JPH10206189A - Sine wave encoder - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an encoder to which heat and vibrations are not directly transmitted from a motor and which nearly eliminates an adjustment in assembling even if it is formed compact. SOLUTION: The light from a light source 3 irradiates a rotary polarizer 2, so that the light conforming to a plane of polarization is passed. The passed light is reflected at a reflecting mirror 1, passes through the rotary polarizer 2 and hits fixed analyzers 4a-4d. The amount of each light passing through the fixed analyzer 4a-4d and detected at a photodetector 5a-5d corresponds to an angular shift of planes of polarization of the rotary polarizer 2 and the fixed analyzer 4a-4d. That is, the amount changes in the form of a sine wave in accordance with the rotation of the rotary polarizer 2, whereby sine wave signals Sa-Sd of two cycles are obtained per one rotation of the rotary polarizer 2. Output signals of A, B two phases of a 90 deg. phase difference which are stable without influences by a temperature change or noises of optical parts, etc., are obtained by obtaining a difference of the sine wave signals Sa and Sc, and Sb and Sd.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an encoder for detecting a rotation angle or a position.

[0002]

2. Description of the Related Art In addition to magnetic encoders and resolvers, many optical encoders as shown in FIG. 4 are used as encoders for measuring a rotation angle or a position. The optical encoder is mounted on a shaft 17 to be measured and has a rotating disk 12 having bright and dark slits 11 at equal intervals, a light source 13 provided at a position opposed to the slits 11, and a slit 11. A fixed disk 15 having a plurality of fixed slits 14 having a same pitch with the slit portion 11 on the opposite side and having different phases from each other.
And a plurality of light receiving elements 16 provided in the fixed slit 14 in one-to-one correspondence.

Light emitted from a light source 13 passes through a slit portion 11 and a fixed slit 14 and reaches a light receiving element 16. The light receiving element 16 can obtain a sinusoidal electric signal according to a change in the angle of the object to be measured. The angle or position can be measured by measuring the phase of the sine wave signal or counting / measuring the period.

[0004]

In a conventional encoder having such a structure, the space between the rotating slit and the fixed slit is generally narrow, and the shaft of the object to be measured such as a motor and the shaft having the rotating slit are mounted. Is directly connected, so that vibration and heat from the motor side are directly transmitted through the shaft. Due to this temperature rise and vibration, optical components such as light sources and light receiving elements, rotating disks and fixed disks, and electronic components of signal processing circuits, etc. are damaged or deteriorated.
There were problems such as lack of reliability as a sensor. In addition, as the size becomes smaller, mechanical accuracy such as the eccentricity of the shaft 17 and the rotating disk 12 is required, and high-precision assembly,
There were problems such as the need for adjustment.

Japanese Patent Application Laid-Open No. Hei 8-170965 discloses a method of irradiating a rotating surface having a large number of fine grooves aligned in a certain direction with a laser beam to obtain an interference fringe rotating at the same cycle as the rotating surface. The degree of freedom of the fixed position between the light-emitting side and the light-receiving side is expanded by measuring the rotation of the rotating surface by receiving light with the photoelectric conversion element, but the device is expensive and the life is short because laser light is used. There is a disadvantage that.

SUMMARY OF THE INVENTION An object of the present invention is that heat and vibration are not directly transmitted, and even if made small, there is almost no need for adjustment at the time of assembly, the structure is simple, the reliability and durability are excellent, and the cost is low. To provide a simple encoder.

[0007]

The encoder according to the present invention comprises:
A reflecting mirror attached to the end face of the rotation axis of the device under test, a rotating polarizer provided on the reflecting mirror, a light source for irradiating diffused light toward the rotating polarizer, and a rotating polarizer. First and second polarizers, which are provided to face each other, are transmitted by the rotating polarizer, are reflected by the reflecting mirror, and are illuminated by the diffused light transmitted by the rotating polarizer.
, And first and second light receiving elements for receiving light passing through the first and second fixed analyzers, respectively.

The light emitted from the light source is applied to a rotating polarizer attached to the axis end of the object to be measured, and only the light existing on the polarization plane of the polarizer is transmitted. The transmitted light is reflected by a reflecting mirror, passes through a rotating polarizer, and is disposed around the light source, and strikes a fixed analyzer having a polarization plane different from each other by 45 °. The light passing through each fixed analyzer and detected by the light receiving element is converted into an electric signal, and a sine wave signal of two periods can be obtained for one rotation of the rotating polarizer (the polarization plane is rotated by 180 ° rotation). Because it will be in the same state as before). The rotation angle can be detected by measuring the phase of the sine wave signal or by counting the period.

In the present invention, the distance between the rotating polarizer and the fixed analyzer can be made sufficiently large, and there is no sensor shaft as in the conventional example, so that heat or vibration from an object to be measured such as a motor can be directly transmitted. In addition, damage and deterioration of optical components and electronic circuit components are unlikely to occur. In addition, since the magnitude of the detection signal is determined only by the angle between the polarization plane of the rotating polarizer and the fixed analyzer, the size of the light to be irradiated should be extremely small if it hits the rotating polarizer. Also, there is no need to adjust the alignment of the rotating slit and the fixed slit as in the conventional example, and the handling is easy. Furthermore, since a rotating polarizer and a fixed analyzer are used, the cost is lower than when laser light is used.

