental frequency of the electromagnetic wave. This is because the level of the fundamental frequency is remarkably large as compared with the levels of the harmonics and the harmonics, and by making it resonate, it is possible to greatly contribute to the improvement of the S / N ratio.

The transmitting / receiving horn 17 having the above-mentioned configuration
Is used as an electromagnetic wave horn that radiates an electromagnetic wave emitted from the slot antenna 18 and an electromagnetic wave horn that receives a reflected electromagnetic wave, and is also used as a cavity resonator.

As shown in FIG. 1, a reflection horn 22 as a reflector is arranged outside the pedestal 11 in the cavity resonance type electromagnetic wave radiation direction of the transmission / reception horn 17 sharing the central axis C. , The reflection horn 22 and the transmission / reception horn 1
A space for disposing the material to be inspected 23 is secured between the material and the material 7 to allow the material 23 to be inspected. The reflection horn 22 for increasing the directivity of electromagnetic waves includes the waveguide 16 and the transmission / reception horn 1.
Together with 7, they form a device for forming a spatial standing wave.

The reflection horn 22 is made of a metal conductor,
It has the 2nd reflective surface 22a and the 2nd cylinder part 22b. The second reflecting surface 22a is provided substantially orthogonal to the central axis C and parallel to the wavefront of the plane wave traveling wave radiated from the slot antenna 18, for example. This second reflecting surface 22a is also ± 90 ° with respect to the central axis C (the propagation axis of electromagnetic waves).
It may be inclined at an angle of 10 °, and such an intersecting state is included in the concept of "substantially orthogonal". Then, even at these intersecting angles of ± 10 °, a spatial standing wave described later can be established by mutual interference between the new light wave and the reflected wave, which was confirmed by the experiment according to the present invention.

The second tubular portion 22b is provided with one end on the side facing the wave transmitting / receiving horn 17 being open and the other end being integrally connected to the second reflecting surface 22b, for example, and being orthogonal to the central axis C. It has a tubular structure with a constant cross-sectional shape. Therefore, the reflection horn 22 has a non-tapered one-end open tubular structure by the second tubular portion 22b. The cross section of the second tubular portion 22b has a square shape, a rectangular shape,
Although it may be circular or elliptical, in this embodiment, in particular, a square cross section is provided as shown in FIG. 4 in order to secure a larger second reflecting surface 22a under the same width or diameter conditions.

The length E of the second tubular portion 22b extending along the central axis C is set to a length that resonates at a wavelength to be selected and used, for example, a length approximate to one side of a cavity resonator having a rectangular cross section. There is. The resonance wavelength is preferably the fundamental frequency of the electromagnetic wave. This is because the level of the fundamental frequency is much higher than the levels of harmonics and harmonics,
By making it resonate, it can greatly contribute to the improvement of the S / N ratio.

The reflection horn 22 having the above structure is used as a reflector for reflecting the electromagnetic wave radiated from the slot antenna 18 and also as a cavity resonator. The reflection horn 22 is embedded in an electromagnetic wave absorber 27 made of ferrite as shown in FIG. 1, and the surface of the absorber 27 and the opening end of the reflection horn 22 are flush with each other.

Particularly, in the structure in which the electromagnetic wave absorber 27 surrounds the periphery of the reflector 22, it is possible to reduce disturbance noise from being mixed by the absorbing action, form a sharp spatial standing wave, and improve the measurement accuracy. It is effective for

The distance F between the first and second reflecting surfaces 17a and 22a facing each other of the spatial standing wave forming device (see FIG. 1).
Is set to [(λ / 2) × n] (where λ is the wavelength of the electromagnetic wave and n is a positive integer). This distance F is a condition for establishing a sharp and optimal spatial standing wave between the two reflecting surfaces 17a and 22a, and is determined in consideration of the phase shift of the spatial standing wave according to the material 23 to be inspected. In consideration of the space, it is set to about 200 mm, for example.

