JP6786442B2 - Displacement detector - Google Patents

Description

The present invention relates to a displacement detection device that detects a displacement of a surface to be measured by a non-contact sensor using light emitted from a light source, and more particularly to a technique of detecting a displacement of the surface to be measured in a vertical direction.

Conventionally, a displacement detection device using light has been widely used as a device for measuring the displacement and shape of a surface to be measured in a non-contact manner. As a typical example, there is a method of irradiating the surface to be measured with a laser beam and detecting a change in the position of the reflected light by PSD. However, this method has a problem that it is easily affected by the inclination of the surface to be measured, its sensitivity is low, and the resolution of measurement is lowered when the measurement range is widened.

On the other hand, there is a method of using a Michelson interferometer with the surface to be measured as a mirror. This method has a wide detection range and excellent linearity, but when the measurement range is widened, it is subject to changes in the wavelength of the light source and changes in the refractive index of air.

On the other hand, the light emitted from the light source is focused on the surface to be measured by the objective lens, the reflected light reflected on the surface to be measured is focused by the non-point optical element and incident on the light receiving element, and is focused by the astigmatism method. Generate an error signal. Then, the servo mechanism is driven by using the focus error signal, and the objective lens is displaced so that the focal position of the objective lens is the surface to be measured. At this time, there is a method of detecting the displacement of the surface to be measured by reading the scale of the linear scale integrally attached to the objective lens via the connecting member (see, for example, Patent Document 1). This method has the advantage that it is less susceptible to changes in the inclination of the surface to be measured and can measure a large measurement range with high resolution.

In the displacement detection device disclosed in Patent Document 1, in order to improve the accuracy of displacement detection, the numerical aperture (NA: Numerical Aperture) of the objective lens is increased and the beam diameter focused on the surface to be measured is reduced. ing. For example, when the beam diameter formed on the surface to be measured is set to about 2 μm, the detection accuracy of the linear scale is about several nm to about 100 and several nm.

Japanese Unexamined Patent Publication No. 5-89480

However, in the conventional displacement detection device described in Patent Document 1, the objective lens is moved up and down in the optical axis direction by a drive mechanism such as an actuator using a magnet and a coil. Therefore, the mechanical response frequency of the vertical movement of the objective lens is limited by the structure and mass of the actuator. As a result, it was difficult to measure the object to be measured vibrating at high speed with the displacement detection device described in Patent Document 1. In addition, while the detection point can be narrowed down, there is a problem that a large error is generated due to the influence of foreign matter on the object to be measured and small shape changes close to the beam shape, which limits the usage conditions. ..

An object of the present invention is to provide a displacement detection device capable of detecting displacement of a member to be measured in the height direction with high accuracy and capable of high-speed and stable measurement.

In order to solve the above problems and achieve the object of the present invention, the displacement detection device of the present invention includes a first diffraction grating and a head. The first diffraction grating is provided on the surface to be measured of the member to be measured. The head is arranged so as to face the surface to be measured of the member to be measured. The head and the member to be measured are relatively movable in at least one of a direction parallel to the surface to be measured and parallel to the lattice vector direction of the first diffraction grating and a direction orthogonal to the surface to be measured. ..
The head includes a light source that irradiates light, a displacement detection unit, and a light receiving unit. The displacement detection unit divides the light emitted from the light source into a first luminous flux and a second luminous flux, and irradiates the first luminous flux toward the first diffraction grating. The light receiving unit receives the second light flux and the first light flux returned from the first diffraction grating via the displacement detection unit.
The displacement detection unit includes a light flux dividing unit, a second diffraction grating, a reference reflecting member, and a luminous flux coupling unit. The luminous flux dividing unit divides the light into a first luminous flux and a second luminous flux, and irradiates the divided first luminous flux toward the first diffraction grating. The second diffraction grating is divided by the light flux dividing portion, diffracts the first light beam diffracted by the first diffraction grating, and irradiates the first diffraction grating again with the first light flux. The reference reflecting member reflects the second luminous flux divided by the luminous flux dividing portion. The luminous flux coupling portion superimposes the first light flux diffracted by the first diffraction grating and the second diffraction grating and the second luminous flux reflected by the reference reflecting member to irradiate the light receiving portion.
The incident angle of the first light beam on the first diffraction grating, the diffraction angle of the first diffraction grating, the incident angle of the first light beam on the second diffraction grating, and the diffraction angle of the second diffraction grating are heads. And the amount of displacement of the optical path length from the light beam dividing portion of the first light beam to the incident on the first diffraction grating when at least one of the members to be measured is displaced in the direction orthogonal to the surface to be measured, and the first The amount of displacement of the optical path length from the first diffraction grating to the incident on the second diffraction grating in the light beam becomes equal.

According to the displacement detection device of the present invention, since the conventional drive mechanism is not required, heat generated during use can be suppressed. Further, since it is not necessary to drive the drive mechanism, the problem of response frequency can be solved and the usage conditions can be widened.

It is a schematic block diagram which shows the structure of the displacement detection apparatus which concerns on 1st Embodiment of this invention. It is a perspective view which shows the member to be measured and the 1st diffraction grating of the displacement detection apparatus which concerns on 1st Embodiment of this invention. It is explanatory drawing which shows the relationship of the diffraction angle of the 1st diffraction grating and the 2nd diffraction grating in the displacement detection apparatus which concerns on 1st Embodiment of this invention. It is a block diagram which shows the relative position information output means in the displacement detection apparatus which concerns on 1st Embodiment of this invention. A modified example of the second diffraction grating in the displacement detection device according to the first embodiment of the present invention is shown. FIG. 5A is a cross-sectional view showing a modified example of the second diffraction grating, and FIG. 5B is a second. It is sectional drawing which shows the other modification of the diffraction grating of. It is a schematic block diagram which shows the structure of the displacement detection apparatus which concerns on 2nd Embodiment of this invention. It is a block diagram which shows the relative position information output means in the displacement detection apparatus which concerns on 2nd Embodiment of this invention. It is a schematic block diagram which shows the structure of the displacement detection apparatus which concerns on 3rd Embodiment of this invention. It is a schematic block diagram which shows the structure of the 1st displacement detection part and the 2nd displacement detection part in the displacement detection apparatus which concerns on 3rd Embodiment of this invention. It is a schematic block diagram which shows the structure of the 3rd displacement detection part and the 4th displacement detection in the displacement detection apparatus which concerns on 3rd Embodiment of this invention. It is a block diagram which shows the relative position information output means in the displacement detection apparatus which concerns on 3rd Embodiment of this invention. The member to be measured and the first diffraction grating in the displacement detection device according to the third embodiment of the present invention are shown. FIG. 12A is a plan view showing the first diffraction grating, and FIG. 12B is the first diffraction grating. It is sectional drawing which shows the lattice. It is a schematic block diagram which shows the structure of the displacement detection apparatus which concerns on 4th Embodiment of this invention. It is explanatory drawing which shows the relationship between the incident angle and the diffraction angle of the 1st diffraction grating and the 2nd diffraction grating in the displacement detection apparatus which concerns on 4th Embodiment of this invention. It is a schematic block diagram which shows the structure of the displacement detection apparatus which concerns on 5th Embodiment of this invention. It is a schematic block diagram which shows the structure of the displacement detection apparatus which concerns on 6th Embodiment of this invention. It is explanatory drawing which shows the relationship between the incident angle and the diffraction angle of the 1st diffraction grating and the 2nd diffraction grating in the displacement detection apparatus which concerns on 6th Embodiment of this invention. It is a schematic block diagram which shows the structure of the displacement detection apparatus which concerns on 7th Embodiment of this invention. It is explanatory drawing which shows the relationship between the incident angle and the diffraction angle of the 1st diffraction grating and the 2nd diffraction grating in the displacement detection apparatus which concerns on 7th Embodiment of this invention.

Hereinafter, examples of embodiments of the displacement detection device of the present invention will be described with reference to FIGS. 1 to 19. The common members in each figure are designated by the same reference numerals. Moreover, the present invention is not limited to the following forms.
Further, the various lenses described in the following description may be a single lens or a lens group.

1. 1. Example of First Embodiment of Displacement Detection Device First, the configuration of the first embodiment of the displacement detection device of the present invention (hereinafter referred to as “this example”) will be described with reference to FIGS. 1 to 3.

1-1. Configuration Example of Displacement Detection Device FIG. 1 is a schematic configuration diagram showing a configuration of a displacement detection device. FIG. 2 is a perspective view showing a member to be measured provided with a first diffraction grating in the displacement detection device.

The displacement detection device 1 of this example is a displacement detection device that detects the displacement (movement amount) when at least one of the head and the member to be measured is moved.

As shown in FIG. 1, the displacement detection device 1 includes a first diffraction grating 11 provided on the measurement surface 2a of the member 2 to be measured, a head 3, and a relative position information output means 4. The relative position information output means 4 may be housed in the head 3, or may be arranged in a portable information processing terminal or a PC (personal computer) mobile terminal provided outside the head 3.

The head 3 and the member 2 to be measured are in a direction parallel to the surface 2a to be measured and parallel to the lattice vector direction S1 (see FIG. 2) of the first diffraction grating 11 or to the surface 2a to be measured. It is arranged so that it can move relatively in the vertical direction. That is, at least one of the head 3 and the member 2 to be measured is movably arranged in at least one direction parallel to the surface 2a to be measured or perpendicular to the surface 2a to be measured.

Hereinafter, the direction parallel to the surface to be measured 2a and parallel to the lattice vector direction S1 (see FIG. 2) of the first diffraction grating 11 is referred to as the first direction X. Further, the direction parallel to the surface to be measured 2a and orthogonal to the first direction X is defined as the second direction Y. Then, the direction orthogonal to the surface to be measured 2a, that is, the direction orthogonal to the first direction X and the second direction Y is defined as the third direction Z.

As shown in FIG. 2, the member 2 to be measured is formed in a flat plate shape. A first diffraction grating 11 is provided on the surface to be measured 2a of the member to be measured 2 facing the head 3. The first diffraction grating 11 is a reflection type diffraction grating.

The first diffraction grating 11 is composed of a plurality of ridges 11a protruding from the surface to be measured 2a. The plurality of ridges 11a are arranged at predetermined intervals along the first direction X. The distance between two adjacent ridges 11a in the plurality of ridges 11a is the lattice pitch d _{R of} the first diffraction grating 11.

Then, the lattice vector directions S1 of the plurality of ridges 11a are arranged in parallel with the first direction X. Further, the direction (lattice line direction) S2 in which the ridge 11a extends is parallel to the second direction Y on the surface to be measured 2a. The lattice vector direction S1 and the lattice line direction S2 exist on a plane parallel to the surface to be measured 2a. Then, the lattice vector direction S1 does not have to be parallel to the first direction X, and similarly, the lattice line direction S2 does not have to be parallel to the second direction Y.

In this example, an example in which the first diffraction grating 11 is formed by a plurality of ridges 11a protruding from the surface to be measured 2a has been described, but the present invention is not limited to this, and for example, the member 2 to be measured 2 The first diffraction grating 11 may be formed by forming a plurality of groove portions on the surface to be measured 2a.

Further, the first diffraction grating 11 is formed on the member 2 to be measured, which is made of, for example, a glass or silicon substrate. The plurality of ridges 11a constituting the first diffraction grating 11 are formed by depositing a material having a high reflectance such as gold or aluminum on the surface to be measured 2a of the member 2 to be measured. The lattice pitch d _R and the diffraction angle θ of the first diffraction grating 11 will be described later.