According to the embodiment of the present invention, the first and second fixed analyzers are provided on the same plane, the angles of the polarization planes are different from each other by 45 °, and the first and second fixed analyzers are 90 ° apart from each other. °
It further has different third and fourth fixed analyzers, and third and fourth light receiving elements that respectively receive light passing through the third and fourth fixed analyzers. By taking the difference between the detection signal of the first and second light receiving elements and the detection signal of the third and fourth light receiving elements, even if the detection signal contains noise, the signal obtained by taking the difference becomes Noise is not included, and a stable A and B two-phase signal having a phase difference of 90 ° without the influence of noise is obtained.

[0011]

Next, embodiments of the present invention will be described with reference to the drawings. 1 is a configuration diagram of a sine wave encoder according to an embodiment of the present invention, FIG. 2 is a configuration diagram of fixed analyzers 4a to 4d in FIG. 1, and FIG. 3 is a waveform diagram of signals obtained by light receiving elements 5a to 5d. is there.

The sine wave encoder according to the present embodiment comprises a reflecting mirror 1, a rotating polarizer 2, a light source 3, a fixed analyzer plate 4, and a light receiver 5.
It is composed of The reflecting mirror 1 is mounted on the end face of the rotating shaft 6 of the device under test, and the rotating polarizer 2 is mounted on the reflecting mirror 1. The light source 3 irradiates the diffused light toward the rotating polarizer 2. The fixed analyzer plate 4 is provided so as to face the rotating polarizer 2, and passes through the rotating polarizer 2, is reflected by the reflecting mirror 1, and is irradiated with diffused light passing through the rotating polarizer 2. To 4d are attached. The straight lines in the fixed analyzers 4a to 4d in FIG. 2 indicate the polarization planes, and the fixed analyzers 4a and 4b have the polarization plane angles shifted by 45 ° from each other, and the fixed analyzers 4c and 4d have the polarization plane angles of 45 ° deviation,
The fixed analyzers 4a and 4c have a polarization plane angle of 90 ° with respect to each other, and the fixed analyzers 4b and 4d have a polarization plane angle of 90 ° with each other.
° is off. The light receivers 5 are respectively fixed analyzers 4a to 4a.
It comprises light receiving elements 5a to 5d that receive light passing through 4d and convert the light into electric signals.

The light emitted from the light source 3 is applied to the rotating polarizer 2, and only the light existing on the polarization plane is transmitted. The transmitted light is reflected by the reflecting mirror 1, passes through the rotating polarizer 2, and strikes the fixed analyzers 4a to 4d. The amounts of light that pass through the fixed analyzers 4a to 4d and are detected by the light receiving elements 5a to 5d are the amounts of light corresponding to the deviations of the polarization plane angles of the rotating polarizer 2 and the fixed analyzers 4a to 4d, that is, the rotating polarizer 2 The sinusoidal signals Sa to Sd of two periods are obtained for one rotation of the rotating polarizer 2 as shown in FIG. By taking the differential between the sine wave signals Sa and Sc, and Sb and Sd, it is possible to obtain stable A and B two-phase output signals having a 90 ° phase difference without the influence of temperature fluctuations of optical components and the like and noise. Obtainable.

The fixed analyzers 4a and 4b or 4c
And 4d alone. However, in this case, noise included in the signal is not removed.

[0015]

As described above, according to the present invention, there is no transmission of heat or vibration from the object to be measured such as a motor.
For this reason, there is little damage and deterioration of electronic components used for optical components and signal processing circuits, etc., and the reliability is excellent, and even if it is made compact, it can be easily assembled and adjusted with almost no adjustment of optical components etc. There is an effect that an inexpensive sine wave encoder having a small size and a simple structure can be realized.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of a sine wave encoder according to an embodiment of the present invention.

FIG. 2 is a configuration diagram of a fixed analyzer plate 4.

FIG. 3 is a waveform diagram of a detection signal obtained by light receiving elements 5a to 5d.

FIG. 4 is a configuration diagram of a conventional example of an encoder.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Reflecting mirror 2 Rotating polarizer 3 Light source 4 Fixed analyzer plate 4a-4d Fixed analyzer 5 Light receiver 5a-5d Light receiving element 6 Rotation axis 11 Slit part 12 Rotating disk 13 Light source 14 Fixed slit 15 Fixed disk 16 Light receiving element 17 Shaft

Claims (2)

[Claims] 1. A reflecting mirror attached to an end face of a rotation axis of an object to be measured, a rotating polarizer provided on the reflecting mirror, and a light source for irradiating diffused light toward the rotating polarizer. Provided opposite to the rotating polarizer, transmitted through the rotating polarizer, reflected by the reflecting mirror, and hit by the diffused light transmitted through the rotating polarizer, the angles of the polarization planes are 45 ° to each other
A sine wave encoder having first and second fixed analyzers different from each other, and first and second light receiving elements that respectively receive light passing through the first and second fixed polarizers. 2. The third, third and fourth fixed analyzers are provided on the same plane as the first and second fixed analyzers, and have angles of polarization different from each other by 45 ° and different from the first and second fixed analyzers by 90 °. 4th
2. The sine wave encoder according to claim 1, further comprising: a fixed analyzer, and third and fourth light receiving elements that respectively receive light passing through the third and fourth fixed analyzers.