JP2002005692A - Optical encoder - Google Patents

Abstract

(57) [Problem] To convert an analog signal of a light receiving element into an electric signal, it is possible to remove a harmonic component other than a fundamental wave and to improve the division accuracy after multiplication. Provide an expression encoder. A fixed slit plate (5) is provided in an optical encoder that receives light from a light emitting element transmitted or reflected by a rotating slit by a light receiving element and detects the speed and the like of the rotating disk.
The shape of each of the fixed slits 61 formed in the fixed slit 6 among the four sides defining the boundary between the transparent portion and the light shielding portion
1 radially outer boundary 61A and radially inner boundary 61C
Are formed by an arc based on the rotation center of the rotating disk, and the circumferential boundaries 61B, 61B of the other fixed slit 6 are formed.
D represents straight lines 61E and 61 passing through the center of rotation of the rotating disk.
Assuming that the angle between F and F is θs, the circumferential boundaries 61B, 6 of the fixed slit 61 are within the range of 0 <θs <90 °.
1D was tilted.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention is, for example, mounted on a servomotor for driving a table of a machine tool or a robot, etc., and controls a rotation angle and a rotation speed by light transmitted through a slit provided in a rotary disk. The present invention relates to an optical encoder for detecting.

[0002]

2. Description of the Related Art Conventionally, an optical encoder mounted on a servomotor for driving a table of a machine tool or a robot is as shown in FIG. FIG. 1 is an overall perspective view showing a basic configuration common to the present invention and a conventional optical encoder. FIG. 6 is a schematic view of a fixed slit formed by a conventional optical encoder and a rotating disk superimposed and viewed from the front. 1 is an encoder, 2 is a rotating shaft, 3 is a rotating disk, 4 is a rotating slit which becomes a code pattern formed on the rotating disk 3, 42 is a transparent portion of the rotating slit, 42A is a light shielding portion, and 42B is a light shielding portion of the rotating disk 3. Boundary between transparent part and transparent part, 5 is fixed slit plate, 6,
62 is a fixed slit having a light receiving window formed in the fixed slit plate 5 corresponding to the rotary slit 4, 7 is a light emitting element such as an LED, 8 is a light receiving element, OO is the axis of the rotary shaft 2, P- P is an optical system composed of an optical path from the light emitting element 7 to the light receiving element 8. In the encoder 1 having such a configuration, when the rotating shaft 2 of the motor rotates, the rotating disk 3 made of glass or the like rotates integrally with the rotating shaft 2. When light from a light emitting element 7 such as an LED is incident on a rotating slit 4 formed in the rotating disk 3, light transmitted or reflected through the rotating slit 4 is received directly or through a fixed slit 6 by a light receiving element such as a photodiode. Recognize at 8. Then, the analog signal of the light receiving element 8 is converted into an electric signal amplified and adjusted by a circuit board (not shown), and then multiplied, interpolated, or pulsed to detect the rotation speed or the rotation position of the rotating disk 3 described above. is there.

[0003]

However, in the prior art, when the interval (pitch) between the fixed slit 6 or the rotating slit 4 and the slit of the light receiving element 4 is reduced in order to increase the resolution, the light is detected by the light diffraction phenomenon. The higher-order frequency components contained in the sinusoidal signal become large, causing distortion in the waveform. For this reason, when trying to multiply this analog signal by a multiplication circuit using a resistor bridge, the division accuracy of the output pulse is reduced. There is a problem that the division accuracy of the output data is reduced. The present invention has been made in order to solve the above-mentioned problem, and when converting an analog signal of a light receiving element into an electric signal, it is possible to remove a harmonic component other than a fundamental wave, and to achieve a division accuracy after multiplication. It is an object of the present invention to provide an optical encoder capable of improving the optical encoder.

