JP2007178281A - Tilt sensor and encoder - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To measure a relative angular relation between illuminating light and an optical unit. <P>SOLUTION: Since both states of interfering light at a first diffraction grating 127a and a second diffraction grating 127b of the optical unit 26 are varied in response to a relative variation in the angle between the illuminating light emitted by a light source and the optical unit 26 having the first diffraction grating 127a and the second diffraction grating 127b, the relative angular relation between the illuminating light and the optical unit can be measured by receiving the interfering light by using a light receiving element. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a tilt sensor and an encoder, and more particularly, to a tilt sensor for measuring a relative tilt amount between illumination light and a diffraction grating, and an encoder including the tilt sensor.

  Conventionally, for example, an optical encoder as described in Patent Document 1 has been used to measure the position of a test object.

  This optical encoder is an encoder that detects the intensity of illumination light that has passed through both a moving diffraction grating that moves with a moving body and a fixed index diffraction grating as information that indicates the relative positional deviation between the two diffraction gratings. This is called a so-called diffraction interference type encoder.

  Such an optical encoder can only measure the position in the grid arrangement direction. However, recently, it is considered necessary to measure also the rotation of the test object (the inclination direction of the moving grid that moves with the test object with respect to the surface on which the grid is formed).

  Further, for example, if the incident angle of light incident on the diffraction grating for generating three beams of the modulation encoder described in Patent Document 2 can also be measured, accurate position measurement by the modulation encoder can be realized. Become.

JP 2005-55360 A US Patent 6,639,686

  The present invention has been made under the circumstances described above, and from a first viewpoint, the light source that emits illumination light; the first diffraction grating; and the illumination light with respect to the first diffraction grating An optical unit having a second diffraction grating arranged in a predetermined positional relationship with respect to the optical path direction of the optical system; receiving light interfered with the optical unit, and relating to a relative angle change between the illumination light and the optical unit And a light receiving element that outputs a signal.

  According to this, the state of the light that interferes with the first diffraction grating and the second diffraction grating of the optical unit changes according to the relative angle change between the illumination light and the optical unit, and the interference light is received. A signal relating to a relative change in angle between the illumination light and the optical unit is output from the received light receiving element. Therefore, the relative angular relationship between the illumination light and the optical unit can be detected based on the signal.

  From a second viewpoint, the present invention has a light source that emits illumination light; an arbitrary refractive index in which a diffraction grating is provided on the surface on the light source side, and a reflective film is formed on the surface on the opposite side. An optical element; after receiving the light reflected by the reflective film after passing through the diffraction grating and again passing through the diffraction grating, and outputting a signal relating to a relative angle change between the illumination light and the optical element; A second tilt sensor comprising: a light receiving element;

  According to this, in accordance with the relative change in angle between the illumination light incident on the optical element and the optical element, the state of the light that has passed through the diffraction grating, reflected by the reflective film, and again passed through the diffraction grating changes. And the signal regarding the relative angle change of illumination light and an optical unit is output from the light receiving element which received the light. Therefore, the relative angular relationship between the illumination light and the optical unit can be detected based on the signal.

  According to a third aspect of the present invention, there is provided an encoder for irradiating a pattern arranged along a predetermined direction with illumination light and detecting the pattern, the first diffraction grating and the first diffraction grating. On the other hand, an optical unit having a second diffraction grating arranged in a predetermined positional relationship with respect to the optical path direction of the illumination light; illumination light that receives illumination light that has passed through the optical unit and is incident on the optical unit And a light receiving element that outputs a signal relating to a relative angle change between the optical unit and the optical unit.

  According to this, the signal output from the light receiving element that receives the light diffracted by the first and second diffraction gratings changes in accordance with the relative angle change between the illumination light incident on the optical unit and the optical unit. Therefore, the relationship between the optical unit and the illumination light can be adjusted according to the signal. Therefore, it is possible to perform highly accurate position measurement by performing position measurement using an optical unit that causes illumination light to interfere after adjustment.

  According to a fourth aspect of the present invention, an encoder that irradiates illumination light onto a pattern arranged along a predetermined direction and detects the pattern includes the first and second tilt sensors of the present invention. It is the 2nd encoder characterized.

