Measurement device and measurement method

Abstract

A measurement device according to the present embodiment comprises: a laser light emission unit which emits first laser light and second laser light; a transmission-type diffraction grating on which the first laser light emitted from the laser light emission unit is incident; a scale diffraction grating on which ±1st order diffraction light emitted from the transmission-type diffraction grating is incident; a reflection element on which 0 order diffraction light emitted from the transmission-type diffraction grating is incident; a reference light emission unit on which the second laser light emitted from the laser light emission unit is incident, and which emits a reference light; an interference optical system which generates a first interference beam by superimposing third laser light that returns in an optical path overlapping the ±1st order diffraction light from the scale diffraction grating and a portion of fourth laser light that returns in an optical path overlapping the 0 order diffraction light from the reflection element, and which generates a second interference beam by superimposing another portion of the fourth laser light emitted from the reflection element and the reference light emitted from the reference light emission unit; a light-receiving unit which receives the first interference beam to generate a first interference signal and receives the second interference beam to generate a second interference signal; and a displacement calculation unit which calculates a displacement amount of the scale diffraction grating from the first interference signal and the second interference signal.

Description

Measuring device and measuring method

[0001] The present invention relates to a measurement device and a measurement method.

[0002] Precision positioning is a fundamental technology used in manufacturing, for example. Displacement sensors that perform single-axis measurement using laser interferometers and linear encoders have been developed as precision positioning technologies. However, there is an increasing need for multi-axis measurement in various measuring instruments such as machine tools and surface roughness meters.

[0003] Conventional multi-axis measuring instruments use sensors in multiple mutually orthogonal directions, but misplacement of the sensors can cause Abbe errors, and the accumulation of these errors can lead to a decrease in measurement accuracy. To maintain the accuracy of laser interferometers, environmental conditions such as temperature, humidity, and air pressure must be strictly controlled.

[0004] Meanwhile, optical surface encoders have been developed. In optical surface encoders, a scale diffraction grating with an equal pitch is mounted as a measurement target on a movable stage or the like, and relative displacement in multiple axes is measured by reading information about the scale diffraction grating with an optical head. For example, Non-Patent Documents 1, 2, and 3 disclose surface encoders having a reference grating in which a reference grating is arranged perpendicular to the scale grating (scale diffraction grating), laser light is incident on the scale grating and the reference grating, and diffracted light from the scale grating and diffracted light from the reference grating are superimposed and interfere with each other. Furthermore, Patent Document 1 discloses a surface encoder without a reference grating, in which diffracted light from the scale gratings interfere with each other.

[0005] Japanese Patent Application Laid-Open No. 2023-097776

[0006] Gao Wei, "Latest Encoder Technology and Prospects," Journal of the Japan Society for Precision Engineering, Vol. 82, No. 9, pp. 773-777 (2016). A. Kimura et al., "A sub-nanometric three-axis surface encoder with short-period planar gratings for stage motion measurement," Precision Engineering, Vol. 36, pp. 576-585 (2012). Y. Hong et al. , “Reduction of crosstalk errors in a surface encoder having a long Z-directional measuring range”, Sensors, Vol. 22, No. 23,9563 (2022).

[0007] However, in conventional surface encoders, laser light is incident perpendicularly on the scale grating and diffracted light diffracted from the grating surface at a diffraction angle corresponding to the order is detected. Therefore, when the scale grating moves in a direction perpendicular to the grating surface, the position of the diffracted light from the scale grating shifts on the detector, causing a beam shift. For this reason, the allowable range of movement of the scale grating in the direction perpendicular to the grating surface, which is necessary to obtain an interference signal, is very small. In other words, the measurement range of the scale grating in the direction perpendicular to the grating surface is limited.

[0008] For example, in the technology disclosed in Non-Patent Document 3, a symmetrical optical arrangement cancels out the effect of beam shift, thereby expanding the measurement range of the surface encoder in the Z axis, i.e., the allowable range of movement of the scale grating in the direction perpendicular to the grating surface. However, there is a demand for a further expansion of the measurement range of the surface encoder in the direction perpendicular to the grating surface. Furthermore, in the technology disclosed in Non-Patent Document 3, a symmetrical optical arrangement is used, so the number of parts constituting the device is large, and the optical system and the entire device are large in scale.

[0009] In view of the above-mentioned problems, the present invention provides a measurement device and a measurement method that can detect multi-axial displacement of a scale grating over a wide measurement range without causing beam shift on the light-receiving surface of a detector even when the scale grating moves in a direction perpendicular to the grating surface, i.e., in the normal direction.

[0010] A measuring device according to an embodiment of the present invention includes a laser beam emitting unit that emits a first laser beam and a second laser beam, a transmission diffraction grating onto which the first laser beam emitted from the laser beam emitting unit is incident, a scale diffraction grating onto which ±1st-order diffracted beams emitted from the transmission diffraction grating are incident, a reflecting element onto which 0th-order diffracted beams emitted from the transmission diffraction grating are incident, a reference beam emitting unit that receives the second laser beam emitted from the laser beam emitting unit and emits a reference beam, and a third laser beam returning from the scale diffraction grating along an optical path that overlaps with the ±1st-order diffracted beams. an interference optical system that generates a first interference beam by superimposing light and a portion of a fourth laser beam returning from the reflecting element along an optical path that overlaps with the zeroth-order diffracted light, and generates a second interference beam by superimposing another portion of the fourth laser beam emitted from the reflecting element and the reference light emitted from the reference light emission unit; a light receiving unit that receives the first interference beam to generate a first interference signal, and receives the second interference beam to generate a second interference signal; and a displacement calculation unit that calculates the amount of displacement of the scale diffraction grating from the first interference signal and the second interference signal.

[0011] According to the present invention, it is possible to provide a measurement device and a measurement method that can detect multi-axial displacement of a scale grating over a wide measurement range without causing beam shift on the light receiving surface of the detector even when the scale grating moves in a direction perpendicular to the grating surface, i.e., in the normal direction.

[0012] Fig. 1 is a schematic diagram of a measurement device of a first embodiment to which the present invention is applied; Fig. 2 is a front view of a transmission diffraction grating of the measurement device of Fig. 1; Fig. 3 is a front view of a scale diffraction grating of the measurement device of Fig. 1; Fig. 4 is a schematic diagram of a measurement device of a second embodiment to which the present invention is applied; Fig. 5 is a schematic diagram of a measurement device of a third embodiment to which the present invention is applied;

[0013] Hereinafter, embodiments of a measuring apparatus and a measuring method according to the present invention will be described with reference to the drawings, in which the direction of movement of a scale grating perpendicular to the grating surface is defined as the Z-axis direction, the X-axis direction of the scale grating is defined as the up-down direction, and the Y-axis direction of the scale grating is defined as the depth direction.

[0014] First Embodiment First, a first embodiment of the present invention will be described with reference to Fig. 1 to Fig. 3. Fig. 1 is a schematic diagram of a measurement apparatus 100 according to the first embodiment of the present invention. The measurement apparatus 100 includes a laser beam emitting unit 110, a transmission type diffraction grating 120, a wave plate 124, a scale diffraction grating 130, an interference optical system 180, a reference beam emitting unit 140, a light receiving unit 190, and a displacement calculating unit 200. For simplicity, diffracted light and the like that are not required for the present invention are not shown in the drawings.

