JP2015169491A - Displacement detector and displacement detection method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a displacement detector capable of detecting the displacement of a measuring object with a simple configuration.SOLUTION: The displacement detector 3 includes: a retroreflector 31 disposed in a probe; a light source unit 32 for emitting irradiation light L1 capable of irradiating a predetermined range A toward the retroreflector 31; a beam splitter 33 that is disposed between the retroreflector 31 and the light source unit 32, transmits the irradiation light L1, and reflects the reflected light L2 reflected by the retroreflector 31; and a light receiving unit 34 for receiving the reflected light L3 reflected by the beam splitter 33.

Description

  The present invention relates to a displacement detection device and a displacement detection method.

Conventionally, an apparatus for detecting the displacement of an object to be measured is known (for example, see Patent Document 1).
Patent Document 1 discloses a laser tracker. The laser tracker moves one target provided on the object to be measured, and tracks this target with laser light. The displacement of the object to be measured is detected based on the distance to the target based on the reflected light from the target and the spatial angle of the target.

JP 2012-103227 A

  However, the configuration as described in Patent Document 1 requires a mechanism for tracking the target, and there is a problem that the configuration becomes complicated.

  An object of the present invention is to provide a displacement detection device and a displacement detection method capable of detecting the displacement of an object to be measured with a simple configuration.

The displacement detection apparatus of the present invention includes a retroreflector provided on a measurement object, a light source unit that emits irradiation light that can irradiate a predetermined range toward the retroreflector, and the retroreflector. A beam splitter that transmits the irradiation light and reflects the light reflected by the retroreflector, and a light receiving unit that receives the light reflected by the beam splitter. It is characterized by having.
The displacement detection method of the present invention emits irradiation light that can irradiate a predetermined range from a light source unit toward a retroreflector provided on an object to be measured, and between the retroreflector and the light source unit. The beam splitter provided on the light beam transmits the irradiation light, reflects the light reflected by the retroreflector, and receives the light reflected by the beam splitter by the light receiving unit. The displacement of the object to be measured is detected based on a light receiving position.

Another displacement detection apparatus according to the present invention includes a retroreflector provided on an object to be measured, a light source unit that emits irradiation light that can irradiate a predetermined range, and an emission side of the irradiation light with respect to the light source unit. A beam splitter that reflects the irradiated light to enter the retroreflector and transmits the light reflected by the retroreflector, and a light receiving unit that receives the light transmitted through the beam splitter It is characterized by having.
According to another displacement detection method of the present invention, irradiation light capable of irradiating a predetermined range is emitted from a light source unit toward a retroreflector provided on an object to be measured, and the irradiation light is emitted to the light source unit. A beam splitter provided on the exit side reflects the irradiated light to enter the retroreflector, transmits the light reflected by the retroreflector, and receives the light transmitted through the beam splitter. And detecting the displacement of the object to be measured based on the light receiving position at the light receiving portion.

According to such a configuration, the irradiation light emitted to the retroreflector is reflected by the retroreflector after passing through the beam splitter. The light reflected by the retroreflector returns to the beam splitter, is reflected by the beam splitter, and is received by the light receiving unit.
Moreover, according to another structure, the irradiation light radiate | emitted from the light source part reflects in a beam splitter, and injects into a retroreflection body. The light incident on the retroreflector is reflected by the retroreflector, returns to the beam splitter, passes through the beam splitter, and is received by the light receiving unit.
When the retroreflector moves in a direction orthogonal to the optical axis of the irradiation light in the irradiation range of the irradiation light, the light receiving position is displaced corresponding to the movement of the retroreflector.
For this reason, the displacement of the object to be measured can be detected based on the position of the retroreflector that moves in the irradiation range with a simple configuration without providing a configuration for tracking the retroreflector.

  In the displacement detection apparatus of the present invention, it is preferable that the displacement detection apparatus further includes a light collecting unit that is provided between the beam splitter and the light receiving unit and collects light from the beam splitter.

  According to such a configuration, it is possible to reduce the size of the light receiving spot at the light receiving unit, and to improve the displacement detection accuracy of the object to be measured, compared to a configuration in which the light collecting unit is not provided. In addition, since the light receiving spot can be reduced, the displacement detection range can be expanded.

