JP2002116005A - Laser-interferometer type displacement gauge - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a laser-interferometer type displacement gauge, provided with a ring laser resonator as a dual-frequency ring laser light source. SOLUTION: The laser-interferometer type displacement gauge is provided with a displacement detecting mirror 42, mounted to a body under displacement detection of receiving and reflecting one laser light among dual-frequency laser beams emitted to outside via a laser beam extracting part from the double- frequency ring laser light source and feeding the one laser light back to the laser beam extracting part, a receiver 52 for output for superposing the reflected light at the laser beam extracting part of the feedback light which is fed back from the displacement detecting mirror 42 on the other laser beam among the dual-frequency laser light emitted to outside from the laser beam extracting part to from optical beat, receiving the optical beat as a detection signal, and photoelectrically converting it, and a signal processing part 5 for processing the received electrical signal of the receiver 52 for output to create a signal, which indicates displacement of the body to be distortion detected.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a laser interferometer-type displacement meter, and more particularly to a laser interferometer-type displacement meter using the Doppler effect for optically measuring the displacement of a detection object in a non-contact state.

[0002]

2. Description of the Related Art A conventional example will be described with reference to FIG. FIG.
The interferometer configured in (a) is a Michelson-type interferometer. The two-frequency laser light source 1 is used as a light source.
As the two-frequency laser light source 1, a Zeeman laser using a Zeeman effect by a magnetic field in which a magnet is combined with a laser light source such as a He-Ne laser resonator has been generally used. The Zeeman laser obtains laser beams of two frequencies in polarization states orthogonal to each other, and these two frequency laser lights are output from the light source as linearly polarized lights orthogonal to each other.

The Michelson interferometer shown in FIG. 5A uses a first polarization-independent beam splitter 21 and a second polarization-independent beam splitter 22 as light beam splitting elements constituting the Michelson interferometer. I have. The two-frequency light beam emitted from the two-frequency laser light source 1 is first split by the first beam splitter 21. The two-frequency light flux transmitted through the first beam splitter 21 is further split by a second polarization-independent beam splitter 22.

[0004] Here, transmitted through the first beam splitter 21, f ₁ component of the two-frequency light flux transmitted also the second polarization-independent beam splitter 22, f ₁ which allowed to transmit this
The light passes through the frequency filter 38 and is sent to the displacement detection branch M. The f ₁ component of the two-frequency light beam sent to the displacement detection branch M is reflected by the displacement detection mirror 42 and returns to the second polarization-independent beam splitter 22, while passing through the first beam splitter 21, The f ₂ component of the two-frequency light beam reflected by the two polarization-independent beam splitters 22 is transmitted to the beat detection branch B of the Michelson interferometer after passing through the f ₂ frequency filter 39 that allows the light to pass therethrough. F ₂ component of the two-frequency light flux fed into the beat detection branch B is fed back to the second polarization-independent beam splitter 22 is reflected at mirror 41. F ₁ component and f ₂ components of the light beam returned to the polarization-independent beam splitter 22 again multiplexes herein.

By the way, the frequency of the f ₁ component of the light beam reflected by the displacement detecting mirror 42 is subject to a Doppler shift of Δf ≒ 2v (f ₁ / c) due to the moving speed v of the displacement detecting mirror 42. Here, c indicates the speed of light. The signal processing unit 5 detects an optical beat between the (f ₁ ± Δf) component having undergone the Doppler shift and the f ₂ component reflected by the mirror 41 of the beat detection branch B. When detecting the optical beat in the signal processing unit 5, the output mixing polarizer 51 is a polarizer that extracts a vibration component in which the two light beams are superposed because the two light beams are orthogonal in polarization state.
Must be placed before the output receiver 52.

The reference light branch R emitted from the dual-frequency laser light source 1 and reflected by the first beam splitter 21
The beats of the two-frequency light beam that have not been subjected to the Doppler shift and sent to the CPU are separately processed via a reference mixing polarizer 61, a reference receiver 62, and a reference counter 63, and are detected as reference light. The beat signal including the Doppler shift Δf and the beat signal that has not been subjected to the Doppler shift are input to a subtractor 54 and subjected to subtraction processing, and the Doppler shift Δ
f is obtained, and Δf is integrated in the integrator 55 to detect the displacement.

