JP6682097B2 - Optical interference length measuring device - Google Patents

Description

  The present invention relates to an optical interference length measuring device having an optical system that suppresses stray light and multiplexed light.

There is a measuring device in which mirrors are provided at one end and the other end of the object to be measured, laser light is irradiated from these light sources to these mirrors, and the length of the object to be measured is measured by using the light reception result of the reflected light.
In such a measuring device, the temperature of the space in which the measured object is located is changed, and the expansion coefficient of the measured object is measured from the length before the change and the length after the change.

In such a measuring device, the beam splitter is positioned in the horizontal direction with respect to the light source and the light receiving unit, and two mirrors that are in contact with the ends of the object to be measured are provided on the emission side of the beam splitter.
Light from a light source enters a plate (plate-shaped) beam splitter, is separated by the plate beam splitter and is emitted to two mirrors, and the reflected light from the two mirrors is combined by the plate beam splitter to generate a combined light (interference). Light), and the combined wave is received by the light receiving section. The measurement device, for example, based on the light reception result of the combined light in the light receiving unit, by the optical interference method, by measuring the amount of change in the distance of the measurement target according to the temperature change, thermal expansion Measure the rate.

  However, in the above-described conventional measurement device, unnecessary light such as stray light and light of the third order or more generated by the light from the light source reflected on the inner surface in the plate beam splitter is emitted from the plate beam splitter, Finally, the object to be measured is irradiated, and multiple interference occurs in the synthetic wave, which causes a problem that high measurement accuracy cannot be obtained.

  The present invention has been made in view of the above circumstances, and an object thereof is to suppress the influence of unnecessary light such as third-order light and stray light generated in a beam splitter, and to measure the length of an object to be measured with high accuracy. It is to provide a measuring device.

In order to solve the problems of the above-mentioned conventional techniques and achieve the above-mentioned object, the measuring device of the present invention is a measuring device that measures the distance between the reference surface and the surface to be inspected or the amount of change in the distance. A light source and a first light splitting surface that transmits a part of the second light of the first light from the light source in the first direction and reflects the remaining third light. And a first optical means that is a trapezoidal beam splitter that reflects the third light toward the first direction on a first surface parallel to the first light splitting surface; and the first optical means. enters the second light and the third light from the unit, one of the light of the second light and the third light reflected toward the reference surface, wherein the said one light The fourth light, which is the reflected light on the reference surface, is emitted to the first optical means, and the other light of the second light and the third light is forwarded. Second optical having a second light splitting surface that reflects toward the surface to be inspected and emits fifth light, which is the reflected light of the other light on the surface to be inspected, to the first optical means. Means and a light receiving means, the first optical means is formed integrally with the second optical means, and the reflected light on the first surface of the third light is generated. It is configured such that it does not enter the first light splitting surface, and that it enters the second light splitting surface only through the integrated first optical means and second optical means. cage, said first beam splitting surface reflects one of said fourth light and the fifth light from said second optical means, and transmits the other, the said fourth optical fifth Light is generated, and the light receiving means receives the combined light.

According to this configuration, the first optical means is configured such that the reflected light of the third light on the first surface does not enter the first light splitting surface. It is possible to prevent the three lights from being further reflected in the first optical means and causing ghost, stray light, tertiary light, and misalignment.
Accordingly, the distance between the reference surface and the surface to be inspected or the amount of change in the distance can be measured with high accuracy. The measuring device of the present invention can measure the thermal expansion of the measured object placed between the reference surface and the surface to be measured by measuring the change in the distance according to the temperature change.
Further, according to this configuration, by integrally forming the first optical means and the second optical means, the number of components can be reduced, alignment adjustment can be facilitated, and stray light and tertiary light can be eliminated. It can be eliminated almost completely. Further, it is possible to substantially completely eliminate the measurement error due to the positional relationship between the first optical means and the second optical means being displaced.

  Suitably, the said 1st optical means of the measuring apparatus of this invention is parallel to the said 1st light separation surface and the said 1st surface, and the said 1st light separation surface and the said 1st light and The angle between the ray of the second light and the light ray is 45 °, the incident direction of the first light to the first optical means and the first direction are parallel to each other, and The fourth light that has entered the first optical means from the optical means enters the first surface without entering the first light splitting surface.

