JP6421410B2 - Encoder scale, encoder, drive device, and stage device - Google Patents

Description

  The present invention relates to an encoder scale, an encoder, a drive device, and a stage device.

  An encoder is used to detect the amount of movement and position information of a moving object such as a mover of a linear motor or a drive shaft of a rotary motor. As an example of the encoder, there is an optical encoder, and a configuration including a scale on which an optical pattern is formed and a light detection unit that detects the optical pattern is known. The scale described above is attached to, for example, a drive shaft of a rotary motor, and rotates integrally with the drive shaft. At that time, the optical pattern is irradiated with light, reflected light or transmitted light is acquired by the light detection unit, and the rotation amount and rotation position of the shaft part are detected based on a signal corresponding to the change in the light intensity. .

  In recent years, a configuration in which a so-called Archimedean spiral pattern is formed on an encoder scale is known (see, for example, Patent Document 1). The spiral pattern is formed so that the radius continuously changes in the rotation direction around the rotation axis of the scale, and the reflectance or transmittance changes at a predetermined pitch. In this configuration, the spiral pattern periodically changes in phase in the radial direction every time the scale makes one round. For this reason, the light detection unit can detect the rotation amount and rotation position of the scale by detecting this phase change.

  On the other hand, in such a scale, if the rotation axis is decentered or the scale is deformed due to a temperature change, the position of the spiral pattern may shift in the radial direction, which may cause a detection error. Therefore, a pattern track for compensating for a detection error may be formed separately from the spiral pattern.

JP 2012-68124 A

  However, when a plurality of pattern tracks including the spiral pattern is to be formed on the scale, it is necessary to secure a space for arranging these patterns on the scale. For this reason, it is difficult to reduce the scale. Moreover, since it is necessary to enlarge the irradiation range of the light irradiated to a pattern, the cost of a light source will become high.

  In view of the circumstances as described above, the present invention enables a small scale and realizes downsizing of the encoder, and at the same time, can achieve cost reduction, an encoder scale, an encoder, an encoder manufacturing method, a drive device, and An object is to provide a stage apparatus.

According to the first aspect of the present invention, the encoder scale includes a first spiral pattern having a radius that continuously changes in the rotation direction about the rotation axis, and the first spiral pattern is centered on the rotation axis. A plurality of first light reflection portions or a plurality of first light transmission portions arranged along the locus of the first spiral, wherein the first light reflection portion or the first light transmission portion is: radially around the rotation axis disposed at a first pitch, and the scale for Rue encoder is arranged at a second pitch is provided in the direction of the first spiral.

According to a second aspect of the present invention, the scale for encoders, and a light detector for detecting light through the encoder scale, as the scale encoder, the encoder scale according to the first aspect of the present invention An encoder to be used is provided.

  According to a third aspect of the present invention, a moving member, a drive unit that moves the moving member, and an encoder that is fixed to the moving member and detects position information of the moving member are provided. A drive device is provided in which an encoder according to two aspects is used.

  According to the fourth aspect of the present invention, there is provided a stage apparatus that includes a moving object and a driving device that moves the moving object, and uses the driving device according to the third aspect of the present invention as the driving device.

  According to the aspect of the present invention, the encoder scale can be reduced, and the encoder can be reduced in size. Further, the cost of the light source to be used can be prevented from increasing, and the cost can be reduced.

It is a figure which shows an example of the scale for encoders concerning 1st Embodiment, (a) is a perspective view, (b) It is a top view. It is a graph which shows an example of a detection signal. (A) is sectional drawing which shows an example of embodiment of the encoder using the scale for encoders shown in FIG. 1, (b)-(d) is a top view which shows an example of a photon detection part. It is a figure which shows typically the circuit structure of a light-receiving part. It is a functional block diagram which shows the structure of the control circuit of a photon detection part. It is a flowchart which shows operation | movement of an encoder. It is a top view which shows an example of the scale for encoders concerning 2nd Embodiment. (A) is sectional drawing which shows an example of embodiment of the encoder using the scale for encoders shown in FIG. 7, (b) is a top view which shows an example of a photon detection part. It is a functional block diagram which shows the structure of the control circuit of a photon detection part. It is a graph which shows the signal value of the detection signal detected by the light-receiving part. It is a top view which shows an example of the scale for encoders concerning a 1st modification. It is a graph which shows the signal value of the detection signal detected by the light-receiving part. (A) is a top view which shows an example of the scale for encoders concerning 3rd Embodiment, (b) is a top view which shows an example of the scale for encoders concerning a 2nd modification. An example of the encoder which concerns on 4th Embodiment is shown, (a) is a top view, (b) is sectional drawing along the AA of (a). It is sectional drawing which shows an example of the encoder which concerns on a 3rd modification. It is a top view which shows an example of the scale for encoders concerning 5th Embodiment. It is a figure which shows an example of the drive device which concerns on embodiment. It is a figure which shows an example of the stage apparatus which concerns on embodiment.

  Embodiments of the present invention will be described below with reference to the drawings. However, the present invention is not limited to this. Further, in the drawings, in order to describe the embodiment, the scale is appropriately changed and expressed, for example, partly enlarged or emphasized. In the following description, “encoder scale” may be abbreviated as “scale” as appropriate.

<First Embodiment>
FIG. 1 is a diagram illustrating an example of an encoder scale S according to the first embodiment. The scale S constitutes a part of an optical rotary encoder, for example, and is used by being attached to a shaft portion of a drive system such as a rotary motor. In this case, the scale S rotates around the axis about the rotation axis AX. The scale S is a reflective scale.

  As shown in FIG. 1A, the scale S includes a substrate 10 and a fixing portion 20. The substrate 10 is formed in a circular shape having a predetermined diameter around the rotation axis AX. The substrate 10 is formed using a material having such a rigidity that it is not easily deformed by rotation, impact, vibration, or the like, such as glass, metal, resin, or ceramic. Although the substrate 10 is formed with a uniform thickness, for example, the central portion or the like may be formed thicker than the periphery. The material, thickness, dimensions, and the like of the substrate 10 can be appropriately determined according to the application, for example, the rotational speed of the shaft portion to be attached, the installation environment such as the installation temperature and humidity, and the like.

  The fixing portion 20 is formed in a cylindrical shape that protrudes from the second surface 10 b of the substrate 10. The fixed portion 20 is fixed to a moving member that is a measurement target, such as a shaft portion such as a rotary motor. The fixed part 20 has a mounting hole 20a into which a shaft part such as a rotary motor can be inserted. The fixing portion 20 may be provided with a fixing mechanism (not shown) such as a fixing screw for fixing the shaft portion in a state where the shaft portion is inserted into the mounting hole 20a.

  FIG. 1B is a plan view showing the configuration of the first surface 10 a of the substrate 10. As shown in FIGS. 1A and 1B, an optical pattern (first spiral pattern) 30 is formed on the first surface 10 a of the substrate 10. The optical pattern 30 is a light reflection pattern. The optical pattern 30 includes a light reflecting portion 31 and a reflection suppressing portion 32.

The light reflecting portion 31 is formed using, for example, a highly reflective metal material such as aluminum or an inorganic material such as silicon oxide (SiO ₂ ). The light reflecting portion 31 may be mirror-finished. The light reflecting portion 31 has a reflectance set to, for example, about 40% or more. However, in order to ensure a sufficient reflectance in the light reflecting portion 31, the light reflecting portion 31 can be formed so that the reflectance becomes 70% or more, for example. In addition, the reflectance here is the reflectance with respect to the detection light used with an optical encoder, for example.

The light reflecting portion 31 is arranged along a spiral locus centering on the rotation axis AX. As shown in FIG. 1B, the distance between the light reflection part 31 (light reflection part 31x) closest to the rotation axis AX and the rotation axis AX is R0, the phase angle is θ, and the radius of the algebraic helix is R. Then, the light reflecting portion 31 is
R = R0 + Pθ Formula (1)
It is arranged along the spiral represented by (Archimedes' spiral). As shown in the equation (1), the radius R of this spiral changes continuously according to the change of the phase angle θ. FIGS. 1A and 1B show a configuration in which the light reflecting portion 31 is arranged along, for example, eight turns of an algebraic spiral satisfying the above formula (1). However, the configuration is limited to this. In other words, it is sufficient that the light reflecting portion 31 has at least one turn.

  Since the light reflecting portion 31 is arranged along such a spiral locus, the distance from the rotation axis AX continuously changes in the rotation direction D1. Moreover, the light reflection part 31 is arrange | positioned for every rotation from the outermost periphery to the innermost periphery for every predetermined angle (alpha) (2nd pitch) regarding the rotation direction D1. For this reason, the light reflection part 31 is arrange | positioned in the state located in a line with the radial direction D2.

  The dimension in the rotation direction D1 of the light reflecting portions 31 arranged in the radial direction D2 gradually decreases from the outermost periphery to the innermost periphery. Both ends of the light reflecting portion 31 in the rotation direction D1 are arranged on two virtual straight lines set to have an angle θ1 with the rotation axis AX as a center. For this reason, the light reflecting portion 31 is formed so as to spread radially around the rotation axis AX. The light reflecting portions 31 are arranged side by side at a pitch P (first pitch) equal to the radial direction D2. The light reflecting portion 31 is formed such that the dimension (width) in the radial direction D2 is a constant value W1.