The first diffraction grating 11 provided on the member 2 to be measured diffracts the light emitted from the head 3 and returns it to the head 3 again at a predetermined diffraction angle.

The head 3 has a displacement detection unit 5, a light source 6, and a light receiving unit 7 provided in the displacement detection unit 5. The light receiving unit 7 may be arranged inside the displacement detecting unit 5 or may be arranged outside the displacement detecting unit 5. Examples of the light source 6 include a semiconductor laser diode, a superluminescence diode, a gas laser, a solid-state laser, and a light emitting diode.

When a light source having a long coherence distance is used as the light source 6, the tilt allowable range is widened because it is not easily affected by the optical path length difference between the object light and the reference light due to the tilt of the measured surface 2a of the member 2 to be measured. Further, as the interferable distance of the light source 6 becomes shorter, noise due to interference of unnecessary stray light can be prevented, and high-precision measurement can be performed.

Further, when a single mode laser is used as the light source 6, it is desirable to control the temperature of the light source 6 in order to stabilize the wavelength. Further, high frequency superimposition or the like may be added to the light of the single mode laser to reduce the coherence of the light. Further, even when a multi-mode laser is used, by controlling the temperature of the light source 6 with a Peltier element or the like, noise due to interference of unnecessary stray light can be prevented, and more stable measurement becomes possible.

The number of light sources 6 is not limited to one, and the amount of light may be increased by arranging a plurality of light sources 6 and superimposing the lights on each other.

The light L emitted from the light source 6 is incident on the displacement detection unit 5. A lens 16 made of a collimating lens or the like is arranged between the light source 6 and the displacement detection unit 5. The lens 16 collimates the light L emitted from the light source 6 with parallel light. Therefore, the light L collimated with the parallel light by the lens 16 is incident on the displacement detection unit 5.

The displacement detection unit 5 irradiates the light L emitted from the light source 6 toward the first diffraction grating 11 of the member 2 to be measured, and guides the light L returned from the member 2 to the light receiving unit 7. The displacement detection unit 5 includes a second diffraction grating 12, a light beam dividing unit 13, a reference mirror 14 showing an example of a reference light reflecting member, and an object mirror 15 showing an example of an object light reflecting member. It has a first phase plate 17 and a second phase plate 18.

The luminous flux splitting unit 13 is composed of, for example, a polarizing beam splitter. Then, the luminous flux dividing unit 13 reflects the s-polarized light and transmits the p-polarized light. The light L emitted from the light source 6 and collimated with the parallel light by the lens 16 is incident on the luminous flux dividing portion 13. Then, the luminous flux dividing unit 13 divides the light L into two luminous fluxes, a first luminous flux L1 which is an object light and a second luminous flux L2 which is a reference light. In this example, the p-polarized light transmitted through the luminous flux dividing section 13 becomes the first luminous flux L1, and the s-polarized light reflected by the luminous flux dividing section 13 becomes the second luminous flux L2. The first light flux L1 travels toward the first diffraction grating 11, and the second light flux L2 travels toward the reference mirror 14.

In the luminous flux dividing section 13, the light L is divided into a first luminous flux L1 and a second luminous flux L2, and the light amount ratio is equal to that of the first diffraction grating 11 side when incident on the light receiving section 7 described later. , It is preferable to set the ratio so that the reference mirror 14 side has the same amount of light.

Further, a polarizing plate may be provided between the light source 6 and the luminous flux dividing portion 13. This makes it possible to remove light leakage and noise that are slightly present as polarization components orthogonal to s-polarized light and p-polarized light.

Further, although an example in which a polarizing beam splitter is used as the light flux splitting unit 13, the present invention is not limited to this. The luminous flux dividing unit 13 may be configured by, for example, combining a half mirror and a phase plate.

A first phase plate 17 is arranged between the luminous flux dividing portion 13 and the measured surface 2a of the member 2 to be measured, that is, the first diffraction grating 11, and the luminous flux dividing portion 13 and the reference mirror 14 A second phase plate 18 is arranged between them.

The first phase plate 17 and the second phase plate 18 change the polarization direction of the passing light, and are composed of, for example, a quarter wave plate or the like. Therefore, when the passing light is p-polarized light, the first phase plate 17 and the second phase plate 18 are changed to circularly polarized light that rotates in the first direction with the traveling direction as the central axis. Further, when the passing light is circularly polarized light that rotates in the first direction, it is changed to s-polarized light. Further, when the passing light is s-polarized light, it is changed to circularly polarized light that rotates in a second direction opposite to the first direction with the traveling direction as the central axis. Then, when the passing light is circularly polarized light that rotates in the second direction, it is changed to p-polarized light.

Further, in the light source 6, the lens 16, the luminous flux dividing portion 13 and the first phase plate 17, the light transmitted through the luminous flux dividing portion 13, that is, the traveling direction of the first luminous flux L1 is parallel to the third direction Z. It is arranged so as to be. Therefore, the first luminous flux L1 that has passed through the luminous flux dividing portion 13 and passed through the first phase plate 17 is vertically incident on the measured surface 2a of the member 2 to be measured, that is, the first diffraction grating 11. .. As a result, even if the member 2 to be measured is displaced in the third direction Z, the position of the incident point P of the first luminous flux L1 incident on the first diffraction grating 11 changes on the first diffraction grating 11. do not do.

The second diffraction grating 12 is arranged at a position where the first light flux L1 diffracted by the first diffraction grating 11 and returned to the displacement detection unit 5 is incident. The plane of the second diffraction grating 12 is arranged so as to be inclined with respect to the third direction Z. The second diffraction grating 12 is a transmission type diffraction grating that transmits light and diffracts the transmitted light. The lattice pitch d _T and the diffraction angle φ of the second diffraction grating 12 will be described later.

The object mirror 15 is arranged in the direction in which the first luminous flux L1 incident from the first diffraction grating 11 in the second diffraction grating 12 is transmitted. Further, the object mirror 15 is arranged at a position where the first light flux L1 transmitted through the second diffraction grating 12 is vertically incident on the reflection surface. Then, since the first light flux L1 is vertically incident on the object mirror 15, the object mirror 15 is such that the optical path when the first light flux L1 is incident and the optical path after reflection coincide with each other. Reflect.

The first luminous flux L1 reflected by the object mirror 15 passes through the same optical path as the going optical path, and again in the order of the second diffraction grating 12, the first diffraction grating 11, and the first phase plate 17. It is incident on the dividing portion 13. That is, the optical path from the luminous flux dividing portion 13 to the object mirror 15 in the first luminous flux L1 (hereinafter, referred to as “going optical path”) and the optical path from the object mirror 15 to the luminous flux dividing portion 13 (hereinafter, “returning optical path”). ".) Matches. Therefore, the position of being incident on the first diffraction grating 11 again on the return optical path is incident on the same irradiation point P as the outgoing optical path.

Further, the first luminous flux L1 is diffracted twice by the first diffraction grating 11 and the second diffraction grating 12 in the forward optical path and the return optical path.

The reference mirror 14 is arranged in the traveling direction of the second luminous flux L2 divided by the luminous flux dividing portion 13. The reference mirror 14 is arranged so that its reflecting surface is parallel to the surface of the luminous flux dividing portion 13 that irradiates the second luminous flux L2. That is, the reference mirror 14 is arranged at a position where the second luminous flux L2 is perpendicularly incident on the reflecting surface thereof. Then, since the second luminous flux L2 is vertically incident on the reference mirror 14, the reference mirror 14 so that the optical path when the second luminous flux L2 is incident and the optical path after reflection coincide with each other. reflect.

The second luminous flux L2 reflected by the reference mirror 14 passes through the same optical path as the going optical path, passes through the second phase plate 18, and is incident on the luminous flux dividing portion 13 again. The length of the optical path length from the luminous flux dividing portion 13 in the first luminous flux L1 to being reflected by the object mirror 15 and returning to the luminous flux dividing portion 13 again, and from the luminous flux dividing portion 13 in the second luminous flux L2 to the reference mirror 14. The reference mirror 14 and the object mirror 15 are arranged so that the lengths of the optical paths after being reflected and returning to the luminous flux dividing portion 13 are equal.

As a result, even if the wavelength of the light source 6 fluctuates due to changes in atmospheric pressure, humidity, or temperature, the effects of the first luminous flux L1 and the second luminous flux L2 can be made equal. As a result, stable measurement can be performed regardless of the surrounding environment without performing atmospheric pressure correction, humidity correction, or temperature correction. Further, when manufacturing the displacement detection device 1, it is possible to easily adjust the optical path length of the first light flux L1 and the optical path length and the angle of the optical axis of the second light flux L2.

Further, the luminous flux dividing unit 13 superimposes the first luminous flux L1 reflected and returned by the object mirror 15 and the second luminous flux L2 reflected and returned by the reference mirror 14. Then, the luminous flux dividing unit 13 irradiates the light receiving unit 7 with the superimposed first luminous flux L1 and the second luminous flux L2. That is, the luminous flux dividing portion 13 shown in this example has a role as a luminous flux dividing portion for dividing the luminous flux and a role as a luminous flux coupling portion for superimposing the first luminous flux L1 and the second luminous flux L2.

The light receiving unit 7 includes a condenser lens 21, a half mirror 22, a first polarization beam splitter 24, and a second polarization beam splitter 25. Further, on the optical path between the half mirror 22 and the second polarizing beam splitter 25, for example, a light receiving side phase plate 23 made of a 1/4 wave plate or the like is arranged.

The condensing lens 21 condenses the incident first light flux L1 and the second light flux L2 from the light flux dividing unit 13. Further, the condenser lens 21 has a beam diameter appropriately large on the first light receiving element 31, the second light receiving element 32, the third light receiving element 33, and the fourth light receiving element 34, which will be described later. Condenses light. The half mirror 22 divides the light. The light divided by the half mirror 22 is incident on the second polarization beam splitter 25 via the first polarization beam splitter 24 or the light receiving side phase plate 23.

The first polarization beam splitter 24 is arranged so that the polarization direction of the incident light flux is inclined by 45 degrees with respect to the incident surface. A first light receiving element 31 and a second light receiving element 32 are provided on the light emitting port side of the first polarizing beam splitter 24. Further, a third light receiving element 33 and a fourth light receiving element 34 are provided on the light emitting port side of the second polarizing beam splitter 25.

The first polarized beam splitter 24 and the second polarized beam splitter 25 reflect the interference light having the s polarization component, transmit the interference light having the p polarization component, and divide the light.

The first light receiving element 31, the second light receiving element 32, the third light receiving element 33, and the fourth light receiving element 34 receive light and obtain an interference signal. Then, the relative position information output means 4 is connected to the light receiving unit 7. The light receiving unit 7 outputs the interference signal obtained by the first light receiving element 31, the second light receiving element 32, the third light receiving element 33, and the fourth light receiving element 34 to the relative position information output means 4.

1-2. Relationship between First Diffraction Grating and Second Diffraction Grating Next, the relationship between the first diffraction grating 11 and the second diffraction grating 12 having the above-described configuration will be described with reference to FIG.
FIG. 3 is an explanatory diagram showing the relationship between the diffraction angles of the first diffraction grating 11 and the second diffraction grating 12.