Here, the displacement is counted by the output counter 53 by adding the time t to the movement speed v, and v · t = (c / 2f ₁ ) Δf · t. Referring to FIG. 5B, this is a polarization beam splitter that separates an incident light beam into transmitted light and reflected light by a polarization state instead of the second polarization independent beam splitter 22 in FIG. 5A. 23 is used to compose an interferometer. Other configurations of the conventional example in FIG. 5B are the same as the corresponding configurations in the conventional example in FIG.

[0008]

The conventional two-frequency laser light source 1 of the laser interferometer-type displacement meter described above combines a laser light source and a magnet to separate the frequency of the two-frequency laser light by the Zeeman effect by a magnetic field. Light source. 2
The magnet required for frequency separation of the high frequency laser light has a large-sized heavy equipment and a complicated structure for mounting and fixing.

In this conventional example, the beat detection branch B and the reference light branch R are formed as protrusions as components of the Michelson interferometer, and the space factor and space availability as a laser interferometer type displacement meter are inconvenient. I was doing it. In addition to the need for a frequency filter that separates two-frequency light beams and a polarization beam splitter, a mixing polarizer that extracts a superimposed component between orthogonal polarizations is also required, and a configuration that extracts a superposed component using a mixing polarizer is adopted. As a result, only half of the light amount can be used for signal detection.

In the above conventional example, the detection accuracy is increased unless the speed of movement v of the object to be detected is high enough to form Δf sufficiently larger than the optical frequency difference (f ₁ −f ₂ ). Can not do. The present invention provides a laser interferometer-type displacement meter that solves the above-mentioned problem by using a ring laser resonator as a laser light source.

[0011]

A closed annular optical path is formed in a glass block.
And three or more mirrors 30, 31, 32 including at least one semi-transmissive mirror 30 are installed along
The CW laser beam and the clockwise CW laser beam are passed through the circular optical path 1
1. A ring that constitutes a laser resonator for propagating along the direction 1 and emits counterclockwise CCW laser light and clockwise CW laser light having frequencies different from each other to the outside via a laser light extraction unit including a semi-transmissive mirror 30. Laser resonator 1
0 is provided as a two-frequency ring laser light source, attached to the displacement detector, and receives and reflects one of the two-frequency laser light emitted from the two-frequency ring laser light source to the outside via the laser light extraction unit. A displacement detection mirror for returning the laser beam to the laser beam extraction unit; a reflected light of the feedback beam returned from the displacement detection mirror at the laser beam extraction unit; and a two-frequency laser beam emitted from the laser beam extraction unit to the outside. An output receiver 52 that receives an optical beat formed by superimposing the other laser beam as a detection signal and performs photoelectric conversion on the optical beat, and processes a received light signal of the output receiver 52 to generate a displacement detection mirror. A laser interferometer-type displacement meter including a signal processing unit 5 for generating and outputting a signal indicating the displacement of the displacement detecting body based on the Doppler shift of the feedback light due to the movement of the laser 42. Form was.

A second aspect of the present invention is a laser interferometer-type displacement meter, wherein the laser light extraction portion of the two-frequency ring laser light source includes a semi-transmissive mirror 30 and a light-transmissive substrate bonded to the surface thereof. 37, a laser interferometer type displacement meter in which the displacement detection mirror 42 is constituted by the corner cube type prism 34. In a third aspect of the present invention, in the laser interferometer-type displacement meter according to any one of the first and second aspects, a laser beam extraction unit;
A laser interferometer-type displacement meter including a plurality of sets each including a displacement detection mirror 42, an output receiver 52, and a signal processing unit 5 was configured.

[0013] Claim 4: Claims 1 to 3
In the laser interferometer-type displacement meter described in any one of the above, the signal processing unit 5 receives an electric signal output from the output receiver 52 and outputs an integrated counter to count the displacement, and a reference counter. Output unit 56 and output counter 53
A laser interferometer-type displacement meter comprising a subtractor 54 for inputting the output of the reference constant output unit 56 and the output of the reference constant output unit 56 to obtain the Doppler shift, and an integrator 55 for integrating the Doppler shift and detecting the displacement. did.

