JP7224747B1 - Displacement detection member and displacement detection device - Google Patents

Abstract

A displacement detection device capable of effectively utilizing an installation space on the side of a member to be measured is provided.
A displacement detection member includes a first detection head that detects a first displacement of the member to be measured in a first direction, and a second displacement in a height direction that is a second direction different from the first direction of the member to be measured. and detecting the displacement of the member to be measured based on the detection signal detected by the second detection head. The displacement detection member includes a diffraction grating, a protective layer that protects the diffraction grating, and a wavelength band selector that transmits light in a first wavelength band through the protective layer toward the diffraction grating and reflects light in a second wavelength band. a layer; The wavelength band selection layer has a passage area through which light in a first wavelength band detected by the first detection head passes, and the second detection head detects light in a second wavelength band reflected on the passage area, A second detection head is formed to detect the second displacement based on the detected detection signal.
[Selection drawing] Fig. 2

Description

The present invention relates to a displacement detection device that detects displacement of a member to be measured using a non-contact sensor that uses light emitted from a light source.

Conventionally, a displacement detection device using light has been widely used as a device for non-contact measurement of the displacement and orientation of a member to be measured (see Patent Document 1).

Patent Literature 1 discloses a technique of providing a scale on a moving body and measuring position information of the moving body within a moving plane by an encoder system. In this encoder system, positional information is measured by irradiating the scale with light and receiving the light reflected by the diffraction grating of the scale.

U.S. Patent Application Publication No. 2008/094592 (International Publication No. 2008/026742) U.S. Pat. No. 7,573,581

However, in such an encoder system, when measuring the displacement of a moving object in a plurality of different directions, it is necessary to provide a scale corresponding to each direction. Therefore, the detectable range at each scale is limited due to the installation space on the moving body.

Accordingly, the present invention provides a displacement detection device and the like that can solve these problems.

According to the present invention, the installation space on the side of the member to be measured can be effectively utilized.

1 is a diagram schematically showing the configuration of a displacement detection device according to a first embodiment; FIG. FIG. 3 is a cross-sectional view showing the configuration of a scale; It is a figure which shows an example of the characteristic of a wavelength band selection layer. FIG. 3 is a diagram showing the configuration of a first detection head; It is a figure showing the structure of a light-receiving part. It is a figure showing the structure of a 2nd detection head. FIG. 4 is a diagram schematically showing the structure of a scale; It is a figure showing the example of a calculator. FIG. 7 is a diagram schematically showing the configuration of a displacement detection device according to a second embodiment; It is a figure showing the structure of a scale typically. It is a figure showing the example of a calculator. FIG. 11 is a diagram schematically showing the configuration of a displacement detection device according to a third embodiment; It is a figure showing the example of a calculator.

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. In addition, about the following embodiment and its modification, the same code|symbol is attached|subjected about the substantially same component, and the description is abbreviate|omitted suitably.
[First embodiment]
FIG. 1 is a diagram schematically showing the configuration of the displacement detection device according to the first embodiment.
A displacement detection device 1 includes a scale 2 , a first detection head 3 , a second detection head 4 and a computing machine 5 . The scale 2 is a displacement detection member incorporating a diffraction grating, and can be installed on a stage movable in the X-axis direction, the Y-axis direction, or the Z-axis direction. The stage is provided on a moving body (member to be measured) (not shown). In this embodiment, the X-axis direction and the Y-axis direction are set in the direction in which the surface of the scale 2 spreads, that is, in the direction of the plane on which the scale 2 is installed, and the height direction of the scale 2 is orthogonal to that plane (XY plane). is the Z-axis direction. A scale that incorporates a diffraction grating is also called a "diffraction grating scale".

The first detection head 3 functions as a "first grating interference displacement detection head" and outputs displacement information (first displacement) of the scale 2 in the X-axis direction (first direction). That is, the first detection head 3 detects the first displacement of the moving body in the first direction. The second detection head 4 functions as a "second grating interference displacement detection head" and outputs displacement information (second displacement) in the Z-axis direction (second direction). That is, the second detection head 4 detects the second displacement in the height direction, which is the second direction of the moving body. The displacement detection device 1 detects displacement of the moving body based on detection signals detected by the first detection head 3 and the second detection head 4 .

