ENCODER AND ATTACHMENT METHOD

An encoder includes: an emitter that emits light; a rotary plate that rotates and includes an annular region that reflects the light emitted from the emitter, the annular region being provided surrounding a rotation axis of the rotary plate; and a light receiver that receives light emitted from the emitter and arriving via the annular region. The light receiver includes: a first set that includes a first light-receiving region and a second light-receiving region that are arranged side by side in a first direction intersecting a rotation direction of rotary plate; and a second set that includes a third light-receiving region and a fourth light-receiving region that are arranged side by side in a second direction intersecting the rotation direction and that is provided side by side with the first set in the rotation direction.

TECHNICAL FIELD

The present disclosure relates to an encoder and an attachment method.

BACKGROUND ART

Conventional encoders that detect rotation of a detection target, such as a motor shaft, are known. For example, such encoders include components such as a rotary plate that rotates with the detection target and a member for detecting the eccentricity of the rotary plate relative to the detection target. For example, Patent Literature (PTL) 1 discloses an angular velocity detection device. In the angular velocity detection device, sensor members are disposed facing each other across the rotation center of the shaft. Information on the angular velocity obtained from the sensor members is input to a control device to perform arithmetic processing so as to remove an error component in the attachment position of the disk and obtain only the true rotational angular velocity component, and cause a drive motor for the photoconductor drums to output drive pulses that prevent rotational fluctuations.

CITATION LIST

Patent Literature

SUMMARY OF INVENTION

Technical Problem

The angular velocity detection device according to PTL 1, however, is not capable of precisely detecting the eccentricity of the rotary plate relative to the detection target.

The present disclosure has been conceived in view of the above circumstances, and aims to provide an encoder etc. capable of precisely detecting the eccentricity of a rotary plate relative to a detection target.

Solution to Problem

An encoder according to an aspect of the present disclosure is an encoder including: an emitter that emits light; a rotary plate that rotates and includes an annular region that reflects or transmits the light emitted from the emitter, the annular region being provided surrounding a rotation axis of the rotary plate; and a light receiver that receives light emitted from the emitter and arriving via the annular region, wherein the light receiver includes: a first set that includes a first light-receiving region and a second light-receiving region that are arranged side by side in a first direction intersecting a rotation direction of the rotary plate; and a second set that includes a third light-receiving region and a fourth light-receiving region that are arranged side by side in a second direction intersecting the rotation direction and that is provided side by side with the first set in the rotation direction.

An attachment method according to an aspect of the present disclosure is an attachment method of attaching an encoder to a detection target, wherein the encoder includes: an emitter that emits light; a rotary plate that rotates and includes an annular region that reflects or transmits the light emitted from the emitter, the annular region being provided surrounding a rotation axis of the rotary plate; and a light receiver that receives light emitted from the emitter and arriving via the annular region, the light receiver includes: a first set that includes a first light-receiving region and a second light-receiving region that are arranged side by side in a first direction intersecting a rotation direction of the rotary plate; and a second set that includes a third light-receiving region and a fourth light-receiving region that are arranged side by side in a second direction intersecting the rotation direction and that is provided side by side with the first set in the rotation direction, and the encoder further includes: an outputter that outputs a signal indicating a value of X expressed as below and a signal indicating a value of Y expressed as below:

where A1 denotes a signal value corresponding to light received by the first light-receiving region, A2 denotes a signal value corresponding to light received by the second light-receiving region, B1 denotes a signal value corresponding to light received by the third light-receiving region, and B2 denotes a signal value corresponding to light received by the fourth light-receiving region, the attachment method including: attaching the rotary plate to the detection target; and after the attaching, causing the outputter to output the signal indicating the value of X and the signal indicating the value of Y, wherein in the attaching, the rotary plate is attached to the detection target at a position where the value of X indicated by the signal output by the outputter becomes 0 and the value of Y indicated by the signal output by the outputter becomes 0.

Advantageous Effects of Invention

According to the present disclosure, it is possible to provide, for example, an encoder capable of precisely detecting the eccentricity of a rotary plate relative to a detection target.

DESCRIPTION OF EMBODIMENTS

Hereinafter, embodiments of the present disclosure will be described. Note that the embodiments described below each show one specific example of the present disclosure. Therefore, the numerical values, constituent elements, the arrangement and connection of the constituent elements, steps, the processing order of the steps etc. shown in the embodiments below are mere examples, and do not intend to limit the present disclosure. Accordingly, among the constituent elements in the embodiments below, those not recited in the independent claims will be described as optional constituent elements.

Also, the drawings are represented schematically and are not necessarily precise illustrations. Note that constituent elements that are substantially the same are given the same reference signs in the drawings, and redundant descriptions thereof will be omitted or simplified.

In the embodiments described below, terms indicating relative attitudes of two directions, such as “parallel” and “orthogonal”, may be used. The meanings of such terms include attitudes that are not strictly the attitudes indicated by the terms. For example, when it is stated that two directions are orthogonal, it not only means that the two directions are completely orthogonal but also means that the two directions are substantially orthogonal unless otherwise specified. That is, it also means that differences of, for example, several percent are included.

FIG.1is a perspective view illustrating encoder10according to an embodiment.FIG.2is a schematic diagram of rotary plate20of encoder10inFIG.1as viewed in the axis direction.FIG.3is a schematic diagram of emitter40and light receiver50of encoder10inFIG.1as viewed in the axis direction.FIG.4is an explanatory diagram for describing a relationship between the dimensions of first light-receiving region55and second light-receiving region56and the dimensions of light that irradiates first light-receiving region55and second light-receiving region56in encoder10inFIG.1. Encoder10will be described with reference toFIG.1throughFIG.4.

Note thatFIG.1omits illustration of first absolute pattern22, second absolute pattern23, first incremental pattern24, second incremental pattern25, etc., to avoid complication of the drawing. Also,FIG.2illustrates only the half of rotary plate20to avoid complication of the drawing. In addition, inFIG.4, emitter40and first and second light-receiving regions55and56are shifted in a first direction to avoid complication of the drawing. Also, the axis direction indicates the direction in which rotation axis A extends (the Z-axis direction inFIG.1, for example).

As illustrated inFIG.1, encoder10detects rotation of detection target1. Specifically, encoder10detects, for example, the position (rotation position) of detection target1, the rotation direction of detection target1, the rotation amount of detection target1, and/or the rotational speed of detection target1. Detection target1rotates about rotation axis A. In the present embodiment, detection target1is the rotation shaft (the shaft) of a motor.

