JP3795646B2 - Position measuring device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a position measuring apparatus, and more particularly to an apparatus for measuring the positions of a first moving body and a second moving body that run side by side with high accuracy.
[0002]
[Prior art]
As a length measuring device, a light wave interferometer using laser light is known. The length measurement accuracy can reach 10 ^-8 to 10 ^-11 in principle, and therefore the light wave interferometer is an indispensable device for high-precision length measurement in a vacuum. However, when measurement is performed in the air using such a light wave interferometer, the measurement accuracy deteriorates due to wavelength fluctuations due to fluctuations in the refractive index of air. For example, even if the total length of the measurement optical path is 1 mm or less, the standard deviation varies by about ± 5 nm. In addition, the variation increases with an increase in the total length of the measurement optical path. For example, when the total length of the optical path length is 1 m, the variation due to fluctuation is about ± 100 nm.
[0003]
Further, when the object moves, air movement occurs due to the influence of the movement, and as a result, the refractive index of air on the measurement optical path varies greatly. For example, it has been reported that when an object reciprocates at a low speed of 0.25 μm with a period of 1 second, the error of the output of the light wave interferometer exceeds ± 50 nm.
[0004]
Accordingly, when the distance between objects and the displacement of the object are measured using an optical interferometer in the air, there is a problem in that high-accuracy measurement cannot be realized because the above error occurs.
[0005]
Thus, it has been proposed to cancel the refractive index variation as described above using two light waves having different wavelengths. However, even in this method, it is a practical limit to suppress the fluctuation range to about ± 5 nm while the object is stationary with respect to the measurement optical path length of about 500 mm.
[0006]
On the other hand, Japanese Patent Laid-Open No. 8-166215 discloses an apparatus for measuring the length of a measurement target (in the air) outside the bellows by accommodating the entire measurement system in a bellows whose inside is evacuated. Has been. However, there is a problem that the variable range of length is limited by the structural constraints of bellows.
[0007]
[Problems to be solved by the invention]
As described above, conventionally, when the variable range of the length becomes as large as several tens of mm or more, the measurement performance of the light wave interferometer based on the high stability and high accuracy of the light wavelength in vacuum is used in the air. In particular, the position of the moving body that shakes the air in the air could not be measured with high accuracy.
[0008]
The present invention has been made in view of the above-described problems of the prior art, and the purpose thereof is the same as that of light wave interference measurement in a vacuum in which the position of a moving object placed in the air or an environment identified with the same is measured. It is to measure with a degree of accuracy.
[0009]
[Means for Solving the Problems]
To achieve the above object, the first invention provides a first moving body that moves in a first space, a second moving body that moves in parallel with the first moving body in a second space, and the first moving body. Separating means having a transmission part that transmits light to at least a part of the first space and the second space, a first light wave interferometer measuring the displacement of the first moving body, and the first moving body And relative displacement measuring means for measuring the relative displacement of the second moving body, the displacement of the first moving body measured by the first length measuring means, and the relative displacement measured by the relative displacement measuring means, Computing means for computing the position of the second moving body, wherein the relative measuring means comprises a scale provided on one of the first moving body or the second moving body, and the first moving body or the first moving body. Detection means provided on the other of the two moving bodies and detecting a change in the scale position of the scale Characterized in that it comprises a. By measuring the position of the first moving body with a light wave interferometer with high accuracy and measuring the relative displacement between the first moving body and the second moving body with high accuracy using a scale, The position of the two moving bodies can be calculated with high accuracy.
[0010]
According to a second aspect, in the first aspect, the first space is substantially in a vacuum state. Thereby, the position of the first moving body can be measured with high accuracy.
[0011]
In addition, a third invention is characterized in that, in the first invention, the first space is filled with a gas such as He ^{2 which} has less fluctuation in the refractive index of light than air. This also makes it possible to measure the position of the first moving body with high accuracy.
[0012]
According to a fourth aspect, in the first to third aspects, the second space is substantially filled with air. Accordingly, the position of the second moving body that moves in the air can be obtained with high accuracy.
[0013]
According to a fifth invention, in the first to fourth inventions, a second light wave interferometer measuring the posture of the second moving body and the first motion measured by the first light wave interferometer. Further comprising control means for causing the first moving body and the second moving body to move in parallel based on the posture of the body and the posture of the second moving body measured by the second light wave interferometer. To do. By moving both moving bodies in parallel, the positional accuracy of the second moving body calculated based on the relative displacement can be ensured.