[0004]

In order to solve the above problems, the present invention according to claim 1 comprises a light emitting element, a light receiving element having a light receiving surface facing all light emitting surfaces of the light emitting element, A fixed slit plate fixed to the light emitting element side and having a plurality of fixed slits serving as a light receiving window, and a plurality of rotating slits disposed between the light emitting element and the fixed slit plate and serving as a code pattern are formed. In the optical encoder for detecting the speed of the rotating disk, the rotational position by receiving the light from the light emitting element transmitted or reflected by the rotating slit by the light receiving element, the rotating disk, Each of the fixed slits formed on the slit plate has a fixed slit in which one of two sides in the radial direction is one of four sides defining a boundary between the transparent part and the light shielding part. The radially outer boundary and the radially inner boundary are formed by an arc based on the center of rotation of the rotary disk, and the other circumferential boundary of the fixed slit, which is the other two sides in the circumferential direction, is the rotary disk. 0 <θs <, where θs is the angle formed by a straight line passing through the rotation center of
The circumferential boundary of the fixed slit is inclined within a range of 90 °. The present invention of claim 2 is the invention of claim 1
In the optical encoder described above, among the four sides defining the boundary between the transparent portion and the light shielding portion of the rotary slit provided on the rotary disk, the circumferential slit of the rotary slit, which is two sides in the circumferential direction, is fixed to the fixed slit. Are relatively shifted with respect to the inclination angle of the circumferential boundary. The present invention according to claim 3 is a light-emitting element, a light-receiving element having a light-receiving surface facing all light-emitting surfaces of the light-emitting element, a plurality of light-receiving elements fixed to the light-emitting element side of the light-receiving element, and a light-receiving window A fixed slit plate having a fixed slit, and a rotating disk having a plurality of rotating slits disposed between the light emitting element and the fixed slit plate, and serving as a code pattern, having transmitted or reflected the rotating slit. In the optical encoder that detects the speed and the rotational position of the rotating disk by receiving the light from the light emitting element by the light receiving element, the shape of the light receiving section provided on the light receiving element is such that the light receiving section and the non-light receiving section Of the four sides that define the boundary of the part,
A radially outer boundary and a radially inner boundary of the light receiving portion, which are two sides in one radial direction, are formed by an arc based on the center of rotation of the rotating disk, and are two sides in the other circumferential direction. When the angle between the circumferential boundary of the light receiving portion and a straight line passing through the rotation center of the rotary disk is θs, 0 <θs
The circumferential boundary of the light receiving portion is inclined within a range of an angle of <90 °. According to a fourth aspect of the present invention, in the optical encoder according to the third aspect, of the four sides defining the boundary between the transparent portion and the light shielding portion of the rotating slit provided in the rotating disk, two sides in the circumferential direction are defined. The circumferential boundary of the rotating slit is shifted relative to the inclination angle of the circumferential boundary of the light receiving unit. The present invention according to claim 5 is a light-emitting element, a light-receiving element having a light-receiving surface facing all the light-emitting surfaces of the light-emitting element, and a plurality of light-receiving windows fixed to the light-emitting element side of the light-receiving element, and a light-receiving window A fixed slit plate having a fixed slit, and a rotating disk having a plurality of rotating slits disposed between the light emitting element and the fixed slit plate, and serving as a code pattern, having transmitted or reflected the rotating slit. By receiving light from the light emitting element by the light receiving element, in the optical encoder for detecting the speed and the rotational position of the rotating disk, the shape of the rotating slit provided in the rotating disk is a transparent part and a light shielding part. Of the four sides that define the boundary of
A radially outer circumferential boundary and a radially inner circumferential boundary of the rotating slit, which are two sides in one radial direction, are formed by an arc based on the rotation center of the rotating disk, and the other circumferential direction is defined by a circular arc.
The circumferential boundary of the rotating slit, which is a side, defines the circumferential boundary of the rotating slit in the range of 0 <θs <90 ° when an angle between the rotating slit and a straight line passing through the rotation center of the rotating disk is θs. It is inclined.

