JPS62240814A - Optical encoder - Google Patents

Abstract

PURPOSE:To obtain a device dispensing with machining of a slit by a method wherein a slit being substantially parallel to a rotating shaft is formed by a rotary body fitting eccentrically to the rotating shaft and a restricting plate disposed separately from the rotary body. CONSTITUTION:A slit 4 being parallel to a rotating shaft 2 is formed between a rotary body 1 fitted eccentrically to the rotating shaft 2 and a restricting plate 3. A beam of light emitted from a light-emitting element 6 is diffracted at the edge of the opening of the slit 4, the intensity of the beam becomes maximum on the optical axis of the light-emitting element 6, and a number of peaks are obtained also in portions being separate from the optical axis, due to the mutual interference of beams diffracted at the opposite edges of the opening of the slit 4. Since the light-emitting element 6 is constituted by a semiconductor laser 5, the wavelength of the light emitting therefrom is fixed, and only the width of the slit 4 is varied with the rotation of the rotary body 1. A photodiode 8 of a light-receiving element 9 is disposed at a position deviated from the optical axis of the laser 5 of the light-emitting element 6, and the intensity of the received light is varied in accordance with the rotational angle of the rotary body 1. The output of said diode 8 is subjected to wave shaping, and a pulse obtained thereby can be used for control and measurement.

Description

[Detailed Description of the Invention] [Technical Field] The present invention relates to an optical encoder, more specifically, a servo 8
This invention relates to an optical 7-type encoder used to detect the position and speed of a device in a robot, machine tool, recorder, etc. that has a feedback control system such as a robot, machine tool, recorder, etc.

[Background Art] Generally, as this type of optical type encoder, a rotary encoder as shown in FIG. 4 and a linear encoder as shown in FIG. 6 are known.

As shown in FIG. 4, the rotary encoder includes a code wheel 13 (see FIG. (a)) and code wheel 1
7 aids plate 15 (ff$5 figure (
b)), a light emitting element 16 that emits light toward the code wheel 13, and the code wheel 13 and 7 aids plate 1.
5) and a light receiving element 17 that receives the light transmitted through the sleeve 12.14. In this rotary encoder, when the code wheel 13 rotates together with the rotary shaft 11, the code wheel 13 and the 7-AIDS plate 15 cut off the signal from the light emitting element 16! The light-receiving element 17 detects a change in the amount of light when the light is rotated, and the rotation angle and rotation speed of the rotating shaft 11 are detected based on this amount of change.

On the other hand, as shown in FIG. 6, the linear encoder moves back and forth from side to side, and is positioned at a fixed position parallel to the main scale 22, in which a large number of slits 21 are formed at a predetermined pitch. An index scale 2 that is fixed and has M number of slits (not shown) periodically formed at positions corresponding to the slits 21.
3, and a light source 24 that emits light toward the main scale 22.
and a light receiving element 27 that receives the light transmitted through the slit 21 of the main scale 22 and the index scale 23. This linear encoder uses a light receiving cable 27 to detect changes in the amount of light when the light from the light emitting WB 26 is interrupted by the main scale 21 and the index scale 23 as the main scale 21 moves in the left-right direction. Based on this amount of change, the amount and speed of movement of the main scale 21 are detected.

By the way, in order to improve the detection accuracy (resolution e, >) of such an optical encoder, it is necessary to
2 and the pickpocket 7 formed on the index scale 23
) 12 (14, 21) number or pickpocket 7) 12 (14, 2
It is necessary to improve the dimensional accuracy of 1). As a method for manufacturing the slit 12 (14, 21) that satisfies the requirements for accuracy, a method shown in FIG. 7 (ttS8) has been considered. That is, in the method shown in FIG. 7, after depositing a metal layer 32 such as chromium on a transparent glass substrate 31 (
Figure (b)), 7 otorenost layers 33 on the surface of the metal layer 32
After forming a mask 34 with a slit pattern and exposing it to light (W & 7 (C)), etching (Fig. 7 (d)), N33 is removed (
tIS7 (C)), and the method shown in FIG.
After forming the 7-otrenost layer 36 on the thin metal plate 35 (
FIG. 8(b)), mask 3 with a slit pattern
8 (c)), etching (ffi 8 (d)), and then removing the 7 photoresist M36 (Fig. 8 (e)).
:lS7 In the method shown in the figure, the metal layer 3 on the glass substrate 31 is
2, the slit 12 (14, 21) force f is formed, and in the method shown in FIG.
4121) is formed. When forming slits 7) 12 (14, 21>) using these processing methods, chemical treatments such as etching are required in either case, which complicates the processing process and increases manufacturing costs. There is a problem.

[Objective of the Invention 1 The present invention has been made in view of the above-mentioned α, and its main object is to provide an optical encoder that does not require slit processing.

[Disclosure of the Invention] (Structure) The optical encoder according to the present invention includes a plate-shaped rotating body having an appropriate thickness and eccentrically attached to a rotating shaft, and a plate-shaped rotating body that is spaced apart from the circumferential surface of the rotating body and placed in a fixed position. R-
By detecting the rotation angle and rotation speed of the rotating body based on changes in the slit width between the rotating body and the aperture plate, machining of the slit is not required.

(Example) Hereinafter, an example of the present invention will be described based on the drawings. 1st
As shown in the figure, a rotating shaft 2 is fixed perpendicularly to the surface of a plate-shaped rotating body 1 having an appropriate thickness, and the rotating body 1 rotates together with the rotating shaft 2.

