JPH1172355A - Displacement information detector - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a displacement information detector capable of accurately detecting displacement information of an optical scale having V-shaped grooves in a predetermined period. SOLUTION: Optical fluxes from a light source 1 are collected by a lens system 2 and are allowed to be incident on a first region 3d of a grating section of an optical scale 3 capable of being relatively rotated with respect to the optical fluxes. Grating widths in the diameter direction of the grating section are different from each other. The light from the grating section of the first region 3a is reflected by a concave mirror 4 of a reflection member to be incident on a second region 3b having a grating width different from that of the first region 3a. The optical fluxes via the second region 3b are received, thereby detecting relative rotational displacement information of the optical scale 3.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a displacement information detecting apparatus, and more particularly, to a physical quantity of displacement information such as rotation information and movement of a displaced object using diffraction generated when light is irradiated on a displaced object (optical scale). Is suitable for a rotary encoder or the like which can obtain the value with high accuracy.

[0002]

2. Description of the Related Art Conventionally, NC machine tools and the like have a rotary encoder or a linear encoder (hereinafter referred to as an "encoder") as a displacement information detecting device for detecting displacement information such as a moving amount and a rotating amount of an object (displaced object). ) Is used.

In particular, encoders are widely used in machine tools and measuring devices because they have a simple structure and can detect the amount of angular displacement and the amount of movement with high accuracy.

FIG. 17 is a schematic view of a main part of an encoder proposed in Japanese Patent Publication No. 36-11793. In the drawing, a light beam from a light source 201 passes through an opening 202a provided in a substrate 202, and is then converted into a substantially parallel light beam by a lens system 203 as a first area of an optical scale 204 as a displacement object provided with a radiation grating (linear grating). 204a.

[0005] The ± n-order diffracted light diffracted by the grating of the first area 204a of the optical scale 204 is guided to the second area 204b of the optical scale 204 via the lens system 205, the corner cube 206, and the lens system 207. , An interference pattern is formed on the surface. A light beam based on the interference pattern that has passed through the second region 204b is collected by the lens system 208 and detected by the light receiving element 209.

At this time, the optical scale 204 is indicated by an arrow 204
c, the interference pattern formed on the optical scale 204 is displaced in the opposite direction.
9, a signal having a period twice as long as the grating resolution (grating pitch) is obtained.

The encoder shown in FIG. 1 obtains displacement information of the optical scale 204 using a periodic signal obtained by the light receiving element 209.

[0008]

In the encoder shown in FIG. 17, the incident area (first area 204a) of the light beam from the light source 201 to the optical scale 204 and the diffracted light beam diffracted by the optical scale 204 are converted into optical members 205, 206, and 206. The re-incident area (second area 204b) when re-entering the optical scale 204 via the 207 is set to be located in the displacement direction 204c on the optical scale 204.

For this reason, especially when applied to a rotary encoder, a large space is required for arranging each element such as a light source, a plurality of lens systems, and a light receiving element, and diffracted light from an optical scale is applied to the optical scale. Many optical members are required for re-entering, and the whole apparatus tends to be complicated and large.

In addition, since a light beam (diffracted light) that enters and exits substantially perpendicularly to the optical scale is used, the diffracted light exiting to the left and right of the light receiving element is likely to become stray light, and the entire apparatus can be reduced in size and simplified. However, there is a problem that it is difficult to obtain high-precision displacement information while trying. In addition, if the distance between the optical scale and the plurality of lens systems deviates from the design value (if there is a gap change), there is a problem that the S / N ratio of the signal obtained by the light receiving means decreases. In particular, the allowable value of the gap from the design value becomes stricter as the grating pitch becomes finer.

It is a first object of the present invention to provide a displacement information detecting device suitable for a rotary encoder for detecting a rotational displacement with high accuracy while simplifying the entire device.

A rotary encoder for detecting displacement information of a displaced object with high accuracy while reducing the space for disposing each member and simplifying the entire apparatus, and relaxing the permissible error in disposing each member. A second object is to provide a suitable displacement information detecting device.

[0013]

According to the present invention, there is provided a displacement information detecting apparatus comprising: (1-1) a displacement information detecting device for causing a light beam to enter a first region of a grating portion having a different grating width in a radial direction of an optical scale rotatable relative to a light beam; The light from the grating portion of the first region is reflected by a reflecting member and is incident on a second region having a grating width different from the grating width of the first region of the grating portion, and the luminous flux passing through the second region And detecting relative rotational displacement information of the optical scale.

In particular, (1-1-1) the reflection member inverts the image of the grid in the first area at a magnification substantially matching the grid in the second area and in the traveling direction of the grid. It is characterized by being arranged to project.

(1-2) A first area on a rotatable optical scale in which a radial grating portion in which a light beam from a light irradiating means is arranged at a constant period via a lens system is provided on the circumference of a disk. And diffracted light diffracted by the grating portion of the first area is reflected by a mirror, and is incident on the second area of the optical scale.
In a displacement information detecting device for detecting displacement information of the optical scale by receiving a light beam passing through a grating portion of the second region by a light receiving means, the first region and the second region are each provided with a rotation axis of the optical scale. Are located in different regions in the radial direction.

In particular, (1-2-1) the grating portion is formed of an amplitude grating.