［式２］

As shown in FIG. 3, the first luminous flux L1 is vertically incident on the first diffraction grating 11 along the third direction Z. As shown in FIG. 2, the lattice vector direction S1 of the first diffraction grating 11 is parallel to the first direction X. Then, the first diffraction grating 11 diffracts at a diffraction angle θ. Here, assuming that the wavelength of the first luminous flux L1 is λ and the lattice pitch d _R of the first diffraction grating 11, the diffraction angle θ of the first diffraction grating 11 can be calculated by the following equations 1 and 2. it can.
[Equation 1]

[Equation 2]

The first luminous flux L1 diffracted by the first diffraction grating 11 is incident on the second diffraction grating 12 and diffracted by the second diffraction grating 12. The lattice vector direction of the second diffraction grating 12 at this time exists on a plane formed by the first direction X and the third direction Z. Further, the lattice vector direction of the second diffraction grating 12 is inclined at an angle θ _T with respect to the incident angle of the first luminous flux L1 on the first diffraction grating 11. That is, the lattice vector direction of the second diffraction grating 12 is inclined at an angle θ _T with respect to the third direction Z.

［式４］

When the second diffraction grating 12 in the first light beam L1 is incident at an angle φ, the second diffraction grating 12 diffracts at a diffraction angle φ if the second diffraction grating 12 satisfies the Bragg condition. Therefore, as the Bragg condition, the lattice pitch d _T or the diffraction angle φ of the second diffraction grating 12 may be set so as to satisfy the following equations 3 and 4. Note that λ is the wavelength of the first luminous flux L1.
[Equation 3]

[Equation 4]

When the second diffraction grating 12 satisfies the Bragg condition, for example, if the second diffraction grating 12M (see FIG. 5A) of the transmission type volume type hologram described later is used, a very high diffraction efficiency can be obtained. .. However, since the angle of incidence φ on the second diffraction grating 12 and the design of the lattice pitch d _T are limited, the second diffraction grating 12 is a transmission type having no thickness without using a volume type hologram. A diffraction grating may be used. By using a transmission type diffraction grating having no thickness, it is possible to give a degree of freedom in selecting the incident angle and the diffraction angle.

When the second diffraction grating 12 satisfies the Bragg condition, the first light beam L1 diffracted by the second diffraction grating 12 for the second time (the first is the first diffraction grating 11) is reflected by the object mirror 15. Then, it is incident on the second diffraction grating 12 again. As shown in FIGS. 1 and 3, when the member 2 to be measured is not displaced in the third direction Z, the position of the incident point Q incident on the second diffraction grating 12 in the first luminous flux L1 is ,It does not change. Further, even if the member 2 to be measured is displaced in the first direction X or the second direction Y, the position of the incident point Q incident on the second diffraction grating 12 in the first luminous flux L1 does not change. Then, the first luminous flux L1 that has been diffracted the third time by the second diffraction grating 12 is incident on the first diffraction grating 11 and is diffracted the fourth time by the first diffraction grating 11.

Here, an example in which the member 2 to be measured, that is, the first diffraction grating 11 moves in the third direction Z by the length ΔZ will be described.
As shown in FIG. 3, when the first diffraction grating 11 moves upward by a length ΔZ along the third direction Z, that is, in the direction approaching the head 3, it is incident on the incident point P2 of the first diffraction grating 11. At that time, the optical path length of the first luminous flux L1 becomes shorter by the length ΔZ. The first luminous flux L1 is vertically incident on the measured surface 2a of the member 2 to be measured, that is, the first diffraction grating 11. Therefore, even if the member 2 to be measured is displaced in the third direction Z, the positions of the incident points P1 and P2 of the first luminous flux L1 incident on the first diffraction grating 11 are located on the first diffraction grating 11. It does not change.

When the first diffraction grating 11 moves upward along the third direction Z, that is, by the length ΔZ in the direction approaching the head 3, the position of the first light flux L1 that is incident on the second diffraction grating 12 is incident. It changes from the point Q1 to the incident point Q2. The optical path length from the incident point P2 of the first diffraction grating 11 to the incident point Q2 of the second diffraction grating 12 is the first when the first diffraction grating 11 does not move in the third direction Z. The length M1 is longer than the optical path length from the incident point P1 of the diffraction grating 11 to the incident point Q1 of the second diffraction grating 12. Further, the distance from the incident point Q2 of the second diffraction grating 12 to the object mirror 15 is the incident point of the second diffraction grating 12 when the first diffraction grating 11 is not moving in the third direction Z. The length M2 is longer than the optical path length from Q1 to the object mirror 15.

Therefore, if ΔZ = M1 + M2 is satisfied, the optical path length of the first luminous flux L1 becomes constant even if the first diffraction grating 11 moves in the third direction Z. Further, the condition for satisfying ΔZ = M1 + M2 is expressed by the following equation 5 from the diffraction angle θ of the first diffraction grating 11 and the diffraction angle φ of the second diffraction grating 12.
[Equation 5]

Therefore, the diffraction angle θ of the first diffraction grating 11 and the diffraction angle φ of the second diffraction grating 12 satisfy the above equation 5. As a result, the optical path length of the first luminous flux L1 can be kept constant even if the first diffraction grating 11 moves in the third direction Z. It can also be applied to an optical path in which the first light flux L1 is reflected by the object mirror 15 and returns to the light flux dividing portion 13. Therefore, the optical path length of the return optical path in the first luminous flux L1 can always be constant.

As described above, even if the member 2 to be measured is displaced in the first direction X or the second direction Y, the position of the incident point Q incident on the second diffraction grating 12 in the first luminous flux L1 changes. Therefore, the optical path length of the first luminous flux L1 can be kept constant. As a result, even if the first diffraction grating 11 moves in the first direction X, the second direction Y, and the third direction Z, the optical path length of the first luminous flux L1 does not change, so that the first luminous flux L1 The optical path length of the second light flux L2 and the optical path length of the second luminous flux L2 can always be kept constant.

For example, the wavelength λ of the light source 6 is 790 nm, the lattice pitch d _R of the first diffraction grating 11 is 1 μm, the incident angle of the first light beam L1 on the first diffraction grating 11 is 0 degrees, and the second diffraction grating 12 In the case of the grating pitch d _T of, the diffraction grating of the first diffraction grating 11 is θ≈52.2 °, and the diffraction angle of the second diffraction grating 12 is φ≈45.9 °.

1-3. Configuration Example of Relative Position Information Output Means Next, a configuration example of the relative position information output means 4 will be described with reference to FIG.
FIG. 4 is a block diagram showing the relative position information output means 4 of this example.

As shown in FIG. 4, the relative position information output means 4 includes a first differential amplifier 61a, a second differential amplifier 61b, a first A / D converter 62a, and a second A / D converter. It has 62b, a waveform correction processing unit 63, and an incremental signal generator 64.

The first light receiving element 31 and the second light receiving element 32 are connected to the first differential amplifier 61a, and the third light receiving element 33 and the fourth light receiving element 34 are connected to the second differential amplifier 61b. Is connected. A first A / D converter 62a is connected to the first differential amplifier 61a, and a second A / D converter 62b is connected to the second differential amplifier 61b. The first A / D converter 62a and the second A / D converter 62b are connected to the waveform correction processing unit 63. Further, the waveform correction processing unit 63 is connected to the incremental signal generator 64.

The first differential amplifier 61a receives an interference signal from the first light receiving element 31 and the second light receiving element 32, and the second differential amplifier 61b receives the interference signal from the third light receiving element 33 and the fourth light receiving element 34. Receive an interference signal. The first differential amplifier 61a and the second differential amplifier 61b differentially amplify the received interference signal and cancel the DC component of the interference signal.

The signal differentially amplified by the first differential amplifier 61a is A / D converted by the first A / D converter 62a, and the signal amplitude, offset, and phase are corrected by the waveform correction processing unit 63. This signal is calculated in the incremental signal generator 64 as, for example, an A-phase incremental signal.

Similarly, the signal differentially amplified by the second differential amplifier 61b is A / D converted by the second A / D converter 62b. Then, the signal amplitude, the offset, and the phase are corrected by the waveform correction processing unit 63, and the signal is output from the incremental signal generator 64 as an incremental signal of the B phase whose phase is 90 degrees different from that of the A phase.

The two-phase incremental signal thus obtained is discriminated in the forward and reverse directions by a pulse discrimination circuit (not shown) or the like, whereby the head 3 and the member 2 to be measured are in the first direction X or the third direction Z. It is possible to detect whether the relative displacement amount is in the positive direction or the negative direction.

Further, by counting the number of pulses of the incremental signal with a counter (not shown), it is possible to measure how many cycles of the above-mentioned cycle the interference light intensity of the first light flux L1 and the second light flux L2 has changed. As a result, the displacement detection device 1 detects the relative displacement amount (movement amount) between the member 2 to be measured and the head 3.

The relative position information output by the relative position information output means 4 of this example may be the above-mentioned two-phase incremental signal, or may be a signal including the displacement amount and the displacement direction calculated from the incremental signal. ..

1-4. Operation Example of Displacement Detection Device Next, an operation example of the displacement detection device 1 having the above-described configuration will be described with reference to FIGS. 1, 3 and 4.

As shown in FIG. 1, the light L emitted from the light source 6 is collimated by the lens 16 to become parallel light. The parallel light L collimated by the lens 16 is incident on the luminous flux dividing portion 13. The light incident on the luminous flux dividing section 13 is divided into a first luminous flux L1 and a second luminous flux L2. As described above, the luminous flux dividing unit 13 reflects the s-polarized light of the light and transmits the p-polarized light. Therefore, the first luminous flux L1 due to the p-polarized light transmitted through the luminous flux dividing portion 13 is applied to the first phase plate 17. Further, the second luminous flux L2 due to the s-polarized light reflected by the luminous flux dividing portion 13 is applied to the second phase plate 18.

Since the polarization direction of the first light flux L1 is p-polarized light, the first light flux L1 is circularly polarized light that rotates in the first direction with the traveling direction as the central axis by passing through the first phase plate 17. Changes to. Further, since the polarization direction of the second light flux L2 is s-polarized light, the second light flux L2 rotates in the second direction with the traveling direction as the central axis by passing through the second phase plate 18. It changes to circularly polarized light.

The first luminous flux L1 that has passed through the first phase plate 17 is vertically incident on the surface to be measured 2a of the member 2 to be measured, that is, the irradiation point P of the first diffraction grating 11. Then, as shown in FIG. 3, the first luminous flux L1 is diffracted by the first diffraction grating 11 at a diffraction angle θ. The first luminous flux L1 to which the second diffraction is performed is incident on the second diffraction grating 12 at the irradiation point Q (see FIG. 1) at an incident angle φ. As described above, since the second diffraction grating 12 satisfies the Bragg condition, the first luminous flux L1 is diffracted by the second diffraction grating 12 at a diffraction angle φ.

The first luminous flux L1 diffracted by the second diffraction grating 12 is vertically incident on the object mirror 15. Then, the first luminous flux L1 is reflected again by the object mirror 15 toward the second diffraction grating 12. The first luminous flux L1 is incident on the second diffraction grating 12 at an incident angle φ. At this time, the first luminous flux L1 is incident on the irradiation point Q in the second diffraction grating 12 which is the same as the optical path. Then, the second diffraction grating 12 performs the third diffraction, and the first diffraction grating 11 is incident at the same irradiation point P as the optical path at the incident angle θ.

In this way, by setting the irradiation point P of the going optical path and the irradiation point P of the returning optical path with respect to the first diffraction grating 11 to the same point, the influence generated when the first diffraction grating 11 is tilted can be reduced. Can be done. Further, the same effect can be obtained by setting the irradiation point Q of the outgoing optical path and the irradiation point Q of the returning optical path with respect to the second diffraction grating 12 to the same point. Furthermore, the detection accuracy can be further improved as compared with the conventional displacement detection device that detects the center points of the two points as virtual measurement points.