  According to this, the encoder that measures the position in the in-plane direction perpendicular to the optical axis of the illumination light can detect the relative angle change between the optical unit or optical element having the diffraction grating and the illumination light. Since the first and second tilt sensors of the present invention are provided, the optical unit or the optical element can be adjusted according to the detected angle change. Therefore, highly accurate position measurement can be performed by performing position measurement after adjustment.

<< First Embodiment >>
Hereinafter, a first embodiment of the present invention will be described with reference to FIGS.

  FIG. 1 schematically shows a tilt sensor 100 according to the first embodiment. The tilt sensor 100 includes a light source 120, a collimator lens 121, an optical unit 26, and a light receiving element 136, which are sequentially arranged in the Z-axis direction (the vertical direction in FIG. 1).

  As the light source 120, for example, a short wavelength band VCSEL (surface emitting laser) can be employed. This surface-emitting laser is a near-infrared surface-emitting semiconductor laser that has high uniformity and can be driven at high speed and can be made into a large-scale array.

  The collimator lens 121 converts the laser light emitted from the light source 120 into parallel light.

  The optical unit 26 is made of a glass plate that transmits laser light, and is connected to an object to be measured (moving body) that measures a tilt amount. As shown in an enlarged view in FIG. 2A, a light source side grating 127a is provided on the surface of the glass plate on the light source 120 side, and a light receiving element side grating is provided on the back surface (surface on the light receiving element side). 127b is provided. These gratings 127a and 127b are line-and-space patterns in which a plurality of line patterns whose longitudinal direction is the X-axis direction are arranged in the Y-axis direction, and the pitch of the light source side grating 127a is, for example, 25.0 μm. The pitch of the light receiving element side grating 127b is, for example, 25.6 μm.

  Returning to FIG. 1, the light receiving element 136 is composed of a multi-part light receiving element.

  According to the tilt sensor 100 configured as described above, the laser light emitted from the light source 120 is converted into parallel light by the collimator lens 121 and enters the optical unit 26. The laser light incident on the optical unit 26 interferes as follows.

  FIG. 2A shows a state in which laser light is incident on the upper surface of the optical unit 26 perpendicularly. In this case, the optical unit 26 generates a plurality of diffracted lights at the light source side grating 127a based on the incident parallel light. FIG. 2A shows ± first-order diffracted light generated at three points (point A, point B, point C) of the light source side grating 127a among the diffracted lights.

  Of these, when focusing on the + 1st order diffracted light generated at the point A, the + 1st order diffracted light further generates a plurality of diffracted lights at the point AB of the light receiving element side grating 127b. Here, in FIG. 2 (A), only ± first-order diffracted light is shown (not shown in parentheses), and among them, the contribution to interference is indicated by a solid line in FIG. 2 (A). -1st order diffracted light. On the other hand, for the −1st order diffracted light generated at the point A, a plurality of diffracted lights are further generated at the AC point of the light receiving element side grating 127b. Here, in FIG. 2 (A), only ± first-order diffracted light is shown (not shown in parentheses), and among them, the contribution to interference is shown by a solid line in FIG. 2 (A). + 1st order diffracted light.

  Next, when attention is paid to the −1st order diffracted light generated at the point B, the −1st order diffracted light further generates a plurality of diffracted lights at the point AB of the light receiving element side grating 127b. Here, in FIG. 2 (A), only ± first-order diffracted light is shown (indicated by parentheses), among which the contribution to interference is indicated by a solid line in FIG. 2 (A). + 1st order diffracted light. The + 1st order diffracted light interferes with the −1st order diffracted light generated at the AB point of the light receiving element side grating 127b among the + 1st order diffracted light generated at the point A described above.

  Next, focusing on the + 1st order diffracted light generated at the point C, this + 1st order diffracted light further generates a plurality of diffracted lights at the AC point of the light receiving element side grating 127b. Here, in FIG. 2 (A), only ± first-order diffracted light is shown (indicated by parentheses), among which the contribution to interference is indicated by a solid line in FIG. 2 (A). -1st order diffracted light. The -1st order diffracted light interferes with the + 1st order diffracted light generated at the AC point of the light receiving element side grating 127b among the -1st order diffracted light generated at the point A described above.

  In this way, interference fringes are formed on the light receiving element 136 due to the interference of the laser light passing through the optical unit 26.