As illustrated inFIG.1andFIG.2, rotary plate20rotates with detection target1about rotation axis A. Rotary plate20includes main body21, first absolute pattern22, second absolute pattern23, first incremental pattern24, second incremental pattern25, and annular region26. First absolute pattern22, second absolute pattern23, first incremental pattern24, and second incremental pattern25are examples of one or more patterns for detecting the rotation angle of rotary plate20(detection target1).

Main body21is in the shape of a plate whose thickness direction is in the axis direction, and is circular as viewed in the axis direction. Main body21is attached to one end portion of detection target1in the axis direction and rotates with detection target1about rotation axis A. The axis of main body21coincides with axis B of annular region26.

First absolute pattern22is a pattern for detecting an absolute position of detection target1. First absolute pattern22is provided on a main surface of main body21closer to emitter40and is annularly provided surrounding rotation axis A. The axis of first absolute pattern22coincides with axis B of annular region26. For example, first absolute pattern22includes a reflective portion and a non-reflective portion that are arranged annularly. The reflective portion is a portion that reflects toward light receiver50light emitted from emitter40, and the non-reflective portion is a portion that does not reflect toward light receiver50the light emitted from emitter40. Second absolute pattern23is a pattern for detecting an absolute position of detection target1. Second absolute pattern23is provided on the main surface of main body21closer to emitter40and is annularly provided surrounding rotation axis A. The axis of second absolute pattern23coincides with axis B of annular region26. Second absolute pattern23is provided inwardly of first absolute pattern22in the radial direction around axis B of annular region26. For example, second absolute pattern23includes a reflective portion and a non-reflective portion that are arranged annularly. The reflective portion is a portion that reflects toward light receiver50light emitted from emitter40, and the non-reflective portion is a portion that does not reflect toward light receiver50the light emitted from emitter40.

First incremental pattern24is a pattern for detecting a relative position of detection target1. First incremental pattern24is provided on the main surface of main body21closer to emitter40and is annularly provided surrounding rotation axis A. The axis of first incremental pattern24coincides with axis B of annular region26. First incremental pattern24is provided outwardly of first absolute pattern22in the radial direction around axis B of annular region26. For example, first incremental pattern24includes a reflective portion and a non-reflective portion that are arranged annularly. The reflective portion is a portion that reflects toward light receiver50light emitted from emitter40, and the non-reflective portion is a portion that does not reflect toward light receiver50the light emitted from emitter40.

Second incremental pattern25is a pattern for detecting a relative position of detection target1. Second incremental pattern25is provided on the main surface of main body21closer to emitter40and is annularly provided surrounding rotation axis A. The axis of second incremental pattern25coincides with axis B of annular region26. Second incremental pattern25is provided inwardly of second absolute pattern23in the radial direction around axis B of annular region26. For example, second incremental pattern25includes a reflective portion and a non-reflective portion that are arranged annularly. The reflective portion is a portion that reflects toward light receiver50light emitted from emitter40, and the non-reflective portion is a portion that does not reflect toward light receiver50the light emitted from emitter40.

Note that, for example, each of one or more patterns for detecting a rotation angle of rotary plate20may transmit the light emitted from emitter40.

Annular region26is a ring-shaped region that is provided surrounding rotation axis A and reflects light emitted from emitter40. Annular region26reflects toward light receiver50the light emitted from emitter40. Annular region26is provided on the main surface of main body21closer to emitter40. The direction in which axis B of annular region26extends coincides with the axis direction.FIG.1illustrates the state in which axis B of annular region26coincides with rotation axis A. For example, annular region26includes a reflective portion that is annularly disposed in a continuous manner and reflects toward light receiver50the light emitted from emitter40.

As illustrated inFIG.1, substrate30is provided facing rotary plate20in the axis direction. Substrate30is in the shape of a plate whose thickness direction is in the axis direction.

As illustrated inFIG.1andFIG.3, emitter40emits light. Specifically, emitter40emits light toward rotary plate20. More specifically, emitter40emits light toward first absolute pattern22, second absolute pattern23, first incremental pattern24, second incremental pattern25, and annular region26. Emitter40is provided on a main surface of substrate30closer to rotary plate20.

Light receiver50receives light emitted from emitter40and arriving via annular region26, for example. Light receiver50includes first absolute light-receiving region51, second absolute light-receiving region52, first incremental light-receiving region53, second incremental light-receiving region54, a first set, and a second set. First absolute light-receiving region51, second absolute light-receiving region52, first incremental light-receiving region53, and second incremental light-receiving region54are examples of one or more light-receiving regions that receive light emitted from emitter40and arriving via one or more patterns.

First absolute light-receiving region51receives light emitted from emitter40and arriving via first absolute pattern22.

Second absolute light-receiving region52receives light emitted from emitter40and arriving via second absolute pattern23.

First incremental light-receiving region53receives light emitted from emitter40and arriving via first incremental pattern24.

Second incremental light-receiving region54receives light emitted from emitter40and arriving via second incremental pattern25.

The first set includes first light-receiving region55and second light-receiving region56that are arranged side by side in first direction E intersecting rotation direction C of rotary plate20. The second set includes third light-receiving region57and fourth light-receiving region58that are arranged side by side in second direction F intersecting rotation direction C, and is provided side by side with the first set in rotation direction C. That is to say, third light-receiving region57and fourth light-receiving region58are provided side by side with first light-receiving region55and second light-receiving region56in rotation direction C.

In the present embodiment, emitter40is interposed between the first set and the second set in rotation direction C. That is to say, emitter40is interposed between first and second light-receiving regions55and56and third and fourth light-receiving regions57and58in rotation direction C.

Each of first direction E and second direction F is a direction parallel to the plane orthogonal to rotation axis A. In the present embodiment, each of first direction E and second direction F is a direction (Y-axis direction) parallel to straight line G that is orthogonal to rotation axis A, and the first set and the second set are provided line-symmetrically with respect to straight line G. That is to say, first light-receiving region55and second light-receiving region56are arranged side by side in the direction parallel to straight line G, third light-receiving region57and fourth light-receiving region58are arranged side by side in the direction parallel to straight line G, and first and second light-receiving regions55and56and third and fourth light-receiving regions57and58are provided line-symmetrically with respect to straight line G.