[0014]
The sixth invention is the fifth invention, further comprising first and second reflecting mirrors provided on the first moving body, and a third reflecting mirror provided on the second moving body. The first reflecting mirror is arranged so as to be orthogonal to the optical path of the first lightwave interferometer, and the second reflector directs light from the second lightwave interferometer to the second moving body. Therefore, the third reflecting mirror is arranged at a predetermined angle with respect to the optical path, and the third reflecting mirror is arranged so as to be orthogonal to the optical path of the light from the second light wave interferometer measured by the second reflecting mirror, The control means controls to maintain the relationship between the first, second and third reflecting mirrors and the optical path.
[0015]
According to a seventh aspect, in the sixth aspect, the predetermined angle is π / 4.
[0016]
Further, an eighth invention is the first to seventh inventions, wherein a gas flow having a moving speed larger than a moving speed of the second moving body is generated between the isolating means and the second moving body. It further has laminar flow forming means. Thereby, the fluctuation of the air between the separating means and the second moving body can be reduced, and the relative displacement can be measured with high accuracy.
[0017]
In a ninth aspect based on the first to eighth aspects, the isolating means is made of a nonmagnetic material, and the first moving body follows the movement of the second moving body by magnetic interaction. It is characterized by moving without contact. By causing the first moving body to follow the movement of the second moving body, the position can be reliably measured even if the amount of movement of the second moving body is large.
[0018]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
[0019]
<First Embodiment>
The length measuring unit of the position measuring apparatus in this embodiment is roughly composed of two parts. The first is a part for measuring the position of the first moving body, and the second is a part for measuring a relative variation between the first moving body and the second moving body. The part for measuring the position of the first moving body includes a light wave interferometer, and measures the first moving body that moves substantially in a vacuum with high accuracy. The portion for measuring the relative displacement between the first moving body and the second moving body projects a scale with a predetermined scale and light to the scale, and detects the reflected light or transmitted light from the scale, thereby the position of the scale. A relative position detector for detecting changes in Such a length measurement method for detecting a change in the scale scale position depends on the structure of the scale scale (the layout of the scale and the properties of the members), but the fluctuation in the refractive index of the air Since there is no influence, there is an advantage that the measured value is stable unless the interval at which the scale is arranged changes due to temperature change, acceleration, application of external force, secular change, or the like.
[0020]
FIG. 1 shows a specific configuration of the position measuring apparatus of the present embodiment. The first moving body 12 is accommodated in the first space 14. This first space is a substantially vacuum space. The “substantially vacuum” refers to a vacuum that can ignore the influence of air fluctuations on the light passing therethrough, and does not necessarily mean a complete vacuum state. The first moving body 12 is provided with two reflecting mirrors (mirrors) M1 and M2. The mirror M1 is relative to the optical path 100 (first measurement optical path) of a first light wave interferometer (hereinafter referred to as a light wave interferometer) 10A that measures the position and orientation (pitch angle and yaw angle) of the first moving body 12. It arrange | positions so that it may orthogonally cross. Accordingly, the laser light emitted from the first light wave interferometer 10A is reflected by the mirror M1 and is incident on the first light wave interferometer 10A again. Further, the mirror M2 has a predetermined angle (α = in the figure) with respect to the optical path 200 (second measurement optical path) of the second light wave interferometer 10B that measures the posture (pitch angle and yaw angle) of the second moving body 16 described later. They are inclined so as to form π / 4). Further, the first moving body 12 is provided with a scale 12A having a scale formed on the surface thereof. The scale interval of the scale 12A is formed with high accuracy like a semiconductor circuit pattern, and has a resolution comparable to that of a laser wavelength interferometer. In addition, the 1st moving body 12 can move to the left-right direction of a paper surface, as shown in a figure. As an environment in which the influence of air fluctuation can be ignored, the first space 14 is not in a vacuum state, and can be filled with a gas such as He, which has a significantly smaller fluctuation in the refractive index of light than air. It is.