Next, the first luminous flux L1 is diffracted a fourth time by the first diffraction grating 11 and is irradiated on the first phase plate 17. The polarization direction of the first light flux L1 at this time is circularly polarized light that rotates in the first direction with the traveling direction as the central axis. Therefore, the first luminous flux L1 is changed by the first phase plate 17 to s-polarized light which is orthogonal to the p-polarized light which is the going polarization direction.

On the other hand, the second luminous flux L2 irradiated on the reference mirror 14 is reflected by the reference mirror 14 and again irradiated on the second phase plate 18. The polarization direction of the second luminous flux L2 at this time is circular polarization that rotates in the second direction with the traveling direction as the central axis. Therefore, the second luminous flux L2 is changed by the second phase plate 18 to p-polarized light which is orthogonal to the s-polarized light which is the going polarization direction.

The first luminous flux L1 that has passed through the first phase plate 17 is incident on the luminous flux dividing portion 13 again, and the second luminous flux L2 that has passed through the second phase plate 18 is incident on the luminous flux dividing portion 13 again. At this time, since the polarization direction of the first light flux L1 is s-polarized light, it is reflected by the light flux dividing unit 13 and irradiated to the light receiving unit 7. Further, since the polarization direction of the second light flux L2 is p-polarized light, it passes through the light flux dividing unit 13 and irradiates the light receiving unit 7. Therefore, a light flux in which the first light flux L1 and the second light flux L2 of linearly polarized light which are orthogonal to each other overlap each other is incident on the light receiving unit 7.

The light flux is focused by the condenser lens 21 and is applied to the half mirror 22. The half mirror 22 divides the luminous flux into two lights. The luminous flux transmitted through the half mirror 22 is incident on the first polarizing beam splitter 24.

Here, in the first polarization beam splitter 24, the polarization directions of the first light flux L1 and the second light flux L2, which are 90 degrees different from each other, are polarized with respect to the incident surface of the first polarization beam splitter 24, respectively. It is tilted so that the direction is tilted by 45 degrees. As a result, the first light flux L1 and the second light flux L2 have a p-polarization component and an s-polarization component with respect to the first polarization beam splitter 24, respectively. Therefore, the first light flux L1 and the second light flux L2 that have passed through the first polarization beam splitter 24 interfere with each other with polarized light having the same polarization direction. Therefore, the first luminous flux L1 and the second luminous flux L2 can be caused to interfere with each other by the first polarization beam splitter 24.

Similarly, the first light flux L1 and the second light flux L2 reflected by the first polarization beam splitter 24 interfere with each other having the same polarization direction with respect to the first polarization beam splitter 24. Therefore, it can be interfered by the first polarization beam splitter 24.

The interference light with the first luminous flux L1 and the second luminous flux L2 transmitted through the first polarizing beam splitter 24 is received by the first light receiving element 31. Further, the interference light with the first light flux L1 and the second light flux L2 reflected by the first polarization beam splitter 24 is received by the second light receiving element 32. Here, the interference signals photoelectrically converted by the first light receiving element 31 and the second light receiving element 32 are signals having 180-degree phases different from each other.

Then, as the interference signal obtained by the first light receiving element 31 and the second light receiving element 32, an interference signal of A × cos (2 × K1x + 2 × B × K2z + δ) is obtained. Here, A is the amplitude of interference, and K1 is the wave number of the first diffraction grating 11 represented by 2π / d _R. Further, x indicates the amount of movement of the first diffraction grating 11, that is, the amount of displacement of the head 3 and the member 2 to be measured relative to the first direction X. On the other hand, K2 is the wave number of the second diffraction grating 12 represented by 2π / d _T. z indicates the amount of movement of the second diffraction grating 12 in the lattice vector direction in the first luminous flux L1 incident on the second diffraction grating 12. Note that d _R is the lattice pitch of the first diffraction grating 11, and d _T is the lattice pitch of the second diffraction grating 12. Further, δ indicates the initial phase.

Further, B is a coefficient associated with the inclination of the lattice vector direction of the second diffraction grating 12 with respect to the third direction Z at an inclination angle θ _T. Then, when the angle of incidence on the second diffraction grating 12 (the diffraction angle is the same under Bragg conditions) is φ, it can be indicated by B = cosθ _T + sinθ _T × tanφ.

Here, when the head 3 and the member 2 to be measured move by x / 2 relative to the first direction X, the irradiation point of the first luminous flux L1 irradiated to the first diffraction grating 11 is in the first direction. Move x / 2 to X. That is, the first luminous flux L1 moves on the first diffraction grating 11 in the first direction X by x / 2. Therefore, the phase of K1x is added to the first luminous flux L1, and the interference light that causes light and darkness of one cycle is received by the first light receiving element 31 and the second light receiving element 32.

Even if the head 3 and the member 2 to be measured move relatively in the first direction X, the irradiation point on the second diffraction grating 12 in the first luminous flux L1 does not change. Therefore, only the phase diffracted by the first diffraction grating 11 is added to the first luminous flux L1.

Further, when the head 3 and the member 2 to be measured move by Z / (2 × B) relative to the third direction Z, the irradiation point of the first luminous flux L1 irradiated to the second diffraction grating 12 becomes the second irradiation point. It moves by Z / 2 in the lattice vector direction of the diffraction grating 12 of 2. That is, the first luminous flux L1 moves on the second diffraction grating 12 by Z / 2 in the lattice vector direction. Therefore, the phase of K2z is added to the first luminous flux L1, and the interference light that causes light and darkness of one cycle is received by the first light receiving element 31 and the second light receiving element 32.

As described above, the first luminous flux L1 is incident on the first diffraction grating 11 in parallel with the third direction Z. Therefore, the first luminous flux L1 is vertically incident on the first diffraction grating 11. Therefore, even if the head 3 and the member 2 to be measured move relatively in the third direction Z, the irradiation point on the first diffraction grating 11 in the first luminous flux L1 does not change. Therefore, only the phase diffracted by the second diffraction grating 12 is added to the first luminous flux L1.

Further, the diffraction angle θ of the first diffraction grating 11 and the diffraction angle φ of the second diffraction grating 12 satisfy the above equation 5. Therefore, even if the head 3 and the member 2 to be measured move in ΔZ relative to the third direction Z, the sum of ΔZ and M1 + M2 shown in FIG. 3 is always 0. As a result, even if the optical path length of the first luminous flux L1 does not change and the head 3 and the member 2 to be measured move in ΔZ relative to the third direction Z, the second diffraction in the first luminous flux L1. Only the position incident on the grating 12 changes.

Here, as described above, the interference signal obtained by the first light receiving element 31 and the second light receiving element 32 does not contain a component related to the wavelength of the light source 6. Therefore, even if the wavelength of the light source fluctuates due to changes in atmospheric pressure, humidity, and temperature, the interference intensity is not affected.

On the other hand, as shown in FIG. 1, the light flux reflected by the half mirror 22 is incident on the light receiving side phase plate 23. The light flux composed of the first light flux L1 and the second light flux L2, which are linearly polarized light whose polarization directions differ from each other by 90 degrees, becomes circularly polarized light in opposite directions by passing through the light receiving side phase plate 23. Since the circularly polarized light rotating in opposite directions is on the same optical path, they are superposed to become linearly polarized light and are incident on the second polarization beam splitter 25.

The linearly polarized s-polarized light component is reflected by the second polarization beam splitter 25 and received by the third light receiving element 33. Further, the p-polarized light component passes through the second polarization beam splitter 25 and is received by the fourth light receiving element 34.

As described above, the linearly polarized light incident on the second polarization beam splitter 25 is generated by superimposing circularly polarized light in opposite directions. Then, the polarization direction of the linearly polarized light incident on the second polarization beam splitter 25 rotates 1/2 when the head 3 and the member 2 to be measured move relative to the first direction X by d _R / 2. Further, even if the head 3 and the member 2 to be measured move by d _T / (2 × B) relative to the first direction X, the polarization direction of the linearly polarized light incident on the second polarization beam splitter 25 remains unchanged. , 1/2 rotation.

Therefore, even in the third light receiving element 33 and the fourth light receiving element 34, the interference signal of A × cos (2 × K1x + 2 × B × K2z + δ') is obtained in the same manner as in the first light receiving element 31 and the second light receiving element 32. Is obtained. δ'is the initial phase.

Further, the signals photoelectrically converted by the third light receiving element 33 and the fourth light receiving element 34 are 180 degrees out of phase.

In this example, the second polarization beam splitter 25 that splits the light flux received by the third light receiving element 33 and the fourth light receiving element 34 is tilted 45 degrees with respect to the first polarization beam splitter 24. It is arranged. Therefore, the signals obtained by the third light receiving element 33 and the fourth light receiving element 34 are 90 degrees out of phase with the signals obtained by the first light receiving element 31 and the second light receiving element 32.

Therefore, for example, the signal obtained by the first light receiving element 31 and the second light receiving element 32 is used as a sin signal, and the signal obtained by the third light receiving element 33 and the fourth light receiving element 34 is used as a cos signal. Can be obtained.

The signal obtained by these light receiving elements is calculated by the relative position information output means 4, and the relative displacement amount between the head 3 and the member 2 to be measured is counted. Thereby, the relative displacement amount between the head 3 and the member 2 to be measured can be detected.

In the displacement detection device 1 of this example, the interference signal obtained by the light receiving unit 7 of the displacement detection unit 5 includes displacement information in the first direction X and the third direction Z. Therefore, it is applied to a device that detects the relative displacement of the head 3 and the member 2 to be measured in the first direction X when the head 3 and the member 2 to be measured move relatively only in the first direction X. it can. Alternatively, it can also be used as a device for detecting the relative displacement of the head 3 or the member 2 to be measured in the third direction Z when the head 3 and the member 2 to be measured move relatively only in the third direction Z. Applicable. That is, the displacement detection device 1 of this example has two ways of use in one device.

1-5. Second Modification Example of the Diffraction Grating Next, a modification of the diffraction grating will be described with reference to FIGS. 5A and 5B.
FIG. 5A is a cross-sectional view showing a modified example of the second diffraction grating, and FIG. 5B is a cross-sectional view showing another modified example of the second diffraction grating.

The second diffraction grating 12M shown in FIG. 5A is a so-called volume type hologram using a photographic plate. An absorption type hologram may be used, but here, a phase type hologram will be described. The lattice portion 12b in the second diffraction grating 12M is formed, for example, as follows. First, an emulsion of a silver salt sensitive to light is applied to one surface of a glass substrate 12a, interference fringes are exposed, and the glass substrate 12a is developed and then bleached. As a result, the lattice portion 12b is formed with a portion where silver particles remain and a portion where silver particles do not remain.

Here, the place where the silver particles remain has a high refractive index, and the place where the silver particles do not remain has a low refractive index. That is, it is a phase type hologram. Further, as a material, a photopolymer for hologram recording may be used instead of the photographic plate.

The second diffraction grating 12N shown in FIG. 5B has a lattice portion 12c made of, for example, chromium (Cr) formed on one surface of a substantially transparent glass substrate 12a. Generally, the lattice portion 12c has a thickness of 1 μm or less because a thin film such as chromium is formed on one surface of the glass substrate 12a by vacuum deposition.

