JPH08201115A - Rotary encoder - Google Patents

Abstract

PURPOSE: To make possible the obtaining of higher resolutions with a simple structure. CONSTITUTION: An optical disc 110 is fixed on the rotating shaft of a servo motor. A data for detecting an angle of rotation is recorded on a data surface of the optical disc 110 depending on the presence of pits 111-113. A pit 110b is provided to detect one rotation made. A laser light 125 is outputted from a light source 121 of an optical system 120. A distribution refractive index lens 122 gets the laser light 125 condensed onto a track with the pins 111-113 provided. The distribution refractive index lens 123 turns the laser light reflected on the pit 111 to a parallel light beam. A photo detector 124 receives the laser light as parallel light beam to be converted into an electrical signal. This makes possible the obtaining of higher resolutions corresponding to a recording density of the data of the optical disc 110.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a rotary encoder for detecting a rotation angle and the like, and more particularly to a rotary encoder for detecting a rotation angle and the like by detecting a pulse signal proportional to the rotation angle.

[0002]

2. Description of the Related Art A rotary encoder is attached to a servomotor controlled by a numerical control device and is used to detect information such as a rotation angle of the servomotor. The rotary encoder has a disk attached to the shaft of the servomotor, and the disk is provided with a slit. By detecting the light passing through this slit, the rotation angle, the rotation direction, and the rotation speed can be recognized.

For example, an incremental type rotary encoder is provided with three sets of light sources and light receiving elements which are arranged with a rotating disk interposed therebetween. Two of them are 90 ° to each other
Two-phase pulse trains having different phases are detected. The rotation angle and the rotation direction are determined by this pulse train. At this time,
In order to improve the resolution, phase division is performed based on a two-phase pulse train. Since the number of pulses increases due to the phase division, the resolution can be increased. The other set of the light source and the light receiving element detects one pulse per one rotation of the rotating disk. The absolute position is determined by counting the two-phase signals with reference to the time of outputting the pulse.

Since the resolution of such a rotary encoder is determined by the width of the slit, it is necessary to narrow the width of the slit in order to further increase the resolution. However, if the width of the slit is narrowed, the amount of light is reduced and the influence of the diffraction of the transmitted light becomes large, so there is a limit to narrowing the width of the slit. Moreover, if the width of the slit is narrowed and the amount of light is reduced, the detection signal reacts sensitively to dust.
Therefore, even if extremely small dust adheres to the slit, the wrong rotation angle or the like may be detected.

Therefore, in a conventional rotary encoder having a high resolution, a slit of a rotating disk and a slit having a phase shift of 360 degrees are provided between the rotating disk and a light source, and light is received by a light receiving element having a wide area, thereby making it possible to obtain a light amount. Was compensating for the decline.

FIG. 7 is a diagram showing a conventional rotary encoder. The rotating disk 310 is provided with slits 311 for detecting a two-phase pulse train at equal intervals in the circumferential direction. Further, several slits 312 for detecting one pulse per one rotation of the rotating disk 310 are provided as slits 31.
It is provided inside 1. Each slit 311 and 312
Is a hole elongated in the radial direction.

The light source 301 emits light 302 toward the slits 311 and 312. This light 302 is an LED
Light emitted from the light emitting element such as. The lens 303 is
It is provided between the light source 301 and the rotating disk 310,
The light 302 from the light source 301 is converted into parallel rays perpendicular to the rotating disk 310. The mask 330 provided between the lens 303 and the rotary disk 310 is provided with the slits 311 and 312 of the rotary disk 310 and five slits 331 to 335 that are out of phase by 360 degrees. Slit 3
31 to 334 are provided on the path of the light with which the slit 311 of the rotating disk is irradiated. On the other hand, the slit 335
Is provided on the path of the light with which the slit 312 of the rotating disk is irradiated.

Light receiving elements 321 to 325 having an area sufficiently larger than the slits 311 and 312 are provided at positions corresponding to the slits 331 to 335 on the opposite side of the mask 330 with respect to the rotary disk 310. .
The light receiving elements 321 and 322 and the light receiving elements 323 and 324 are installed at positions where their phases are shifted by 90 degrees. The light receiving elements 322 and 324 are different from the light receiving elements 321 and 323 in that
It outputs a signal with positive and negative inversion. The light receiving element 325 detects a signal each time the slit 312 crosses the light path.