(1-2-2) A plurality of ± n-order diffracted lights diffracted by the grating portion of the first area of the optical scale are reflected by the mirror and superimposed on the second area of the optical scale. To form an interference pattern.

(1-2-3) The lens system emits a light beam from the light irradiation means as a condensed light beam.

(1-2-4) The mirror comprises a concave mirror for reflecting the 0th-order light and ± nth-order diffracted light diffracted by the grating portion of the first region.

(1-2-5) The lens system emits a light beam from the light irradiation means as a parallel light beam.

(1-2-6) The mirror comprises a plane mirror provided for each diffracted light that reflects the 0th-order light and ± nth-order diffracted light diffracted by the grating portion of the first region.

(1-2-7) The lattice section uses a V-groove lattice. And so on.

(1-3) A light beam from the light irradiation means is condensed by a lens system, and a grating portion having a wavefront dividing function is provided on a rotatable optical scale provided on a circumference of a disk in a first area. The light is made incident, the diffracted light diffracted by the grating section of the first area is reflected by a concave mirror and made incident on the second area of the optical scale, and the light beam passing through the grating section of the second area is received by the light receiving means. Accordingly, in the displacement information detecting device for detecting displacement information of the optical scale, the first region and the second region are located in different regions in a radial direction of a rotation axis of the optical scale, and ± n-order diffracted light from the grating portion of one region is converged on or near the surface of the concave mirror, and the concave mirror forms an image of the first region of the optical scale on the second region by an eccentric system. It is characterized by having.

In particular, (1-3-1) the wavefront dividing function grating is a V-groove grating.

(1-3-2) The concave mirror forms an image of the first area in an enlarged or reduced form on a second area.

(1-3-3) A plurality of diffracted lights of ± n order diffracted light diffracted by the grating portion of the first area of the optical scale are reflected by the concave mirror and superimposed on the second area of the optical scale. To form an interference pattern.

(1-3-4) The light receiving means has a plurality of light receiving elements, and a light beam based on the interference pattern superimposed on the second area of the optical scale is provided in a V-groove of a lattice portion of the second area. And are incident on the plurality of light receiving elements respectively in a plurality of directions.

(1-3-5) The light source and the reflecting surface of the concave mirror have a substantially conjugate relationship by the lens system.

(1-3-6) A part of the optical scale is located at the center of curvature of the concave mirror. And so on.

[0030]

1 and 2 show a first embodiment of the present invention.
3 is a partial cross-sectional view of a part of the first embodiment of the present invention, FIG. 4 is an explanatory view of an optical scale and a concave mirror of a part of the first embodiment of the present invention, and FIG. FIG. 6 is an explanatory view of a part of an optical scale according to the first embodiment of the present invention, FIG. 6 is an explanatory view of a signal from a grating portion and a light receiving unit of the optical scale as a part of the first embodiment of the present invention, and FIG. FIG. 8 is an explanatory diagram of a re-formed image on the optical scale of FIG. 1, FIG. 8 is an explanatory diagram of a scale pitch and a superposition pitch with respect to the amount of eccentricity of the concave mirror in the first embodiment of the present invention, and FIG. FIG. 10 is an explanatory view of a scale pitch and a superposition pitch with respect to the amount of eccentricity of the concave mirror in FIG. 10, FIG. 10 is a cross-sectional view of a main part of a part of the first embodiment of the present invention, and FIG. Other facts that indicate the state of incidence Form of illustration, FIG. 12 is an explanatory view of another embodiment showing an incident state of the light beam to the optical scale in Embodiment 1 of the present invention.

In FIG. 1, reference numeral 1 denotes a light source, which comprises, for example, an LED or a semiconductor laser, and emits a coherent light beam having a wavelength λ (632.8 nm). Reference numeral 2 denotes a lens system, which is composed of a spherical lens or an aspherical lens, condenses a light beam from the light source 1 and guides it to an optical scale 3 described later.

The light source 1, the lens system 2 and the like constitute one element of the light irradiation means LR. Reference numeral 3 denotes an optical scale having a phase difference detecting function and an amplitude type diffraction grating function. As shown in FIGS. 5 and 6, a plurality of radial gratings (number of slits) having a fixed period are formed on the surface of a disk-shaped substrate 3c. A grating portion 3d composed of 2500 or 5000 V-groove gratings) is provided.
The substrate 3c of the optical scale 3 is made of a porous optical material, for example, polycarbonate or plastic, and has a rotating body (not shown).
And a rotating shaft 3e integrated with the rotating body.
Is rotated in the direction of arrow 6 around the center.

FIGS. 6A and 6B are detailed views of the grating portion 3d of the optical scale 3, in which two inclined surfaces 30b-1 and 30b-2 and one flat portion 30a forming a V-groove are defined. Are alternately arranged at the pitch P to form the lattice portions 3d. The width of the V groove is (1/2) P, and the two inclined surfaces 30b-1 and 30b-2 forming the V groove each have a width of (1/4) P, and each of the inclined surfaces 30b-1, 30b-2 inclines at a critical angle or more with respect to a straight line connecting the bottom of the V-groove and the perpendicular to the flat portion 30a, at θ = 45 ° in the present embodiment.