  FIG. 2B shows a state in which the laser light is incident on the upper surface of the optical unit 26 at an angle slightly inclined from the vertical. FIG. 2B shows a state in which the angle of the optical unit 26 is the same and the laser beam is tilted as compared with FIG. 2A. On the contrary, the optical path of the laser beam is different. The same concept can be applied to the case where the optical unit 26 is tilted in the same manner.

  In this case, in the optical unit 26, a plurality of diffracted lights are generated by the light source side grating 127a based on the incident parallel light. In FIG. 2B, among the diffracted lights, three points of the light source side grating 127a ( Only ± first-order diffracted light generated at points A, B ′, and C ′) is shown.

  As shown in FIG. 2B, the + 1st order diffracted light generated at the point A is diffracted again at the point AB ′ of the light receiving element side grating 127b, and the ± 1st order diffracted light (the parentheses in FIG. (Not shown). In this case, −1st order diffracted light indicated by a solid line contributes to interference. On the other hand, the −1st order diffracted light generated at the point A is diffracted again at the AC ′ point of the light receiving element side grating 127b, and ± 1st order diffracted light (shown without parentheses in FIG. 2B). appear. In this case, + 1st order diffracted light indicated by a solid line contributes to interference.

  As can be seen from FIG. 2B, the optical path lengths in the glass member of the + 1st order diffracted light and the −1st order diffracted light generated at point A are different.

  Similarly, the −1st order diffracted light of the ± 1st order diffracted light generated by the diffraction at the B ′ point of the light source side grating 127a is diffracted again at the AB ′ point of the light receiving element side grating 127a, and the ± 1st order diffracted light (in parentheses) To be generated). Of these, the + 1st order diffracted light indicated by the solid line interferes with the −1st order diffracted light generated via the points A and AB ′ described above.

  On the other hand, the + 1st order diffracted light of the ± 1st order diffracted light generated by the diffraction at the point C ′ of the light source side grating 127a is diffracted again at the AC ′ point of the light receiving element side grating 127a, and the ± 1st order diffracted light (with parentheses attached). Generated). Of these, the −1st order diffracted light indicated by the solid line interferes with the + 1st order diffracted light generated via the above-described points A and AC ′.

  In this case, as can be seen from a comparison between FIG. 2A and FIG. 2B, the relative angle between the optical axis of the laser beam and the optical unit 26 varies, so that the corresponding interference light is changed in the Y-axis direction ( In this embodiment, it is shifted in the -Y direction), that is, the interference intensity of the interference fringes changes. The light receiving element 136 detects the interference intensity of the generated interference fringes and outputs a signal including the amount of movement of the interference fringes on the light receiving surface to a control device (not shown). In the tilt sensor 100 of the present embodiment, the origin of measurement does not exist. However, in the initial adjustment, the optical unit 26 is in a desired state (for example, as shown in FIG. Assume that the position of the interference fringe when set to the state of being perpendicularly incident) is regarded as the origin, and a deviation from the origin is detected.

  Here, as in the present embodiment, when a scale in which a grating is arranged on the front and back surfaces of a glass plate is employed, it can be considered that the light source side grating 127a is regarded as an index scale and the light receiving element side grating 127b is regarded as a moving scale. . That is, if the moving scale is tilted and the light beam emission position is changed by one pitch (25.6 μm), the propagation angle inside the glass is θ ′, the glass thickness is t, and the lattice pitch is p. ).

tan θ ′ = p / t (1)
Since the above equation (1) is an equation relating to the inside of the glass, when the refractive index is 1.5 and the actual inclination of the optical unit 26 is θ, the following equation (2) is obtained.

sin θ / sin θ ′ = 1.5
sin θ = 1.5 sin [tan ⁻¹ (p / t)] (2)
Here, if the lattice pitch is 25.6 μm and the glass thickness is 3 mm, θ = 44 (min). Accordingly, since one cycle of the interference fringes corresponds to 44 minutes, the resolution is 44 × 60/512 = about 5.16 (seconds) when the number of interpolation of the light receiving element 136 is 512. In addition, since a multi-segment light receiving element is employed as the light receiving element 136, a two-phase signal can be obtained by detecting values of points having a 90 ° phase difference, and the inclination direction can also be measured.

  In addition, since the optical path length difference variation between ± 1st order diffracted lights due to the tilt does not occur by using the method of the present embodiment, the initial condition of Talbot (Talbot) interference does not change even if the tilt occurs. It is possible to perform stable tilt measurement.