In such a rotary encoder,
The traveling direction of the light 302 radially output from the light source 301 is changed by the lens 303 to a direction perpendicular to the rotating disk 310. Of the light 302, only the light of the slits 331 to 335 of the mask 330 is the mask 330.
And is irradiated onto the rotating disk 310.

Of the light emitted to the rotating disk 310, the amount of light that has passed through the slits 311 and 312 is determined by each light receiving element 3.
21 to 325. These lights are detected as a sine wave corresponding to the rotation of the rotating disk 310. In addition,
The sine waves detected by the light receiving element 321 and the light receiving element 323 are 90 degrees out of phase with each other. Then, the light receiving element 321
From the detection signals of the light receiving element 323 and the light receiving element 323, the rotation direction and the rotation speed of the rotating disk 310 are calculated. At this time, the light receiving elements 321, 323 detected by the light receiving elements 322, 324.
The detected signal is phase-divided by the opposite signal.
The absolute position is determined by counting the two-phase signals of the light receiving element 321 and the light receiving element 323 with the pulse detected by the light receiving element 325 as a reference.

As described above, high resolution can be ensured by performing the phase division or using the light receiving element having a wide area.

[0012]

However, if an attempt is made to increase resolution by performing phase division, an extra pulse train phase division circuit is required. Further, a mask and a large number of light receiving elements having a large area are also required to compensate for the decrease in the amount of light. Therefore, there is a problem that the structure of the rotary encoder becomes complicated.

The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a rotary encoder capable of obtaining high resolution with a simple structure.

[0014]

In order to solve the above-mentioned problems, the present invention provides a rotary encoder for detecting a rotation angle, etc., in which a track mounted on a rotary shaft and having data recorded therein for detecting the rotation angle is recorded. An optical system including an optical disc provided, a laser light irradiation unit for irradiating the track with laser light, and a light receiving unit for reading the data by receiving reflected light from the track. A featured rotary encoder is provided.

[0015]

The optical disc mounted on the rotary shaft is provided with a track on which data for detecting the rotation angle is recorded. When the laser light irradiation unit of the optical system irradiates the track with the laser light, the intensity of the reflected light changes depending on the recorded data. The data is read by receiving the reflected light by the light receiving unit.

As a result, a high resolution can be obtained according to the recording density of the data on the optical disk.

[0017]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a diagram showing a data detection mechanism portion of a rotary encoder of the present invention. In this figure, an optical disk 110 on which data is recorded and an optical system 12 for detecting data are shown.
0 is shown.

The optical disk 110 is fixed to the rotary shaft of a servo motor. On the data surface of the optical disk 110, data for detecting the rotation angle is provided with pits 111 to 1
It is recorded depending on the presence or absence of 13. Pits 111-11
The height “h” of 3 is about 0.11 μm. This pit 1
11 to 113 are provided for one track at regular intervals. The pit length and the interval "d" are 3T to 11T (T
Is set within the range of (wavelength of laser light to be irradiated). The optical disk 110 is provided with a transparent protective film on the reflecting surface on which data is recorded. In addition, a pit 110b for detecting that one rotation has been made is also provided. The pits 111 to 113 and 110b are elongated in the rotation direction 1 of the optical disk 110.

A laser light 125 is output from the light source 121 of the optical system 120. The distributed index lens 122 focuses the laser light 125 on the track provided with the pits 111 to 113. Spot 1 of focused laser light
26 is a region wider than the width of the pit. This light source 12
1 and the distributed index lens 122 constitute a laser beam irradiation section.

On the other hand, the distributed index lens 123 converts the laser light reflected by the pit 111 into parallel rays. The light receiving element 124 receives the laser light that has become a parallel light beam and converts it into an electric signal. The distributed index lens 123 and the light receiving element 124 form a light receiving portion.