[0014] Claim 5: Claims 1 to 3
The laser interferometer-type displacement meter described in any one of the above, further comprising a reference laser light extraction unit for emitting the dual-frequency laser light to the outside, and receiving the optical beat of the dual-frequency light and performing photoelectric conversion. Signal processing unit 5
Has a laser interferometer-type displacement meter having a reference counter 63 for inputting an electric signal output from the reference receiver 62. Claim 6: In the laser interferometer-type displacement meter according to any one of Claims 1 to 5, the two-frequency ring laser light source includes a counterclockwise CCW laser light propagating counterclockwise and a counterclockwise CCW laser light. Two anodes 2 oscillating clockwise CW laser light, respectively
4 and 25 and a single cathode 3 common to them.
A laser interference having a Ne laser light source, injecting currents of different magnitudes into the two anodes, causing a Langmuir flow of He-Ne gas to cause a difference in the oscillation frequency of the dual frequency laser light. A displacement meter was constructed.

[0015]

Embodiments of the present invention will be described. The present invention uses a ring laser resonator as a laser light source in a laser interferometer-type displacement meter. This ring laser resonator will be described with reference to FIG. In FIG. 1, an annular ring laser resonator 10 closed in a glass block G is formed, and a laser oscillation gas is sealed in an annular optical path 11. When a voltage is applied between the first anode 24, the second anode 25, and the cathode 3, a plasma discharge is generated, and the resulting laser light is applied to the half-wave disposed along the annular optical path 11. Transmission mirror 30, first
While being reflected by the flat mirror 31 and the second flat mirror 32, the circular optical path 11 propagates and circulates independently as a counterclockwise CCW laser beam and a clockwise CW laser beam. The semi-transmissive mirror 30 constitutes a laser beam extraction unit. Here, in the above ring laser resonator, the mirror is a first plane mirror 3 including one semi-transmissive mirror 30.
Although it is composed of a total of three first and second plane mirrors 32, it can also be composed of a total of four or more mirrors including one semi-transmissive mirror 30.

A part of the CCW laser light is transmitted through the semi-transmissive mirror 30.
Further, the light passes through the light-transmitting substrate 37 lining the light and is extracted to the outside, and directly enters the output receiver 52. A part of the CW laser light passes through the semi-transmissive mirror 30 and the light-transmitting substrate 37 and is extracted to the outside, is retroreflected by the corner cube type prism 34, is reflected by the surface of the light-transmitting substrate 37, and is output to the receiver. 52. The translucent mirror 30 from which the laser light is extracted is bonded and lined with a light transmissive substrate 37 such as glass having an appropriate thickness. The light transmitting substrate 37 lining the semi-transmissive mirror 30 and the corner cube type prism 34 are used in combination to form the light transmitting substrate 3
By appropriately setting the thickness of 7, a parallel space is provided between the incident light and the reflected light of the corner cube type prism 34, and the light is reflected by the corner cube type prism 34 to be on the surface of the light transmitting substrate 37. The optical axis of the reflected light that arrives and is reflected and the transmitted light that passes through the light-transmitting substrate 37 and exits from the reflection point of the light ahead of the surface are matched. That is, the optical axis of the CW laser beam that transmits through the semi-transmissive mirror 30 and the light-transmitting substrate 37, is retroreflected by the corner cube prism 34, and is reflected by the surface of the light-transmitting substrate 37, The optical axis of the CCW laser light that passes through and exits the light-transmitting substrate 37 backing the light-transmitting substrate 37 can be matched by appropriately setting the thickness of the light-transmitting substrate 37. Incidentally, the CCW laser light and the CW laser light interfere with each other immediately before being incident on the output receiver 52 to generate interference fringes. The output receiver 52 detects this interference fringe. This is known as a ring laser gyro practically used as an angular velocity detector.

Here, when the ring laser resonator 10 is used to form a ring laser gyro,
Since the W laser light and the CW laser light must be emitted at the same frequency, the currents applied to the first anode 24 and the second anode 25 are controlled to exactly the same current value, and the CCW laser light and the CW laser light are controlled. The light frequency is the same. However, when the ring laser resonator 10 is used as a light source of a laser interferometer-type displacement meter, conversely, the CCW laser light and the CW laser light must have two different frequencies. Therefore, the ring laser resonator 10
In the above, by providing a difference between the currents applied to the first anode 24 and the second anode 25, a frequency difference can be easily generated between the CCW laser light and the CW laser light. Hereinafter, this will be described more specifically.

