JP2003322552A - Light receiving-emitting composite unit and displacement detecting device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an inexpensive and highly reliable light receiving-emitting unit and a displacement detecting device suitable for reducing the size and weight. <P>SOLUTION: This device is characterized by having a light source 51 for emitting the light, a polarized light separating part 58 for generating synthetic light by synthesizing the two light reflected from an external optical system by emitting the light to the external optical system by separating the light emitted from the light source 51 into the two light mutually different in a polarized light component, a light branching film 59 for dividing the synthetic light formed by the polarized light separating part 58 into a plurality, a polarized light part 42 for respectively passing only a prescribed polarized light component on the divided synthetic light, a lens part 41 for respectively introducing a plurality of interference light passing through the polarized light part 42 to a prescribed position, and a light receiving element 52 for generating an interference signal by respectively photoelectrically transducing the plurality of interference light introduced by the lens part 41. <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 JP-A-60-98302 is shown in FIGS. 7 and 8. FIG. 7 shows this conventional optical displacement measuring device 10.
0 is a perspective view schematically showing 0, and FIG. 8 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. 9 and 10. FIG. 9 shows a conventional optical displacement measuring device 11
0 is a schematic perspective view, and FIG. 10 is a side view schematically showing a 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 applied to the diffraction grating 111 are diffracted by the diffraction grating, respectively, and become one-time diffracted light. The once diffracted light is reflected by the second mirrors 115a and 115b, respectively. The one-time diffracted light is transmitted to the diffraction grating 11
It is irradiated again to 1 and diffracted to become a diffracted light twice. 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. .

[0011]

However, in the above-mentioned conventional optical displacement measuring devices 100 and 110, it is necessary to assemble while individually adjusting each individually manufactured optical component in the manufacturing process. This required precise adjustments for variations in finish accuracy and characteristics, and had to introduce complicated processes, which was an obstacle to lowering prices.

There is also a problem that a large space is required for adjusting, fastening and fixing each component, and it is impossible to downsize the entire apparatus.

Furthermore, since an adhesive must be used when fixing each part, the bonding state changes according to changes in the surrounding environment, and deviations between the parts occur due to environmental changes and changes over time. There is a fear.

Therefore, the present invention has been proposed in view of the above-mentioned problems, and an object of the present invention is to provide a highly reliable light emitting and receiving composite unit suitable for size reduction and weight reduction at low cost and displacement detection. To provide a device.

[0015]

In order to solve the above-mentioned problems, a light emitting and receiving composite unit according to the present invention has a light source that emits light and a light emitted from the light source that have different polarization components from each other. A polarization beam splitter that splits the light into two lights, outputs the light to an external optical system, and combines the two lights reflected from the external optical system to generate a combined light, and a combined light generated by the polarization beam splitter. A light splitting means for splitting the light into a plurality of rays, a polarizing means for transmitting only the predetermined polarized light component of the divided combined light, a lens portion for guiding a plurality of interference light rays passing through the polarizing means to respective predetermined positions, A plurality of interference lights guided by the lens unit are photoelectrically converted, and a light receiving unit for generating an interference signal is provided.

Further, in order to solve the above-mentioned problems, the displacement detecting apparatus according to the present invention is a displacement detecting apparatus for detecting a displacement in a grating vector direction of an object to be inspected having a diffraction grating based on an interference signal. , A light source that emits light,
The light emitted from the light source has different polarization components from each other.
A polarization beam splitter that splits and outputs two beams of light; a reflection unit that reflects two first diffracted beams obtained by diffracting the two beams of light emitted from the beam splitter by the diffraction grating; The first diffracted light reflected by the means is diffracted by the diffraction grating to obtain two second diffracted light beams, thereby generating a combined light beam,
A light splitting means for splitting the combined light into a plurality of lights, a polarizing means for transmitting only the predetermined polarized light components of the split light, and a lens for guiding a plurality of interference lights passing through the polarizing means to predetermined positions, respectively. And a light receiving unit that photoelectrically converts a plurality of interference lights guided by the lens unit to generate the interference signal.

[0017]

BEST MODE FOR CARRYING OUT THE INVENTION First, a displacement detecting device according to a first embodiment of the present invention will be described.