  Suitably, the said 2nd optical means of the measuring apparatus of this invention has a 2nd light separation surface, a 2nd surface, and a 3rd surface, The said 2nd light is the said 2nd light. The fourth light, which is reflected by the light separation surface toward the surface to be inspected, is the reflected light of the second light, is transmitted toward the second light separation surface, and the fourth light is transmitted. The reflected light from the second surface and the third surface is transmitted with the second light separating surface facing the surface to be inspected, and the reflected light on the surface to be inspected is reflected by the second light separating surface. The third light is reflected toward the first optical means, the third light is reflected toward the reference surface at the second light splitting surface, and the fifth light is reflected light of the third light. Is transmitted toward the second light separation surface, and reflected light of the fifth light on the second surface and the third surface is transmitted through the second light separation surface toward the reference surface. In the said reference plane The reflected light is reflected toward the first optical means at said second beam splitting surface.

  Preferably, the measuring device of the present invention has a holding means for holding the reference surface and the surface to be inspected so that the direction in which light is incident is the direction of gravity, and the light source is the first light in the horizontal direction. And the light receiving means receives the combined light from the horizontal direction.

  According to this configuration, by causing the gravity direction and the distance measurement direction to coincide with each other, a measurement error occurs due to the holding means that holds the reference surface and the surface to be inspected tilts or bends due to gravity. It is possible to avoid the above and perform highly accurate measurement.

  Suitably, the measuring device of the present invention further comprises an arithmetic means for calculating the distance or the variation based on the light reception result of the light receiving means.

  According to the present invention, it is possible to provide a measuring device capable of measuring the length of an object to be measured with high accuracy by suppressing the influence of unnecessary light such as third-order light and stray light generated in the beam splitter.

FIG. 1 is an external perspective view of a measuring device according to an embodiment of the present invention. FIG. 2 is a side view of the measuring device shown in FIG. FIG. 3 is a cross-sectional view taken along the line AA shown in FIG. FIG. 4 is an enlarged perspective view of the vicinity of the upper mirror support portion and the oil tank shown in FIG. FIG. 5 is a schematic cross-sectional view of a cross section passing through the central axis of the upper mirror support portion shown in FIG. FIG. 6 is a perspective view of the portion shown in FIG. 4 seen from below. FIG. 7 is a diagram for explaining the optical system of the measuring apparatus shown in FIG. FIG. 8 is a diagram for explaining a modified example of the optical system shown in FIG. FIG. 9 is a view for explaining the action of the model when vibration is applied to the measuring device shown in FIG. FIG. 10 is a cross-sectional configuration diagram for explaining the heat retaining mechanism of the measuring device shown in FIG. FIG. 11 is an enlarged cross-sectional configuration diagram of a contact portion of the upper mirror support portion 9 of the first heat conduction portion shown in FIG. FIG. 12 is a functional block diagram of the temperature control (heat retention) mechanism of the measuring device shown in FIG. FIG. 13: is a figure which shows the temperature of the 1st area | region in which a to-be-measured object is located, and the external temperature of a measuring device on a time-axis.

Hereinafter, a measuring device according to an embodiment of the present invention will be described.
The measuring device of the present embodiment is an optical interference length measuring device for measuring the length between the reference surface and the surface to be inspected by interfering the light irradiated to the reference surface and the surface to be inspected, respectively. .
FIG. 1 is an external perspective view of a measuring device 1 according to an embodiment of the present invention. FIG. 2 is a view of the measuring device 1 shown in FIG. 1 as seen from the side surface direction. FIG. 3 is a sectional view taken along a sectional line AA shown in FIG.

As shown in FIG. 1, in the measuring apparatus 1, the second base 13 is fixed on the first base 11 by three columns.
Three oil tanks 31 (1), 31 (2), 31 (3) are fixed to the second base 13 at equal intervals in the circumferential direction.

Further, as shown in FIG. 3, a buffer solution is stored in the oil tanks 31 (1), 31 (2), 31 (3).
Floating bodies 21 (1), 21 (2), 21 (3) are respectively floated in the buffer solutions of the oil tanks 31 (1), 31 (2), 31 (3).

