JPS60119408A - Displacement measuring method - Google Patents

Abstract

PURPOSE:To make a circuit concise by fetching transmitting and receiving waves at two positions in a propagation lapse from a microwave oscillator, phase-shifting one extracting signal by 90 deg., adding it to the other extracting signal, and detecting a phase difference to a low frequency signal. CONSTITUTION:The first and the second detectors 4, 7 detect a mixed wave of transmitting waves (es1, es2) from a microwave oscillator 2 and reflected waves (er1, er2) from an object to be measured A, and send it to the first band-pass filter 5 and the second band-pass filter 8 for extracting the respective fundamental waves. A signal E1 obtained from the first band-pass filter is sent to a 90 deg. phase shifter 6, and a signal E1' is applied to an adder 10. Also, a signal E2 obtained from the second band-pass filter 8 is also applied to the adder 10, and an added signal of both the signals is sent to a phase comparator 11. Subsequently, a phase difference is detected by comparing an oscillated wave from a low frequency oscillator 1 and the phase, and a detecting signal is outputted.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention projects microwaves onto an object to be measured, and utilizes the phase difference between the transmitted wave and the reflected wave table from the object to be measured. Concerning a method of measuring the displacement of.

[Prior art]

A known method for measuring the displacement of an object to be measured is to project microwaves toward the object and utilize the phase difference between the reflected wave and the transmitted wave.

The method includes Double 5ideband Wi
th Carrier Presen method + Dou
ble 5ideband With 5upres
sedCarrier method, Single 5ide
band Witl+ Carrier Present
Method + Single 5ideband With
There are 5uppressed carrier systems, etc., and all of these systems use a phase shifter.

As expected, phase shifters in the microwave band had complicated circuits and were expensive. For this reason, it is not preferable to perform industrial measurements using such a measurement method because the range of measurement application is limited due to the cost of the circuit.

〔the purpose〕

The present invention was made in view of the above circumstances, and its purpose is to simplify the circuit by using a phase shifter in a low frequency band, thereby making it easier to handle and increasing reliability. The purpose of the present invention is to provide a method for measuring displacement.

〔composition〕

The displacement measuring method according to the present invention is a method of measuring the displacement of a measured object using a phase difference between a microwave transmitted toward the measured object and a reflected wave from the microwave. A periodically modulated microwave is guided by an antenna, projected onto the object to be measured, and the reflected wave is received by the antenna.
The transmitted and received waves are extracted at two positions separated by a predetermined distance on the propagation path from the microwave oscillator to the antenna,
Detect the mixed wave of the transmitted and received waves at each position, extract the fundamental wave or specific harmonic from each detected signal, shift one extracted signal by 90 degrees and add it to the other extracted signal, The present invention is characterized in that the phase difference between the signal obtained by this addition and the low frequency signal for modulation is detected, and the displacement of the object to be measured is determined based on this phase difference.

(Example〕 The present invention will be specifically explained below based on the drawings.

The drawing is a schematic diagram showing the implementation state of the present invention, and in the drawing, 1 indicates a low frequency oscillator of Mtlz order, and 2 indicates a microwave oscillator. The transmission wave of the microwave oscillator 2 is frequency modulated by the oscillation wave (Eosin (ωmt)) from the low frequency oscillator 1, and the transmission wave esl is attached to the tip of the waveguide 3 via the waveguide 3. It is sent to antenna 9. The antenna 9 is directed toward the object to be measured. A vibriso I/coupler 12L] 22 is provided in the middle of the waveguide 3 at a distance p, and a hybrid coupler 121 near the microwave oscillator 2 has a first waveform with a square characteristic.
The input terminal of the wave detector 4 is connected to the hybrid coupler 122 near the antenna 9, and the input terminal of the second wave detector 7, which also has square-law characteristics, is connected.

1st. Each of the second detectors 4.7 detects a mixed wave of the transmitted wave (eslles2) from the microwave oscillator 2 and the reflected wave (erller2) from the object under test A, and outputs a detected signal eI.
A first band filter 5 that extracts the fundamental waves of +”2.
．． It is sent to the second band filter 8. First band filter 5
The signal E1 obtained from the above is sent to a 90' phase shifter 6, and the signal E1' phase-shifted by the 90° phase shifter 6 is given to an adder 10.