The perspective view which shows the stage apparatus which concerns on 1st Embodiment of this invention. The block diagram which shows the said stage apparatus. The schematic diagram which shows the displacement detection apparatus which comprises the said stage apparatus. FIG. 3 is an enlarged view of a part of the displacement detection device. The perspective view which shows the coordinate measuring machine which concerns on 2nd Embodiment of this invention. The block diagram which shows the said coordinate measuring machine. (A), (B), (C) is a schematic diagram which shows the principal part of the displacement detection apparatus which concerns on the modification of this invention. The schematic diagram which shows the said displacement detection apparatus which concerns on another modification of this invention.

[First Embodiment]
The first embodiment of the present invention will be described below.
{Stage device configuration}
First, the configuration of the stage apparatus according to the first embodiment of the present invention will be described.
In FIG. 1, three axes that are orthogonal to each other will be described as an X axis, a Y axis, and a Z axis, and the vertical direction on the paper surface will be described as a Z axis direction. The machine coordinate system is defined by the X-axis direction, the Y-axis direction, and the Z-axis direction. The same applies to the following drawings.

  As shown in FIGS. 1 and 2, the stage device 1 includes a stage body 2, a displacement detection device 3, and a control device 4.

The stage body 2 includes an XY stage 21 as an object to be measured, a slide mechanism 22 that slides the XY stage 21 in the X-axis direction and the Y-axis direction, and a drive unit 23 that drives the slide mechanism 22.
The XY stage 21 is formed in a rectangular plate shape, and has a placement surface 211 that is substantially parallel to the XY plane. A positioning object (not shown) that is positioned by the stage device 1 is placed on the placement surface 211.
The slide mechanism 22 is constituted by, for example, a slider, a guide rail, etc. (not shown).

  The displacement detection device 3 detects the positions of the XY stage 21 in the X axis direction and the Y axis direction. As shown in FIGS. 1 and 3, the displacement detection device 3 includes a retroreflector 31, a light source unit 32, a beam splitter 33, a light receiving unit 34, a light collecting unit 35, a light source control unit 36, Displacement calculation unit 37 is provided.

  The retroreflector 31 is provided at a predetermined position of the placement surface 211 on the XY stage 21, for example, at a corner. The retroreflector 31 reflects incident light and returns it to the incident direction. An example of the retroreflector 31 is a configuration in which a total reflection film 312 is coated on a hemispherical surface opposite to the light incident direction in the ball lens 311 having a refractive index of 2. Further, the retroreflector 31 may be a so-called corner cube in which three flat plates are combined at a right angle to form a vertex of a cube and a total reflection film is provided on the inner surface thereof.

The light source unit 32, the beam splitter 33, the light receiving unit 34, and the light collecting unit 35 are accommodated in a housing 30 disposed above the XY stage 21.
The light source unit 32 emits irradiation light L <b> 1 that can irradiate a predetermined range toward the retroreflector 31. The light source unit 32 includes a light source 321 that is controlled by the light source control unit 36 and emits diverging light as irradiation light L1. The light source 321 is arranged so that the optical axis (center axis) LA of the irradiation light L1 is substantially parallel to the Z axis. The light source 321 may be arranged so that the optical axis LA intersects the Z axis. The light source 321 is arranged so that the irradiation light L1 can irradiate the circular irradiation range A including the entire range in which the retroreflector 31 provided on the XY stage 21 can move.

  The beam splitter 33 is provided between the retroreflector 31 and the light source unit 32, transmits the irradiation light L1, and reflects the reflected light L2 reflected by the retroreflector 31. As the beam splitter 33, a half mirror, a prism, or the like can be used.

  The light receiving unit 34 receives a later-described condensed light L <b> 4 emitted from the light collecting unit 35 on the light receiving surface 341, and outputs a signal corresponding to the light receiving position to the control device 4. As the light receiving unit 34, a two-dimensional PSD (Position Sensitive Detector (optical position sensor)), a CMOS (Complementary MOS (Metal-Oxide Semiconductor)) image sensor, a CCD (Charge Coupled Device) image sensor, a PD (Photodiode) array, etc. Can be used.

  The condensing part 35 is provided between the beam splitter 33 and the light-receiving part 34, condenses the reflected light L3 reflected by the beam splitter 33, and emits the condensed light L4. The condensing unit 35 includes a condensing lens 351 arranged so that the focal point is located on the light receiving surface 341. For this reason, the light receiving spot SP1 of the condensed light L4 on the light receiving surface 341 has a dot shape.