The floating bodies 21 (1), 21 (2), and 21 (3) are connected to the upper mirror support portion 9 (an example of the first supporting portion of the present invention) via the disc 17 (an example of the first member of the present invention). ) Is fixed.
A ring-shaped member 27 (an example of the second member of the present invention) is provided on the outer side of the circular plate 17 via a leaf spring 25 (an example of the elastic member of the present invention).
The ring-shaped member 27 is connected to the ring-shaped member 29 located therebelow by three columns.
The disc 15 is fixed to the inside of the ring-shaped member 29 via a leaf spring 23. The upper mirror support portion 9 is fixed to the center of the disk 15.

Further, the disc 15 is formed with a hole for installing the oil tank 31 (1), 31 (2), 31 (3).
Slide guides 33 (1) and 33 (2) are fixed to two opposing positions on the outer periphery of the ring-shaped member 29.
Further, the second base 13 is provided with slide guide fixing columns 39 (1), 39 (2) at positions facing the slide guides 33 (1), 33 (2).
The slide guides 33 (1) and 33 (2) guide the movement of the ring-shaped member 29 in the direction of gravity (an example of the optical axis direction of the present invention).

By thus providing the slide guides 33 (1) and 33 (2), the horizontal movement and inclination of the upper mirror support portion 9 are restricted, so that the upper mirror 51 is appropriately moved along the direction of gravity. it can. As a result, the upper mirror 51 does not shake in the horizontal direction, and highly accurate measurement is possible.
In the measuring device 1, the coarse movement of the upper mirror support portion 9 is suppressed by the slide guides 33 (1) and 33 (2), and the fine movement of the upper mirror support portion 9 is suppressed by the leaf springs 25 and 23.

As shown in FIG. 3, an upper mirror 51 (an example of the test surface of the present invention) is fixed in the upper mirror support portion 9 (first support) of the cylindrical body. The reflecting surface of the upper mirror 51 is located on the optical section 41 side.
Inside the upper mirror support portion 9, a lower mirror support portion 53 fixed to the second base 13 is installed without contacting the upper mirror support portion 9. A lower mirror 55 (an example of the reference surface of the present invention) is fixed to the lower mirror support portion 53. The lower mirror support portion 53 has a cylindrical shape. The reflecting surface of the lower mirror 55 is located on the upper mirror 51 side.

Further, an optical portion 41 is fixed to a lower portion of the second base 13 at a position facing the upper mirror support portion 9.
A light source 151 and a light receiving section 153 are provided on the first base 11. The light source 151 and the light receiving unit 153 are provided at the same height as the optical unit 41 in the gravity direction.

The light source 151 is a linearly polarized laser light source, and emits light (laser light) toward the optical unit 41 in the horizontal direction. Highly accurate distance measurement becomes possible by using a laser beam having a short wavelength.
The light receiving unit 153 is a CCD sensor including a plurality of light receiving elements, and receives the light (combined light) from the optical unit 41.

Further, the measuring device 1 has a calculation unit 35.
The calculation unit 35 calculates the distance between the upper mirror 51 and the lower mirror 55, that is, the length of the measurement target 7 based on the light reception result of the optical unit 41. Specifically, the calculation unit 35 calculates by the Michelson interferometry method based on the light reception result, calculates the movement amount of the interference fringes, and calculates the expansion amount of the measured object 7 based on the movement amount.

The measuring device 1 has a reserve tank 61.
The reserve tank (an example of the second tank of the present invention) 61 has a buffer solution between it and the oil tanks 31 (1), 31 (2), 31 (3) (an example of the first tank of the present invention). It has a flow path and stores a larger amount of buffer solution than the oil tanks 31 (1), 31 (2), 31 (3). The buffer solution is, for example, silicone oil.

