Encoder device

Abstract

In encoder devices, there is a need to improve the accuracy of position or angle detection. [Solution] The device comprises a scale with a periodic pattern, a light-emitting unit that irradiates the scale with light, a light-receiving unit that receives the light reflected by the scale with multiple pixels, a storage unit that stores the output from the light-receiving unit relating to at least a part of the scale as a reference, and a detection unit that detects the amount of scale movement by comparing the reference and the output from the light-receiving unit.

Description

Technical Field

[0001] The present invention relates to an encoder device.

Background Art

[0002] An encoder device is used to detect the position or angle of a movable member (for example, Patent Documents 1-4). Encoder devices include incremental encoders that detect relative positions or angles and absolute encoders that detect absolute positions or angles. In an encoder device, it is required to improve the detection accuracy of position or angle.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Patent Document 2

Patent Document 3

Patent Document 4

Summary of the Invention

[0004] One aspect of the present invention is an encoder device including a scale provided with a periodic pattern, a light emitting unit that irradiates light onto the scale, a light receiving unit that receives the light reflected by the scale with a plurality of pixels, a storage unit that stores based on the output from the light receiving unit regarding at least a part of the scale as a reference, and a detection unit that detects the movement amount of the scale by comparing the reference and the output from the light receiving unit.

[0005] One aspect of the present invention provides a scale having a first periodic pattern and a second periodic pattern having a period different from the period of the first periodic pattern and arranged in parallel with the first periodic pattern; a light-emitting unit that irradiates light onto the scale; a first light-receiving unit whose relative position to the scale changes as a moving unit moves and which receives light irradiated from the light-emitting unit onto the scale and reflected by the first periodic pattern; a second light-receiving unit that receives light irradiated from the light-emitting unit onto the scale and reflected by the second periodic pattern; and a unit that receives light reflected by the first periodic pattern. The encoder device comprises: a first A / D converter that converts the output from the first light receiving unit into a first digital output; a second A / D converter that converts the output from the second light receiving unit, which receives light reflected by the second periodic pattern, into a second digital output; and an absolute position detection unit that detects the absolute position of the moving part based on the phase difference between the first digital output, which is obtained by converting the output from the first light receiving unit, which receives light reflected by the first periodic pattern, and the second digital output, which is obtained by converting the output from the second light receiving unit, which receives light reflected by the second periodic pattern.

[0006] One aspect of the present invention is an encoder device comprising a scale having a periodic pattern, a light-emitting unit that irradiates light onto the scale, and a light-receiving unit whose relative position to the scale changes as a moving unit moves, and which receives light irradiated from the light-emitting unit onto the scale and reflected by the scale using a plurality of pixels, wherein dead zones, which are regions where no pixels are arranged, are provided between the plurality of pixels, and the reflective and non-reflective parts constituting the periodic pattern, and the plurality of pixels are arranged such that, in the process of the relative position between the scale and the light-receiving unit changing, if the reflected image at the boundary between the reflective and non-reflective parts has a portion that overlaps with the dead zone, the boundary has a portion that overlaps with at least one of the plurality of pixels. [Brief explanation of the drawing]

