JP2003322551A - Displacement detecting device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a displacement detecting device superior in stability with the lapse of time while coping with an angle change in a diffraction grating, and while miniaturizing the device regardless of the kind of light source. <P>SOLUTION: This displacement detecting device is characterized by having the light source 51 for emitting the light, a polarized light separating part 58 for emitting the light by separating the light emitted from the light source 51 into the two light mutually different in a polarized light component, a first lens 41a arranged between the light source 51 and the polarized light separating part 58, a reflection optical system 14 for respectively reflecting the two first diffracted light obtained by diffracting the two light emitted from the polarized light separating part 58 by the diffraction grating 11, a light branching part 44 for dividing the synthetic light into a plurality by generating the synthetic light by synthesizing the two second diffracted light obtained by diffracting the first diffracted light reflected by the reflection optical system 14 by the diffraction grating 11, a polarized light part 42 for respectively passing only a prescribed polarized light component on the divided synthetic light, a light receiving element 52 for generating an interference signal by respectively photoelectrically transducing the interference light passing through the polarized light part 42, and a second lens 41 arranged between the polarized light part 42 and the light receiving element 52. <P>COPYRIGHT: (C)2004,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a combined light emitting and receiving unit for detecting a relative movement position in a movable part of a machine tool, a semiconductor manufacturing apparatus or the like, a manufacturing method thereof, and a displacement detecting apparatus.

[0002]

2. Description of the Related Art Conventionally, an optical displacement detection device using a diffraction grating has been known as a device for detecting a relative movement position in a movable part such as a machine tool or a semiconductor manufacturing device.

For example, a conventional optical displacement measuring device proposed in Japanese Patent Application Laid-Open No. 60-98302 is shown in FIGS. 14 and 15. FIG. 14 is a perspective view schematically showing the conventional optical displacement measuring device 100, and FIG. 15 is a side view schematically showing the conventional optical displacement measuring device 100.

A conventional optical displacement measuring apparatus 100 includes a diffraction grating 101 that linearly moves in the directions of arrows X1 and X2 in the figure with the movement of a movable part such as a machine tool, a light source 102 that emits light, and a light source 102. A half mirror 103 that splits the light emitted from the two beams into two beams and causes the two diffracted lights from the diffraction grating 101 to overlap and interfere with each other;
Two mirrors 104a and 104b that reflect the diffracted light diffracted by the diffraction grating 101, and a photodetector 105 that photoelectrically converts the two interfering diffracted lights to generate an interference signal.
It has and.

The light emitted from the light source 102 is split into two beams by the half mirror 103. The two beams are applied to the diffraction grating 101, respectively. The two beams with which the diffraction grating 101 is irradiated are diffracted by the diffraction grating 101 and become diffracted light (hereinafter, this diffracted light is referred to as once diffracted light). The one-time diffracted light is reflected by the mirrors 104a and 104b, respectively. Mirror 104
The one-time diffracted light reflected by a and 104b is again irradiated on the diffraction grating 101 and diffracted again (hereinafter, this re-diffracted light is referred to as twice-diffracted light). These two
The two-time diffracted light of the book passes through the same optical path and is reflected by the half mirror 10.
The light enters the photodetector 105, and they are superposed on each other and interfere with each other, and the photodetector 105 is irradiated with the light.

Such a conventional optical displacement measuring device 10
At 0, the displacement of the diffraction grating 101 in the directions of arrows X1 and X2 in the drawing can be detected. That is, in the optical displacement measuring apparatus 100, a phase difference is generated between the two double-diffracted lights based on the diffraction grating 101 according to the movement of the diffraction grating 101. Therefore, in this optical displacement measuring apparatus 100, the moving position of the movable part of the machine tool or the like can be measured by detecting the phase difference between the two twice-diffracted lights from the interference signal obtained by the photodetector. .

Further, another conventional optical displacement measuring device proposed in Japanese Patent Laid-Open No. 60-98302 is shown in FIGS. 16 and 17. FIG. 16 is a perspective view schematically showing a conventional optical displacement measuring device 110, and FIG. 17 is a side view schematically showing the conventional optical displacement measuring device 110.

The conventional optical displacement measuring device 110 has a diffraction grating 111 that linearly moves in the directions of arrows X1 and X2 in the figure with the movement of a movable part such as a machine tool, a light source 112 that emits light, and a light source 112. The half mirror 113 that splits the light emitted from the two beams into two beams and causes the two diffracted lights from the diffraction grating 111 to overlap and interfere with each other.
And two first beams for irradiating the two beams divided by the half mirror 113 to the same position on the diffraction grating 111.
Mirrors 114a and 114b, and two second mirrors 115a that reflect the diffracted light diffracted by the diffraction grating 111,
115b and a photodetector 116 that receives two diffracted lights that interfere and generates an interference signal.

The light emitted from the light source 112 is split into two beams by the half mirror 113. These two beams are respectively reflected by the first mirrors 114a and 114b.
It is reflected by the laser beam and is irradiated onto the same position on the diffraction grating 111. The two beams with which the diffraction grating 111 is irradiated are diffracted by the diffraction grating 111, respectively, and become one-time diffracted light. The one-time diffracted light is transmitted to the second mirrors 115a and 1a, respectively.
It is reflected by 15b. The once-diffracted light is again irradiated onto the diffraction grating 111 and diffracted to become twice-diffracted light. These two two-time diffracted lights are incident on the half mirror 113 through the same optical path, and are superposed and interfere with each other, and are irradiated on the photodetector 116.

Such a conventional optical displacement measuring device 11
At 0, the displacement of the diffraction grating 111 in the directions of the arrows X1 and X2 in the figure can be detected. That is, in the optical displacement measuring device 110, a phase difference occurs between the two double-diffracted lights based on the diffraction grating 111 according to the movement of the diffraction grating 111. Therefore, in the optical displacement measuring device 110, the moving position of the movable part of the machine tool or the like can be measured by detecting the phase difference between the two twice-diffracted lights from the interference signal obtained by the photodetector 116. .

By the way, if there is a difference in the optical path lengths of the two beams split by the above-mentioned half mirror 113, a phase change occurs in the interference signal, which causes a measurement error. Therefore, in order to exhibit desired characteristics in the optical displacement measuring devices 100 and 110, it is necessary to adjust the optical path lengths of the above-described two split beams to be equal.

FIG. 18 shows a conventional optical displacement measuring device proposed in Japanese Patent Laid-Open No. 61-83911, which can be adjusted so that the optical path lengths of the divided beams are made equal.