Here, the positional relationship among the light source 321, the beam splitter 33, and the condenser lens 351 will be described in detail.
First, as shown in FIG. 4, the intersection point P is a position where the optical axis LA of the irradiation light L1 passes on the reflection surface of the reflection light L2 in the beam splitter 33. The condensing lens 351 is arranged so that a line segment M1 connecting the center 351C of the main surface 351A of the condensing lens 351 and the intersection point P is orthogonal to a line segment M2 connecting the light emission point 321A of the light source 321 and the intersection point P. Has been. Further, the condenser lens 351 is arranged so that the length of the line segment M1 is equal to the length of the line segment M2.
With such an arrangement, regardless of the position of the retroreflector 31, the optical axis of the reflected light L3 is positioned on the center 351C of the main surface 351A, and the light on the optical axis of the reflected light L3 is reflected by the condenser lens 351. The light travels straight without being refracted and reaches the light receiving surface 341. Therefore, the light receiving position on the light receiving surface 341 and the position of the retroreflector 31 can be made to correspond accurately.

  For example, when the light source 321, the beam splitter 33, and the condenser lens 351 are arranged so that the length of the line segment M1 is not equal to the length of the line segment M2, depending on the position of the retroreflector 31, The light on the optical axis of the reflected light L3 is refracted by the condenser lens 351 and reaches the light receiving surface 341. In such a case, the light receiving position on the light receiving surface 341 and the position of the retroreflector 31 do not correspond exactly, but the displacement calculation unit 37 performs a correction process to appropriately calculate the displacement. Can do.

The light source control unit 36 controls the light source 321 of the light source unit 32 to emit the irradiation light L1.
The displacement calculation unit 37 calculates the displacement of the XY stage 21 based on the light receiving position of the condensed light L4 at the light receiving unit 34.

  As shown in FIG. 2, the control device 4 includes a drive control unit 41 that controls the drive unit 23 to move the XY stage 21. The light source controller 36 and the displacement calculator 37 constitute a part of the control device 4.

{Position adjustment method by stage device}
Next, a position adjustment method using the stage device 1 will be described.
First, in a state where the XY stage 21 is positioned at a predetermined position, the light source control unit 36 causes the light source 321 to emit the irradiation light L1. At this time, since the entire range in which the retroreflector 31 on the XY stage 21 is movable is included in the irradiation range A of the irradiation light L1, no matter where the XY stage 21 moves, the retroreflection is performed. The body 31 is irradiated with the irradiation light L1.

As shown in FIG. 3, the incident light L11 incident on the retroreflector 31 among the irradiation light L1 transmitted through the beam splitter 33 is reflected by the retroreflector 31, and is reflected as the reflected light L2. Is incident on. The reflected light L2 is reflected by the beam splitter 33 and enters the condenser lens 351 as reflected light L3. The reflected light L3 is collected by the condensing lens 351 and enters the light receiving surface 341 as the condensed light L4.
Here, when the retroreflector 31 moves in the XY plane, the incident angle of the reflected light L2 with respect to the beam splitter 33 and the emission angle of the reflected light L3 change corresponding to this movement. As a result, the light receiving position of the condensed light L4 on the light receiving surface 341 also changes corresponding to the movement of the retroreflector 31. In addition, since the retroreflector 31 does not move in the Z-axis direction, the light receiving spot SP1 of the condensed light L4 on the light receiving surface 341 is always a dot having the same size.
The light receiving unit 34 then outputs a signal corresponding to the light receiving position of the condensed light L4 to the displacement calculating unit 37.

The displacement calculation unit 37 calculates the X coordinate and the Y coordinate of the reference position where the retroreflector 31 in the XY stage 21 is provided based on the signal from the light receiving unit 34. Then, the displacement calculation unit 37 stores the calculated X and Y coordinates of the reference position in a storage unit (not shown) or displays it on a display device (not shown).
Thereafter, when the operator instructs the position adjustment of the XY stage 21 by operating the input unit (not shown), the drive control unit 41 controls the drive unit 23 and moves the XY stage 21 based on this instruction. Then, the measurement of the reference position of the XY stage 21 and the position adjustment of the XY stage 21 by the displacement detection device 3 are repeated until the position adjustment of the XY stage 21 is completed.