  The reflection suppressing unit 32 is formed using, for example, a metal material having a high light absorption rate such as chromium (Cr) or a material having a high light transmittance such as glass. The reflection suppression unit 32 has a lower reflectance than the light reflection unit 31. The reflectance ratio between the light reflecting portion 31 and the reflection suppressing portion 32 can be set arbitrarily. The reflectance ratio is set to an arbitrary value that allows the light detection unit 40 described later to identify the reflected light from the light reflecting unit 31.

  The reflection suppressing unit 32 is disposed so as to fill the space between the light reflecting units 31 in the rotation direction D1 and the radial direction D2. For this reason, the reflection suppression part 32 is arrange | positioned for every predetermined angle (alpha) regarding the rotation direction D1. Moreover, the reflection suppression part 32 is arrange | positioned along with the predetermined pitch P across the light reflection part 31 in the radial direction D2. The reflection suppressing portion 32 is formed such that the dimension (width) in the radial direction D2 is a constant value W2. A dimension W2 of the reflection suppressing unit 32 in the radial direction D2 is equal to, for example, the dimension W1 of the light reflecting unit 31 in the radial direction D2. In addition, the end portions of the adjacent light reflecting portions 31 facing each other in the rotation direction D1 are arranged on two imaginary straight lines set to have an angle θ2 with the rotation axis AX as the center. This angle θ2 is equal to the angle θ1 for both ends of the light reflecting portion 31 in the rotation direction D1.

  The light reflecting portions 31 and the reflection suppressing portions 32 are alternately arranged in the rotation direction D1. For this reason, on the first surface 10a of the substrate 10, the light reflectance changes in the rotation direction D1 with a predetermined period. The arrangement of the optical pattern 30 along the rotation direction D1 is used as an incremental pattern.

  Moreover, the light reflection part 31 and the reflection suppression part 32 are alternately arrange | positioned in the radial direction D2. Therefore, on the first surface 10a of the substrate 10, the light reflectance changes at a predetermined period in the radial direction D2. Of the optical pattern 30, a group (eight) of light reflecting portions 31 arranged in the radial direction D2 from the rotation axis AX, the group of light reflecting portions 31 is counterclockwise with respect to the position of the light reflecting portion 31X. As the phase angle θ increases, the position in the radial direction D2 is arranged so as to approach the outer peripheral side (or away from the rotation axis AX). Such an arrangement of the group of light reflecting portions 31 is used as an absolute pattern.

  2 (a) and 2 (b), as shown in FIG. 1 (a), while the scale S is rotated, the optical pattern 30 is irradiated with detection light and the reflected light is received. It is a graph which shows the detection signal output by photoelectric conversion. FIG. 2A shows the intensity distribution of light reflected by the group of light reflecting portions 31 arranged in the radial direction D2 from the rotation axis AX in the optical pattern 30, and shows an absolute signal. The horizontal axis of the graph shown in FIG. 2A indicates the position corresponding to the radial direction D2 of the scale S, and the vertical axis of the graph indicates the signal intensity of the detection signal. The detection signal here is a detection signal obtained by integrating the detection values of the light reflected by one light reflecting portion 31 in the rotation direction D1.

  As shown in FIG. 2A, the light detection unit 40 obtains a waveform detection signal. As the optical pattern 30 moves (rotates), the group of light reflecting portions 31 moves in the radial direction D2 with respect to the light detecting portion 40. Due to the movement of the group of light reflecting portions 31, the detection signal moves in the radial direction D2. The light detection unit 40 detects the position of the detection signal in the radial direction D2. The light detection unit 40 averages a plurality of peak values in the waveform detection signal to detect the position in the radial direction D2, and corrects the detection error.

  In the optical pattern 30 shown in FIGS. 1A and 1B, the group of light reflecting portions 31 moves in the radial direction D2 as the scale S rotates, and the position of the group of light reflecting portions 31 when the scale S rotates once. Returns to the predetermined position. Therefore, the position detection in the radial direction D2 is within the range where the scale S makes one rotation. In the optical pattern 30, the position of the group of light reflecting portions 31 in the radial direction D2 corresponds to the phase angle θ of the scale S. Therefore, the absolute position information (absolute information) of the scale S can be detected by detecting the position of the detection signal in the radial direction D2.

  FIG. 2B shows the intensity distribution of light reflected by the light reflecting portions 31 arranged in the rotation direction D1 in the optical pattern 30, and shows an incremental signal. The horizontal axis of the graph shown in FIG. 2B shows the time axis, and the vertical axis of the graph shows the magnitude of the signal intensity value of the output signal. The detection signal here is a detection signal obtained by integrating the detection values of the light reflected by the light reflecting portion 31 for one round in the radial direction D2.

  As shown in FIG. 2B, the photodetection unit 40 obtains a graph of the high frequency signal. As the optical pattern 30 moves (rotates), the light reflecting portions 31 arranged in the rotation direction D1 move in the rotation direction D1. As described above, both ends of the light reflecting portion 31 in the rotation direction D1 are arranged on the two imaginary straight lines set at the angle θ1 with the rotation axis AX as the center, so that the rotation axis in the radial direction D2 The same detection signal is obtained in the light reflecting portion 31 disposed on the AX side and the light reflecting portion 31 disposed on the outer periphery in the radial direction D2. Incremental information in the rotation direction D1 of the optical pattern 30 is obtained based on the high-frequency signal.

  As described above, according to the first embodiment, the light reflection portions 31 and the reflection suppression portions 32 are alternately arranged along the spiral trajectory so that the pitch P is set in the radial direction D2 around the rotation axis AX. It is possible to form a configuration in which the light reflectance changes and the light reflectance changes for each angle α in the rotation direction D1. For this reason, both absolute position information and incremental information can be generated as described above. Therefore, it is not necessary to form a plurality of types of patterns on the scale S, and the scale S can be reduced. Thereby, an encoder can be reduced in size.

  FIG. 3 is a cross-sectional view showing an example of an encoder using the encoder scale S shown in FIG. In the following description, components that are the same as or equivalent to those in the above-described embodiment are denoted by the same reference numerals, and description thereof is omitted or simplified. As shown in FIG. 3A, the encoder EC includes a scale (encoder scale) S, a main body B, and a controller CONT. As the scale S, the scale S of the first embodiment described above is used. The scale S is fixed to a shaft portion SF such as a rotary motor and rotates integrally with the shaft portion SF. The main body B is fixed to a non-rotating part BD, such as a casing of a rotary motor, and has a housing 39 and a light detection part 40. The light detection unit 40 detects light via the optical pattern 30 described above. The housing 39 may include an adjustment mechanism for adjusting the position of the light detection unit 40 with respect to the scale S.

  FIG. 3B is a plan view illustrating an example of the light detection unit 40. As shown in FIG. 3B, the light detection unit 40 has a chip substrate 40a formed in a rectangular shape in plan view. A light emitting unit 41, a light receiving unit 42, and a control circuit 43 are formed on the chip substrate 40a.

  The light emitting unit 41 emits detection light to the optical pattern 30 described above. The light emitting unit 41 includes a light emitting element 41a, a connection unit 41b, and a cathode electrode 41c, and further includes an anode electrode (not shown) and the like. The light emitting element 41a has a light emission region 41d. The light emission region 41d is formed so as to emit laser light having a predetermined wavelength in one direction or a plurality of directions. The connection portion 41b and the cathode electrode 41c are connected by, for example, a lead wire.

The light receiving unit 42 receives light via the optical pattern 30. In the present embodiment, the reflected light from the optical pattern 30 is received. The light receiving unit 42 includes a plurality of light receiving elements 42a. For example, a two-dimensional sensor (image sensor) is used as the light receiving element 42a. Examples of the two-dimensional sensor include a CCD (Charge Coupled Device) and a CMOS (Complementary).
Metal Oxide Semiconductor) image sensors are used.

  A plurality of light receiving elements 42a are arranged side by side in the direction along the rotation direction D1 and in the direction along the radial direction D2. The arrangement of the light receiving elements 42a (positions in the rotation direction D1 and the radial direction D2) corresponds to the arrangement of the optical pattern 30. Therefore, one light receiving element 42 a corresponds to one light reflecting portion 31 or reflection suppressing portion 32. For this reason, one of the two light receiving elements 42a adjacent to each other in the rotational direction D1 or the radial direction D2 corresponds to the light reflecting portion 31, and the other corresponds to the reflection suppressing portion 32. However, the arrangement number of the light receiving elements 42 a can be appropriately changed according to the configuration of the optical pattern 30. For example, you may arrange | position so that the some light receiving element 42a may respond | correspond to one light reflection part 31 grade | etc.,.

  The light receiving unit 42 can detect by switching between two detection modes, a detection mode for detecting an absolute signal and a detection mode for detecting an incremental signal. FIGS. 3C and 3D are diagrams schematically illustrating two detection modes in the light receiving unit 42. The detection mode shown in FIG. 3C is a detection mode in which the detection results of the light receiving elements 42a arranged in the rotation direction D1 are integrated and output for each column, and an absolute signal is detected. In this detection mode, the light receiving unit 42 functions in the same manner as when the light receiving elements 42c are arranged in a strip shape that is long in the rotation direction D1 as shown in FIG. In this case, the light reflected by the light reflecting portions 31 arranged in the rotation direction D1 in the optical pattern 30 can be detected in a state where the light is integrated for each strip.