Further, in the second diffraction grating 12M shown in FIG. 5A and the second diffraction grating 12N shown in FIG. 5B, when the incident angle is φa and the diffraction angle is φb, when the Bragg condition of the following formula 6 is satisfied, φa = It becomes φb. Note that n is an integer.
[Equation 6]

Further, in the case of the second diffraction grating 12M shown in FIG. 5A, the output of the diffracted light diffracted by the second diffraction grating 12M can be maximized when the Bragg condition is satisfied. That is, it is possible to prevent the amount of diffracted light diffracted by the second diffraction grating 12M from decreasing.

2. Second Embodiment Example Next, the displacement detection device according to the second embodiment will be described with reference to FIGS. 6 and 7.
FIG. 6 is a schematic configuration diagram showing the configuration of the displacement detection device according to the second embodiment, and FIG. 7 is a block diagram showing the relative position information output means in the displacement detection device according to the second embodiment. Is.

The displacement detection device 101 according to the second embodiment is a displacement detection device capable of outputting two-dimensional displacement information in the first direction X and the third direction Z. Therefore, here, the same reference numerals are given to the parts common to the displacement detection device 1 according to the first embodiment, and duplicate description will be omitted.

As shown in FIG. 6, the displacement detection device 101 includes a member 2 to be measured provided with a first diffraction grating 111, a head 3, and a relative position information output means 104. The head 3 and the member 2 to be measured are configured to be relatively movable in two directions, a first direction X and a third direction Z.

In the first diffraction grating 111, the direction of the diffracted light is directed to one side of the first direction X on the first displacement detection unit 5A side of the head 103, which will be described later. Further, in the first diffraction grating 111, the direction of the diffracted light is directed to the other side of the first direction X on the second displacement detection unit 5B side of the head 103 described later. Therefore, it is preferable to use a blazed diffraction grating as the first diffraction grating 111.

The head 103 includes a first displacement detection unit 5A, a second displacement detection unit 5B, a light source 6, a lens 16, a light source side phase plate 106, and an optical distribution unit 107. The first displacement detection unit 5A is arranged on one side of the first direction X of the head 3, and the second displacement detection unit 5B is arranged on the other side of the first direction X of the head 3.

A light source 6, a lens 16, a light source side phase plate 106, and an optical distribution unit 107 are arranged between the first displacement detection unit 5A and the first direction X in the second displacement detection unit 5B. The light source side phase plate 106 adjusts the polarization axis of the light L emitted from the light source 6, and adjusts, for example, to circularly polarized light inclined by 45 ° with respect to the optical axis.

The light L that has passed through the light source side phase plate 106 is irradiated to the light distribution unit 107. The light distribution unit 107 is composed of, for example, a mirror 107a and a half mirror 107b. The half mirror 107b is arranged closer to the light source 6 than the mirror 107a.

The reflectance of the half mirror 107b to the other side of the first direction X is set to 50%. Therefore, the half mirror 107b equally distributes the light L that has passed through the light source side phase plate 106 toward the mirror 107a side in the third direction Z and the other side of the first direction X. Then, the light LB reflected by the half mirror 107b is irradiated toward the luminous flux dividing unit 13B of the second displacement detecting unit 5B.

The light LA transmitted through the half mirror 107b is incident on the mirror 107a. The mirror 107a reflects the incident light LA toward the light flux dividing unit 13A of the first displacement detecting unit 5A.

The first displacement detection unit 5A includes a light receiving unit 7A, a second diffraction grating 12A, a luminous flux dividing unit 13A, a reference mirror 14A, and a reference mirror 14A, similarly to the displacement detecting unit 5 according to the first embodiment. An object mirror 15A, a first phase plate 17A, and a second phase plate 18A are provided. The light receiving unit 7A is connected to the first relative position information output unit 4A of the relative position information output means 104. Then, the light receiving unit 7A transmits the obtained interference signal to the first relative position information output unit 4A.

The light receiving unit 7A of the first displacement detection unit 5A obtains the interference signal represented by the following formula 7. Here, A1 is the amplitude of interference.
[Equation 7]

The second displacement detection unit 5B includes a light receiving unit 7B, a second diffraction grating 12B, a luminous flux division unit 13B, a reference mirror 14B, and a reference mirror 14B, similarly to the displacement detection unit 5 according to the first embodiment. An object mirror 15B, a first phase plate 17B, and a second phase plate 18B are provided. The light receiving unit 7B is connected to the second relative position information output unit 4B of the relative position information output means 104. Then, the light receiving unit 7B transmits the obtained interference signal to the second relative position information output unit 4B.

Further, the second diffraction grating 12B, the luminous flux dividing unit 13B, the reference mirror 14B, the object mirror 15B, the first phase plate 17B and the second phase plate 18B constituting the second displacement detection unit 5B are the first. It is inverted and arranged along the first direction X with respect to the displacement detection unit 5A.

The light receiving unit 7B of the second displacement detection unit 5B obtains the interference signal represented by the following equation 8. Here, A2 is the amplitude of interference.
[Equation 8]

As shown in the above equations 7 and 8, the displacement information in the first direction X in the interference signal obtained by the light receiving unit 7A of the first displacement detection unit 5A and the light receiving unit 7B of the second displacement detection unit 5B is positive or negative. Is different.

As shown in FIG. 7, the relative position information output means 104 includes a first relative position information output unit 4A, a second relative position information output unit 4B, and a calculation unit 114. As described above, the displacement information in the first direction X in the interference signal obtained by the light receiving unit 7A of the first displacement detection unit 5A and the light receiving unit 7B of the second displacement detection unit 5B is different in positive and negative.

Therefore, when the displacement information A from the first relative position information output unit 4A and the displacement information B from the second relative position information output unit 4B are added together, only the displacement information in the third direction Z can be extracted. .. Further, by subtracting the displacement information B of the second relative position information output unit 4B from the displacement information A of the first relative position information output unit 4A, only the displacement information of the first direction X can be extracted.

Then, the calculation unit 114 adds the displacement information A from the first relative position information output unit 4A and the displacement information B from the second relative position information output unit 4B and divides by 2, so that the head 103 and the cover are covered. The displacement information of the position relative to the measuring member 2 in the third direction Z is calculated. Further, the calculation unit 114 subtracts the displacement information B of the second relative position information output unit 4B from the displacement information A of the first relative position information output unit 4A and divides it by 2, so that the head 103 and the member 2 to be measured The displacement information in the first direction X is calculated.

As a result, according to the displacement detection device 101 according to the second embodiment, it is possible to output two-dimensional displacement information in the first direction X and the third direction Z.

Since other configurations are the same as those of the displacement detection device 1 according to the first embodiment, their description will be omitted. The displacement detection device 101 having such a configuration can also obtain the same effects as the displacement detection device 1 according to the above-described first embodiment.

3. 3. Example of Third Embodiment Next, the displacement detection device according to the third embodiment will be described with reference to FIGS. 8 to 12.
FIG. 8 is a schematic configuration diagram showing the configuration of the displacement detection device according to the third embodiment. FIG. 9 is a schematic configuration diagram showing the configurations of the first displacement detection unit and the second displacement detection unit in the displacement detection device according to the third embodiment. FIG. 10 is a schematic configuration diagram showing a configuration of a third displacement detection unit and a fourth displacement detection in the displacement detection device according to the third embodiment. FIG. 11 is a block diagram showing a relative position information output means in the displacement detection device according to the third embodiment. 12A and 12B show the first diffraction grating in the displacement detection device according to the third embodiment.

The displacement detection device 101 according to the second embodiment has a second direction Y orthogonal to the first direction X, the third direction Z, the first direction X, and the third direction Z. It is a displacement detection device that can output three-dimensional displacement information. Therefore, here, the same reference numerals are given to the parts common to the displacement detection device 1 according to the first embodiment, and duplicate description will be omitted.

As shown in FIGS. 8, 9 and 10, the displacement detection device 201 includes a member 202 to be measured provided with a first diffraction grating 211, a head 203, and a relative position information output means 204. .. The head 203 and the member 202 to be measured are configured to be relatively movable in the three directions of the first direction X, the second direction Y, and the third direction Z.

As shown in FIGS. 12A and 12B, the member 202 to be measured is formed in a flat plate shape. A first diffraction grating 211 is provided on the surface to be measured 202a of the member to be measured 202. The first diffraction grating 211 has a first lattice vector direction parallel to the first direction X and a second lattice vector direction parallel to the second direction Y.

Further, the first diffraction grating 211 is composed of a plurality of protrusions 211a. The plurality of protrusions 211a project from the surface to be measured 202a in the third direction Z. The plurality of protrusions 211a are arranged in a grid pattern at intervals along the first lattice vector direction parallel to the first direction X and the second lattice vector direction parallel to the second direction Y. ing.

An example in which the first diffraction grating 211 according to the third embodiment is composed of a plurality of protrusions 211a has been described, but the present invention is not limited to this, and for example, the surface to be measured of the member 202 to be measured. The first diffraction grating 211 may be formed by a plurality of recesses formed in 202a.

As shown in FIGS. 8, 9 and 10, the head 203 includes a first displacement detection unit 5A, a second displacement detection unit 5B, a third displacement detection unit 5C, a fourth displacement detection unit 5D, and a light source. 6, the lens 16, the light source side phase plate 106, and the light distribution unit 207 are provided. The first displacement detection unit 5A is arranged on one side of the first direction X of the head 3, and the second displacement detection unit 5B is arranged on the other side of the first direction X of the head 3. Further, the third displacement detection unit 5C is arranged on one side of the second direction Y of the head 3, and the fourth displacement detection unit 5D is arranged on the other side of the second direction Y of the head 3.

A light source 6, a lens 16, a light source side phase plate 106, and an optical distribution unit 207 are arranged between the first displacement detection unit 5A, the second displacement detection unit 5B, the third displacement detection unit 5C, and the fourth displacement detection unit 5D. Has been done. That is, the light source 6, the lens 16, the light source side phase plate 106, and the light distribution unit 207 are arranged at the center of the head 3 in the first direction X and the second direction Y.

The light distribution unit 207 has a mirror 207a, a first half mirror 207b, a second half mirror 207c, and a third half mirror 207d. The light distribution unit 207 is arranged in the order of the mirror 207a, the first half mirror 207b, the second half mirror 207c, and the third half mirror 207d along the third direction Z from the side to be measured 202 in the third direction Z. ing. That is, the third half mirror 207d is arranged on the light source 6 side.

The reflectance of the third half mirror 207d to the other side in the second direction Y is set to 25%. The reflectance of the second half mirror 207c to one side in the second direction Y is set to 33.3%. The reflectance of the first half mirror 207b to the other side of the first direction X is set to 50%.

The light LD reflected from the third half mirror 207d is irradiated toward the luminous flux dividing unit 13D of the fourth displacement detecting unit 5D. The light LC transmitted through the third half mirror 207d and reflected by the second half mirror 207c is irradiated toward the luminous flux dividing unit 13C of the third displacement detecting unit 5C. The light LB that has passed through the third half mirror 207d and the second half mirror 207c and reflected by the first half mirror 207b is irradiated toward the light flux dividing portion 13B of the second displacement detection unit 5B. Then, the light LA transmitted through the third half mirror 207d, the second half mirror 207c, and the first half mirror 207b is reflected by the mirror 207a toward the luminous flux dividing portion 13A of the first displacement detecting portion 5A.

When the light distribution unit 207 has a non-polarizing characteristic, the light polarization axis in the space from the light distribution unit 207 to the light flux dividing units 13A, 13B, 13C, 13D of each displacement detection unit 5A, 5B, 5C, 5D. It is not necessary to provide a phase plate or the like for adjusting the light flux. Therefore, the configuration of the displacement detection device 201 can be simplified.