As shown in FIG. 1, the displacement detecting device 10 according to the first embodiment of the present invention is a transmission type diffraction grating 11 which is attached to a movable part of a machine tool or the like and linearly moves.
And the light emitted by the light emitting element is converted into two lights La1 and L
It is emitted from the light emitting / receiving composite unit 12 that detects the interference signal by interfering the two two-time diffracted lights Lc1 and Lc2 that are separated and emitted into a2 and diffracted by the diffraction grating 11. Two lights La1, La2
Of the two-time diffracted light Lc1 and Lc2 from the diffraction grating 11 to the light-receiving / combining unit 12, and the diffraction grating 11.
The reflection optical system 14 that reflects the two single-time diffracted lights Lb1 and Lb2 from the above and irradiates the diffraction grating 11 again.

As shown in FIG. 2, the diffraction grating 11 has, for example, a thin plate shape, and gratings such as narrow slits and grooves are carved at predetermined intervals on or in the surface thereof.
The light incident on such a diffraction grating 11 is diffracted by a slit or the like carved on the surface and 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.

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. When the diffraction grating 11 is a transmissive type, both the surface on which the light is incident and the surface on which the diffracted light is generated are referred to as a grating surface 11a. Further, the direction in which the grating of the diffraction grating 11 is formed (directions of arrows C1 and C2 in FIG. 2), that is,
A direction perpendicular to a lattice vector indicating the direction of change of the transmittance or reflectance of the grating, the depth of the groove, etc., and the grating surface 1
The direction parallel to 1a is called the lattice direction. The 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. 3), that is, the direction parallel to the grating vector of the diffraction grating 11 is the grating vector direction. Called. The directions of these diffraction gratings 11 will be referred to not only in the first embodiment of the present invention but also in other embodiments.

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 the interference fringes are printed on the 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.

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 where the reflection member 13a irradiates the grating surface 11a of the diffraction grating 11 and a predetermined position where the reflection member 13b irradiates the grating surface 11a of the diffraction grating 11 may be brought close to each other. As a result, the difference in optical path length in the diffraction grating 11 can be reduced, and errors due to uneven thickness of the scale and the like can be reduced.

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 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 sequentially stacked. 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 reflective surface 30a is
The one-time diffracted lights Lb1 and Lb2 are reflected vertically so that the one-time diffracted lights Lb1 and Lb2 go backward in the same path as the incident path. By the way. The one-time diffracted lights Lb1 and Lb2 applied to the reflecting surface 30a have already passed through the quarter-wave plate WP31 and are reflected by the reflecting surface 30a.
Since the diffracted lights Lb1 and Lb2 again pass through the quarter-wave plate WP31, the polarization direction is rotated by 90 °,
The diffraction grating 11 is irradiated again.

Next, the details of the combined light emitting and receiving unit 12 will be described. The combined light receiving and emitting unit 12 includes a housing member 40 for housing a light emitting element and a light receiving element, and a lens portion 41.
And a polarization unit 42 (42 which transmits only a predetermined polarization component).
_1, 42_2, 42_3, 42_4), the phase plate 43 for changing the polarization state of light, and the double-diffracted light Lc1, Lc2 obtained by dividing the light with which the diffraction grating 11 is irradiated or diffracting the diffraction grating 11. And an optical branching unit 44 for separating the light.

The housing member 40 is a light source 5 that emits 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 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 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.

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 photoelectrically converted 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 lens section 41 is an optical element such as a lens having a predetermined numerical aperture. The lens unit 41 includes a light source 51
The light La emitted from is incident. The lens part 41 is
The incident light La is imaged on the grating surface 11a of the diffraction grating 11 and the reflectors 26 and 27 with a predetermined beam diameter. In the first embodiment, since the transmission type diffraction grating 11 is adopted, the outgoing light La is normally reflected by the reflectors 26, 2
Image on 7. For this reason, the diameter of the beam irradiated on the lattice plane 11a can be increased, and the influence of dust and scratches can be reduced. Also like this,
By arranging the lens portion 41 that controls both the beam diameter of the light emitted to the outside and the beam diameter of the received light in the same package, the integration degree can be increased, the manufacturing process can be simplified, and the reliability of the entire device can be improved. Can be increased.

