JPH08166215A - Optical displacement detector - Google Patents

Abstract

PURPOSE: To hold detection accuracy by connecting a bellows for vacuum camber which covers an optical path formed by connecting an emission interference part and a reflection mirror to two vacuum tanks, providing a drive device for changing length of the optical path, and applying pressure on a pressurization camber formed between the two vacuum tanks. CONSTITUTION: The first vacuum chamber 1 is fixed to a device main body 9, a laser beam is generated in its inside, and an interfering emission interference part 10 is provided. The second vacuum chamber 2 is attached to the main body 9 via a bearing part 9A so as to approaching to/departing from the vacuum chamber 1 and provided with a reflection mirror 11 in its inside. An optical path 12 is formed by connecting the reflection mirror 11 and the interference part 10 and the optical path 12 is made to coincide with the axis of a bellows 3 for a vacuum chamber. The drive device 5 is provided with a motor 13 fixed to the outside of the vacuum tank 1 and the like and the length of the optical path 12 is changed by approaching/departing the vacuum chambers 1 and 2. When the length of the optical path 12 is changed by approaching/departing the vacuum chambers 1, 2, a pressure control means 8 applies pressure for nullifying resistance force, which acts on the expansion/contraction direction of the bellows 3, on a pressurization chamber 7.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention is based on a change in the length of an optical path formed by connecting a light emission interference section and a reflection mirror inside two vacuum chambers. The present invention relates to an optical displacement detector that detects displacement between vacuum chambers.

[0002]

BACKGROUND ART Some optical displacement detectors use a laser interferometer having a laser light source and a reflecting mirror. When this type of optical displacement detector is used in the atmosphere, the refractive index changes due to fluctuations in air temperature, humidity, atmospheric pressure, CO ₂ concentration, etc., so it is necessary to correct the measured value according to the refractive index. Even if the measurement value is corrected, the correction value itself may include an error. In order to eliminate the influence of such a refractive index, it is possible to put the entire optical displacement detector in a vacuum chamber, but this would make the vacuum chamber itself large and require a large-scale mechanism. The detector becomes expensive. Therefore, conventionally, there is known an optical displacement detector in which the influence of the refractive index is eliminated by making only the optical path between the light emitting portion of the laser light source and the laser interference portion and the reflecting mirror a vacuum.

A conventional example of an optical displacement detector having a vacuum chamber is shown in FIG. As shown in FIG. 5, the conventional optical displacement detector includes a first vacuum chamber 51 fixed to the device body 50.
And a vacuum chamber 54 having a second vacuum tank 52 provided in the apparatus main body 50 via a bearing portion 50A, and a bellows 53 connecting these vacuum tanks 51, 52 to each other. And the second vacuum chamber 52 is the drive motor 5
5, a driving device 58 including a driving screw shaft 56 and a nut 57 allows the driving device 58 to approach and separate. First vacuum chamber 5
A light emission interference part 59 including a laser light source and a laser interference part is provided in the inner center part of 1, and a reflection mirror 60 is provided in the inner center part of the second vacuum chamber 52, with the light emission interference part 59 and the reflection mirror. An optical path 61 is formed on the center line by connecting with 60. This optical path 61 includes the first vacuum chamber 51 and the second vacuum chamber 5.
The distance between the first vacuum chamber 51 and the second vacuum chamber 52 can be detected based on the change in the length of the optical path as the distance between the first vacuum chamber 51 and the second vacuum chamber 52 is changed.

[0004]

The first vacuum chamber 51 is connected to each other by a bellows 53 in order to change the length of the optical path.
When the second vacuum tank 52 and the second vacuum tank 52 are separated from each other, the effective area A ₁ of the bellows 53 and the external pressure (atmospheric pressure) P ₀ surrounding the vacuum tanks 51 and 52 are between these vacuum tanks 51 and 52. The resistance force F (= A ₁ × P ₀ ) formed by the product is the first and second vacuum chambers 5.
It occurs on the center line of 1,52. In this case, since the magnitude of the driving force and the magnitude of the resistance force are different, a driving force difference corresponding to the resistance force occurs depending on the driving direction. Furthermore, since the drive device 58 is provided at the end portions of the first and second vacuum chambers 51 and 52, the action axis of the driving force and the action axis of the resistance force acting on the center line are not on the same axis. A moment (M = F × L ₁ ) is generated due to the axial distance L ₁ between the operating axis of the driving force and the center line, and the vacuum chambers 51 and 52 and the bearing portion 50A are distorted.