[0007] [Figure 1] This figure shows an example of the configuration of the encoder device 1 according to the first embodiment. [Figure 2] This figure shows an example of the scale 20 according to the first embodiment. [Figure 3] This figure shows an example of the configuration of a chip constituting the encoder device 1 according to the first embodiment. [Figure 4] This figure shows an example of the functional configuration of the signal processing unit 6 according to the first embodiment. [Figure 5] This figure shows an example of the operation flow of the encoder device 1 according to the first embodiment. [Figure 6] This figure shows an example of imaging a periodic pattern using multiple pixels according to the first embodiment. [Figure 7] This figure shows an example of a reference waveform and a detected phase waveform according to the first embodiment. [Figure 8] This figure shows an example of the range of the periodic pattern detected by the first linear sensor 100 in the incremental scale 21 according to the first embodiment. [Figure 9] This figure shows an example of scale 20a according to the second embodiment. [Figure 10] This figure shows an example of a pulse output when the first incremental scale 21a and the second incremental scale 23a are read according to the second embodiment. [Figure 11] This figure shows an example of the configuration of a chip constituting the encoder device 1a according to the second embodiment. [Figure 12] This figure shows an example of the functional configuration of the signal processing unit 6a according to the second embodiment of this embodiment. [Figure 13] This figure shows an example of reading a scale, similar to that used in conventional encoder devices, using the first linear sensor 100 provided in the encoder device 1 or encoder device 1a according to the second embodiment. [Figure 14] This figure shows an example of a graph illustrating how the output from each pixel changes in accordance with the movement of a periodic pattern related to the conventional technology. [Figure 15]When there is no dead zone provided between a plurality of pixels according to the related art, it shows how the output from each pixel changes in response to the movement of the periodic pattern. [Figure 16] It is a figure which shows an example of the shape and arrangement | positioning of the multiple pixels which concern on a 3rd Embodiment. [Figure 17] It is a figure which shows an example of the shape of the reflection area | region 75c which concerns on the modification of a 3rd Embodiment. [Figure 18] It is a figure which shows an example of the shape and arrangement | positioning of the multiple pixels which concern on the modification of a 3rd Embodiment. [Figure 19] It is a figure which shows an example of the shape and arrangement | positioning of the multiple pixels which concern on the modification of a 3rd Embodiment.

MODE FOR CARRYING OUT THE INVENTION

[0008] (First Embodiment) Hereinafter, the first embodiment will be described in detail with reference to the drawings. FIG. 1 is a diagram showing an example of the configuration of an encoder device 1 according to the present embodiment. The encoder device 1 includes a disk 2, a light emitting unit 3, a light receiving unit 4, and a signal processing chip 5. The encoder device 1 is, for example, a rotary encoder. In FIG. 1, a cross section in a direction perpendicular to the circumferential direction of the disk 2 of the encoder device 1 is shown.

[0009] A rotating shaft (not shown) is provided on the disk 2. The disk 2 rotates as the rotating shaft rotates. A scale 20 is provided on the disk 2. The scale 20 is a pattern composed of a reflection part that reflects light and a non - reflection part that absorbs light. As shown in FIG. 2, the scale 20 includes an incremental scale 21 and an absolute scale 22. As an example, the incremental scale 21 is provided on the outer peripheral side of the disk 2 rather than the absolute scale 22.

[0010] The incremental scale 21 is provided with a pattern for detecting the relative angle of rotation of the disk 2. In the incremental scale 21, the reflecting portions and the non-reflecting portions are alternately arranged at equal intervals along the circumferential direction of the disk 2. A pattern in which the reflecting portions and the non-reflecting portions are alternately arranged at equal intervals is also described as a stripe pattern. The incremental scale 21 is a periodic pattern with a pattern composed of the reflecting portions and the non-reflecting portions as a unit. Therefore, the scale 20 is provided with a periodic pattern.

[0011] The absolute scale 22 is an angle-specific pattern for detecting the absolute angle of rotation of the disk 2. The pattern is a linear gray code.

[0012] The light emitting unit 3 irradiates light to the scale 20 provided on the disk 2. As an example, the light emitting unit 3 includes a light emitting diode (LED) as a light source. In the example shown in FIG. 1, a part of the irradiation light irradiated from the light emitting unit 3 to the scale 20 is reflected by the reflecting portions 210 and 212, and the remaining part is absorbed by the non-reflecting portion 211.

[0013] The light receiving unit 4 includes a plurality of pixels. The light receiving unit 4 receives the light irradiated from the light emitting unit 3 to the scale 20 and reflected by the scale 20 by the plurality of pixels. Here, the relative position between the light receiving unit 4 and the scale 20 changes due to the rotation of the rotation axis provided on the disk 2. As an example, the light receiving unit 4 is a line sensor camera. That is, in the light receiving unit 4, the plurality of pixels are arranged in a row. Also, in the light receiving unit 4, each of the plurality of pixels is, for example, composed of a CMOS (Complementary Metal Oxide Semiconductor). That is, the light receiving unit 4, as an example, includes a CMOS image sensor.