In the radial direction around rotation axis A, first light-receiving region55and third light-receiving region57are provided at the same position, and second light-receiving region56and fourth light-receiving region58are provided at the same position.

First light-receiving region55and second light-receiving region56are provided at respective positions where first light-receiving region55and second light-receiving region56can receive light (see H inFIG.3) emitted from emitter40and arriving via annular region26. Third light-receiving region57and fourth light-receiving region58are provided at respective positions where third light-receiving region57and fourth light-receiving region58can receive light (see H inFIG.3) emitted from emitter40and arriving via annular region26.

For example, each of first light-receiving region55, second light-receiving region56, third light-receiving region57, and fourth light-receiving region58is a light-receiving region in a light-receiving element. That is to say, for example, light receiver50includes a plurality of light-receiving elements.

As illustrated inFIG.4, in the present embodiment, emitter40includes a point light source, and expressions below are satisfied:

where h1denotes the dimension between annular region26and emitter40in the axis direction, h2denotes the dimension between annular region26and first and second light-receiving regions55and56in the axis direction, L denotes the dimension between an end portion of first light-receiving region55farther from second light-receiving region56and an end portion of second light-receiving region56farther from first light-receiving region55in first direction E, W1denotes the dimension of annular region26in first direction E, and W2denotes the dimension, in first direction E, of light that is emitted from the point light source and, after being incident on annular region26, irradiates first light-receiving region55and second light-receiving region56. Note that the same relational expressions are satisfied for third light-receiving region57and fourth light-receiving region58as well.

Dimension L between the end portion of first light-receiving region55farther from second light-receiving region56and the end portion of second light-receiving region56farther from first light-receiving region55in first direction E is greater than dimension W2, in first direction E, of light that is emitted from emitter40and, after being incident on annular region26, irradiates first light-receiving region55and second light-receiving region56. Furthermore, the dimension between an end portion of third light-receiving region57farther from fourth light-receiving region58and an end portion of fourth light-receiving region58farther from third light-receiving region57in second direction F is greater than the dimension, in second direction F, of light that is emitted from emitter40and, after being incident on annular region26, irradiates third light-receiving region57and fourth light-receiving region58.

FIG.5is a block diagram illustrating a functional configuration of encoder10inFIG.1. The functional configuration of encoder10will be described with reference toFIG.5.

As illustrated inFIG.5, encoder10further includes outputter60and calculator70. Outputter60outputs a signal corresponding to light received by light receiver50. Specifically, outputter60outputs a signal corresponding to light received by first absolute light-receiving region51, a signal corresponding to light received by second absolute light-receiving region52, a signal corresponding to light received by first incremental light-receiving region53, a signal corresponding to light received by second incremental light-receiving region54, a signal corresponding to light received by first light-receiving region55, a signal corresponding to light received by second light-receiving region56, a signal corresponding to light received by third light-receiving region57, and a signal corresponding to light received by fourth light-receiving region58. For example, outputter60outputs a signal corresponding to the intensity of light received by light receiver50.

Outputter60outputs a signal indicating a value of X expressed as below and a signal indicating a value of Y expressed as below, where: A1 denotes a signal value corresponding to light received by first light-receiving region55; A2 denotes a signal value corresponding to light received by second light-receiving region56; B1 denotes a signal value corresponding to light received by third light-receiving region57; and B2 denotes a signal value corresponding to light received by fourth light-receiving region58.

Outputter60also outputs a signal indicating a value of Q expressed as below.

Outputter60also outputs a signal indicating a value of X1 expressed as below and a signal indicating a value of Y1 expressed as below.

Calculator70calculates a value of P1 expressed as below, where: P denotes a rotation angle (angle address) of rotary plate20detected based on light emitted from emitter40and, after being incident on one or more patterns, received by one or more light-receiving regions; Δr denotes an eccentric amount of axis B of annular region26relative to rotation axis A (seeFIG.6); Φ denotes an eccentric phase of axis B of annular region26relative to rotation axis A (seeFIG.6); and r denotes the radius of annular region26(seeFIG.6). As described above, in the present embodiment, the one or more patterns are first absolute pattern22, second absolute pattern23, first incremental pattern24, and second incremental pattern25, and the one or more light-receiving regions are first absolute light-receiving region51, second absolute light-receiving region52, first incremental light-receiving region53, and second incremental light-receiving region54.

For example, when Φ=0 through n/2 and when Φ=3n/2 through 2n, calculator70calculates a value of P1 by P1=P+tan−1(Δr×sin Φ/r).

Also, for example, when Φ=n/2 through 3n/2, calculator70calculates a value of P1 by P1=P−tan−1(Δr×sin Φ/r).

Furthermore, for example, when the value of Y calculated by Y=(A1+B1)−(A2+B2) is positive, calculator70calculates a value of P1 by P1=P+tan−1(Δr×sin Φ/r).

Furthermore, for example, when the value of Y calculated by Y=(A1+B1)−(A2+B2) is negative, calculator70calculates a value of P1 by P1=P−tan−1(Δr×sin Φ/r).

The details of the calculation method performed by calculator70will be described later.

Outputter60outputs a signal indicating the value of P1 calculated by calculator70.

The functional configuration of encoder10has been described above.

FIG.6is a schematic diagram illustrating a state in which axis B of annular region26is eccentric relative to rotation axis A.FIG.7is a schematic diagram illustrating an example of changes in position of light (see H inFIG.7) that irradiates first light-receiving region55, second light-receiving region56, third light-receiving region57, and fourth light-receiving region58, caused by rotation of rotary plate20in the state in which axis B of annular region26is eccentric relative to rotation axis A.FIG.8is a graph illustrating an example of signals output by outputter60when rotary plate20rotates in the state in which axis B of annular region26is eccentric relative to rotation axis A. The signals output by outputter60will be described with reference toFIG.6throughFIG.8.

In the state in which axis B of annular region26is eccentric relative to rotation axis A as illustrated inFIG.6, rotation of rotary plate20causes a change in the position of light that irradiates first light-receiving region55, second light-receiving region56, third light-receiving region57, and fourth light-receiving region58after being incident on annular region26.

For example, when rotary plate20is in the position indicated by T1 inFIG.7, light in the state in which axis B of annular region26is eccentric relative to rotation axis A is located more to one side in the Y-axis direction than the position of light in the state in which axis B of annular region26is not eccentric relative to rotation axis A (see the two-dot-dash line inFIG.7).