This conventional optical displacement measuring device 120 is
With the movement of movable parts such as machine tools, arrow X1 in the figure
And a light source 122 including a diffraction grating 121 that linearly moves in the X2 direction and a multimode semiconductor laser that emits light.
A half mirror 123 for splitting the light emitted from the light source 122 into two beams and for superimposing and interfering two diffracted lights from the diffraction grating 121; and the diffraction grating 12
Two mirrors 124 that reflect the diffracted light diffracted by 1.
a, 124b, a half mirror 125 for separating interfering diffracted light, and photodetectors 126a, 126b for photoelectrically converting the diffracted light to generate interference signals.

The light emitted from the light source 122 is split into two beams by the half mirror 123. The two beams are projected onto the diffraction grating 121. The two beams with which the diffraction grating 111 is irradiated are generated by the diffraction grating 12
Each is diffracted by 1 and becomes one-time diffracted light. The once diffracted light is reflected by the mirrors 124a and 124b, respectively. The once-diffracted light is again irradiated to the diffraction grating 121 and diffracted to become twice-diffracted light. These two double-diffracted lights are incident on the half mirror 123 through the same optical path, overlapped and interfere with each other, and are applied to the photodetectors 126a and 126b via the half mirror 125.

Such a conventional optical displacement measuring device 12
At 0, by using a multimode semiconductor laser as a light source, it is possible to detect the displacement of the diffraction grating 121 in the directions of the arrows X1 and X2 while controlling the optical path length of the divided beams. That is, since the optical displacement measuring device 120 can detect the difference in the optical path lengths, the optical path lengths can be adjusted with high accuracy, and the adjustment state can be monitored. Therefore, the error based on the wavelength variation can be easily identified. can do.

By the way, the above-mentioned optical displacement measuring device 1
14 and 17, it is difficult to detect the position in the case of the rotational movement in the arrow A1 and arrow A2 directions or the rotational movement in the arrow B1 and arrow B2 directions in FIGS. In order to prevent the influence of such an angular fluctuation of the diffraction grating, an optical displacement measuring device is further proposed, for example, in Japanese Patent Laid-Open No. 2000-81308.

This conventional optical displacement measuring device 130 is
As shown in FIG. 19, a diffraction grating 131 that is attached to a movable part of a machine tool or the like and moves linearly, a light source 132 that emits light, and two interfering two-time diffracted lights Lc1 and Lc2 are received to generate an interference signal. A light-receiving element 133 to be generated, a position detector 134 for detecting a moving position from the diffraction grating 131 based on an interference signal from the light-receiving element 133, and a light source 132.
The light La emitted from the laser beam is split into two beams La1 and La2, which are applied to the diffraction grating 131 and
The irradiation / reception optical system 135 that interferes the two-time diffracted lights Lc1 and Lc2 from 31 to irradiate the light-receiving element 133, and the two one-time diffracted lights Lb1 and Lb2 from the diffraction grating 131 are reflected to the diffraction grating 131 again. And a reflection optical system 136 for irradiating.

The irradiation / light reception optical system 135 forms a first image forming element 141 for forming an image of the light La emitted from the light source 132 on the grating surface of the diffraction grating 131, and the light L emitted from the light source.
a is divided into two beams La1 and La2, and
The two double-diffracted lights from the diffraction grating 131 are Lc1 and Lc.
The half mirror 142 that overlaps two and interferes with each other, the reflector 143 that reflects the lights La1 and La2 separated by the half mirror 142 and the two-time diffracted lights Lc1 and Lc2, and the half mirror 142 are overlapped with each other. The two double-diffracted lights Lc1 and Lc2 receive the light receiving element 13
The second imaging element 144 for forming an image on the light receiving surface of No. 3 is provided.

The reflection optical system 136 reflects the one-time diffracted lights Lb1 and Lb2 generated by the lights La1 and La2 and irradiates the diffraction grating 131 again with the reflector 146, and the lights La1 and L1.
The third imaging element 14 that irradiates the reflector 146 with the once-diffracted light Lb1 and Lb2 generated by La2 as parallel light.
8 and.

The optical displacement measuring device 1 having the above-mentioned configuration
In 30, the diffraction grating 131 is moved to the X-axis according to the movement of the movable part.
By moving in one direction or X2 direction, two 2
A phase difference occurs between the diffracted lights Lc1 and Lc2. In this optical displacement measuring device 130, two two-time diffracted lights Lc1 and Lc
The interference signal is detected by causing c2 to interfere with each other, the phase difference between the two twice-diffracted lights Lc1 and Lc2 is obtained from the interference signal, and the moving position of the diffraction grating 131 is detected.

Further, in this optical displacement measuring device 130,
The light La emitted from the light source 132 is supplied to the first imaging element 141.
Is imaged on the grating surface of the diffraction grating 131, and
The third imaging element 138 causes the respective one-time diffracted light Lb
The parallel light of 1 and Lb2 is always radiated perpendicularly to each reflector 146. Therefore, even if the optical axes of the first-order diffracted lights Lb1 and Lb2 reflected by the reflector 146 are deviated, the first-order diffracted lights Lb1 and Lb2 always travel in the same optical path as when they were incident and are on the grating surface of the diffraction grating 131. It is incident on the same incident point. Therefore, in this optical displacement measuring device 130, even when the diffraction grating 131 is tilted, the twice-diffracted light Lc1,
Lc2 always passes through the same optical path as that at the time of incidence. Also, there is no change in the optical path length.

[0022]

However, in the optical displacement measuring device 120 using a multimode semiconductor laser as a light source, which is proposed in Japanese Patent Laid-Open No. 61-83911, the optical path length is changed with respect to the wavelength fluctuation of the light source. Although it can be controlled and eventually stable characteristics can be obtained, there is a problem that a general semiconductor laser cannot be used. Also, this optical displacement measuring device 12
At 0, it is not possible to cope with the angular fluctuation of the diffraction grating,
There is a problem that the allowable error is restricted not only when actually mounting each component constituting the device but also when mounting the diffraction grating to the movable portion.

The optical displacement measuring device 130 proposed in Japanese Patent Application Laid-Open No. 2000-81308, which reduces the influence of the angular fluctuation of the diffraction grating, is an imaging element such as a lens for realizing the angle adjustment of the optical path. Since it is necessary to use a child, there is a problem that the configuration of the device becomes complicated.
Further, since the optical displacement measuring device 130 uses individual components such as a lens and a half mirror, it lacks stability over time and is a major obstacle to downsizing the entire device.