[0021]
On the other hand, the second moving body 16 is accommodated in the second space 18. The second space 18 is, for example, a space in the atmosphere. A mirror M3 is disposed on the second moving body 16 so as to be orthogonal to the optical path 200 of the second optical interferometer 10B reflected by the mirror M2. Accordingly, the laser light emitted from the second light wave interferometer 10B is reflected by the mirror M2, reflected by the mirror M3, incident on the mirror M2, reflected by the mirror M2, and again incident on the second light wave interferometer 10B. Further, the second moving body 16 is provided with a relative displacement detector 16A that detects a change in the position of the scale of the scale 12A. The relationship between the scale 12A and the relative displacement detector 16A will be described in detail later. Similarly to the first moving body 12, the second moving body 16 can also move in the left-right direction on the paper surface.
[0022]
The first space 14 and the second space 18 are separated by a partition wall 20. The laser beam transmission part in the partition wall 20, that is, the transmission part of the optical path 200 and the transmission part of the optical path between the relative displacement detector 16A and the scale 12A are made of an optically transparent member (for example, glass). Of course, the part of the partition wall 20 may be a hollow container and filled with gas so that the refractive index does not fluctuate. The first space 14 is formed inside a container (not shown), and the second space 18 may be formed in the container, but may be open to the atmosphere.
[0023]
The posture control unit 24 is means for controlling the position of the first moving body 12 in the moving direction and controlling the posture of the first moving body 12. Specifically, control is performed so that the mirror M1 is always orthogonal to the optical path 100 according to the position and orientation of the first moving body 12 measured by the first light wave interferometer 10A.
[0024]
The posture control unit 32 is means for controlling the posture of the second moving body in the movement direction. Specifically, the mirror M3 is controlled so as to be always orthogonal to the optical path 200 according to the posture of the second moving body 16 measured by the second light wave interferometer 10B. Specifically, the yaw angle and pitch angle of the second moving body 16 are adjusted so that the mirror M3 is always orthogonal to the optical path 200. As a result, the first moving body 12 and the second moving body 16 move in parallel. Therefore, both the first moving body 12 and the second moving body move in parallel with the optical axis 100 in vacuum. The measurement data of the second interferometer 10B can be supplied to the attitude control unit 32 by wire or wirelessly.
[0025]
The relative displacement detector 16A projects a laser beam toward the scale of the scale 12A, and detects the displacement of the scale by receiving the reflected light. Taking a diffraction grating as an example of the scale, the optical path of the laser light projected from the relative displacement detector 16A toward the scale 12A is from the direction of the ± first-order diffraction angle as shown as optical paths 300 and 400 in the figure. Incident on the scale. This projection light is diffracted by a scale (diffraction grating), and this diffracted light becomes 0th-order diffracted light, that is, reflected light perpendicular to the scale 12A. Then, the reflected light is reflected by a mirror (not shown) of the relative displacement detector 16A, and enters as an optical path 500 perpendicular to the scale of the scale 12A. The optical path 500 perpendicularly incident on the scale of the scale 12A is diffracted by the scale to become ± first-order diffracted light, and enters the light receiving unit (not shown) of the relative displacement detector 16A through the optical paths 300 and 400. The relative displacement detection unit 16A is parallel to each other by a known method (see, for example, “High-resolution linear scale” Makoto Sugaya, Journal of Japan Society for Precision Engineering, pp. 57, page 1943) based on the re-incident laser beams in the optical paths 300 and 400. The relative displacement of the first moving body 12 and the second moving body 16 that move in the same manner is detected. Briefly explaining the detection principle, the zero-order light from the diffraction grating does not contain the phase of the grating, but the ± first-order light contains the phase information of the grating, and the grating moves in a certain direction. The phase of the diffracted light also changes. Therefore, the relative displacement between the first moving body 12 and the second moving body 16 can be detected by detecting this phase (specifically, the change in the intensity of the ± 1st order interference light).
[0026]
The calculation unit 33 is based on the position data of the first moving body measured by the first light wave interferometer 10A and the relative displacement data of the first moving body 12 and the second moving body 16 measured by the relative displacement detection unit 16A. Thus, the position of the second moving body is calculated. Specifically, the position of the second moving body = the position of the first moving body + the relative displacement of both moving bodies is calculated. The calculated position of the second moving body 16 is output to, for example, a display device (not shown).
[0027]
Thus, in the present embodiment, the position of the first moving body that is substantially in a vacuum state is measured with high accuracy by the light wave interferometer, and the relative displacement between the first moving body and the second moving body is determined as the refractive index of the air. It is possible to measure with high accuracy using a scale that is not affected by fluctuations in the position, and to calculate the position of the second moving body with high accuracy based on both measurement values.