[0015] The laser light emitting unit 110 includes a laser light source 111 , a collimating lens 112 , and a cube-type polarizing beam splitter 113 .

[0016] The laser light source 111 emits laser light L11 containing S-polarized light and P-polarized light along the X-axis direction. The laser light L11 emitted from the laser light source 111 diverges from the emission surface of the laser light source 111 around the X-axis direction. The collimating lens 112 is disposed on the optical path of the laser light L11 emitted from the laser light source 111. The collimating lens 112 collimates the laser light L11 incident along the X-axis direction and emits the collimated laser light L11 along the X-axis. Note that each drawing only shows the traveling direction and optical axis of each laser light after the collimating lens 112 in the measurement device 100, and the outer edges of each laser beam are omitted.

[0017] The polarizing beam splitter 113 is disposed on the optical path of the laser beam L11 that has been output from the collimating lens 112 and collimated. The polarizing beam splitter 113 has, for example, a polarization separation film that reflects S-polarized light contained in the incident light and transmits P-polarized light contained in the incident light. The polarizing beam splitter 113 refracts S-polarized laser beam L12S of the laser beam L11 incident along the X-axis direction in a Z-axis direction that is perpendicular to the X-axis direction, and emits the laser beam L12S in the Z-axis direction, while emitting P-polarized laser beam L13P of the laser beam L11 incident along the X-axis direction in the X-axis direction. Note that the polarizing beam splitter 113 may be used to convert the laser beam emitted in the Z-axis direction into P-polarized light and the laser beam emitted in the X-axis direction into S-polarized light.

[0018] The transmission diffraction grating 120 is disposed on the optical path of the laser beam L12S emitted from the polarizing beam splitter 113 of the laser beam emitting unit 110. Although not shown in Fig. 1, the grating surface of the transmission diffraction grating 120 is aligned along the X-axis direction, which is perpendicular to the laser beam L12S. That is, as shown in Fig. 2, a diffraction grating is formed with a period (pitch) of 2g on the surface of the transmission diffraction grating 120 that faces the polarizing beam splitter 113 and is parallel to the X-axis direction.

[0019] The transmissive diffraction grating 120 separates the laser beam L12S incident along the Z-axis direction into laser beam L14S, which is a zeroth-order diffracted beam that travels straight in at least the Z-axis direction, and laser beam L15S, which is a ±1st-order diffracted beam that is inclined at a predetermined angle toward the X-axis and Z-axis directions and travels in the D1 or D3 direction on a plane including the X-axis and Z-axis directions. Note that, for simplicity, the −1st-order diffracted beam in the D3 direction is not shown in FIG. 1.

[0020] In order to prevent the measurement device 100 from generating stray light or other light unnecessary for measurement, a light-shielding plate or a light-absorbing plate may be disposed on the optical path of the −1st-order diffracted light (not shown) of the laser light L12S.

[0021] The scale diffraction grating 130 is disposed in an area irradiated with the laser beams L14S and L15S emitted from the transmission diffraction grating 120. The scale diffraction grating 130 is, for example, a reflection diffraction grating. The grating surface of the scale diffraction grating 130 is along the X-axis direction. Although not shown in FIG. 1 , a diffraction grating is formed on the surface of the scale diffraction grating 130, i.e., the surface facing the transmission diffraction grating 120. The period (pitch) of the scale diffraction grating 130 is set to g, which is half the period (pitch) of the transmission diffraction grating 120. The scale diffraction grating 130 is supported by a moving stage 132 and is movable along the X-axis, Y-axis, and Z-axis directions.

[0022] The laser light L14S emitted from the transmission diffraction grating 120 is incident on the scale diffraction grating 130 via the wave plate 124. The scale diffraction grating 130 then emits the incident laser light L14C as laser light L16C, which is zeroth-order diffracted light, in the MZ direction, which is parallel to the Z-axis direction and opposite to the Z-axis direction. That is, at least a portion of the laser light L14C incident on the scale diffraction grating 130 from the transmission diffraction grating 120 returns as laser light L16C from the scale diffraction grating 130 to the transmission diffraction grating 120 in the opposite direction along substantially the same optical path as when it was incident on the scale diffraction grating 130.

[0023] The laser beam L16C passes through the wave plate 124 again and enters the transmission diffraction grating 120 as laser beam L16P.

[0024] The wave plate 124 is disposed between the transmissive diffraction grating 120 and the scale diffraction grating 130 on the optical path of the laser light L14 emitted from the transmissive diffraction grating 120. The wave plate 124 is, for example, a quarter-wave plate, and rotates the polarization direction of light incident from the Z-axis direction and the MZ direction by a quarter wavelength, and emits the light in the Z-axis direction and the MZ direction. The wave plate 124 converts the S-polarized laser light L14 incident along the Z-axis direction into circularly polarized laser light L14C, and emits the laser light L14C in the Z-axis direction.

[0025] The scale diffraction grating 130 outputs the laser beam L14C incident along the Z-axis direction as circularly polarized laser beam L16C, which is a zero-order diffracted beam, in the MZ direction parallel to and opposite to the Z-axis direction.

[0026] The wave plate 124 converts the circularly polarized laser light L16C incident along the MZ direction into P-polarized laser light L16P, and emits the laser light L16P in the Z-axis direction.

[0027] The scale diffraction grating 130 emits the laser light L15S incident from the transmission diffraction grating 120 along the direction D1 as laser light L20S, which is +1st-order diffracted light, in a direction D2 that is parallel to the direction D1 and opposite to the direction D1. That is, at least a part of the laser light L15S incident on the scale diffraction grating 130 from the transmission diffraction grating 120 returns to the transmission diffraction grating 120 as laser light L20S from the scale diffraction grating 130 in the opposite direction along substantially the same optical path as when it was incident on the scale diffraction grating 130.

[0028] In the measuring apparatus 100 of the present invention, the period of the scale diffraction grating 130 is set to half the period of the transmission diffraction grating 120. Because the period of the scale diffraction grating 130 is half the period of the transmission diffraction grating 120, laser light L20S, which is +1st order diffracted light, is used as the laser light that returns from the scale diffraction grating 130 to the transmission diffraction grating 120 along a path that overlaps with laser light L15S. In the measuring apparatus 100, when attention is focused only on the relative positional relationship between the laser light L15S and the laser light L20S, an arrangement similar to the Littrow mounting is adopted.

[0029] The transmissive diffraction grating 120 separates the laser beam L16P incident along the MZ direction into laser beam L19P, which is ±1st-order diffracted light traveling at least in the D2 direction or the D4 direction, and laser beam L18P, which is 0th-order diffracted light traveling in the MZ direction. For simplicity, the −1st-order diffracted light traveling in the D4 direction is not shown in FIG. 1. The transmissive diffraction grating 120 separates the laser beam L20S incident along the D2 direction into laser beam L21S, which is 0th-order diffracted light traveling at least in the D2 direction, and laser beam L21S traveling in the MZ direction, which is parallel to the Z-axis direction and opposite to the Z-axis direction.