Therefore, in the conventional example shown in FIG. 4, the light emission interference section 59 provided in the first vacuum chamber 51, the reflecting mirror 60 provided in the second vacuum chamber 52, and these light emission interference sections 59. And an optical path 61 formed by connecting the reflecting mirror 60 to each other, the optical system formed by connecting the first and second vacuum chambers 51 and 52 as a result of the approaching and separating movement of the first vacuum chamber 51 and the second vacuum chamber 52.
However, there is a problem that it cannot be maintained on the center lines of the vacuum chambers 51 and 52, and high detection accuracy cannot be maintained.

It is an object of the present invention to prevent the geometrical accuracy between the first vacuum chamber and the second vacuum chamber from decreasing even if the length of the optical path is changed during measurement, that is, the emission interference. An object of the present invention is to provide an optical displacement detector that can maintain high detection accuracy without breaking the postures of the mirror and the reflecting mirror.

[0007]

Therefore, according to the present invention, the first vacuum chamber and the second vacuum chamber are used to weaken the resistance force acting in the expansion and contraction direction of the bellows for the vacuum chamber, which occurs when the length of the optical path is changed. It is intended to achieve the above object by applying a pressure to a pressure chamber between the tank and the tank. Specifically, in the optical displacement detector of the present invention, a light emission interference section is provided inside the first vacuum chamber, a reflection mirror is provided inside the second vacuum chamber, and the light emission interference section and the reflection mirror are provided. A bellows for vacuum chamber covering the optical path formed by connecting the first vacuum chamber and the second vacuum chamber by connecting the first vacuum chamber and the second vacuum chamber to each other. A driving device for changing the length of the optical path is provided in the first vacuum tank and the second vacuum tank, and the first vacuum tank and the second vacuum tank are set based on the change in the length of the optical path. An optical displacement detector for detecting a displacement with respect to a tank, wherein a pressure chamber formed between the first vacuum tank and the second vacuum tank and pressure is applied to the pressure chamber. And a pressure control means.

Here, the pressure control means expands and contracts the bellows for the vacuum chamber when the first vacuum chamber and the second vacuum chamber are moved away from each other to change the length of the optical path. A configuration may be used in which a pressure that cancels the resistance force acting in the direction is applied to the pressurizing chamber. Furthermore, the pressure control means includes a pressure sensor that detects the pressure in the pressurizing chamber, and a pressure control valve that controls the pressure applied to the pressurizing chamber based on the pressure value detected by the pressure sensor. It may be configured as. The pressure chamber may be formed between the vacuum chamber bellows and a pressure chamber bellows concentrically arranged on the vacuum chamber bellows. In this case, if the effective area of the vacuum chamber bellows is A ₁ , the effective area of the pressure chamber bellows is A ₂ , and the atmospheric pressure is P ₀ , the command pressure value P ₁ given by the pressure control means is It can be obtained by the formula. _{{(A 2 -A 1) ×} (P 1 -P 0)} - (A 1 × P 0) = 0 P 1 = {(A 1 × P 0) / (A 2 -A 1)} + P 0 = (A ₂ × P ₀ ) /
(A ₂ -A ₁₎

Alternatively, the pressure chamber may be formed by a plurality of pressure chamber bellows symmetrically arranged with the vacuum chamber bellows interposed therebetween. In this case, there are N pressure chamber bellows, the effective area of the vacuum chamber bellows is A ₃ , the effective area of the pressure chamber bellows is A ₄ , and the atmospheric pressure is P _0.
Then, the command pressure value P ₂ given by the pressure control means is obtained by the following equation. _{N × (A 4 × P 2} ) - (A 3 × P 0) = 0 P 2 = (A 3 × P 0) / N × A 4