FIG. 2 is a cross-sectional view showing the configuration of the scale 2. As shown in FIG.
The scale 2 is configured by arranging a diffraction grating 2b on a substrate 2a. The surface of the diffraction grating 2b is covered and protected by a protective layer 2c having a certain thickness. The upper surface of the protective layer 2c is smooth, and the wavelength band selection layer 2d is arranged thereon. The wavelength band selection layer 2d has a passage region through which light in the first wavelength band passes, and reflects light in the second wavelength band on the passage region (upper surface). The wavelength band selection layer 2d is a multilayer film that transmits light in the first wavelength band and reflects light in the second wavelength band.

A glass substrate, a metal substrate, a resin sheet, or the like is adopted as the base material 2a. Diffraction grating 2b is a reflective diffraction grating having a first grating vector parallel to the X-axis direction. The diffraction grating 2b may be, for example, a chromium film in which periodic irregularities are recorded and coated with aluminum, gold, silver, or the like having high reflectance as a reflective layer. The period Λ of the unevenness is the pitch of the grating and is assumed to be submicron to several microns.

The protective layer 2c has a role of protecting the diffraction grating 2b and a role of arranging the wavelength band selection layer 2d on the top surface, and has a two-layer structure in this embodiment. The wavelength band selection layer 2d is assumed to have a thickness of submicrons to several millimeters so as to efficiently transmit the first wavelength band. The wavelength band selection layer 2d may be formed by forming a film of SiO ₂ as a material on the protective layer 2c by CVD (Chemical Vapor Deposition) or sputtering. Alternatively, the cover glass may be adhered with a resin adhesive or the like. At that time, it is preferable to match the refractive index of the adhesive with the refractive index of the cover glass. The wavelength band selection layer 2d may have a characteristic of transmitting light in a first wavelength band centered at 790 nm and reflecting light in a second wavelength band centered at 655 nm, for example.

FIG. 3 is a diagram showing an example of the characteristics of the wavelength band selection layer 2d.
The wavelength band selection layer 2d functions as a “bandpass filter” and reflects 93% or more of incident light having a wavelength band of 655±10 nm (645 to 665 nm) (corresponding to the “second wavelength band”). , 1% or less. In addition, 93% or more of incident light having a wavelength band of 790±10 nm (780 to 800 nm) (corresponding to the “first wavelength band”) is transmitted, and 1% or less is reflected.

The wavelength band selection layer 2d has a high transmittance for light in the first wavelength band at a specific wavelength and an incident angle to the wavelength band selection layer 2d. The reason why the first wavelength band has a wavelength bandwidth is to allow variations in the wavelength of the light source and variations in the angle of incidence on the wavelength band selection layer 2d. Further, the wavelength band selection layer 2d has a high reflectance with respect to light in the second wavelength band at a specific wavelength and an incident angle to the wavelength band selection layer 2d. The reason why the second wavelength band is provided with a wavelength bandwidth is to allow variations in the wavelength of the light source and variations in the angle of incidence on the wavelength band selection layer 2d.

FIG. 2 shows an example of reflection on scale 2 of light B1 (light in the first wavelength band) with a center wavelength of 790 nm and light B2 (light in the second wavelength band) with a center wavelength of 655 nm. there is The light B1 is guided to the scale 2 at an incident angle of 27.7°, for example, is not reflected by the surface of the wavelength band selection layer 2d, passes through the wavelength band selection layer 2d and the protective layer 2c, and is reflected by the surface of the diffraction grating 2b. , is diffracted (see dotted arrow).

On the other hand, the light B2 is guided to the scale 2 at an incident angle of 45°, for example, and reflected by the surface of the wavelength band selection layer 2d (see the solid line arrow). As shown in FIG. 2, even if the lights B1 and B2 are guided to the same position P1 on the surface of the scale 2, one is transmitted and the other is reflected. In other words, the same incident point on the scale 2 can be used for the light in the first wavelength band and the light in the second wavelength band.

FIG. 4 is a diagram showing the configuration of the first detection head 3. As shown in FIG.
The first detection head 3 includes a light source 3a, a polarizing beam splitter 3b, mirrors 3c and 3d, phase plates with mirrors 3e and 3f, and a light receiving portion 3g. The polarizing beam splitter 3b functions as a "first polarizing beam splitter", the mirrors 3c and 3d function as a "first reflecting means", and the light receiving section 3g functions as a "first light receiving means". In addition, below, a polarizing beam splitter (Polarizing Beam Splitter) is also written as "PBS" for convenience. The first detection head 3 detects the light in the first wavelength band that has passed through the wavelength band selection layer 2d on the scale 2 and has been reflected by the diffraction grating 2b.