When the ring laser resonator 10 is used as a laser light source, the difference between the oscillation frequencies of the CCW laser light and the CW laser light can be provided by providing a difference between the pumping currents i ₁ and i ₂ of the two lights. There is a method of driving the first anode 24 and the second anode 25 to generate a Langmuir flow to generate a frequency difference. The method of forming the oscillation frequency difference is a simple method that is extremely excellent in variable operability. The Langmuir flow of a gain medium in a laser is well known as one of noise factors, particularly in the field of ring laser gyros. See `` F.Arno
witz; THE LASERGYRO, pp.178-183, Velocity Flow of th
e Active Medium, in “LASER APPLICATIPNS” ed M.Ros
s, Academic Press, 1971 ". In embodiments of the present invention, by supplying a pumping current i ₂ to the pumping current i ₁ and the second anode 25 from the high voltage power supply 26 to the first anode 24, a typical value injection current applied in each 1mA increments in the base, Pumping current difference (i ₁ −i ₂ ) = 1 μ
The oscillation light frequency difference of about 0.1 Hz per current difference of A can be obtained almost linearly in the use region.

In addition to the method of forming the oscillation frequency difference,
In the ring laser resonator 10 oscillating by circularly polarized light, a magnetic field is applied in the traveling direction of light, and C is applied by utilizing the Faraday effect.
A difference can be provided between the oscillation frequencies of the CW laser light and the CW laser light. An embodiment of the present invention will be described with reference to FIG. In this embodiment, the ring laser resonator 10 shown and described with reference to FIG. 1 is used as a laser light source. However, this embodiment is used without the light transmitting substrate 37.

The optical frequency component of the CCW laser light is represented by f _2, and the f ₂ component of this light is transmitted through the semi-transmissive mirror 30 and is extracted to the outside, and directly enters the output receiver 52. The optical frequency component of the CW laser light is defined as f _1, and the f ₁ component of this light is transmitted through the semi-transmissive mirror 30 and extracted to the outside, and then propagates to the displacement detection mirror 42 to move the movement velocity v of the displacement detection mirror 42. As a result, a Doppler shift of Δf ≒ 2v (f ₁ / c) is received, the light returns to the surface of the semi-transmissive mirror 30, is reflected, and enters the output receiver 52.

The (f ₁ ± Δf) component of the light returned and reflected on the surface of the semi-transmissive mirror 30 is the CCW laser light which has not been subjected to the Doppler shift directly emitted through the semi-transmissive mirror 30 as in the conventional example. and the superposed interference immediately before entering the optical frequency component f ₂ to the output receiver 52, the signal processing unit 5
And is extracted as an optical signal corresponding to the displacement. The signal processing unit 5 receives an electric signal output from the output receiver 52, accumulates the displacement, and counts the displacement.
3, a reference constant output unit 56, a subtractor 54 that receives the output of the output counter 53 and the output of the reference constant output unit 56 to obtain the Doppler shift, and integrates the Doppler shift to calculate the displacement. It comprises an integrator 55 for detecting. The reference constant output unit 56
The signal of digital values generated output representing the frequency difference between the CW light and the CCW light (f ₁ -f _2).

The second embodiment will be described with reference to FIG.
In the first embodiment of FIG. 2, the return light reflected by the displacement detection mirror 42 reaches the vicinity of the point where the CCW and CW light around the ring laser resonator 10 of the transflective mirror 30 is reflected. An unstable external resonator is formed by being partially coupled to the oscillation mode of both the CCW and the CW light. Even in this case, since the light transmittance of the semi-transmissive mirror 30 constituting the ring laser resonator 10 is generally small, the oscillation modes of the frequencies f ₁ and f ₂ are maintained. If the oscillation modes f ₁ and f ₂ approach or overlap with each other, the original oscillation mode may be involved or compete with the oscillation mode, and the stability of the laser interferometer-type displacement meter as a light source may be impaired. Therefore, in the ring laser resonator of the second embodiment, the light transmitting substrate 37 such as glass having an appropriate thickness is used.
Is bonded to the semi-transmissive mirror 30, and the displacement detecting mirror 42
By using a corner cube type prism 34 as a retroreflective element and providing a parallel interval between incident light and reflected light, return light is prevented from being coupled to the CCW and CW round modes of the ring laser resonator 10. Thus, the stability of the laser interferometer-type displacement meter as a light source is secured.
That is, when the above-described ring laser resonator 10 is used as a laser light source of a laser interferometer-type displacement meter, the spot size of the light beam of both round lights of CCW and CW is about 1 mm in diameter, and the corner cube type prism 34
3-4mm between incident light and reflected light by using
And the displacement detection mirror 42
Does not reach the vicinity of the reflection point of both the CCW and CW of the ring laser resonator 10 in the semi-transmissive mirror 30. This makes it impossible for the return light to re-circulate in the annular optical path 11 again, and secure stable oscillation as a light source of the laser interferometer-type displacement meter.

