JP3208830B2 - Encoder and optical device for encoder - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an encoder and an optical device for an encoder, and more particularly to a plurality of sawtooth-shaped translucent gratings on the outer or inner peripheral surface of a cylindrical object or on a flat plate surface. A light beam is incident on a rotating body or a moving body having an optical scale provided periodically, and rotation information of the rotating body or movement information of the moving body is detected by utilizing the light beam passing through the optical scale. The present invention relates to an encoder and an optical device for the encoder.

[0002]

2. Description of the Related Art Conventionally, the rotational speed of a computer such as a floppy disk drive, office equipment such as a printer, an NC machine tool, and a rotary mechanism such as a captain motor or a rotary drum of a VTR, and the fluctuation amount of the rotational speed. A photoelectric rotary encoder has been used as a means for detecting the position.

FIGS. 8 and 9 are a sectional view and a plan view of a principal part of a rotary encoder using so-called Tollbot interference proposed in Japanese Patent Application Laid-Open Nos. 61-10716 and 1-176914. is there.

In FIG. 1, reference numeral 1 denotes a semiconductor laser, which emits a coherent light beam having a wavelength λ. A collimator lens system 2 converts a divergent light beam from the semiconductor laser 1 into a parallel light beam, and the semiconductor laser 1 and the collimator lens system 2 constitute light irradiation means LR. Reference numeral 3 denotes an optical scale having a light-transmitting lattice portion in which a plurality of V grooves are periodically provided on the inner peripheral surface of the cylindrical member 3c, and rotates in the direction shown by the arrow.

The optical scale 3 is made of a translucent optical material. Three photodetectors 4a, 4b, and 4c constituting the light receiving means 4 are arranged at positions facing the light irradiation means LR with the optical scale 3 interposed therebetween. The output of each photodetector is connected to the signal processing circuit 5. The signal processing circuit 5 includes a pulse counting circuit, a rotation direction determination circuit, a signal interpolation processing circuit, and the like.

[0006] The rotary encoder shown in FIG. 1 causes a light beam from the light irradiation means LR to enter a first scale 3 a in one area of the optical scale 3, and further modulates (diffuses) the light beam on the optical scale 3 to the optical scale 3. Light is modulated (deflected) by being incident on the second scale 3b in another area. Then, a plurality of (three) light beams emitted from the optical scale 3 are received by the light receiving means 4, and rotation information of the optical scale 3 is detected using an output signal from the light receiving means 4.

[0007]

In a conventional rotary encoder utilizing Talbot interference, an optical base on which light irradiating means and light receiving means are mounted is received and received over the entire mounting surface of a mounting portion having a motor and the like. I was wearing it.

For this reason, the distortion of the mounting surface of the mounting portion is transmitted to the optical base as it is, and the surface of the optical base is distorted, causing an error in the optical arrangement of the laser and the collimator lens constituting the light irradiation means. As a result, there has been a problem that the contrast of the output signal obtained by the light receiving means is reduced, and the detection accuracy of the movement information of the moving body is reduced.

[0009]

According to the present invention, the configuration when the optical base on which the light irradiating means and the light receiving means are mounted is attached to the mounting portion, and the assembling method when the optical scale is fixed to the rotating shaft of the rotating body is appropriately set. By doing so, an output signal with good contrast can be obtained from the light receiving means, the optical scale can be fixed to the rotation axis with high accuracy and easily, and an encoder and an encoder capable of detecting the movement information of the moving body with high accuracy The purpose of the present invention is to provide an optical device for use.

[0011]

According to the first aspect of the present invention, there is provided an encoder for irradiating a light beam from a light irradiating means to a first scale of the optical scale of a moving body provided with an optical scale comprising a lattice having a constant period. Then, the light beam light-modulated by the first scale is made incident on a second scale of the optical scale, the light beam light-modulated by the second scale is received by a light receiving unit, and a signal from the light receiving unit is received. In an encoder for detecting movement information of the moving body using the light irradiation means and the light receiving means, the light irradiation means and the light receiving means are mounted on an optical base, and the optical base member has at least three protruding absorbing portions. The optical base is mounted on the mounting surface of the mounting portion via the at least three protruding absorbing portions, and the absorbing portion is made of a material having a lower rigidity than the material of the mounting surface of the mounting portion. There.

According to a second aspect of the present invention, in the first aspect of the present invention, the absorbing portion is made of a resin material.