The distributed index lenses 122 and 1 described above are used.
A cylindrical lens 23 has a refractive index squared in the radial direction. Such a distributed index lens has a diameter of 1
The lens has a large aperture angle, high magnification, and high light-condensing ability, although it is a very small lens having a length of about 1 mm and a length of 1 to 2 mm. Therefore, since it is possible to focus on a position that is quite close, it is possible to narrow the distance from the optical disc.

In such a structure, the optical disk 1
Reference numeral 10 rotates in the same direction as the rotation axis of the servomotor, but at the same angle. The laser light 125 output from the light source 121 of the laser light irradiation unit is condensed by the distributed refraction lens 122 and is irradiated onto the track provided with the pits 111 to 113 for detecting the rotation angle. Of the irradiated laser light, the light reflected by the pits 111 to 113 and the light reflected at the periphery of the pits 111 to 113 have an optical path difference according to the height of the pits 111 to 113, and are mutually π. Cause a phase difference of. Therefore, in the portion where there is a pit on the track, the reflected light from the pit and the reflected light from the periphery of the pit cancel each other out, and the reflected light becomes zero. On the other hand, in a portion without a pit, the irradiated light is reflected as it is and is incident on the distributed index lens 123.

The reflected light incident on the distributed index lens 123 becomes parallel rays and is received by the light receiving element 124. "1" and "0" of the data are identified by the presence or absence of the light received by the light receiving element 124, and the rotation angle of the servo motor is calculated from this data.

FIG. 2 is a view showing a data detection mechanism unit attached to the servo motor. Rotary encoder 10
0 is fixed to the bottom of the servomotor 200. An optical disk 110, on which data for detecting a rotation angle and the like is recorded, is fixed to a rotation shaft 210 of the servomotor 200. The optical systems 120 and 140 detect the recorded data by irradiating the optical disk 110 with a laser beam. The connector 101 is an optical system 12
0, 140 and a comparator (not shown) are electrically connected.

With this structure, when the rotary shaft 210 of the motor 200 rotates, the optical disk 110 also rotates. Along with this rotation, changes in the presence or absence of pits are detected in the optical systems 120 and 140. By transmitting the signal indicating the presence or absence of the pit to the comparator connected to the connector 101, the rotation angle of the rotation shaft 210 and the like are detected.

FIG. 3 is a top view of the data detection mechanism section.
The optical disk 110 is fixed to a rotary shaft 210 that rotates around the central axis O. On the upper surface of the optical disc 110, tracks 110a in which data is recorded by the pits 111 to 113 are provided. Truck 110
In a, pits are arranged at equal intervals in the circumferential direction.
A pit 110b for detecting one rotation is provided inside the track 110a.

Two optical systems 120 and 130 are provided for the track 110a. The optical system 120 and the optical system 130 are installed at positions shifted by 1/4 cycle when one cycle is set for a place with a pit and a place without a pit. The optical systems 120 and 130 are light sources 121 and 1 respectively.
31, the irradiation-side distributed refractive lenses 122 and 132, the light-receiving-side distributed refractive lenses 123 and 133, and the light-receiving element 12
It is composed of 4,134. Optical system 120, 130
Are arranged in parallel with the radial direction of the optical disc 110.

An optical system 140 is provided at a position where the pit 110b passes when the optical disc 110 rotates. The optical system 140 detects that the pit 110b has passed the position irradiated with the laser beam. The optical system 140 includes a light source 141 and a distribution refraction lens 14 on the irradiation side.
2, the light receiving side distributed refractive lens 143, and the light receiving element 1
And 44. Each element of the optical system 140 is arranged parallel to the radial direction of the optical disc 110.

FIG. 4 is a side view of the data detection mechanism section.
The optical disk 110 is fixed to a rotary shaft 210 having O-O ₀ as a central axis. The light sources 121 and 141, the distribution-side refraction lenses 122 and 142 on the irradiation side, the distribution-refraction lenses 123 and 143 on the light-receiving side, and the light-receiving elements 124 and 144.
The optical systems 120 and 140 configured by and irradiate the laser beams 125 and 145 from the oblique direction and receive the reflected light reflected obliquely.