  As described above in detail, according to the tilt sensor of the first embodiment, the optical unit 26 is provided with the light source side grating 127a and the light source side grating 127a at a position separated from the light source side grating 127a by a predetermined distance in the Z-axis direction. The light receiving element side grating 127b is diffracted by the light source side grating 127a and the light receiving element side grating 127b of the optical unit 26 according to the relative angle change between the laser beam and the optical unit 26. Therefore, the relative angular relationship between the laser beam and the optical unit 26 can be measured by detecting the interference fringe with a light receiving element.

  Further, in this embodiment, since the pitches of the light source side grating and the light receiving element side grating are different, the interval (pitch) of interference fringes becomes large. For example, as in this embodiment, when the pitch of the light source side grating is 25.0 μm and the pitch of the light receiving element side grating is 25.6 μm, interference fringes with a pitch of about 0.8 mm are generated. Become. Therefore, since the pitch of the interference fringes used for tilt measurement is large, a change in the intensity of the interference fringes (movement of the interference fringes on the light receiving surface of the light receiving element) can be accurately detected. Thereby, it is possible to improve the tilt measurement accuracy.

<< Second Embodiment >>
Next, an encoder according to a second embodiment of the present invention will be described with reference to FIGS. FIG. 3 shows a schematic configuration of the encoder 17 of the second embodiment.

  The encoder 17 includes a scale 18 extending in the Y-axis direction and a probe unit 19 that emits a beam probe. The scale 18 is formed with a reflective diffraction grating (grating 1) having periodicity in the Y-axis direction. As shown in FIG. 3, this diffraction grating is an uneven surface type diffraction grating. The pitch (cycle) is the same in all sections.

  The probe unit 19 includes a laser diode 20, a bending mirror 22 disposed on the + Y side of the laser diode 20, an optical unit 26, a beam splitter 28, and an objective lens sequentially disposed on the + Z side of the bending mirror 22. 30, a lens 32 and an optical sensor 34 disposed on the + Y side of the beam splitter 28, and a light receiving element 36 disposed on the −Y side of the beam splitter 28.

  The laser diode 20 emits laser light having a wavelength of 640 nm, for example.

  The bending mirror 22 has a function as a vibrating mirror that is vibrated by a driving device 24 including, for example, a piezo element, and the angle of the bending mirror 22 can be adjusted by the driving device 24. A control device (not shown) adjusts the angle of the reflection surface of the mirror 22 with respect to the laser light emitted from the laser diode 20 via the driving device 24 to a desired angle.

  The optical unit 26 is the same as the optical unit in the tilt sensor 100 described above, but here, the light source side grating is based on the incident laser light and the main beam of 0th-order diffracted light and 2 of ± 1st-order diffracted light. Two sub-beams are generated. The arrangement relationship between the main beam and the two sub beams is a relationship in which the main beam is arranged between the two sub beams along the arrangement direction of the grating when these beams are irradiated on the scale.

  The optical sensor 34 is composed of a CCD or the like, and the light receiving element 36 is the same as the light receiving element 136 of the tilt sensor 100 described above, and outputs a detection signal to a control device (not shown).

  In the encoder 17 configured as described above, the laser light emitted from the laser diode 20 is reflected by the bending mirror 22 by approximately 90 °, enters the optical unit 26, and the optical unit 26 generates a main beam, two sub beams, and the like. Then, after passing through the beam splitter 28, the objective lens 30 reaches the grating 1 on the scale 18. The laser light reflected on the grating 1 passes through the objective lens 30, is reflected by the beam splitter 28, and is received by the optical sensor 34 via the lens 32. A signal from the optical sensor 34 is sent to a control device (not shown). Since the principle and circuit configuration of signal detection in this control device are disclosed in detail in JP 2000-511634 A and US Pat. No. 6,639,686, etc., detailed description is omitted. .

The optical sensor 34 receives light in a state of being divided into a main beam of zero-order diffracted light and two sub beams of ± first-order diffracted light. Therefore, when such a probe unit is employed, as the optical sensor 34, as shown in FIG. 4, a four-part optical sensor 34 ₃ for main beam detection and two sensors 34 ₁ for sub beam detection, 34 ₂ and can be used.