[0030] The interference optical system 180 has a reflecting mirror 134 and a wave plate 150. The transmission type diffraction grating 120 also plays the role of the interference optical system 180. The reflecting mirror 134 of the interference optical system 180 is arranged on the optical path of the laser beams L19P and L21S emitted from the transmission type diffraction grating 120 in the D2 direction. The reflecting mirror 134 reflects the laser beams L19P and L21S incident along the D2 direction and emits the laser beams L19P and L21S in the MZ direction. The laser beams L19P and L21S emitted from the reflection mirror 134 in the same MZ direction are superimposed to generate an interference beam IB1.

[0031] The reference beam emitting unit 140 includes a wave plate 142, a reflecting mirror 144, and a wave plate 150. The wave plate 142 is disposed on the optical path of the laser beam L13P emitted from the polarizing beam splitter 113 of the laser beam emitting unit 110. The wave plate 142 is, for example, a quarter-wave plate, and rotates the polarization direction of light incident from the X-axis direction and the MX direction, which is parallel to the X-axis direction and opposite to the X-axis direction, by a quarter wavelength, and emits the light in the X-axis direction and the MX direction. The wave plate 142 converts the P-polarized laser beam L13P incident along the X-axis direction into circularly polarized laser beam L13C and emits the laser beam L13C in the X-axis direction.

[0032] The reflecting mirror 144 is disposed on the optical path of the laser light L13C emitted in the X-axis direction from the wave plate 142. The reflecting mirror 144 reflects the laser light L13C incident along the X-axis direction, and outputs the reflected light as laser light L30C in the MX direction.

[0033] The wave plate 142 converts the circularly polarized laser beam L30C incident along the MX direction into S-polarized laser beam L30S and emits the laser beam L30S in the MX direction. The laser beam L30S emitted from the wave plate 142 in the MX direction is incident on the polarizing beam splitter 113, refracted by the polarizing beam splitter 113 in the MZ direction, and emitted from the polarizing beam splitter 113 in the MZ direction.

[0034] Laser beam L18P, which is zero-order diffracted light emitted from transmission diffraction grating 120 along the MZ direction, passes through polarizing beam splitter 113 and is emitted in the MZ direction from polarizing beam splitter 113. Laser beams L18P and L30S, which are emitted from polarizing beam splitter 113 in the same MZ direction, are superimposed to generate interference beam IB2.

[0035] The wave plate 150 is arranged across the optical paths of the laser beams L19P and L21S that are output from the reflecting mirror 134 and superimposed on each other in the interference optical system 180, and the optical paths of the laser beams L18P and L30S that are output from the polarizing beam splitter 113 and superimposed on each other. Note that the wave plate 150 may be arranged as separate wave plates on the optical paths of the laser beams L19P and L21S and on the optical paths of the laser beams L18P and L30S. The wave plate 150 adjusts the polarization direction of each of the laser beams L19P and L21S that are incident along the MZ direction, and also adjusts the polarization direction of each of the laser beams L18P and L30S that are incident along the MZ direction. The wave plate 150 is, for example, a quarter wave plate, and converts the incident laser beams L19P, L21S and laser beams L18P, L30S into circularly polarized light, and emits them in the MZ direction as laser beams L19C, L21C and laser beams L18C, L30C.

[0036] The light receiving unit 190 has a first light receiving unit 160 and a second light receiving unit 170. The first light receiving unit 160 is disposed on the optical path of the laser beams L19C and L21C (i.e., the interference beam IB1) ​​emitted from the wave plate 150. The first light receiving unit 160 receives the laser beams L19C and L21C incident along the MZ direction, generates an interference signal S1 of the laser beams L19C and L21C, and outputs the interference signal S1. The second light receiving unit 170 is disposed on the optical path of the laser beams L18C and L30C (i.e., the interference beam IB2) emitted from the wave plate 150. The second light receiving unit 170 receives the laser beams L18C and L30C incident along the MZ direction, generates an interference signal S2 of the laser beams L18C and L30C, and outputs the interference signal S2. Each of the first light receiving section 160 and the second light receiving section 170 is configured with, for example, a photodiode (PD), a position sensing device (PSD), an imaging element, or the like.

[0037] The displacement calculation section 200 is electrically connected to each of the first light receiving section 160 and the second light receiving section 170. The phase Δφ of the laser light L21C, which is the +1st order diffracted light, ＋１ is expressed by the following equation (1).

[0038]

[0039] The symbol g represents half the pitch of the transmission diffraction grating 120. The angle θ represents the diffraction angle of the laser beam L15S, which is the +1st-order diffracted beam emitted from the transmission diffraction grating 120. The symbol Δz represents the displacement of the scale diffraction grating 130 relative to the transmission diffraction grating 120 in the Z-axis direction. The symbol Δx represents the displacement of the scale diffraction grating 130 relative to the transmission diffraction grating 120 in the X-axis direction. The symbol λ represents the peak wavelength of the laser beams L11 and L12S.

[0040] The phase Δφ of the laser beam L19P, which is the zeroth-order diffracted beam ０ is expressed by the following equation (2).

[0041]

[0042] The angle θ is expressed by the following equation (3).

[0043]

[0044] The light intensity I of the interference signal S2 between the laser beam L18P, which is the zero-order diffracted light, and the laser beam L30C, which is the reference light, is （０，ｒｅｆ） is expressed by the following equation (4).

[0045]

[0046] In the formulas in this specification, E represents the electric field of the subscript laser light. * means complex conjugate. A represents the complex amplitude of the subscript laser light. φ represents the phase of the subscript laser light. The subscript 0 represents the zeroth-order diffracted light, and the subscript +1 represents the +1st-order diffracted light. The subscript ref means reference light, and the subscript (0, ref) represents both the reference light and the zeroth-order diffracted light. As described above, the light intensity of the interference signal S2 is expressed as a function of Δz, and the displacement Δz is detected from the above equations (2) to (4).

[0047] The light intensity I of the interference signal S1 between the laser beam L19P, which is the 0th-order diffracted light, and the laser beam L21S, which is the +1st-order diffracted light, is （０，＋１） is expressed by the following equation (5).

[0048]

[0049] As described above, the light intensity of the interference signal S1 is expressed as a function of the displacement Δx and the displacement Δz, and if the displacement Δz is detected from the interference signal S2, the displacement Δx is detected from the interference signal S1.

[0050] The displacement calculation unit 200 receives the interference signal S2 output from the second light receiving unit 170, and applies the interference signal S2 to equation (4) including the above-mentioned displacement amount Δz to detect the displacement amount Δz alone. The displacement calculation unit 200 further receives the interference signal S1 output from the first light receiving unit 160, and applies the interference signal S1 to equation (5) including the above-mentioned displacement amounts Δx and Δz to detect the displacement amount Δx using the already detected displacement amount Δz. The displacement calculation unit 200 is, for example, a computer and has a processor that performs calculations related to equations (1) to (5) above and calculates the displacement amounts Δx and Δz.

[0051] In the measurement apparatus 100, the optical path of the laser light L20S returning from the scale diffraction grating 130 to the transmission diffraction grating 120 overlaps with and is opposite to the optical path of the laser light L15S emitted from the transmission diffraction grating 120 to the scale diffraction grating 130. Therefore, the displacement amounts Δx and Δz are determined only by the size of the scale diffraction grating 130 in the X-axis direction. By adopting a configuration in which the laser light L20S returns from the scale diffraction grating 130 to the transmission diffraction grating 120 as described above, the measurement range of the measurement apparatus 100 in the X-axis direction and the Z-axis direction can be expanded.