The light source 3a is a first light source that emits light in a first wavelength band, and can employ a coherent light source such as a laser diode, an LED, a superluminescent diode, a solid state laser, or a gas laser. In particular, multimode lasers, LEDs, superluminescent diodes, etc., which are coherent light sources but have extremely short coherence lengths, are desirable for preventing the generation of unwanted interference light. This is because the unwanted interference light destroys the waveform of the sine wave when forming an interference signal for displacement detection, and deteriorates the accuracy of displacement detection.

A beam L emitted from the light source 3a is split into two beams L1 and L2 by the PBS 3b. At this time, the angle of polarization of the beam L emitted from the light source 3a is determined so that the light amounts of the beam L1 and the beam L2 are substantially equal.

One of the split beams L1 has a polarization state of the P wave component, so it passes through the PBS 3b, is reflected by the mirror 3c, and enters the scale 2. FIG. At this time, since the beam L1 is light in the first wavelength band, it passes through the wavelength band selection layer 2d of the scale 2, passes through the protective layer 2c, and travels toward the diffraction grating 2b. Then, the light is diffracted by the diffraction grating 2b and guided to the mirrored phase plate 3e. The beam L1 is reflected by the mirrored phase plate 3e.

As the mirrored phase plate 3e, a λ/4 phase plate with a mirror is assumed. The beam L1 becomes an S-wave component after passing through the phase plate 3e with a mirror, enters the scale 2 again, is diffracted a second time, and returns along the previous path. That is, beam L1 is guided by mirror 3c, reflected, and returns to PBS 3b. Since the beam L1 is an S-wave component at this time, it is reflected by the PBS 3b and overlapped with a beam L2, which will be described later, and guided to the light receiving section 3g.

The other split beam L2 is reflected by the PBS 3b because its polarization state is the S-wave component. This beam L2 is incident on the scale 2 after being reflected by the mirror 3d. At this time, since the beam L2 is light in the first wavelength band, it passes through the wavelength band selection layer 2d of the scale 2, passes through the protective layer 2c, and travels toward the diffraction grating 2b. Then, the light is diffracted by the diffraction grating 2b and guided to the mirrored phase plate 3f. The beam L2 is reflected by the mirrored phase plate 3f.

As the mirrored phase plate 3f, a λ/4 phase plate with a mirror is assumed. The beam L2 becomes a P-wave component by passing through the phase plate 3f with a mirror, enters the scale 2 again, is diffracted a second time, and returns along the previous path. That is, beam L2 is guided by mirror 3d, reflected, and returns to PBS 3b. Since the beam L2 is a P-wave component at this time, it is superimposed on the beam L1 while passing through the PBS 3b, and guided to the light receiving section 3g.

The first detection head 3 is adjusted so that the beam L1 and the beam L2 split into two by the PBS 3b have the same optical path length. This is effective when a light source with low coherence is used as the light source 3a. When a more inexpensive semiconductor laser is used as the light source 3a, the influence of the wavelength change of the light source 3a due to temperature change can be canceled by equalizing the optical path lengths of the beams L1 and L2. Even if there is a change in the refractive index of the air due to a change in air pressure, humidity, or temperature in the optical path, the same canceling effect is exhibited. These realize stable measurement in long-term measurement.

FIG. 5 is a diagram showing the configuration of the light receiving section 3g.
Light receiving portion 3g includes phase plate 50, half mirror 52, PBS 54, PBS 56, and light receiving elements 11a to 11d. PBS 54 is provided with light receiving elements 11a and 11b, and PBS 56 is provided with light receiving elements 11c and 11d.

The polarized light components of the two beams L1 and L2 superimposed by the PBS 3b do not interfere with each other as they are because the polarization axes of the S wave component and the P wave component are orthogonal to each other. Therefore, by passing the beams L1 and L2 through the phase plate 50, the beams are made such that the interference intensity of a specific polarization axis changes depending on the phase state of the light of the S wave component and the P wave component. This beam is split into two by a half mirror 52 and made incident on PBS 54 and PBS 56, respectively.