[0010]

According to the present invention as described above, for the purpose of measurement, the driving device is operated to bring the first vacuum chamber and the second vacuum chamber into close proximity to each other and to separate the optical path between the light emission interference section and the reflecting mirror. Change the length. When pressure is applied to the pressurizing chambers by the pressure control means as the vacuum chambers move toward and away from each other, the resistance force acting between the vacuum chambers in the expansion / contraction direction of the bellows for the vacuum chamber is weakened, and the first vacuum Since the tank and the second vacuum tank are not relatively distorted, high detection accuracy can be maintained. Here, if the pressure exerted by the pressure control means on the pressurizing chamber cancels out the resistance force acting in the expansion / contraction direction of the vacuum chamber bellows, a moment will not be generated in these vacuum chambers, so that higher detection accuracy can be obtained. Can be maintained.

Further, the pressure control means includes a pressure sensor for detecting the pressure in the pressurizing chamber and a pressure control for controlling the pressure applied to the pressurizing chamber to a command pressure value based on the pressure value detected by the pressure sensor. With the valve, the pressure sensor appropriately detects the pressure value of the pressurizing chamber, which changes with the distance between the first vacuum chamber and the second vacuum chamber, and changes the volume of the pressurizing chamber. Regardless of the above, by maintaining the pressure in the pressurizing chamber at a predetermined value (P ₁ or P ₂ ) by the pressure control valve, the resistance force acting between the first and second vacuum chambers can be reliably offset. You can Further, if the pressurizing chamber is formed between the vacuum chamber bellows and the pressurizing chamber bellows arranged concentrically with the vacuum chamber bellows, the pressure for canceling the resistance force can be ensured in the vacuum chamber. Besides, the bellows for a vacuum chamber can be used not only for forming the vacuum chamber but also for forming the pressure chamber, so that the number of parts can be reduced. On the other hand, if the vacuum chamber is formed of a plurality of bellows for pressurizing chambers symmetrically arranged with the bellows for vacuum chamber sandwiched therebetween, the same effect as described above can be achieved, and in addition, the pressurization per Since the size of the chamber bellows is not limited, the pressure bellows and the vacuum bellows can be the same size.

[0012]

Embodiments of the present invention will be described below with reference to the drawings. Here, in each of the embodiments, the same components are designated by the same reference numerals, and the description thereof will be omitted or simplified. FIG. 1 schematically shows the main part of an optical displacement detector according to the first embodiment. In FIG. 1, the optical displacement detector is a length measuring machine that uses a laser interferometer, and has a substantially cylindrical shape that connects the first vacuum chamber 1, the second vacuum chamber 2 and these vacuum chambers 1 and 2. A vacuum chamber 4 including a bellows 3 for a vacuum chamber, a driving device 5 provided outside the first vacuum chamber 1 and the second vacuum chamber 2, and a pressurizing device provided so as to surround the bellows 3 for a vacuum chamber. A chamber bellows 6, a pressure chamber 7 formed between the pressure chamber bellows 6 and the vacuum chamber bellows 3, and air as a working fluid is enclosed in the pressure chamber 7 to apply pressure. The pressure control means 8 is provided.

The first vacuum chamber 1 is fixed to the main body 9 of the apparatus, and a light emission interference section 10 which emits laser light and interferes with the light emission interference section 10 is provided inside thereof. A laser interferometer body (not shown) is provided. The second vacuum chamber 2 is attached to the apparatus main body 9 via the bearing portion 9A so as to be close to and away from the first vacuum chamber 1, and a reflecting mirror 11 is provided inside the second vacuum chamber 1 and is opposite to the reflecting mirror 11. A contactor (not shown) is provided outside the side. The optical path 1 is formed by connecting the reflecting mirror 11 and the light emission interference unit 10.
2 is formed, and this optical path 12 coincides with the axis of the vacuum chamber bellows 3.