Here, the ring laser resonance shown in FIG.
A first plane mirror 31 and a second plane mirror
The mirror 32 on a semi-transmissive mirror equivalent to the semi-transmissive mirror 30
In other words, the laser light is set along the annular optical path 11.
Semi-transmissive mirror 30, first flat mirror 31, second flat mirror 31
The annular optical path 11 is counterclockwise reflected by the plane mirror 32
As clockwise CCW laser light and clockwise CW laser light
They can propagate and circulate independently of each other. This
Laser light from these semi-transmissive mirrors
Can be The second embodiment of FIG.
In the embodiment, the laser light is extracted from the rollers 30 and 31 to the outside.
is there. According to this embodiment, one laser light source is used.
Reference beam branch R using the
A single laser interferometer displacement meter
Wear. That is, a reference laser for emitting a two-frequency laser beam to the outside.
A laser light extraction unit. This reference laser beam
Receives the optical beat of the two-frequency light emitted and output from the extraction unit.
A reference receiver 62 that performs light-to-photoelectric conversion is provided.
You. Then, in the signal processing unit 5 of the embodiment of FIG.
The output of the reference receiver 62 is used in place of the illumination output unit 56.
Input reference beat signal to generate reference signal
A counter 63 is provided. Provides a constant reference signal
Instead of the reference constant output unit 56,
The reference counter 63 for generating the reference signal
Thus, the oscillation frequency difference (f ₁−f_Two)But
Even if it fluctuates depending on environmental conditions, the fluctuating oscillation frequency
Number difference (f₁−f_Two) Is separately detected and subtracted.
It is possible to always take out the correct value of Δf
It works.

A third embodiment will be described with reference to FIG.
In the third embodiment, the second plane mirror 32 in the second embodiment of FIG. 3 is also replaced with a semi-transmissive mirror equivalent to the semi-transmissive mirror 30, and the counterclockwise CCW laser light and the clockwise CW Take out part of the laser light and easily
It is an example which comprises a laser interferometer type displacement meter of the system.
The reference counter 63 is commonly used by a plurality of laser interferometer type displacement meters.

As the laser light source of the laser interferometer-type displacement meter of the present invention, a ring laser resonator having different oscillation frequency modes for both left and right circling lights can be generally used. It is preferable to use a ring laser resonator having a resonator length of 20 to 30 cm in the He-Ne laser of ゜.

[0026]

As described above, according to the present invention, a configuration is employed in which a ring laser resonator is used as a light source and a two-frequency laser beam is generated by controlling the discharge current. . Thus, a two-frequency laser beam can be easily obtained without using a magnet which is a large-sized heavy equipment having a complicated structure for mounting and fixing and which requires frequency separation.

By employing a ring laser resonator as a light source, a plurality of systems of laser interferometer-type displacement meters can be easily constructed from one ring laser resonator, and a more inexpensive laser interferometer can be used. A type displacement meter can be configured. Accordingly, it is possible to provide a displacement meter that simultaneously measures the displacements of a plurality of displacement detectors with one light source including a ring laser resonator. Further, the conventional Michelson interferometer is inconvenient in terms of space utilization because the reference beam branch, the beat detection branch, and the displacement detection branch protrude, but the laser interferometer type displacement of the present invention employing a ring laser resonator as a light source. The meter does not have these protruding branches and can be made compact as a whole.

Further, since the ring laser resonator is a light source which emits a light beam of two frequencies having the same polarization state, it eliminates the need for a frequency filter, a polarization beam splitter, and a polarization independent beam splitter required in the conventional example. At the same time, it is necessary to extract a superposition component between orthogonal polarizations by a mixing polarizer, and only half of the light amount can be used for signal detection. This improves the disadvantage, and improves the SN ratio by using the entire light amount supplied by the light source. be able to.

Although it is impossible with a conventional Zeeman laser to make the setting of the difference between the two frequencies of the light source variable, the noise due to the region of the movement speed of the displacement detector to be measured, the use environment, etc. Corresponding to the spectrum of
By providing a difference between the pumping currents of the CCW laser light and the CW laser light, the light source frequency difference can be appropriately set. According to the present invention, by adopting the above-described configuration, the oscillation frequency difference (f ₁ −f ₂ ) of the laser light can be variably set suitably in accordance with the region of the movement speed of the displacement detection body. By doing so, displacement measurement with high detection accuracy can be performed without depending on the movement speed of the displacement detection body.