PBS 54 is positioned rotated 45 degrees about the incident beam direction with respect to PBS 56 . The PBSs 54 and 56 transmit and reflect specific polarized light components, respectively, and the interference light is received by the light receiving elements 11a to 11d and photoelectrically converted to obtain an interference signal. An interference signal obtained by each of the light receiving elements 11a to 11d is represented by Acos(4Kx+δ). A is the amplitude of the interference and K is the wavenumber denoted by 2π/Λ. δ indicates the initial phase. Λ is is the grating pitch at scale 2;

That is, when the scale 2 moves in the direction of the grating vector (X-axis direction) by 1/4 grating pitch (that is, Λ/4), the interference intensity of the specific polarization component becomes can get. The light receiving element 11a and the light receiving element 11b receive the interference light whose brightness is reversed by passing through the PBS 54, and photoelectrically convert the light. Further, the PBS 54 is rotated by approximately 45 degrees with respect to the PBS 56, and the phases of the light receiving elements 11c and 11d are shifted by 90 degrees with respect to the light receiving elements 11a and 11b. As a result, the phase difference of the interference signal is 180 degrees between the light receiving elements 11a and 11b, 90 degrees between the light receiving elements 11a and 11c, and 180 degrees between the light receiving elements 11c and 11d.

FIG. 6 is a diagram showing the configuration of the second detection head 4. As shown in FIG.
The second detection head 4 includes a light source 4a, a PBS 4b, mirrors 4c-4g, a scale 4h, a PBS 4i and a light receiving section 4j. The PBS 4b functions as a "second polarizing beam splitter", the mirrors 4c to 4g function as a "second reflecting means", the PBS 4i functions as a "beam combining means", and the light receiving section 4j functions as a "second light receiving means". Function. The second detection head 4 detects the light of the second wavelength band reflected on the passing region of the wavelength band selection layer 2d on the scale 2. FIG.

The light source 4a is a second light source that emits light in a second wavelength band, and can employ a coherent light source such as a laser diode, an LED, a superluminescent diode, a solid state laser, or a gas laser. In particular, multimode lasers, LEDs, superluminescent diodes, etc., which are coherent light sources but have extremely short coherence lengths, are desirable for preventing the generation of unwanted interference light. This is because the unwanted interference light destroys the waveform of the sine wave when forming an interference signal for displacement detection, and deteriorates the accuracy of displacement detection.

A beam L10 emitted from the light source 4a is split into two beams L11 and L12 by the PBS 4b. At this time, the polarization angle of the beam L10 emitted from the light source 4a is determined so that the light amounts of the beam L11 and the beam L12 are substantially equal.

One of the split beams L11 is polarized in the P-wave component, so it passes through the PBS 4b and is successively reflected by the mirrors 4g and 4e to enter the scale 4h. The scale 4h is a "diffraction grating scale" including a transmission diffraction grating (transmission diffraction grating 62 described later). The diffraction grating has grating vectors parallel to the Z-axis and diffracts each incoming beam. The beam L11 is diffracted by the diffraction grating of the scale 4h, then sequentially reflected by the mirrors 4f and 4g, and guided to the PBS 4i.

The other split beam L12 is reflected by the PBS 4b and guided to the scale 2 because its polarization state is the S-wave component. Since the beam L12 is light in the second wavelength band, it is reflected without passing through the wavelength band selection layer 2d of the scale 2, is reflected by the mirror 4c, and is diffracted by the scale 4h. Then, the light is reflected by the mirror 4d, guided to the scale 2 again, and reflected. This beam L12 is superimposed on the beam L11 while being reflected by the PBS 4i, and guided to the light receiving section 4j. The light receiving section 4j causes the beams superimposed by the PBS 4i to interfere with each other, and photoelectrically converts the interference light.

FIG. 7 is a diagram schematically showing the structure of the scale 4h.
The scale 4h has a transmissive diffraction grating 62 with a grating pitch d arranged on a glass substrate 60 . A volume type hologram is used as the transmission diffraction grating 62, and high diffraction efficiency can be obtained by diffracting the light under the Bragg condition.

Returning to FIG. 6, the second detection head 4 is adjusted so that the beam L11 and the beam L12 split into two by the PBS 4b have the same optical path length. Even if the scale 2 moves in the Z-axis direction, the optical path lengths of the beams L11 and L12 do not change. This is effective when a light source with low coherence is used as the light source 4a. When a more inexpensive semiconductor laser is used as the light source 4a, the influence of wavelength change of the light source 4a due to temperature change can be canceled by equalizing the optical path lengths of the beams L11 and L12. Even if there is a change in the refractive index of the air due to a change in air pressure, humidity, or temperature in the optical path, the same canceling effect is exhibited. These realize stable measurement in long-term measurement.