[0052] 2 is a front view of the transmission diffraction grating 120 as viewed along the Z-axis direction. As shown in Fig. 2, the transmission diffraction grating 120 is an element in which a one-dimensional diffraction grating having a period 2g in the X-axis direction is formed on the plate surface of a transparent substrate. The slit lines of the one-dimensional diffraction grating of the transmission diffraction grating 120 extend parallel to the Y-axis direction. The laser light L12S incident on the transmission diffraction grating 120 is incident on a region including the one-dimensional diffraction grating for a plurality of periods of the transmission diffraction grating 120.

[0053] Fig. 3 is a front view of the scale diffraction grating 130 as viewed along the Z-axis direction. As shown in Fig. 3, the scale diffraction grating 130 is an element in which a metal coating is applied to the plate surface of a transparent substrate and a one-dimensional diffraction grating having a period g in the X-axis direction is formed. The slit lines of the one-dimensional diffraction grating of the scale diffraction grating 130 extend parallel to the Y-axis direction. Each of the laser beams L14C and L15S incident on the scale diffraction grating 130 is incident on an area including a one-dimensional diffraction grating corresponding to a plurality of periods of the scale diffraction grating 130. The laser beam L15S is incident on the grating surface of the scale diffraction grating 130 further forward in the MX direction than the laser beam L14C.

[0054] The one-dimensional diffraction gratings of the transmission diffraction grating 120 and the scale diffraction grating 130 may be either amplitude type diffraction gratings or phase type diffraction gratings. In order to obtain the intensity of the diffracted light emitted from the transmission diffraction grating 120 and the scale diffraction grating 130, it is preferable that each one-dimensional diffraction grating is a phase type diffraction grating. The one-dimensional diffraction gratings of the transmission diffraction grating 120 and the scale diffraction grating 130 are formed by a known method for manufacturing diffraction gratings.

[0055] The measuring apparatus 100 of the first embodiment described above includes a laser beam emitting unit 110, a transmission diffraction grating 120, a scale diffraction grating (scale diffraction grating, reflective element) 130, an interference optical system 180, a light receiving unit 190, and a displacement calculating unit 200. The laser beam emitting unit 110 emits a laser beam (first laser beam) L12S and a laser beam (second laser beam) L13P in different directions using a polarizing beam splitter 113. The laser beam L12S emitted from the laser beam emitting unit 110 is incident on the transmission diffraction grating 120. The transmission diffraction grating 120 diffracts the incident laser beam L12S and emits laser beam L14S, which is at least a zeroth-order diffracted beam of the laser beam L12S, and laser beam L15S, which is a +1st-order diffracted beam. The scale diffraction grating 130 is incident on the laser beam (+1st order diffracted beam) L15S emitted from the transmission diffraction grating 120 and the laser beam (0th order diffracted beam) L14C obtained after the laser beam (0th order diffracted beam) L14S passes through the wave plate 124. The scale diffraction grating 130 diffracts the incident laser beam L14C and emits laser beam L16C which is at least the 0th order diffracted beam of the laser beam L14C. The scale diffraction grating 130 diffracts the incident laser beam L15S and emits laser beam L20S which is at least the diffracted beam of the laser beam L15S. The laser beam L13P emitted from the laser beam emitting unit 110 is incident on the reference beam emitting unit 140. The reference beam emitting unit 140 emits laser beam (reference beam) L30S based on the incident laser beam L13P. The interference optical system 180 generates an interference beam (first interference beam) IB1 by superimposing the laser beams (third laser beams) L20S, L21S returning from the scale diffraction grating 130 to the transmission type diffraction grating 120 along an optical path overlapping with the laser beam L15S, and a laser beam (part of the fourth laser beam) L19P that is a part of the laser beams (fourth laser beams) L16C, L16P returning from the scale diffraction grating 130 to the transmission type diffraction grating 120 along an optical path overlapping with the zeroth-order diffracted beam. The interference optical system 180 generates an interference beam (second interference beam) IB2 by superimposing, at the polarizing beam splitter 113, another part of the laser beams (fourth laser beams) L16C, L16P emitted from the scale diffraction grating 130 (another part of the fourth laser beam).The light receiving unit 190 receives the interference beam IB1 to generate an interference signal (first interference signal) S1, and receives the interference beam (second interference beam) IB2 to generate an interference signal (second interference signal) S2. The displacement calculation unit 200 calculates a displacement amount Δx in the X-axis direction and a displacement amount Δz in the Z-axis direction of the scale diffraction grating 130 from the interference signals S1 and S2.

[0056] In the measurement apparatus 100 of the first embodiment, the optical paths of the laser beams L16C, L16P and laser beam L20S emitted from the scale diffraction grating 130 toward the transmission diffraction grating 120 substantially overlap with the optical paths of the laser beams L14S, L14C and laser beam L15S incident on the scale diffraction grating 130 from the transmission diffraction grating 120, respectively, when viewed from the Y-axis direction. Even if the scale diffraction grating 130 moves along the Z-axis, the positions at which the laser beams L20S, L16P emitted from the scale diffraction grating 130 toward the transmission diffraction grating 120 and incident on the transmission diffraction grating 120 do not change, and no beam shift occurs even when the scale diffraction grating 130 moves in the Z-axis direction, as in conventional measurement apparatuses such as surface encoders. The measurement apparatus 100 of the first embodiment can expand the measurement range in the Z-axis direction, i.e., in the direction perpendicular to the grating surface of the scale diffraction grating 130, compared to conventional measurement apparatuses. Furthermore, while beam shift in the Z-axis direction has conventionally been handled using many optical devices, the present invention has a very simple structure, which makes it possible to miniaturize various optical systems such as the interference optical system 180.

[0057] In the measuring apparatus 100 of the first embodiment, the laser light emitting unit 110 has a laser light source 111 that emits laser light (light) L11 including laser light L12S and laser light L13P, and a collimating lens 112 that collimates the laser light L11 emitted from the laser light source 111. In the measuring apparatus 100 of the first embodiment, the laser lights (incident light) L14S, L14C, and L15S that are incident on the scale diffraction grating 130 are collimated light.

[0058] In the measuring device 100 of the first embodiment, collimated laser beams L14C and L15S are incident on the scale diffraction grating 130, so that the spread of the laser beams L16C, L16P, and L20S emitted from the scale diffraction grating 130 in a direction intersecting the optical axis is suppressed, and the measurement accuracy of the displacement amounts Δx and Δz and the measurement range in the Z-axis direction can be ensured.

[0059] In the first embodiment, the laser beam L14C is incident on the scale diffraction grating 130 and the laser beam L16C is emitted, but a mirror may be placed in this location instead of the scale diffraction grating 130. For the zero-order diffracted beam, the scale diffraction grating 130 only needs to function in the same way as a mirror.

[0060] In the measuring device 100 of the first embodiment, the laser light L11 emitted from the laser light source 111 is polarized and separated by the polarizing beam splitter 113, and can be separated into S-polarized laser light L12S and P-polarized laser light L13P in a simple, compact manner and with low loss.