Further, the signal E2 obtained from the second band filter 8 is also given to the adder 10, and the adder 10 adds the above two signals and sends the added signal to the phase comparator 11. The oscillation wave from the low frequency oscillator 1 is sent to the phase comparator 11, and the phase comparator 11 compares the phases of the re-input signals, detects a phase difference, and outputs a detection signal.

Note that the circuit constants are the first. 1°k for the sensitivity of the second detectors 4 and 7
2. 1st. Based on the output level of the second band filter 6.8, etc., it is adjusted to satisfy the following f1.1 formula.

k, ・Es1 ・Er1−2 ・Es2 ・Er2−
-Es -Er -fil However, Es I+ Er + + Es 21 Er
2: Each signal es l , er l , es 2 .

To the amplitude of er2: 1st. Output width Es of the second band filter: 1st.
Amplitude Er of the fundamental wave or harmonic of the transmitted wave component after passing through the second band filter: 1st. Regarding the amplitude of the fundamental wave or harmonic of the reflected wave component after passing through the second band filter, and the separation distance l, please refer to (2) 2 or (3) below.
It is determined that the formula is satisfied.

Or...(3) However, λg is the wavelength within the waveguide of two microwaves.Next, the measurement principle of the present invention will be explained. Since the transmitted wave is the microwave from the microwave oscillator 2 frequency-modulated by the oscillation wave from the low-frequency oscillator 1, the angular frequency ω is expressed by the following equation (4).

ω−ωh +'A・Δω・sin (ωmt) ・・・
(4) However, ω0: center frequency Δω: frequency change width Such a transmitted wave is input to the first detector 4.

The transmitted wave es1 at this time is expressed by the following equation (5).

es I=Es 1・sin (ωt) ・(51e3
2, since the second detector 7 is separated from the first detector 4 by a distance β on the antenna 9 side, the phase delay is 2.
πi/λg, and the following formula (6) % Formula % Next, α is the phase delay caused by the transmitted wave reciprocating between the first detector 4 and the antenna 9, and α is the phase delay caused by the antenna 9 outputting the transmitted wave. If the phase delay during which the reflected wave from the object A is captured is φ, the reflected wave er1 is expressed by the following equation (7).

er 1=Er 1・sin (ω is one φ−α) −(
7) Regarding 6r2, there is a delay by the phase obtained by subtracting the phase of the signal reciprocating over the distance l from the phase delay α, so ef2 is expressed by the following equation (8).

g g Since the detector 7 inputs the mixed signals es2 and er2, the first . The second detectors 4 and 7 each output a signal "l+e2" shown by equations 91 and 101.

e1=to+C'AEs+2+V2Er 1"+E
s H・Er 1・cos (φ+CX)) ・19)
62 =, 2 C'AEs 2 2 →-'A Er
22] g (10) At this time, since the separation distance ρ is determined to satisfy the above formula (2) or (3), the right side of formula (10) is obtained.

Therefore, as understood from the f91.001 formula, the first
Output signal e of the detector 4 and output signal e of the second detector 7
This results in a phase difference of 90 degrees.

Now, if the distance from the antenna 9 to the object to be measured A is X, the phase delay φ is expressed by the following equation (11), where C: microwave propagation speed. By substituting , φ becomes the following (
12) Equation becomes.

(12) Then, in equation (12), sin φ and cos φ are expressed by equations (13) and (14) below.

(Margin below) 0 That is, cos φ-cos (φ, +I)-sin (0mm
))-CO3φ0 °cos fD゛sin (0mm
)1-sin φo-5in (D-sin ((+
+11 t) 1=Jo (D) ・cos φo+2
・cos φ.

・sin ((2n+1) ωmtl ... (13)
However, Jo (D), Jzn (D), J2n++ (
D) is the hesocell function of the first kind sin φ −5in (φ ro + r)−sin (
0mm))=sin φo-cos (D-sin (
0m1) 10 CO3φo -5in (D-sin (
0mm) 1-Ja (D> ・sin φ0 →2・s
jnφ.