Since the first displacement detection unit 5A and the second displacement detection unit 5B have the same configuration as the first displacement detection unit 5A and the second displacement detection unit 5B according to the second embodiment. The description thereof will be omitted.

The light receiving unit 7A of the first displacement detection unit 5A obtains the interference signal represented by the following equation 9. Here, A1 is the amplitude of interference.
[Equation 9]

Further, the light receiving unit 7B of the second displacement detection unit 5B obtains the interference signal represented by the following equation 10. Here, A2 is the amplitude of interference.
[Equation 10]

The third displacement detection unit 5C, like the displacement detection unit 5 according to the first embodiment, includes a light receiving unit 7C, a second diffraction grating 12C, a luminous flux dividing unit 13C, a reference mirror 14C, and the like. An object mirror 15C, a first phase plate 17C, and a second phase plate 18C are provided. Further, the lattice vector direction of the second diffraction grating 12C exists on a plane formed by the second direction Y and the third direction Z. The light receiving unit 7C is connected to the third relative position information output unit 4C of the relative position information output means 204. Then, the light receiving unit 7C transmits the obtained interference signal to the third relative position information output unit 4C.

The light receiving unit 7C of the third displacement detecting unit 5C obtains the interference signal represented by the following equation 11. Here, A3 is the amplitude of interference. y indicates the amount of movement of the first diffraction grating 211, that is, the amount of displacement of the head 203 and the member 202 to be measured relative to the second direction Y.
[Equation 11]

The fourth displacement detection unit 5D includes a light receiving unit 7D, a second diffraction grating 12D, a luminous flux division unit 13D, a reference mirror 14D, and a reference mirror 14D, similarly to the displacement detection unit 5 according to the first embodiment. An object mirror 15D, a first phase plate 17D, and a second phase plate 18D are provided. Further, the lattice vector direction of the second diffraction grating 12C exists on a plane formed by the second direction Y and the third direction Z. The light receiving unit 7D is connected to the fourth relative position information output unit 4D of the relative position information output means 204. Then, the light receiving unit 7D transmits the obtained interference signal to the fourth relative position information output unit 4D.

Further, the second diffraction grating 12D, the luminous flux dividing unit 13D, the reference mirror 14D, the object mirror 15D, the first phase plate 17D and the second phase plate 18D constituting the fourth displacement detection unit 5D are the first. It is inverted and arranged along the second direction Y with respect to the displacement detection unit 5A.

The light receiving unit 7D of the fourth displacement detection unit 5D obtains the interference signal represented by the following equation 12. Here, A4 is the amplitude of interference.
[Equation 12]

As shown in FIG. 11, the relative position information output means 204 includes a first relative position information output unit 4A, a second relative position information output unit 4B, a third relative position information output unit 4C, and a fourth relative position information. It has an output unit 4D and a calculation unit 214.

As described above, the displacement information in the first direction X in the interference signal obtained by the light receiving unit 7A of the first displacement detection unit 5A and the light receiving unit 7B of the second displacement detection unit 5B is different in positive and negative. Further, the displacement information in the second direction Y from which the light receiving unit 7C of the third displacement detection unit 5C and the light receiving unit of the fourth displacement detection unit 5D are obtained are different in positive and negative.

Therefore, by subtracting the displacement information B of the second relative position information output unit 4B from the displacement information A of the first relative position information output unit 4A, only the displacement information of the first direction X can be extracted. Further, by subtracting the displacement information D of the fourth relative position information output unit 4D from the displacement information C of the third relative position information output unit 4C, only the displacement information in the second direction Y can be extracted. Then, all the displacement information A, B, C, D of the first relative position information output unit 4A, the second relative position information output unit 4B, the third relative position information output unit 4C, and the fourth relative position information output unit 4D are displayed. By adding them together, only the displacement information in the third direction Z can be extracted.

Then, the calculation unit 214 includes all the displacement information A and B of the first relative position information output unit 4A, the second relative position information output unit 4B, the third relative position information output unit 4C, and the fourth relative position information output unit 4D. , C, and D are added and divided by 4, so that the displacement information of the relative position of the head 103 and the member 202 to be measured in the third direction Z is calculated.

Further, the calculation unit 214 subtracts the displacement information B of the second relative position information output unit 4B from the displacement information A of the first relative position information output unit 4A and divides it by 2, so that the head 103 and the member 202 to be measured The displacement information in the first direction X is calculated. The calculation unit 214 subtracts the displacement information D of the fourth relative position information output unit 4D from the displacement information C of the third relative position information output unit 4C and divides it by 2, so that the head 103 and the member 202 to be measured are second. The displacement information in the direction Y of is calculated.

As a result, according to the displacement detection device 201 according to the third embodiment, it is possible to output three-dimensional displacement information in the first direction X, the second direction Y, and the third direction Z. it can.

Since other configurations are the same as those of the displacement detection device 1 according to the first embodiment, their description will be omitted. The displacement detection device 201 having such a configuration can also obtain the same effects as the displacement detection device 1 according to the above-described first embodiment.

Further, in the fourth embodiment, an example in which the first lattice vector direction and the second lattice vector direction of the first diffraction grating 211 are orthogonal to each other has been described, but the present invention is not limited to this. The first lattice vector direction and the second lattice vector direction do not have to be orthogonal to each other, and may intersect each other on the measured surface 202a of the member 202 to be measured. The first displacement detection unit 5A and the second displacement detection unit 5B are arranged along the first lattice vector direction, and the third displacement detection unit 5C and the fourth displacement detection unit 5D are arranged along the second lattice vector direction. Is placed.

4. Example of Fourth Embodiment Next, the displacement detection device according to the fourth embodiment will be described with reference to FIGS. 13 and 14.
FIG. 13 is a schematic configuration diagram showing the configuration of the displacement detection device according to the fourth embodiment, and FIG. 14 shows the first diffraction grating and the second diffraction grating in the displacement detection device according to the fourth embodiment. It is explanatory drawing which shows the relationship between the incident angle and the diffraction angle of a diffraction grating.

The displacement detection device 301 according to the fourth embodiment is different from the displacement detection device 1 according to the first embodiment in that the first luminous flux L1 is perpendicular to the first diffraction grating. The point where it does not enter and the point where the second diffraction grating does not satisfy the Bragg condition. Therefore, here, the same reference numerals are given to the parts common to the displacement detection device 1 according to the first embodiment, and duplicate description will be omitted.

As shown in FIG. 13, the displacement detection device 301 includes a head (not shown), a first diffraction grating 11 provided on the member 2 to be measured, and a relative position information output means 304. Further, in the head, the light source 6, the light receiving unit 7, the lens 16, the luminous flux dividing unit 313, the second diffraction grating 312, the reference mirror 314, the object mirror 315, and the first phase A plate 317 and a second phase plate 318 are arranged.

In the displacement detection device 301 according to the fourth embodiment, the first luminous flux L1 does not enter perpendicularly to the first diffraction grating. Therefore, the light source 6, the lens 16, the luminous flux dividing portion 313, the second diffraction grating 312, the reference mirror 314, the object mirror 315, the first phase plate 317, and the second phase plate 318 are the first implementations. It is arranged at a position different from that of the displacement detection device 1 according to the embodiment.

The reference mirror 314 is arranged at a position where the optical path length of the second luminous flux L2 is the same as the optical path length of the first luminous flux L1. Further, the reference mirror 314 is arranged at a position where the second luminous flux L2 emitted from the luminous flux dividing portion 313 is vertically incident. Further, the object mirror 315 is arranged at a position where the first luminous flux L1 diffracted by the second diffraction grating 312 is vertically incident.

Next, with reference to FIG. 14, the relationship between the incident angle θ _R and the diffraction angle θ of the first diffraction grating 11 and the incident angle θ ₁ and the diffraction angle θ ₂ to the second diffraction grating 12 will be described.
As shown in FIG. 14, when the first diffraction grating 11 moves upward along the third direction Z, that is, in the direction approaching the head by a length ΔZ, it becomes the first diffraction grating 11 in the first luminous flux L1. The position of incidence changes from the incident point P1 to the incident point P2. Therefore, at the time when the first luminous flux L1 is incident on the first diffraction grating 11, the optical path length of the first luminous flux L1 is shortened by ΔM in length.

Further, when the first diffraction grating 11 moves upward along the third direction Z, that is, by the length ΔZ in the direction approaching the head, the position of the first light flux L1 that is incident on the second diffraction grating 312 is changed. It changes from the incident point Q1 to the incident point Q2. The optical path length from the incident point P2 of the first diffraction grating 11 to the incident point Q2 of the second diffraction grating 312 is the first when the first diffraction grating 11 does not move in the third direction Z. The length M1 is longer than the optical path length from the incident point P1 of the diffraction grating 11 to the incident point Q1 of the second diffraction grating 312. Further, the distance from the incident point Q2 of the second diffraction grating 312 to the object mirror 315 is the incident point of the second diffraction grating 312 when the first diffraction grating 11 is not moving in the third direction Z. The length M2 is longer than the optical path length from Q1 to the object mirror 315.

Therefore, if ΔZ = M1 + M2 is satisfied, the optical path length of the first luminous flux L1 becomes constant even if the first diffraction grating 11 moves in the third direction Z. The conditions for satisfying ΔZ = M1 + M2 are the incident angle θ _R to the first diffraction grating 11, the diffraction angle θ of the first diffraction grating 11, the incident angle θ ₁ to the second diffraction grating 312, and the second. The following equation 13 can be shown from the diffraction angle θ ₂ of the diffraction grating 312.
[Equation 13]

Therefore, the diffraction angle theta ₂ of the diffraction angle theta and the second diffraction grating 312 of the first diffraction grating 11 satisfies the above expression 13. As a result, the optical path length of the first luminous flux L1 can be kept constant even if the first diffraction grating 11 moves in the third direction Z. It can also be applied to an optical path in which the first light flux L1 is reflected by the object mirror 315 and returns to the light flux dividing portion 313. Therefore, the optical path length of the return optical path in the first luminous flux L1 can always be constant.

When the incident on the first diffraction grating 11 in the first luminous flux L1 is vertical, θ _R = 0 °. If the second diffraction grating 312 satisfies the Bragg condition, then θ ₁ = θ ₂ = φ. As a result, the above formula 13 is converted into the above formula 5.

Further, the light receiving element of the light receiving unit 7 obtains an interference signal as shown in the following formula 14.
[Equation 14]

K1 is the wave number of the first diffraction grating 11 represented by 2π / d _R. Further, x indicates the amount of movement of the first diffraction grating 11, that is, the amount of displacement of the head 3 and the member 2 to be measured relative to the first direction X. On the other hand, K2 is the wave number of the second diffraction grating 12 represented by 2π / d _T. z indicates the amount of movement of the second diffraction grating 12 in the lattice vector direction in the first luminous flux L1 incident on the second diffraction grating 12. Note that d _R is the lattice pitch of the first diffraction grating 11, and d _T is the lattice pitch of the second diffraction grating 12. Further, δ indicates the initial phase.

Further, B is a coefficient associated with the lattice vector direction of the second diffraction grating 12 being inclined at an inclination angle θ _T with respect to the direction in which the first luminous flux L1 is incident on the first diffraction grating 11. .. The inclination angle θ _T is an angle of incidence θ _R on the first diffraction grating 11, a diffraction angle θ of the first diffraction grating 11, an angle of incidence θ _{1 on} the second diffraction grating 312, and θ _T = θ _1. It has a relationship of + θ + θ _R −90 °.