  In addition, the detection mode shown in FIG. 3D is a detection mode in which the detection results of the light receiving elements 42a arranged in the radial direction D2 are integrated and output for each column, and an incremental signal is detected. In this detection mode, it functions in the same manner as when the light receiving elements 42d are arranged in a strip shape long in the radial direction D2 as shown in FIG. 3 (d). In this case, the light reflected by the group of light reflecting portions 31 arranged in the one radial direction D2 from the rotation axis AX can be detected in a state of being integrated for each strip.

  FIG. 4 is a diagram schematically illustrating a circuit configuration of the light receiving unit 42. As shown in FIG. 4, the light receiving unit 42 includes a first signal line 42p and a second signal line 42q, and a first output line 42r and a second output line 42s. The first signal line 42p receives a control signal and is connected to a plurality of signal lines (signal lines 42p1, 42p2, 42p3, 42p4,...). The second signal line 42q is connected to a plurality of signal lines (signal lines 42q1, 42q2, 42q3, 42q4,...). The first output line 42r has a plurality of output lines (output lines 42r1, 42r2, 42r3, 42r4,...). The second output line 42s has a plurality of output lines (output lines 42s1, 42s2, 42s3, 42s4,...).

  The light receiving element 42a includes a photodiode 42b, a first transistor 42m, and a second transistor 42n. The gate electrode of the first transistor 42m is connected to the first signal line 42p via a plurality of signal lines 42p1, 42p2, 42p3, 42p4,. The source electrode of the first transistor 42m is connected to the photodiode 42b. The drain electrode of the first transistor 42m is connected to the first output line 42r (output lines 42r1, 42r2, 42r3, 42r4,...) Via the light receiving elements 42a arranged in the radial direction D2.

  The gate electrode of the second transistor 42n is connected to the second signal line 42q via a plurality of signal lines 42q1, 42q2, 42q3, 42q4,. The source electrode of the second transistor 42n is connected to the photodiode 42b. The drain electrode of the second transistor 42n is connected to the second output line 42s (output lines 42s1, 42s2, 42s3, 42s4,...) Via the light receiving elements 42a arranged in the rotation direction D1.

  In addition, the light receiving unit 42 is provided with a switching circuit 42e. The switching circuit 42e can switch on and off control signals input to the first signal line 42p and the second signal line 42q, respectively.

  Here, an operation for switching between a detection mode for detecting an absolute signal and a detection mode for detecting an incremental signal will be described. In order to switch between the two detection modes in the light receiving unit 42, switching is performed so that a control signal is input to either the first signal line 42p or the second signal line 42q by the switching circuit 42e.

  For example, when a control signal is input to the first signal line 42p and no control signal is input to the second signal line 42q, the control signal is input to the gate electrode of the first transistor 42m of each light receiving element 42a, and the second A control signal is not input to the gate electrode of the transistor 42n. For this reason, the output signal from the photodiode 42b is transmitted to the first output line 42r (output lines 42r1, 42r2, 42r3, 42r4,...) Via the plurality of light receiving elements 42a arranged in the radial direction D2. For this reason, the output results of the plurality of light receiving elements 42a arranged in the radial direction D2 are integrated and transmitted to the first output line 42r. Accordingly, as shown in FIG. 3D, the light receiving unit 42 integrates and outputs the signals of the light receiving elements 42d arranged in the radial direction D2.

  In this case, one of the light receiving elements 42a adjacent to the rotation direction D1 corresponds to the light reflecting portion 31, and the other corresponds to the reflection suppressing portion 32. Therefore, when the detection result of one light receiving element array (the output signal output to the output line 42r1) is a result corresponding to the light reflecting portion 31, the detection result of the other light receiving element array (output to the output line 42r2). The output signal) corresponds to the reflection suppression unit 32. In this case, the output signal output to the output line 42r3 corresponds to the light reflection unit 31, and the output signal output to the output line 42r4 corresponds to the reflection suppression unit 32. In this way, the same type of output signal is transmitted to the first output lines 42r arranged in every other direction in the rotation direction D1. In this embodiment, the output results transmitted to the output lines 42r1, 42r3,... Are transmitted to the output line 42t and integrated, and the transmission results transmitted to the output lines 42r2, 42r4,. Accumulated.

  On the other hand, when a control signal is input to the second signal line 42q and no control signal is input to the first signal line 42p, the control signal is input to the gate electrode of the second transistor 42n of each light receiving element 42a, and the first No control signal is input to the gate electrode of the transistor 42m. For this reason, the output signal from the photodiode 42b is transmitted to the second output line 42s (output lines 42s1, 42s2, 42s3, 42s4,...) Via the plurality of light receiving elements 42a arranged in the rotation direction D1. For this reason, the output results of the plurality of light receiving elements 42a arranged in the rotation direction D1 are integrated and transmitted to the second output line 42s. Thus, as shown in FIG. 3C, the light receiving unit 42 integrates and outputs the signals of the light receiving elements 42c arranged in the rotation direction D1.

  In this case, one of the two rows of light receiving elements 42a adjacent in the radial direction D2 corresponds to the light reflecting portion 31, and the other corresponds to the reflection suppressing portion 32. Therefore, when the detection result of one light receiving element array (the output signal output to the output line 42s1) is a result corresponding to the light reflecting portion 31, the detection result of the other light receiving element array (output to the output line 42s2). The output signal) corresponds to the reflection suppression unit 32. In this case, the output signal output to the output line 42s3 corresponds to the light reflection unit 31, and the output signal output to the output line 42s4 corresponds to the reflection suppression unit 32. In this way, the same kind of output signals are transmitted to the first output lines 42r arranged every other line in the radial direction D2. In this embodiment, the output results transmitted to the output lines 42s1, 42s3,... Are transmitted to the output line 42v and integrated, and the transmission results transmitted to the output lines 42s2, 42s4,... Are transmitted to the output line 42w. Accumulated.

  FIG. 5 is a functional block diagram showing the control circuit 43 of the chip substrate 40a. As illustrated in FIG. 5, the chip substrate 40 a is provided with a processing unit 44 that processes the detection result of the light receiving unit 42. Based on the output signal (absolute signal ABS: first phase signal) regarding the radial direction D2 and the output signal (incremental signal INC: second phase signal) regarding the rotation direction D1, the processing unit 44 performs one rotation information ST. Is calculated. The single rotation information ST includes absolute position information (absolute information). The processing unit 44 outputs position information including the one-rotation information ST to the control unit CONT by, for example, a serial communication method in response to a request from the control unit CONT. Note that the single rotation information ST in the present embodiment is absolute position information, but may be relative position information.

  Next, the operation of the encoder EC after the power is turned on will be described. FIG. 6 is a flowchart showing the operation of the encoder EC. After the encoder EC is powered on, the control unit CONT is initialized. Thereafter, the control unit CONT instructs the switching circuit 42e of the light receiving unit 42 not to input the control signal to the first signal line 42p and to input the control signal to the second signal line 42q. With this operation, the light receiving unit 42 enters a detection mode for detecting an absolute signal (step ST01).

  In this state, the control unit CONT causes the light emitting unit 41 to emit light to the optical pattern 30 and causes the light receiving unit 42 to detect reflected light from the optical pattern 30. In the light receiving unit 42, an absolute signal is detected as shown in FIG. 2A (step ST02). Note that the phase resolution of the light receiving unit 42 at this time can be set to 512 divisions, for example.

  Thereafter, the control unit CONT instructs the switching circuit 42e of the light receiving unit 42 not to input a control signal to the second signal line 42q and to input a control signal to the first signal line 42p. By this operation, the light receiving unit 42 is switched to a detection mode for detecting an incremental signal (step ST03).

  In this state, the control unit CONT causes the light emitting unit 41 to emit light to the optical pattern 30 and causes the light receiving unit 42 to detect reflected light from the optical pattern 30 as described above. In the light receiving unit 42, an incremental signal is detected as shown in FIG. 2B (step ST04). At this time, the pitch (angle α) at which the reflectance changes in the rotation direction D1 of the optical pattern 30 is the same as the phase resolution of the absolute signal, for example, 512 divisions. Furthermore, the resolution of the absolute signal can be supplemented by interpolating the incremental signal. Note that the detection light is not limited to being emitted from the light emitting unit 42 in steps ST03 and ST04, respectively, and the switching circuit 42e is switched while one detection light is being emitted so as to obtain an absolute signal and an incremental signal. It may be.

  Thereafter, the processing unit 44 calculates the absolute position information of the scale S by associating the two signals of the absolute signal and the incremental signal (step ST05). Thereafter, the control unit CONT measures rotation information by adding incremental information to the absolute position information (step ST06).

  In the encoder EC, since the scale S in which the light reflecting portions 31 and the reflection suppressing portions 32 are alternately arranged along the spiral trajectory is used, the pitch P extends in the radial direction D2 around the rotation axis AX. It is possible to form the optical pattern 30 in which the light reflectivity changes and the light reflectivity changes for each angle α in the rotation direction D1. For this reason, as described above, both the absolute position information and the incremental information can be generated by one optical pattern 30. Therefore, it is not necessary to form a plurality of types of patterns on the scale S, and the scale S can be reduced. Thereby, an encoder can be reduced in size. The effect of such an encoder EC is the same in other embodiments and modifications described below.