The structure of the light receiving portion 4j is the same as that of the light receiving portion 3g of the first detection head 3 (see FIG. 5). For convenience of explanation, the light receiving elements of the light receiving section 4j are hereinafter referred to as "light receiving elements 21a to 21d". That is, the light receiving elements 21a to 21d of the second detection head 4 correspond to the light receiving elements 11a to 11d of the first detection head 3, respectively.

The polarized light components of the two beams L11 and L12 superimposed by the PBS 4i do not interfere with each other as they are because the polarization axes of the S wave component and the P wave component are orthogonal to each other. Therefore, by passing the beams L1 and L2 through the phase plate 50, the beams are made such that the interference intensity of a specific polarization axis changes depending on the phase state of the light of the S wave component and the P wave component. This beam is split into two by a half mirror 52 and made incident on PBS 54 and PBS 56, respectively.

An interference signal obtained by each of the light receiving elements 21a to 21d is represented by Acos(2Kx+δ). A is the amplitude of the interference and K is the wavenumber denoted by 2π/d. δ indicates the initial phase. d is the grating pitch in the transmissive diffraction grating 62 of the scale 4h. As for the interference intensity of the specific polarization component, when the scale 2 moves in the Z-axis direction, the incident position of the beam L12 incident on the transmissive diffraction grating 62 of the scale 4h moves in the Z-axis direction. For example, when the scale 2 moves in the Z-axis direction by 1/2 the grating pitch (that is, d/2) of the transmissive diffraction grating 62, a signal is obtained as a change in the amount of light in one cycle.

FIG. 8 is a diagram showing a specific example of the computing machine 5. As shown in FIG.
The calculator 5 includes a displacement output section 10 that outputs displacement information detected by the first detection head 3 and a displacement output section 20 that outputs displacement information detected by the second detection head 4 . The displacement output section 10 includes differential amplifiers 12 a and 12 b, A/D converters 13 a and 13 b, a waveform correction processing circuit 14 and an incremental signal generator 15 . The displacement output unit 20 includes differential amplifiers 22 a and 22 b, A/D converters 23 a and 23 b, a waveform correction processing circuit 24 and an incremental signal generator 25 .

Among the interference signals photoelectrically converted by the first detection head 3, the interference signals between the light receiving elements 11a and 11b are DC-cancelled by the differential amplifier 12a. This cancels the DC offset of the electrical signal due to the increase/decrease in the interference intensity. Similarly, the light receiving elements 11c and 11d are also DC-cancelled by the differential amplifier 12b. Since the outputs of the differential amplifier 12a and the differential amplifier 12b have a phase difference of 90 degrees, the interference signal can be detected as sinusoidal waves of SIN and COS, so the direction of phase progression can be determined.

Each interference signal is digitally converted by the A/D converters 13a and 13b, and the waveform correction processing circuit 14 corrects the difference in amplitude and offset between SIN and COS and the phase difference between SIN and COS. is corrected, interpolated by the incremental signal generator 15, and output as displacement information in the X-axis direction.

Similarly, among the interference signals photoelectrically converted by the second detection head 4, the interference signal between the light receiving elements 21a and 21b is DC-cancelled by the differential amplifier 22a, and the light receiving elements 21c and 21d are DC-cancelled by the differential amplifier 22b. is DC canceled by Then, they are converted into digital signals by A/D converters 23a and 23b, respectively. Since there is a phase difference of 90 degrees between the outputs of the differential amplifier 22a and the differential amplifier 22b, it is possible to determine the direction in which the phase of the interference signal advances.

Each interference signal is digitally converted by the A/D converters 23a and 23b, and the waveform correction processing circuit 24 corrects the difference in amplitude and offset between SIN and COS and the phase difference between SIN and COS. is corrected, interpolated by the incremental signal generator 25, and output as displacement information in the Z-axis direction.

The A/D converters of the displacement output units 10 and 20 are synchronized by a clock generator 60. FIG. Incremental signal generators 15 and 25 output relative position information that changes per clock. As a result, the displacement information in the X-axis direction and the displacement information in the Z-axis direction are output at synchronized timing.