According to a third aspect of the present invention, in the first aspect of the present invention, the absorbing portion has a tapered shape having a wide contact surface on the optical base side and a narrow contact surface on the mounting portion side.

An optical device for an encoder according to a fourth aspect of the present invention is an optical device for an encoder that detects movement information of a moving body using a light beam passing through an optical scale,
A light irradiating unit for irradiating a first scale of the light source scale with a light beam; and a light beam modulated by a light beam modulated by the first scale incident on a second scale of the optical scale. Light receiving means for receiving light, and the movement information is detected using a signal from the light receiving means, and the light irradiation means and the light receiving means are mounted on an optical base. The optical base member has at least three protruding absorbing portions, and the optical base is mounted on the mounting surface of the mounting portion via the at least three protruding absorbing portions, and the absorbing portion is attached to the mounting portion. It is characterized in that it is made of a material having a lower rigidity than the material of the mounting surface of the mounting portion.

[0015]

FIG. 1 is a perspective view of a main part of a first embodiment of the present invention, and FIG.
FIG. 3 is a cross-sectional view of a main part of the first embodiment of the present invention, FIG. 3 is a schematic view of a main part for describing a method of detecting rotation information when the present invention is applied to a rotary encoder using Talbot interference, and FIG. 3 is an explanatory view of a part of FIG. 3, and FIG. 5 is an explanatory view of an output signal waveform from the light receiving means of FIG.

First, a method of detecting rotation information of a rotating body will be described with reference to FIGS.

In FIG. 1, reference numeral LR denotes light irradiation means, which has a semiconductor laser 1 and a collimator lens 2. Reference numeral 3 denotes an optical scale which has a structure in which a plurality of gratings (grating portions) 3d are provided at a constant period of a grating pitch P on the inner peripheral surface or the outer peripheral surface of the cylindrical member 3c. The optical scale 3 is made of a translucent optical material, for example, a polycarbonate, is provided as a part of the rotating body 6, and rotates around the rotating shaft 6 a integrally with the rotating body 6.

As shown in FIGS. 3 and 4, the grating 3d has two inclined surfaces which are long in the direction perpendicular to the rotation direction of the optical scale 3 (in the direction of the rotation axis 6a) as indicated by the arrow 3f and which are inclined in opposite directions. V-groove (V-groove portion) and a curved surface portion (hereinafter, referred to as a “plane portion”) having a slight curvature based on a cylindrical shape and having a substantially flat surface
).

FIGS. 4A and 4B are detailed views of the grating of the optical scale 3. The grating is formed by alternately arranging the V-grooves 30b-1, 30b-2 and the plane portion 30a. On the inner surface of the cylindrical member 3c, n V-grooves are arranged at regular intervals and are arranged at regular intervals at a pitch P in the circumferential direction. V groove width is 1/2
Each of the two flat portions forming the P and V grooves has a width of 1 / 4.P, and each inclined surface is at least a critical angle with respect to a straight line connecting the bottom and the center of the V groove. Is inclined at θ = 45 °.

The distance D (diameter inside the optical scale) along the optical axis between the first scale (first region) 3a and the second scale (second region) 3b of the optical scale 3 has a grating pitch in this embodiment. P and the wavelength are set as λ so that D = N · P ² / λ (N is a natural number) and P = πD / n (n is the total number of slits (V grooves)).

By setting the diameter D of the optical scale 3 in this manner, the first region 3a on the side surface of the optical scale 3 is set.
Is projected directly on the grid of the second area 3b.
The lattice image projected here is called a Fourier image, and is generated by the self-imaging action of the lattice due to the light diffraction phenomenon.

In this embodiment, the material of the optical scale 3 is made of plastic, so that the optical scale 3 can be easily manufactured by a manufacturing method such as injection molding or compression molding.

Reference numeral 4 denotes light receiving means, which has three photodetectors (light receiving elements) 4a, 4b, and 4c for respectively receiving the three light beams that have been modulated and emitted by the optical scale 3. Reference numeral 5 denotes a signal processing circuit, which includes a pulse count circuit, a rotation direction determination circuit, a signal interpolation processing circuit, and the like.
Rotation information is detected.

Next, a method for detecting rotation information of the optical scale 3 (rotator 6) in this embodiment will be described.

The light beam from the semiconductor laser 1 is converted into convergent light by adjusting the position of the collimator lens system 2, and this converged light beam is converted into a first scale (first area) 3 a of the optical scale 3.
Incident on The reason why the convergent light is used here is that the side surface of the optical scale 3 has a refractive power equivalent to a concave lens due to a difference in curvature between the outer surface and the inner surface. Become light.