Furthermore, for example, when rotary plate20is in the position indicated by T2 inFIG.7, light in the state in which axis B of annular region26is eccentric relative to rotation axis A is located more to one side in the X-axis direction than the position of light in the state in which axis B of annular region26is not eccentric relative to rotation axis A (see the two-dot-dash line inFIG.7).

Furthermore, for example, when rotary plate20is in the position indicated by T3 inFIG.7, light in the state in which axis B of annular region26is eccentric relative to rotation axis A is located more to the other side in the Y-axis direction than the position of light in the state in which axis B of annular region26is not eccentric relative to rotation axis A (see the two-dot-dash line inFIG.7).

Furthermore, for example, when rotary plate20is in the position indicated by T4 inFIG.7, light in the state in which axis B of annular region26is eccentric relative to rotation axis A is located more to the other side in the X-axis direction than the position of light in the state in which axis B of annular region26is not eccentric relative to rotation axis A (see the two-dot-dash line inFIG.7).

As illustrated inFIG.8, when rotary plate20rotates in the state in which axis B of annular region26is eccentric relative to rotation axis A, outputter60outputs a signal indicating a shift in the X-axis direction and a signal indicating a shift in the Y-axis direction. These signals show that axis B of annular region26is eccentric relative to rotation axis A. Hereinafter, the signal indicating a shift in the X-axis direction may be described as a first signal, and the signal indicating a shift in the Y-axis direction may be described as a second signal.

The signals output by outputter60have been described above.

FIG.9is a flow chart illustrating an example of the calculation method performed by calculator70of encoder10inFIG.1. An example of the calculation method performed by calculator70will be described with reference toFIG.9.

As illustrated inFIG.9, first, calculator70matches the amplitude of the first signal and the amplitude of the second signal (step S1). As described above, the first signal is a signal indicating a shift in the X-axis direction, and the second signal is a signal indicating a shift in the Y-axis direction.

After matching the amplitude of the first signal and the amplitude of the second signal, calculator70determines the eccentric phase of axis B relative to rotation axis A and the eccentric amount of axis B relative to rotation axis A (step S2). For example, the eccentric phase of axis B relative to rotation axis A is calculated using the value of X indicated by the first signal and the value of Y indicated by the second signal. Also, for example, the eccentric amount of axis B relative to rotation axis A is calculated from the amplitude of the first signal. Furthermore, for example, the eccentric amount of axis B relative to rotation axis A is calculated from a function or a table prepared in advance. Note that the amplitude used for calculating the eccentric amount may be sequentially determined from a square root of sum of squares of the first signal and the second signal whose amplitudes have been matched. Specifically, for example, the amplitude, which is denoted by G and is used for calculating the eccentric amount, may be calculated in real time by the equation below.

Calculator70calculates an angle after determining the eccentric phase and the eccentric amount (step S3). For example, a true detection address, which is denoted by P1, is calculated by P1=P+tan−1(Δr×sin Φ/r). Here, as described above, P denotes a rotation angle of rotary plate20detected based on light emitted from emitter40and, after being incident on one or more patterns, received by light receiver50, r denotes the radius of annular region26, Δr denotes an eccentric amount of axis B of annular region26relative to rotation axis A, and Φ denotes an eccentric phase of axis B of annular region26relative to rotation axis A.

An example of the calculation method performed by calculator70has been described above.

FIG.10is a flow chart illustrating another example of the calculation method performed by calculator70of encoder10inFIG.1. Another example of the calculation method performed by calculator70will be described with reference toFIG.10. Note that the following description mainly focuses on the differences from the example of the calculation method illustrated inFIG.9.

As illustrated inFIG.10, first, calculator70obtains the amplitude of the second signal (step S11). For example, calculator70obtains the amplitude of the second signal prior to one rotation. For example, calculator70obtains the amplitude of the second signal from one rotation in a test mode or one rotation in continuous rotations. Specifically, for example, calculator70obtains the amplitude of the second signal from arbitrary 360-degree data. Also, for example, calculator70obtains the amplitude of the second signal by clipping a peak value from arbitrary 180-degree data.

After obtaining the amplitude of the second signal, calculator70determines the eccentric phase of axis B relative to rotation axis A and the eccentric amount of axis B relative to rotation axis A (step S2). For example, calculator70estimates the waveform of the second signal from the amplitude of the second signal obtained, and determines the eccentric phase of axis B relative to rotation axis A from: the value of Y indicated by the second signal output from outputter60; and the increase and decrease tendency of the signal level of the second signal.

In such a manner as described, calculator70may calculate the eccentric phase etc., of axis B relative to rotation axis A without using the first signal.

Another example of the calculation method performed by calculator70has been described above.

As described above, encoder10can more precisely detect the eccentricity of rotary plate20relative to detection target1. In addition, since encoder10includes first light-receiving region55, second light-receiving region56, third light-receiving region57, and fourth light-receiving region58on single substrate30, encoder10can be downsized and less expensive.

Encoder10according to Embodiment 1 has been described above.

Encoder10according to Embodiment 1 includes: emitter40that emits light; rotary plate20that rotates and includes annular region26that reflects the light emitted from emitter40, annular region26being provided surrounding rotation axis A of rotary plate20; and light receiver50that receives light emitted from emitter40and arriving via annular region26. Light receiver50includes: a first set that includes first light-receiving region55and second light-receiving region56that are arranged side by side in first direction E intersecting rotation direction C of rotary plate20; and a second set that includes third light-receiving region57and fourth light-receiving region58that are arranged side by side in second direction F intersecting rotation direction C and that is provided side by side with the first set in rotation direction C.

Accordingly, light receiver50includes: the first set that includes first light-receiving region55and second light-receiving region56that are arranged side by side in first direction E intersecting rotation direction C of rotary plate20; and the second set that includes third light-receiving region57and fourth light-receiving region58that are arranged side by side in second direction F intersecting rotation direction C and that is provided side by side with the first set in rotation direction C. With this, rotation of rotary plate20causes a change in the position of light received by first light-receiving region55, second light-receiving region56, third light-receiving region57, and fourth light-receiving region58, thus enabling precise detection of the eccentricity of rotary plate20relative to detection target1.

Furthermore, encoder10according to Embodiment 1 further includes outputter60that outputs a signal indicating a value of X expressed as below and a signal indicating a value of Y expressed as below:

where A1 denotes a signal value corresponding to light received by first light-receiving region55, A2 denotes a signal value corresponding to light received by second light-receiving region56, B1 denotes a signal value corresponding to light received by third light-receiving region57, and B2 denotes a signal value corresponding to light received by fourth light-receiving region58.