[0014] The encoder device 1 is a reflective optical encoder. In the encoder device 1, the bottom surface of the LED provided in the light-emitting unit 3 and the surface of the light-receiving unit 4 are on the same plane. Therefore, the encoder device 1 is thinner compared to a transmissive optical encoder. In the encoder device 1, for example, the distance between the scale 20 and the light-receiving unit 4 is about 4 mm to 8 mm. Therefore, in the encoder device 1, the light reflected by the scale 20 is received by the light-receiving unit 4 before it diverges significantly. As a result, the encoder device 1 acquires an image of the scale 20 with no change in magnification at all times, without the need for a lens.

[0015] The signal processing chip 5 is an ASIC (Application Specific Integrated Circuit) chip that performs signal processing.

[0016] Referring now to Figure 3, the configuration of the chips constituting the encoder device 1 will be described. Figure 3 is a diagram showing an example of the configuration of the chips constituting the encoder device 1 according to this embodiment. The encoder device 1 comprises a signal processing chip 5, a first sensor chip 10, and a second sensor chip 11. The first sensor chip 10 is provided with a first linear sensor 100 and a first A / D converter 101. The second sensor chip 11 is provided with a second linear sensor 110 and a second A / D converter 111.

[0017] The first linear sensor 100 is a line sensor camera for reading the incremental scale 21. The first linear sensor 100 receives light that is illuminated from the LED 12 onto the incremental scale 21 and reflected by the incremental scale 21. The first A / D converter 101 converts the output from the first linear sensor 100 into a digital output.

[0018] The second linear sensor 110 is a line sensor camera for reading the absolute scale 22. The second linear sensor 110 receives light that is illuminated from the LED 12 onto the absolute scale 22 and reflected by the absolute scale 22. The second A / D converter 111 converts the output from the second linear sensor 110 into a digital output.

[0019] The first linear sensor 100 and the second linear sensor 110 are, for example, linear sensors of the same type. The linear sensor has a mode for reading the incremental scale 21 and a mode for reading the absolute scale 22. The first linear sensor 100 is the linear sensor switched to the mode for reading the incremental scale 21. The second linear sensor 110 is the linear sensor switched to the mode for reading the absolute scale 22. Furthermore, a different type of linear sensor than the first linear sensor 100 may be used as the second linear sensor 110 to read the Gray code.

[0020] As described above, the signal processing chip 5 is an ASIC chip. The signal processing chip 5 detects the relative angle of rotation of the disk 2 based on the output from the first linear sensor 100, which has been converted to a digital output by the first A / D converter 101. The signal processing chip 5 also detects the absolute angle of rotation of the disk 2 based on the output from the second linear sensor 110, which has been converted to a digital output by the second A / D converter 111. The first linear sensor 100 and the second linear sensor 110 are included in the light receiving unit 4 (Figure 1). The LED 12 is included in the light emitting unit 3 (Figure 1).

[0021] Referring now to Figure 4, the signal processing unit 6, which is implemented by the signal processing chip 5, will be described. Figure 4 is a diagram showing an example of the functional configuration of the signal processing unit 6 according to this embodiment. The signal processing unit 6 includes a phase detection unit 60, a counting unit 61, a relative position detection unit 62, an absolute position detection unit 63, a reference waveform creation unit 64, an operation switching unit 65, and a storage unit 66. These functional units are implemented as an ASIC.

[0022] The phase detection unit 60 detects the phase of the incremental scale 21. This phase is the phase of one period of the incremental scale 21. The phase detection unit 60 detects the phase by comparing the phase difference between a reference phase waveform pre-stored in the memory unit 66 and a phase waveform obtained when the output from the first linear sensor 100 included in the light receiving unit 4 is converted to a digital output by the first A / D converter 101. Hereafter, the reference phase waveform stored in the memory unit 66 will also be referred to as the reference waveform. The phase waveform obtained when the output from the first linear sensor 100 included in the light receiving unit 4 is converted to a digital output will also be referred to as the detected phase waveform.

[0023] The counting unit 61 counts the number of periods of a periodic pattern based on the phase of the periodic pattern detected by the phase detection unit 60.