[0061] In the measuring apparatus 100 of the first embodiment, the pitch g of the scale diffraction grating 130 is half the pitch 2g of the transmission diffraction grating 120, and therefore the angle of incidence of the laser light L15S that is emitted from the transmission diffraction grating 120 and enters the scale diffraction grating 130 is approximately equal to the diffraction angle of the laser light L20S that is diffracted by the scale diffraction grating 130 and emitted as +1st order diffracted light from the scale diffraction grating 130. This makes it possible to overlap the optical path of the laser light L15S that enters the scale diffraction grating 130 from the transmission diffraction grating 120 with the optical path of the laser light L20S that is the +1st order diffracted light that enters the transmission diffraction grating 120 from the scale diffraction grating 130, and return the laser light L20S to the transmission diffraction grating 120. According to the measuring apparatus 100 of the first embodiment, the laser light L20S, which is +1st-order diffracted light having high diffraction efficiency among the diffracted lights emitted from the scale diffraction grating 130, is returned from the scale diffraction grating 130 to the transmission diffraction grating 120, thereby strengthening the interference beam IB1 and the interference signal S1, and thereby improving the measurement accuracy and measurement sensitivity of the displacement amounts Δx and Δz.

[0062] In the measurement apparatus 100 of the first embodiment, the scale diffraction grating 130 has a uniaxial diffraction pattern. That is, a one-dimensional diffraction grating having a predetermined pitch g in the X-axis direction is formed on the grating surface of the scale diffraction grating 130 that is parallel to the X-axis direction and the Y-axis direction. The slit lines of the diffraction grating of the scale diffraction grating 130 extend along the Y-axis direction.

[0063] The measuring apparatus 100 of the first embodiment can measure two-axis displacement (multi-axis displacement) of the scale diffraction grating 130, that is, the displacement amount Δx in the X-axis direction and the displacement amount Δz in the Z-axis direction.

[0064] Although not shown, in the measurement apparatus 100 of the first embodiment, the scale diffraction grating 130 may have a biaxial diffraction pattern. That is, a two-dimensional diffraction grating having a predetermined pitch g in the Y-axis direction in addition to the X-axis direction may be formed on the grating surface of the scale diffraction grating 130. In this case, in addition to the displacement amount Δx in the X-axis direction and the displacement amount Δz in the Z-axis direction of the scale diffraction grating 130, the displacement amount Δy in the Y-axis direction can be measured, thereby measuring triaxial displacement (multiaxial displacement). Note that by adding a one-dimensional diffraction grating having a predetermined pitch g in the Y-axis direction as in a third embodiment described later, triaxial displacement (multiaxial displacement) can be measured; this will be described in detail in the third embodiment.

[0065] The measurement method of the first embodiment uses the measurement apparatus 100 of the first embodiment to measure the displacement amounts Δx and Δz in the X-axis and Z-axis directions of the scale diffraction grating 130 (multiaxial displacements). The measurement method of the first embodiment uses the measurement apparatus 100, and therefore can expand the measurement range in the Z-axis direction, i.e., in the direction perpendicular to the grating surface of the scale diffraction grating 130, compared to when a conventional measurement apparatus such as a surface encoder is used.

[0066] Second Embodiment Next, a second embodiment of the present invention will be described with reference to Fig. 4. In the description of the measurement device and measurement method of the second embodiment, duplicated descriptions of content common to the measurement device 100 and measurement method of the first embodiment will be omitted. Among the components of the measurement device of the second embodiment, components common to the measurement device 110 of the first embodiment will be assigned the same reference numerals as those of the measurement device 110.

[0067] 4 is a schematic diagram of a measuring apparatus 300 according to a second embodiment of the present invention. The measuring apparatus 300 includes a laser beam emitting unit 110, a transmission type diffraction grating 120, a wave plate 124, a scale diffraction grating 130, an interference optical system 210, a reference beam emitting unit 140, a light receiving unit 192, and a displacement calculating unit 202.

[0068] The configuration of the measurement apparatus 300 of the second embodiment differs from that of the first embodiment in the optical paths of the interference beams IB1 and IB2 from the non-polarizing beam splitter 220 onward.

[0069] The interference optical system 210 has a reflecting mirror 134 and a wave plate 150, and further has a non-polarizing beam splitter 220, a phase difference plate 230, and a wave plate 240. The transmission diffraction grating 120 also plays the role of the interference optical system 210, as in the first embodiment.

[0070] The non-polarizing beam splitter 220 is disposed across the optical path of the interference beam IB1 of the laser beams L19P and L21S emitted from the reflecting mirror 134, and the optical path of the interference beam IB2 of the laser beam L18P emitted from the transmission diffraction grating 120 and the laser beam L30S emitted from the reference beam emission unit 140. The non-polarizing beam splitter 220 is disposed between the polarizing beam splitter 113 and the wave plate 150 in the MZ direction.

[0071] The non-polarizing beam splitter 220 is, for example, a cube-shaped beam splitter that has a half-mirror film that transmits approximately half of the incident light and reflects most of the remaining light, regardless of the polarization direction of the incident light. The non-polarizing beam splitter 220 transmits approximately half of the laser beams L19P and L21S incident along the MZ direction and emits them in the MZ direction as an interference beam IB1A, and reflects the remaining approximately half of the laser beams L19P and L21S incident along the MZ direction and emits them in the X-axis direction as an interference beam IB1B. The non-polarizing beam splitter 220 transmits approximately half of the laser beams L18P and L30S incident along the MZ direction and emits them in the MZ direction as an interference beam IB2A, and reflects the remaining approximately half of the laser beams L19P and L21S incident along the MZ direction and emits them in the X-axis direction as an interference beam IB2B.

[0072] The retardation plate 230 is disposed across the optical path of the interference beam IB1B of the laser beams L19P and L21S emitted from the non-polarizing beam splitter 220 in the X-axis direction, and the optical path of the interference beam IB2B of the laser beams L18P and L30S emitted from the non-polarizing beam splitter 220 in the X-axis direction. Separate retardation plates 230 may be disposed on the optical paths of the interference beam IB1B and IB2B. By passing through the retardation plate 230, which is disposed so that its fast axis coincides with the S-polarized light, the laser beam L19P incident along the X-axis direction is given a phase delay of 90° relative to the L21S light. The laser beam L18P incident along the X-axis direction is given a phase delay of 90° relative to the L30S light. The phase difference plate 230 shifts the phase of the interference beams IB1B and IB2B and the laser light constituting these interference beams by 90° relative to the interference beams IB1A and IB2A and the laser light constituting these interference beams. The phase difference plate 230 is, for example, a quarter-wave plate.

[0073] The wave plate 240 is disposed across the optical paths of the interference beams IB1B and IB2B emitted from the retardation plate 230. Separate wave plates may be disposed on the optical paths of the interference beam IB1B and IB2B. The wave plate 240 is, for example, a polarizing plate, and forms a 45° angle with both P-polarized light and S-polarized light. The wave plate 240 rotates the polarization direction of the incident light. The wave plate 240 rotates the polarization direction of each of the laser beams L19P, L21S, L18P, and L30S incident along the X-axis direction, and emits them in the X-axis direction. The wavelength plate 240 adjusts the polarization direction of the laser beams L19P and L21S of the incident interference beam IB1B and the laser beams L18P and L30S of the incident interference beam IB2B, and emits them in the X-axis direction as laser beams L19C and L21C and laser beams L18C and L30C.