As described above, in the present embodiment, by providing the wavelength band selection layer 2d on the surface of the scale 2 and providing the reflective diffraction grating 2b inside the scale 2, the surface area of the scale 2 is not increased. , the displacement in the X-axis direction and the displacement in the Z-axis direction can be detected simultaneously. There is no need to provide a scale corresponding to each direction of displacement to be detected, and the scale can be configured compactly. In other words, the detectable range can be increased with respect to the size of the scale. That is, according to this embodiment, the scale can be made compact, and the installation space for the moving body (member to be measured) can be effectively utilized.

[Second embodiment]
FIG. 9 is a diagram schematically showing the configuration of the displacement detection device according to the second embodiment.
The displacement detection device 201 further includes a third detection head 7 in addition to the first detection head 3 and the second detection head 4 of the first embodiment. The third detection head 7 functions as a "third grating interference type displacement detection head" and outputs displacement information of the two-dimensional scale 202 in the Y-axis direction. Thereby, the displacement detection device 201 can output displacement information in the plane direction and the height direction of the scale 202 .

FIG. 10 is a diagram schematically showing the configuration of the scale 202. As shown in FIG. The upper part of FIG. 10 is a plan view, and the lower part is a sectional view.
The scale 202 has a two-dimensional diffraction grating 202b arranged on a substrate 202a. The diffraction grating 202b is a reflective diffraction grating having a second grating vector parallel to the Y-axis direction. The surface of the diffraction grating 202b is protected with a protective layer 202c. The upper surface of the protective layer 202c is smooth, and the wavelength band selection layer 202d is arranged thereon. The wavelength band selection layer 202d is a multilayer film that transmits light in the first wavelength band and reflects light in the second wavelength band.

A glass substrate, a metal substrate, a resin sheet, or the like is adopted as the base material 202a. The diffraction grating 202b is a reflective diffraction grating and has periodic unevenness. The irregularities are dots arranged at equal intervals in the X-axis direction and the Y-axis direction, and have two lattice vectors in the X-axis direction and the Y-axis direction. The uneven pattern may be formed by etching a chromium film, or may be formed directly on a glass substrate by dry etching. Also, the diffraction grating 202b may be coated with aluminum, gold, silver, or the like, which has a high reflectance. The period Λ of the unevenness is the pitch of the grating and is assumed to be submicron to several microns.

The protective layer 202c has a role of protecting the diffraction grating 202b and a role of arranging the wavelength band selection layer 202d on the upper surface. The wavelength band selection layer 202d is assumed to have a thickness of submicrons to several millimeters so as to efficiently transmit the first wavelength band. The wavelength band selection layer 202d may be formed by depositing SiO ₂ as a material on the protective layer 202c by CVD or sputtering. Alternatively, the cover glass may be adhered with a resin adhesive or the like. At that time, it is preferable to match the refractive index of the adhesive with the refractive index of the cover glass. The wavelength band selection layer 202d has characteristics of transmitting light in a first wavelength band with a center wavelength of 790 nm, for example, and reflecting light in a second wavelength band with a center wavelength of 655 nm (characteristics similar to those of the first embodiment). may have

The third detection head 7 functions on the same principle as the first detection head 3 . The third detection head 7 includes a light source (third light source) that emits light in the first wavelength band, a PBS (third polarizing beam splitter) that splits the beam emitted from the light source into two and then overlaps them again, It includes a mirror (third reflecting means) that reflects each beam, and a light receiving section (third light receiving means) that causes interference between the beams superimposed by the PBS and photoelectrically converts the interference light.

However, the direction in which the third detection head 7 detects displacement is the Y-axis direction, and it is arranged so as to be parallel to the grating vector of the scale 202 . Since the displacement detection device 201 includes the first detection head 3, the second detection head 4, and the third detection head 7, an interference signal indicating displacement in the X-axis direction, an interference signal indicating displacement in the Y-axis direction, and an interference signal indicating displacement in the Z-axis direction. Calculation of displacement detection in three directions of the interference signal indicating displacement in direction is required.

FIG. 11 is a diagram showing a specific example of the computing machine 5. As shown in FIG.
The computer 5 includes a displacement output section 10 that outputs displacement information detected by the first detection head 3 , a displacement output section 20 that outputs displacement information detected by the second detection head 4 , and a third detection head 7 . A displacement output unit 30 for outputting displacement information detected by is provided. The displacement output section 10 and the displacement output section 20 are the same as in the first embodiment. The displacement output unit 30 includes differential amplifiers 32 a and 32 b, A/D converters 33 a and 33 b, a waveform correction processing circuit 34 and an incremental signal generator 35 . Thereby, displacement information in the X-axis direction, the Y-axis direction and the Z-axis direction can be output.