In this embodiment, of the diffracted light from the optical scale 3, three luminous fluxes of the 0th-order diffracted light and ± 1st-order diffracted light are used. Here, since the V-groove of the grating portion 3d is formed radially with respect to the optical scale 3, the pitch is different between the inner peripheral side and the outer peripheral side of the optical scale 3. Here, the pitch means the width of the circumferential flat portion 30a and the two inclined surfaces 3
It refers to the sum of the widths of 0b-1 and 30b-2.

In this embodiment, the material of the optical scale 3 is made of polycarbonate or plastic, and is made by a method such as injection molding or compression molding. Reference numeral 4 denotes a concave mirror, which comprises a spherical mirror, an elliptical mirror, a parabolic mirror, an aspherical mirror, and the like. The concave mirror 4 coincides with the Fourier transform plane of the grating 3d.

In this embodiment, as shown in FIGS. 3 and 4, the light beam 101 condensed by the lens system 2 and incident on the first region 3a of the optical scale 3 is diffracted by the grating portion of the optical scale 3. nth order diffracted light (0th order and ± 1st order diffracted light L
Each element is set so that (0), L (+1), L (-1)) converge on the surface 4b of the concave mirror 4 or its vicinity (the pupil position of the concave mirror 4 or its vicinity).

The optical axis 4a of the concave mirror 4 and the incident light beam 101
The center ray (principal ray) 101a is decentered by the eccentricity Δ as shown in FIG. The concave mirror 4 is an optical scale 3
Convergent light beam (three diffracted light beams L
(0), L (+1), L (-1)), and an interference pattern image (image) based on three diffracted lights as shown in FIG. 7 is reproduced in the second region 3b on the optical scale 3 surface. It is forming an image. At this time, when the optical scale 3 moves in the rotation direction 6, the re-imaged image moves in a direction opposite to the rotation direction 6.
That is, the grating portion and the interference pattern image are relatively displaced relative to each other by a value twice as large as the moving amount of the optical scale 3.

In this embodiment, the optical scale 3
In this case, rotation information having twice the resolution of the grating portion configured as described above is obtained.

Numeral 5 denotes a light receiving means, and a light beam based on the phase relationship between the interference pattern formed near the second region 3b of the grating portion 3d of the optical scale 3 as shown in FIG. It has three photodetectors (light receiving elements) 5a, 5b, and 5c for receiving the three light beams that are geometrically refracted and emitted in the region 3b. The signal from the light receiving means 5 is processed by a signal processing circuit 103 having a pulse counting circuit and a rotation direction discriminating circuit, and rotation information is obtained from this. The light source 1, the lens system 2, and the light receiving means 5 are fixed and held in the housing PK.

Next, a method for detecting rotation information of the optical scale (rotating body) 3 in this embodiment will be described. The luminous flux from LED1, which is one element of the light irradiating means, is passed through
Thereby, light is condensed on the reflecting surface 4b on the concave mirror surface 4 or in the vicinity thereof. This convergent light is made incident on the first region 3a on the grating portion 3d of the optical scale 3, as shown in FIGS. 6 of the convergent light incident on the first region 3a.
The light beam that has reached the plane portion 30a of the grating portion 3d shown in (1) passes through the plane portion 30a, advances to the concave mirror 4, and forms an image on that surface. Also, the light beam that has reached the inclined surface 30b-1 forming the V-groove is totally reflected as shown in FIG. 6 to form the V-groove, since the inclination angle of the inclined surface 30b-1 is set to be equal to or greater than the critical angle. To the other inclined surface 30b-2
The light is totally reflected also at 0b-2.

As described above, finally, the inclined surface 3 of the lattice portion 3d
The light beam that has reached 0b-1 is returned to the incident direction without entering the concave mirror. Similarly, the light beam that has reached the other inclined surface 30b-2 constituting the V-groove is returned by repeating total reflection. Therefore, in the first region 3a, V
The light beam that reaches the range of the two inclined surfaces 30b-1 and 30b-2 that form the groove is reflected without entering the optical scale 3, and only the light beam that reaches the plane portion 30a travels on the optical scale 3. become.

That is, in the first region 3a, the V-groove type grating portion 3d has the same optical action as the transmission type amplitude diffraction grating. The light beam is diffracted by the grating portion 3d of the first region 3a,
Due to the action of the grating portion, diffracted light of 0 order, ± 1 order, ± 2 order 生 じ is generated, and the diffracted light is condensed on the surface of the concave mirror 4.
The collected diffracted light is reflected by the concave mirror 4 decentered with respect to the principal ray 101a,
An image is formed again in the area 3b, and an image (an image of a radial groove) is formed again on the surface of the optical scale 3.

Here, the first region 3a and the second region 3b are regions which are radially different from the grating portion 3d of the radial grating on the surface of the optical scale 3 (they may partially overlap). At this time, since the optical scale 3 has the radial grating portions 3d, the grating pitches of the first region 3a and the second region 3b are different. Further, the pitch of the inner circumference side and the outer circumference side of the optical scale 3 also differ in the irradiation area of the second area 3b.

Therefore, in the present embodiment, the lattice portion of the first region 3a is enlarged and projected on the second region 3b on the lattice portion 3d, and an image (inverted image) similar to the pitch of the radial lattice portion 3d of the optical scale 3 is obtained. Is formed. Therefore, in the present embodiment, the concave mirror 4 is set to a desired radius of curvature R,
The incident light beam is eccentrically arranged with respect to the principal ray 101a, and the shift amount Δ with respect to the incident optical axis is set to an optimum value.