Therefore, the present invention has been devised in view of the above-mentioned problems, and it is possible to cope with the angle variation of the diffraction grating regardless of the kind of the light source and to reduce the size of the device over time. It is an object of the present invention to provide a displacement detection device having excellent stability.

[0025]

DISCLOSURE OF THE INVENTION In order to solve the above-mentioned problems, a displacement detecting apparatus according to the present invention detects a displacement in a grating vector direction of an object to be inspected having a diffraction grating based on an interference signal. In the displacement detecting device, a light source that emits light, a beam splitter that splits the light emitted from the light source into two lights, and emits the light, and a first lens disposed between the light source and the beam splitter. A reflecting means for reflecting the two first diffracted lights obtained by diffracting the two lights emitted from the beam splitter by the diffraction grating, and the first diffracted light reflected by the reflecting means. Is combined with two second diffracted light beams obtained by being diffracted by the diffraction grating to generate combined light, and the light dividing means for dividing the combined light into a plurality of light beams is divided into a predetermined number. A polarizing means for transmitting only a polarized component, a light receiving means for photoelectrically converting the interference light transmitted through the polarizing means to generate the interference signal, and a second lens arranged between the polarizing means and the light receiving means. And is provided.

[0026]

DESCRIPTION OF THE PREFERRED EMBODIMENTS A displacement detecting device to which the present invention is applied will be described. As shown in FIG. 1, the displacement detection device 10 according to the present invention includes a transmission type diffraction grating 11 which is attached to a movable part of a machine tool or the like and moves linearly, and two lights La1, which emit light emitted by a light emitting element. Two double-diffracted lights L which are separated into La2, are emitted, and are diffracted by the diffraction grating 11.
The light emitting and receiving composite unit 12 that interferes c1 and Lc2 with each other to detect an interference signal, and the two lights La1 and La2 emitted from the light receiving and emitting composite unit 12 are applied to the diffraction grating 11, and the light from the diffraction grating 11 is emitted. Reflective optics for reflecting two double-diffracted lights Lc1, Lc2 to the light-receiving / combining unit 12 and two single-diffracted lights Lb1, Lb2 from the diffraction grating 11 and irradiating the diffraction grating 11 again. System 14 and.

As shown in FIG. 2, the diffraction grating 11 has, for example, a thin plate shape, and a narrow slit, a groove or the like, or a grating having a distributed refractive index is formed at a predetermined interval on the surface or inside thereof. It is carved. The light incident on such a diffraction grating 11 is diffracted by a slit or the like carved on the surface,
The light passes through the diffraction grating 11. Diffracted light generated by diffraction is generated in the direction determined by the grating interval and the wavelength of light. Further, the diffraction grating 11 may be formed on the bonding surface of a scale (not shown) formed by bonding glass.

In describing the embodiments of the present invention, the surface of the diffraction grating 11 on which the grating is formed is referred to as a grating surface 11a. Further, the direction of the diffraction grating 11 in which the grating is formed (directions of arrows C1 and C2 in FIG. 2), that is, perpendicular to the grating vector indicating the direction of change in transmittance and reflectance of the grating, depth of the groove, and the like Direction and the lattice plane 11a
The direction parallel to is called the lattice direction. A direction perpendicular to the direction in which the grating is formed and parallel to the grating surface 11a (directions of arrows D1 and D2 in FIG. 2), that is, the diffraction grating 1
A direction parallel to one grid vector is called a grid vector direction. The normal direction of the diffraction grating 11 is set to E1, E
There are two directions.

The diffraction grating 11 is attached to a movable part of a machine tool or the like, and moves along with the movement of the movable part in the directions of arrows D1 and D2 in FIG. 2, that is, in the grating vector direction.

In the present invention, the type of the diffraction grating is not limited, and not only those in which the grooves and the like are mechanically formed as described above but also those in which interference fringes are printed on a photosensitive resin are prepared. It may be.

The reflecting member 13a reflects the light La1 and irradiates it at a predetermined position on the grating surface 11a of the diffraction grating 11. The light La1 is diffracted by the diffraction grating 11 to obtain the once-diffracted light Lb1. The reflecting member 13b receives the light L
It reflects a2 and irradiates it at a predetermined position on the grating surface 11a of the diffraction grating 11. The light La2 is diffracted by the diffraction grating 11 to obtain the once-diffracted light Lb2. It is desirable that the incident angles of the light La1 and the light La2 incident on the diffraction grating 11 are equal.

The reflecting member 13a has a single diffracted light Lb.
2 caused by diffraction of 1 by the diffraction grating 11
The diffracted light Lc1 is emitted. The reflecting member 13a reflects the twice-diffracted light Lc1 and irradiates the combined light-receiving and emitting unit 12 with it. Further, the reflecting member 13b has one-time diffracted light Lb2.
Is diffracted by the diffraction grating 11 to be irradiated with the double-diffracted light Lc2. The reflection member 13b is
The diffracted light Lc2 is reflected and irradiated to the light emitting / receiving composite unit 12.

By the way, a predetermined position for irradiating the grating surface 11a of the diffraction grating 11 by the reflecting member 13a and a predetermined position for irradiating the grating surface 11a of the diffraction grating 11 by the reflecting member 13b may be brought close to each other. As a result, it is possible to reduce the difference in optical path length caused by unevenness in the thickness of the diffraction grating 11 and reduce errors due to uneven thickness of the scale.

The reflection optical system 14 includes a reflector 26 that reflects the once-diffracted light Lb1 and irradiates the diffraction grating 11 again, and a reflector 27 that reflects the once-diffracted light Lb2 and irradiates the diffraction grating 11 again. 1 / Changing the polarization state of the diffracted light Lb1 1 /
It has a four-wave plate WP1 and a quarter-wave plate WP2 that changes the polarization state of the once-diffracted light Lb2. The quarter-wave plates WP1 and WP2 may be, for example, film-shaped with the optical axis inclined by 45 °.

The reflector 26 is irradiated with one-time diffracted light Lb1 which has passed through the quarter-wave plate WP1. The reflector 26 is
The one-time diffracted light Lb1 is reflected vertically so that the one-time diffracted light Lb1 travels back in the same path as the incident path. By the way, the one-time diffracted light Lb1 emitted to the reflector 26 is
The one-time diffracted light Lb1 that has already passed through the quarter-wave plate WP1 and is reflected by the reflector 26 is the quarter-wave plate WP1.
Since the light passes through 1 again, the diffraction grating 11 is irradiated again with the polarization direction rotated by 90 °.