・sin ((2n+1) 0mm) ...(14
)1 Therefore, from (13) and (14) the composite wave of warriors,
For example, if filters 5 and 8 are set so that the fundamental wave component when n=1 is extracted, the signals E, , E2 and E+ = 2・k−Es after passing through filters 5 and 8
−Er −J+ (D)・sin (φ(,+α)
・sin (0m t) −(15)E2 =2・k−
Es −Er −J+ (D)・cos (φθ+α)
・sin (0m t)...(16). The signal of El is sent to the 90° phase shifter 6 and phase-shifted, as shown below (17
) The signals E and l are expressed by the following equations.

E+ '--2・k-Es -Er-Jl (1))
・sin (φ. +α) ・sin (0mm ±
--) 1--2-1(・Es −Er ・Jl (D)
・sin (ψθ +α)・cos (0mm)el,
e2 are adjusted to be in phase.

The signal E+' and the signal E2 are sent to the adder 1o, which adds these signals and sends the added signal expressed by the following equation (18) to the phase comparator 11.

E+ ' 10E2-2 ・k-Es -Er -J+
(D) 1(sin (φ0 → −α)7cos(ω1t
)-cos (φ0 +α)・5in(0mm)1--
2- to −Es −Er −J+ (D)・sin (φ
0 → −α−ωmt) −2・k−Es −Er −J+ (D)・sin (
ωmt−φ. -α) ... (18) The phase comparator 11 uses the above equation (1st) and the output wave of the low frequency oscillator 1, that is, E. The phase is compared with sin (0m t>), and the phase difference φa+α obtained by the comparison is output.

Measurement phase φ. → Since -α has an arbitrariness every 2π, it is not possible to determine the distance The displacement ΔX of A can be known. That is, the displacement ΔX is 3 Z.

Note that in the above explanation, measurements are made using the fundamental wave component, but
The present invention is not limited to this, and any harmonic component may be used. Furthermore, although a sine wave is used for the microwave, it is not limited to this, and other rectangular waves, triangular waves, etc. may also be used, and it goes without saying that similar results can be obtained using rectangular waves, triangular waves, etc. .

Next, the effects of the present invention will be explained based on Examples. A varactor-tuned Gunn oscillator is used as the microwave oscillator 2, and a 1.5 dB obtemamp phon is used as the antenna 9.
0.5m x 0.5, about 0.5m away from antenna 9
The center frequency ωo/2 is aimed at the object A, which is a steel plate of
π: lO, 525 GHz, center wavelength λ: approximately 28.5
mm, frequency change width Δω/2π: IOMH2, output 4: A microwave of about 10 mW was transmitted to measure the displacement of the steel plate.

As a result, the resolution was 10 μm, and the maximum displacement was 14.
The linearity of the device's phase change output for 25 am was less than 0.1 mm.

〔effect〕

As detailed above, since the displacement measurement method according to the present invention uses microwaves modulated at a low frequency, the phase shifter may be of a low frequency, and the phase shift angle may be fixed at 90'. Therefore, the circuit configuration is simple, the handling for measurement is easy, the reliability is high, and measurement with sufficiently high precision is possible.

In the case of the present invention, the present invention has excellent effects such as being able to provide an inexpensive measuring device.

[Brief explanation of drawings]

FIG. 1 is a schematic diagram showing an implementation state of the present invention. I...Low frequency oscillator 2...Microwave oscillator 3.
...Waveguide 4...First wave detector 5...First band filter 6...90° phase shifter 7...Second wave detector 8...Second band filter 10... Adder 11
...Phase 5 Comparator patent Applicant Sumitomo Metal Industries Co., Ltd. Agent Patent attorney Noboru Kono 6

Claims (1)

[Claims] 1. In a method of measuring the displacement of a measured object using the phase difference between the microwave transmitted toward the measured object and the reflected wave, periodic modulation is applied at low frequency. The microwave is guided to the antenna, projected onto the object to be measured, and the reflected wave is received by the antenna, and transmitted and received at two positions separated by a predetermined distance on the propagation path from the microwave oscillator to the antenna. @ Extract the wave, detect the mixed wave of the transmitted and received waves at each position, extract the fundamental wave or specific harmonic from each detected signal, shift one extracted signal by 90 degrees and extract the other. A displacement measuring method characterized by adding signals, detecting a phase difference between the signal obtained by the addition and the low frequency signal for modulation, and determining the displacement of the object to be measured based on this phase difference. .