In this way, even if the first light beam L1 does not enter perpendicularly to the first diffraction grating 11 and the second diffraction grating 312 does not satisfy the Bragg condition, the first diffraction grating 11 if the diffraction angle theta ₂ of the diffraction angle theta and the second diffraction grating 312 satisfies the equation 13, is not the optical path length of the first light flux L1 is changed.

Since other configurations are the same as those of the displacement detection device 1 according to the first embodiment, their description will be omitted. The displacement detection device 301 having such a configuration can also obtain the same effects as the displacement detection device 1 according to the above-described first embodiment.

5. Example of Fifth Embodiment Next, the displacement detection device according to the fifth embodiment will be described with reference to FIG.
FIG. 15 is a schematic configuration diagram showing the configuration of the displacement detection device according to the fifth embodiment.

The displacement detection device 401 according to the fifth embodiment detects the relative displacement of the head 3 or the member 2 to be measured only in the third direction Z. Therefore, here, the same reference numerals are given to the parts common to the displacement detection device 1 according to the first embodiment, and duplicate description will be omitted.

As shown in FIG. 15, the displacement detection device 401 includes a first diffraction grating 11 provided on the member 2 to be measured, a head 403, and a relative position information output means 404.

The head 403 has a displacement detection unit 405, a light source 6, and a light receiving unit 7 provided in the displacement detection unit 405. Further, the displacement detection unit 405 includes a second diffraction grating 12, a luminous flux dividing unit 13, an object mirror 15, and a first phase plate 17. Since the second diffraction grating 12, the object mirror 15, and the first phase plate 17 have the same configuration as the displacement detection device 1 according to the first embodiment, the description thereof will be omitted. To do.

Further, the head 403 includes a luminous flux coupling portion 413, a third diffraction grating 412, a first reference reflection member 414a, a second reference reflection member 414b, a second object mirror 415, and a second object. It has 3 phase plates 417. The first reference reflecting member 414a and the second reference reflecting member 414b are arranged at positions facing each other on both sides of the head 3 in the first direction X. The first reference reflecting member 414a and the second reference reflecting member 414b are composed of a triangular prism. As described above, the reference reflecting member is not limited to the mirror, and various other optical components such as a prism can be applied.

The second luminous flux L2, which is the reference light reflected by the luminous flux dividing portion 13, is irradiated toward the first reference reflecting member 414a. Then, the first reference reflecting member 414a reflects the incident second light flux L2 toward the second reference reflecting member 414b. Then, the second reference reflecting member 414b reflects the incident second luminous flux L2 toward the luminous flux coupling portion 413.

The luminous flux coupling portion 413, the third diffraction grating 412, the mirror 415 for the second object, and the third phase plate 417 are the luminous flux dividing portion 13, the second diffraction grating 12, the mirror 15 for the object, and the first phase plate. It is arranged on one side of the first direction X with respect to 17. Specifically, the luminous flux coupling portion 413, the third diffraction grating 412, the second object mirror 415 and the third phase plate 417 are the luminous flux dividing portion 13, the second diffraction grating 12, the object mirror 15 and It is arranged at a position inverted with respect to the first phase plate 17 along the first direction X.

The first luminous flux L1 that was incident on the first irradiation point PA of the first diffraction grating 11 and was diffracted twice by the first diffraction grating 11 and the second diffraction grating 12 and returned to the luminous flux dividing unit 13 again. Is reflected by the luminous flux dividing portion 13 and is irradiated toward the luminous flux coupling portion 413. The light flux coupling unit 413 reflects the incident first light flux L1 again toward the first diffraction grating 11 of the member 2 to be measured. That is, the luminous flux coupling portion 413 has a role as a rereflection portion.

The first luminous flux L1 that reflects the luminous flux coupling portion 413 passes through the third phase plate 417, and its polarization direction changes to circularly polarized light. Then, the first luminous flux L1 that has passed through the third phase plate 417 is incident on the second irradiation point PB of the first diffraction grating 11. The first luminous flux L1 is diffracted by the first diffraction grating 11. The direction of the diffraction direction at the second irradiation point PB is opposite to the direction of the diffraction direction at the first irradiation point PA in the first direction X. That is, the direction of the diffraction direction at the second irradiation point PB is opposite to the direction of the diffraction direction at the first irradiation point PA.

The first luminous flux L1 diffracted by the first diffraction grating 11 is incident on the third diffraction grating 412. Then, the first luminous flux L1 is diffracted by the third diffraction grating 412 and incident on the second object mirror 415. The first luminous flux L1 is reflected by the second object mirror 415 and is incident on the third diffraction grating 412 again. Then, the first luminous flux L1 is diffracted again by the third diffraction grating 412 and is incident on the first diffraction grating 11.

The lattice pitch and diffraction angle of the third diffraction grating 412 are the same as the lattice pitch d _T and the diffraction angle φ of the second diffraction grating 12. Further, the positional relationship between the third diffraction grating 412 and the second object mirror 415 is obtained by reversing the positional relationship between the second diffraction grating 12 and the object mirror 15 along the first direction X. The positional relationship in the third direction Z is the same. Therefore, these explanations will be omitted.

Then, the first light flux L1 incident on the first diffraction grating 11 is diffracted by the first diffraction grating 11 and irradiated toward the third phase plate 417 and the light flux coupling portion 413. The first luminous flux L1 is diffracted four times only by the first diffraction grating 11, but the direction of the diffraction direction is reversed twice. Therefore, the phase diffracted by the first diffraction grating 11 in the first luminous flux L1 is canceled.

The first luminous flux L1 incident on the luminous flux coupling portion 413 passes through the luminous flux coupling portion 413. Further, the second luminous flux L2 incident on the luminous flux coupling portion 413 reflects the luminous flux coupling portion 413. As a result, the first luminous flux L1 and the second luminous flux L2 overlap at the luminous flux coupling portion 413. Then, the first luminous flux L1 and the second luminous flux L2 overlap each other as s-polarized light and p-polarized light orthogonal to each other, and irradiate the light receiving unit 7.

The optical path lengths from the luminous flux dividing portion 13 to the luminous flux coupling portion 413 in the first luminous flux L1 and the second luminous flux L2 divided by the luminous flux dividing portion 13 are set to be equal.

Since the light receiving unit 7 has the same configuration as the light receiving unit 7 according to the first embodiment, the description thereof will be omitted. In the light receiving unit 7, an interference signal of A × cos (4 × B × K2z + δ) can be obtained. Here, A is the amplitude of interference, and K2 is the wave number of the second diffraction grating 12 represented by 2π / d _T. z indicates the amount of movement of the second diffraction grating 12 in the lattice vector direction in the first luminous flux L1 incident on the second diffraction grating 12. Note that d _R is the lattice pitch of the first diffraction grating 11, and d _T is the lattice pitch of the second diffraction grating 12. Further, δ indicates the initial phase.

Further, B is a coefficient associated with the inclination of the lattice vector direction of the second diffraction grating 12 with respect to the third direction Z at an inclination angle θ _T. Then, when the angle of incidence on the second diffraction grating 12 (the diffraction angle is the same under Bragg conditions) is φ, it can be indicated by B = cosθ _T + sinθ _T × tanφ.

As described above, the interference signal obtained by the light receiving unit 7 includes only the displacement information in the third direction Z. As a result, according to the displacement detection device 401 according to the fifth embodiment, it is possible to detect the relative displacement of the head 3 or the member 2 to be measured only in the third direction Z.

Since other configurations are the same as those of the displacement detection device 1 according to the first embodiment, their description will be omitted. The displacement detection device 401 having such a configuration can also obtain the same effects as the displacement detection device 1 according to the above-described first embodiment.

6. Sixth Embodiment Example Next, the displacement detection device according to the sixth embodiment will be described with reference to FIGS. 16 and 17.
FIG. 16 is a schematic configuration diagram showing the configuration of the displacement detection device according to the sixth embodiment, and FIG. 17 shows the first diffraction grating and the second diffraction grating in the displacement detection device according to the sixth embodiment. It is explanatory drawing which shows the relationship between the incident angle and the diffraction angle of a diffraction grating.

The displacement detection device 501 according to the sixth embodiment differs from the displacement detection device 1 according to the first embodiment in that a reflection type diffraction grating is used as the second diffraction grating. is there. Therefore, here, the same reference numerals are given to the parts common to the displacement detection device 1 according to the first embodiment, and duplicate description will be omitted.

As shown in FIG. 16, the displacement detection device 501 includes a head 503, a member 2 to be measured provided with a first diffraction grating 11, and a relative position information output means 504. The head 503 has a displacement detection unit 505, a light source 6, and a light receiving unit 7 provided on the displacement detection unit 505.

Further, the displacement detection unit 505 includes a second diffraction grating 512, a luminous flux dividing unit 13, a first phase plate 17, a second phase plate 18, and a reference mirror 14. Since the luminous flux dividing portion 13, the reference mirror 14, the first phase plate 17, and the second phase plate 18 have the same configuration as the displacement detection device 1 according to the first embodiment. , The description is omitted.

The second diffraction grating 512 is a reflection type diffraction grating that reflects and diffracts the incident first light flux L1. Then, the second diffraction grating 512 reflects the first luminous flux L1 diffracted by the first diffraction grating 11 again toward the first diffraction grating 11 and diffracts it. Therefore, in the displacement detection device 501 according to the sixth embodiment, the second diffraction grating 512 has a role as a reflection member for an object. As a result, it is not necessary to newly provide a mirror, a prism, or the like as a reflective member for an object, and the number of parts can be reduced.

Next, with reference to FIG. 17, the relationship between the incident angle θ _R and the diffraction angle θ of the first diffraction grating 11 and the incident angle θ ₁ and the diffraction angle θ ₂ to the second diffraction grating 512 will be described.
As shown in FIG. 17, when the first diffraction grating 11 moves upward along the third direction Z, that is, in the direction approaching the head by the length ΔZ, it becomes the first diffraction grating 11 in the first luminous flux L1. The position of incidence changes from the incident point P1 to the incident point P2. Therefore, at the time when the first luminous flux L1 is incident on the first diffraction grating 11, the optical path length of the first luminous flux L1 is shortened by ΔM in length.

Further, when the first diffraction grating 11 moves upward by the length ΔZ along the third direction Z, that is, in the direction approaching the head, the position of the first light flux L1 that is incident on the second diffraction grating 512 is changed. It changes from the incident point Q1 to the incident point Q2. The optical path length from the incident point P2 of the first diffraction grating 11 to the incident point Q2 of the second diffraction grating 512 is the first when the first diffraction grating 11 does not move in the third direction Z. The length M1 is longer than the optical path length from the incident point P1 of the diffraction grating 11 to the incident point Q1 of the second diffraction grating 512.

Therefore, if ΔM = M1 is satisfied, the optical path length of the first luminous flux L1 becomes constant even if the first diffraction grating 11 moves in the third direction Z. The conditions for satisfying ΔZ = M1 are the incident angle θ _R to the first diffraction grating 11, the diffraction angle θ of the first diffraction grating 11, and the incident angle (diffraction angle) θ ₁ to the second diffraction grating 512. Then, it can be expressed by θ = θ _R and θ ₁ + θ = 90 °.

Therefore, the angle of incidence θ _{R on} the diffraction grating 11 of 1, the diffraction angle θ of the first diffraction grating 11, and the angle of incidence (diffraction angle) θ _{1 on} the second diffraction grating 512 are θ = θ _R , and Satisfy θ ₁ + θ = 90 °. As a result, the optical path length of the first luminous flux L1 can be kept constant even if the first diffraction grating 11 moves in the third direction Z.