By arranging the optical systems 120, 130, 140 on the optical disc 110 in this way, a signal having a period proportional to the rotation angle of the optical disc is detected from the optical systems 120, 130. The two signals are 90 degrees out of phase with each other. The optical system 140 detects one wavelength for each rotation of the optical disk. By analyzing these detected pulse signals, the rotary shaft 21
The rotation direction of 0, the rotation angle, etc. can be calculated.

FIG. 5 is a block diagram showing a detection signal analysis function. The signal input terminals A, B, C are connected to the connector 101 shown in FIG.
Signals from the optical systems 120, 130 and 140 are input to C, respectively.

The signal input terminals A, B and C are connected to the comparators 151 to 153, and the resistor R1
~ Grounded through R3. Comparator 151-
153 identifies "1" and "0" from the output of the detected signal, and outputs a pulse signal. Comparator 151,
The output side of 152 is both connected to the rotation direction detector 154 and the absolute position detector 155. Comparator 1
The output side of 53 is connected to the absolute position detector 155.

The rotation direction detecting section 154 has a comparator 1
The rotation direction is detected from the pulse signals from 51 and 152 which are 90 degrees out of phase with each other. The rotation direction can be detected by determining which pulse signal is advancing. The rotation direction signal indicating the detected rotation direction is transferred to the absolute position detection unit 155. Absolute position detector 155
Recognizes the rotation direction of the rotation axis from the rotation direction signal from the rotation direction detection unit 154, and recognizes the rotation angle from the pulse signals from the comparators 151 and 152. Further, the absolute position is calculated by calculating the rotation angle with reference to the time when one rotation signal indicating one rotation is input from the comparator 153. The calculation result is transferred to the controller of the rotary shaft of the servo motor.

With such a configuration, the comparator 15
The detection signals from the optical systems 120, 130, 140 converted into pulse signals of “1” and “0” by
First, the rotation direction is detected by the rotation direction detection unit 154 from the pulse signals output from the comparators 151 and 152. Next, the rotation angle and the absolute position are further detected by the pulse signal output from each of the comparators 151 to 153 and the rotation direction signal. Then, those data are transferred to the control circuit. In this way, the control circuit can accurately recognize the operating condition of the motor.

FIG. 6 is a diagram showing an example of the pulse signal output from the comparator. The phase of the pulse signal A ₁ output from the comparator 151 is 90 degrees in advance of the phase of the pulse signal B ₁ output from the comparator 152.
That is, the pulse signal A ₁ is a lead signal and the pulse signal B ₁ is a delay signal. The pulse signal C ₁ output from the comparator 153 is one rotation signal that outputs one pulse when the optical disk makes one rotation.

When such a pulse signal is detected, the rotation angle direction is obtained from the pulse signal A ₁ and the pulse signal B ₁ . That is, since the pulse signal A ₁ is a lead signal, it can be seen that the optical system 120 moves forward relative to the movement of the optical disc and the optical systems 120 and 130 (shown in FIG. 3). Therefore, in this case, the optical disk 110 shown in FIG. 3 is rotating clockwise.

The rotation angle of the optical disk depends on the pulse signal A
The number of pulses is ₁ . Further, the absolute position can be obtained by counting the number of pulse signals A ₁ after the pulse signal C ₁ is output.

As described above, since the rotation angle of the servo motor can be detected by reading the data recorded on the optical disk, a high resolution can be obtained. Moreover, since the pulse train is not phase-divided, a simple structure can be obtained.

Further, since the optical disc is provided with a polycarbonate protective film having a thickness of 1.2 μm on the data recording surface, even if some dust adheres to the film, the dust adheres to the film. The position and the data recording surface are sufficiently separated from each other, and there is little influence on the irradiation light to the pit and the reflected light from the pit. Therefore, the detected data becomes very accurate, and high reliability can be secured.

Further, by condensing light with the distributed index lens, the entire apparatus can be downsized. Below, the comparative example of the rotary encoder of this invention and the conventional rotary encoder is shown. In this comparative example, a case where phase division is performed by a conventional slit type rotary encoder is used as a reference, and comparison with other cases is performed.