{Effect of the first embodiment}
According to the first embodiment, when the irradiation light L <b> 1 is emitted to the retroreflector 31, the light reflected by the retroreflector 31 and the beam splitter 33 is received by the light receiving unit 34. When the retroreflector 31 moves in the XY plane orthogonal to the optical axis LA in the irradiation range A of the irradiation light L1, the light receiving position at the light receiving unit 34 corresponds to the movement of the retroreflector 31. Displace.
Therefore, the displacement of the XY stage 21 can be detected based on the position of the retroreflector 31 that moves in the irradiation range A with a simple configuration without providing a configuration for tracking the retroreflector 31.
Furthermore, since the displacement is detected using light, the response speed can be increased. Moreover, since the members constituting the displacement detection device 3 are not expensive and the electrical equipment is simple, it is possible to reduce the price. Further, since only the retroreflector 31 is provided on the object to be measured, the displacement of the object to be measured in various environments such as an environment with strong electromagnetic noise, vacuum, extremely high temperature, extremely low temperature, high pressure environment, underwater, etc. is detected. be able to.

In addition, the displacement detector 3 is provided with a condensing unit 35 that condenses the reflected light L3 from the beam splitter and emits the condensed light L4.
For this reason, compared with the structure which does not provide the condensing part 35, the size of the light reception spot SP1 in the light-receiving part 34 can be made small, and the displacement detection precision of the XY stage 21 can be improved. Further, since the light receiving spot SP1 can be reduced, the displacement detection range can be expanded.
In particular, in the first embodiment, since the focal point of the condensing lens 351 constituting the condensing unit 35 is located on the light receiving surface 341, the light receiving spot SP1 can be formed in a dot shape. Therefore, compared to a configuration in which the focal point of the condenser lens 351 is not positioned on the light receiving surface 341, the displacement detection accuracy can be improved and the displacement detection range can be expanded.

Furthermore, divergent light capable of irradiating a circular irradiation range A is used as the irradiation light L1.
For this reason, it is possible to detect a two-dimensional displacement of the XY stage 21 that moves within the irradiation range A.

[Second Embodiment]
Hereinafter, a second embodiment of the present invention will be described.
In addition, about the structure same as 1st Embodiment, the same name and the same code | symbol are attached | subjected and detailed description is abbreviate | omitted.

{Configuration of CMM}
As shown in FIGS. 5 and 6, the coordinate measuring machine 1 </ b> A includes a coordinate measuring machine main body 6, a displacement detection device 3, and a control device 7.

  The coordinate measuring machine main body 6 includes a mounting table 61 on which the workpiece W is mounted, a glass plate 62 provided above the mounting table 61, a probe 63 as an object to be measured, and the probe 63 on the glass plate 62. A slide mechanism 64 that slides in the X-axis direction and the Y-axis direction on the opposite surface of the mounting table 61 and a drive unit 65 that drives the slide mechanism 64 are provided. Note that the probe 63 may be slid and positioned by hand without providing the slide mechanism 64 and the drive unit 65. Further, the slide mechanism 64 may be moved by hand without providing only the drive unit 65.

The probe 63 is a so-called non-contact type displacement meter. The probe 63 is formed in a cylindrical shape extending in the vertical direction. The probe 63 is provided so that the cylindrical axis is substantially parallel to the Z axis. The probe 63 includes a light source (not shown). The light emitting point of this light source is located on the cylindrical axis of the probe 63. The probe 63 emits the measurement light L6 from the light source from the lower end, and irradiates the emitted measurement light L6 onto the work W on the mounting table 61. The probe 63 detects the Z-axis direction position of the measurement position on the workpiece W based on the reflected light from the workpiece W, and outputs the detection result to the control device 7.
A retroreflector 31 is provided at the center of the upper end of the probe 63. Specifically, the retroreflector 31 is located on the extension line of the cylindrical shaft in the probe 63. Thereby, the X and Y coordinates of the measurement position on the workpiece W by the probe 63 can be matched with the X and Y coordinates of the retroreflector 31.
The slide mechanism 64 is composed of, for example, a slider, a guide rail, etc. (not shown).

  The displacement detection device 3 detects the position of the probe 63 in the X-axis direction and the Y-axis direction. The light source 321 of the displacement detection device 3 is arranged so that the irradiation light L1 can irradiate a circular irradiation range B including the entire range in which the retroreflector 31 provided on the probe 63 can move.