Further, in FIG. 1, reference numeral 24 is a control unit stored in the control panel 25, which gives a control output thereof to the drive source of the carriage moving means 12 to control the drive thereof. Further, the control unit 24 controls the first and second reflecting surfaces 17a, 22 based on the output of the electromagnetic wave sensor 15 input thereto.
This is to find the antinode of the spatial standing wave formed between a.

To detect the antinode of the spatial standing wave, the power value of the half cycle of the voltage waveform (see FIG. 5) output from the electromagnetic wave sensor 15 is read into the memory over time, and the maximum power value is determined. Do by asking. That is, to explain one specific example, in FIG. 5, the power value v2 at s1 and the power value v3 at s2 thereafter are compared by a comparator, and the larger power value v3 is updated and stored in the memory. After that, the power value v4 at s3 is further updated and stored in the comparator by the power value v4.
Compared with v3, the larger power value v3 is updated and stored in the memory, and the same procedure is repeated until sn time to compare the power values. As a result, the last remaining power value in the memory is the maximum power value of the output voltage waveform, and the position of the antinode G (see FIG. 1) of the spatial standing wave can be detected by the above processing.

Instead of the antinode G, the node H of the spatial standing wave is obtained.
(See FIG. 1) position may be detected, in which case,
After detecting the minimum voltage value and the maximum voltage value by the same procedure as described above, the position of the node of the spatial standing wave is detected by calculating the electric power value of the half of the total value of these values by arithmetic processing. it can. Therefore, the calculation process is easier to detect the belly G, and the configuration of the control unit 24 can be simplified accordingly.

The control panel 25 stores therein an arithmetic unit 26 to which the output of the control unit 24 is input (thus, the output of the distance sensor 13 is also supplied via the control unit 24). The calculation unit 26 shifts the position of the antinode G or the node H of the spatial standing wave when the test material 23 is inserted into the spatial standing wave, that is, the phase shift amount ΔZ ( Figure 1
(See reference) and calculated phase shift amount Δ
Based on Z and the permittivity ε which is known in advance for the test material 23 and has already been input to the calculation unit 26, the measurement target of the test material 23, in the case of the present embodiment, the test material 23. The thickness t is calculated.

The control unit 24 and the arithmetic unit 26 are formed by a microcomputer, and an external recording device (not shown) such as an XY plotter or CRT is connected to the output end of the arithmetic unit 26. The measurement result is displayed on.

The amount of phase shift ΔZ of the spatial standing wave is calculated by the distance at the time of detecting the antinode G of the spatial standing wave W (see the dotted line and the chain double-dashed line in FIG. 1) in which the material 23 to be tested is not inserted. Absolute between the first output value of the sensor 13 and the second output value of the distance sensor 13 at the time of detection of the antinode G ′ that is displaced due to the insertion of the material 23 to be tested into the same space standing wave W. It is executed by an arithmetic process of finding a value. The thickness t of the test material 23 is calculated by the equation (t = ΔZ / ε ^1/2 ), where ΔZ is the phase shift amount of the spatial standing wave and ε is the test value. The permittivity of material 23 and ^1/2 have the same contents as the root, which is a mathematical root symbol.

Next, the measurement sequence will be described using the microwave measuring device for measuring the thickness of the dielectric material, which is provided with the above-mentioned spatial standing wave forming device. When the measurement apparatus is operated, the electromagnetic wave having the wavelength of the millimeter-mail wave generated by the electromagnetic wave transmitter 14 is supplied to the waveguide 16. And this waveguide 16
The electromagnetic wave transmitted by the circulator 19 has its wave direction changed by the circulator 19 and travels like a plane wave (dotted line w1 in FIG. 1) from the slot antenna 18 to the outside of the waveguide 16.
), And this electromagnetic wave is transmitted and received by the transmitting and receiving horn 17.
Gives a directivity to the reflection horn 22.

The traveling wave w1 (planar wave-shaped electromagnetic wave) that has entered the reflection horn 22 is provided with the second reflection surface 22 of the reflection horn 22 that is provided so as to intersect the traveling direction at a right angle.
It is reflected at b.