The drive unit 5 is a drive motor 13 fixed to the outside of the first vacuum chamber 1, and a drive unit having one end connected to the drive motor 13 and arranged in parallel with the axis of the vacuum chamber bellows 3. And a nut 15 screwed to the driving screw shaft 14 and fixed to the second vacuum chamber 2.
The first vacuum chamber 1 and the second vacuum chamber 2 are configured to be close to and separated from each other so that the length of the optical path 12 is changed. Light path 1
When the length of 2 changes, the displacement of the contact is detected by the laser interferometer. The bellows 6 for the pressurizing chamber is formed in a substantially cylindrical shape whose axis coincides with the axis of the bellows 3 for the vacuum chamber, and both ends of the bellows 6 have a first vacuum tank 1 and a second vacuum tank 2. Are linked to.

The pressure control means 8 includes a first vacuum chamber 1 and a second vacuum chamber 1.
When the length of the optical path 12 is changed by separating the vacuum chamber 2 from the vacuum chamber 2, the resistance force F acting in the expansion and contraction direction of the vacuum chamber bellows 3
Is applied to the pressurizing chamber 7, an air pressure source 16 for sending air as a working fluid to the pressurizing chamber 7, a pressure sensor 17 for detecting the pressure in the pressurizing chamber 7, and this pressure sensor. A pressure control valve 18 for controlling the pressure applied to the pressurizing chamber 7 to a command pressure value P ₁ based on the pressure value detected at 17, and a differential amplifier 19 for sending a control signal to the pressure control valve 18.
This differential amplifier 19 is provided with a command pressure value output circuit 20 for instructing the command pressure value P ₁ . Differential amplifier 19
Is to control the pressure control valve 18 so that the pressure in the pressurizing chamber 7 becomes the command pressure value P ₁ while taking in the pressure value of the pressurizing chamber 7 detected by the pressure sensor 17. Here, if the effective area of the vacuum chamber bellows 3 is A ₁ , the effective area of the pressure chamber bellows 6 is A ₂ , and the atmospheric pressure is P ₀ , the command pressure value P ₁ is obtained by the following equation. . _{{(A 2 -A 1) ×} (P 1 -P 0)} - (A 1 × P 0) = 0 P 1 = {(A 1 × P 0) / (A 2 -A 1)} + P 0 = (A ₂ × P ₀ ) /
(A ₂ -A ₁₎

In the first embodiment having such a structure, the driving device 5 is operated for the measurement, and the first vacuum chamber 1 and the second vacuum chamber 2 are separated from each other by the light emission interference section 10. Reflector 11
When the length of the optical path 12 between and is changed, a resistance force F acts between the vacuum chambers 1 and 2 in the expansion / contraction direction of the vacuum chamber bellows 3. However, the pressure that cancels this resistance F is applied to the pressurizing chamber 7 by the pressure control means 8. That is, the pressure sensor 17 of the pressure control means 8 detects the pressure in the pressurizing chamber 7, and the pressure in the pressurizing chamber 7 is taken in by the differential amplifier 19 while the pressure value in the pressurizing chamber 7 is taken in by the command pressure value P ₁ The pressure control valve 18 is controlled so that

Therefore, according to the first embodiment, the light emission interference portion 10 provided inside the first vacuum chamber 1 and the reflecting mirror 11 provided inside the second vacuum chamber 2 are connected. The formed optical path 12 is covered with a bellows 3 for a vacuum chamber, and a driving device 5 is provided outside the vacuum tanks 1 and 2 for changing the length of the optical paths 12 by separating these vacuum tanks 1 and 2 from each other. 12
In an optical displacement detector that detects displacement based on a change in the length of the pressure chamber 7, a pressure chamber 7 formed between the vacuum chambers 1 and 2 and a pressure control means for applying pressure to the pressure chamber 7. 8
And the resistance force acting in the expansion and contraction direction of the vacuum chamber bellows 3 between the vacuum chambers 1 and 2 is weakened,
Since the first vacuum chamber 1 and the second vacuum chamber 2 are relatively less distorted, high detection accuracy can be maintained. Further, since the pressure applied to the pressurizing chamber 7 by the pressure control means 8 cancels the resistance force acting in the expansion and contraction direction of the vacuum chamber bellows 3, moments may be generated in these vacuum chambers 1 and 2. Therefore, higher detection accuracy can be maintained.