[0024] The relative position detection unit 62 detects the amount of relative rotation of the disk 2 from an arbitrary reference position. Here, the relative position detection unit 62 detects the amount of relative rotation in units of one period of the period pattern based on the number of periods counted by the counting unit 61 and the phase detected by the phase detection unit 60.

[0025] The absolute position detection unit 63 detects the absolute angle of rotation of the disk 2. The absolute position detection unit 63 detects the absolute angle by reading the Gray code obtained when the output from the second linear sensor 110 included in the light receiving unit 4 is converted to a digital output by the second A / D converter 111.

[0026] The reference waveform creation unit 64 creates a reference waveform. The reference waveform creation unit 64 creates a reference waveform for each rotation angle of the disk 2, which is based on the pixels provided in the light receiving unit 4. The reference waveform creation unit 64 creates the reference waveform during the period from when the encoder device 1 is manufactured in the factory until it is actually put into use. The reference waveform creation unit 64 stores the created reference waveform as reference waveform information 660 in the storage unit 66.

[0027] The operation switching unit 65 switches the operation of the signal processing chip 5. The operation switching unit 65 switches the operation of the signal processing chip 5 between a mode for creating a reference phase waveform (referred to as the reference waveform creation mode) and a mode for detecting the rotation angle of the disk 2 (referred to as the detection mode). In the reference waveform creation mode, the reference waveform creation unit 64 operates. In the detection mode, the phase detection unit 60, the counting unit 61, the relative position detection unit 62, and the absolute position detection unit 63 operate.

[0028] The memory unit 66 stores reference waveform information 660. In other words, the memory unit 66 pre-stores reference phase waveforms for each phase of the incremental scale 21, which is measured in pixels. These phases represent the phases in one period. The memory unit 66 is implemented as a memory mounted on the ASIC. In other words, the memory unit 66 is a memory provided in the encoder device 1.

[0029] Next, the operation flow of the encoder device 1 in the reference waveform creation mode and the detection mode will be described. Figure 5 is a diagram showing an example of the operation flow of the encoder device 1 according to this embodiment.

[0030] The reference waveform creation mode is performed, for example, before the encoder device 1 is manufactured and shipped from the factory. Therefore, by the time the reference waveform creation mode is performed, the assembly of the components constituting the encoder device 1 is complete. This assembly determines the positional relationship between the disc 2 and the light receiving unit 4 (first linear sensor 100).

[0031] Step S10: The reference waveform creation unit 64 acquires a reference waveform. When acquiring the reference waveform, the incremental scale 21 is positioned at an arbitrary location where one or more periods can be acquired. Light emitted from the light-emitting unit 3 onto the periodic pattern included in the incremental scale 21 and reflected by the periodic pattern is received by multiple pixels provided in the first linear sensor 100. In other words, the periodic pattern is imaged by multiple pixels provided in the first linear sensor 100. Here, the periodic pattern included in the incremental scale 21 is imaged for a length of one or more periods.

[0032] The first A / D converter 101 converts the output from the first linear sensor 100 into a digital output. The reference waveform creation unit 64 acquires the converted digital output as a reference waveform. This digital output corresponds to the readings captured by the multiple pixels provided in the first linear sensor 100. Therefore, the reference waveform is a waveform represented as a pair of the numbers of the multiple pixels provided in the first linear sensor 100 and the readings captured by those multiple pixels.

[0033] Step S20: The reference waveform creation unit 64 performs preprocessing on the acquired reference waveform, including filtering, smoothing, and DC removal. The filtering and smoothing processes shape the phase waveform. In addition, the smoothing and DC removal processes remove noise from the phase waveform.

[0034] Step S30: The reference waveform creation unit 64 creates reference waveform information 660 that shows the pre-processed reference waveform.

[0035] Step S40: The reference waveform creation unit 64 stores the created reference waveform information 660 in the storage unit 66. Therefore, it is stored in the memory provided in the encoder device 1 before the encoder device 1 is shipped. With this, the encoder device 1 terminates its operation in the reference waveform creation mode.

[0036] Next, the operation of the detection mode will be described. For example, the operation of the detection mode is repeated at a predetermined interval when the encoder device 1 is in use. The predetermined interval is the sampling period of the first A / D converter 101.