[0028]
Note that, on the optical path 200 for measuring the posture of the second moving body 16, it is necessary to reduce the refractive index fluctuation as much as possible from the viewpoint of high-precision control. Accordingly, the area 600 around the mirror M3 is preferably made of a glass material having no refractive index fluctuation, for example, like the partition wall 20, and the circumference thereof is made of such a glass material, and the inside is substantially made. It may be in a vacuum state.
[0029]
Further, in order to suppress the influence of air fluctuation existing between the partition wall 20 and the second moving body 16, a laminar flow forming unit 30 may inject a high-speed air flow to stabilize the gas flow at this interval. Is preferred. In order to effectively suppress air fluctuation due to the movement of the second moving body 16, the laminar flow speed needs to be significantly higher than the movement speed of the second moving body 16.
[0030]
FIG. 2 shows specific drive mechanisms (including posture control units 24 and 32) for the first moving body 12 and the second moving body. The first moving body 12 and the second moving body 16 both require a guide mechanism and a driving mechanism related to the movement, and the second moving body 16 is a movement in the air. Although a mechanism used in a machine or the like can be used as it is, the first moving body 12 needs to be moved with high accuracy in a vacuum. If an ordinary contact type guide mechanism is used, problems such as lubrication adapted to a vacuum may occur. On the other hand, a non-contact type guide mechanism such as a magnetic levitation mechanism or a non-contact linear motor may be used for the first moving body 12. In this embodiment, the following simple drive mechanism is employed.
[0031]
That is, in the figure, the first moving body 12 and the second moving body 16 move in the direction perpendicular to the paper surface. The partition wall 20 that houses the first moving body 12 is supported by a support mechanism 34. Further, the second moving body 16 is fixed to a measured body (not shown).
[0032]
As described above, the partition wall 20 is provided with a transmission member through which laser light is transmitted, and is shown here as a window 20A. The inside of the partition wall 20 is maintained in a substantially vacuum state.
[0033]
In the partition wall 20, the first moving body 12 is provided so as to be movable along the moving direction, and further, a first optical system 36 including a mirror M2 and a scale 12A is provided. The first moving body 12 is driven by the vertical control unit 600 and the left / right control unit 700 in a non-contact manner with respect to the partition wall 20. The up / down control unit 600 and the left / right control unit 700 correspond to the posture control unit 24 in FIG. 1. The vertical controller 600 includes a magnetic circuit constituent element 38 fixedly arranged on the second moving body 16, a magnetic circuit constituent element 40 fixedly arranged on the first moving body 12, and an excitation control coil that excites the magnetic circuit constituent element 38. 42. Further, the left / right control unit 700 excites the magnetic circuit constituent element 44 fixedly arranged on the second moving body 16, the magnetic circuit constituent element 46 fixedly arranged on the first moving body 12, and the magnetic circuit constituent element 44. The excitation control coil 48 is configured. Further, a magnetic sensor 50 is provided for detecting the excitation action by the vertical control unit 600, and a magnetic sensor 52 is provided for detecting the magnetic action by the left / right control unit 700.
[0034]
Excitation is controlled by the vertical control unit 600 and the left / right control unit 700 based on the outputs of the magnetic sensors 50 and 52. As a result, the posture of the first moving body 12 is always controlled to be constant. That is, a stable state without contact with the partition wall 20 is established.
[0035]
The second moving body 16 is provided with a second optical system 37, and the second optical system 37 includes the mirror M3 and the relative displacement detector 16A shown in FIG. That is, the laser light travels between the first optical system 36 and the second optical system 37 through the window 20A.
[0036]
In such a configuration, when the second moving body 16 moves, the relative displacement between the second moving body 16 and the first moving body 12 is always detected by the relative displacement detector 16A. As described above, since the position of the first moving body 12 can be measured with high accuracy under vacuum conditions, as a result, the position of the second moving body 16 can be measured with high accuracy as the position of the first moving body 12. Is possible. In other words, the position of the second moving body 16 in the air can be observed with the same accuracy as the observation in vacuum. Therefore, highly accurate position measurement can be realized by fully utilizing the function of the optical interferometer.
[0037]
It is also possible to feed back the relative displacement detected by the relative displacement detector 16A to the posture controller 24 and control the position of the first moving body 12 so that the relative displacement becomes zero. That is, the first moving body 12 can be moved following the movement of the second moving body 16. Thereby, even when the movement amount of the second moving body 16 is large, it is possible to reliably measure the relative displacement and calculate the position.