  According to this configuration, the oil tanks 31 (1), 31 (2), 31 (3) and the reserve tank 61 have the same liquid level of the buffer solution. Therefore, even if the temperature of the buffer solution stored in the oil tanks 31 (1), 31 (2), 31 (3) near the object to be measured 7 changes, the buffer solution stored in the reserve tank 61 cannot be changed. If the temperature does not change, it is possible to suppress the increase in the liquid level due to the expansion of the buffer solution in the oil tanks 31 (1), 31 (2), 31 (3). As a result, the positions of the floating bodies 21 (1), 21 (2), 21 (3) in the oil tanks 31 (1), 31 (2), 31 (3) in the direction of gravity can be made constant, and the influence of temperature changes It is possible to perform stable and highly accurate measurement without being affected.

FIG. 7 is a diagram for explaining an optical system of the measuring device 1 according to the embodiment of the present invention.
As shown in FIG. 7, in the measuring device 1, the measured object 7 is sandwiched and held by the upper mirror 51 and the lower mirror 55 located at different positions in the gravity direction (vertical direction in FIG. 7). The measuring device 1 measures the distance of the object 7 to be measured in the direction of gravity or its change.

As shown in FIG. 7, the light source 151, the light receiving unit 153, and the optical unit 41 are provided at the same height in the gravity direction, and the measurement target 7 is held above the optical unit 41.
In the optical unit 41, the first optical unit 411 and the second optical unit 413 are integrally molded.
The first optical unit 411 is a polarization-independent trapezoidal beam splitter.
The first optical unit 411 transmits L1 part of the second light L2 of the first light from the light source 151 in the first direction X1 and transmits the remaining third light L31 in the Y2 direction. It has the 1st light separation surface 411a which reflects and reflects. The first light splitting surface 411a is a half mirror.
Further, the first optical unit 411 has a first surface S1 that reflects the third light L31 reflected by the first light separation surface 411a toward the X1 direction.

The first optical unit 411 is configured so that the reflected light of the third light L31 on the first surface S1 does not enter the first light separation surface 411a. The first light separation surface 411a transmits the fifth light L55 from the second optical unit 413 and emits the combined light L6 obtained by reflecting the fourth light L46 toward the light receiving unit 153. .
The light receiver 153 receives the combined light L6.

In the first optical unit 411, the first light separation surface 411a and the first surface S1 are parallel to each other. The angle between the first light splitting surface 411a and the light rays of the first light L1 and the second light L21 is 45 °.
The incident direction of the first light L1 from the light source 151 on the incident surface S11 is parallel to the horizontal direction (X1-X2: first direction).
The fourth light L45 that has entered the first optical unit 411 from the second optical unit 413 does not enter the first light splitting surface 411a and enters the first surface S1.

The second optical unit 413 has a second light splitting surface 413a that reflects the second light L2 from the first optical unit 411 toward the upper mirror 51 as the second light L21. The second light splitting surface 413a is a polarization beam splitter.
The quarter-wave plate 415 located above the second optical unit 413 converts linearly polarized light of the passing light into circularly polarized light and converts circularly polarized light of the passing light into linearly polarized light.
The second light L21 passes through the quarter-wave plate 415, is converted into circularly polarized light, is reflected by the upper mirror 51, and the reflected fourth light L41 passes through the quarter-wave plate 415. Then, the light is converted into linearly polarized light whose polarization axis is orthogonal to L21, is transmitted through the second light separation surface 413a, and is incident on the second surface S2 of the second optical unit 413.
The fourth light L41 is reflected by the second surface S2 toward the third surface S3 as the fourth light L42, and the fourth light L43 which is the reflected light on the third surface S3 is the second light L42. The light is transmitted through the light separation surface 413 a, passes through the quarter-wave plate 415, is converted into circularly polarized light, and is incident on the upper mirror 51.
The fourth light L43 is reflected by the upper mirror 51, and the reflected fourth light L44 passes through the quarter-wave plate 415 and is converted into linearly polarized light whose polarization axis is orthogonal to that of L43. The second light splitting surface 413a is reflected as the fourth light L45 toward the first optical unit 411.

The second light splitting surface 413a reflects the third light L32 from the first optical unit 411 toward the lower mirror 55 as third light L33.
The third light L33 passes through the quarter-wave plate 415, is converted into circularly polarized light, is reflected by the lower mirror 55, and the reflected fifth light L51 passes through the quarter-wave plate 415. Then, it is converted into linearly polarized light whose polarization axis is orthogonal to L33, is transmitted through the second light separation surface 413a, and is incident on the third surface S3 of the second optical unit 413.