Thus, when the image of the grating portion of the first region 3a is re-imaged on the surface of the second region 3b by the concave mirror 4, the pitch of a part of the radial grating is matched so that S / S
A detection signal having a good N ratio is obtained.

The light beam incident on the plane portion 30a in the second region 3b is transmitted linearly as shown in FIG. 6B, and reaches the photodetector 5c at the center of the light receiving means 5. Further, two inclined surfaces 30b-1 and 30b forming a V-groove surface
The light beam that has arrived at b-2 is incident on each surface at an incident angle of 45 °, so that it is refracted greatly in different directions, and the photodetectors 5a and 5b on both sides of the light receiving means 5 are received.
To reach.

As described above, in the second region 3b, the two inclined surfaces 30b-inclined in different directions with respect to the incident light beam.
The light flux advances in three directions by the three different planes of the inclination direction of the plane portion 30a between the 1, 30b-2 and the V groove, and the photodetectors 5a provided at positions corresponding to the respective planes. , 5b, 5c. That is, in the second region 3b, the grating portion 3d of the V-groove functions as a light wavefront splitting element.

That is, the light flux based on the phase relationship between the grating portion of the second region 3b and the interference pattern image formed on the surface is 3
, And each photodetector 5a, 5b, 5c
Incident on

When the optical scale 3 rotates, the amount of light detected by each of the photo detectors 5a, 5b, 5c changes. Assuming that the balance of the amount of light incident on each photodetector changes according to the relative displacement between the position of the grating portion 3d and the position of the image, and as a result, the optical scale 3 rotates counterclockwise, as shown in FIG. Such a change in the amount of light accompanying the rotation of the optical scale 3 is obtained. Here, the horizontal axis is the amount of rotation of the optical scale 3, and the vertical axis is the amount of received light.

The signals a, b, c correspond to the photo detectors 5a, 5b, 5c, respectively. Conversely, when the optical scale 3 is rotated clockwise, the signal a is the photodetector 5b, the signal b is the photodetector 5a, and the signal c.
Is the output of the photodetector 5c. Based on these signals, rotation information such as the rotation angle and rotation amount of the optical scale 3 or the rotation speed and rotation acceleration is obtained.

FIG. 6C shows a theoretical change in the amount of light when the contrast of the image formed in the second region 3b is very high and close to ideal.

FIGS. 8 and 9 show 2500 pulses (25 pulses) per round as a grating portion on the optical scale 3 in this embodiment.
00P / R) and 5000 pulses (5000P / R), the light flux 10 incident on the first area 3a of the optical scale 3
The second region 3b when the first principal ray 101a is decentered by Δ with respect to the optical axis 4a of the concave mirror 4 when the first principal ray 101a is reflected by the concave mirror 4 and enters the second region 3b (when the amount of eccentricity is Δ)
5 shows the scale pitch of the grating portion with respect to the distance from the incident chief ray.

In addition, when the grating portion of the first region 3a is formed in the second region 3b by the concave mirror 4 when the amount of eccentricity is Δ, the overlapping pitch with respect to the distance from the incident principal ray of the image of the grating portion is shown. I have.

As shown in FIGS. 8 and 9, the eccentricity Δ is Δ:
When the distance is 0.62 (nm), the distance between the incident chief ray of the second region 3b and the incident pitch is near 1.8 mm, and the scale pitch and the superimposition pitch are substantially the same.

In the present embodiment, an area whose distance from the incident principal ray 101a is in the vicinity of 1.8 mm is used.

In this embodiment, the light source 1 is controlled by the lens system 2.
And the reflecting surface 4b of the concave mirror 4 have a substantially conjugate relationship, so that ± n-order diffracted light from the optical scale 3 is condensed on the reflecting surface 4b of the concave mirror 4 or in the vicinity thereof. Also, a part of the optical scale 3 is made to coincide with the center of curvature of the concave mirror 4.

Thus, even if the distance (gap) between the optical scale 3 and the concave mirror 4 is slightly displaced from the set value, the error of the displacement information obtained by the light receiving means 5 is reduced.
That is, the allowable value of the gap characteristic is relaxed.

FIGS. 10A and 10B are explanatory views of incident light and reflected light when there is an error in the gap between the optical scale 3 and the concave mirror 4. FIG.

When the optical scale 3 is located at the position of the radius of curvature of the concave mirror 4 as shown in FIG. 10A, that is, at the position of the best gap, the diffracted light diffracted by the V-groove is reflected by the concave mirror 4 and becomes optical. Since the light is condensed on the surface of the scale surface 3, the contrast of the interference fringes shows the maximum value.

However, when the optical scale 3 is deviated from the position of the best gap as shown in FIG. 10B, the diffracted light is reflected by the concave mirror 4 on the surface of the optical scale 3 and then on the optical scale 3. Since no light is collected, the contrast of the interference pattern is reduced.

Since such a decrease in the contrast of the interference pattern is linked to a decrease in the output signal detected by the light receiving means, it is important how much the contrast is reduced by shifting the optical scale from the best gap. Value.