The reflector 27 is irradiated with one-time diffracted light Lb2 that has passed through the quarter-wave plate WP2. The reflector 27 is
The one-time diffracted light Lb2 is reflected vertically so that the one-time diffracted light Lb2 goes backward in the same path as the incident path. By the way, the one-time diffracted light Lb2 with which the reflector 27 is irradiated is
The one-time diffracted light Lb2 that has already passed through the quarter-wave plate WP2 and is reflected by the reflector 27 is the quarter-wave plate WP.
Since the light passes through 2 again, the diffraction grating 11 is irradiated again with the polarization direction rotated by 90 °.

The reflective optical system 14 is not limited to the above-mentioned structure, but may be composed of a reflective prism, for example. FIG. 3 shows a configuration of the displacement detection device 10 using a reflection prism in the reflection optical system 14.
In FIG. 3, description of the same components and members as in FIG. 1 will be omitted.

The reflecting prism 30 includes a quarter-wave plate WP.
31 are stacked. The optical axis of the quarter-wave plate WP31 is inclined by 45 ° with respect to the polarization direction of incident light. The reflecting surface 30a of the reflecting prism 30 is irradiated with the one-time diffracted lights Lb1 and Lb2 that have passed through the quarter-wave plate WP31. The reflecting surface 30a receives the one-time diffracted lights Lb1 and Lb2.
Reflects the one-time diffracted lights Lb1 and Lb2 vertically so that the light travels in the same path as the incident path. By the way. The one-time diffracted lights Lb1 and Lb2 irradiated on the reflecting surface 30a are
The one-time diffracted lights Lb1 and Lb2 which have already passed through the quarter-wave plate WP31 and which are reflected by the reflecting surface 30a are 1
Since it passes through the / 4 wave plate WP31 again, the polarization direction is 9
In the state rotated by 0 °, the diffraction grating 11 is irradiated again.

Next, details of the combined light emitting and receiving unit 12 will be described. As shown in FIG. 4, the light emitting / receiving composite unit 12 includes a housing member 40 for housing a light emitting element and a light receiving element.
And a plurality of lenses (41a, 41_1, 41_2, 41
_3, 41_4), and a polarization unit 42 (42_1, 42_1) that transmits only a predetermined polarization component.
_2, 42_3, 42_4), a phase plate 43 that changes the polarization state of light, and the light that illuminates the diffraction grating 11 is divided or obtained by diffracting the diffraction grating 11.
Synthetic lights Ld1 and L by combining the diffracted lights Lc1 and Lc2
and an optical branching unit 44 for separating into D2, Ld3, and Ld4.

The housing member 40 is a light source 5 for emitting the light La.
1 and a light receiving element 52 (52_1, 52_2, 52_3, 52 that photoelectrically converts interference light described below to generate an interference signal).
_4) and the semiconductor substrate 5 for installing the light source 51 to apply an electric signal or to control the optical path by the reflecting surface 53a.
3 and a semiconductor substrate 54 for installing a light receiving element and extracting an electric signal.

The light source 51 is an element that emits coherent light such as laser light. The light source 51 may be, for example, a multimode semiconductor laser that emits laser light having a small coherence length. Further, the polarization direction of the light source 51 is arranged so as to be parallel or perpendicular to the straight line AA shown in FIG.

The light receiving element 52 is a photoelectric conversion element for converting the light applied to the light receiving surface into an electric signal corresponding to the amount of light, and is composed of, for example, a photo detector. The light receiving element 52 receives each of the interference lights Ld1, Ld2, Ld3, and Ld4 with which the light receiving surface is irradiated,
An interference signal corresponding to the light quantity is generated.

The interference signal obtained by photoelectric conversion by the light receiving element 52 is detected by a position detector (not shown) via the semiconductor substrate 54. The position detector (not shown) obtains a phase difference based on the obtained interference signal and outputs a position signal indicating the relative movement position of the diffraction grating 11.

The compound lens section 41 is composed of an optical element such as a lens having a predetermined numerical aperture. Lens 41
The light La emitted from the light source 51 is incident on a.
The lens 41a can image the incident light La on the grating surface 11a of the diffraction grating 11 and the reflectors 26 and 27 with a predetermined beam diameter. In the present invention, the emitted light La is normally imaged on the reflectors 26 and 27. For this reason,
The diameter of the beam irradiated on the lattice surface 11a can be increased, and the influence of dust and scratches on the lattice surface 11a can be reduced. Further, by arranging the compound lens portion 41 for controlling the beam diameters of the light emitted to the outside and the light received as described above in the same package, the degree of integration can be increased and the manufacturing process can be simplified. ,
The reliability of the entire device can be improved.

Further, the lenses 41_1, 41_2, 41_
3 and 41_4 include the interference light L emitted from the polarization unit 42.
d1, Ld2, Ld3, and Ld4 are incident, respectively. The lenses 41_1, 41_2, 41_3, 41_4 form the incident interference lights Ld1, Ld2, Ld3, Ld4 on the light receiving elements 52_1, 52_2, 52_3, 52_4. The image forming point does not necessarily have to be the point where the beam diameter is minimum, and for example, the point where the difference in optical path length within the image of the beam is minimum may be located on the light receiving surface.

That is, these lenses 41a and 41_
1, 41_2, 41_3, 41_4 can set the convergence position of the emitted light, respectively. Further, the compound lens portion 41 is not limited to the structure in which a plurality of lenses are connected as described above, and for example, the above-mentioned lenses may be integrated into one lens. Further, each of the lenses that form the compound lens unit 41 is not only for converging a beam, but also for emitting parallel light,
Alternatively, divergent light may be emitted.

Polarizers 42_1, 42_2, 42_3, 4
2_4 is the combined light Ld1 incident from the phase plate 43,
Only predetermined polarization components of Ld2, Ld3, and Ld4 are transmitted, and the interference lights Ld1, Ld2, Ld3, and Ld4 are emitted to the lens unit 41. Incidentally, each combined light Ld incident on each polarization unit 42 is a linearly polarized light whose polarization direction changes with the movement of the diffraction grating 11. 9 from this synthetic light Ld
In order to obtain intensity signals having different phases by 0 °, each polarization unit 4
2 is a 45 ° interval (eg 5 °, 50 °, 95 °, 140
It is sufficient if it is arranged at (°), and it can be arranged without being restricted by the posture at the time of attaching the polarization part 42.
It should be noted that by providing such a polarization section 42 between the phase plate 43 and the compound lens section 41, there is also an advantage that the entire unit can be made compact.