[0074] The wave plate 150 adjusts the polarization direction of the laser beams L19P and L21S of the incident interference beam IB1A and the laser beams L18P and L30S of the incident interference beam IB2A, and emits them in the MZ direction as laser beams L19C and L21C and laser beams L18C and L30C.

[0075] The light receiving unit 192 includes a first light receiving unit 160 and a second light receiving unit 170, and further includes a third light receiving unit 250 and a fourth light receiving unit 260. The third light receiving unit 250 is disposed on the optical paths of the interference beam IB1B and the laser beams L19C and L21C emitted from the wave plate 240. The third light receiving unit 250 receives the laser beams L19C and L21C incident along the X-axis direction, generates an interference signal S3 of the laser beams L19C and L21C, and outputs the interference signal S3. The fourth light receiving unit 260 is disposed on the optical paths of the laser beams L18C and L30C emitted from the wave plate 240. The fourth light receiving unit 260 receives the laser beams L18C and L30C incident along the X-axis direction, generates an interference signal S4 of the laser beams L18C and L30C, and outputs the interference signal S4. Like the first light receiving section 160 and the second light receiving section 170, the third light receiving section 260 and the fourth light receiving section 270 are each configured with, for example, a PD, a PSD, an imaging element, or the like.

[0076] The displacement calculation unit 202 is electrically connected to each of the first light receiving unit 160 , the second light receiving unit 170 , the third light receiving unit 250 , and the fourth light receiving unit 260 .

[0077] In the configuration of the measurement device 300, the light intensity I of the interference signal S2 （０，ｒｅｆ）＿０° is expressed by the following equation (6).

[0078]

[0079] The light intensity I of the interference signal S4 （０，ｒｅｆ）＿９０° is expressed by the following equation (7).

[0080]

[0081] From equations (6) and (7), the displacement Δz of the scale diffraction grating 130 in the Z-axis direction is expressed by the following equation (8).

[0082]

[0083] In the configuration of the measurement device 300, the optical intensity I of the interference signal S1 （０，＋１）＿０° is expressed by the following equation (9).

[0084]

[0085] In the configuration of the measurement device 300, the light intensity I of the interference signal S3 （０，＋１）＿９０° is expressed by the following equation (10).

[0086]

[0087] From equations (8), (9), and (10), the displacement Δx of the scale diffraction grating 130 in the X-axis direction is expressed by the following equation (11).

[0088]

[0089] The displacement calculation unit 202 receives the interference signal S2 output from the second light receiving unit 170 and the interference signal S4 output from the fourth light receiving unit 260, and applies the interference signals S2 and S4 to equations (6) and (7) including the above-mentioned displacement amount Δz, thereby detecting the displacement amount Δz alone. The displacement calculation unit 202 further receives the interference signal S1 output from the first light receiving unit 160 and the interference signal S3 output from the third light receiving unit 250, and applies the interference signals S1 and S3 to equations (9) and (10) including the above-mentioned displacement amounts Δx and Δz, thereby detecting the displacement amount Δx using the already detected displacement amount Δz. The displacement calculation unit 202 is, for example, a computer and has a processor that performs calculations related to the above-mentioned equations (6) to (11) and the calculation of the displacement amounts Δx and Δz.

[0090] The measurement apparatus 300 uses two sets of interference signals S1, S3 and S2, S4, which have a phase difference of 90° from each other, and therefore detects not only the displacement amount Δx of the scale diffraction grating 130 in the X-axis direction and the displacement amount Δz of the scale diffraction grating 130 in the Z-axis direction, but also the direction of displacement of the scale diffraction grating 130 in the X-axis direction and the direction of displacement of the scale diffraction grating 130 in the Z-axis direction.

[0091] The measuring apparatus 300 of the second embodiment described above includes the laser beam emitting unit 110, the transmission diffraction grating 120, the scale diffraction grating 130, the interference optical system 210, the light receiving unit 192, and the displacement calculating unit 202. The interference optical system 210 generates interference beams (first interference beams) IB1A and IB1B by superimposing laser beams (third laser beams) L20S and L21S returning from the scale diffraction grating 130 along an optical path overlapping with the laser beam L15S and a laser beam (fourth laser beam) L16C and L16P returning from the scale diffraction grating 130 along an optical path overlapping with the zeroth-order diffracted beam (part of the fourth laser beam) L19P. The interference optical system 210 generates interference beams (second interference beams) IB2A and IB2B by superimposing a laser beam (another part of the fourth laser beam) L18P that is another part of the laser beams (fourth laser beams) L16C and L16P emitted from the scale diffraction grating 130 and a laser beam L30S emitted from the reference beam emission unit 140. The light receiving unit 192 receives the interference beams IB1A and IB1B to generate interference signals (first interference signals) S1 and S3, and receives the interference beams (second interference beams) IB2A and IB2B to generate interference signals (second interference signals) S2 and S4. The displacement calculation unit 202 calculates a displacement amount Δx in the X-axis direction and a displacement amount Δz in the Z-axis direction of the scale diffraction grating 130 from the interference signals S1, S3 and S2, S4.

[0092] In the measurement apparatus 300 of the second embodiment, similarly to the measurement apparatus 100 of the first embodiment, the optical paths of the laser beams L16C, L16P and laser beam L20S emitted from the scale diffraction grating 130 toward the transmission diffraction grating 120 substantially overlap with the optical paths of the laser beams L14S, L14C and laser beam L15S incident on the scale diffraction grating 130 from the transmission diffraction grating 120 when viewed from the Y-axis direction. Even when the scale diffraction grating 130 moves along the Z-axis, the positions at which the laser beams L20S, L16P emitted from the scale diffraction grating 130 toward the transmission diffraction grating 120 and incident on the transmission diffraction grating 120 do not change, and beam shift does not occur as in conventional measurement apparatuses such as surface encoders. The measurement apparatus 300 of the second embodiment has an expanded measurement range in the Z-axis direction, i.e., in the direction perpendicular to the grating surface of the scale diffraction grating 130, compared to conventional measurement apparatuses, enabling the miniaturization of various optical systems such as the interference optical system 210.

[0093] The measuring device 300 of the second embodiment has a configuration in common with the measuring device 100 of the first embodiment, and therefore can obtain the same effects as those of the measuring device 100 of the first embodiment.

[0094] In the measurement apparatus 300 of the second embodiment, the interference optical system 210 includes a reflecting mirror 134, a wave plate (first wave plate) 150, a retardation plate 230, and a wave plate (second wave plate) 240. The reflecting mirror 134 parallelizes the laser light (third laser light) L21S, the laser light (part of the fourth laser light) L19P, and the laser light (another part of the fourth laser light) L18P. Specifically, the reflecting mirror 134 reflects the laser light L21S and L19P emitted from the transmission diffraction grating 120 in the D2 direction, emits them along the MZ direction, and parallelizes them with the laser light L18P emitted from the transmission diffraction grating 120 in the MZ direction. The wave plate 150 adjusts the polarization direction of a portion of each of the laser beams L18P and L30S to generate an interference beam (first interference sub-beam) IB1A that forms the interference beam IB1 and an interference beam (second interference sub-beam) IB2A that forms the interference beam IB2. The phase difference plate 230 shifts the phase of the interference beams IB1B and IB2B and the laser beams that form these interference beams by 90° relative to the interference beams IB1A and IB2A and the laser beams that form these interference beams. The wave plate 240 adjusts the polarization direction of a portion of each of the laser beams L19P and L21S to generate an interference beam (third interference sub-beam) IB1B that forms the interference beam IB1 and an interference beam (fourth interference sub-beam) IB2B that forms the interference beam IB2.