In this embodiment, the center of curvature of the concave mirror 4 is located near one point of the optical scale 3.
Further, the light source 1 and the concave mirror 4 are made to have a substantially conjugate relationship by the lens system 2 so that a decrease in contrast when the optical scale 3 deviates from the best gap is reduced.
A signal with a good N ratio is obtained.

In the present embodiment, as described above, the incident position of the principal ray when the light is incident on the optical scale, reflected by the concave mirror, and re-enters the optical scale is set to be different in the radial direction. The rotation information of the rotating object (optical scale) is detected with high accuracy while increasing the degree of freedom in the arrangement of the optical scale, the light receiving means, and the like, and reducing the size of the entire apparatus.

Further, the light source and the concave mirror are made to have a substantially conjugate relationship by the lens system, and a part of the optical scale is set to be located at a position having a substantially radius of curvature of the concave mirror. The allowable value of the interval (gap) from the design value is relaxed.

FIGS. 11 and 12 show that the light beam 101 emitted from the light source in this embodiment, passes through the lens system, is diffracted after entering the first area 3a of the optical scale 3, and forms an image on the concave mirror 4 surface. FIG. 9 is an explanatory diagram showing an optical path of another embodiment of the light beam 102 reflected by the concave mirror 4 and passing through the second area 3 b of the optical scale 3.

FIGS. 11 (A), 11 (B) and 11 (C) show a light beam 101 passing through the lens system from the first area 3a closer to the rotation axis 3e on the grating portion of the optical scale 3 and a concave mirror. 4 shows a case where the light is reflected by the light source 4 and re-enters the second region 3b farther from the rotation axis 3e.

That is, the case where the lattice portion of the first area 3a is enlarged and imaged on the second area 3b by the concave mirror 4 is shown.
In FIG. 11A, the light flux 101 is the first area 3a.
11B, the light beam 101 obliquely enters the second region 3b after being reflected by the concave mirror 4 and then obliquely enters the first region 3a and the second region 3b in FIGS. 11B and 11C. Shows the case.

FIGS. 12A, 12B and 12C show a light beam 101 passing through a lens system from a first area 3a farther from a rotation axis 3e on a grating portion of an optical scale 3 and a concave mirror. 4 shows a case where the light is reflected on the second region 3b closer to the rotation axis 3e. That is, a case is shown in which the grating of the first area 3a is reduced and imaged on the second area 3b by the concave mirror 4. Among them, FIG.
Is obliquely incident on the first region 3a, and is perpendicularly incident on the second region 3b after being reflected by the concave mirror 4, and FIG.
(C) shows a case where the light beam 101 is obliquely incident on the first region 3a and the second region 3b. In each of the configurations in FIGS. 11 and 12, the same effect as in the first embodiment is obtained.

FIG. 13 is a schematic view of a main part of a second embodiment of the present invention. This embodiment is the first embodiment shown in FIGS.
(1) that the light beam from the light irradiation means 1 is incident on the first area 3a of the optical scale 3 as a parallel light beam by the lens system 2.

0 from the first area 3a of the optical scale 3
The second-order light and the ± n-th order diffracted lights are condensed by the concave mirror 4 at the focal position 4c, and then are incident as divergent light on the second region 3b of the optical scale 3 to form interference fringes on the surface. , And the other configurations are the same.

That is, in the present embodiment, as shown in FIG.
A light beam from the light irradiating means 1 is converted into a parallel light beam by a lens system, and a lattice portion in which radial V-grooves are arranged at a constant period is provided on a rotatable optical scale 3 provided on a circumference of a disk in a first area 3a. The light is made incident, the diffracted light diffracted by the grating portion of the first area 3a is reflected by the concave mirror 4 and condensed at the focal point 4c, and then made incident as divergent light on the second area 3b of the optical scale. The light beam passing through the grating portion is received by the light receiving means 5 to detect displacement information of the optical scale 3.

At this time, the first area 3a and the second area 3b are located in different areas in the radial direction of the rotation axis 3e of the optical scale 3, and the concave mirror 4 is located in the first area of the optical scale 3. An image 3a is formed on the second area 3b by an eccentric system.

FIG. 14 is a schematic view of a main part of a third embodiment of the present invention. This embodiment is the first embodiment shown in FIGS.
When the light beam from the light irradiation means 1 is condensed by the lens system 2 and is incident on the first area 3a of the optical scale 3, it is condensed on the focal position 4c of the concave mirror 4.

After the diffracted light from the first area 3a of the optical scale 3 is condensed at the focal position 4c, it becomes divergent light, is reflected by the concave mirror 4, and then becomes a parallel light flux, then becomes the second area of the optical scale 3 3b, and interference fringes are formed on the surface. , And the other configurations are the same.

That is, in this embodiment, as shown in FIG.
A first area on a rotatable optical scale 3 in which a light beam from a light irradiating means 1 is condensed by a lens system 2 and a lattice portion having radial V-grooves arranged at a constant period is provided on the circumference of a disk. 3a, the diffracted light diffracted by the grating portion of the first region 3a is condensed at the focal position 4c of the concave mirror 4, reflected as a divergent light beam by the concave mirror 4 to become a parallel light beam, and The displacement information of the optical scale 3 is detected by making the light incident on the two regions 3 b and receiving the light beam passing through the lattice portion of the second region 3 b by the light receiving means 5.