[0037] Step S110: The phase detection unit 60 acquires the detected phase waveform. Here, the LED 12 emits light every 1 microsecond. The first linear sensor 100 receives the light that is illuminated from the LED 12 onto the incremental scale 21 and reflected by the incremental scale 21. The phase detection unit 60 acquires the detected phase waveform obtained by converting the output from the first linear sensor 100 to a digital output by the first A / D converter 101. The first A / D converter 101 converts the output from the first linear sensor 100 to a digital output at a predetermined sampling period. The light source may be kept lit, and the sensor reading period may be set to every 1 microsecond.

[0038] Referring to Figure 6, we will now explain how the light reflected by the incremental scale 21 is received (imaged) by multiple pixels provided on the first linear sensor 100. Figure 6 is a diagram showing an example of imaging of a periodic pattern by multiple pixels according to this embodiment. The pixel row 30 is a plurality of pixels arranged in a single row on the first linear sensor 100.

[0039] The first reflection region 72 and the second reflection region 74 are reflected images (bright areas) formed at the positions of pixel rows 30 when light emitted from the LED 12 is reflected by the reflective portion of the incremental scale 21. The first absorption region 71 and the second absorption region 73 are shadows (dark areas) formed at the positions of pixel rows 30 when light emitted from the LED 12 is absorbed by the absorbing portion of the incremental scale 21.

[0040] Here, the width of a pixel row 30 in the direction of the row (the direction in which the disk 2 rotates) is, for example, 10 micrometers. The number of pixels in the pixel row 30 is such that the length of the pixel row 30 is approximately one or two units of the periodic pattern of the incremental scale 21. In the example shown in Figure 6, the pixel row 30 consists of approximately 30 pixels. The length of the pixel row 30 is about two pixels longer than the length of one and a half units of the periodic pattern.

[0041] For each light emission of the LED 12 per microsecond, the first linear sensor 100 simultaneously reads out all pixels included in the pixel array 30. The first linear sensor 100 ensures sufficient signal strength with a short exposure time, eliminating the need for a global shutter when the light source is blinking. The first linear sensor 100 detects the signal by voltage.

[0042] Returning to Figure 5, we continue the explanation of the operation in detection mode. Step S120: The phase detection unit 60 performs preprocessing on the acquired detected phase waveform, including filtering, smoothing, and DC removal.

[0043] Step S130: The phase detection unit 60 calculates the positional correlation (phase) between the reference waveform and the detected phase waveform. The detected phase waveform is the pre-processed detected phase waveform. The phase detection unit 60 reads the reference waveform information 660 from the storage unit 66. The phase detection unit 60 calculates the positional correlation between the reference waveform indicated by the read reference waveform information 660 and the detected phase waveform.

[0044] The operation for calculating position correlation will now be explained with reference to Figures 7 and 8. Figure 7 is a diagram showing an example of a reference waveform and a detected phase waveform according to this embodiment. In Figure 7, the reference waveform G0 and the detected phase waveform G1 are shown as plots indicating the digital output values ​​from the first A / D converter 101 for each pixel number.

[0045] Figure 8 shows the range of the periodic pattern detected by the first linear sensor 100 in the incremental scale 21. The reference waveform G0 is a phase waveform obtained by detecting the range indicated by line L0 within the periodic pattern. The range indicated by line L0 is the range detected in order to acquire the reference waveform in the reference waveform creation mode. As described above, the acquired reference waveform is stored in the storage unit 66 as reference waveform information 660.

[0046] On the other hand, the detected phase waveform G1 is a phase waveform obtained by detecting the range indicated by line L1 within the periodic pattern. The range indicated by line L1 is the range detected in order to acquire the detected phase waveform in detection mode. The range indicated by line L1 changes each time detection (reading) is performed because the disk 2 rotates.

[0047] The phase detection unit 60 detects the phase of the periodic pattern in which the phase of the phase waveform obtained by converting the output from the first linear sensor 100 to a digital output by the first A / D converter 101 is minimized, based on the reference waveform for each phase of the periodic pattern in which the pixels of the first linear sensor 100 are stored in the memory unit 66.