[0095] In the measurement apparatus 300 of the second embodiment, a phase difference of 90° is imparted to the interference beams IB1B and IB2B with respect to the interference beams IB1A and IB2A, and the displacement amounts Δx and Δz are detected using two sets of interference signals S1, S3 and S2, S4 which have a phase difference of 90° from each other. According to the measurement apparatus 300 of the second embodiment, in addition to the displacement amount Δx of the scale diffraction grating 130 in the X-axis direction and the displacement amount Δz of the scale diffraction grating 130 in the Z-axis direction, the direction of displacement of the scale diffraction grating 130 in the X-axis direction and the direction of displacement of the scale diffraction grating 130 in the Z-axis direction can be detected.

[0096] The measurement method of the second embodiment uses the measurement apparatus 300 of the second embodiment to measure the displacement amounts Δx and Δz in the X-axis and Z-axis directions (multiaxial displacements) of the scale diffraction grating 130. The measurement method of the second embodiment uses the measurement apparatus 300, and therefore the measurement range in the Z-axis direction, i.e., the direction perpendicular to the grating surface of the scale diffraction grating 130, can be expanded compared to when a conventional measurement apparatus such as a surface encoder is used. Furthermore, the measurement method of the second embodiment can detect the displacement amount Δx of the scale diffraction grating 130 in the X-axis direction and the displacement amount Δz of the scale diffraction grating 130 in the Z-axis direction, as well as the displacement direction of the scale diffraction grating 130 in the X-axis direction and the Z-axis direction.

[0097] Third Embodiment Next, a third embodiment of the present invention will be described with reference to Fig. 5. In the description of the measurement device and measurement method of the third embodiment, duplicated descriptions of content common to the measurement device 100 and measurement method of the first embodiment and the measurement device 300 and measurement method of the second embodiment will be omitted. Of the components of the measurement device of the third embodiment, components common to the first and second embodiments will be assigned the same reference numerals.

[0098] In addition, since elements in the Y-axis direction are included in FIG. 5, the configuration of the measurement apparatus 400 of the third embodiment is shown three-dimensionally.

[0099] As shown in FIG. 5 , the measuring apparatus 400 of the third embodiment is configured by adding a configuration to the measuring apparatus 300 of the second embodiment. In the third embodiment, a transmission-type diffraction grating 320 that generates a Y-axis direction laser light is added. A mirror 340 that collimates the generated Y-axis direction laser light and causes it to enter the light receiving unit 192 is also added. The moving stage 132 supports a diffraction grating 130 corresponding to the X-axis direction, a scale diffraction grating 330 corresponding to the Y-axis direction, and a mirror (reflective element) 310 corresponding to the zeroth-order diffracted light. The mirror 310 may be substituted with a scale diffraction grating (first scale diffraction grating, reflective element) 130 or a scale diffraction grating (second scale diffraction grating, reflective element) 330, which is a reflective diffraction grating.

[0100] The transmission diffraction grating 320 is disposed in the Z-axis direction of the transmission diffraction grating 120, i.e., at a position where the laser light L12S has passed through the transmission diffraction grating 120. The transmission diffraction grating 320 may also be disposed in front of the transmission diffraction grating 120 in the Z-axis direction.

[0101] The transmission diffraction grating 320 is an element in which a one-dimensional diffraction grating having a period of 2g in the Y-axis direction is formed on the plate surface of a transparent substrate. The slit lines of the one-dimensional diffraction grating of the transmission diffraction grating 320 extend parallel to the X-axis direction. In other words, the slit lines of the transmission diffraction grating 120 are arranged perpendicular to the slit lines of the transmission diffraction grating 320.

[0102] The transmission diffraction grating 320 separates the laser beam L14S, which is transmitted through the transmission diffraction grating 120 and incident along the Z-axis direction, into laser beam L32S, which is a zeroth-order diffracted beam that travels linearly in at least the Z-axis direction, and laser beam L33S, which is a ±1st-order diffracted beam that is inclined at a predetermined angle toward the Y-axis and Z-axis directions and travels in the D5 or D7 direction on a plane including the Y-axis and Z-axis directions. Note that, for simplicity, the −1st-order diffracted beam in the D7 direction is not shown in FIG. 1.

[0103] The scale diffraction grating 330 is disposed in an area irradiated with the laser beam L33S emitted from the transmission diffraction grating 320 in the direction D5. The scale diffraction grating 330 is, for example, a reflection diffraction grating. The grating surface of the scale diffraction grating 330 is along the X-axis direction. Although not shown in FIG. 5 , a diffraction grating (not shown in FIG. 5 ) is formed on the surface of the scale diffraction grating 330 on the transmission diffraction grating 320 side and parallel to the X-axis direction. The period (pitch) of the scale diffraction grating 330 is set to g, which is half the period (pitch) of the transmission diffraction grating 320.

[0104] The laser light L33S emitted from the transmission diffraction grating 320 is incident on the scale diffraction grating 330. The scale diffraction grating 330 then emits the incident laser light L33S in a direction D6 that is opposite to the incident direction D5. That is, at least a portion of the laser light L33S that is incident on the scale diffraction grating 330 from the transmission diffraction grating 320 returns as laser light L37S from the scale diffraction grating 330 to the transmission diffraction grating 320 in the opposite direction along substantially the same optical path as when the laser light was incident on the scale diffraction grating 330.

[0105] Laser light L32S emitted from the transmission diffraction grating 320 is incident on the reflection mirror 310 via the wave plate 124. The reflection mirror 310 reflects the incident laser light L32C and emits it as laser light L34C in the MZ direction parallel to the Z-axis direction and opposite to the Z-axis direction. In other words, the laser light L32C incident on the mirror 310 from the transmission diffraction grating 320 returns to the transmission diffraction grating 320 from the mirror 310 as laser light L34C in the opposite direction along substantially the same optical path as when it entered the mirror 310.

[0106] The transmissive diffraction grating 320 separates the laser beam L34P incident along the MZ direction into laser beam L36P, which is ±1st-order diffracted light traveling at least in the D6 direction or the D8 direction, and laser beam L35P, which is 0th-order diffracted light traveling in the MZ direction. For simplicity, the −1st-order diffracted light traveling in the D8 direction is not shown in FIG. 5 . The transmissive diffraction grating 320 separates the laser beam L37S incident along the D6 direction into laser beam L38S, which is 0th-order diffracted light traveling at least in the D6 direction, and laser beam L38S traveling in the MZ direction, which is parallel to the Z-axis direction and opposite to the Z-axis direction.

[0107] The transmission diffraction grating 120 separates the laser beam L35P incident along the MZ direction into laser beam L40P, which is ±1st-order diffracted light traveling at least in the D2 and D4 directions, and laser beam L39P, which is 0th-order diffracted light traveling in the MZ direction. For simplicity, the −1st-order diffracted light traveling in the D4 direction is not shown in FIG. 5. In the optical paths of the laser beams L39P and L40P, the configuration of the measurement apparatus 400 downstream from the transmission diffraction grating 120 is the same as that of the measurement apparatus 100 of the first embodiment.