Further, the pressure control means 8 includes a pressure sensor 17 for detecting the pressure in the pressurizing chamber 7, and the pressure sensor 17
The pressure control valve 18 for controlling the pressure applied to the pressurizing chamber 7 to the command pressure value P ₁ on the basis of the pressure value detected in 1. And the first vacuum chamber 1 in addition to being able to be applied to the second vacuum chambers 1 and 2.
The pressure value of the pressurizing chamber 7 that changes with the distance between the second vacuum chamber 2 and the second vacuum chamber 2 is properly detected by the pressure sensor 17, and the pressure control valve 18 is activated based on the properly detected pressure value. Since the pressure is controlled regardless of the volume change in the pressure chamber 7, the first
Also, the resistance force acting between the second vacuum chambers 1 and 2 can be canceled out with certainty. Further, in the first embodiment, the pressurizing chamber 7
Is formed between the vacuum chamber bellows 3 and the pressurizing chamber bellows 6 concentrically arranged on the vacuum chamber bellows 3, the pressure for canceling the resistance force F is set to the first and the second. In addition to being surely applied to the vacuum chambers 1 and 2, the number of parts can be reduced by using the vacuum chamber bellows 6 not only for forming the vacuum chamber 4 but also for forming the pressurizing chamber 7. .

Next, a second embodiment of the present invention will be described with reference to FIG. The second embodiment is different from the first embodiment in the structure of the pressurizing chamber, and the other structures are the same as those in the first embodiment. FIG. 2 shows an outline of a main part of an optical displacement detector according to the second embodiment. In FIG. 2, the optical displacement detector includes the vacuum chamber 4 including the first vacuum chamber 1, the second vacuum chamber 2, and the vacuum chamber bellows 3, the driving device 5, and the vacuum chamber. A plurality of pressure chamber bellows 26, two in FIG. 2, which are symmetrically arranged with the bellows 3 interposed therebetween,
The pressure chamber 27 is formed from the space of the bellows 26 for pressure chamber, and the pressure control means 8 for applying pressure to the pressure chamber 27. The light emission interference unit 10 is provided inside the first vacuum chamber 1.
A laser interferometer body (not shown) is provided on the outside opposite to 0. A reflecting mirror 11 is provided inside the second vacuum chamber 2, and a contactor (not shown) is provided outside the reflecting mirror 11 on the opposite side. The reflecting mirror 11 and the light emission interference unit 10
The optical path 12 is formed by connecting with.

The pressure control means 8 includes a first vacuum chamber 1 and a second vacuum chamber 1.
When the length of the optical path 12 is changed by separating the vacuum chamber 2 from the vacuum chamber 2 and the resistance force F acting in the expansion / contraction direction of the bellows 3 for the vacuum chamber.
Is applied to the pressurizing chamber 27, and the command pressure value P ₂ is supplied to the air pressure source 16, the pressure sensor 17, the pressure control valve 18, the differential amplifier 19, and the differential amplifier 19. This is a configuration including a command pressure value output circuit 20 for instructing. Here, the effective area of the vacuum chamber bellows 3
And A _3, the effective area of the pressurizing chamber bellows 26 and A _4, if the atmospheric pressure and P _0, the command pressure value P ₂ is determined by the following equation. _{2 × (A 4 × P 2} ) - (A 3 × P 0) = 0 P 2 = (A 3 × P 0) / 2 × A 4

Therefore, according to the second embodiment, in addition to achieving the same effects as in the first embodiment, the vacuum chamber 27
Is formed from a plurality of pressure chamber bellows 26 symmetrically arranged with the vacuum chamber bellows 3 interposed therebetween, the same effect as that of the first embodiment can be achieved, and one pressure chamber is provided. Since the size of the use bellows 26 is not limited, the pressure bellows 26 and the vacuum bellows 3 can have the same size.