The control device 7 includes a drive control unit 71, a probe control unit 72, and a coordinate calculation unit 73. The light source control unit 36 and the displacement calculation unit 37 constitute a part of the control device 7.
The drive control unit 71 controls the drive unit 65 to move the probe 63 without changing the posture. In the case where the drive unit 65 is not provided, the drive control unit 71 is not necessary.
The probe control unit 72 controls the probe 63 to detect the position of the measurement position in the Z-axis direction.
The coordinate calculation unit 73 calculates the X, Y, and Z coordinates of the measurement position of the workpiece W based on the calculation result of the displacement calculation unit 37 and the detection result of the probe 63.

{Measuring method with CMM}
Next, a measurement method using the coordinate measuring machine 1A will be described.
First, the drive control unit 71 acquires shape data of the workpiece W from a storage unit (not shown) or the like. Then, the drive control unit 71 controls the drive unit 65 to move the probe 63 above the first measurement position on the workpiece W.
At this time, the probe 63 moves only in at least one of the X-axis direction and the Y-axis direction by the slide mechanism 64 and does not move in the Z-axis direction. Further, the optical axis LA of the irradiation light L1 is set substantially parallel to the Z axis as described above. For this reason, the retroreflector 31 moves only in the XY plane orthogonal to the optical axis LA of the irradiation light L1.
Then, the probe control unit 72 causes the probe 63 to detect the position of the measurement position in the Z-axis direction. The probe 63 outputs a signal corresponding to the detection result to the coordinate calculation unit 73.

The light source controller 36 causes the light source 321 to emit the irradiation light L1.
At this time, since the entire range in which the probe 63 can move is included in the irradiation range B of the irradiation light L1, the retroreflector 31 is irradiated with the irradiation light L1 regardless of the position of the probe 63. The
As shown in FIG. 3, the incident light L11 incident on the retroreflector 31 among the irradiation light L1 transmitted through the beam splitter 33 is condensed by the condenser lens 351, and is received as the condensed light L4. Incident to 341.
The light receiving unit 34 then outputs a signal corresponding to the light receiving position of the condensed light L4 to the displacement calculating unit 37.

The displacement calculation unit 37 calculates the X coordinate and Y coordinate of the position of the probe 63 where the retroreflector 31 is provided, based on the signal from the light receiving unit 34. Then, the displacement calculator 37 outputs the X and Y coordinates of the calculated position to the coordinate calculator 73.
The coordinate calculation unit 73 sets the X and Y coordinates of the retroreflector 31 based on the signal from the displacement calculation unit 37 as the X and Y coordinates of the measurement position on the workpiece W. Then, the coordinate calculation unit 73 stores the set X, Y coordinates and the Z coordinate of the measurement position based on the signal from the probe 63 as the X, Y, Z coordinate of the measurement position on the workpiece W (not shown). Remember me.
Thereafter, the control device 7 repeats the above processing until the measurement at the last measurement position is completed.

{Operational effects of the second embodiment}
According to the second embodiment, a coordinate measuring machine 1A capable of measuring the workpiece W with a simple configuration can be provided.

[Modification]
It should be noted that the present invention is not limited to the above-described embodiment, but includes modifications and improvements as long as the object of the present invention can be achieved.

  For example, in the first embodiment, as shown in FIG. 7A, the displacement detecting device 3 does not have to be provided with the light collecting unit 35. According to such a configuration, the reflected light L3 is incident on the light receiving surface 341 as it is without being condensed, so that the light receiving spot SP2 becomes larger than the case where the light condensing part 35 is provided, but the XY stage 21 It is possible to detect a two-dimensional displacement.

  Further, in order to detect the two-dimensional displacement of the XY stage 21, as shown in FIG. 7B, a collimator lens 322 is provided between the light source 321 and the beam splitter 33, and parallel instead of diverging light. Light may be used as the irradiation light L21. Even with such a configuration, it is possible to detect a two-dimensional displacement of the XY stage 21 that moves within the irradiation range of the irradiation light L21.