That is, the electric field energy of the traveling wave W1 is absorbed by the movement of free electrons on the surface of the metal forming the second reflecting surface 22b, and the electric field energy on the surface of the second reflecting surface 22b becomes zero. Therefore, this second reflecting surface 22
The traveling wave W1 is reflected by the absorbed electric field energy with b as a node, and the traveling horn 22
Is given a directivity toward the transmitting / receiving horn 17.

Then, a reflected wave (a plane wave-shaped electromagnetic wave, which is a two-chain chain line w2 in FIG. 1) that has entered the transmission / reception horn 17.
A part of the second reference surface 22a is formed by the first reflection surface 17a of the transmission / reception horn 17 provided so as to intersect the traveling direction of the reflected wave w2 at a right angle, in the same manner as the reflection at the second reflection surface 22a. The one reflection surface 17a is reflected as a node, and directivity is given toward the reflection horn 22.

Therefore, due to the mutual interference between the traveling wave W1 and the reflected wave W2 of the plane wave electromagnetic wave radiated from the slot antenna 18 due to the operation of this measuring apparatus, [(λ / 2)
The spatial standing wave W is formed in the space between the first and second reflection surfaces 17a and 22a of both horns 17 and 22 which are arranged so as to satisfy the expression [xn]. Then, since the electromagnetic wave repeats reciprocating with the first and second reflecting surfaces 17a and 22a as nodes,
Mutual interference between the traveling wave W1 and the reflected wave W2 is repeated, and a spatial standing wave W having a large amplitude can be formed by the amplification action caused by the mutual interference.
That is, the electric field energy of electromagnetic waves can be stored in the form of standing wave power.

In the formation of the spatial standing wave, the transmission / reception horn 17 and the reflection horn 22 have a standing wave having a target wavelength of electromagnetic waves giving directivity, that is, a standing wave having a fundamental frequency having a large power level. Since it resonates and leaks other frequency components, the above-described amplification can be performed only for electromagnetic waves of a specific frequency component for which a spatial standing wave is desired to be generated. Thereby, a larger amplitude can be given to the spatial standing wave W, and the interference of the harmonic wave and the harmonic wave with the standing wave W can be reduced.

Moreover, since the transmission / reception horn 17 is used for both transmission and reception of electromagnetic waves, it is possible to eliminate the parallax in the transmission / reception wave.
It is possible to reduce the occurrence of blurring in the phase of the spatial standing wave W in the distance direction even when the spatial standing wave W is approached up to mm.

Further, as described above, since the transmitting / receiving horn 17 also serves to transmit and receive electromagnetic waves, generation of a diffracted wave at the opening of the horn due to transmission and reception is prevented by the transmitting horn. Since the horn and the horn can be suppressed to half as compared with those provided in parallel, the distortion of the spatial standing wave due to the superposition of the diffraction wave on the spatial standing wave W can be reduced.

In addition, the first of the transmitting / receiving horns 17 and 22,
Since there is no change in the cross-sectional shape of the second cylindrical portions 17b and 22b, the conversion efficiency of the electric field energy of the spatial standing wave W into the received power is higher than that of the tapered one.

As described above, it is possible to increase the amplitude of the spatial standing wave W by selecting only an electromagnetic wave of a specific wavelength, amplifying it, and having little overlap of other wavelengths on it and no parallax. Therefore, the S / N ratio and the phase resolution of the spatial standing wave W can be improved. By the way, in the above configuration, 6
The spatial resolution of the spatial standing wave W formed by the electromagnetic wave of the millimeter wave (50 GHz) wavelength is 4.3 mm ² , and the phase detection resolution is 0.12 degrees (the position resolution is 1 μm converted into the distance). I was able to get it.

A part of the spatial standing wave W that has entered the transmitting / receiving horn 17 flows into the waveguide 16 from the slot antenna 18, is directed by the circulator 19 and is transmitted to the electromagnetic wave sensor 15. The sensor 15 detects the electric field energy of the spatial standing wave W.