Further, the interference lights Ld1, Ld2, Ld3, and Ld4 emitted from the polarization unit 42 are incident on the lens unit 41, respectively. The lens unit 41 receives each interference light L
d1, Ld2, Ld3, Ld4 are the light receiving elements 52_1, 52
An image is formed on _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. Further, the lens unit 41 may emit parallel light or emit divergent light, not only for converging the beam.

By the way, the lens unit 41 forms an image of the incident light La and each of the interference lights Ld1, Ld2, Ld3, Ld4.
The image formation is performed using one lens unit, but the present invention is not limited to this, and may be performed using a plurality of lens units, for example. The lens forming the lens portion 41 forms a plurality of incident light beams at desired positions, and thus various shapes can be applied. For example, when it is desired to set the interval between the light receiving elements 52 to be narrow, the interference lights Ld1, Ld2, Ld
Since it is necessary to gradually close the interval of 3, Ld4,
As shown in FIG. 4, the shape of the lens portion 41 is changed to the light receiving element 52.
It is configured to be convex toward.

Further, when the distance between the light source 51 and the light receiving element 52 is set to be short, the shape of the lens portion 41 is configured to be convex near the light source 51 as shown in FIG.

That is, the lens portion 41 is composed of the light source 51.
The image forming point of light can be determined based on the arrangement of the light receiving element 52 and the light receiving element 52. Also, when designing the circuit, the light source 5
1 and the light receiving elements can be arranged with a certain degree of freedom. In addition, by using the lens unit 41 as an optional unit, it is possible to flexibly cope with various specifications of the IC.

The lens portion 41 is not limited to the above-mentioned form, and for example, a constitution in which the lens portion 41 and the compound prism are integrated may be applied.

This composite prism is designed so that the incident light La,
Also, the optical path is controlled by refracting the interference lights Ld1, Ld2, Ld3, and Ld4. The composite prism has the effect described above in combination with the lens portion 41, and may be integrally molded with the lens portion 41 to form a molded component.

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. It suffices that the polarization sections 42 are arranged at intervals of 45 ° (for example, 5 °, 50 °, 95 °, 140 °), and the polarization sections 42 can be arranged without any restriction on the posture at the time of attachment. In addition, by providing such a polarization unit 42 between the phase plate 43 and the lens unit 41, there is also an advantage that the entire unit can be made compact.

The phase plate 43 includes a polarization 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. By the way, this phase plate 43 is used for the light source 51.
The light La enters from the lens 41a through the lens 41a. The phase plate 43 converts the light La, which is, for example, linearly polarized light, into circularly polarized light and irradiates the polarized light separating unit 58 with the light. Also, this phase plate 43
Is the light branching films 59_1, 59_2, 59_3, 59_4.
The combined lights Ld1, Ld2, Ld3, and Ld4 emitted from are received, converted into circularly polarized light, and emitted to the above-described polarization unit 42. That is, a configuration is adopted in which the conversion of the light La from the light source 51 and the conversion of the light Ld from the light branching film 59 are shared by one phase plate 43. Note that the combined light emitting and receiving unit 12
Can also be applied to a configuration in which the phase plate 43 is omitted.

The polarization separation section 58 is composed of, for example, a polarization beam splitter, and the light La emitted from the light source 51 is incident on 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.
Further, the twice-diffracted light Lc1 and the twice-diffracted light Lc2 from the diffraction grating 11 are incident on the polarization splitting portion 58. The polarization beam splitting unit 58 superimposes the two two-time diffracted lights Lc1 and Lc2 to combine them, and outputs the combined light Ld 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.

In the combined light emitting and receiving unit 12, the housing member 40, the lens portion 41, the polarizing portion 42, the phase plate 43, and the light branching portion 44 described above are arranged in the same package as an independent unit. Composed. 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 detector 10 of the first embodiment 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 portion 41 as shown in FIG. Light La is
An image is converted by the lens unit 41, and the phase plate 43 made of, for example, a quarter-wave plate is irradiated with the image.

The light La emitted to the phase plate 43 is changed into circularly polarized light by the phase plate 43. That is, the linearly polarized light La emitted through the phase plate 43 is emitted from the light source 5
It is possible to change to circularly polarized light regardless of the polarization direction of the light emitted from 1. As a result, the polarization component of the light emitted from the light source 51 can be freely selected without making the polarization component of the light emitted from the light source 51 about 45 ° with respect to the polarization splitting unit 58 as in the prior art. It will be possible.

