JPH01118716A - Optical encoder - Google Patents

Abstract

PURPOSE:To reduce variation in pulse width with a pulse output by providing a reference light transmission part with slits, receiving light passed through them by one photodetecting element, and setting a reference output. CONSTITUTION:The light passed through slits AB0 and Z0 of a rotary disk 20 is passed through slit parts (A, B, and Z) for respective channels and the reference light transmission part (R), and converted photoelectrically by the photodetecting element. The transmission part R is provided with the slits R and generates an output opposite in phase from the slits A. Then the light passed through the slits A and R is received by the one photodetecting element and then the outputs are opposite in phase as shown in a figure (a), so their mean value is calculated to obtain a reference voltage RV. This reference voltage RV is compared with the outputs corresponding to the slits A, B, and Z to obtain pulse outputs of respective channels as shown in figures (b) and (c). In this case, the reference voltage RV also varies in proportion to variation in the output of the slit A, so variation in the pulse width of the pulse output is reduced.

Description

[Detailed Description of the Invention] [Industrial Field of Application] The present invention allows light that has passed through a slit in a rotating disk to pass through a slit section for each channel and a reference light transmitting section of a fixed slit, photoelectrically converts the light, and The present invention relates to an optical encoder that obtains a pulse output for each channel by comparing each channel output from a slit section for each channel that has undergone photoelectric conversion with a reference output from a reference transmission section.

[Prior art] Fig. 5 is a block diagram showing a conventional optical encoder.
FIGS. 6(a) and 6(b) are explanatory diagrams showing details of the rotating disk 22 and fixed slit 12 in FIG. 5, respectively;
7(a), (b), -, (f) are waveform diagrams showing signals from the light receiving element 40 of FIG. 5, and FIG. 8 is a comparison circuit of the conventional example circuit board 50 of FIG. It is a pulse output waveform diagram.

The circuit board 50 on which the light emitting element 30 is assembled is mounted on a support 60
It is fixed to the motor 80 by. The light receiving element 40 is fixed to the motor 80 facing the light emitting element 30, and a fixing slit 12 is provided in front of the light receiving element 40. The rotating disk 22 is attached to the motor shaft 70 so as to be located between the circuit board 50 and the fixed slit 12, and is rotated as the motor shaft 70 is rotated by the motor 80.

Next, regarding the operation of this conventional example, FIGS. 7(a), (b), -
, (f).

The rotating disk 22 has a circular shape and has a slit AB consisting of continuous thin slits along its outer periphery, and a slit Zo provided only at one location around the circumference. The fixed slit 12 includes slits A, B, and RW% Z that allow the light from the light emitting element 30 to pass through the slits ABO and Z. Further, behind the slits A, B, RW, and Z, there are light receiving elements 4 corresponding to each of the slits A, B, RW, and Z.
0 is set. Slit A and slit B are incremental slits, and are set so that changes in the amount of passing light are out of phase with each other by 90°. Unlike the slits A and B, the reference output slit RW is a large window, so it is not affected much by the rotation angle of the rotating disk 22 and allows a fairly constant scene to pass through. The slit Z for detecting the reference position is slit Z. Allows light to pass through when facing. Therefore, normally the rotating disk 22
The light that has passed through passes through slits A, B, RW, and Z, and is sent to the opposing light receiving elements 40, respectively, as shown in FIG. 7(a).
, (b) and (c). The comparison circuit of the circuit board 50 includes slits A, B,
Compare the output from Z with the output from slit RW, detect that the output from slits A and B%Z exceeds the reference voltage that is the output from slit RW, and set the pulse width T for each.
1°, "r2., 'r,." Pulse outputs are output as shown in FIG.

However, as can be seen from FIG. 1, an increase in the gap between the fixed slit 12 and the rotating disk 22 occurs due to elongation of the motor shaft 70 due to temperature rise or a thrust load on the load side of the motor shaft 70. When the gap increases, the output from slits A, B, and Z decreases, but the reference voltage from slit RW hardly decreases. Therefore, the range in which the output from slits A, B, and Z exceeds the output from slit RW is shown in Figure 7 (d). ), (e), (
f), and the comparator output also has a pulse width TI1
It becomes narrow like %TI2 and TI3, and in the worst case, no output is produced. A similar problem also occurs due to deterioration of the light generating element 30.

Figure 9(a) was devised to solve this problem.
, an optical encoder using a fixed slit 13 and a rotating disk 23 shown in (b),
FIGS. 10(a), 10(b), and 10(c) are waveform diagrams showing the operation, respectively.

The light from the light emitting element 30 that has passed through the slit AB of the rotating disk 23 is passed through the slits A'', A-, B'', and B-, and the light that has passed through the slits Zo''' and Zo- is sent through the slits Z' and 2, respectively. - through slit A", A-1
The transmitted light is received by light receiving elements 40 provided corresponding to B+, B-1Z+, and Z-, respectively. In this case, the output of slit A+ and the output of slit A- are 180
The two outputs are set to have different phases, and a reference output R1 is set from the two outputs. Output of slit B and output of slit B-, output of slit Z+ and slit Z
The relationship with the output of − is also similar. Base voltage R+, R2
, R3 are slits A+, A-1, and slit B, respectively.
, B-, slit z", z-, so if these outputs decrease, the reference voltage R,, R
2, R also decreases, making it difficult for the pulse width to change. However, this case is more complicated than the fixed slit 12 shown in FIG. 6(b).