Second Embodiment
The second embodiment will be described. In the first embodiment described above, the configuration in which the optical pattern 30 is formed as the scale S along one spiral trajectory has been described as an example. However, the present invention is not limited to this, and two spiral trajectories are used. The optical pattern 30 may be formed along the line. Note that the same or equivalent components as those of the above-described embodiment are denoted by the same reference numerals, and description thereof is omitted or simplified.

  FIG. 7 is a plan view showing an example of the scale SA according to the second embodiment. FIG. 7 shows the first surface 10a of the substrate 10 in the scale SA. About another structure, it is the same as that of the scale S shown in FIG. As shown in FIG. 7, the optical pattern 130 includes a first spiral pattern 130A and a second spiral pattern 130B. The first spiral pattern 130A and the second spiral pattern 130B are each formed along a so-called Archimedean spiral trajectory. However, in the first spiral pattern 130A and the second spiral pattern 130B, the spiral winding direction is opposite.

  The first spiral pattern 130A includes a light reflecting portion 131A and a reflection suppressing portion 132A. The light reflecting portions 131A and the reflection suppressing portions 132A are alternately arranged in the rotation direction D1. For this reason, in the first spiral pattern 130A, the light reflectance changes in the rotation direction D1 with a predetermined period. The change in the light reflectance along the rotation direction D1 in the first spiral pattern 130A is used as an incremental pattern.

  Further, the light reflecting portions 131A and the reflection suppressing portions 132A are alternately arranged in the radial direction D2. Therefore, in the first spiral pattern 130A, the light reflectance changes in the radial direction D2 with a predetermined period. Of the first spiral pattern 130A, with respect to a group (four) of light reflecting portions 131A arranged in one radial direction D2 from the rotation axis AX, the group of light reflecting portions 131A is opposite to the position of the light reflecting portion 131X. It arrange | positions so that the position on radial direction D2 may approach the outer peripheral side, so that phase angle (theta) becomes large clockwise. Such an arrangement of the group of light reflecting portions 131A is used as an absolute pattern.

  The second spiral pattern 130B has a light reflecting portion 131B and a reflection suppressing portion 132B. The light reflecting portions 131B and the reflection suppressing portions 132B are alternately arranged in the rotation direction D1. For this reason, in the second spiral pattern 130B, the light reflectance changes in the rotation direction D1 with a predetermined period. Note that the light reflecting portion 131A and the reflection suppressing portion 132A are arranged at every predetermined angle α in the rotation direction D1. Moreover, the light reflection part 131B and the reflection suppression part 132B are arrange | positioned for every predetermined angle (alpha) regarding the rotation direction D1. Further, the light reflecting portion 131A and the light reflecting portion 131B are arranged side by side in the radial direction D2. Therefore, in the second spiral pattern 130B, the light reflectance change period in the rotation direction D1 is the same as the light reflectance change period in the rotation direction D1 in the first spiral pattern 130A. The change in the light reflectance along the rotation direction D1 in the second spiral pattern 130B is used as an incremental pattern similar to the first spiral pattern 130A.

  Further, the light reflecting portions 131B and the reflection suppressing portions 132B are alternately arranged in the radial direction D2. Therefore, in the second spiral pattern 130B, the light reflectance changes in the radial direction D2 at a predetermined period. Of the second spiral pattern 130B, for the group (four) of light reflecting portions 131B arranged in the radial direction D2 from the rotation axis AX, the group of light reflecting portions 131B is counteracted with respect to the position of the light reflecting portion 131Y. As the phase angle θ increases in the clockwise direction, the position in the radial direction D2 is arranged closer to the rotation axis AX. Such an arrangement of the group of light reflecting portions 131B is used as an absolute pattern.

  The light reflecting portions 131A and the reflection suppressing portions 132A are arranged side by side at a pitch P1 equal to the radial direction D2. The light reflecting portions 131B and the reflection suppressing portions 132B are arranged side by side at a pitch P2 equal to the radial direction D2. The pitch P1 of the light reflecting part 131A and the reflection suppressing part 132A and the pitch P2 of the light reflecting part 131B and the reflection suppressing part 132B may be the same value or different values. When the pitch P1 and the pitch P2 have different values, different absolute signals are detected between the first spiral pattern 130A and the second spiral pattern 130B. Further, the distance in the radial direction between the first spiral pattern 130A and the second spiral pattern 130B may be either the pitch P1 or the pitch P2 described above, or may be a distance different from the pitches P1 and P2.

  FIG. 8A is a cross-sectional view showing an example of an encoder ECA using the encoder scale SA shown in FIG. Note that the same or equivalent components as those of the above-described embodiment are denoted by the same reference numerals, and description thereof is omitted or simplified. As shown in FIG. 8A, the encoder ECA includes a scale (encoder scale) SA, a main body B, and a controller CONT. The scale SA is the scale SA described above. The scale SA is fixed to a shaft portion SF such as a rotary motor and rotates integrally with the shaft portion SF. The main body part B is fixed to the non-rotating part BD and includes a housing 39 and a light detection part 140. The light detection unit 140 detects light via the optical pattern 130 described above. The housing 39 may include an adjustment mechanism for adjusting the position of the light detection unit 140 with respect to the scale SA.

  FIG. 8B is a plan view illustrating an example of the light detection unit 140. As shown in FIG. 8B, the light detection unit 140 has a chip substrate 140a formed in a rectangular shape in plan view. A light emitting unit 141, a light receiving unit 142, a control circuit 143, a correcting unit 144, and a processing unit 145 are formed on the chip substrate 140a.

  The light emitting unit 141 is formed to illuminate the detection light with respect to both the first spiral pattern 130A and the second spiral pattern 130B of the optical pattern 130 described above. The light receiving unit 142 includes a first light receiving unit 142A and a second light receiving unit 142B. The first light receiving unit 142A receives light (eg, reflected light) via the first spiral pattern 130A. The second light receiving unit 142B receives light (eg, reflected light) via the second spiral pattern 130B.

  The first light receiving unit 142A and the second light receiving unit 142B have a plurality of light receiving elements 142Aa and 142Ba, respectively. As the light receiving elements 142Aa and 142Ba, an image sensor such as a CCD or a CMOS is used as in the first embodiment. A plurality of light receiving elements 142Aa and 142Ba are arranged side by side in the direction along the rotational direction D1 and in the direction along the radial direction D2. The arrangement of the light receiving elements 142Aa (positions in the rotation direction D1 and the radial direction D2) corresponds to the arrangement of the first spiral pattern 130A. The arrangement of the light receiving elements 142Ba corresponds to the arrangement of the second spiral pattern 130B. Further, as in the first embodiment, the light receiving unit 142 can detect by switching between two detection modes of a detection mode for detecting an absolute signal and a detection mode for detecting an incremental signal.

  FIG. 9 is a functional block diagram showing a control circuit of the chip substrate 140a. As shown in FIG. 9, the chip substrate 140a is provided with a correction unit 144 that corrects the detection result of the light receiving unit 142 and a processing unit 145 that processes the corrected detection result.

  The correction unit 144 includes a first correction unit 144a and a second correction unit 144b. The first correction unit 144a obtains a differential result between the absolute signal (first phase signal) obtained from the first spiral pattern 130A and the absolute signal (third phase signal) obtained from the second spiral pattern 130B. Based on the above, an absolute correction signal (first correction phase signal) is generated. Based on the addition result of the absolute signal obtained from the first spiral pattern 130A and the absolute signal obtained from the second spiral pattern 130B, the second correction unit 144b performs the rotation axis AX of the scale SA and the first The amount of eccentricity with respect to the center of the spiral pattern 130A or the second spiral pattern 130B is calculated.

  FIG. 10 is a graph for explaining the correction operation by the first correction unit 144a and the second correction unit 144b. The horizontal axis of the graph shown in FIG. 10 indicates the magnitude of the rotation angle of the scale SA, and the vertical axis of the graph indicates the signal value (radius) of the absolute signal output from the first light receiving unit 142A and the second light receiving unit 142B. The position in the direction D2).

  The detection light emitted from the light emitting unit 141 is reflected by the first spiral pattern 130A and the second spiral pattern 130B, respectively. The reflected light that passes through the first spiral pattern 130A is received by the first light receiving unit 142A. The reflected light that has passed through the second spiral pattern 130B is received by the second light receiving unit 142B. In the present embodiment, the first spiral pattern 130A and the second spiral pattern 130B are opposite in the traveling direction of the phase in the radial direction during rotation. For this reason, the moving direction of the absolute signal obtained from the first light receiving unit 142A is opposite to the moving direction of the absolute signal obtained from the second light receiving unit 142B. Therefore, as shown in FIG. 10, when the signal obtained by the first light receiving unit 142A takes a positive value, the signal obtained by the second light receiving unit 142B takes a negative value. Further, the absolute values of these signals increase in proportion to the rotation angle.