The light La emitted from the phase plate 43 is, for example, S-polarized light 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: pitch of diffraction grating λ: wavelength of light m: first-order diffracted light Lb1 and Lb2 are reflectors 26 and 27, respectively.
Reflected vertically. At this time, the one-time diffracted lights Lb1 and Lb
Since 2 passes through the quarter-wave plates WP1 and WP2 twice, the polarization directions are rotated by 90 °. For this reason,
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. Polarization separation unit 58
Then, the P-polarized twice-diffracted light Lc1 and the S-polarized twice-diffracted light Lc2 are superimposed 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 synthetic 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 °. In addition, the polarization unit 42_3 transmits only the 90 ° polarization direction.
No. 4 transmits only the polarization direction of 135 °.
At this time, the interference lights Ld1 and Ld transmitted through each polarization unit 42
The strengths of 2, Ld3, and Ld4 are expressed by the following equations (21) to (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 formulas passes through the lens 41 and is received by the light receiving elements 52_1, 52_2, 52_3, 52_4.
Is imaged. That is, each light receiving element 52 photoelectrically converts the interference light Ld represented by the above equation 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.

Next, a displacement detecting device according to a second embodiment of the present invention will be described. Constituent elements and members that are the same as those of the displacement detection device 10 according to the first exemplary embodiment are assigned the same reference numerals and the description thereof is cited, and the description of the present exemplary embodiment is omitted.

As shown in FIG. 6, the displacement detecting device 70 according to the second embodiment of the present invention is a reflection type diffraction grating 71 which is attached to a movable part of a machine tool or the like and linearly moves.
And the light emitted by the light emitting element is converted into two lights La1 and L
The light emitting / receiving composite unit 12 detects the interference signal by interfering the two two-time diffracted lights Lc1 and Lc2, which are separated into a2 and are diffracted by the diffraction grating 71, and emitted from the light emitting / receiving composite unit 12. Two lights La1, La2
Of the two-time diffracted light Lc1 and Lc2 from the diffraction grating 71 to the light receiving and emitting composite unit 12, and the diffraction grating 71.
The reflection optical system 74 that reflects the two single-time diffracted lights Lb1 and Lb2 from the above and irradiates the diffraction grating 71 again.

The diffraction grating 71 has, for example, a thin plate shape, and a grating such as narrow slits or grooves is engraved on the surface thereof at predetermined intervals. Light incident on such a diffraction grating 71 is diffracted by a slit or the like carved on the surface,
The diffraction grating 71 is reflected. Diffracted light generated by diffraction is generated in the direction determined by the grating interval and the wavelength of light.

In the present invention, the kind 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 73a reflects the light La1 and irradiates it at a predetermined position on the grating surface 71a of the diffraction grating 71. The light La1 is diffracted by the diffraction grating 71 to obtain the once-diffracted light Lb1. The reflecting member 73b receives the light L
It reflects a2 and irradiates it at a predetermined position on the grating surface 71a of the diffraction grating 71. The light La2 is diffracted by the diffraction grating 71 to obtain the once-diffracted light Lb2.

Further, the reflecting member 73a has one-time diffracted light Lb.
2 generated when 1 is diffracted by the diffraction grating 71
The diffracted light Lc1 is emitted. The reflecting member 73a reflects the twice-diffracted light Lc1 and irradiates the combined light-emitting / receiving unit 12 with the light. Further, the reflecting member 73b has a single diffracted light Lb2.
Is diffracted by the diffraction grating 71, and the double-diffracted light Lc2 is emitted. The reflection member 73b is
The diffracted light Lc2 is reflected and irradiated to the light emitting / receiving composite unit 12.

By the way, the predetermined position where the reflecting member 73a irradiates the grating surface 71a of the diffraction grating 71 and the predetermined position where the reflecting member 73b irradiates the grating surface 71a of the diffraction grating 71 are located at the same position. Image.
At this time, it is desirable that the beam diameter be large enough not to be affected by dust or scratches on the grating surface 71a. Further, this image formation point does not necessarily have to be the point where the beam diameter is the smallest, and the point where the difference in the optical path lengths in the beam images is the smallest may be located on the grating surface 71a.