The phase plate 43 includes a polarizing section 42 and a light branching section 4
4 are stacked so as to be sandwiched between them. This phase plate 4
Reference numeral 3 is, for example, a quarter-wave plate and performs conversion between circularly polarized light and linearly polarized light. Incidentally, the phase plate 43 may be constituted by a film-shaped quarter-wave plate inclined at 45 ° with respect to the straight line AA shown in FIG.
The light La enters through a. The phase plate 43 converts the light La, which is, for example, linearly polarized light, into circularly polarized light and converts the light La into polarized light.
Irradiate to 8. Further, the phase plate 43 receives the combined lights Ld1, Ld2, Ld3, and Ld4 emitted from the light branching unit 44, converts them into circularly polarized light, and outputs the circularly polarized light to the above-described polarizing unit 42.
That is, a configuration is adopted in which the conversion of the polarization state of the light La from the light source 51 and the conversion of the polarization state of the light Ld from the light branching film 59 are shared by one phase plate 43. The combined light emitting and receiving unit 12 can also be applied to a configuration in which the phase plate 43 is omitted.

The light branching unit 44 divides the light La emitted from the light source 51 into two lights La1 and La2 and emits the light La, and the double diffracted light Lc from the reflecting members 13a and 13b.
1, a polarization splitting unit 58 that synthesizes Lc2 to generate a synthetic light Ld, and light splitting films 59_1 and 59_2 that split the synthetic light Ld emitted from the polarization splitting unit 58 into synthetic lights Ld1, Ld2, Ld3, and Ld4. 59_3 and 59_4.

The polarization separation section 58 is composed of, for example, a polarization beam splitter or the like, and the light La emitted from the light source 51 enters through the phase plate 43. The polarized light separating section 58 is
A part of the incident light La is reflected to generate light La1,
A part of the incident light La is transmitted to generate the light La2. The polarization splitting unit 58 converts the light La1 and La2 into
It may be divided into S-polarized light and P-polarized light whose polarization components are orthogonal to each other.
In this case, the light La1 becomes S-polarized light and light La2.
Is P-polarized light. In addition, the polarization separation section 58 has
Two-time diffracted light Lc1 and two-time diffracted light L from the diffraction grating 11
c2 is incident. The polarization beam splitting unit 58 superimposes and synthesizes two two-time diffracted lights Lc1 and Lc2, and the combined light L
The d is emitted to the light branching film 59.

Light branching films 59_1, 59_2, 59_3,
The reflectances of 59_4 are 1/4, 1/3, 1/2, and
It is set to 1 (that is, the light branching film 59_4 is a total reflection surface). Therefore, the incident combined light L
When d is almost the same light amount, the combined lights Ld1, Ld2, Ld3,
It becomes possible to divide into Ld4.

The receiving / emitting composite unit 12 includes the above-mentioned housing member 40, the composite lens section 41, and the polarization section 42.
The phase plate 43 and the light branching section 44 are arranged in the same package and configured as an independent unit. Further, each of these members is configured to be laminated and integrated.

That is, in the combined light emitting and receiving unit 12, by packaging each member into an integrated structure, precise position adjustment is facilitated, and it is not necessary to take a large space for arranging parts, and the displacement detecting apparatus as a whole is Miniaturization,
The weight can be reduced. Further, by accommodating each member in the same accommodating member, it is possible to reduce the influence of environmental changes and changes over time, and it is possible to minimize misalignment during adjustment and the like, and consequently the light emitting and receiving combined unit 12 The overall reliability can be increased.

Next, an operation example of the displacement detecting device 10 to which the present invention is applied will be described.

First, the light La emitted from the light source 51 is reflected by the reflecting surface 53a of the semiconductor substrate 53 and is applied to the lens 41a as shown in FIG. Light La is
The image is converted by the lens 41a and is irradiated on the phase plate 43, which is, for example, a quarter-wave plate.

The light La radiated to the phase plate 43 is changed into circularly polarized light by the phase plate 43.

The light La emitted from the phase plate 43 is, for example, S-polarized and P-polarized light La1 and La by the polarization splitting unit 58.
It is separated into two and is incident on the diffraction grating 11 via the reflecting members 13a and 13b. By the way, the incident angle of the light La1 on the diffraction grating 11 is θa, and the incident angle of the light La2 is θb.
In addition, the diffraction angle of the one-time diffracted light Lb1 is θa ′, and the one-time diffracted light L
When the diffraction angle of b2 is θb ′, the following equation (11),
(12) is established. sin θa + sin θa ′ = mλ / d (11) sin θb + sin θb ′ = mλ / d (12) d: Diffraction grating pitch λ: Light wavelength m: Diffraction order By the way, a volume phase hologram is used for the diffraction grating 11 to perform Bragg diffraction. When using, θa = θa ', θ
The incident angle is such that b = θb ′. Diffraction grating 1
When the volume type phase hologram is not used for 1, the incident angle and the diffraction angle are arbitrary angles shown by the above-mentioned relationship.

The once diffracted lights Lb1 and Lb2 are reflected vertically by the reflectors 26 and 27, respectively. At this time, the one-time diffracted lights Lb1 and Lb2 pass through the ¼ wavelength plates WP1 and WP2.
The polarization directions are rotated by 90 ° for each pass. Therefore, the one-time diffracted light Lb1 that was originally S-polarized is converted into P-polarized light, and the one-time diffracted light Lb2 that was originally P-polarized is converted into S-polarized light.

Next, the reflectors 26 and 27 are reflected by 1
The diffracted light beams Lb1 and Lb2 are diffracted again by the diffraction grating 11 to become diffracted light beams Lc1 and Lc2 twice, and reach the polarization splitting unit 58 again through the same optical path. The diffraction orders of the two-time diffracted lights Lc1 and Lc2 may be of the same order, and are not limited to the cases of the same order. Polarization separation unit 58
Then, the P-polarized 2-fold diffracted light Lc1 and the S-polarized 2-fold diffracted light Lc2 are overlapped and combined to generate a combined light Ld.

The combined light Ld is converted into the light branching films 59_1 and 59_.
2, 59_3, 59_4 through Ld1, Ld2, Ld
It is divided into 3 and Ld4. This divided synthetic light Ld1,
The phase plate 43 is irradiated with Ld2, Ld3, and Ld4, respectively. At this time, the two-time diffracted lights Lc1 and Lc2 are circularly polarized lights having mutually opposite directions. When this combined light Ld is received through a polarizing plate that transmits only a specific polarization component, this combined light Ld
The two two-time diffracted lights Lc1 and Lc
The amplitude of 2 is A1, A2, the moving amount of the diffraction grating 11 in the direction of the grating vector is x, the initial phase is δ, and K = 2.
Assuming that π / d (d is the grating pitch), if the first-order diffracted light is used in the first and second diffractions, if a specific polarization component is extracted, the interference signal I as in the following equation (13) is obtained. Is obtained. I = A1 ² + A2 ² + 2 · A1 · A2 cos (4 · K · x + δ) (13) This interference signal I changes by one period when the diffraction grating 11 moves d / 4 in the grating vector direction. δ is an amount that depends on the difference between the optical path lengths of the two two-time diffracted lights Lc1 and Lc2 that are superposed.