The rotating body 1 is circular, and the rotating shaft 2 is attached slightly eccentrically from the center of the rotating body 1. A diaphragm plate 3 is disposed on the circumferential portion of the rotary body 1 so as to be spaced apart from the circumferential surface of the rotary body 1 in the radial direction of the rotary body 1 . The aperture plate 3 is fixed at a fixed position on a casing or the like, and has a knife edge on the rotating body 1 side, and a slit 4 parallel to the rotation axis 2 is formed between the curve of the rotor 1 and the tip edge of the aperture plate 3. form. Therefore, when the rotating body 1 rotates, the peripheral surface of the rotating body 1 and the tip of the aperture plate 3 jI
By changing the distance of darkness from Ait, slit 4
width changes. Here, the amount of eccentricity between the center of the rotating body 1 and the center of the rotating shaft 2, and the distance between the circumferential surface of the carrier body 1 and the tip edge of the crest plate 3 are such that the width of the slit 4 is about the wavelength of light. It is set up in such a relationship. A light emitting section 6 consisting of a semiconductor laser 5 and a light receiving section 9 consisting of a condensing lens 7 and a V7 autodiode 8 are sandwiched across the opening surface of the slit 4.
are opposed. The optical axis of the semiconductor laser 5 is perpendicular to the aperture surface of the slit 4, and the optical axis of the seven otodiodes 8 is arranged at a position offset from the optical axis of the semiconductor laser 5. Therefore, the light receiving section 9 receives the light beam emitted from the light emitting section 6 and diffracted by the slit 4.

(Operation) The operation will be explained below.The light emitted from the light emitting part 6 is diffracted at the opening edge of the slit 4, so the distance from the optical axis of the light emitting part 6 is determined horizontally, and the intensity of the diffracted light is determined vertically. Then, the intensity distribution of the diffracted light passing through the slit 4 is as shown in the f:IS2 diagram. That is, the intensity of the light beam transmitted through the slit 4 is maximum on the optical axis of the light emitting part 6, and many peaks also occur in areas far from the optical axis due to interference between the light beams diffracted at both edges of the opening of the slit 4. is obtained. This peak is
If the order of the spectrum is the order of the spectrum, λ is the wavelength, d is the diffraction grating constant (width of the slit), and φ1 is the angle of the diffracted light with respect to the optical axis centered at the position of slit 4, then nλ = d-sin
It is obtained at the position where the relationship φmugi is established.

Here, since the light emitting section 6 is composed of the semiconductor laser 5, the wavelength is constant, and only the width of the slit 4 changes as the rotating body 1 rotates. That is, as shown by the broken line in FIG. 2, the distance from the optical axis to the peak position of the diffracted light changes in accordance with the change in the width of the slit 4 in areas other than the optical axis. Since the 7-otodiode 8 is disposed at a position offset from the optical axis of the semiconductor laser 5 of the light emitting section 6, the received light intensity at the 7-otodiode 8 depends on the rotation of the rotating body 1, as shown in FIG. It changes depending on the angle. Pulses can be obtained by waveform shaping the output of these 7 Otodiodes, which can be used for control and measurement in the same way as conventional optical encoders.

Further, since the resolution can be set according to the change in the opening width of the slit 4, it can be set appropriately according to the eccentricity of the rotating shaft 2 with respect to the rotating body 1.

[Effects of the Invention] As described above, the present invention includes a plate-shaped rotating body having an appropriate thickness and eccentrically attached to a rotating shaft, and a rotating body disposed at a fixed position apart from the circumferential surface of the rotating body. A diaphragm plate that forms a slit approximately parallel to the rotational axis between the circumferential surface of the WIJ! : Since the light emitting part and the light receiving part are set at λ, the rotation angle and rotation speed of the rotating body can be detected by changing the slit width between the rotating body and the diaphragm plate, which is different from the conventional method. There is an advantage that manufacturing costs can be reduced because such slit processing is not necessary.

Furthermore, any desired resolution can be obtained by simply managing the amount of eccentricity of the rotating shaft with respect to the rotating body, which has the advantage of facilitating design.

[Brief explanation of drawings]

Fig. 1 is a schematic configuration diagram showing one embodiment of the present invention, Figs. 2 and 3 are explanatory diagrams of the same operation as above, Fig. 4 is a side view showing a conventional rotarienhug, and Fig. 5 (a )(b) is a front view showing a code wheel and a 7-Aze plate used in the same as above, and FIG. 6(, )(b) is a perspective view and a plan view showing a conventional linear encoder, respectively.
7 and 8 are process diagrams showing a conventional slit processing method, respectively. 1 is a rotating body, 2 is a rotating shaft, 3 is a diaphragm plate, 4 is a slit,
5 is a semiconductor laser, 6 is a light emitting section, 7 is a condensing lens, 8 is an otodiode, and 9 is a light receiving section. Agent Patent Attorney Ishi 1) Ai 7 Figure 1 Figure 2 Figure 4 Figure 5 Figure 6 and r Figure 7 (G) 2 31 Figure 8

Claims (1)

[Claims] (1) A rotating ring is formed between a plate-shaped rotating body having an appropriate thickness and attached eccentrically to the rotating shaft, and the circumferential surface of the rotating body, which is arranged at a fixed position apart from the circumferential surface of the rotating body. An optical encoder comprising: an aperture plate forming substantially parallel slits; and a light emitting section and a light receiving section placed opposite to each other across the slit.