The first correction unit 144a performs the following correction process. When there is an eccentricity between the rotation axis AX of the scale SA and the center of the first spiral pattern 130A or the second spiral pattern 130B, the absolute signals obtained by the first light receiving unit 142A and the second light receiving unit 142B are: As shown in FIG. 10, an error of one period occurs every time the scale SA rotates once. The error due to the eccentricity is generated by the same amount in both the first light receiving unit 142A and the second light receiving unit 142B. When the absolute signal value obtained from the first light receiving unit 142A is ABSa and the absolute signal value obtained from the second light receiving unit 142B is ABSb, the first correction unit 144a is:
(ABSa-ABSb) / 2
The absolute correction signal in which the influence of eccentricity is canceled is calculated (see the straight wavy line in FIG. 10). By obtaining the above value, in addition to the eccentricity, the above-described ABSa value and ABSb value simultaneously overlap by the same amount (for example, the influence of the optical insulator due to the shaft shake or the light source light amount fluctuation) is cancelled. Can do. Thereby, a highly accurate detection result can be obtained.

The second correction unit 144b measures the amount of eccentricity ε in real time by calculating with (ABSa + ABSb) / 2. In this case, if the detection radius is R, the eccentric error ERR of the encoder ECA is
ERR = 2 tan ⁻¹ (ε / R) (2)
It is represented by

  The second correction unit 144b obtains the incremental signal (second phase signal) obtained from the first spiral pattern 130A or the second spiral pattern 130B based on the eccentric error ERR calculated as described above. An incremental correction signal can be generated from the incremental signal (fourth phase signal). That is, based on the calculated eccentricity error ERR, an incremental correction signal is generated by correcting the detection error due to the eccentricity error ERR with respect to the second phase signal and the fourth phase signal.

  Returning to FIG. 9, the correction unit 144 sends an absolute signal (absolute correction signal calculated by the first correction unit 144 a) ABS and an incremental signal (incremental correction signal calculated by the second correction unit 144 b) INC to the processing unit 145. Output. However, in addition to these correction signals, for example, an absolute signal obtained by the first light receiving unit 142A, an absolute signal obtained by the second light receiving unit 142B, an incremental signal obtained by the first light receiving unit 142A, the second Incremental signals obtained by the light receiving unit 142B may be output to the processing unit 145.

  The processing unit 145 calculates one rotation information ST based on the absolute signal ABS and the incremental signal INC output from the correction unit 144. The processing unit 145 outputs position information including the one-rotation information ST to the control unit CONT by a request from the control unit CONT, for example, by a serial communication method or the like.

  According to the encoder ECA of the second embodiment, the first spiral pattern 130A and the second spiral pattern 130B having different winding directions are formed on the scale SA. Therefore, using these two patterns, the absolute position information and By acquiring the incremental information, the eccentricity between the rotation axis AX of the scale SA and the centers of the first spiral pattern 130A and the second spiral pattern 130B can be detected. Thereby, it is possible to obtain a highly accurate detection result from which the eccentricity error is removed.

<First Modification>
In the second embodiment described above, the configuration in which the first spiral pattern 130A and the second spiral pattern 130B having different winding directions are formed on the scale SA is described as an example. However, the present invention is not limited to this. Instead, the winding directions of the first spiral pattern 130A and the second spiral pattern 130B may be the same. FIG. 11 is a plan view illustrating an example of the scale SB according to the first modification. In FIG. 11, the scale SB and the light detection unit 140 are illustrated, and other configurations relating to the encoder are the same as those of the encoder ECA described in the second embodiment. In FIG. 11, the scale SB is indicated by a solid line, and the light detection unit 140 is indicated by a broken line. Note that the same or equivalent components as those of the above-described embodiment are denoted by the same reference numerals, and description thereof is omitted or simplified.

  As shown in FIG. 11, the scale SB has an optical pattern 230. The optical pattern 230 has a first spiral pattern 230A and a second spiral pattern 230B. The first spiral pattern 230A and the second spiral pattern 230B are each formed along the path of the Archimedean spiral. Therefore, the spiral direction of the spiral is the same in the first spiral pattern 230A and the second spiral pattern 230B.

  The first spiral pattern 230A includes a light reflecting portion 231A and a reflection suppressing portion 232A. The light reflecting portions 231A are arranged at predetermined angles α in the rotation direction D1, and are arranged side by side in the radial direction D2. The light reflecting portions 231A are arranged side by side at a pitch P3 equal to the radial direction D2. The reflection suppressing unit 232B is disposed so as to fill the gap between the light reflecting units 231A. Regarding the group (four) of light reflecting portions 231A arranged in the one radial direction D2 from the rotation axis AX in the first spiral pattern 230A, the group of light reflecting portions 231A is opposite to the position of the light reflecting portion 231X as a reference. It arrange | positions so that the position on radial direction D2 may approach the outer peripheral side, so that phase angle (theta) becomes large clockwise.

  The second spiral pattern 230B includes a light reflecting portion 231B and a reflection suppressing portion 232B. The light reflecting portions 231B are arranged at predetermined angles α in the rotation direction D1, and are arranged side by side in the radial direction D2. The light reflecting portions 231B are arranged side by side at a pitch P4 equal to the radial direction D2. The reflection suppressing unit 232B is disposed so as to fill the gap between the light reflecting units 231B. Regarding the group (two) of light reflecting portions 231B arranged in the radial direction D2 from the rotation axis AX in the second spiral pattern 230B, the group of light reflecting portions 231B is opposite to the position of the light reflecting portion 231Y. It arrange | positions so that the position on radial direction D2 may approach the outer peripheral side, so that phase angle (theta) becomes large clockwise.

  In the radial direction D2, the pitch (P4) of the light reflecting portions 231B is set to be twice the pitch (P3) of the light reflecting portions 231A. For this reason, in the radial direction D2, the number of the light reflecting portions 231B is half of the number of the light reflecting portions 231A. In FIG. 11, the first spiral pattern 230 </ b> A and the second spiral pattern 230 </ b> B are formed to be continuous, but the present invention is not limited to this, and both may be arranged apart in the radial direction D <b> 2.

  The light detection unit 140 has the same configuration as that of the second embodiment. The light emitting unit 141 illuminates detection light on both the first spiral pattern 230A and the second spiral pattern 230B of the optical pattern 230 described above.

  The first light receiving unit 142A of the light receiving unit 142 receives light (eg, reflected light) via the first spiral pattern 230A. The second light receiving unit 142B of the light receiving unit 142 receives light (eg, reflected light) via the second spiral pattern 230B. The arrangement (positions in the rotational direction D1 and the radial direction D2) of the light receiving elements 142Aa of the first light receiving unit 142A corresponds to the arrangement of the first spiral pattern 230A. The arrangement of the light receiving elements 142Ba of the second light receiving unit 142B corresponds to the arrangement of the second spiral pattern 230B. Similarly to the second embodiment, the light receiving unit 142 switches between two detection modes, ie, a detection mode for detecting an absolute signal and a detection mode for detecting an incremental signal.

  FIG. 12 is a graph for explaining the correction operation by the first correction unit 144a and the second correction unit 144b in the first modification. The horizontal axis of the graph shown in FIG. 12 indicates the magnitude of the rotation angle of the scale SB, and the vertical axis of the graph indicates the signal value (radius) of the absolute signal output from the first light receiving unit 142A and the second light receiving unit 142B. The position in the direction D2).

  The detection light emitted from the light emitting unit 141 is reflected by the first spiral pattern 230A and the second spiral pattern 230B, and received by the first light receiving unit 142A and the second light receiving unit 142B, respectively. In this embodiment, the first spiral pattern 230A and the second spiral pattern 230B have the same traveling direction of the phase in the radial direction during rotation. For this reason, the movement direction of the absolute signal obtained from the first light receiving unit 142A and the movement direction of the absolute signal obtained from the second light receiving unit 142B are the same direction. Accordingly, as shown in FIG. 12, the signals obtained by the first light receiving unit 142A and the second light receiving unit 142B both take a positive value.

  Further, since the pitches P3 and P4 in the radial direction D2 are different between the first spiral pattern 230A and the second spiral pattern 230B, the signal values are different in proportion to the rotation angle. Since the pitch P4 of the second spiral pattern 230B is set to twice the pitch P3 of the first spiral pattern 230A, as shown in FIG. The signal value (2A) is double the signal value (A) in the two light receiving units 142.

The first correction unit 144a performs the following correction process. When there is an eccentricity between the rotation axis AX of the scale SB and the center of the first spiral pattern 230A or the second spiral pattern 230B, the absolute signals obtained by the first light receiving unit 142A and the second light receiving unit 142B are: As shown in FIG. 12, every time the scale SB rotates once, an error for one cycle occurs. The phase of error due to eccentricity is generated by the same amount in both the first light receiving unit 142A and the second light receiving unit 142B. When the absolute signal value obtained from the first light receiving unit 142A is ABSc, the absolute signal value obtained from the second light receiving unit 142B is ABSd, and the eccentricity is ε,
ABSc = 2A + ε
ABSd = A + ε
It is.