[0048] As described above, the reference waveform is acquired after the assembly of the components constituting the encoder device 1 is completed and stored in the storage unit 66 in advance. Errors in the arrangement may occur during the assembly of the components. For example, the length direction of the pixel array 30 provided in the first linear sensor 100 may be oblique to the direction of the periodic pattern of the incremental scale 21. Also, errors in the diameter of the incremental scale 21 may cause the optical pitch of the periodic pattern to deviate from the design value.

[0049] Even if there is an error in the placement of a component during assembly, the reference waveform is acquired and stored in the storage unit 66, affected by the error in the placement of that component. The error in the placement of that component remains even when acquiring the detected phase waveform. Therefore, when calculating the positional correlation between the reference waveform and the detected phase waveform, the error in the placement of that component is canceled out. In other words, the calculation result of the positional correlation is not affected by the error in the placement of that component.

[0050] The encoder device 1 can reduce the required precision of component placement during manufacturing. In other words, with the encoder device 1, precise positioning (calibration) of the components is unnecessary after the initial assembly.

[0051] In the encoder device 1, for example, even if the length direction of the pixel array 30 provided in the first linear sensor 100 is oblique to the direction of the periodic pattern of the incremental scale 21, the calculation result of the position correlation is not affected, so the required precision for the arrangement of the pixel array 30 provided in the first linear sensor 100 can be reduced. Also, in the encoder device 1, for example, even if the optical pitch of the periodic pattern deviates from the design value due to an error in the diameter of the incremental scale 21, the calculation result of the position correlation is not affected, so the requirements for the diameter of the incremental scale 21 are relaxed.

[0052] Furthermore, in encoder device 1, the calculation for calculating the position correlation is performed using only subtraction and addition, making the calculation simple. Therefore, encoder device 1 can perform calculations faster than when the calculation for calculating the position correlation includes operations other than subtraction and addition.

[0053] However, the phase of the incremental scale 21 may generally correspond to the phase between pixels. Therefore, the phase detection unit 60 performs the operation described below.

[0054] Step S140: The phase detection unit 60 outputs the detected phase. The phase detection unit 60 outputs the phase to, for example, the motor control unit (not shown in Figure 1) that controls the rotation of the disk 2. With this, the encoder device 1 terminates its operation in detection mode.

[0055] As described above, the detection mode operation is repeated at a predetermined period when the encoder device 1 is in use. The predetermined period is the sampling period of the first A / D converter 101. Therefore, the phase output from the encoder device 1 is discrete with respect to time. The sampling period of the first A / D converter 101 is, for example, 1 megaframe per second.

[0056] In calculating positional correlation, the error is smaller when the change in the digital output value relative to the pixel number is large for both the reference waveform and the detected phase waveform. Therefore, it is preferable that the reflected image of the periodic pattern shown in Figure 6 is fine. A fine reflected image means that the contrast of the contour of the reflected image is high. To increase the contrast of the contour of the reflected image, it is preferable that the size of the light source (LED 12) provided in the light-emitting unit 3 is small (close to a point light source). For example, the diameter of LED12 is 180 micrometers. For example, the wavelength of the emitted light is 850 nanometers, and the directional angle is 30 degrees.

[0057] Furthermore, the larger the number of points that make up both the reference waveform and the detected phase waveform, the smaller the error in position correlation. For this reason, it is preferable that the pixels provided on the first linear sensor 100 be small in size and numerous. The size of the pixels is preferably, for example, 10 micrometers or less.

[0058] Furthermore, a larger number of pixels in the first linear sensor 100 reduces the impact on phase calculation even if some of the pixels in the first linear sensor 100 are missing. In other words, a larger number of pixels in the first linear sensor 100 results in greater robustness of phase detection results against pixel loss.

[0059] In this embodiment, an example has been described in which the incremental scale 21 has a stripe pattern as its periodic pattern, but it is not limited to this. The incremental scale 21 may have, for example, a pattern in which reflective and non-reflective parts are randomly arranged as its periodic pattern. In other words, in that case, the incremental scale 21 will repeatedly have a pattern in which reflective and non-reflective parts are randomly arranged. Even when the periodic pattern is a pattern in which reflective and non-reflective parts are randomly arranged, the calculation for calculating the position correlation between the reference waveform and the detected phase waveform described above is the same. It is believed that randomly arranged patterns, compared to stripe patterns, offer improved phase detection accuracy.