Accordingly, it is possible to output a signal corresponding to the position of rotary plate20, thus enabling further precise detection of the eccentricity of rotary plate20relative to detection target1.

Furthermore, in encoder10according to Embodiment 1, outputter60outputs a signal indicating a value of Q expressed as below:

Accordingly, it is possible to output a signal corresponding to the position of rotary plate20, thus enabling further precise detection of the eccentricity of rotary plate20relative to detection target1.

Furthermore, in encoder10according to Embodiment 1, outputter60outputs a signal indicating a value of X1 expressed as below and a signal indicating a value of Y1 expressed as below:

Accordingly, it is possible to output a signal corresponding to the position of rotary plate20, thus enabling further precise detection of the eccentricity of rotary plate20relative to detection target1.

Furthermore, in encoder10according to Embodiment 1, rotary plate20includes one or more patterns for detecting a rotation angle of rotary plate20, and light receiver50includes one or more light-receiving regions that receive light emitted from emitter40and arriving via the one or more patterns. Encoder10according to Embodiment 1 further includes calculator70that calculates a value of P1 expressed as below:

where P denotes a rotation angle of rotary plate20detected based on the light emitted from emitter40and, after being incident on the one or more patterns, received by the one or more light-receiving regions, Δr denotes an eccentric amount of axis B of annular region26relative to rotation axis A, Φ denotes an eccentric phase of axis B relative to rotation axis A, and r denotes the radius of annular region26.

Outputter60outputs a signal indicating the value of P1calculated by calculator70.

Accordingly, it is possible to detect the correct position of detection target1even in the state in which rotary plate20is eccentric relative to detection target1.

Furthermore, in encoder10according to Embodiment 1, emitter40is interposed between the first set and the second set in rotation direction C.

Accordingly, it is possible to inhibit reduction of the amount of light received by first light-receiving region55, second light-receiving region56, third light-receiving region57, and fourth light-receiving region58, thus enabling further precise detection of the eccentricity of rotary plate20relative to detection target1.

Furthermore, in encoder10according to Embodiment 1, each of first direction E and second direction F is a direction parallel to straight line G orthogonal to rotation axis A, and the first set and the second set are provided line-symmetrically with respect to straight line G.

It is possible to inhibit reduction of the amount of light received by first light-receiving region55, second light-receiving region56, third light-receiving region57, and fourth light-receiving region58and inhibit variation in the amount of light received by first light-receiving region55, second light-receiving region56, third light-receiving region57, and fourth light-receiving region58, thus enabling further precise detection of the eccentricity of rotary plate20relative to detection target1.

Furthermore, in encoder10according to Embodiment 1, dimension L between an end portion of first light-receiving region55farther from second light-receiving region56and an end portion of second light-receiving region56farther from first light-receiving region55in first direction E is greater than dimension W2, in the first direction, of light that is emitted from emitter40and, after being incident on annular region26, irradiates first light-receiving region55and second light-receiving region56, and the dimension between an end portion of third light-receiving region57farther from fourth light-receiving region58and an end portion of fourth light-receiving region58farther from third light-receiving region57in second direction F is greater than the dimension, in second direction F, of light that is emitted from emitter40and, after being incident on annular region26, irradiates third light-receiving region57and fourth light-receiving region58.

Accordingly, in the state in which rotary plate20is eccentric relative to detection target1, rotation of rotary plate20can cause an appropriate change in the position of light received by first light-receiving region55and second light-receiving region56and the position of light received by third light-receiving region57and fourth light-receiving region58, thus enabling further precise detection of the eccentricity of rotary plate20relative to detection target1.

Furthermore, in encoder10according to Embodiment 1, emitter40includes a point light source, and expressions below are satisfied:

where h1denotes the dimension between annular region26and emitter40in an axis direction in which rotation axis A extends, h2denotes the dimension between annular region26and first and the second light-receiving regions55and56in the axis direction in which rotation axis A extends, L denotes the dimension between the end portion of the first light-receiving region farther from the second light-receiving region and the end portion of the second light-receiving region farther from the first light-receiving region in the first direction, W1denotes the dimension of the annular region in the first direction, and W2denotes the dimension, in the first direction, of light that is emitted from the point light source and, after being incident on the annular region, irradiates the first light-receiving region and the second light-receiving region.

Accordingly, in the state in which rotary plate20is eccentric relative to detection target1, rotation of rotary plate20can cause an appropriate change in the position of light received by first light-receiving region55and second light-receiving region56, thus enabling further precise detection of the eccentricity of rotary plate20relative to detection target1.

FIG.11is a schematic diagram of rotary plate20aof an encoder according to Embodiment 2 as viewed in the axis direction.FIG.12is a schematic diagram of emitter40aand light receiver50aof the encoder inFIG.11as viewed in the axis direction. A configuration of the encoder according to Embodiment 2 will be described with reference toFIG.11andFIG.12. Note that the following description mainly focuses on the differences from encoder10according to Embodiment 1.

Note thatFIG.11illustrates only the half of rotary plate20ato avoid complication of the drawing.

As illustrated inFIG.11, the encoder according to Embodiment 2 includes rotary plate20adifferent from rotary plate20. Also, as illustrated inFIG.12, the encoder according to Embodiment 2 includes emitter40adifferent from emitter40and light receiver50adifferent from light receiver50. The encoder according to Embodiment 2 is different from encoder10mainly in these aspects.

Annular region26ais a ring-shaped region that is provided surrounding rotation axis A and reflects the light emitted from emitter40a. Annular region26areflects toward light receiver50athe light emitted from emitter40a. Annular region26ais provided on the main surface of main body21closer to emitter40a. The direction in which axis B of annular region26aextends coincides with the axis direction. For example, annular region26aincludes a reflective portion that is annularly disposed in a continuous manner and reflects toward light receiver50athe light emitted from emitter40a.

As illustrated inFIG.12, emitter40aemits light. Specifically, emitter40aemits light toward rotary plate20a. More specifically, emitter40aemits light toward absolute pattern22a, incremental pattern24a, and annular region26a. Emitter40ais provided on the main surface of substrate30closer to rotary plate20a.