[0005]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. [First Embodiment] FIG. 2 is a schematic view of a fixed slit of an optical encoder according to a first embodiment of the present invention as viewed from the front. In addition, about the same component as this invention conventionally,
The same reference numerals are given and the description thereof will be omitted, and only different points will be described. In the figure, reference numerals 61A, 61B, 61C, and 61D denote boundaries between the light-shielding portion and the transparent portion of the fixed slit 61.
1A is an outer peripheral radial boundary line of the fixed slit, 61C is an inner peripheral radial boundary line of the fixed slit, 61B and 61D are peripheral boundary lines of the fixed slit, 61E and 6D.
1F is a straight line passing through the center of rotation of the rotary disk 3, LP is an arc defining the inclination of the fixed slit, SP is the slit pitch of the optical encoder, and θs is the inclination of the circumferential boundary of the fixed slit. The configuration in which the present invention is different from the conventional one is as follows. That is, the fixed slit plate 5
The shape of each of the fixed slits 61 formed on one of the four sides defining the boundary between the transparent portion and the light-shielding portion is one of the two sides in the radial direction.
And the radially inner peripheral side boundary 61C is formed by an arc based on the rotation center of the rotary disk 3, and the circumferential boundary 61 of the fixed slit 61, which is the other two sides in the circumferential direction.
B and 61D are inclined in an angle range of 0 <θs <90 °, where θs is an angle formed by a straight line passing through the rotation center of the rotary disk 3. Next, the operation of the optical encoder will be described with reference to FIGS. FIG. 3 is a schematic view of the fixed slit shown in FIG. 2 and the rotating disk superimposed and viewed from the front, FIG. 4 is a layout diagram of fixed slits necessary for explaining the operation of the present invention, and FIG. Shows a waveform when converting the analog signal into an electric signal,
(A) is a fundamental wave, (b) is a third harmonic (c) composite wave. In FIG. 3, reference numeral 41 denotes a transparent portion of the rotating slit provided on the rotating disk, 41A denotes a light shielding portion of the rotating slit provided on the rotating disk, and 41B denotes a boundary between the transparent portion 41 and the light shielding portion 41A. Here, for the sake of convenience, the arc pitch LP shown in FIG.
To represent the magnitude of the inclination theta _S with an angle ratio of the. That is, the arc LP is 1/6 of the slit pitch SP.
The electrical angle is 360 と な り 6 = 60 °,
The circumferential boundaries 61B and 61D of the fixed slits are defined as straight lines 61E and 61F passing through the center of rotation of the rotating disk, in other words, forming a slope of 60 ° with the circumferential boundary of the conventional fixed slit. Under such conditions, as the rotating disk rotates, the light passing through the fixed slit includes the third harmonic, and the fundamental wave and the third harmonic are respectively

[0006]

(Equation 1)

The output P due to the light passing through the fixed slit is

[0008]

(Equation 2)

## EQU1 ## Next, in FIG. 4, there is a fixed slit 61 in which the angle ratio between the arc LP and the slit pitch SP is 1: 6, and the inclination θs of the circumferential boundary line of the fixed slit is defined as 60 °. Up and down 2
Consider equally divided units (61U, 61L). Since the two fixed slits 61U and 61L have a phase difference of 60 °, the output of the entire fixed slit 61 is the same as that in which half of the output P is added with a phase difference of 60 °. Output of slit 61U is P2, slit 61L
Assuming that the output of P3 is P3, FIG.

[0010]

(Equation 3)