[0060] An example has been described in which the first linear sensor 100 is a line sensor camera, that is, in which multiple pixels are arranged in a single row in the first linear sensor 100, but it is not limited to this. The first linear sensor 100 may also be an area sensor camera. In other words, multiple pixels may be arranged in two or more rows in the first linear sensor 100. Even in that case, in order to capture one or more periodic patterns, the multiple pixels are arranged in two or more rows without changing the number of pixels in each row from the case where they are arranged in one row. However, in order to shorten the time required for calculating the position correlation, it is preferable that multiple pixels in the first linear sensor 100 be arranged in a single row. Furthermore, instead of a CMOS image sensor, a CCD (Charge-Coupled Device) image sensor may be used as the first linear sensor 100.

[0061] As described above, the encoder device 1 according to this embodiment includes a scale 20, a light-emitting unit 3, a light-receiving unit 4, an A / D converter (a first A / D converter 101 in this embodiment), a storage unit 66, and a phase detection unit 60. The scale 20 is provided with a periodic pattern (incremental scale 21 in this embodiment). The light-emitting unit 3 illuminates the scale 20 with light. The light-receiving unit 4 changes its relative position to the scale 20 as the moving part moves (in this embodiment, the rotation of the disc 2), and receives the light that is irradiated from the light-emitting unit 3 onto the scale 20 and reflected by the scale 20 with multiple pixels (in this embodiment, the pixel array 30 provided in the first linear sensor 100). The A / D converter (in this embodiment, the first A / D converter 101) converts the output from the light receiving unit 4 into a digital output. The memory unit 66 pre-stores reference phase waveforms (in this embodiment, phase shift data indicated by reference waveform information 660) for each phase of a periodic pattern (in this embodiment, an incremental scale 21) with the pixels of the pixel row 30 as the unit. The phase detection unit 60 detects the phase of the periodic pattern (incremental scale 21 in this embodiment) by comparing the phase difference between a reference phase waveform (data indicated by reference waveform information 660 in this embodiment) pre-stored in the memory unit 66 and a phase waveform (detected phase waveform in this embodiment) obtained when the output from the light receiving unit 4 is converted to a digital output by the A / D converter (first A / D converter 101 in this embodiment).

[0062] In conventional phase detection methods, one period (one pitch) of the periodic pattern was received by receiving light from multiple pixels on the sensor in sets of four pixels. This is because, based on the A-phase signal and B-phase signal from each of the two incremental scales, one period is divided into four regions according to the signs of the A-phase signal and B-phase signal, and the phase is read by referring to the approximate value of the arctangent function for each region. In conventional phase detection methods, since one period of the periodic pattern is received by sets of four pixels on the sensor, the size of the pixels on the sensor had to be determined according to the size of the reflected image of the periodic pattern of the incremental scale.

[0063] As described above, in the encoder device 1 according to this embodiment, the phase of the periodic pattern (incremental scale 21 in this embodiment) is detected by comparing the phase difference between a reference phase waveform (phase shift data indicated by reference waveform information 660 in this embodiment) pre-stored in the storage unit 66 and a phase waveform (detected phase waveform in this embodiment) obtained by converting the output from the light receiving unit 4 to a digital output by the A / D converter (first A / D converter 101 in this embodiment). Therefore, in the encoder device 1, the size of the pixels in the pixel array 30 provided in the light receiving unit 4 is not limited by the size of the reflected image of the periodic pattern (incremental scale 21 in this embodiment) provided in the scale 20. In the encoder device 1, by reducing the size of the pixels (for example, to 1 micrometer or less), it is possible to acquire a frequency component of the periodic pattern (incremental scale 21 in this embodiment) that is higher than half the frequency of the periodic pattern (Nyquist frequency). Therefore, the encoder device 1 can improve the accuracy of detecting the phase of the periodic pattern (incremental scale 21 in this embodiment).