First absolute light-receiving region51aand second absolute light-receiving region52aeach receive light emitted from emitter40aand arriving via absolute pattern22a.First absolute light-receiving region51aand second absolute light-receiving region52aare arranged out of alignment with each other in rotation direction C.

First incremental light-receiving region53aand second incremental light-receiving region54aeach receive light emitted from emitter40aand arriving via incremental pattern24a.First incremental light-receiving region53aand second incremental light-receiving region54aare arranged out of alignment with each other in rotation direction C.

The first set includes first light-receiving region55aand second light-receiving region56athat are arranged side by side in first direction E intersecting rotation direction C of rotary plate20a.The second set includes third light-receiving region57aand fourth light-receiving region58athat are arranged side by side in second direction F intersecting rotation direction C, and is provided side by side with the first set in rotation direction C.

An end portion of first light-receiving region55acloser to second light-receiving region56a,an end portion of second light-receiving region56acloser to first light-receiving region55a,an end portion of third light-receiving region57acloser to fourth light-receiving region58a,and an end portion of fourth light-receiving region58acloser to third light-receiving region57aare each in the shape of a straight line extending in the tangential direction with respect to rotation direction C.

Also, an end portion of first light-receiving region55afarther from second light-receiving region56a,an end portion of second light-receiving region56afarther from first light-receiving region55a, an end portion of third light-receiving region57afarther from fourth light-receiving region58a,and an end portion of fourth light-receiving region58afarther from third light-receiving region57aare each in the shape of a straight line extending in the tangential direction with respect to rotation direction C.

The encoder according to Embodiment 2 has been described above.

In the encoder according to Embodiment 2, the end portion of first light-receiving region55acloser to second light-receiving region56a,the end portion of second light-receiving region56acloser to first light-receiving region55a,the end portion of third light-receiving region57acloser to fourth light-receiving region58a,and the end portion of fourth light-receiving region58acloser to third light-receiving region57aare each in the shape of a straight line extending in the tangential direction with respect to rotation direction C.

Accordingly, it is possible to inhibit reduction of the amount of light received by first light-receiving region55a,second light-receiving region56a,third light-receiving region57a,and fourth light-receiving region58a,thus enabling further precise detection of the eccentricity of rotary plate20arelative to detection target1.

FIG.13is a schematic diagram of rotary plate20bof an encoder according to Embodiment 3 as viewed in the axis direction.FIG.14is a schematic diagram of emitter40band light receiver50bof the encoder inFIG.13as viewed in the axis direction. A configuration of the encoder according to Embodiment 3 will be described with reference toFIG.13andFIG.14. Note that the following description mainly focuses on the differences from encoder10according to Embodiment 1.

Note thatFIG.13illustrates only the half of rotary plate20bto avoid complication of the drawing.

As illustrated inFIG.13, the encoder according to Embodiment3includes rotary plate20bdifferent from rotary plate20. Also, as illustrated inFIG.14, the encoder according to Embodiment 3 includes emitter40bdifferent from emitter40and light receiver50bdifferent from light receiver50. The encoder according to Embodiment 3 is different from encoder10mainly in these aspects.

Annular region26bis a ring-shaped region that is provided surrounding rotation axis A and reflects the light emitted from emitter40b.Annular region26breflects toward light receiver50bthe light emitted from emitter40b.Annular region26bis provided on the main surface of main body21closer to emitter40b.The direction in which axis B of annular region26bextends coincides with the axis direction. For example, annular region26bincludes a reflective portion that is annularly disposed in a continuous manner and reflects toward light receiver50bthe light emitted from emitter40b.

Annular region26bis located inwardly of absolute pattern22band incremental pattern24bin the radial direction around axis center B. That is to say, among absolute pattern22b,incremental pattern24b,and annular region26b,annular region26bis located most inwardly in the radial direction.

As illustrated inFIG.14, emitter40bemits light. Specifically, emitter40bemits light toward rotary plate20b.More specifically, emitter40bemits light toward absolute pattern22b,incremental pattern24b,and annular region26b.Emitter40bis provided on the main surface of substrate30closer to rotary plate20b.

First absolute light-receiving region51band second absolute light-receiving region52beach receive light emitted from emitter40band arriving via absolute pattern22b.

First incremental light-receiving regions53band second incremental light-receiving regions54beach receive light emitted from emitter40band arriving via incremental pattern24b.

The first set includes first light-receiving region55band second light-receiving region56bthat are arranged side by side in first direction E intersecting rotation direction C of rotary plate20b.The second set includes third light-receiving region57band fourth light-receiving region58bthat are arranged side by side in second direction F intersecting rotation direction C, and is provided side by side with the first set in rotation direction C.

Each of the first set and the second set is located inwardly of emitter40bin the radial direction around rotation axis A. That is to say, each of first light-receiving region55b,second light-receiving region56b,third light-receiving region57b,and fourth light-receiving region58bis located inwardly of emitter40bin the radial direction around rotation axis A.

An end portion of first light-receiving region55bcloser to second light-receiving region56b,an end portion of second light-receiving region56bcloser to first light-receiving region55b,an end portion of third light-receiving region57bcloser to fourth light-receiving region58b,and an end portion of fourth light-receiving region58bcloser to third light-receiving region57bare each in the shape of a curved line extending in rotation direction C.

Also, an end portion of first light-receiving region55bfarther from second light-receiving region56b,an end portion of second light-receiving region56bfarther from first light-receiving region55b, an end portion of third light-receiving region57bfarther from fourth light-receiving region58b,and an end portion of fourth light-receiving region58bfarther from third light-receiving region57bare each in the shape of a curved line extending in rotation direction C.

First light-receiving region55b,second light-receiving region56b,third light-receiving region57b,and fourth light-receiving region58bare each in the shape of an arc extending in rotation direction C.

First direction E is a direction that coincides with the radial direction around rotation axis A, and second direction F is a direction that coincides with the radial direction around rotation axis A and intersects first direction E.

First light-receiving region55band third light-receiving region57bare adjacent to each other in rotation direction C, and second light-receiving region56band fourth light-receiving region58bare adjacent to each other in rotation direction C.

The encoder according to Embodiment 3 has been described above.

In the encoder according to Embodiment 3, each of the first set and the second set is located inwardly of emitter40bin the radial direction around rotation axis A.

Accordingly, it is possible to more easily bend the light received by first light-receiving region55b,second light-receiving region56b, third light-receiving region57b,and fourth light-receiving region58b, thus enabling further precise detection of the eccentricity of rotary plate20brelative to detection target1.