The convergent light beam is applied to the grating 3d of the first region 3a.
In FIG. 4, as shown in FIG. 4A, the light beam that has reached the grating portion 30a passes through the grating portion 30a and proceeds into the cylinder. or,
The light beam that has reached the grating portion 30b-1 surface is totally reflected and directed to the 30b-2 surface as shown in the figure because the inclined surface is set to a critical angle or more, and is also totally reflected at the 30b-2 surface. Therefore, the light beam that reaches the surface 30b-1 does not enter the inside of the cylindrical member of the optical scale 3,
It will be returned to the substantially incident direction. Similarly, the light beam that has reached the surface 30b-2 is returned by repeating total reflection.

Therefore, the light beam reaching the range of the two inclined surfaces 30b-1 and 30b-2 forming the V groove in the first region 3a is reflected without entering the cylindrical member, and the light beam reaching the grating portion 30a. Only one will go inside the cylindrical member. That is, in the first region 3a, the V-groove type lattice 3
d has the same function as the transmission type amplitude diffraction grating.

The light beam is diffracted by the grating 3d in the first area 3a, and the diffraction action of the grating produces 0th, ± 1st, ± 2nd,... Diffracted light. As a result of interference between one or three light beams, a Fourier image of the grating in the first region 3 a is formed inside the optical scale 3. The Fourier image is repeatedly formed at a position that is an integral multiple of the distance L behind the lattice plane based on the distance L.

In this embodiment, the light source wavelength λ, the grating pitch P, and the position of the collimator lens system 2 are set such that the third (N = 3) Fourier image is formed on the grating surface of the second area 3b. Is set. The light-dark pitch of this Fourier image is V which is the lattice 3d of the first region 3a and the second region 3b.
It becomes equal to the pitch P of the groove.

In the second region 3b, the light beam incident on the surface 30a is substantially perpendicularly incident as shown in FIG. 4B, so that it is transmitted linearly and reaches the photodetector 4c. Also, the light beams that have reached the two inclined surfaces 30b-1 and 30b-2 forming the V-groove surface are incident on each surface at an incident angle of approximately 45 °, and are greatly refracted in different directions, respectively, so that each of the detectors 4a And 4b. As described above, in the second region 3b, the light flux is 3 due to two different inclined surfaces inclined in different directions with respect to the incident light flux and a plane having a total of three kinds of inclination directions of the V groove and the plane between the V grooves. The light travels in two directions, and reaches photodetectors 4a, 4b, and 4c provided at positions corresponding to the respective surfaces. That is, in the second region 3b, the V-groove grating functions as a light wavefront splitting element.

When the optical scale 3 rotates, the amount of light detected by each of the photodetectors 4a, 4b, 4c changes. If the balance of the amount of light incident on each photodetector changes according to the relative displacement between the position of the grating and the position of the Fourier image, and as a result the optical scale 3 rotates counterclockwise, as shown in FIG. A change in the amount of light accompanying the rotation of the optical scale 3 can be obtained.

Here, the horizontal axis is the rotation amount of the optical scale 3, and the vertical axis is the received light amount. The signals a, b, c correspond to the photo detectors 4a, 4b, 4c, respectively. When the optical scale 3 rotates clockwise, a is 4b,
b is the output of 4a and c is the output of 4c. The rotation direction can be determined from this difference.

FIG. 5A shows a theoretical change in the amount of light when the contrast of the Fourier image is very high and close to the ideal. Actually, the contrast of the Fourier image is lower. As shown in FIG. 5B, each light quantity changes in a substantially sinusoidal manner. Optical scale 3 based on these signals
The rotation information such as the rotation angle and the rotation amount, the rotation speed, and the rotation acceleration of the (rotator 6) is obtained.

Although the present embodiment has been described for a case where the present invention is applied to a rotary encoder, the present invention can be similarly applied to a linear encoder.

Next, the structural features of the rotary encoder of the present invention, such as the optical base and the mounting portion, will be described with reference to FIGS.

In the figure, reference numeral 1a denotes a laser holder, which holds the semiconductor laser 1. Reference numeral 2a denotes a lens holder, which holds the collimator lens 2. 3 is an optical scale and 4 is a light receiving means. Reference numeral 11a denotes an optical base, which is made of, for example, a gin-coated steel material, on which the light irradiating means LR and the light receiving means 4 are mounted. Reference numeral 11b denotes a projection-shaped absorbing portion, which is made of, for example, a polycarbonate resin and is made of a material having a rigidity value smaller than the rigidity of a mounting surface 19a of the mounting portion 19 described later.