At this time, the first area 3a and the second area 3b are located in different areas in the radial direction of the rotation axis 3e of the optical scale 3, and the concave mirror 4 is located in the first area of the optical scale 3. An image 3a is formed on the second area 3b by an eccentric system.

FIG. 15 is a schematic view of a main part of a fourth embodiment of the present invention, and FIG. 16 is an enlarged perspective view of a part of FIG. This embodiment is different from the first embodiment shown in FIGS. 1 to 12 in that the light beam from the light irradiation means 1 is incident on the first area 3 a of the optical scale 3 as a parallel light beam by the lens system 2.

The parallel light of the 0th-order light and ± nth-order diffracted light diffracted by the grating portion of the first area 3a is converted into plane mirrors 41 and 4 respectively
The light is reflected at 2, 43 and is incident on the second region 3 of the optical scale 3 to form interference fringes on the surface. , And the other configurations are the same.

That is, in this embodiment, as shown in FIGS. 15 and 16, the light beam from the light irradiating means 1 is converted into a parallel light beam 101 by the lens system 2 and a lattice portion in which linear V-grooves are arranged at regular intervals is used as a substrate. First on the movable optical scale 3 provided above
Zero-order light L (0) and ± n-order (n = 1) diffracted lights L (+), L diffracted by the grating portion of the first region 3a after being incident on the region 3a
The parallel light of (-1) is reflected by the plane mirrors 41, 42, and 43, respectively, and is incident on the second area 3b of the optical scale 3.
The displacement information of the optical scale 3 is detected by receiving the light beam passing through the lattice portion of the second area 3b by the light receiving means 5.

Here, the first area 3a and the second area 3b are located in different areas in the radial direction of the rotation axis 3e of the optical scale 3.

In this embodiment, the diffracted light transmitted through the first area of the optical scale 3 may be three or more light beams.

In the present invention, a V-groove grating having a V-shaped cross section is used as a grating portion for detecting the phase difference of the optical scale. Applicable.

For example, an optical scale having a grating portion as shown in FIGS. 18 to 22 may be used.

FIGS. 18A and 18B are cross-sectional views of the essential parts of another embodiment of the grating portion 3d of the optical scale 3 according to the present invention. The present embodiment is different from the first embodiment in that a curved surface having a curvature is used instead of the inclined surface which is a plane constituting the lattice portion 3d shown in FIG. 6, and the other structures are the same.

That is, on the surface of the disk-shaped substrate 3c, there is provided a grating portion 3d composed of a plurality of radiation gratings having a constant period. The lattice portion 3d is configured by alternately arranging one flat surface portion 30a and two curved surfaces 30b-1 and 30b-2 having a curvature at a predetermined pitch P.

FIG. 18A corresponds to the first region 3a, and only the light beam incident on the plane portion 30a of the grating portion 3d passes through the optical scale 3 and is incident on the curved surface 30b-1 (30b-2). Is the curved surface 30b-1 (30b-2) and the plane portion 3
This shows a state where the light is totally reflected at 0a and returned to the incident direction.

FIG. 18B shows the second area 3 of the optical scale.
3B illustrates the optical path of the light beam incident on b. As described above, the grating portion 3d has the same optical action as that of the transmission type amplitude diffraction grating as shown in FIGS. 6A and 6B.

FIGS. 19A and 19B are cross-sectional views of a main part of another embodiment of the grating portion 3d of the optical scale 3 according to the present invention. In this embodiment, a curved surface 30b having a curvature is used instead of the inclined surface composed of the flat surface constituting the lattice portion 3d shown in FIG.
-1 and 30b-2, and is different in that a flat surface portion 30b-3 is provided between the curved surfaces, and the other configurations are the same.

That is, on the surface of the disk-shaped substrate 3c, there is provided a grating portion 3d composed of a plurality of radiation gratings having a constant period. The lattice portion 3d has one flat portion 30a, two curved surfaces 30b-1, 30b-2 having a curvature, and a flat portion 30b-
3 are alternately arranged at a predetermined pitch P.

FIG. 19A corresponds to the first region 3a, and only the light beam incident on the plane portion 30a and the plane portion 30b-3 of the grating portion 3d passes through the optical scale 3 and becomes the curved surface 30b-1.
The light beam incident on (30b-2) is curved surface 30b-1 (30
b-2) and a state where the light is totally reflected by the plane portion 30a and returned to the incident direction.

FIG. 19B shows the second area 3 of the optical scale.
3B illustrates the optical path of the light beam incident on b. As described above, the grating portion 3d has the same optical action as that of the transmission type amplitude diffraction grating as shown in FIGS. 6A and 6B.

FIGS. 20A and 20B are cross-sectional views of the main part of another embodiment of the grating portion 3d of the optical scale 3 according to the present invention. This embodiment is different from the first embodiment in that the V-groove shown in FIG. 6 is replaced by triangular protrusions (30b-1, 30b-2), and the other configurations are the same.

That is, a grating portion 3d composed of a plurality of radiation gratings having a constant period is provided on the surface of the disk-shaped substrate 3c. The grid portion 3d is configured by alternately arranging one flat portion 30a and two flat portions 30b-1 and 30b-2 each including a flat surface at a predetermined pitch P.