The relative distance between the peak of the grating 1 and the vibration center of the beam probe can be detected from the result of receiving the two sub beams, that is, from one of the detection signals from the optical sensors 34 ₁ and 34 ₂ . The result obtained by adding the detected values of the amplitude and phase detected from the signals from the optical sensors 34 ₁ and 34 _{2 is} detected as the measured value of the encoder, and the subtracted result is used as the drift amount of the beam probe due to the position drift of the laser diode. Detected.

Note that four-divided photosensor 34 ₁ outputs, for example a of the sensor, b, c, when the d, from the detection result of the main beam, to create two signals (a + b + c + d , a + c-b over d) Can do. Since these two signals have a phase difference of 90 degrees, these two signals are sent to the control device and used for focus control between the objective lens 30 and the grating 1.

  In this manner, the probe unit 19 outputs laser light toward the scale 18, receives the laser light (beam probe) reflected on the grating 1 of the scale 18 by the optical sensor 34, and a signal corresponding to the light reception result. Is output.

  As can be seen from FIG. 3, the laser light that has passed through the optical unit 26 and reflected by the beam splitter 28 enters the light receiving element 36. Therefore, in the probe unit 19 of the encoder 17 in FIG. 3, the laser diode 20 corresponds to the light source 120 of the tilt sensor 100 in FIG. 1, the light receiving element 36 corresponds to the light receiving element 136 in FIG. Since this is the same as the optical unit 26 of the tilt sensor 100, the tilt sensor 100 ′ having the same function as the tilt sensor 100 of FIG. The tilt sensor 100 ′ can detect the relative angle between the optical unit 26 and the laser light incident on the optical unit 26. Therefore, the control device adjusts the angle of the laser beam incident on the optical unit 26 by adjusting the angle of the bending mirror 22 via the driving device 24 based on the detection result of the tilt sensor 100 ′. As a result, the laser light can be incident on the optical unit 26 at an ideal angle, so that the measurement by the encoder 17 can be performed with high accuracy.

  Since the optical unit 26 generates a main beam and two sub beams, the relative angle may be obtained from these beams, or the relative angle is obtained using any one of the three beams. May be.

  As described above, according to the encoder of the present embodiment, the tilt sensor 100 ′ includes the tilt sensor 100 ′ that can measure the relative angular relationship between the laser beam and the optical unit 26. The angular relationship between the laser beam and the optical unit 26 can be adjusted based on the detection result obtained by. As a result, position measurement by the encoder can be accurately performed over a long period of time.

  Moreover, according to this embodiment, since the optical unit 26 provided in the probe unit 19 of the encoder 17 has a function for measuring the inclination of the optical unit 26, the number of parts can be reduced. Enlargement of the encoder itself can be suppressed.

  In the second embodiment, a reflection type diffraction grating is used as the scale 18. However, the invention is not limited to this, and a transmission type diffraction grating may be used. In this case, the lens 32 and the optical sensor 34 are arranged on the + Z side of the scale 18.

  Note that the encoder of the second embodiment can also be employed in a diffraction interference type or shadow type encoder.

  Furthermore, the optical unit 26 of the second embodiment can be used as the scale 18 of the encoder.

  In each of the above embodiments, a glass plate is used as the optical unit 26. However, the material is not limited to glass as long as it is a member having an arbitrary refractive index. For example, a diffraction grating may be formed in a semiconductor or the like.

  In each of the above embodiments, the case where the grating pitches of the light source side grating 127a and the light receiving element side grating 127b provided in the optical unit 26 are slightly different (25.0 μm and 25.6 μm) has been described. However, the present invention is not limited to this, and both gratings may have the same pitch.

  In each of the above embodiments, the case where the light source side grating 127a and the light receiving element side grating 127b are provided on the front and back surfaces of the glass plate has been described, but the present invention is not limited to this. For example, it is possible to employ an optical unit 26 ′ having the configuration shown in FIG. In this case, the optical unit 26 can be fixed to the object to be measured, for example.

  As shown in FIG. 5A, the optical unit 26 ′ is made of a glass plate, a diffraction grating 127 ′ is provided on the + Z side surface of the glass plate, and a reflective film 129 is provided on the −Z side surface. Is provided.

  According to the optical unit 26 ′ configured as described above, the obliquely incident laser light is diffracted by the diffraction grating 127 ′ to generate ± first-order diffracted light. These ± 1st order diffracted light and 0th order light are totally reflected by the reflection film 129 and diffracted again by the diffraction grating 127 ′. Here, it is the light indicated by the solid line in FIG. 5A that contributes to the interference.