The optical base 11a and the absorbing part 11b are manufactured by a so-called outsert molding method by a method of manufacturing a molded article. The optical base 11a and the absorbing part 11b are formed as an integral part. Reference numeral 19 denotes a mounting portion, to which the optical base 11a is attached by the fastening member 18 via the absorbing portion 11b. The mounting portion 19 has a motor and the like for rotating the rotating body 6 about the rotating shaft 6a.

In the conventional rotary encoder, when the optical base 11a is mounted on the mounting portion 19, the mounting surface 19
The entire surface of “a” was in a state of receiving the optical base 11a. Therefore, the distortion of the flatness of the mounting surface 19a of the mounting portion 19 is directly transmitted to the optical base 11a, and the distortion is transmitted to the space between the laser light source 1 and the collimator lens 2 via the laser holder 1a and the lens holder 2a. Had an effect.

As a result, interference fringes formed at the same pitch interval as the first scale 3a formed by the principle of Tolbot interference are formed at positions deviated from the position of the second scale 3b, which is the reference position. In some cases, the contrast of the output signal to be obtained is reduced, and the detection accuracy is reduced.

On the other hand, in this embodiment, the optical base 11
a at least three protruding absorbing portions 11b are provided;
The optical base 11a is attached to the mounting portion 19 via the absorbing portion 11b.
Is mounted on the mounting surface 19a. In particular, the absorbing portion 11b is made of a material whose rigidity is smaller than that of the material of the mounting surface 19a of the mounting portion 19.

Then, the optical base 11 is fastened by the fastening member 18.
The fastening force when tightening a on the mounting surface 19a of the mounting portion 19 is absorbed by the absorbing portion 11b, and is not transmitted to the optical base 11a.

Thus, the optical base 11a is attached to the mounting portion 19
This prevents a change in the distance between the laser light source 1 and the collimator lens 2 when mounted on the camera, maintains a good contrast of the output signal from the light receiving means 4, and improves the detection accuracy of the rotation information of the rotating body.

In particular, the absorbing portion 11b in this embodiment has a cross-sectional shape that is wide on the optical base 11a side and has a narrow taper portion on the mounting portion 19 side, and the contact area of the mounting portion 19 on the mounting surface 19a is small. By reducing it, the way of transmitting distortion is reduced.

FIG. 6 and FIG. 7 are schematic views of a main part near the optical scale 3 according to the second embodiment of the present invention.

FIGS. 6A and 6B are a plan view and a sectional view when the optical scale 3 is mounted on the rotating shaft (shaft portion) 6a, and FIGS. 7A and 7B rotate the optical scale 3. Shaft 6a
3A and 3B are a plan view and a cross-sectional view after being mounted on the device. In the figure, reference numeral 3 denotes an optical scale, and a lattice having a constant pitch is formed on the inner peripheral surface or the outer peripheral surface of the cylindrical member 3c.

Reference numeral 64 denotes a snap portion extending from the cylindrical member 3c. A projection P is formed on a part of the inner wall of the snap portion, and is fixed so as to engage with a groove provided on the rotary shaft 6a. Reference numeral 6a denotes a rotating shaft connected to a rotating body (not shown). A groove is formed in a part of the rotating shaft, and the rotating shaft is engaged with the projection P of the snap portion 64 and fixed. 6
Reference numeral 2 denotes a hinge portion, which is provided above the rotation shaft 6a on the inner peripheral plane of the cylindrical member 3c. Reference numeral 63 denotes a handling unit, which is connected to the hinge unit 62. In this embodiment, each of the elements 62, 63,
Numeral 64 is formed by molding.

In the present embodiment, when assembling the optical scale 3, a handling portion 63 for handling the scale is provided at a place other than the scale portion of the optical scale 3, and the optical scale 3 is assembled to a rotating shaft 6 a that supports the optical scale 3. In finding,
The projection P of the snap part of the optical scale 3 is provided on the rotation axis 6a without directly touching the optical scale.
The optical scale 3 is attached to the rotating shaft 6a by using a groove for engaging with the rotary shaft 6a. Then, after assembling in this state, the handling portion 63 is removed as shown in FIG.