The fifth light 51 is reflected by the third surface S3 toward the second surface S2 as the fifth light L52, and the fifth light L53 which is the reflected light on the second surface S2 is the second light L52. The light is transmitted through the light separation surface 413a, passes through the quarter-wave plate 415, is converted into circularly polarized light, and is incident on the lower mirror 55.
The fifth light L53 is reflected by the lower mirror 55, and the reflected fifth light L54 passes through the quarter-wave plate 415 and is converted into linearly polarized light whose polarization axis is orthogonal to that of L53. The second light splitting surface 413a is reflected as the fifth light L55 toward the first optical unit 411.

  According to the configuration of the optical unit 41 illustrated in FIG. 7, in the first optical unit 411, the third light L32, which is the reflected light of the third light L31 on the first surface S1, is converted into the first light separation surface. Since it is configured so as not to enter the 411a, it is possible to prevent the ghost, stray light, tertiary light, and misalignment from occurring due to the third light L32 being further reflected in the first optical unit 411.

This makes it possible to measure the distance between the upper mirror 51 and the lower mirror 55 or the amount of change in the distance with high accuracy.
In addition, the measuring device 1 can measure the thermal expansion of the measured object 7 installed between the upper mirror 51 and the lower mirror 55 by measuring the change in the distance according to the temperature change.

Between the optical path length between the second light L2 separated by the first light separation surface 411a and the upper mirror 51, and the optical path length between the third light L31 and the lower mirror 55 is measured. There is an optical path difference that is four times the length of the object 7, and when the object to be measured 7 thermally expands and the length changes, the optical path difference also changes.
Further, the striped pattern generated in the sixth light L6 (combined light) by causing the fourth light L46 and the fifth light L55 to interfere with each other on the first light separation surface 411a moves due to the change in the optical path difference. To do. The calculation unit 35 detects the thermal expansion coefficient of the measurement target 7 by detecting the movement amount from the light reception result of the light reception unit 153.

According to the configuration of the optical unit 41 shown in FIG. 7, the number of components can be reduced by integrally forming the first optical unit 411 and the second optical unit 413, and alignment adjustment of the optical path length can be easily performed. Therefore, stray light and third-order light can be almost completely eliminated.
This is possible by using a trapezoidal beam splitter as the first optical unit 411. In the past, since a plate-shaped beam splitter was used, it could not be integrated.

  In the example shown in FIG. 7, the first optical unit 411 and the second optical unit 413 are integrally molded, but they may be separated as shown in FIG.

  Further, according to the configuration of the optical unit 41 shown in FIG. 7, the object to be measured 7 held between the upper mirror 51 and the lower mirror support portion 53 is made to match the gravity direction and the distance measuring direction. It is possible to avoid a measurement error caused by tilting or bending due to gravity, and to perform highly accurate measurement.

Hereinafter, the buffer mechanism of the measuring device 1 will be described in detail.
As described above, in the measuring apparatus 1, as shown in FIG. 3, the floating bodies 21 (1), 21 (, 21 (1), 21 (1), 21 (1), 21 (1), 21 (3) 2) and 21 (3) are floating.
The upper mirror support portion 9 and the upper mirror 51 move in the gravity direction (Y1-Y2 direction) integrally with the floating bodies 21 (1), 21 (2), 21 (3).

That is, the upper mirror 51 floats in the buffer solution while being in contact with the upper portion of the measured object 7.
Further, if it simply floats, tilting or parallel movement occurs with the upper part of the measured object 7 as a fulcrum, so the slide guides 33 (1) and 33 (2) cause the ring-shaped member 29 and the ring-shaped member. The movement of the member 27 (upper mirror 51) in the direction of gravity is guided. At this time, due to the combination of the leaf spring 25 and the leaf spring 23 (parallel movement spring) shown in FIG. 4 and the like, tilting and parallel movement do not occur, and the upper mirror 51 moves only in the gravity direction (vertical direction).