As a result, the third harmonic can be canceled. The same applies to the other orders (5, 7... Orders), and the inclination θs is set to 180/5 = 36 °, 18
If 0/7 = 25.7 °, each harmonic can be canceled. Also, since the ninth harmonic is an odd multiple of the third harmonic, if the inclination θ _S is set to 60 °, the third, ninth, and 15th harmonics need not be set.
Next. . . Harmonics can be canceled. In addition, by simulating a waveform that can be extracted by changing the inclination θ _S , it is understood that setting the inclination to 1 rad (= 57.3 °) effectively removes harmonics other than the fundamental wave. Therefore, among the four sides defining the boundary between the transparent portion and the light-shielding portion in each fixed slit formed in the fixed slit plate of the optical encoder, the circumferential direction boundary of the fixed slit, which is two sides in the circumferential direction, and the rotating disk 0 <θs, where θs is the angle formed by a straight line passing through the rotation center of
Since the circumferential boundary of the fixed slit is inclined in the range of <90 °, when converting an analog signal of the light receiving element into an electric signal, a good waveform that does not include a harmonic component other than the fundamental wave can be obtained. It is possible to provide an optical encoder which can take out and improve the division accuracy after multiplication. [Second Embodiment] The second embodiment is different from the first embodiment in that the fixed slit 61 shown in FIGS. 2 and 3 is inclined with respect to straight lines 61E and 61F passing through the rotation center of the rotary disk. In addition to the configuration, although not shown directly, of the four sides defining the boundary between the transparent portion 41 and the light shielding portion 41A of the rotary slit 4 on the rotary disk, two circumferential edges of the rotary slit (41B) Is relatively shifted with respect to the inclination angles of the circumferential boundaries 61B and 61D of the fixed slit 61. Since the operation is basically the same as that of the first embodiment, a description thereof will not be repeated. Thereby, when converting the analog signal of the light receiving element into an electric signal, it is possible to approximate a sine wave that does not include a harmonic component other than the fundamental wave, and it is possible to improve the division accuracy after the multiplication. [Third Embodiment] The third embodiment is different from the first embodiment in that the fixed slit 61 shown in FIG. 2 is inclined with respect to straight lines 61E and 61F passing through the center of rotation of the rotary disk. Alternatively, although not shown directly, of the four sides defining the boundary between the light receiving portion and the non-light receiving portion provided in the light receiving element 8,
A radially outer boundary and a radially inner boundary of the light receiving portion, which are two sides in one radial direction, are formed by an arc based on the center of rotation of the rotating disk 3 and are two sides in the other circumferential direction. When the angle formed between the light receiving section and the straight lines 61E and 61F passing through the rotation center of the rotating disk is θs,
The point is that the circumferential boundary of the light receiving unit is inclined in the range of <θs <90 °. Further, in such a configuration, although not shown, the circumferential boundary of the rotating slit, which is two sides in the circumferential direction, among the four sides defining the boundary between the transparent portion and the light shielding portion of the rotating slit provided on the rotating disk. May be shifted relative to the inclination angle of the circumferential boundary of the light receiving unit. Since the operation is basically the same as that of the first embodiment, a description thereof will not be repeated. Similarly, the analog signal of the light receiving element can be approximated to a sine wave, and the division accuracy after the multiplication can be improved. [Fourth Embodiment] The fourth embodiment is different from the first embodiment in that the fixed slit 61 shown in FIG. 3 is inclined with respect to a straight line passing through the center of rotation of the rotary disk 3. Although not shown directly, among the four sides defining the boundary between the transparent portion 41 and the light-shielding portion 41A of the rotating slit provided on the rotating disk 3, one of the two sides in the radial direction is a radial outer circumferential boundary of the rotating slit. And the radially inner circumferential side boundary is formed by an arc based on the rotation center of the rotating disk 3, and the circumferential boundary of the rotating slit 41 which is the other two sides in the circumferential direction is:
The angle formed by a straight line passing through the center of rotation of the rotating disk 3 is θ
When s is set, the circumferential boundary of the rotary slit 3 is inclined within the range of 0 <θs <90 °. Since the operation is basically the same as that of the first embodiment, a description thereof will not be repeated. Similarly, the analog signal of the light receiving element can be approximated to a sine wave, and the division accuracy after the multiplication can be improved. Incidentally, the optical encoder of the present invention,
Although the rotary type has been described, it may be applied to a linear optical encoder, and the diameter of the encoder can be considered to be infinite, so the description is omitted.

[0012]

As described above, according to the present invention, the boundary between the transparent portion and the light shielding portion in each fixed slit formed in the fixed slit plate of the optical encoder is defined.
When the angle between the circumferential boundary of the fixed slit, which is the two sides in the circumferential direction, and the straight line passing through the center of rotation of the rotary disk is θs, the angle is fixed in the range of 0 <θs <90 °. The slit is configured so that the circumferential boundary of the slit is inclined, so that when converting the analog signal of the light receiving element to an electric signal, it is possible to extract a good waveform that does not include harmonic components other than the fundamental wave, and to perform division after multiplication. An optical encoder that improves the accuracy can be provided.

[Brief description of the drawings]

FIG. 1 is an overall perspective view showing a basic configuration common to the present invention and a conventional optical encoder.

FIG. 2 is a schematic view of a fixed slit showing the first embodiment of the present invention as viewed from the front.

FIG. 3 is a schematic view of the fixed slit and the rotating disk shown in FIG.

FIG. 4 is a layout diagram of fixed slits necessary for explaining the operation of the present invention.

5A and 5B show waveforms when an analog signal of a light receiving element is converted into an electric signal, wherein FIG.
(B) is the third harmonic (c) is a composite wave.

FIG. 6 is a schematic view of a fixed slit formed by a conventional optical encoder and a rotating disk superimposed and viewed from the front.