The reflection optical system 74 includes a reflector 76 that reflects the once-diffracted light Lb1 and irradiates the diffraction grating 71 again, and a reflector 77 that reflects the once-diffracted light Lb2 and irradiates the diffraction grating 71 again. 1 / Changing the polarization state of the diffracted light Lb1 1 /
It has a four-wave plate WP71 and a quarter-wave plate WP72 that changes the polarization state of the once-diffracted light Lb2.

The reflector 76 is irradiated with the one-time diffracted light Lb1 that has passed through the quarter-wave plate WP71. Reflector 76
Reflects the one-time diffracted light Lb1 vertically so that the one-time diffracted light Lb1 goes back in the same path as the incident path. By the way, the one-time diffracted light Lb1 emitted to the reflector 76
Has already passed through the quarter-wave plate WP71, and the one-time diffracted light Lb1 reflected by the reflector 76 has passed through the quarter-wave plate WP71 again, so that the polarization direction is rotated by 90 °. Then, the diffraction grating 71 is irradiated again.

The reflector 77 is irradiated with the one-time diffracted light Lb2 that has passed through the quarter-wave plate WP72. Reflector 77
Reflects the one-time diffracted light Lb2 vertically so that the one-time diffracted light Lb2 goes backward in the same path as the incident path.

The reflector 77 is irradiated with the one-time diffracted light Lb2 that has passed through the quarter-wave plate WP72. Reflector 77
Reflects the one-time diffracted light Lb2 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 emitted to the reflector 77
Has already passed through the quarter-wave plate WP72, and the one-time diffracted light Lb2 reflected by the reflector 77 again passes through the quarter-wave plate WP72, so that the polarization direction is rotated by 90 °. Then, the diffraction grating 71 is irradiated again.

For the details of the combined light emitting and receiving unit 12 in the second embodiment and the operation example in the second embodiment, the description of the first embodiment is cited.

That is, in the displacement detecting device 70 according to the second embodiment using the reflection type diffraction grating 71, each member in the light emitting and receiving composite unit 12 is packaged into an integrated structure to perform precise position adjustment. Becomes easier,
Also, there is no need to take up a large space for arranging parts,
It is possible to reduce the size and weight of the entire displacement detection device. Further, by housing each member in the same housing member, it is possible to reduce the effects of environmental changes and changes over time, and it is possible to minimize misalignment during adjustment, etc. The reliability of can be increased.

Also in the second embodiment, since the conversion of the light La from the light source 51 and the conversion of the light Ld from the light branching film 59 are shared by one phase plate 43, the size is also reduced. It becomes easier to manage and it is possible to further reduce the manufacturing cost. Furthermore, by making the detector-side exit surface of the lens unit non-planar, the detector and the overall shape can be freely designed.

The displacement detectors of the first and second embodiments to which the present invention is applied have been described above. In the displacement detection device of each embodiment, the diffraction gratings 11 and 71 in which the gratings are provided in parallel at a predetermined interval are used, but in the present invention, the diffraction gratings in which such gratings are provided in parallel are used. You don't have to. For example, the angle may be detected using a diffraction grating provided with a radial grating such as a rotary encoder.

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.

Further, in the displacement detecting device of each embodiment,
The case where the diffraction gratings 11 and 71 are attached to a movable part such as a machine tool and the diffraction grating 11 moves according to the movement of the movable part has been described.
It goes without saying that it is sufficient if the displacement detectors 1, 71 and the displacement detector relatively move.

[0075]

As described above in detail, in the displacement detecting device and the combined light receiving and emitting unit according to the present invention, the respective members are packaged into an integrated structure, which facilitates precise position adjustment. It is not necessary to take a large space for arranging parts, and the displacement detecting device can be downsized and lightweight. In addition, by storing each member in the same housing member, it is possible to reduce the influence of environmental changes and changes over time, and it is possible to minimize misalignment at the time of adjustment and, in turn, the displacement detection device and receiver. The reliability of the entire light emitting composite unit can be improved.

Further, the displacement detecting device and the combined light emitting and receiving unit according to the present invention have a lens portion for guiding the light La emitted from the light source and the light emitted from the light branching portion to a predetermined image forming point. The displacement detection device and the combined light emitting and receiving unit having this lens portion can determine the image forming point of light based on the arrangement of the light source and the light receiving element. In addition, even when designing the circuit, it is possible to give flexibility to the arrangement of the light source and the light receiving element, and by using the lens unit as an optional unit, it is possible to flexibly cope with various specifications of the IC. be able to.