In the measuring apparatus 1, when vibration from the installation surface is applied to the first base 11, the vibration is transmitted to the lower mirror support portion 53, the measurement target 7, and the lower mirror 55 via the second base 13.
Here, since the upper mirror 51 is only in a state of floating in the buffer solution, the upper mirror 51 is in the same vibration state as the lower mirror 55 through the measured object 7. As a result, in the calculation of the distance to the object 7 to be measured (upper mirror optical path length-lower mirror optical path length), the effects of vibration cancel each other out, and the results are not affected.
Further, since silicon oil, which is a viscous fluid, is used as the buffer solution for floating the upper mirror 51, there is the effect of reducing the vibration itself due to the damping effect of the oil.

FIG. 9 is a diagram for explaining the operation when vibration is applied to the measuring device 1 shown in FIG.
In FIG. 9, “A0” indicates the optical path length 55 (L) in the gravity direction from the surface of the second base 13 to the lower mirror 55. Further, “B0” indicates the optical path length 51 (L) in the gravity direction from the surface of the second base 13 to the upper mirror 51.

When the second base 13 vibrates and the lower mirror 55 moves by δA in the direction of gravity, the following expressions (1) and (2) are established.
[Equation 1]
Optical path length 55 (L) = A0 + δA (1)

[Equation 2]
Optical path length 51 (L) = B0 + δA (2)

  The distance between the upper mirror 51 and the lower mirror 55 (measurement distance of the measured object 7) is “optical path length 51 (L) −optical path length 55 (L)”, and the following expression (3) is established.

[Equation 3]
Optical path length 51 (L) -optical path length 55 (L) = (A0 + δA)-(B0 + δA) = A0-B0 (3)

That is, it is not affected by δA.

  Incidentally, conventionally, the mirrors are held horizontally, and each mirror is supported in a cantilever manner. When vibration is applied, each cantilever tip is excited independently so that it swings. The effects of vibration are different for the two mirrors. Therefore, the influence of the vibration remains on the measurement result of the measurement target. Not only the length of the object to be measured may be affected, but also the direction of inclination to the direction of gravity may be affected.

In the measuring apparatus 1, for example, the static movement amount (mm level) when attaching the measured object 7 to the upper mirror 51 and the lower mirror 55 is guided by the slide guides 33 (1) and 33 (2), The upper mirror support portion 9 integrally moves with the ring-shaped member 27 and the like and vertically moves as a whole.
Also, small dynamic vibrations of the μm to nm level when measuring the length of the object 7 to be measured are absorbed and damped by the spring properties of the leaf springs 23 and 25 and the damping effect of the oil damper.

According to this configuration, both rotation and parallel movement of the upper mirror support portion 9 are restrained, and the elastic deformation of the leaf springs 23 and 25 causes the inner disks 15 and 17 and the upper mirror support portion 9 to move in parallel only in vertical movement. To do.
Since the static elongation (measurement target) of the measured object 7 due to thermal expansion is an extremely small amount, the plate springs 23 and 25 are elastically deformed by an extremely small amount while floating on the surface of the buffer solution. The vertical movement of the inner parts of 23 and 25 is not hindered.

Hereinafter, the temperature control (heat retention) mechanism of the measuring device 1 will be described.
FIG. 10 is a cross-sectional configuration diagram for explaining the temperature control (heat retention) mechanism of the measuring device 1 shown in FIG.
The measuring apparatus 1 has a first temperature control unit 73 that heats a first region 71 in which the measured object 7 held between the upper mirror 51 and the lower mirror 55 is located.
The first temperature control unit 73 has a first heat conduction unit 81 (labyrinth shield) that forms the first region 71 therein, and a Peltier element 83 located outside thereof.
A first region 71 is formed inside the cylindrical upper mirror support portion 9.

  A second region 93 is formed so as to surround the first region 71. The temperature of the second region 93 is adjusted by the liquid flowing through the heat sink (circulation path) 95. The measuring apparatus 1 has a second temperature control unit 173 that controls the heat sink 95 to adjust the temperature of the second region 93.