[Explanation of symbols]

 Reference Signs List 1 encoder 2 rotating shaft 3 rotating disk 4 rotating slit 41 transparent portion of rotating slit 41A light shielding portion of rotating slit 41B boundary between light shielding portion and transparent portion of rotating disk 5 fixed slit plate 6 fixed slit 61 fixed slit 61A outer diameter of slit Directional boundary line 61B Peripheral boundary line of fixed slit 61C Inner peripheral radial boundary line of fixed slit 61D Peripheral boundary line of fixed slit 61E Straight line passing through the rotation center of rotating disk 61F Straight line passing through the rotating center of rotating disk 61U 2 Outer peripheral side of divided transparent part 61L 2 Inner peripheral side of divided transparent part 7 Light emitting element 8 Light receiving element LP Arc that defines the inclination of slit SP Slit pitch of encoder θs Inclination of circumferential boundary line of fixed slit

Claims (5)

[Claims] 1. A light-emitting element, a light-receiving element having a light-receiving surface facing all light-emitting surfaces of the light-emitting element, and a plurality of fixed slits fixed to the light-emitting element side of the light-receiving element and serving as a light-receiving window. The fixed slit plate formed, the light emitting element disposed between the light emitting element and the fixed slit plate, and a rotating disk having a plurality of rotating slits to be a code pattern, the light emitting element transmitted or reflected through the rotating slit In the optical encoder that detects the speed and the rotational position of the rotating disk by receiving light from the light receiving element, the shape of each fixed slit formed in the fixed slit plate is a transparent portion and a light shielding portion. Of the four sides that define the boundary of
The radially outer peripheral boundary and the radially inner peripheral boundary of the fixed slit, which are one of the two sides in the radial direction, are formed by an arc based on the rotation center of the rotary disk, and the other two sides in the circumferential direction. The circumferential boundary of the fixed slit is inclined at an angle of 0 <θs <90 ° when the angle between the fixed slit and a straight line passing through the center of rotation of the rotating disk is θs. An optical encoder, characterized in that: 2. A four-sided boundary defining a boundary between a transparent portion and a light-shielding portion of a rotary slit provided on the rotary disk, a circumferential boundary of the rotary slit, which is two sides in a circumferential direction, is defined by a circumferential direction of the fixed slit. The optical encoder according to claim 1, wherein the optical encoder is shifted relative to the inclination angle of the direction boundary. 3. A light-emitting element, a light-receiving element having a light-receiving surface facing all light-emitting surfaces of the light-emitting element, and a plurality of fixed slits fixed to the light-emitting element side of the light-receiving element and serving as a light-receiving window. The fixed slit plate formed, the light emitting element disposed between the light emitting element and the fixed slit plate, and a rotating disk having a plurality of rotating slits to be a code pattern, the light emitting element transmitted or reflected through the rotating slit In the optical encoder for detecting the speed and rotation position of the rotating disk by receiving light from the light receiving element with the light receiving element, the shape of the light receiving part provided in the light receiving element is a boundary between the light receiving part and the non-light receiving part. Of the four sides that define
A radially outer boundary and a radially inner boundary of the light receiving portion, which are sides, are formed by an arc based on the rotation center of the rotating disk, and a circumferential boundary of the light receiving portion, which is the other two sides in the circumferential direction. Is the angle θs with the straight line passing through the center of rotation of the rotating disk.
Wherein the circumferential boundary of the light receiving portion is inclined within a range of 0 <θs <90 °. 4. The four sides defining the boundary between the transparent portion and the light-shielding portion of the rotating slit provided on the rotating disk, and the circumferential boundary of the rotating slit, which is two sides in the circumferential direction, is defined by the circumference of the light receiving portion. The optical encoder according to claim 3, wherein the optical encoder is shifted relative to the inclination angle of the direction boundary. 5. A light-emitting element, a light-receiving element having a light-receiving surface facing all light-emitting surfaces of the light-emitting element, and a plurality of fixed slits fixed to the light-emitting element side of the light-receiving element and serving as a light-receiving window. The fixed slit plate formed, the light emitting element disposed between the light emitting element and the fixed slit plate, and a rotating disk having a plurality of rotating slits to be a code pattern, the light emitting element transmitted or reflected through the rotating slit By receiving light from the light receiving element by the light receiving element, in the optical encoder for detecting the speed of the rotating disk, the rotational position, the shape of the rotating slit provided in the rotating disk,
Of the four sides that define the boundary between the transparent part and the light-shielding part, the radially outer peripheral side boundary and the radially inner peripheral side boundary of the rotating slit, which are two sides in one radial direction, are based on the rotation center of the rotary disk. The circumferential boundary of the rotating slit, which is formed by the circular arc and forms the other two sides in the circumferential direction, is 0 <θs <90 ° when an angle between the rotating slit and a straight line passing through the center of rotation of the rotating disk is θs. An optical encoder wherein a circumferential boundary of the rotary slit is inclined within an angle range.