Next, a third embodiment of the present invention will be described with reference to FIG. The third embodiment is different from the first embodiment in the structure of the pressure control means, and the other structures are the same as those in the first embodiment. FIG. 3 schematically shows an optical displacement detector according to the third embodiment. In FIG. 3, the optical displacement detector includes a first vacuum chamber 1, a second vacuum chamber 2, and a vacuum chamber 4 including a vacuum chamber bellows 3 and a first vacuum chamber 4.
Drive device 5 provided outside the vacuum chamber 1 and the second vacuum chamber 2, the pressure chamber bellows 6 provided so as to surround the vacuum chamber bellows 3, and the pressure chamber bellows. 6 and the pressure chamber 7 formed between the vacuum chamber bellows 3 and a pressure control means 38 for enclosing air in the pressure chamber 7 to apply pressure.

The pressure control means 38 decompresses the pressure gauge 31 for detecting the pressure in the pressurizing chamber 7, the air pressure source 16 and the air pressure sent from the air pressure source 16 to the pressurizing chamber 7 in the first embodiment. And a precision pressure reducing valve 32 that applies a pressure of the same pressure value P ₁ . Therefore, according to the third embodiment, it is possible to achieve the same effect as that of the first embodiment.

Next, a fourth embodiment of the present invention will be described with reference to FIG. The fourth embodiment is a more specific example of the third embodiment, and the basic configuration is the same as that of the third embodiment. FIG. 4 schematically shows an optical displacement detector according to the fourth embodiment. In FIG. 4, the optical displacement detector includes the vacuum chamber 4 including the first vacuum chamber 1, the second vacuum chamber 2, and the vacuum chamber bellows 3, the first vacuum chamber 1 and the second vacuum chamber 1. Driving device 5 provided outside the vacuum chamber 2, the pressure chamber bellows 6 provided so as to surround the vacuum chamber bellows 3, the pressure chamber bellows 6 and the vacuum chamber bellows 3. The pressurizing chamber 7 formed between
And the pressure control means 38 for enclosing air in the pressurizing chamber 7 and applying a pressure thereto.

Inside the first vacuum chamber 1, the light emission interference section 1 is provided.
0 is provided, and the laser interferometer main body 41 is provided outside the light emission interference unit 10. This laser interferometer main body 41 is provided with a laser light source (not shown) and an optical fiber 42.
Laser light is sent through. The first vacuum chamber 1 is attached to the apparatus main body 9 via a bracket 43,
The bracket 43 pivotally supports both ends of the drive screw shaft 14, and the drive motor 13 for rotationally driving the drive screw shaft 14 is fixed to the end of the bracket 43. The second vacuum chamber 2 is attached to the apparatus main body 9 via the bearing portion 9A so as to be able to approach and separate from the first vacuum chamber 1, and the reflecting mirror 11 is provided therein. This reflector 11
A contact 44 is provided on the outside opposite to the contact 44.
4 is opposed to the measurement table 45.

The optical path 12 is formed by connecting the reflecting mirror 11 and the light emission interference section 10. The optical path 12 coincides with the axis of the vacuum chamber bellows 3. The vacuum chamber 4 is connected to a vacuum device 46, and the vacuum device 46 is composed of a vacuum pump 47 for sucking the vacuum chamber 4, an opening / closing valve 48, and a vacuum gauge 49. Therefore, according to the fourth embodiment, it is possible to achieve the same effect as that of the third embodiment.

The present invention is not limited to the above-described embodiments, but includes the following modifications as long as the object of the present invention can be achieved. For example, in each of the above embodiments, the optical displacement detector is applied to a length measuring machine using a laser interferometer, but in the present invention, the first vacuum chamber 1 and the second vacuum chamber 2 are separated from each other. If it changes the length of the optical path 12 by means of the above, it can be applied to a displacement detector using a device other than the laser interferometer, for example, a refractive index measuring device. Further, the working fluid used in the pressure control means 8, 38 may be a liquid such as water or oil.

In each of the above embodiments, the pressure applied by the pressure control means 8 and 38 to the pressurizing chamber 7 is made equal to the resistance force F. However, the pressure applied by the pressure control means 8 to the pressurizing chamber 7 is the resistance. It may be larger or smaller than the force F. Furthermore, in each of the above-described embodiments, the configuration of the driving device 5 is not limited to the feed screw mechanism, and another configuration, for example, a motor to which a pinion is attached is fixed to the outside of the first vacuum chamber 1. The rack that meshes with the pinion may be fixed to the second vacuum chamber 2, or the bearing 9
A linear motor arranged at A may be used. Further, the bearing portion 9A may be an air bearing other than the ball bearing.