Since other configurations are the same as those of the displacement detection device 1 according to the first embodiment, their description will be omitted. The displacement detection device 501 having such a configuration can also obtain the same effects as the displacement detection device 1 according to the above-described first embodiment.

7. Seventh Embodiment Example Next, the displacement detection device according to the seventh embodiment will be described with reference to FIGS. 18 and 19.
FIG. 18 is a schematic configuration diagram showing the configuration of the displacement detection device according to the seventh embodiment, and FIG. 19 shows the first diffraction grating and the second diffraction grating in the displacement detection device according to the seventh embodiment. It is explanatory drawing which shows the relationship between the incident angle and the diffraction angle of a diffraction grating.

The displacement detection device 601 according to the seventh embodiment uses a reflection type diffraction grating as the second diffraction grating, similarly to the displacement detection device 501 according to the sixth embodiment. .. Therefore, here, the same reference numerals are given to the parts common to the displacement detection device 1 according to the first embodiment, and duplicate description will be omitted.

As shown in FIG. 18, the displacement detection device 601 includes a head 603, a member 2 to be measured provided with a first diffraction grating 11, and a relative position information output means 4. The head 603 has a displacement detection unit 605, a light source 6, and a light receiving unit 7 provided in the displacement detection unit 605.

Further, the displacement detection unit 505 includes a second diffraction grating 612, a luminous flux dividing unit 13, a first phase plate 17, a second phase plate 18, a reference mirror 14, and an object mirror 615. have. Since the luminous flux dividing portion 13, the reference mirror 14, the first phase plate 17, and the second phase plate 18 have the same configuration as the displacement detection device 1 according to the first embodiment. , The description is omitted.

The second diffraction grating 612 is a reflection type diffraction grating that reflects and diffracts the incident first light flux L1. Then, the second diffraction grating 612 reflects the first luminous flux L1 diffracted by the first diffraction grating 11 toward the object mirror 615 and diffracts it. The object mirror 615 reflects the incident first luminous flux L1 again toward the second diffraction grating 612.

In the displacement detection device 601 according to the seventh embodiment, the object mirror 615 is added to the displacement detection device 501 according to the sixth embodiment. However, by providing the object mirror 615, the work of matching the optical path length of the first light flux L1 and the optical path length of the second light flux L2 can be easily performed.

Next, with reference to FIG. 19, the relationship between the incident angle θ _R and the diffraction angle θ of the first diffraction grating 11 and the incident angle θ ₁ and the diffraction angle θ ₂ to the second diffraction grating 12 will be described.
As shown in FIG. 19, when the first diffraction grating 11 moves upward along the third direction Z, that is, in the direction approaching the head by the length ΔZ, it becomes the first diffraction grating 11 in the first luminous flux L1. The position of incidence changes from the incident point P1 to the incident point P2. Therefore, at the time when the first luminous flux L1 is incident on the first diffraction grating 11, the optical path length of the first luminous flux L1 is shortened by ΔM in length.

Further, when the first diffraction grating 11 moves upward along the third direction Z, that is, by the length ΔZ in the direction approaching the head, the position of the first light flux L1 that is incident on the second diffraction grating 612 is changed. It changes from the incident point Q1 to the incident point Q2. The optical path length from the incident point P2 of the first diffraction grating 11 to the incident point Q2 of the second diffraction grating 612 is the first when the first diffraction grating 11 does not move in the third direction Z. The length M1 is longer than the optical path length from the incident point P1 of the diffraction grating 11 to the incident point Q1 of the second diffraction grating 612. Further, the distance from the incident point Q2 of the second diffraction grating 612 to the object mirror 615 is the incident point of the second diffraction grating 612 when the first diffraction grating 11 is not moving in the third direction Z. The length M2 is longer than the optical path length from Q1 to the object mirror 615.

Therefore, if ΔZ = M1 + M2 is satisfied, the optical path length of the first luminous flux L1 becomes constant even if the first diffraction grating 11 moves in the third direction Z. The conditions for satisfying ΔZ = M1 + M2 are the incident angle θ _R to the first diffraction grating 11, the diffraction angle θ of the first diffraction grating 11, the incident angle θ ₁ to the second diffraction grating 612, and the second. The above equation 13 can be shown from the diffraction angle θ ₂ of the diffraction grating 612.

Therefore, the diffraction angle theta ₂ of the diffraction angle theta and the second diffraction grating 612 of the first diffraction grating 11 satisfies the above expression 13. As a result, the optical path length of the first luminous flux L1 can be kept constant even if the first diffraction grating 11 moves in the third direction Z.

As the second diffraction grating 512 according to the sixth embodiment and the second diffraction grating 612 according to the seventh embodiment, for example, the cross-sectional shape of the groove is formed in a sawtooth shape, so-called. It is preferable to use a blazed diffraction grating. This makes it possible to increase the diffraction efficiency for a specific wavelength.

Since other configurations are the same as those of the displacement detection device 1 according to the first embodiment, their description will be omitted. The displacement detection device 601 having such a configuration can also obtain the same operation and effect as the displacement detection device 1 according to the above-described first embodiment.

The present invention is not limited to the embodiments described above and shown in the drawings, and various modifications can be made without departing from the gist of the invention described in the claims. In the above-described embodiment, the light emitted from the light source may be supplied by flying not only in a gas but also in a space in a liquid or a vacuum.

Although words such as "parallel" and "orthogonal" have been used in the present specification, these do not mean only strict "parallel" and "orthogonal", but include "parallel" and "orthogonal". Further, it may be in a "substantially parallel" or "substantially orthogonal" state within a range in which the function can be exhibited.

1 ... Displacement detection device, 2 ... Measured member, 2a ... Measured surface, 3 ... Head, 4 ... Relative position information output means, 5 ... Displacement detection unit, 6 ... Light source, 7 ... Light receiving part, 11 ... First Diffraction grating, 12 ... 2nd diffraction grating, 13 ... Light source dividing part (light flux coupling part), 14 ... Reference mirror (reference reflection member), 15 ... Object mirror (object reflection member), 17 ... 1st Phase plate 18 ... 2nd phase plate, L1 ... 1st light beam, L2 ... 2nd light beam

Claims (8)

A first diffraction grating provided on the surface to be measured of the member to be measured, and
A head, which is arranged to face the surface of the member to be measured, is provided.
The head and the member to be measured are relatively movable in at least one of a direction parallel to the surface to be measured and a direction orthogonal to the surface to be measured.
The head
A light source that irradiates light and
A displacement detection unit that divides the light emitted from the light source into a first luminous flux and a second luminous flux and irradiates the first luminous flux toward the first diffraction grating.
A light receiving unit that receives the second light flux and the first light flux returned from the first diffraction grating via the displacement detection unit is provided.
The displacement detection unit
A luminous flux dividing portion that divides the light into the first luminous flux and the second luminous flux and irradiates the divided first luminous flux toward the first diffraction grating.
A second diffraction grating that is divided by the light flux dividing portion and diffracted by the first diffraction grating, diffracts the first light flux, and irradiates the first diffraction grating again with the first light flux.
A reference reflecting member that reflects the second luminous flux divided by the luminous flux dividing portion,
A luminous flux coupling that superimposes the first light flux diffracted by the first diffraction grating and the second diffraction grating and the second light flux reflected by the reference reflecting member to irradiate the light receiving portion. With a department,
The angle of incidence of the first light beam on the first diffraction grating, the diffraction angle of the first diffraction grating, the angle of incidence of the first light beam on the second diffraction grating, the second diffraction grating. The diffraction angle of is incident on the first diffraction grating from the light beam dividing portion in the first light beam when at least one of the head and the member to be measured is displaced in a direction orthogonal to the surface to be measured. A displacement detecting apparatus characterized in that the amount of displacement of the optical path length up to is equal to the amount of displacement of the optical path length from the first diffraction grating to the incident on the second diffraction grating in the first light beam. The displacement detecting unit includes an optical path length from the luminous flux dividing portion in the first luminous flux to the luminous flux coupling portion via the first diffraction grating, and the luminous flux dividing portion in the second luminous flux for reference. The displacement detecting device according to claim 1, wherein the optical path lengths to the luminous flux coupling portion via the reflecting member are equal. The incident angle θ _R of the first light beam to the first diffraction grating, the diffraction angle θ of the first diffraction grating, the incident angle θ ₁ of the first light beam to the second diffraction grating, the said. The diffraction angle θ ₂ of the second diffraction grating satisfies the following equation [Equation].

The displacement detection device according to claim 1 or 2. The displacement according to any one of claims 1 to 3, wherein the displacement detecting unit causes the first light flux divided by the light flux dividing unit to be vertically incident on the first diffraction grating. Detection device. The displacement detection device according to any one of claims 1 to 4, wherein the diffraction of the second diffraction grating satisfies the Bragg condition. The head
A first displacement detection unit composed of the displacement detection unit and arranged on one side of the first diffraction grating in the lattice vector direction,
A second displacement detection unit arranged on the other side of the first diffraction grating in the lattice vector direction with respect to the first displacement detection unit and having the same components as the first displacement detection unit.
A light distribution unit that distributes the light emitted from the light source to the light that irradiates the first displacement detection unit and the light that irradiates the second displacement detection unit is provided.
The claim is characterized in that the component of the second displacement detection unit is inverted with respect to the component of the first displacement detection unit along the lattice vector direction of the first diffraction grating. The displacement detection device according to any one of 1 to 5. The first diffraction grating is in the direction of the first lattice vector parallel to the surface to be measured.
It has a second lattice vector direction that is parallel to the surface to be measured and intersects the first lattice vector direction.
The head
A first displacement detection unit composed of the displacement detection unit and arranged on one side of the first diffraction grating in the direction of the first lattice vector,
A second displacement detection unit arranged on the other side of the first diffraction grating in the direction of the first lattice vector with respect to the first displacement detection unit and having the same components as the first displacement detection unit.
A third displacement detection unit arranged on one side of the first diffraction grating in the direction of the second lattice vector and having the same components as the first displacement detection unit.
A fourth displacement detection unit, which is arranged on the opposite side of the first diffraction grating in the direction of the second lattice vector with respect to the third displacement detection unit and has the same components as the first displacement detection unit.
The light emitted from the light source is irradiated to the first displacement detection unit, the light to irradiate the second displacement detection unit, the light to irradiate the third displacement detection unit, and the fourth displacement detection unit. Equipped with a distributor for the light
The component of the second displacement detection unit is arranged in reverse with respect to the component of the first displacement detection unit along the first lattice vector direction of the first diffraction grating, and the third displacement detection is performed. The components of the unit are arranged along the second grating vector direction.
The component of the fourth displacement detection unit is inverted with respect to the component of the third displacement detection unit along the second lattice vector direction of the first diffraction grating. The displacement detection device according to any one of claims 1 to 5. The displacement detection unit
The first diffraction grating is irradiated again by the second diffraction grating, and the first light beam diffracted by the first diffraction grating and returned is irradiated again toward the first diffraction grating. With the rereflection part,
The first diffraction grating is irradiated by the rereflection unit, the first light beam diffracted by the first diffraction grating is diffracted, and the first light beam is again irradiated to the first diffraction grating. With a third diffraction grating,
Any one of claims 1 to 5, wherein the third diffraction grating is inverted with respect to the second diffraction grating along the lattice vector direction of the first diffraction grating. Displacement detection device according to the section.

Images