[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 another configuration diagram of the combined light emitting and receiving unit.

FIG. 6 is a diagram for explaining a displacement detection device using a reflection type diffraction grating.

FIG. 7 is a perspective view of a conventional optical displacement measuring device.

FIG. 8 is a side view of a conventional optical displacement measuring device.

FIG. 9 is a perspective view of another conventional optical displacement measuring device.

FIG. 10 is a side view of another conventional optical displacement measuring device.

[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 lens part, 42 polarizing part, 43 phase plate, 44 light splitting part, 51 light source, 52 light receiving element,
53, 54 semiconductor substrate, 58 polarized light separating section, 59 light branching film

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Hidehiro Kume             6-735 Kita-Shinagawa, Shinagawa-ku, Tokyo Soni             -Inside the corporation (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 Akihiro Kuroda             3-9-17 Sogotanda, Shinagawa-ku, Tokyo             Knee Precision Technology Stock Association             In-house F-term (reference) 2F103 BA01 BA04 BA43 CA04 CA08                       DA01 DA12 EA02 EA15 EA18                       EA19 EA20 EB02 EB12 EB16                       EB28 EB32 EB35 EC01 EC11                       EC12 EC13 EC14 EC15

Claims (11)

[Claims] 1. A light source that emits light, and the light emitted from the light source is split into two lights having different polarization components, emitted to an external optical system, and reflected from the external optical system. A polarization beam splitter that combines two lights to generate a combined light, a light splitting unit that splits the combined light generated by the polarization beam splitter into a plurality of beams, and transmits only the predetermined polarization component to each of the divided combined lights. A polarization unit, a lens unit that guides the plurality of interference lights that have passed through the polarization unit to predetermined positions, and a light receiving unit that photoelectrically converts the plurality of interference lights that are guided by the lens unit to generate an interference signal. And a combined light emitting and receiving unit. 2. The light emitting / receiving composite according to claim 1, wherein the lens unit is further arranged between the light source and the polarization beam splitter to change a propagation direction of light emitted from the light source. unit. 3. The light emitting / receiving composite unit according to claim 1, wherein the lens unit forms an image of the plurality of interference lights transmitted through the polarization unit. 4. The combined light emitting and receiving unit according to claim 1, wherein the lens portion is configured to be convex toward the light receiving means. 5. The lens section guides the interference light such that the distance between the light source and the light receiving means is shorter than the distance between the polarization beam splitter and the light splitting means. Item 7. A light emitting and receiving composite unit according to item 1. 6. A displacement detection device for detecting displacement in a grating vector direction of an object to be inspected having a diffraction grating based on an interference signal, wherein a light source emitting light and light emitted from the light source are mutually polarized. 2 different ingredients
A polarization beam splitter that splits and outputs two beams of light; a reflection unit that reflects two first diffracted beams obtained by diffracting the two beams of light emitted from the beam splitter by the diffraction grating; A light splitting unit configured to combine the two second diffracted lights obtained by diffracting the first diffracted light reflected by the means with the diffraction grating to generate combined light, and dividing the combined light into a plurality of lights. A polarizing unit that transmits only the predetermined polarized component of the divided combined light; a lens unit that guides a plurality of interference lights that have passed through the polarizing unit to a predetermined position; and a plurality of lens units that are guided by the lens unit. A displacement detecting device comprising: a light receiving unit that photoelectrically converts the interference light to generate the interference signal. 7. The displacement detecting device according to claim 6, wherein the lens unit is further arranged between the light source and the polarization beam splitter, and changes the propagation direction of the light emitted from the light source. . 8. The displacement detection device according to claim 6, further comprising a compound lens that forms an image of the plurality of interference lights that have passed through the polarization unit. 9. The displacement detecting device according to claim 6, wherein the compound lens and the lens portion are formed by an integral molding component. 10. The light source, the polarization beam splitter, the reflection means, the light splitting means, the polarization means, the lens section, and the light receiving means are arranged in the same package and are independent units. The displacement detection device according to claim 6, wherein the displacement detection device is configured as follows. 11. The displacement detecting device according to claim 6, wherein the diffraction grating is a transmission type or a reflection type diffraction grating.