Therefore, by calculating the difference between ABSc and ABSd,
ABSc−ABSd = (2A + ε) − (A + ε)
And
ABSc-ABSd = A
Thus, the influence of the eccentricity is canceled, and the signal value (A) of the absolute signal at the second light receiving unit 142B can be obtained. Further, by doubling the value (A) thus obtained, the signal value (2A) of the absolute signal at the first light receiving unit 142A when the influence of the eccentricity is canceled can be obtained. By obtaining the above values, in addition to the eccentricity, the above-described fluctuations in which the ABSc value and the ABSd value are simultaneously superimposed by the same amount (for example, the influence of the optical insulator due to the shaft shake or the light source light quantity fluctuation) are canceled. Can do. As a result, a highly accurate detection result in which the eccentricity error is corrected can be obtained.

The first correction unit 144a can measure the eccentricity ε2 in real time by calculating (ABSd−A) using the value (A) calculated as described above. In this case, assuming that the detection radius is R2, the eccentric error ERR2 of the scale SB is similar to the above-described equation 2,
ERR2 = 2 tan ⁻¹ (ε2 / R2) (3)
It is represented by

  The second correction unit 144b obtains the incremental signal (second phase signal) obtained from the first spiral pattern 230A or the second spiral pattern 230B based on the eccentric error ERR2 calculated as described above. An incremental correction signal can be generated from the incremental signal (fourth phase signal).

  In the first modification, the configuration in which the pitch (P4) of the light reflecting portions 231B is set to twice the pitch (P3) of the light reflecting portions 231A in the radial direction D2 has been described as an example. However, the present invention is not limited to this. If the pitch P3 and the pitch P4 are not the same, the pitch P4 can be arbitrarily set, for example, three times the pitch P3.

<Third Embodiment>
A scale according to the third embodiment will be described. FIG. 13A is a plan view showing an example of the scale SC according to the third embodiment, and also shows an enlarged view of a part of the scale SC. In the following description, the same or equivalent components as those of the above-described embodiment are denoted by the same reference numerals, and the description thereof is omitted or simplified. As shown in FIG. 13A, the scale SC has an optical pattern 330. The optical pattern 330 has a first spiral pattern 330A and a second spiral pattern 330B. In the first spiral pattern 330A and the second spiral pattern 330B, the spiral winding direction is opposite to that of the scale SA shown in FIG.

  The first spiral pattern 330A includes a light reflecting portion 331A and a reflection suppressing portion 332A. In addition, the second spiral pattern 330B includes a light reflecting portion 331B and a reflection suppressing portion 332B. The light reflecting portions 331A and 331B are arranged for each predetermined angle α (second pitch) in the rotation direction D1.

  On the other hand, between the first spiral pattern 330A and the second spiral pattern 330B, the phase is set in a state shifted in the rotation direction D1. This phase shift is an angle 1/4 (α / 4) of the angle α. In this way, between the light reflecting portion 331A and the light reflecting portion 331B, the pitch α at which the light reflectance changes is the same, but the phase is shifted by α / 4.

  Therefore, when the incremental signal of the optical pattern 330 is detected by the light detection unit, the phase of the incremental signal related to the first spiral pattern 330A and the phase of the incremental signal related to the second spiral pattern 330B are shifted by 90 °. Detected. Thus, since a two-phase incremental signal whose phase is shifted by 90 ° can be obtained, the rotation direction of the scale SC can be detected depending on which of the incremental signals is acquired first. For example, when the scale SC rotates in the clockwise direction, the incremental signal related to the second spiral pattern 330B is acquired first, and the incremental signal related to the first spiral pattern 330A is acquired with the phase shifted by 90 °.

<Second Modification>
The scale according to the second modification will be described. FIG. 13B is a plan view showing an example of the scale SD according to the second modification. FIG. 13B shows a part of the scale SD. In the following description, the same or equivalent components as those of the above-described embodiment are denoted by the same reference numerals, and the description thereof is omitted or simplified. As shown in FIG. 13B, the scale SD has an optical pattern 430. The optical pattern 430 has a first spiral pattern 430A and a second spiral pattern 430B. Each of the first spiral pattern 430A and the second spiral pattern 430B is formed along the trajectory of one Archimedean spiral. The spiral winding directions of the first spiral pattern 430A and the second spiral pattern 430B are the same.

  The first spiral pattern 430A includes a light reflecting portion 431A and a reflection suppressing portion 432A. The second spiral pattern 430B includes a light reflection portion 431B and a reflection suppression portion 432B. The light reflecting portions 431A are arranged at a predetermined pitch P (first pitch) in the radial direction D2. The light reflecting portions 431B are arranged at a predetermined pitch P (first pitch) in the radial direction D2.

  On the other hand, the interval (pitch) is shifted in the radial direction D2 between the first spiral pattern 430A and the second spiral pattern 430B. The gap is ¼ (P / 4) of the pitch P. As described above, the light reflecting portion 431A and the light reflecting portion 431B have the same pitch P at which the light reflectance changes, but are shifted so that the interval between them is larger by P / 4 than the pitch P. It has become.

  In this configuration, when the absolute signal of the optical pattern 430 is detected by the light detection unit, the phase of the absolute signal related to the first spiral pattern 430A and the phase of the absolute signal related to the second spiral pattern 430B are shifted by 90 °. Detected by state. Thus, since a two-phase absolute signal whose phase is shifted by 90 ° can be obtained, for example, the first spiral pattern 430A and the first spiral pattern 430A and the single light-receiving unit (for example, the light-receiving unit 42 in FIG. 3B) can be obtained. Even when light is received from both of the second spiral patterns 430B, the signals of both can be separated.

  In this modification, the configuration in which the interval between the first spiral pattern 430A and the second spiral pattern 430B is (P + P / 4) has been described as an example, but the present invention is not limited to this. If the interval is different from the pitch P, the same effect as described above can be obtained.

<Fourth embodiment>
An encoder ECB according to the fourth embodiment will be described. FIG. 14A is a plan view showing an example of an encoder ECB according to the fourth embodiment, and FIG. 14B is a cross-sectional view taken along line AA in FIG. The encoder ECB uses the scale S shown in FIG. The AA line of Fig.14 (a) is a curve along the rotation direction D1. FIG. 14B shows a state when the line AA is stretched linearly. Accordingly, in FIG. 14B, the radial direction D2 corresponds to the depth direction of the paper. FIG. 14A shows a part of the scale S and the light detection unit 540, and other configurations relating to the encoder ECB are the same as those of the encoder EC described in the first embodiment. In FIG. 14A, the scale S is indicated by a broken line, and the light detection unit 540 is indicated by a solid line. In the following description, the same or equivalent components as those of the above-described embodiment are denoted by the same reference numerals, and the description thereof is omitted or simplified.

  As shown in FIGS. 14A and 14B, the light detection unit 540 includes a light emitting unit 541, a light receiving unit 42, a control circuit 543, and a modulation unit 544. The light emitting unit 541 includes a first light emitting unit 541A and a second light emitting unit 541B. When the first light emitting unit 541A and the second light emitting unit 541B irradiate the optical pattern 30 with light and receive the reflected light from the optical pattern 30 with the light receiving unit 42, the phase is shifted in the rotation direction D1. It is arranged to be in a state. This phase shift is set to be an angle that is 1/4 (α / 4) of the angle α.

  When the light receiving unit 42 detects the incremental signal of the optical pattern 30, the phase of the incremental signal related to the reflected light obtained from the first light emitting unit 541A through the optical pattern 30 and the optical pattern 30 from the second light emitting unit 541B are detected. The phase of the incremental signal relating to the reflected light obtained through is detected with a 90 ° deviation. Note that the rotation direction of the scale S can be detected by a two-phase incremental signal whose phase is shifted by 90 °, as in the case of using the scale SC shown in the third embodiment.

  Note that the arrangement of the second light emitting unit 541B is not limited to the position where the reflected light is out of phase by α / 4 in the rotation direction D1 with respect to the reflected light from the first light emitting unit 541A as described above. Absent. For example, instead of the second light emitting unit 541B, the third light emitting unit 541C may be provided so that the phase reflected from the light reflected by the first light emitting unit 541A is shifted by P / 4 in the radial direction D2. In this case, a two-phase absolute signal whose phase is shifted by 90 ° can be obtained. Thereby, the same effect as the scale SD shown in the second modified example can be obtained.

  Further, instead of the second light emitting unit 541B, reflected light that is shifted in phase by α / 4 in the rotational direction D1 and shifted by P / 4 in the radial direction D2 with respect to the reflected light from the first light emitting unit 541A is formed. The fourth light emitting unit 541D may be provided at the position. In this case, a two-phase incremental signal whose phase is shifted by 90 ° and a two-phase absolute signal whose phase is shifted by 90 ° can be obtained.

  Further, the modulation unit 544 modulates the light amounts (light intensity) of the detection lights L1 and L2 emitted from the first light emitting unit 541A and the second light emitting unit 541B based on an instruction from the control circuit 543 at a predetermined period. For example, the modulation unit 544 can modulate the detection light L1 and the detection light L2 so that the phases thereof are different. The phase difference at this time is set so as to be shifted by 180 ° so as to be opposite to each other. Thereby, with respect to the scale S, the first light emitting unit 541A and the second light emitting unit 541B alternately illuminate the detection lights L1 and L2. The control circuit 543 of the light detection unit 540 includes a synchronous detection circuit 543a that performs synchronous phase detection.