Each composite light Ld emitted from this phase plate 43
1, Ld2, Ld3, and Ld4 are transmitted by the polarization unit 42, respectively, so that only predetermined polarization components are transmitted. Each polarization unit 42
Are set to have an interval of 45 °, respectively, but in this example, the polarization unit 42_1 transmits only the polarization direction of 0 °, and the polarization unit 42_2 transmits only the polarization direction of 45 °. , And the polarization part 42_3 is 90 °
And transmits only the polarization direction of
_4 transmits only the polarization direction of 135 °. At this time, the interference lights Ld1 and Ld transmitted through the respective polarization parts 42
The intensities of d2, Ld3, and Ld4 are calculated by the following equation (21).
It is represented by (24). B + Acos (4 ・ K ・ x + δ °) (21) B + Acos (4 ・ K ・ x + 90 ° + δ) (22) B + Acos (4 ・ K ・ x + 180 ° + δ) (23) B + Acos (4 ・ K ・ x + 270 ° + δ) (24) B = 1/4 (A1 ² + A2 ² ) A = 1/2 · A1 · A2 Formula (21) is defined as interference light Ld1 transmitted through the polarization unit 42_1.
Is a formula expressing the intensity of the polarization part 42_.
2 is an expression that represents the intensity of the interference light Ld2 that has passed through 2, Formula (23) is an expression that represents the intensity of the interference light Ld3 that has transmitted through the polarization unit 42_3, and Formula (24) is an expression that represents the polarization unit 42_4.
3 is an expression representing the intensity of the interference light Ld4 that has passed through. The interference light Ld1 represented by these equations is generated by the lenses 41_1 and 4_1.
1_2, 41_3, 41_4, through the light receiving element 52_
Images are formed on 1, 52_2, 52_3, 52_4. That is, each light-receiving element 52 receives the interference light Ld represented by the above equation.
Will be photoelectrically converted to generate an interference signal.

Subtracting equations (21) and (23),
The DC component of the interference signal can be removed. Further, by subtracting the equations (22) and (24), the DC component of the interference signal can be removed. The subtracted signal is
Since the phases are different from each other by 90 °, it is possible to obtain a signal for detecting the moving direction in the diffraction grating.

Further, in the present invention, as the reflection optical system 14,
The reflection prism 30 can also be applied as described above.
Therefore, dust is not mixed into the reflecting surface 30a on which the beam is imaged, and no scratches are formed on the reflecting surface 30a, so that the displacement can be detected with higher accuracy.

The present invention is not limited to the above embodiment. For example, the following configuration capable of reducing the error due to the wavelength variation of the light source 51 can be applied.

When the wavelength of the light source fluctuates, the optical path length from the polarization splitting unit 58 to the reflector 26 and the polarization splitting unit 58.
If there is a difference in the optical path length from the reflector to the reflector 27 (hereinafter, this optical path length difference is referred to as ΔL), a measurement error occurs. The error amount E can be expressed as follows. E = Δλ / λ · 2 · ΔL · 4 / d (45) λ: wavelength of the light source 51 Δλ: variation amount of wavelength ΔL: optical path difference d between two lights separated by the polarization separation unit 58: diffraction grating 11 At this time, it is necessary to reduce ΔL so that the error amount E falls within the allowable range with respect to the expected wavelength variation Δλ. The lens 41a and the lenses 41_1, 41_2,
41_3 and 41_4 are set so that the light emitted respectively converges on a specific point (including a virtual image point, infinity is impossible). In the present embodiment, since the light split into two by the polarization splitting unit 58 passes through the same lens 41a, the distance between each convergence point and the light source 51 that is the light emitting point becomes equal. By the way, when individual lenses are used for each of the two light beams separated in the polarization beam splitting unit, lenses having the same focal length and the same shape are used to make the distances equal.

At this time, the tendency of the light Ld near the light receiving element 52 is shown in FIG. In FIG. 6, d is the shift amount of the convergence positions of the two lights. Of the two lights, the solid line is the light flux based on the twice-diffracted light Lc1, and the broken line is the twice-diffracted light Lc1.
When the luminous flux is based on c2, d = 0 only when the optical path lengths of the two are equal, and the two luminous fluxes overlap. Further, when the optical path lengths of the two lights are different, d ≠ 0
Then, concentric interference fringes are generated and the intensity of the interference signal is reduced. Therefore, maximize the interfering signal, or
Alternatively, by adjusting the positions of the reflectors 26, 27 (30a) so that the interference image becomes a null fringe, the optical path lengths of the two lights are made equal regardless of the coherence length of the light source 51. You can

If the optical path lengths can be made equal, the measurement error can be reduced by the above equation (45) even if the wavelength of the light source varies.

Further, in the present invention, each lens in the compound lens section 41 may be adjusted as follows.

FIG. 7A shows the positional relationship between the light emitting point of the light source 51 and the reflectors 26 and 27 (reflection surface 30a). Further, FIG. 7B shows reflectors 26 and 27 (reflecting surface 30
The positional relationship between a) and the light receiving element 52 is shown. The lens 41a and the lenses 41_1, 41_2, 41_3, 41
_4 and _4 are set so as to satisfy the following geometrical optics imaging relationship. 1 / LO + 1 / LO '= 1 / FO (31) 1 / LR + 1 / LR' = 1 / FR (32) FO: Focal length of lens 41a FR: Focal length of lenses 41_1, 41_2, 41_3, 41_4 LO, LO ', LR, and LR' are geometrical optical distances and indicate distances from the main plane of each lens 41, for example, FIG.
In the case of the optical system shown in FIG. LO = L1 (41) LO '= L2 + (L12 + L3 + L4) / N1 + L5 + L6 + (L7 + L8) / N2 + L9 + L10 / N3 (42) LR = L10 / N3 + L9 + (L7 + L8 ) / N2 + L6 + L5 + (L11 + L3) / N1 + L12 (43) LR '= L13 (44) N1: Refractive index N2 of the polarization separation part 58 and the light separation film 59: Refractive index N3 of the diffraction grating 11: Refractive index of the reflecting prism, that is, in the example shown in FIG.
By arranging each lens so as to satisfy 4), the image of the light emitting point is formed on the reflectors 26 and 27 geometrically and the image of the reflectors 26 and 27 is formed on the light receiving element 52. Becomes That is, if the lenses are arranged so as to satisfy the expressions (41) to (44), the light source 51 and the reflectors 26, 27 (3
0a) is arranged at a substantially conjugate position due to the geometrical optical image formation relationship, and the reflectors 16 and 27 (30a) and the light receiving element 52 are arranged.
Will be arranged at a substantially conjugate position due to the geometrical optics image formation relationship.