[0108] The reflecting mirror 340 reflects the laser beams L36P and L38S incident along the D6 direction and emits the laser beams L36P and L38S in the MZ direction. The laser beams L36P and L38S emitted from the reflecting mirror 340 in the same MZ direction are superimposed to generate an interference beam IB3.

[0109] In the optical paths of the interference beams IB1 and IB2, the configuration from the non-polarizing beam splitter 220 onward in the measuring apparatus 400 of the third embodiment is the same as that of the measuring apparatus 300 of the second embodiment, except that light receiving units 350 and 360 for detecting the interference beams IB3A and IB3B are added.

[0110] In the configuration of the measurement device 400, the optical intensity I of the interference signal S5 （０，Ｙ＋１）＿０° is expressed by the following equation (12).

[0111]

[0112] In the configuration of the measurement device 400, the optical intensity I of the interference signal S （０，＋１）＿９０° is expressed by the following equation (13).

[0113]

[0114] From equations (8), (12), and (13), the displacement Δy of the scale diffraction grating 330 in the Y-axis direction is expressed by the following equation (14).

[0115]

[0116] As described above, the measuring apparatus 400 of the third embodiment can measure the amount of displacement in the Y-axis direction in addition to the X-axis direction and Z-axis direction by arranging the transmission diffraction grating 320 and the scale diffraction grating 330. According to the measuring method of the third embodiment, since the measuring apparatus 400 is used, it is possible to measure the amount of displacement in the three axes of X, Y, and Z while expanding the measurement range in the Z-axis direction compared to when a conventional measuring apparatus such as a surface encoder is used.

[0117] Although the preferred embodiments of the present invention have been described in detail above, the present invention is not limited to the above-described embodiments. Various modifications are possible within the scope of the gist of the present invention as set forth in the claims. Furthermore, the configurations of different embodiments may be combined as appropriate.

[0118] For example, the scale diffraction grating 130 may be an element (first scale diffraction grating) that is not disposed in the region where the laser beam L14C is incident, but is disposed in the region where the laser beam 15S is incident, and that has a blazed grating formed thereon that retroreflects the laser beam 15S and returns it to the transmission diffraction grating 120 via the same path as the laser beam L20S. In this case, a reflective element having a reflective surface that reflects the laser beam L14C and returns it to the transmission diffraction grating 120 via the same path as the laser beam 16C is disposed in the region where the laser beam L14C is incident. Furthermore, the scale diffraction grating 130 may be any element that can emit light that propagates via the same optical path as the laser beams L16C and L20S, and for example, a multi-level diffraction grating (first scale diffraction grating) may be used.

[0119] 100, 300, 400 Measuring device 110 Laser light irradiation unit 111 Laser light source 112 Collimating lens 113 Polarizing beam splitter 120 Transmission type diffraction grating (first transmission type diffraction grating) 124 Wave plate 130 Scale diffraction grating (first scale diffraction grating, reflective element) 132 Moving stage 134 Reflecting mirror 140 Reference light emitting unit 142 Wave plate 144 Reflecting mirror 150 Wave plate 160 First light receiving unit 170 Second light receiving unit 200, 202 Displacement calculation unit 210 Interference optical system 220 Non-polarizing beam splitter 230 Phase difference plate 240 Wave plate 250 Third light receiving unit 260 Fourth light receiving unit 310 Mirror (reflective element) 320 Transmission type diffraction grating (second transmission type diffraction grating) 330 Scale diffraction grating (second scale diffraction grating, reflective element) 340 Reflection mirror

Claims

1. A measuring device comprising: a laser light emitting unit that emits a first laser light and a second laser light; a transmission type diffraction grating into which the first laser light emitted from the laser light emitting unit is incident; a scale diffraction grating into which the ±1st order diffracted light emitted from the transmission type diffraction grating is incident; a reflection element into which the 0th order diffracted light emitted from the transmission type diffraction grating is incident; a reference light emitting unit that receives the second laser light emitted from the laser light emitting unit and emits a reference light; an interference optical system that overlaps a part of a third laser light returning in an optical path overlapping with the ±1st order diffracted light from the scale diffraction grating and a part of a fourth laser light returning in an optical path overlapping with the 0th order diffracted light from the reflection element to generate a first interference beam, and overlaps another part of the fourth laser light emitted from the reflection element and the reference light emitted from the reference light emitting unit to generate a second interference beam; a light receiving unit that receives the first interference beam to generate a first interference signal and receives the second interference beam to generate a second interference signal; and a displacement calculation unit that calculates a displacement amount of the scale diffraction grating from the first interference signal and the second interference signal.

2. The measuring device according to claim 1, wherein the laser light emitting unit includes: a laser light source that emits light including the first laser light and the second laser light; and a collimating lens that collimates the light emitted from the laser light source, and the incident light incident on the scale diffraction grating is collimated light.

3. The measuring device according to claim 1, wherein the laser light emitting unit includes: a laser light source that emits light including the first laser light and the second laser light; and a polarization beam splitter that separates S-polarized light and P-polarized light included in the light emitted from the laser light source, the first laser light is S-polarized light, and the second laser light is P-polarized light.

4. The measuring device according to claim 1, wherein the pitch of the scale diffraction grating is 1 / 2 of the pitch of the transmission type diffraction grating, and the third laser light is the +1st order diffracted light that is diffracted by the scale diffraction grating when the +1st order diffracted light incident on the scale diffraction grating is emitted from the scale diffraction grating.

5. The interference optical system includes: a reflection mirror that makes the third laser beam, a part of the fourth laser beam, and another part of the fourth laser beam parallel to each other; a first wave plate that adjusts the polarization directions of the fourth laser beam and the reference light respectively, and generates a first interference sub-beam forming the first interference beam and a second interference sub-beam forming the second interference beam; a phase difference plate that gives a 90° phase difference to the first interference sub-beam and the second interference sub-beam to generate a third interference sub-beam forming the first interference beam and a fourth interference sub-beam forming the second interference beam; a second wave plate that adjusts the polarization directions of the fourth laser beam and the reference light respectively, and generates the third interference sub-beam and the fourth interference sub-beam. The measuring device according to claim 1.

6. The transmission diffraction grating has a first transmission diffraction grating and a second transmission diffraction grating. The first transmission diffraction grating and the second transmission diffraction grating are arranged side by side on the optical axis of the first laser beam incident on the transmission diffraction grating. When viewed along the optical axis, the slit line of the first transmission diffraction grating is perpendicular to the slit line of the second transmission diffraction grating. The measuring device according to claim 1.

7. The scale diffraction grating has a first scale diffraction grating and a second scale diffraction grating. The first scale diffraction grating and the reflection element are arranged along a direction parallel to one of the slit lines of the first transmission diffraction grating and the second transmission diffraction grating. The second scale diffraction grating and the reflection element are arranged along a direction parallel to the other of the slit lines of the first transmission diffraction grating and the second transmission diffraction grating. The measuring device according to claim 6.

8. A measuring method of measuring the multi-axis displacement of the scale diffraction grating by using the measuring device according to any one of claims 1 to 7.

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