Next, in such a state where the spatial standing wave W is formed, the control section 24 operates the carriage moving means 12 to move the carriage 11 to the reflection horn 22 side, while the electromagnetic wave sensor 15 is being operated. Read the received power of. Therefore, the antinode G of the spatial standing wave is detected based on the change in the received power of the electromagnetic wave sensor 15 as described above, and the output of the distance sensor 13 is read into the control unit 24 at this detection time, It is stored in the calculation unit 26 as a measurement reference.

After that, the material to be tested 23 made of a dielectric material such as a plastic film whose permittivity ε is known in advance.
Are inserted parallel to the wavefront of the spatial standing wave W. Then, the molecules of the material 23 to be tested slow down the propagation speed of the electromagnetic wave, and the phase of the spatial standing wave W is shifted in proportion to the delay. This phase shift amount is indicated by ΔZ in FIG. At this time, the phase shift amount ΔZ, the thickness t of the test material 23, and the dielectric constant ε are ΔZ = t · root ε, that is, ΔZ = t.
・ The relationship is represented by the ε ^1/2 formula.

In this state, the gantry moving means 12 is operated to move the gantry 11 to the reflection horn 22 side, and based on the received power of the electromagnetic wave sensor 15 at that time, the control section 24.
Detects the antinode G ′ of the spatial standing wave W that has been displaced (shifted), and reads the output of the distance sensor 13 at the time of detection.

Then, the computing unit 26 obtains the absolute values of these based on the output (position data of the antinodes G and G ') from the distance sensor 13 obtained by the above detection, and shifts the phase of the spatial standing wave W. Calculate the quantity ΔZ. Furthermore, the calculation unit 2
After that, 6 calculates the thickness of the test material 23 according to the arithmetic expression of (t = ΔZ / ε ^1/2 ) based on the phase shift amount ΔZ and the dielectric constant ε of the test material 23.

That is, as described above, the thickness of the test material 23 made of the dielectric material can be measured in a non-contact manner by utilizing the spatial standing wave W. The present invention is not limited to the above-mentioned one embodiment. For example, a dielectric material whose thickness t is known in advance and whose dielectric constant is unknown is inserted into the spatial standing wave W as the material 23 to be measured, and the above-described measurement is performed.
The dielectric constant ε of the test material 23 can be measured by performing the calculation according to the formula of = (ΔZ / t) ² .

Further, the present invention, as described above, uses the test material 23.
Since the measurement is performed based on the detection of the phase shift amount ΔZ of the spatial standing wave W that is caused by the molecular structure of the material of (3), not only the non-contact measurement of the thickness t and the dielectric constant ε described above but also the measurement of the test material 23 It is also possible to measure changes in constituent materials, differences, etc., or discriminate them without contact.

Further, in the reflector of the present invention, a flat plate-like reflecting plate forming a second reflecting surface facing the first reflecting surface may be used instead of the reflecting horn. In addition, in the microwave measuring apparatus of the present invention, the spatial standing wave may be measured at an intermediate portion other than the antinode or the node.

[0064]

As described above in detail, since the present invention is constructed as described above, it has the following effects. Claim 1
In the spatial standing wave forming method according to (1), since the number of times of mutual interference between the traveling wave and the reflected wave between the reflecting surface and the reflector around the slot antenna is large and the spatial standing wave is amplified, the amplitude is A large spatial standing wave can be formed, and the S / N of the spatial standing wave
The ratio and phase resolution can be improved.

In the apparatus for forming a spatial standing wave according to claim 2, only a specific wavelength can be selected, other wavelengths are rarely superimposed on it, and there is no parallax.
By forming a spatial standing wave having a large amplitude, it is possible to improve the S / N ratio and the phase resolution of the spatial standing wave.

Further, in the microwave measuring apparatus according to the third aspect, the spatial standing wave forming apparatus according to the first aspect can be used to improve the S / N ratio and the phase resolution of the spatial standing wave. The phase shift can be easily detected, and the measurement target of the test material can be detected with high accuracy.