This displacement detecting device 10 employing such an optical system is provided with reflectors 26, 2 as shown in FIG. 9, for example.
Even when 7 rotates, the position of the image forming point on each light receiving element 52 does not change. That is, although the angle of the light Ld incident on each light receiving element 52 changes, the position of the image forming point on the light receiving element 52 does not change and the optical path length does not change, so that the interference signal does not change. It will be.

Further, the displacement detecting device 10 to which the present invention is applied
May be set so that the above-mentioned LR ′ distance becomes smaller than the LR distance (so that LR ′ / LR ≦ 1). The ratio of the amount of movement of the image forming point in the light receiving element 52 to the amount of movement of the image forming point in the reflectors 26 and 27 is represented by LR ′ / LR. Therefore, by reducing the value of LR '/ LR, the amount of movement of the image forming point on the light receiving surface can be suppressed. That is, LR '/
By setting LR ≦ 1, it is possible to make the moving amount of the image forming point of the light receiving element 52 smaller than the moving amount of the image forming point of the reflectors 26 and 27, and suppress the decrease of the intensity of the interference signal. Is possible. Particularly, in the light emitting / receiving composite unit 12, the housing member 40 described above, the composite lens portion 41,
In the present invention in which the polarization unit 42, the phase plate 43, and the light branching unit 44 are arranged in the same package and configured as an independent unit, LR 'can be made extremely small, so that LR'
/ LR can be made smaller.

That is, in the displacement detecting apparatus 10 to which the present invention is applied, the lenses in the compound lens portion 41 are arranged as described above, whereby the rotation of the diffraction grating 11 and the rotation of the reflectors 26, 27 are caused. Even in this case, it is possible to minimize the deviation in the light receiving element 52,
The influence on the interference signal can be reduced.

Each lens 4 in the compound lens section 41
When the light emitted from each lens 41 is converged when the aperture of No. 1 is small, the diameter of the imaged beam becomes too small, which may be affected by dust or scratches. Therefore, the compound lens unit 41 may diverge the emitted light to the extent that it is not affected by dust or scratches at the image forming point.

Further, each lens 41 in the compound lens portion 41 may change the beam diameter on the diffraction grating 11 and the light receiving element 52 by changing the emitted light into parallel light. As a result, the beam diameter of the light can be made constant at all times, so that when the diffraction grating 11 is mounted, the allowable width in the E1 and E2 directions can be increased as shown in FIG.

The light emitted from the lens 41a is reflected by the reflector 26,
Lights La1 and La2 incident on the diffraction grating 11 are formed by focusing on or collimating the light on 27.
It is also possible to adjust the reflected lights Lb1 and Lb2 to have the same optical path.

The displacement detecting device to which the present invention is applied is
The present invention is not limited to the above embodiment. For example, it can be applied to the following configurations. With respect to these configurations, the same components and members as those of the displacement detection device 10 shown in FIGS. 1 and 3 are designated by the same reference numerals and the description thereof will be omitted.

The displacement detecting apparatus 101 shown in FIG. 10 uses a reflecting prism 50 in the reflecting optical system 14 and produces a single-diffracted light Lb.
It has a quarter-wave plate WP51 that passes only 1 and a quarter-wave plate WP52 that passes only the one-time diffracted light Lb2. Each 1 that has passed through these quarter wave plates WP1 and WP2
The diffracted lights Lb1 and Lb2 are reflected by the reflecting surfaces 50a and 50b, respectively. That is, as compared with the above-described catoptric system shown in FIG. 3, a quarter wave plate is separately arranged.

The displacement detecting device 102 shown in FIG.
As an alternative to the reflecting members 13a and 13b shown in FIG. The diffraction grating 70 changes the directions of incident lights La1, La2, Lc1 and Lc2,
The light is incident on the diffraction grating 11 or the combined light emitting and receiving unit 12.

The displacement detecting device 103 shown in FIG.
By adopting a configuration in which the reflecting members 13a and 13b shown in are omitted,
A reflecting prism 70 having a reflecting surface 70a and each reflecting surface 7
The quarter wave plates WP71 and WP72 arranged at 0a are provided.

The displacement detecting device 104 shown in FIG.
The four wavelength plates WP81 and WP82 are connected to the diffraction grating 11 (the light source 5
(Including 1) and the light receiving and emitting composite unit 12.
By the way, the optical axes of the quarter-wave plates WP81 and WP82 are the light La emitted from the light emitting / receiving composite unit 12.
The tilt angle is 45 ° with respect to the polarization axes of La1 and La2.

The diffraction grating 11 of each displacement detecting device shown in FIGS. 10 to 13 may be sandwiched between scales made of glass plates.

Further, in the displacement detecting device to which the present invention is applied, the diffraction grating 11 in which the gratings are provided in parallel at a predetermined interval is provided.
However, in the present invention, the diffraction grating in which such a grating is provided in parallel may not be used. For example, the angle may be detected using a diffraction grating such as a rotary encoder provided with a radial grating.

The displacement detecting apparatus to which the present invention is applied is not limited to the case where the transmission type diffraction grating 11 is used, and for example, a reflection type diffraction grating may be used.

Further, in the present invention, an amplitude type diffraction grating in which brightness and darkness are recorded and a phase type diffraction grating in which a change in refractive index and a change in shape are recorded may be used, and the type of the diffraction grating is not limited. Absent.

In the displacement detecting apparatus to which the present invention is applied, the case where the diffraction grating 11 is attached to a movable part of a machine tool and the diffraction grating 11 moves in accordance with the movement of the movable part has been described. In the invention, the diffraction grating 11
Needless to say, the displacement detection device may move relatively.

[0086]

As described above in detail, in the displacement detecting device according to the present invention, the diameter of the beam irradiated on the grating surface can be arbitrarily set, so that the influence of dust and scratches can be reduced. Is possible. In addition, by arranging such a compound lens unit that controls the beam diameter of the light emitted to the outside and the beam diameter of the received light in the same package,
The degree of integration can be increased, the manufacturing process can be simplified, and the reliability of the entire device can be increased.