Further, in order to detect a one-dimensional displacement of the XY stage 21, as shown in FIG. 7C, a collimator lens 322 and a cylindrical lens 323 or a rod lens 324 are provided between the light source 321 and the beam splitter 33. It is also possible to use line light as the irradiation light L31 instead of diverging light. In this case, it is necessary to provide a cylindrical lens or a rod lens as a condensing lens that condenses the reflected light from the beam splitter 33 on the light receiving surface 341. This is because the reflected light from the beam splitter 33 enters the condenser lens as divergent light in the displacement measurement direction and as parallel light in the direction perpendicular thereto.
Even with such a configuration, it is possible to detect a one-dimensional displacement of the XY stage 21 that moves within the irradiation range of the irradiation light L31. In addition, the retroreflector 31 is irradiated as compared to the configuration in which the retroreflector 31 is irradiated with diverging light or parallel light as shown in the first and second embodiments and FIGS. The amount of light emitted can be increased. Therefore, the displacement of the retroreflector 31 that is further away from the light source 321 than in the case of diverging light or parallel light can be detected, and the displacement detection range can be expanded in the direction in which the line light extends (Y-axis direction).
When line light is used as the irradiation light L31, the light receiving unit 34 may be configured to detect a one-dimensional position, such as a one-dimensional PSD.
Moreover, you may apply the structure shown to FIG. 7 (A)-(C) to 2nd Embodiment.

In the first and second embodiments, a displacement detection device 8 may be provided instead of the displacement detection device 3 as shown in FIG.
In the displacement detection device 8, the beam splitter 33 is provided on the emission side of the irradiation light L <b> 1 with respect to the light source unit 32. The beam splitter 33 reflects the irradiation light L1, and irradiates the irradiation range A with the reflected light L41 reflected. Of the reflected light L41, incident light L42 incident on the retroreflector 31 is reflected by the retroreflector 31 and enters the beam splitter 33 as reflected light L43. The beam splitter 33 transmits the reflected light L43 from the retroreflector 31. The light receiving unit 34 receives the condensed light L44 that is transmitted through the beam splitter 33 and emitted from the condensing lens 351 of the condensing unit 35 by the light receiving surface 341.
In the displacement detection device 8, the positional relationship among the light source 321, the beam splitter 33, and the condenser lens 351 is preferably the same as that shown in FIG.
Furthermore, in the displacement detection device 8, as shown in FIGS. 7A to 7C, a configuration in which the light collecting unit 35 is not provided, or a configuration in which parallel light or line light is used as irradiation light may be applied.

  Furthermore, the displacement detection device of the present invention is used for detecting the displacement of any object other than the XY stage 21 and the probe 63, detecting the displacement of the stylus provided in the measuring head of the displacement meter, detecting the position of the automatic guided vehicle in the factory, and the like. It may be used.

3, 8 ... Displacement detection device 21 ... XY stage (object to be measured)
DESCRIPTION OF SYMBOLS 31 ... Retroreflector 32 ... Light source part 33 ... Beam splitter 34 ... Light receiving part 35 ... Condensing part 63 ... Probe (measurement object)
L1 ... Irradiation light

Claims (5)

A retroreflector provided on the object to be measured;
A light source unit that emits irradiation light that can irradiate a predetermined range toward the retroreflector, and
A beam splitter that is provided between the retroreflector and the light source unit, transmits the irradiation light, and reflects the light reflected by the retroreflector;
A displacement detection apparatus comprising: a light receiving unit that receives light reflected by the beam splitter. A retroreflector provided on the object to be measured;
A light source unit that emits irradiation light that can irradiate a predetermined range;
A beam splitter that is provided on the emission side of the irradiation light with respect to the light source unit, reflects the irradiation light to enter the retroreflector, and transmits the light reflected by the retroreflector;
A displacement detection device comprising: a light receiving portion that receives light transmitted through the beam splitter. In the displacement detection device according to claim 1 or 2,
A displacement detection device, comprising: a condensing unit that is provided between the beam splitter and the light receiving unit and condenses light from the beam splitter. Towards a retroreflector provided on the object to be measured, emits irradiation light that can irradiate a predetermined range from the light source unit,
The beam splitter provided between the retroreflector and the light source unit transmits the irradiation light, reflects the light reflected by the retroreflector, and reflects the light reflected by the beam splitter. Is received by the light receiver,
A displacement detection method for detecting a displacement of the object to be measured based on a light receiving position at the light receiving unit. Towards a retroreflector provided on the object to be measured, emits irradiation light that can irradiate a predetermined range from the light source unit,
A beam splitter provided on the emission side of the irradiation light with respect to the light source unit reflects the irradiation light to be incident on the retroreflector and transmits light reflected by the retroreflector. The light transmitted through this beam splitter is received by the light receiving unit,
A displacement detection method for detecting a displacement of the object to be measured based on a light receiving position at the light receiving unit.

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