  As shown in FIG. 14B, the detection light L1 from the first light emitting unit 541A is reflected by the optical pattern 30, and the reflected light L3 reaches the first light receiving region 542A of the light receiving unit 542. The detection light L2 from the second light emitting unit 541B is reflected by the optical pattern 30, and the reflected light L4 reaches the second light receiving region 542B of the light receiving unit 542.

  The light receiving unit 542 alternately receives an incremental signal related to the reflected light L3 and an incremental signal related to the reflected light L4. Based on the information from the synchronous detection circuit 543a, the control circuit 543 generates two incremental signals whose phases are shifted by 90 ° by separating the detected signals into the reflected lights L3 and L4. Accordingly, as described above, the rotation direction of the scale S can be detected based on the two-phase incremental signal whose phase is shifted by 90 °.

  In this configuration, if the modulation unit 544 does not perform modulation, the amount of detection light emitted from the first light emitting unit 541A and the second light emitting unit 541B is constant. In this case, in the first light receiving region 542A, for example, a cosine wave (cosχ) waveform is obtained as the waveform of the incremental signal. In the second light receiving region 542B, for example, a sinusoidal (sin χ) waveform is obtained as the waveform of the incremental signal.

On the other hand, for example, the modulation unit 544 modulates the detection light L1 emitted from the first light emitting unit 541A into a cosine function (cosωt), and the detection light L2 emitted from the second light emitting unit 541B as a sine function. Modulate to (sin ωt). In this case, the amount of light I1 of the reflected light L3 detected in the first light receiving region 542A is
I1 = sin χ cos ωt
It becomes.
In addition, the light amount I2 of the reflected light L4 detected in the second light receiving region 542B is
I2 = cosχsinωt
It becomes.
The variable χ corresponds to the rotational position of the scale S, the frequency ω corresponds to the frequency of light intensity modulation, and the variable t corresponds to time.

Here, the control circuit 543 combines the light amount I1 of the reflected light L3 detected in the first light receiving region 542A and the light amount I2 of the reflected light L4 detected in the second light receiving region 542B. As a result, as a light reception signal,
I1 + I2 = sin χ cos ωt + cos χ sin ωt = sin (ωt + χ) (4)
Is obtained.

  The synchronous detection circuit 543a uses the received light signal sin (ωt + χ) expressed by the equation (4) and the modulation signal sin ωt that modulates the light amount of the second light emitting unit 541B to perform absolute position information of the scale S by synchronous phase detection. Is detected. As described above, the modulation unit 544 modulates the light amounts of the detection lights L1 and L2 emitted from the first light emitting unit 541A and the second light emitting unit 541B, so that the absolute position information can be detected based on the incremental signal. .

  As for the arrangement of the second light emitting unit 541B, the detection light L2 is in a region that is out of phase by α / 4 in the rotation direction D1 with respect to the irradiation region of the detection light L1 from the first light emitting unit 541A. The position is not limited to the position where irradiation is possible. For example, the second light emitting unit 541B is arranged at a position 541C where the detection light L2 can be emitted in a region shifted by P / 4 in the radial direction D2 from the irradiation region of the detection light L1 from the first light emitting unit 541A. May be. In this case, a two-phase absolute signal whose phase is shifted by 90 ° can be obtained.

  Further, the detection light L2 is irradiated to a region where the phase is shifted by α / 4 in the rotation direction D1 and the distance is shifted by P / 4 in the radial direction D2 with respect to the irradiation region of the detection light L1 from the first light emitting unit 541A The second light emitting unit 541B may be arranged at a possible position 541D. In this case, a two-phase incremental signal whose phase is shifted by 90 ° and a two-phase absolute signal whose phase is shifted by 90 ° can be obtained.

  As described above, the present invention is not limited to modulating the light amounts of the detection lights L1 and L2. For example, light having different wavelengths may be used as the detection light L1 and L2, and the light receiving unit 42 may be a light receiving element that can be detected corresponding to each wavelength. In this case, the detection lights L1 and L2 are irradiated simultaneously, but are detected by being separated by the corresponding light receiving elements, and two incremental signals whose phases are shifted by 90 ° can be acquired.

<Third Modification>
An encoder ECF according to a third modification will be described. In the fourth embodiment described above, the configuration in which one light receiving unit 42 is used has been described as an example. However, the configuration is not limited to this, and the light receiving units are provided in two places as in the third modification. It may be a configuration. FIG. 15 is a cross-sectional view illustrating an example of an encoder ECC according to the third modification. As illustrated in FIG. 15, the encoder ECC includes a scale SE and a light detection unit 640. In the following description, the same or equivalent components as those of the above-described embodiment are denoted by the same reference numerals, and the description thereof is omitted or simplified.

  As shown in FIG. 15, the scale SE has an optical pattern 430. The optical pattern 430 has a first spiral pattern 430A and a second spiral pattern 430B. For example, the first spiral pattern 430A and the second spiral pattern 430B have the same spiral winding direction, and the angle α in the rotation direction D1 and the pitch P in the radial direction D2 of the light reflecting portion are set to be the same. Things are used.

  The light detection unit 640 includes a first light emitting unit 541A and a second light emitting unit 541B as light emitting units, a first light receiving unit 642A and a second light receiving unit 642B as light receiving units 642, and a control circuit (not shown). . The first light emitting unit 541A and the second light emitting unit 541B are the same as those in the fourth embodiment described above. The first light receiving unit 642A receives the reflected light of the first spiral pattern 430A by the light emitted from the first light emitting unit 541A. The second light receiving unit 642B receives the reflected light of the second spiral pattern 430B by the light emitted from the second light emitting unit 542A.

  In the third modification, the first light emitting unit 541A and the second light emitting unit 541B are simultaneously irradiated with detection light, and the respective reflected lights are received by the first light receiving unit 642A and the second light receiving unit 642B. In the first spiral pattern 430A and the second spiral pattern 430B, the light reflecting portions are arranged at the same angle α, but the detection light emitted from the first light emitting portion 541A and the second light emitting portion 541B The reflected light is received with a shift of α / 4. As a result, as in the third and fourth embodiments, two incremental signals whose phases are shifted by 90 ° can be acquired. Note that, in the third modified example, the detection light from the first light emitting unit 541A and the second light emitting unit 541B is not limited to being irradiated simultaneously, and, for example, as in the fourth embodiment described above, the phases are opposite to each other. The light intensity may be modulated so that

<Fifth Embodiment>
An encoder ECD according to the fifth embodiment will be described. In the above-described embodiments and modifications, the rotary encoder and the scale used therefor have been described as examples. However, the present invention is not limited to this, and a linear encoder may be used. FIG. 16 is a plan view showing an example of an encoder ECD according to the fifth embodiment. As illustrated in FIG. 16, the encoder ECD includes a scale SG and a light detection unit 740.

  The scale SG is formed in a rectangular plate shape. The scale SG is attached to a stator (linear guide) such as a linear motor. The scale SG is formed to be long in a direction parallel to the moving direction D3 of a mover such as a linear motor. Note that a light detection unit 740 that detects the scale SG is attached to the mover.

  The scale SG has an optical pattern 730. The optical pattern 730 includes a light reflecting portion 731 and a reflection suppressing portion 732. The light reflecting portions 731 are arranged side by side in the movement direction D3 and are arranged in the width direction D4 orthogonal to the movement direction D3. The light reflecting portions 731 are arranged at an equal pitch P5 in the movement direction D3. The light reflecting portions 731 are arranged at an equal pitch P6 in the width direction D4.

  The light reflecting portion 731 is arranged such that the position on the width direction D4 is shifted according to the position on the moving direction D3. The light reflecting portion 731 is arranged so that the position in the width direction D4 gradually shifts from one end (for example, the left end portion in FIG. 16) to the other end (for example, the right end portion in FIG. 16) in the movement direction D3. ing. The interval PL in the width direction D4 between the light reflecting portion 731 disposed at one end in the moving direction D3 and the light reflecting portion 731 disposed at the other end in the moving direction D3 is equal to the pitch P6 in the width direction D4. ing. Accordingly, the optical pattern 730 is set such that the light reflecting portion 731 is shifted by one in the width direction D4 by proceeding the length L in the movement direction D3.

  The reflection suppressing unit 732 is disposed so as to fill the space between the light reflecting units 731 in the movement direction D3 and the width direction D4. The light reflecting portions 731 and the reflection suppressing portions 732 are alternately arranged in the movement direction D3 and the width direction D4. For this reason, in the scale SG, the light reflectance changes in the movement direction D3 at a predetermined cycle. The change in the light reflectance along the moving direction D3 in the optical pattern 730 is used as an incremental pattern.

  Moreover, the light reflection part 731 and the reflection suppression part 732 are alternately arrange | positioned in the width direction D4. Therefore, in the scale SG, the light reflectance changes in the width direction D4 with a predetermined period. Furthermore, the phase of the light reflectance varies depending on the position in the movement direction D3. Therefore, the light reflecting portions 731 in each column arranged in the width direction D4 in the optical pattern 730 are used as an absolute pattern.

  The light detection unit 740 includes a light emitting unit 741, a light receiving unit 742, a control circuit (not shown), and the like. The light emitting unit 741 emits detection light toward the optical pattern 730. The light receiving unit 742 receives reflected light from the optical pattern 730. Note that the light receiving unit 742 is formed, for example, by arranging a plurality of light receiving elements in the movement direction D3 and the width direction D4.