[0038]
The apparatus as shown in FIG. 2 can be used in the field of, for example, an apparatus that performs high-precision processing or a semiconductor manufacturing apparatus.
[0039]
Second Embodiment
In the first embodiment described above, an example in which a reflective scale is used as a mechanism for measuring the relative displacement between the first moving body 12 and the second moving body 16 has been described. It is.
[0040]
FIG. 3 shows a configuration in the case where a transmission scale is used. In the figure, (A) is a front view and (B) is a side view. The first moving body 12 is provided with a transmission scale 12A and a corner cube (or reflection mirror) 12B, and the second moving body 16 is provided with a relative displacement detector 16A. In the relative displacement detector 16A, a light emitter 16B and a light receiver 16C for emitting laser light are provided. The laser light from the light emitting unit 16B passes through the scale of the scale 12A, is reflected by the corner cube 12B, and enters the light receiving unit 16C without passing through the scale 12A.
[0041]
With such a configuration, the position measuring device can be easily obtained even with a normal scale grating whose scale is not a diffraction grating.
[0042]
【The invention's effect】
As described above, according to the present invention, the displacement (position) of a moving object placed in the air or in the same environment as that is measured with the same degree of accuracy as optical wave interference measurement in a vacuum. Can do.
[Brief description of the drawings]
FIG. 1 is an overall configuration diagram of an embodiment of the present invention.
FIG. 2 is an explanatory diagram of a drive mechanism according to an embodiment of the present invention.
FIG. 3 is a configuration diagram of another embodiment of the present invention.
[Explanation of symbols]
10A 1st light wave interferometer, 10B 2nd light wave interferometer, 12 1st moving body, 14 1st space, 16 2nd moving body, 18 2nd space, 20 Bulkhead, 24 Posture control part, 30 Laminar flow formation part, 32 attitude control unit, 33 calculation unit, 100 first measurement optical path, 200 second measurement optical path, 600 up / down control unit, 700 left / right control unit.

Claims (9)

A first moving body that moves in the first space;
A second moving body that moves in parallel with the first moving body in a second space;
An isolating means for isolating the first space and the second space, and comprising a transmission part that transmits light in at least a part thereof;
A first light wave interferometer measuring the displacement of the first moving body;
A relative displacement measuring means for measuring a relative displacement between the first moving body and the second moving body;
A computing means for computing the position of the second moving body based on the displacement of the first moving body measured by the first length measuring means and the relative displacement measured by the relative displacement measuring means;
The relative measurement means includes
A scale provided on one of the first moving body or the second moving body;
Detecting means provided on the other of the first moving body or the second moving body and detecting a change in the scale position of the scale;
A position measuring device comprising: The position measurement apparatus according to claim 1, wherein the first space is substantially in a vacuum state. The position measurement apparatus according to claim 1, wherein the first space is filled with a gas that has a smaller refractive index fluctuation than air. The position measurement apparatus according to claim 1, wherein the second space is substantially filled with air. A second light wave interferometer measuring the posture of the second moving body;
The first motion body and the second motion based on the posture of the first moving body measured by the first light wave interferometer and the posture of the second moving body measured by the second light wave interferometer. Control means to move the body in parallel;
The position measuring device according to claim 1, further comprising: First and second reflecting mirrors provided on the first moving body;
A third reflector provided on the second moving body;
Further comprising
The first reflecting mirror is disposed so as to be orthogonal to the optical path of the first lightwave interferometer,
The second reflecting mirror is disposed at a predetermined angle with respect to the optical path so as to direct the light from the second light wave interferometer to the second moving body,
The third reflecting mirror is disposed so as to be orthogonal to the optical path of the light from the second lightwave interferometer measured by the second reflecting mirror,
6. The position measuring apparatus according to claim 5, wherein the control means controls so as to maintain a relationship between the first, second and third reflecting mirrors and an optical path. The position measuring apparatus according to claim 6, wherein the predetermined angle is π / 4. Laminar flow forming means for generating a gas flow having a moving speed larger than the moving speed of the second moving body between the isolating means and the second moving body;
The position measuring device according to claim 1, further comprising: The isolating means is made of a non-magnetic material;
The position measuring apparatus according to claim 1, wherein the first moving body moves in a non-contact manner following the movement of the second moving body by a magnetic interaction.

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