Furthermore, in the encoder according to Embodiment 3, an end portion of first light-receiving region55bcloser to second light-receiving region56b,an end portion of second light-receiving region56bcloser to first light-receiving region55b,an end portion of third light-receiving region57bcloser to fourth light-receiving region58b, and an end portion of fourth light-receiving region58bcloser to third light-receiving region57bare each in the shape of a curved line extending in rotation direction C.

Accordingly, it is possible to inhibit reduction of the amount of light received by first light-receiving region55b,second light-receiving region56b,third light-receiving region57b,and fourth light-receiving region58b,thus enabling further precise detection of the eccentricity of rotary plate20brelative to detection target1.

Furthermore, in the encoder according to Embodiment 3, first direction E is a direction that coincides with the radial direction around rotation axis A, and second direction F is a direction that coincides with the radial direction around rotation axis A and intersects first direction E.

It is possible to further inhibit reduction of the amount of light received by first light-receiving region55b,second light-receiving region56b,third light-receiving region57b,and fourth light-receiving region58b,thus enabling further precise detection of the eccentricity of rotary plate20brelative to detection target1.

FIG.15is a schematic diagram of emitter40cand light receiver50cof an encoder according to Embodiment 4 as viewed in the axis direction. A configuration of the encoder according to Embodiment 4 will be described with reference toFIG.15. Note that the following description mainly focuses on the differences from encoder10according to Embodiment 1.

As illustrated inFIG.15, the encoder according to Embodiment 4 is mainly different from encoder10in including a rotary plate (not illustrated) different from rotary plate20, emitter40cdifferent from emitter40, and light receiver50cdifferent from light receiver50.

Emitter40cemits light. Specifically, emitter40cemits light toward the rotary plate. More specifically, emitter40cemits light toward, for example, an annular region (not illustrated) of the rotary plate. Emitter40cis provided on the main surface of substrate30closer to the rotary plate.

Light receiver50creceives light emitted from emitter40cand arriving via the annular region of the rotary plate of the encoder according to Embodiment 4, for example. Light receiver50cincludes first absolute light-receiving region51c,second absolute light-receiving region52c,first incremental light-receiving region53c, second incremental light-receiving region54c,a first set, and a second set.

First absolute light-receiving region51cand second absolute light-receiving region52ceach receive light emitted from emitter40cand arriving via an absolute pattern of the rotary plate.

First incremental light-receiving region53cand second incremental light-receiving region54ceach receive light emitted from emitter40cand arriving via an incremental pattern of the rotary plate.

The first set includes first light-receiving region55cand second light-receiving region56cthat are arranged side by side in first direction E intersecting rotation direction C of the rotary plate. The second set includes third light-receiving region57cand fourth light-receiving region58cthat are arranged side by side in second direction F intersecting rotation direction C, and is provided side by side with the first set in rotation direction C.

A phase difference of 90 degrees is provided between the first set and the second set in rotation direction C. That is to say, the second set is provided at a position shifted from the first set by 90 degrees in rotation direction C.

The encoder according to Embodiment 4 has been described above.

FIG.16is an explanatory diagram for describing a relationship between the dimensions of first light-receiving region55dand second light-receiving region56dand the dimensions of light that irradiates first light-receiving region55dand second light-receiving region56din an encoder according to Embodiment 5. A configuration of the encoder according to Embodiment 5 will be described with reference toFIG.16.

As illustrated inFIG.16, in the present embodiment, emitter40dincludes a surface light source, and expressions below are satisfied:

where h1denotes the dimension between annular region26dand emitter40din an axis direction in which rotation axis A extends, h2denotes the dimension between annular region26dand first and the second light-receiving regions55dand56din the axis direction in which rotation axis A extends, L denotes the dimension between the end portion of first light-receiving region55dfarther from second light-receiving region56dand the end portion of second light-receiving region56dfarther from first light-receiving region55din first direction E, W1denotes the dimension of annular region26din first direction E, W2denotes the dimension, in first direction E, of light that is emitted from the surface light source and, after being incident on annular region26d,irradiates first light-receiving region55dand second light-receiving region56d,and D denotes the dimension of a light emission port of the surface light source in first direction E. Even if the reflected light on the light-receiving surface moves due to the maximum correctable eccentricity, L is designed to, for example, inhibit the reflected light from going outside the light-receiving regions (first light-receiving region55dand second light-receiving region56d). Note that the same relational expressions are satisfied for a third light-receiving region and a fourth light-receiving region as well.

The encoder according to Embodiment 5 has been described above.

In the encoder according to Embodiment 5, emitter40dincludes a surface light source, and expressions below are satisfied:

where h1denotes the dimension between annular region26dand emitter40din an axis direction in which rotation axis A extends, h2denotes the dimension between annular region26dand first and the second light-receiving regions55dand56din the axis direction in which rotation axis A extends, L denotes the dimension between the end portion of first light-receiving region55dfarther from second light-receiving region56dand the end portion of second light-receiving region56dfarther from first light-receiving region55din first direction E, W1denotes the dimension of annular region26din first direction E, W2denotes the dimension, in first direction E, of light that is emitted from the surface light source and, after being incident on annular region26d,irradiates first light-receiving region55dand second light-receiving region56d,and D denotes the dimension of a light emission port of the surface light source in first direction E.

Accordingly, in the state in which the rotary plate is eccentric relative to detection target1, rotation of the rotary plate can cause an appropriate change in the position of light received by first light-receiving region55dand second light-receiving region56d,thus enabling further precise detection of the eccentricity of the rotary plate relative to detection target1.

FIG.17is an explanatory diagram for describing a relationship between the dimensions of first light-receiving region55eand second light-receiving region56eand the dimensions of light that irradiates first light-receiving region55eand second light-receiving region56ein an encoder according to Embodiment 6. A configuration of the encoder according to Embodiment 6 will be described with reference toFIG.17. Note that the following description mainly focuses on the differences from encoder10according to Embodiment 1.

Annular region26eis recessed in the axis direction in which rotation axis A extends. Light emitted from emitter40eand reflected by annular region26eirradiates first light-receiving region55eand second light-receiving region56ewhile converging. Similarly, light emitted from emitter40eand reflected by annular region26ealso irradiates a third light-receiving region and a fourth light-receiving region while converging.

The encoder according to Embodiment 6 has been described above.

In the encoder according to Embodiment 6, annular region26eis recessed in the axis direction in which rotation axis A extends.