[Problems to be Solved by the Invention] In the conventional optical encoder described above, when the gap between the fixed slit 12 and the rotating disk 22 changes, the pulse width of the output of the circuit board 50 also changes, or the pulse width changes. A device with less variation has the disadvantage that the fixed slit is complicated, the number of light receiving elements 40 corresponding to the fixed slit is increased, and the electric circuit is also complicated.

[Means for Solving the Problems] In the optical encoder of the present invention, the reference light transmitting section sets a reference output corresponding to the average value of each channel output independently or in cooperation with each channel output. It has a slit for

[Function] In this way, by providing a slit in the reference light passage section and setting the reference output with the light that has passed through the slit,
The reference output changes in proportion to the output of each channel. In other words, if slits in the same phase and opposite phase as the slits of the increment channel are provided in the reference light transmitting part, and one light receiving element receives the passing light, the average value of the output of each channel can be obtained. If a slit with a phase opposite to the slit of the incrementing channel is provided, an average value can be obtained from the output of the slit of the incrementing channel and the output of the slit with the opposite phase. Since these average values change in proportion to the output of each channel of the fixed slit, the change in the pulse width of the pulse output due to the comparison result between the reference output and each channel output becomes small.

[Embodiments] Next, embodiments of the present invention will be described with reference to the drawings.

FIGS. 1(a) and 1(b) are explanatory diagrams showing a rotating disk 20 and a fixed slit lO used in the first embodiment of the optical encoder of the present invention, respectively, and FIG. 2(a)
, (b) and (c) are waveform diagrams showing the operation of the first embodiment.

In this embodiment, a fixed slit IO is used in place of the fixed slit 12 shown in FIG. 6(b).

The rotating disk 20 is the same as that of the conventional example shown in FIG. 6, but the fixed disk 10 has a slit R instead of the slit RW, and this slit R generates an output in phase opposite to that of the slit A. Therefore, by averaging the outputs from slits A and R, the reference voltage RV is obtained.
By comparing the outputs from slits A, B, and Z, the pulse output of each channel can be obtained. Since the reference voltage RV also changes in proportion to the change in the output due to the slit A, changes in the pulse width of the pulse output are reduced. It can be seen that the number of light receiving elements 40 used is the same as in the conventional example shown in FIG.

FIG. 3 is an explanatory diagram showing details of the slit R formed in the fixed slit 11 used in the second embodiment of the present invention, and FIG. 4 (a), (b), (c), (d) are waveforms showing the operation of the second embodiment.

Different from the first embodiment, the slit R of the fixed slit 11 is provided with four types of slits a+, -, b", and b-. The slits a", a-1b", and b- are the same as the slit A, respectively. These slits a'', a-1b'', If the light passing through b- is received by one light receiving element 40, the slits a", a
It is possible to obtain a reference voltage RV corresponding to the average value of the outputs from -, b'', and b-.This reference voltage RV is closer to direct current than that of the first embodiment, and the error in each output is is canceled.By comparing this reference voltage RV with the outputs from slits A, B, and Z, the pulse output of each channel can be obtained.Then, the reference voltage RV
Since it corresponds to the average value of the outputs from the slits A and H, it changes in proportion to the change in the outputs from the slits A and B, so the change in the pulse width of the pulse output also decreases. In this case as well, the number of light receiving elements 40 is the same as in the conventional example shown in FIG.

In the second embodiment, the slit R has slits a+, a"',
Although the slits a+ and b- are provided, it is clear that only the slits a+ and a- or only the slits b+ and b- may be used.

- Furthermore, if the present invention is applied to an optical fiber encoder (reflective type, transmission type), the number of light emitting/receiving elements, optical fibers, and parts can be reduced, and a compact optical fiber encoder can be manufactured at low cost. It can also be used for reflective optical encoders and linear encoders (reflective type, transmission type, optical fiber type).

[Effects of the Invention] As explained above, the present invention provides a slit in the reference light transmitting section, receives the light passing through the slit with one light receiving element, and sets the reference output. Since it changes in proportion to the output of each channel, the change in the pulse width of the pulse output due to the comparison result between the reference output and each channel output can be effectively reduced without increasing the number of light receiving elements.

[Brief explanation of the drawing]

FIG. 1 is an explanatory diagram showing a rotating disk and fixed slit used in the first embodiment of the optical encoder of the present invention, and FIGS. 2(a), (b), and (c) are diagrams of the first embodiment. 3 is an explanatory diagram showing details of the fixed slit used in the second embodiment of the present invention, and FIGS. 4(a), (b), (c), and (d) are waveform diagrams showing the operation. FIG. 5 is a configuration diagram showing a conventional optical encoder, and FIGS. 6 (a) and (b) are explanations showing the rotating disk and fixed slit used in the conventional example. Figure 7 (a), (b), (c),
(d), (e), and (f) are waveform diagrams showing the operation of the conventional example, Fig. 8 is a waveform diagram showing normal pulse output of the circuit board 50 of the conventional example, and Fig. 9 is an improved conventional example. FIG. 10 is a waveform diagram showing the operation of a conventional example using the rotating disk 23 and fixed slit I3 in FIGS. 9(a) and 9(b). . 10.11...Fixed slit, 20...Rotating disk.

Claims (1)

[Claims] The light that has passed through the slit of the rotating disk is passed through the slit part for each channel of the fixed slit and the reference light transmitting part, and is photoelectrically converted, and each channel is converted by the slit part for each channel that has been photoelectrically converted. In an optical encoder that obtains the pulse output of each channel by comparing the output with the reference output from the reference transmission section, the reference light transmission section generates the reference output corresponding to the average value of each channel output independently or by using the standard output of each channel output. An optical encoder characterized by having a slit for setting in cooperation with either.