According to this configuration, since the second temperature control unit 173 adjusts the temperature of the second region 93 formed so as to surround the first region 71, the first region 71 in which the measurement target 7 is located is located. It is possible to suppress a sudden temperature change. The second area 93 is a constant temperature bath.
Further, since the first temperature control unit 73 controls the temperature by heating the first region 71 with the Peltier device 83, the temperature fluctuation caused in the second region 93 by the temperature control by the second temperature control unit 173. Can be controlled with high responsiveness.
Thereby, the temperature control of the first region 71 in which the measured object 7 is located can be performed with high accuracy.

Below the first area 71 and the second area 93, an opening is formed through which the upper mirror support portion 9 and the lower mirror support portion 53 are inserted (located inside).
Light from the light source 151 located outside the first region 71 and the second region 93 is applied to the upper mirror 51 and the lower mirror 55 through the opening, and the reflected light is received by the light receiving unit 153. Is emitted.

FIG. 11 is an enlarged cross-sectional configuration diagram of a contact portion of the first heat conducting portion 81 shown in FIG. 10 with the upper mirror support portion 9.
As shown in FIG. 11, the first heat conduction portion 81 forming the first region 71 is provided in the contact portion with the upper mirror support portion 9 with respect to the traveling direction of light which is the gravity direction (Z1-Z2 direction). And has a plurality of spatial regions 121a and 121b provided at predetermined intervals.

The edges of the openings of the space regions 121a and 121b are in contact with the outer peripheral surface of the upper mirror support portion 9, and the space regions 121a and 121b are ring-shaped regions centered on the central axis of the upper mirror support portion 9.
Here, the space area 121b has a larger volume than the space area 121a. That is, the diameter of the ring-shaped region is long. The space regions 121a and the space regions 121b are alternately located in the gravity direction (Z1-Z2 direction).

In this configuration, it becomes difficult for air to flow through the contact portion between the first heat conducting portion 81 where air flows in and out with the outside and the outer periphery of the upper mirror support portion 9, and the thermal conductivity with the outside is high. Can be lowered. Thereby, the temperature of the first region 71 can be stabilized.
Further, according to this configuration, a vortex flow is generated in the space regions 121a and 121b, and it becomes difficult for air to flow in the contact portion between the first heat conduction portion 81 and the upper mirror support portion 9, and the heat conductivity can be reduced.

FIG. 12 is a functional block diagram of the heat retaining mechanism of the measuring apparatus 1 shown in FIG.
The measuring apparatus 1 has a first thermometer 131 provided near the measured object 7 in the first area 71.
The measuring apparatus 1 also has a second thermometer 133 provided near the contact portion of the first heat conducting portion 81 with the upper mirror support portion 9.
The measuring apparatus 1 also includes a third thermometer 135 that is provided near the heat sink 95 and measures the temperature of the second region 93.

  The first temperature control unit 73 controls the temperature of the first area 71 based on the measurement results of the first thermometer 131 and the second thermometer 133. The first temperature control unit 73 performs feedback control on the order of 1/100 ° C. by a solid heat pump and high-speed chop control.

  The second temperature control unit 173 controls the temperature of the second region 93 based on the measurement result of the third thermometer 135. The second temperature control unit 173 controls the second region 93 to have a fluctuation of about 5/100 ° C. by a heat base (constant temperature circulator).

With this configuration, the temperature control by the first temperature control unit 73 and the second temperature control unit 173 can be appropriately performed based on the measured temperature.
13: is a figure which shows the temperature of the 1st area | region 71 in which the to-be-measured object 7 is located, and the external air temperature of the measuring apparatus 1 on a time-axis.
As can be seen from FIG. 13, the temperature of the first region 71 is stable even if the outside air temperature changes.

  A low expansion material is used as the main structural material and the optical material of the measuring device 1. For example, CFRP, clear serum, or the like is used as the structural member of the measuring device 1.

The present invention is not limited to the above embodiments.
That is, those skilled in the art may make various changes, combinations, sub-combinations, and substitutions with respect to the constituent elements of the above-described embodiments within the technical scope of the present invention or the equivalent scope thereof.

  For example, in the above-described embodiment, three oil tanks 31 (1), 31 (2), 31 (3) are provided, but the number and arrangement of oil tanks are not particularly limited.