Further, in the displacement detecting apparatus according to the present invention, by packaging each member into an integrated structure, precise position adjustment is facilitated, and it is not necessary to take a large space for arranging parts, so that displacement detection Miniaturization of the entire device,
The weight can be reduced. In addition, by storing each member in the same housing member, it is possible to reduce the effects of environmental changes and changes over time, minimize misalignment during adjustment, etc. Can be increased.

Since the displacement detecting device according to the present invention does not need to use a special light source whose coherence length is limited, a general inexpensive semiconductor laser can be used, and a large cost reduction can be achieved. be able to. Further, it is possible to increase the mounting tolerance of the diffraction grating, the light emitting / receiving unit, etc. with a simple configuration.

[Brief description of drawings]

FIG. 1 is a diagram for explaining a configuration of a displacement detection device according to the present invention.

FIG. 2 is a perspective view of a diffraction grating used for displacement detection.

FIG. 3 is a diagram for explaining a case where a reflective prism is used in a reflective optical system.

FIG. 4 is a configuration diagram of a combined light emitting and receiving unit.

FIG. 5 is a diagram for explaining a polarization direction of a light source.

FIG. 6 is a diagram showing a tendency of light Ld near a light receiving element.

FIG. 7 is a diagram for explaining a positional relationship between a light source, a reflector, and a light receiving element.

FIG. 8 is a diagram for explaining a case where lenses are actually arranged in the displacement detection device to which the present invention is applied.

FIG. 9 is a diagram for explaining a case where a reflector rotates.

FIG. 10 is a diagram for explaining another form of the displacement detection device according to the present invention.

FIG. 11 is a diagram for explaining another mode of the displacement detection device according to the present invention.

FIG. 12 is a diagram for explaining another mode of the displacement detection device according to the present invention.

FIG. 13 is a diagram for explaining another mode of the displacement detection device according to the present invention.

FIG. 14 is a perspective view of a conventional optical displacement measuring device.

FIG. 15 is a side view of a conventional optical displacement measuring device.

FIG. 16 is a perspective view of another conventional optical displacement measuring device.

FIG. 17 is a side view of another conventional optical displacement measuring device.

FIG. 18 is a view for explaining still another conventional optical displacement measuring device.

FIG. 19 is a diagram for explaining an optical displacement measuring device capable of preventing the influence of angular fluctuation of the diffraction grating.

[Explanation of symbols]

10 Displacement Detection Device, 11 Diffraction Grating, 12 Receiving and Emitting Complex Unit, 13 Reflecting Member, 14 Reflecting Optical System, 2
6,27 Reflector, WP1, WP2 1/4 wave plate, 40
Housing member, 41 Compound lens part, 42 Polarizing part, 43
Phase plate, 44 light splitting part, 51 light source, 52 light receiving element, 53, 54 semiconductor substrate, 58 polarization splitting part, 59
Optical branching film

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Akihiro Kuroda             3-9-17 Sogotanda, Shinagawa-ku, Tokyo             Knee Precision Technology Stock Association             In-house (72) Inventor Kayoko Taniguchi             3-9-17 Sogotanda, Shinagawa-ku, Tokyo             Knee Precision Technology Stock Association             In-house (72) Inventor Hideaki Tamiya             3-9-17 Sogotanda, Shinagawa-ku, Tokyo             Knee Precision Technology Stock Association             In-house (72) Inventor Hidehiro Kume             6-735 Kita-Shinagawa, Shinagawa-ku, Tokyo Soni             -Inside the corporation F-term (reference) 2F103 BA04 BA43 CA02 CA03 CA04                       CA08 DA01 DA12 EA15 EB02                       EB12 EB16 EB28 EB32 EB35                       EC01 EC11 EC12 EC14 EC15

Claims (9)

[Claims] 1. A displacement detection device for detecting displacement in a grating vector direction of an object to be inspected having a diffraction grating on the basis of an interference signal, a light source for emitting light, and a light for emitting light from the light source. A beam splitter that separates and emits light, and a first beam splitter disposed between the light source and the beam splitter.
Lens, a reflection unit that reflects two first diffracted light beams obtained by diffracting the two lights emitted from the beam splitter by the diffraction grating, and a first reflection unit that is reflected by the reflection unit. A light splitting unit that splits the combined light into a plurality of light beams by combining two second diffracted light beams obtained by diffracting the diffracted light beam by the diffraction grating, and dividing the combined light beam into a plurality of pieces. A polarizing means for transmitting only a predetermined polarized component, a light receiving means for photoelectrically converting the interference light transmitted through the polarizing means to generate the interference signal, and a second light receiving means arranged between the polarizing means and the light receiving means. Displacement detection device, comprising: 2. The light source, the beam splitter,
The first lens, the light splitting means, the polarizing means, the light receiving means, and the second lens are arranged in the same package and configured as an independent unit. 1. The displacement detection device according to 1. 3. The first portion diffracted by the diffraction grating.
Of the diffracted light of which the polarization component is changed so that the polarization direction of the first diffracted light reflected by the reflecting means is orthogonal to each other, and is arranged so as to be integrated with the reflecting means. The displacement detection device according to claim 1, further comprising: 4. The beam emitted from the beam splitter
2. The displacement detecting device according to claim 1, wherein each of the two lights is converged at an equal distance from the light source. 5. In the reflecting means, the interference fringes of the two second diffracted light beams superposed in the light receiving means are substantially null fringes, or the interference signal is substantially maximum. The displacement detection device according to claim 1, wherein the displacement detection device is arranged as follows. 6. The light source and the reflecting means are arranged at positions substantially conjugate with each other in a geometrical optical image forming relationship, and the reflecting means and the light receiving means are arranged at positions substantially conjugate with each other in a geometrical optical image forming relationship. The displacement detection device according to claim 1, wherein the displacement detection device is arranged. 7. The distance between the reflecting surface of the reflecting means and the main plane of the second lens is equal to or more than the distance between the main plane of the second lens and the light receiving means. 6. The displacement detection device according to 6. 8. The beam splitter is a polarization beam splitter, which is arranged between the diffraction grating and the polarization beam splitter, and changes the polarization state of two lights whose polarization components are orthogonal to each other by ¼. A wavelength plate is provided, and the optical axes of the quarter wavelength plate are inclined by 45 ° with respect to the polarization axes of the two lights, respectively.
The displacement detection device described. 9. The displacement detecting device according to claim 1, wherein the two diffraction orders of the second diffracted light are equal to each other.