[Brief description of drawings]

FIG. 1 is a diagram showing the configuration of a microwave measuring apparatus for measuring the thickness of a dielectric material according to an embodiment of the present invention.

FIG. 2 is a cross-sectional view showing the configuration of the waveguide along the line ZZ in FIG.

FIG. 3 is a cross-sectional view showing a configuration around a transmission / reception horn taken along line YY in FIG.

FIG. 4 is a cross-sectional view showing a configuration around a reflection horn along line XX in FIG.

FIG. 5 is a diagram showing an output waveform of an electromagnetic wave sensor of the microwave measuring apparatus according to the same embodiment.

FIG. 6 is a view showing a schematic configuration of a spatial standing wave forming unit included in a dielectric material thickness measuring apparatus according to a conventional example.

[Explanation of symbols]

11 ... pedestal, 12 ... pedestal moving means, 13 ... distance sensor, 14 ... electromagnetic wave transmitter, 15 ... electromagnetic wave sensor, 16 ... waveguide, 17 ... wave transmitting / receiving horn, 17a ... first reflecting surface, 17b ... 1 tube, 18 ...
Slot antenna, 19 ... Circulator,
22 ... Reflection horn (reflector), 22a ... Second reflection surface,
22b ... 2nd cylinder part, 24 ... control part,
26 ... Operation part.

Claims (3)

[Claims] 1. A reflection surface around a slot antenna provided in a waveguide for transmitting an electromagnetic wave having a microwave wavelength, and the reflection surface in the electromagnetic wave radiation direction of the antenna substantially orthogonal to a central axis of the antenna. With the reflector provided facing each other,
A method for forming a spatial standing wave, wherein the electromagnetic wave radiated from the antenna is repeatedly reflected between the reflecting surface and the reflector to form a spatial standing wave. 2. A waveguide which transmits an electromagnetic wave having a wavelength of a microwave and which is provided with a slot antenna at an intermediate portion in an axial direction, and a waveguide which is attached to the waveguide and is provided around the slot antenna. 1st which is substantially orthogonal to the central axis of the antenna
A cavity resonance type transceiving horn having a reflecting surface and a first cylindrical portion having one end open and the other end connected to the first reflecting surface and having a constant cross-sectional shape orthogonal to the central axis; A spatial standing wave forming device, comprising: a reflector having a second reflecting surface that is arranged in the electromagnetic wave radiation direction of a wave horn and that is substantially orthogonal to the central axis and faces the first reflecting surface. 3. A waveguide in which a slot antenna is provided at an intermediate portion in the axial direction, and an electromagnetic wave transmitter connected to one end of the waveguide to supply an electromagnetic wave having a microwave wavelength to the waveguide. A first reflecting surface provided around the slot antenna and orthogonal to the central axis of the antenna, and a cross-sectional shape in which one end is open and the other end is continuous with the first reflecting surface and is substantially orthogonal to the central axis. And a cavity resonance type transmission / reception horn having a constant first tubular portion, and a transmission / reception horn is provided in the electromagnetic wave radiation direction of the transmission / reception horn with a space for arranging a test material secured. A reflector having a second reflection surface provided substantially orthogonal to the central axis, an electromagnetic wave sensor connected to the other end of the waveguide, the waveguide, the transmission / reception horn, the reflector, The electromagnetic wave transmitter and the electromagnetic wave transmitter Based on outputs from the electromagnetic wave sensor, a gantry on which a carriage is mounted, a gantry moving unit that reciprocates the gantry along the central axis, a distance sensor that detects a movement amount of the gantry, and an output from the electromagnetic wave sensor. And a control unit for detecting an antinode or a node of the space standing wave formed between the first and second reflection plates, and an output from the control unit and an output from the distance sensor to the space for disposing the test material. A microwave measuring apparatus comprising: a phase shift amount of the spatial standing wave depending on the presence or absence of a test material, and a calculation unit that calculates a measurement target of the test material based on the shift amount.