  In this encoder ECD, since the scale SG in which the light reflecting portion 731 and the reflection suppressing portion 732 are alternately arranged in the moving direction D3 and the width direction D4 is used, the change in the light reflectance in the moving direction D3 is an incremental signal. The change in the light reflectance in the width direction D4 can be acquired as absolute position information. In this way, both the absolute position information and the incremental information can be acquired with one optical pattern 730, and for example, the position of the mover relative to the stator can be detected. Further, it is not necessary to form a plurality of types of patterns on the scale SG, the scale SG can be reduced, and the encoder ECD can be reduced in size.

<Drive device>
The drive device according to the embodiment will be described. FIG. 17 is a diagram illustrating an example of an electric motor device MTR as an example of the drive device according to the embodiment. In the following description, components that are the same as or equivalent to those in the above-described embodiment are denoted by the same reference numerals and description thereof is omitted or simplified. As shown in FIG. 17, the motor device MTR includes a shaft portion SF, a main body portion (drive portion) BD that rotationally drives the shaft portion SF, and an encoder EC that detects rotation information of the shaft portion SF. .

  The shaft portion SF has a load side end portion SFa and an anti-load side end portion SFb. The load side end portion SFa is connected to another power transmission mechanism such as a speed reducer. The scale S is fixed to the non-load side end portion SFb via the fixing portion 20. Along with fixing the scale S, an encoder EC is attached. As the scale S and the encoder EC, the first embodiment described above is used, but other embodiments and modifications may be used.

  According to this motor device MTR, since the miniaturized encoder EC is mounted, the entire motor device MTR can be miniaturized. Further, since the small encoder EC is attached to the non-load side end portion SFb, the protrusion from the motor device MTR is reduced, and the motor device MTR can be installed in a small space. Although the motor device MTR has been described as an example of the drive device, the drive device is not limited thereto, and may be another drive device having a shaft portion that rotates using hydraulic pressure or pneumatic pressure.

<Stage device>
The stage apparatus according to the embodiment will be described. FIG. 18 is a perspective view showing an example of the stage apparatus STG according to the embodiment. FIG. 18 shows a configuration in which a rotary table (moving object) TB is attached to the load side end portion SFa of the shaft portion SF of the motor device MTR shown in FIG.

  When the stage device STG configured as described above drives the motor device MTR to rotate the shaft portion SF, this rotation is transmitted to the rotary table TB. At that time, the encoder EC detects the rotational position of the shaft portion SF and the like. Therefore, the rotational position of the rotary table TB can be detected by using the output from the encoder EC.

  Thus, according to the stage apparatus STG, since the small motor apparatus MTR is mounted, the entire stage apparatus STG can be reduced in size. The stage device STG may be applied to a rotary table provided in a machine tool such as a lathe, for example.

  The embodiment has been described above, but the present invention is not limited to the above description, and various modifications can be made without departing from the gist of the present invention. For example, in each of the above-described embodiments and modifications, the scale having a reflective optical pattern has been described as an example. It may be an encoder, a driving device, or a stage device using the. In these light transmissive optical patterns, the same forms as those of the above-described embodiments and modifications can be applied.

  Further, in each of the above-described embodiments, when a plurality of spiral patterns are formed on the scale, it is not limited to receiving the detection light by the plurality of light receiving units. For example, a single light receiving unit may receive reflected light from a plurality of spiral patterns.

  Further, in the case where a plurality of spiral patterns are formed as the encoder scale, one spiral pattern may be used for backup or reference. In this case, when the values from both spiral patterns are compared and one of the values is greatly deviated, one of the values is defective. You may predict whether it is.

  Further, the above-described encoder EC and the like and the driving device (motor device) may be used for a robot device or the like instead of being used for the stage device STG.

S, SA, SB, SC, SD, SG ... scale AX ... rotation axis D1 ... rotation direction D2 ... radial direction α ... angle P, P1, P2, P3, P4 ... pitch EC, ECA, ECB, ECC, ECD ... encoder CONT ... Control part SF ... Shaft part MTR ... Motor device (drive device) STG ... Stage device TB ... Rotary table 30 ... Optical pattern 40 ... Light detection part 41 ... Light emitting part 42 ... Light receiving part 42e ... Switching circuit 44 ... Processing part 130A , 230A, 330A, 430A ... first spiral pattern 130B, 230B, 330A, 430A ... second spiral pattern 144a ... first correction unit 144b ... second correction unit

Claims (19)

An encoder scale comprising a first spiral pattern having a radius continuously changing in a rotation direction around a rotation axis,
The first spiral pattern includes a plurality of first light reflecting portions or a plurality of first light transmitting portions arranged along a locus of a first spiral centered on the rotation axis, first light reflecting portion or the first light transmitting portion, said about an axis of rotation disposed at a first pitch in the radial direction, and are arranged at a second pitch in the direction of the first helical Rue Scale for encoders. Aside from the first spiral pattern, a second spiral pattern having a radius continuously changing in the rotation direction around the rotation axis,
The second spiral pattern has a plurality of second light reflecting portions or a plurality of second light transmitting portions arranged along a locus of a second spiral centering on the rotation axis, light reflection portion or said second light transmitting portion 2, the about an axis of rotation disposed in a third pitch in the radial direction and in the direction of the second helical Ru are arranged at a fourth pitch 請 The encoder scale according to claim 1.   The encoder scale according to claim 2, wherein the first spiral pattern and the second spiral pattern are wound in the same direction.   The encoder scale according to claim 2, wherein the first spiral pattern and the second spiral pattern are wound in opposite directions.   The first pitch of the first spiral pattern is the same as the third pitch of the second spiral pattern, and the phase of the first pitch and the phase of the third pitch are 1. The encoder scale according to any one of claims 2 to 4, which is shifted by / 4 period.   The second pitch of the first spiral pattern is the same as the fourth pitch of the second spiral pattern, and the phase of the second pitch and the phase of the fourth pitch are 1. The encoder scale according to any one of claims 2 to 5, which is shifted by / 4 period.   The encoder scale according to any one of claims 2 to 4, wherein the first pitch of the first spiral pattern is different from the third pitch of the second spiral pattern. An encoder scale,
A light detection unit for detecting light via the encoder scale,
An encoder in which the encoder scale according to any one of claims 1 to 7 is used as the encoder scale.   9. The light detection unit according to claim 8, wherein a plurality of light receiving elements are arranged in each of a radial direction and a rotation direction around the rotation axis corresponding to the first spiral pattern of the encoder scale. Encoder.   The encoder according to claim 9, further comprising a switching element that switches between an output signal from the light receiving elements arranged in the radial direction and an output signal from the light receiving elements arranged in the rotational direction. The photodetection unit detects a first phase signal related to the radial direction and a second phase signal related to the rotational direction;
11. The processing unit according to claim 8, further comprising: a processing unit that calculates an absolute position within one rotation of the encoder scale based on the first phase signal and the second phase signal. Encoder. The encoder scale includes a second spiral pattern different from the first spiral pattern,
The light detection unit further includes a plurality of light receiving elements arranged in each of a radial direction and a rotation direction around the rotation axis corresponding to the second spiral pattern, and the light detection unit relates to the first spiral pattern A first radial phase signal and a third radial phase signal related to the second spiral pattern are detected, and a first phase signal is detected based on the first phase signal and the third phase signal. The encoder according to any one of claims 8 to 10, further comprising a first correction unit that generates a correction phase signal.   The encoder according to claim 12, wherein the first correction unit generates a correction phase signal based on a differential result between the first phase signal and the third phase signal. The encoder scale includes a second spiral pattern different from the first spiral pattern,
The light detection unit further includes a plurality of light receiving elements arranged in each of a radial direction and a rotation direction around the rotation axis corresponding to the second spiral pattern, and the light detection unit relates to the first spiral pattern A first phase signal in the radial direction and a third phase signal in the radial direction related to the second spiral pattern are detected, and based on the addition result of the first phase signal and the third phase signal 11. The apparatus according to claim 8, further comprising: a second correction unit that calculates an eccentric amount between a rotation axis of the encoder scale and a center of the first spiral pattern or the second spiral pattern. The encoder according to item.   The second correction unit corrects the second phase signal in the rotation direction related to the first spiral pattern or the fourth phase signal in the rotation direction related to the second spiral pattern based on the amount of eccentricity. The encoder according to claim 14. An illumination unit that illuminates the encoder scale;
The said illumination part has a 2 or more light emission part at predetermined intervals in at least one of the radial direction of the said 1st spiral pattern, and a rotation direction, The any one of Claims 8-15 characterized by the above-mentioned. The encoder according to item 1.   The encoder according to claim 16, wherein the illumination unit includes a modulation unit that modulates the intensity of each of the light emitting units with a predetermined period. A moving member;
A drive unit for moving the moving member;
An encoder fixed to the moving member and detecting position information of the moving member;
A drive device in which the encoder according to any one of claims 8 to 17 is used as the encoder. A moving object;
A drive device for moving the moving object;
A stage device in which the drive device according to claim 18 is used as the drive device.

Images