According to the present embodiment, by making the diffraction grating 202b have a two-dimensional structure, not only the X-axis direction and the Z-axis direction shown in the first embodiment, but also the Y-axis direction (third 3 displacements) can be detected simultaneously. That is, the scale can be configured compactly, and the detectable range can be increased with respect to the size of the scale.

[Third Embodiment]
FIG. 12 is a diagram schematically showing the configuration of a displacement detection device according to the third embodiment.
The displacement detection device 301 includes a scale 202, one first detection head 3 (first detection head X1), three second detection heads 4 (second detection heads Z1 to Z3), and two third detection heads. 7 (third detection heads Y1, Y2). The displacement detection device 301 is a 6-degree-of-freedom displacement detection device. Based on the signals detected by these detection heads, the calculator 5 calculates the displacement of the scale 202 in the X-axis direction, the Y-axis direction, the Z-axis direction, the angle around the X-axis direction, and the Y-axis direction. Calculate and output the angle and the angle around the Z-axis direction. Since the principle of each detection head is the same as described above, the explanation is omitted.

FIG. 13 is a diagram showing a specific example of the computing machine 5. As shown in FIG.
The computer 5 includes a displacement output section X1 that outputs displacement information detected by the first detection head 3, displacement output sections Y1 and Y2 that output displacement information detected by the third detection heads Y1 and Y2, and a second detection head. It has displacement output units Z1 to Z3 for outputting displacement information detected by the detection heads Z1 to Z3. Each displacement output section includes a differential amplifier, an A/D converter, a waveform correction processing circuit, and an incremental signal generator, which are the same as those of the first embodiment, so description thereof will be omitted.

12, the displacement value detected by the first detection head X1 is X1, the displacement values detected by the second detection heads Z1 to Z3 are Z1 to Z3, and the Let Y1 and Y2 be the displacement values detected by the three detection heads Y1 and Y2. In that case, the displacement in the X-axis direction, the displacement in the Y-axis direction, the displacement in the Z-axis direction, the angle around the X-axis direction, the angle around the Y-axis direction, and the angle around the Z-axis direction are calculated as follows. be.
X-axis displacement = X1
Y-axis displacement=(Y1+Y2)/2
Z-axis displacement=(Z1+Z2+Z3)/3
Angle around Z-axis = tan ^-1 ((Y1-Y2)/LY)
Angle around Y-axis = tan ^-1 ((Z1-Z3)/LZx)
Angle around X-axis = tan ^-1 ((Z2-((Z1+Z3)/2))/ZLy)

According to this embodiment, by devising the number and arrangement of the detection heads, it is possible to detect displacement with six degrees of freedom while suppressing an increase in the size of the scale 2 .

1 displacement detector, 2 scale, 2a substrate, 2b diffraction grating, 2c protective layer, 2d wavelength band selection layer, 3 first detection head, 3a light source, 3b PBS, 3c mirror, 3d mirror, 3e phase plate with mirror, 3f phase plate with mirror, 4 second detection head, 4a light source, 4b PBS, 4f mirror, 4h scale, 4i PBS, 4j light receiving unit, 5 calculator, 7 third detection head, 10 displacement output unit, 20 displacement output unit , 30 displacement output section, 50 phase plate, 52 half mirror, 54 PBS, 56 PBS, 60 glass substrate, 60 clock generator, 62 transmissive diffraction grating, 201 displacement detector, 202 scale, 202a substrate, 202b diffraction grating , 202c protective layer, 202d wavelength band selective layer, 301 displacement detector.

Claims (4)