[Brief description of the drawings]

FIG. 1 illustrates a two-frequency ring laser light source.

FIG. 2 illustrates an embodiment.

FIG. 3 is a diagram illustrating a second embodiment.

FIG. 4 is a diagram illustrating a third embodiment.

FIG. 5 is a diagram illustrating a conventional example.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 2 frequency laser light source 10 Ring laser resonator 11 Ring optical path 12 Frequency laser light source 21 1st polarization independent beam splitter 22 2nd polarization independent beam splitter 23 Polarized beam splitter 24 1st anode 25 2nd anode 26 High voltage power supply 3 Cathode 30 Semi-transmissive mirror 31 First plane mirror 32 Second plane mirror 34 Corner cube prism 36 Photodetector 37 Light transmissive substrate 38 f ₁ frequency filter 39 f ₂ frequency filter 41 mirror 42 Displacement detection mirror 5 Signal Processing Unit 51 Output Mixing Polarizer 52 Output Receiver 53 Output Counter 54 Subtractor 55 Integrator 56 Reference Constant Output Unit 61 Reference Mixing Polarizer 62 Reference Receiver 63 Reference Counter

Continued on the front page F term (reference) 2F064 AA01 BB05 CC04 FF02 GG16 GG22 HH00 JJ05 JJ11 2F065 AA02 AA06 BB25 BB29 DD03 FF51 GG04 HH04 HH13 JJ00 LL00 LL02 QQ25 QQ27 QQ51

Claims (6)

[Claims] 1. A closed annular optical path is formed in a block of glass, and three or more mirrors including at least one semi-transmissive mirror are installed along the annular optical path to provide a counterclockwise CCW.
A counterclockwise CCW laser beam and a clockwise clockwise laser beam that constitute a laser resonator that propagates a laser beam and a clockwise CW laser beam along an annular optical path and have different frequencies from each other via a laser beam extraction unit composed of a semi-transmissive mirror. A ring laser resonator that emits CW laser light to the outside is provided as a two-frequency ring laser light source, is attached to a displacement detector, and is emitted from the two-frequency ring laser light source to the outside via a laser light extraction unit. It has a displacement detection mirror that receives and reflects one of the laser beams out of the light and feeds it back to the laser beam take-out unit. An optical beat formed by superimposing the other laser light of the two-frequency laser light emitted outside is received as a detection signal. A signal for processing the received light signal of the output receiver and generating and outputting a signal indicating the displacement of the displacement detection object based on the Doppler shift of the feedback light due to the movement of the displacement detection mirror. A laser interferometer type displacement meter comprising a processing unit. 2. The laser interferometer-type displacement meter according to claim 1, wherein the laser light extraction portion of the two-frequency ring laser light source comprises a semi-transmissive mirror and a light-transmissive substrate bonded to a surface of the semi-transparent mirror. A laser interferometer-type displacement meter, wherein the mirror is formed by a corner cube type prism. 3. The laser interferometer-type displacement meter according to claim 1, wherein a set including a laser light extraction unit, a displacement detection mirror, an output receiver, and a signal processing unit is provided. A laser interferometer-type displacement meter comprising a plurality of sets. 4. The laser interferometer-type displacement meter according to claim 1, wherein the signal processor receives an electric signal output from the output receiver and counts the displacement. Output counter, reference constant output unit, subtractor that receives the output of the output counter and the output of the reference constant output unit to obtain Doppler shift, and detects displacement by integrating Doppler shift A laser interferometer-type displacement meter, comprising: 5. The laser interferometer-type displacement meter according to claim 1, further comprising: a reference laser light extraction unit that emits a two-frequency laser beam to the outside; A laser comprising: a reference receiver that receives a light beat of light and performs photoelectric conversion; and the signal processing unit further includes a reference counter that inputs an electric signal output from the reference receiver. Interferometer type displacement meter. 6. The laser interferometer-type displacement meter according to claim 1, wherein the two-frequency ring laser light source and the clockwise counterclockwise CCW laser light propagate counterclockwise. It has a He-Ne laser light source consisting of two anodes oscillating each of the circulating CW laser light and one cathode common to them, and injects currents of different sizes into the two anodes. ,
A laser interferometer-type displacement meter characterized by generating a Langmuir flow of He-Ne gas to cause a difference in the oscillation frequency of a two-frequency laser beam.