The radius of the rotating disk (the distance from the center in the radial direction of the slit to the center of the disk) is 25 mm, and 20
When phase division is performed by a slit type rotary encoder having a rotating disk of 48 slits, a pulse train of 65536 pulses can be obtained by one rotation. At this time, the slit width (width of the opening portion or the light shielding portion) is 38.3 μm (1 pitch = 76.6 μm).

On the other hand, if an attempt is made to obtain a pulse train of 65536 pulses using only slits without phase division, the slit width will be 1.12 μm (1 pitch = 2.24 μm). This slit width is difficult to realize due to problems such as diffraction of transmitted light and dust.

On the other hand, in order to obtain a pulse train of 65536 pulses on an optical disc, an optical disc having pits having a circumferential length and a pitch of 1.2 μm is required. When the light beam used is infrared light (wavelength T = 300 nm), the pit length and spacing are 3T to 11T (0.9 μm to 3.3 μ).
m). Therefore, it is possible to sufficiently obtain a pulse train of 65536 pulses. Moreover, if the pit length and interval are set to the shortest (3T), the resolution can be further increased.

[0044]

As described above, in the present invention, the rotation angle of the rotary shaft and the like are detected by the optical disk and the optical system for reading the data recorded on the optical disk. Can be simplified,
Moreover, high resolution can be obtained.

[Brief description of drawings]

FIG. 1 is a diagram showing a data detection mechanism section of a rotary encoder of the present invention.

FIG. 2 is a diagram showing a data detection mechanism unit attached to a servomotor.

FIG. 3 is a top view of a data detection mechanism section.

FIG. 4 is a side view of a data detection mechanism section.

FIG. 5 is a block diagram showing an analysis function of a detection signal.

FIG. 6 is a diagram showing an example of a pulse signal output from a comparator.

FIG. 7 is a diagram showing a conventional rotary encoder.

[Explanation of symbols]

 110 Optical Discs 111-113, 110b Pits 120 Optical System 121 Light Sources 122, 123 Distributed Refractive Index Lens 124 Light-Receiving Element 125 Laser Light

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Office reference number FI technical display location G01D 5/30 S

Claims (9)

[Claims] 1. In a rotary encoder for detecting a rotation angle and the like, an optical disc mounted on a rotation shaft and provided with a track on which data for detecting the rotation angle is recorded, and the track is irradiated with a laser beam. A rotary encoder, comprising: an optical system including a laser light irradiating section for reading, and a light receiving section for reading the data by receiving reflected light from the track. 2. The rotary encoder according to claim 1, wherein data is recorded on the optical disk depending on the presence or absence of irregularities on a data recording surface. 3. The optical system comprises: the laser light irradiation unit that collects light by a distributed index lens; and the light receiving unit that receives reflected light by a distributed index lens. Rotary encoder. 4. The rotary encoder according to claim 1, wherein the optical system includes two sets of the laser light irradiator and the light receiver that detect signals that are 90 degrees out of phase with each other. 5. A rotary encoder for detecting a rotation angle and the like is provided with a track attached to a rotation shaft, in which angle data for detecting the rotation angle is recorded, and one rotation data for detecting one rotation. Angle detection comprising a read optical disc, a first laser beam irradiation unit for irradiating the track with laser light, and a first light receiving unit for receiving the reflected light from the track to read the angle data. Optical system for irradiating a laser beam on a path through which the rotation data passes
The one-rotation detecting optical system including: the laser light irradiating unit and the second light receiving unit that reads the rotation data by receiving the reflected light from the rotation data. 6. The rotary encoder according to claim 5, wherein the angle data and the one-rotation data are recorded on the optical disc depending on the presence or absence of unevenness on the data recording surface. 7. The angle detecting optical system includes a first laser light irradiation unit that collects light with a distributed index lens, and a first light receiving unit that receives reflected light with a distributed index lens. The rotary encoder according to claim 5, which is characterized in that. 8. The one-rotation detecting optical system includes a second laser light irradiation unit that collects light with a distributed index lens and a second light receiving unit that receives reflected light with a distributed index lens. The rotary encoder according to claim 5, wherein: 9. The angle detecting optical system is composed of two sets of the first laser light irradiating section and the first light receiving section for detecting signals whose phases are shifted by 90 degrees from each other. The rotary encoder according to claim 5.