  Here, the principle is the same when comparing FIG. 5 (B) showing the state developed with the reflecting surface as a reference, and FIGS. 2 (A) and 2 (B). Even if it exists, it is clear that the same interference as the said embodiment arises.

  Therefore, as in the case of FIGS. 2A and 2B, the diffracted light of the laser beam diffracted at other points (diffracted by the diffraction grating 127 ′, then reflected by the reflection film 129, and again the diffraction grating Interference light), interference fringes are formed on a light receiving element (not shown) provided behind the optical path.

  Also in this case, as in the above-described embodiment, if the incident angle of the laser beam to the optical unit is different, the position of the interference fringe on the light receiving element changes. Therefore, the laser beam can be detected by detecting the position of the interference fringe. It is possible to detect the incident angle with respect to the optical unit.

  As described above, the tilt sensor of the present invention is suitable for measuring the relative angle between the illumination light and the optical unit. The encoder of the present invention is suitable for pattern detection.

It is the schematic which shows the tilt sensor which concerns on 1st Embodiment. 2A and 2B are views for explaining the principle of the optical unit in FIG. It is the schematic which shows the encoder which concerns on 2nd Embodiment. It is a figure which shows the structure of the light receiving element of FIG. FIG. 5A and FIG. 5B are diagrams showing modifications of the tilt sensor.

Explanation of symbols

  20, 120 ... laser diode (light source), 26 ... optical unit, 26 '... optical element (optical unit), 34, 134 ... light receiving element, 100, 100' ... tilt sensor, 127a ... light source side grating (first diffraction) Grating), 127b... Light receiving element side grating (second diffraction grating), 129... Reflective film, 17... Encoder, IL.

Claims (12)

A light source that emits illumination light;
An optical unit having a first diffraction grating and a second diffraction grating arranged in a predetermined positional relationship with respect to the optical path direction of the illumination light with respect to the first diffraction grating;
A tilt sensor comprising: a light receiving element that receives light that interferes with the optical unit and outputs a signal related to a relative angle change between the illumination light and the optical unit.   The tilt sensor according to claim 1, wherein the optical unit includes a member having an arbitrary refractive index, and the first diffraction grating and the second diffraction grating are formed on the member. . The member is a plate-like member capable of transmitting the illumination light,
The first diffraction grating is formed on the light source side surface of the plate-shaped member,
The tilt sensor according to claim 2, wherein the second diffraction grating is formed on a surface of the plate-like member opposite to the light source side.   The tilt sensor according to claim 3, wherein the grating pitch of the first diffraction grating and the grating pitch of the second diffraction grating are the same or slightly different. The grating pitch of the first diffraction grating and the second diffraction grating is the same,
The tilt sensor according to claim 3, wherein the light receiving element detects a change in an incident angle of the illumination light with respect to the optical unit.   The tilt sensor according to claim 2, wherein the member is made of glass. A light source that emits illumination light;
An optical element having an arbitrary refractive index in which a diffraction grating is provided on the surface on the light source side and a reflective film is formed on the surface on the opposite side;
A light receiving element that receives the light reflected by the reflective film after passing through the diffraction grating and re-passed through the diffraction grating, and outputs a signal relating to a relative angle change between the illumination light and the optical element; A tilt sensor.   The tilt sensor according to claim 1, wherein the light receiving element is a multi-part light receiving element. An encoder that irradiates illumination light to a pattern arranged along a predetermined direction and detects the pattern,
An optical unit having a first diffraction grating and a second diffraction grating arranged in a predetermined positional relationship with respect to the optical path direction of the illumination light with respect to the first diffraction grating;
An encoder comprising: a light receiving element that receives illumination light that has passed through the optical unit, and that outputs a signal related to a relative angle change between the illumination light incident on the optical unit and the optical unit. The optical unit has a plate-like member on which the first diffraction grating and the second diffraction grating are formed,
The encoder according to claim 9, wherein the pattern is formed on the plate-like member. An encoder that irradiates illumination light to a pattern arranged along a predetermined direction and detects the pattern,
The encoder provided with the tilt sensor as described in any one of Claims 1-8.   The encoder according to claim 11, wherein a diffraction grating of an optical unit constituting the tilt sensor is used as a diffraction grating for measuring the position of the object to be measured.

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