Accordingly, it is possible to inhibit reduction of the intensity of light received by each of first light-receiving region55e,second light-receiving region56e,the third light-receiving region, and the fourth light-receiving region, thus enabling further precise detection of the eccentricity of the rotary plate relative to detection target1.

FIG.18is a flow chart illustrating an example of an attachment method according to Embodiment 7. An example of the attachment method according to Embodiment 7 will be described with reference toFIG.18. Described here is an attachment method for attaching encoder10to detection target1.

As illustrated inFIG.18, first, rotary plate20is attached to detection target1(step S21). For example, rotary plate20is attached to detection target1by using a screw, for example.

When rotary plate20is attached to detection target1, rotary plate20is rotated about rotation axis A (step S22). Note that rotary plate20need not necessarily be rotated.

After rotary plate20is rotated about rotation axis A, a signal output by outputter60is obtained (step S23). A value of X and a value of Y are obtained from the signal output by outputter60.

When the signal output by outputter60is obtained, it is determined whether each of the value of X and the value of Y is 0 (step S24).

When each of the value of X and the value of Y is not 0 (No in step S24), the attachment position of rotary plate20attached to detection target1is adjusted (step S25).

In such a manner as described, when each of the value of X and the value of Y is not 0, the attachment position of rotary plate20attached to detection target1is adjusted, and it is determined again whether each of the value of X and the value of Y is 0. Encoder10is attached to detection target1at a position where the value of X output by outputter60becomes 0 and the value of Y output by outputter60becomes 0.

The attachment method according to Embodiment 7 has been described above.

The attachment method according to Embodiment 7 is an attachment method of attaching encoder10to detection target1. Encoder10includes: emitter40that emits light; rotary plate20that rotates and includes annular region26that reflects the light emitted from emitter40, annular region26being provided surrounding rotation axis A of rotary plate20; and light receiver50that receives light emitted from emitter40and arriving via annular region26. Light receiver50includes: a first set that includes first light-receiving region55and second light-receiving region56that are arranged side by side in first direction E intersecting rotation direction C of rotary plate20; and a second set that includes third light-receiving region57and fourth light-receiving region58that are arranged side by side in second direction F intersecting rotation direction C and that is provided side by side with the first set in rotation direction C. Encoder10further includes outputter60that outputs a signal indicating a value of X expressed as below and a signal indicating a value of Y expressed as below:

where A1 denotes a signal value corresponding to light received by first light-receiving region55, A2 denotes a signal value corresponding to light received by second light-receiving region56, B1 denotes a signal value corresponding to light received by third light-receiving region57, and B2 denotes a signal value corresponding to light received by fourth light-receiving region58. The attachment method includes: step S21of attaching rotary plate20to detection target1; and after attaching rotary plate20to detection target1, step S23of causing outputter60to output the signal indicating the value of X and the signal indicating the value of Y. In the attaching of rotary plate20to detection target1, rotary plate20is attached to detection target1at a position where the value of X indicated by the signal output by outputter60becomes 0 and the value of Y indicated by the signal output by outputter60becomes 0.

Accordingly, it is possible to inhibit attachment of encoder10in a state in which encoder10is eccentric relative to detection target1.

Other Embodiments Etc.

Embodiments have been described above as examples of the techniques disclosed in the present application. The techniques according to the present disclosure are, however, not limited to these embodiments and are applicable to embodiments or variations resulting from modifications, replacements, additions, omissions as appropriate, so long as they do not depart from the essence of the present disclosure.

In the embodiments described above, annular regions26through26ereflect light; however, the present disclosure is not limited to this. For example, the annular region may transmit the light emitted from the emitter, toward the light receiver.

Note that in the above embodiments, each constituent element may be configured as dedicated hardware or may be realized by executing a software program suitable for the constituent element. Each of the constituent elements may be realized by means of a program executor, such as a central processing unit (CPU) or a processor, reading and executing a software program recorded on a recording medium such as a hard disk or semiconductor memory. Here, the software programs for realizing, for example, the calculation methods and the attachment method according to the above embodiments are computer programs that cause a computer to perform the steps of the flow charts inFIG.9,FIG.10, andFIG.18.

Note that the following cases are also included in the present disclosure.

(1) At least one device described above is specifically a computer system including a microprocessor, ROM, RAM, a hard disk unit, a display unit, a keyboard, and a mouse, for example. A computer program is stored in the RAM or the hard disk unit. At least one device described above achieves its function as a result of the microprocessor operating according to the computer program. Here, the computer program is configured by combining a plurality of instruction codes indicating instructions to be given to the computer, in order to achieve a given function.

(2) Some or all of the constituent elements included in at least one device described above may be configured from a single system large-scale integration (LSI) circuit. A system LSI circuit is a super-multifunction LSI circuit manufactured with a plurality of components integrated on a single chip, and is specifically a computer system including a microprocessor, ROM, and RAM, for example. A computer program is stored in the RAM. The system LSI achieves its function as a result of the microprocessor operating according to the computer program.

(3) Some or all of the constituent elements included in at least one device described above may be configured as an integrated circuit (IC) card that is detachably attached to the device, or as a stand-alone module. The IC or and the module is a computer system including a microprocessor, ROM, and RAM, for example. The IC card or the module may include the super-multifunction LSI circuit described above. The IC card or the module achieves its function as a result of the microprocessor operating according to a computer program. The IC card or the module may be tamperproof.

(4) The present disclosure may be implemented as the methods described above. The present disclosure may also be a computer program that realizes such methods using a computer, or a digital signal including the computer program.

The present disclosure may also be a computer-readable recording medium, such as a flexible disk, a hard disk, a compact disc (CD)-ROM, a DVD, a DVD-ROM, a DVD-RAM, a Blu-ray Disc (BD; registered trademark), semiconductor memory, etc., having recording thereon the computer program or the digital signal. The present disclosure may also be the digital signal recorded on these recording media.

The present disclosure may transmit the computer program or the digital signal via, for example, a telecommunication line, a wireless or wired communication line, a network such as the Internet, or data broadcasting.

The program or the digital signal may be implemented by another independent computer system by recording the program or the digital signal on a recording medium and transporting it or by transporting the program or the digital signal via a network, etc.

Industrial Applicability

The encoders according to the present disclosure can be used in detecting rotation of, for example, the rotary shaft of a motor that rotates and drives a load.

Reference Signs List