A first detection head that detects a first displacement of the member to be measured in a first direction, and a second detection head that detects a second displacement of the member to be measured in a height direction that is a second direction different from the first direction. and a displacement detection member for detecting the displacement of the member to be measured based on the detection signal detected in
a diffraction grating;
a protective layer that protects the diffraction grating;
a wavelength band selection layer that transmits light in a first wavelength band through the protective layer toward the diffraction grating and reflects light in a second wavelength band;
The wavelength band selection layer has a passage area through which the light in the first wavelength band detected by the first detection head passes, and converts the light in the second wavelength band reflected on the passage area into the second wavelength band. A displacement detection member formed so that the second detection head can detect the second displacement based on a detection signal detected by the detection head. A reflective diffraction grating having a first grating vector in a direction parallel to the X-axis direction, which can be placed on a stage movable in the X-axis direction, the Y-axis direction, or the Z-axis direction, and the surface of the reflective diffraction grating a protective layer having a certain thickness; and a wavelength band selection layer that transmits light in a first wavelength band through the protective layer toward the diffraction grating and reflects light in a second wavelength band. a grating scale;
a first grating interference displacement detection head for detecting displacement in the X-axis direction of the diffraction grating scale provided on a member to be measured that can move in the X-axis direction or the Y-axis direction;
a second grating interference displacement detection head for detecting displacement of the diffraction grating scale in a Z-axis direction perpendicular to the XY plane;
Based on the signal detected by the first grating interference type displacement detection head and the signal detected by the second grating interference type displacement detection head, a member to be measured that can move in the X-axis direction, the Y-axis direction, or the Z-axis direction a computer that calculates and outputs the displacement of the provided diffraction grating scale in the X-axis direction and the Z-axis direction;
with
The first grating interference type displacement detection head comprises: a light source of a first wavelength band; and a first light receiving means for causing interference between the beams superimposed by the first polarization beam splitter and photoelectrically converting the interference light,
The second grating interference displacement detection head includes a light source of a second wavelength band, a second polarization beam splitter that splits the beam of the light source of the second wavelength band into two, and a second reflecting means that reflects each of the beams. , a transmissive diffraction grating having a grating vector parallel to the Z-axis for diffracting each of the beams; beam combining means for superimposing the beams; a second light receiving means for interfering the beams and photoelectrically converting the interference light,
A displacement detector that outputs displacement information in the X-axis direction and displacement information in the Z-axis direction of a diffraction grating scale provided on a member to be measured. The diffraction grating scale includes a reflective two-dimensional diffraction grating having a first grating vector parallel to the X-axis direction and a second grating vector parallel to the Y-axis direction; A protective layer having a certain thickness on the surface of the grating, and a wavelength band selection layer that transmits light in a first wavelength band through the protective layer toward the diffraction grating and reflects light in a second wavelength band. and is a two-dimensional grating scale containing
The displacement detection device is
the first grating interference displacement detection head for detecting displacement in the X-axis direction;
the second grating interference displacement detection head for detecting displacement of the diffraction grating scale in a Z-axis direction perpendicular to the XY plane;
a third grating interference displacement detection head for detecting displacement in the Y-axis direction;
Based on the signal detected by the first grating interference displacement detection head, the signal detected by the second grating interference displacement detection head, and the signal detected by the third grating interference displacement detection head, a computer that calculates and outputs the displacement in the X-axis direction, the displacement in the Y-axis direction, and the displacement in the Z-axis direction of the diffraction grating scale that can be installed on a stage that can move in the Y-axis direction or the Z-axis direction;
with
The third grating interference type displacement detection head splits the beams of the light source of the first wavelength band and the light source of the first wavelength band into two, and then reflects the respective beams with the third polarizing beam splitter that superimposes them again. a third reflecting means, and a third light receiving means for causing interference between the beams superimposed by the third polarization beam splitter and photoelectrically converting the interference light,
3. The displacement detection device according to claim 2, which outputs displacement information in the X-axis direction, the displacement information in the Y-axis direction, and the displacement information in the Z-axis direction of a diffraction grating scale provided on the member to be measured. the two-dimensional diffraction grating scale that can be installed on a member to be measured that can move in the X-axis direction, the Y-axis direction, or the Z-axis direction;
one first grating interference displacement detection head for detecting displacement of the two-dimensional diffraction grating scale in the X-axis direction;
three second grating interference displacement detection heads for detecting displacement in the Z- axis direction;
two third grating interference displacement detection heads for detecting displacement in the Y- axis direction;
The one first grating interference type displacement detection head, the three second grating interference type displacement detection heads for detecting displacements in the Z-axis direction, and the third grating interference type displacement detection heads for detecting the two displacements in the Y-axis direction. Displacement in the X-axis direction and the Y-axis direction of the two-dimensional diffraction grating scale that can be mounted on a stage movable in the X-axis direction, the Y-axis direction, or the Z-axis direction based on the signals detected by each of the displacement detection heads. the computer that calculates and outputs the displacement of, the displacement in the Z-axis direction, the angle around the X-axis direction, the angle around the Y-axis direction, and the angle around the Z-axis direction;
4. The displacement detection device according to claim 3 , comprising:

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