That is, in this embodiment, when attaching the optical scale 3 to the rotary shaft 6a, first, the handle 63 is grasped by hand, and the snap portion 64 having the projection P is fitted into the rotary shaft 6a. The protrusion P of the snap part 64 and the groove of the rotating shaft 6a are engaged and fixed. After that, while holding the handling portion 63, a force is applied to the hinge portion 62 to remove the handling portion 63 and the hinge portion 62 from the cylindrical member 3c.

In this embodiment, if the press-fit margin is set to an appropriate value, the cylindrical optical scale 3 is rotated by a shaft (rotating shaft).
This is preferable because it can be fixed with respect to 6a without shifting during rotation.

With such a configuration, the cylindrical optical scale 3 can be incorporated without touching the lattice portion, and as a result, there is no fear of soiling the lattice portion, and the optical scale 3 can be compared with the conventional attachment using an adhesive. If the replacement of the cylindrical optical scale 3 is considered, it can be easily performed.

[0051]

According to the present invention, as described above, the structure for attaching the optical base on which the light irradiating means and the light receiving means are mounted to the mounting portion and the method for fixing the optical scale to the rotating shaft of the rotating body. By properly setting the assembling method, etc., an output signal with excellent contrast can be obtained from the light receiving means, and the optical scale can be fixed to the rotating shaft with high accuracy and easily, and the movement information of the moving body can be obtained with high accuracy. An encoder and an optical device for the encoder that can be detected can be achieved.

[Brief description of the drawings]

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

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

FIG. 3 is a schematic view of a main part when the present invention is applied to a rotary encoder using Talbot interference.

FIG. 4 is an explanatory view of a part of FIG. 3;

FIG. 5 is an explanatory diagram of an output signal waveform from the light receiving unit in FIG. 3;

FIG. 6 is a schematic diagram of a main part of a second embodiment of the present invention.

FIG. 7 is a schematic view of a main part of a second embodiment of the present invention.

FIG. 8 is a cross-sectional view of a main part of a conventional rotary encoder using Talbot interference.

FIG. 9 is a plan view of a main part of a conventional rotary encoder using Talbot interference.

[Explanation of symbols]

 LR light irradiation means 1 Laser light source 2 Collimator lens 3 Optical scale 3a First scale 3b Second scale 3c Cylindrical member 4 Light receiving means 6 Rotating shaft 11a Optical base 11b Absorbing part 19 Mounting part 19a Mounting surface 62 Hinge part 63 Handling part

──────────────────────────────────────────────────続 き Continued on the front page (58) Fields surveyed (Int. Cl. ⁷ , DB name) G01D 5/00-5/62 G01B 11/00-11/30 G01B 7/00-7/32 G01P 1 / 00-3/80

Claims (4)

(57) [Claims] 1. A moving body provided with an optical scale comprising a grating having a fixed period, a first scale of the optical scale is irradiated with a light beam from a light irradiating unit, and a light beam light-modulated by the first scale is emitted. An encoder that makes the light incident on a second scale of the optical scale, receives the light beam light-modulated by the second scale with a light receiving unit, and detects movement information of the moving body using a signal from the light receiving unit. , light irradiation means and the light receiving means is mounted on the optical base, optical
The base member has at least three protruding absorbing portions,
Wherein the optical base is said at least three protruding through the absorption portion while being mounted on the mounting surface of the mounting portion and the absorbing portion is composed of a material more rigid than the material of the mounting surface is small attachment portion And encoder. 2. The encoder according to claim 1, wherein said absorbing section is made of a resin material. 3. The method according to claim 1, wherein the absorbing portion is wide on the optical base side,
2. The encoder according to claim 1, wherein the encoder has a tapered shape having a narrow contact surface on the mounting portion side. 4. An optical device for an encoder for detecting movement information of a moving body using a light beam passing through an optical scale, the light irradiation for irradiating a light beam to a first scale of the light source scales. Means, and light receiving means for receiving a light beam light-modulated by the first scale and incident on a second scale of the optical scale and receiving a light beam light-modulated, and a signal from the light receiving means With the configuration in which the movement information is detected using, the light irradiation means and the light receiving means are mounted on an optical base, and the optical base member has at least three protruding absorbing portions, wherein the optical base is said at least three protruding through the absorption portion while being mounted on the mounting surface of the mounting portion and the absorbing portion is composed of a material more rigid than the material of the mounting surface is small attachment portion Enko Optical device for the reader.