FIG. 20A corresponds to the first region 3a, and only the light beam incident on the plane portion 30a of the grating portion 3d passes through the optical scale 3 and is incident on the plane portion 30b-1 (30b-2). The luminous flux is totally reflected by the other plane portion 30b-2 (30b-1) and is returned to the incident direction.

FIG. 20B shows the second area 3 of the optical scale.
3B illustrates the optical path of the light beam incident on b. As described above, the grating portion 3d has the same optical action as that of the transmission type amplitude diffraction grating as shown in FIGS. 6A and 6B.

FIGS. 21A and 21B are cross-sectional views of main parts of another embodiment of the grating portion 3d of the optical scale 3 according to the present invention. The present embodiment is different from the first embodiment in that a protrusion composed of two curved surfaces 30b-b and 30b-2 having a curvature is formed instead of the V-shaped groove in FIG. 6, and the other configuration is the same.

That is, on the surface of the disk-shaped substrate 3c, there is provided a grating portion 3d composed of a plurality of radiation gratings having a constant period. The lattice portion 3d has one flat portion 30a and a curvature, and is configured by alternately arranging two projecting curved surfaces 30b-1 and 30b-2 at a predetermined pitch P.

FIG. 21A corresponds to the first region 3a, and only the light beam incident on the plane portion 30a of the grating portion 3d passes through the optical scale 3 and is incident on the curved surface 30b-1 (30b-2). Is totally reflected by the curved surface 30b-1 (30b-2),
This shows a state in which the light is returned to the incident direction.

FIG. 21B shows the second area 3 of the optical scale.
3B illustrates the optical path of the light beam incident on b. As described above, the grating portion 3d has the same optical action as that of the transmission type amplitude diffraction grating as shown in FIGS. 6A and 6B.

FIGS. 22A and 22B are cross-sectional views of the main part of another embodiment of the grating portion 3d of the optical scale 3 according to the present invention. In this embodiment, a curved surface 30b having a curvature is used instead of the inclined surface composed of the flat surface constituting the lattice portion 3d shown in FIG.
-1, 30b-2, and the plane portion 30 between the curved surfaces.
The configuration is different from b-3, and the other configuration is the same.

That is, on the surface of the disk-shaped substrate 3c, there is provided a grating portion 3d composed of a plurality of radiation gratings having a constant period. The lattice portion 3d is configured by alternately arranging one flat surface portion 30a and two curved surfaces 30b-1 and 30b-2 having a curvature at a predetermined pitch P.

FIG. 22A corresponds to the first region 3a, and only the light beam incident on the plane portions 30a and 30b-3 of the grating portion 3d passes through the optical scale 3 and is formed on the curved surface 30b-1.
The light beam incident on (30b-2) is curved surface 30b-1 (30
b-2) and the surface 30b-2 (30b-1) are totally reflected and returned to the incident direction.

FIG. 22B shows the second area 3 of the optical scale.
3B illustrates the optical path of the light beam incident on b. As described above, the grating portion 3d has the same optical action as that of the transmission type amplitude diffraction grating as shown in FIGS. 6A and 6B.

[0104]

According to the present invention, the rotation detection can be performed with high accuracy by simplifying the entire apparatus by reflecting light from the first area, making it incident on the second area having a different grating width, and receiving the light. .

Further, according to the present invention, the condensed light is made incident on the first region of the lattice portion on the disk, and the diffracted light is radially different in the eccentric system by the concave mirror at or near the condensing position. By forming an image on the area and receiving the light through the grid portion of the second area, the space for arranging each member is reduced, the entire apparatus is simplified, and the permissible arrangement of each member is achieved. A displacement information detection device suitable for a rotary encoder or the like that detects displacement information of a displaced object with high accuracy while reducing errors can be achieved.

[Brief description of the drawings]

FIG. 1 is a perspective view of a main part of a part of a first embodiment of the present invention.

FIG. 2 is a perspective view of a main part of a part of the first embodiment of the present invention.

FIG. 3 is a sectional view of a main part of a part of the first embodiment of the present invention;

FIG. 4 is a diagram illustrating a part of an optical scale and a concave mirror according to the first embodiment of the present invention.

FIG. 5 is an explanatory diagram of a part of an optical scale according to the first embodiment of the present invention.

FIG. 6 is an explanatory diagram of a grating portion of an optical scale and a signal from a light receiving unit in a part of the first embodiment of the present invention.

FIG. 7 is an explanatory diagram of a re-imaged image on the optical scale according to the first embodiment of the present invention.

FIG. 8 is an explanatory diagram of a scale pitch and a superposition pitch with respect to the amount of eccentricity of the concave mirror according to the first embodiment of the present invention.

FIG. 9 is an explanatory diagram of a scale pitch and a superposition pitch with respect to the amount of eccentricity of the concave mirror according to the first embodiment of the present invention.

FIG. 10 is a sectional view of a principal part of a part of the first embodiment of the present invention;

FIG. 11 is an explanatory diagram of another embodiment showing a state of incidence of a light beam on an optical scale according to the first embodiment of the present invention.

FIG. 12 is an explanatory view of another embodiment showing a state of incidence of a light beam on an optical scale according to the first embodiment of the present invention.