[0029]

As described above, according to the optical displacement detector of the present invention, the light emission interference portion provided inside the first vacuum chamber and the inside of the second vacuum chamber are provided. Cover the optical path formed by connecting the reflective mirror with a vacuum chamber bellows,
An optical displacement detector that detects the displacement based on the change in the length of the optical path is provided with a driving device outside the vacuum tank that separates these vacuum tanks from each other and changes the length of the optical path. Since a pressure chamber formed between the pressure chamber and the pressure control means for applying pressure to the pressure chamber is provided, the resistance force acting in the expansion / contraction direction of the vacuum chamber bellows is weakened between these vacuum chambers. Since the first vacuum chamber and the second vacuum chamber are relatively less distorted, the geometrical relationship between the first vacuum chamber and the second vacuum chamber is maintained even if the optical path length is changed during measurement. It is possible to maintain high detection accuracy without lowering the accuracy, that is, without losing the postures of the light emission interference unit and the reflecting mirror.

[Brief description of drawings]

FIG. 1 is a schematic view of a main part of an optical displacement detector according to a first embodiment of the present invention.

FIG. 2 is a schematic view of a main part showing an optical displacement detector according to a second embodiment of the present invention.

FIG. 3 is a schematic configuration diagram showing an optical displacement detector according to a third embodiment of the present invention.

FIG. 4 is a schematic configuration diagram showing an optical displacement detector according to a fourth embodiment of the present invention.

FIG. 5 is a schematic view of a main part showing a conventional optical displacement detector.

[Explanation of symbols]

 1 1st vacuum tank 2 2nd vacuum tank 3 Bellows for vacuum chambers 5,35 Driving device 6,26 Bellows for pressurization chambers 7,27 Pressurization chambers 8,38 Pressure control means 10 Light emission interference part 11 Reflector 12 Optical path 17 Pressure sensor 18 Pressure control valve

Claims (5)

[Claims] 1. A light emission interference section is provided inside a first vacuum chamber,
A bellows for a vacuum chamber covering a light path formed by connecting the light emission interference section and the reflecting mirror is provided inside the second vacuum tank, and the bellows for the vacuum chamber are provided as the first vacuum tank and the second vacuum tank. A driving device that is connected to the first vacuum chamber and the second vacuum chamber to change the length of the optical path by separating the first vacuum chamber and the second vacuum chamber from each other. An optical displacement detector for detecting a displacement between the first vacuum chamber and the second vacuum chamber based on a change in the length of the optical path, wherein the first vacuum chamber and the second vacuum chamber are provided. An optical displacement detector comprising: a pressure chamber formed between the pressure chamber and a pressure control unit for applying pressure to the pressure chamber. 2. The optical displacement detector according to claim 1, wherein the pressure control means includes the first vacuum chamber and the second vacuum chamber.
When the length of the optical path is changed by moving the vacuum chamber close to and away from the vacuum chamber, a pressure that cancels the resistance force acting in the expansion and contraction direction of the vacuum chamber bellows is applied to the pressurizing chamber. Optical displacement detector. 3. The optical displacement detector according to claim 1 or 2, wherein the pressure control means is based on a pressure sensor for detecting the pressure in the pressurizing chamber and a pressure value detected by the pressure sensor. An optical displacement detector, comprising: a pressure control valve that controls the pressure applied to the pressurizing chamber to a command pressure value. 4. The optical displacement detector according to claim 1, wherein the pressurizing chamber comprises a bellows for the vacuum chamber and a pressurizing chamber concentrically arranged on the bellows for the vacuum chamber. An optical displacement detector formed between a room bellows. 5. The optical displacement detector according to claim 1, wherein the pressure chamber comprises a plurality of pressure chamber bellows symmetrically arranged with the vacuum chamber bellows interposed therebetween. An optical displacement detector characterized by being formed.