  Further, in the above-described embodiment, the trapezoidal beam splitter is illustrated as the first optical unit 411, but it is particularly limited as long as the reflected light on the inner surface of the third light L31 does not enter the second optical unit 413. Not done.

  INDUSTRIAL APPLICABILITY The present invention can be applied to a system for measuring the length of an object to be measured.

DESCRIPTION OF SYMBOLS 1 ... Measuring device 7 ... Object to be measured 9 ... Upper mirror support 11 ... First base 13 ... Second base 17 ... Discs 23, 25 ... Leaf springs 21 (1), 21 (2), 21 (3) ... Floating bodies 27, 29 ... Ring-shaped members 31 (1), 31 (2), 31 (3) ... Oil tanks 33 (1), 33 (2) ... Slide guides 39 (1), 39 (2) ... Slide guide 41 ... Optical section 51 ... Upper mirror 53 ... Lower mirror support section 55 ... Lower mirror 61 ... Reservoir tank 71 ... First area 73 ... First temperature control section 81 ... First heat conduction section 93 ... Second Area 131 ... First thermometer 133 ... Second thermometer 135 ... Third thermometer 151 ... Light source 153 ... Light receiving part 173 ... Second temperature control part 411 ... First optical part 411a ... First Light splitting surface 413 ... Second optical portion 413a ... Second light splitting surface 415 ... 1/4 Long plate

Claims (5)

A distance between the reference surface and the surface to be inspected, or a measuring device for measuring the amount of change in the distance,
A light source,
A first light splitting surface that transmits a part of the second light of the first light from the light source in the first direction and reflects the remaining third light; First optical means, which is a trapezoidal beam splitter that reflects light toward a first direction on a first surface parallel to the first light splitting surface;
The first incident second light and the third light from the optical means reflects one of the optical of the second light and the third light toward the reference surface, the Fourth light, which is reflected light of one light on the reference surface, is emitted to the first optical means, and the other light of the second light and the third light is directed to the surface to be inspected. Second optical means having a second light splitting surface that reflects the other light and emits fifth light, which is reflected light of the other light on the surface to be inspected, to the first optical means,
A light receiving means,
Have
The first optical means is formed integrally with the second optical means, and the light reflected by the first surface of the third light does not enter the first light splitting surface. And is configured to enter the second light splitting surface only through the inside of the integrated first optical means and second optical means,
The first light splitting surface reflects one of the fourth light and the fifth light from the second optical means, transmits the other, and transmits the fourth light and the fifth light. Produces synthetic light with
The light receiving unit is a measuring device that receives the combined light. The first optical means is
The angle between the first light splitting surface and the rays of the first light and the second light is 45 °,
The direction of incidence of the first light on the first optical means is parallel to the first direction,
The measurement according to claim 1, wherein the fourth light that has entered the first optical means from the second optical means does not enter the first light splitting surface but enters the first surface. apparatus. The second optical means is
A second light splitting surface,
The second side,
And a third surface,
The second light is reflected by the second light separation surface toward the surface to be inspected, and the fourth light, which is reflected light of the second light, is directed toward the second light separation surface. The light reflected by the second surface and the third surface of the fourth light is transmitted with the second light splitting surface directed toward the test surface, and is reflected by the test surface. Light is reflected at the second light splitting surface towards the first optical means,
The third light is reflected by the second light separation surface toward the reference surface, and the fifth light, which is reflected light of the third light, is transmitted toward the second light separation surface. However, the reflected light of the fifth light on the second surface and the third surface is transmitted with the second light separating surface facing the reference surface, and the reflected light on the reference surface is the light. The measuring device according to claim 1, wherein the measuring device is reflected by the second light splitting surface toward the first optical means. A holding means for holding the reference surface and the surface to be inspected so that the direction in which light is incident is the direction of gravity;
The light source emits a first light in a horizontal direction,
The measurement device according to claim 1, wherein the light receiving unit receives the combined light from a horizontal direction. The measuring device according to any one of claims 1 to 4, further comprising a calculating unit that calculates the distance or the amount of change based on a light reception result of the light receiving unit.

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