FIG. 13 is a fragmentary cross-sectional view of a part of Embodiment 2 of the present invention.

FIG. 14 is a fragmentary cross-sectional view of a part of Embodiment 3 of the present invention;

FIG. 15 is a fragmentary cross-sectional view of a part of Embodiment 4 of the present invention;

16 is an enlarged perspective view of a part of FIG.

FIG. 17 is a schematic view of a main part of a conventional encoder.

FIG. 18 is an explanatory view of another embodiment of the optical scale according to the present invention.

FIG. 19 is an explanatory view of another embodiment of the optical scale according to the present invention.

FIG. 20 is an explanatory view of another embodiment of the optical scale according to the present invention.

FIG. 21 is an explanatory view of another embodiment of the optical scale according to the present invention.

FIG. 22 is an explanatory view of another embodiment of the optical scale according to the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Light source 2 Lens system 3 Optical scale 3a 1st area 3b 2nd area 3c Substrate 3d Lattice part 3e Rotation axis 4 Concave mirror 4a Optical axis 41,42,43 Planar mirror 5 Light receiving means 101,102 Incident light flux 101a, 102a Principal ray 103 signal processing circuit

Claims (17)

[Claims] 1. An optical scale that is rotatable relative to a light beam and is incident on a first region of a grating portion having a different grating width in a radial direction, and light from the grating portion of the first region is reflected by a reflecting member. Detecting the relative rotation displacement information of the optical scale by making the light incident on a second region having a lattice width different from the lattice width of the first region of the lattice part, receiving a light beam passing through the second region; Characteristic displacement information detection device. 2. The reflection member projects the image of the grid of the first area on the grid of the second area at a magnification substantially matching the grid and in such a manner that the image is inverted in the traveling direction of the grid. The displacement information detection device according to claim 1, wherein the displacement information detection device is disposed. 3. A luminous flux from the light irradiating means is made to enter a first area on a rotatable optical scale provided on a circumference of a disk with a radial grating portion disposed at a constant period via a lens system. The diffracted light diffracted by the grating portion of the first area is reflected by each mirror and made incident on the second area of the optical scale, and the light beam passing through the grating area of the second area is received by the light receiving means. A displacement information detecting device for detecting displacement information of the optical scale, wherein the first area and the second area are located in different areas in a radial direction of a rotation axis of the optical scale. Displacement information detection device. 4. The displacement information detecting device according to claim 3, wherein said grating portion is formed of an amplitude type grating. 5. A plurality of diffracted lights of ± n order diffracted light diffracted by a grating portion of a first area of the optical scale are reflected by the mirror and superimposed on a second area of the optical scale to form an interference pattern. The displacement information detecting device according to claim 3, wherein the displacement information is detected. 6. The displacement information detecting apparatus according to claim 3, wherein the lens system emits a light beam from the light irradiating means as a converged light beam. 7. The displacement information detecting device according to claim 6, wherein the mirror comprises a concave mirror for reflecting the 0th order light and ± nth order diffracted light diffracted by the grating portion of the first area. 8. The displacement information detecting device according to claim 3, wherein the lens system emits a light beam from the light irradiation unit as a parallel light beam. 9. The mirror according to claim 8, wherein the mirror comprises a plane mirror provided for each of the diffracted lights for reflecting the 0th-order light and ± nth-order diffracted lights diffracted by the grating portion of the first region. Displacement information detection device. 10. The displacement information detecting device according to claim 3, wherein the grating section uses a V-groove grating. 11. A light beam from the light irradiating means is condensed by a lens system, and a grating portion having a wavefront dividing function is made incident on a first area on a rotatable optical scale provided on a circumference of a disk.
The diffracted light diffracted by the grating portion of the first area is reflected by a concave mirror and made incident on a second area of the optical scale.
In a displacement information detecting device for detecting displacement information of the optical scale by receiving a light beam passing through a lattice portion of the region by a light receiving means, the first region and the second region are arranged in a radial direction of a rotation axis of the optical scale. , The ± n-order diffracted light from the grating portion of the first region is focused on or near the surface of the concave mirror, and the concave mirror is A displacement information detecting device, wherein one region is imaged on a second region by an eccentric system. 12. The displacement information detecting device according to claim 11, wherein said wavefront dividing function grating is a V-groove grating. 13. The concave mirror according to claim 1, wherein the first region is a second region.
12. The displacement information detecting device according to claim 11, wherein an image is enlarged or reduced in an area. 14. A plurality of diffracted lights of ± n order diffracted light diffracted by a grating portion of a first area of the optical scale are reflected by the concave mirror and superimposed on a second area of the optical scale to form an interference pattern. The displacement information detecting device according to claim 9, wherein the displacement information detecting device is formed. 15. The light receiving means has a plurality of light receiving elements, and a light beam based on an interference pattern superimposed in a second region of the optical scale is directed in a plurality of directions by V-grooves in a lattice portion of the second region. 15. The displacement information detecting device according to claim 14, wherein the light beams are separated and incident on the plurality of light receiving elements, respectively. 16. The displacement information detecting device according to claim 11, wherein the light source and the reflecting surface of the concave mirror are substantially conjugated by the lens system. 17. The displacement information detecting device according to claim 11, wherein a part of the optical scale is located at a center of curvature of the concave mirror.