[0064] Furthermore, as described above, in the encoder device 1, even if there is an error in the placement of the components during assembly, the phase detection result is not affected by the error in the placement of the components (for example, the orientation of the pixel row 30 relative to the periodic pattern, or at least one of the diameter of the periodic pattern on the disk 2). Therefore, in the encoder device 1, precise positioning (calibration) of the components is unnecessary after the components have been assembled.

[0065] (Second embodiment) A second embodiment of the present invention will be described in detail below with reference to the drawings. In this embodiment, we will describe the case in which the absolute angle of rotation of the disk 2 is detected using two types of incremental scales for detecting the relative position. Note that components identical to those in the first embodiment described above are denoted by the same reference numerals, and descriptions of identical components and operations may be omitted.

[0066] The encoder device according to this embodiment is referred to as encoder device 1a. Encoder device 1a comprises a disc 2a, a light-emitting unit 3, a light-receiving unit 4a, and a signal processing chip 5a. The light-receiving unit 4a is provided with at least two linear sensors for detecting relative angles. The disc 2a is provided with a scale 20a.

[0067] As shown in Figure 9, the scale 20a is provided with a first incremental scale 21a and a second incremental scale 23a. For example, the first incremental scale 21a and the second incremental scale 23a are provided in this order from the outer circumference to the inner circumference of the disk 2a. The second incremental scale 23a is arranged in parallel with the first incremental scale 21a.

[0068] The first incremental scale 21a and the second incremental scale 23a are provided with patterns for detecting the relative angle of rotation of the disk 2. Each of the first incremental scale 21a and the second incremental scale 23a has reflective and non-reflective portions arranged alternately at equal intervals along the circumferential direction of the disk 2a. The second incremental scale 23a has a period different from that of the first incremental scale 21a.

[0069] Figure 10 shows examples of pulses output when the first incremental scale 21a and the second incremental scale 23a are read, respectively. In Figure 10, for the sake of simplicity, the number of pulses, i.e., the number of periodic patterns contained in the first incremental scale 21a and the second incremental scale 23a, respectively, is shown to be fewer than the number of periodic patterns contained in the first incremental scale 21a and the second incremental scale 23a, respectively, as shown in Figure 9.

[0070] The first pulse P1 is the pulse output when the first incremental scale 21a is read. The second pulse P2 is the pulse output when the second incremental scale 23a is read. The number of pulses output when the disk 2a completes one rotation is one less for the second pulse P2 than for the first pulse P1. In other words, for one rotation of the disk 2a, the number of periodic patterns included in the second incremental scale 23a is one less than the number of periodic patterns included in the first incremental scale 21a.

[0071] Therefore, when the disk 2a rotates once, a phase difference of one period occurs between the first incremental scale 21a and the second incremental scale 23a. There is a one-to-one correspondence between the phase difference between the output of the first incremental scale 21a and the output of the second incremental scale 23a and the absolute angle of rotation of the disk 2a. The encoder device 1a calculates the phase difference between the output of the first incremental scale 21a and the output of the second incremental scale 23a and detects the absolute angle of rotation of the disk 2a from this phase difference.

[0072] Note that the number of periodic patterns included in the first incremental scale 21a and the number of periodic patterns included in the second incremental scale 23a do not need to be different, and the example shown in Figure 10 is not the only example.

[0073] On the other hand, the first incremental scale 21a and the second incremental scale 23a are also used to detect the relative angle of rotation of the disk 2. In the encoder device 1a, as an example, the average of the relative angle detected from the first incremental scale 21a and the relative angle detected from the second incremental scale 23a is used as the detection result for the relative angle (phase within one period of the periodic pattern). This improves resistance to dust and other contaminants adhering to pixels and dirt on pixels, and provides highly accurate calculation results compared to detecting the relative angle using only one of them (for example, the first incremental scale 21a).

[0074] Furthermore, only one of the first incremental scale 21a and the second incremental scale 23a may be used to detect the relative angle.

[0075] Here, the light-receiving unit 4a receives light that is irradiated from the light-emitting unit 3 onto the scale 20 and reflected by the first incremental scale 21a, and light that is irradiated from the light-emitting unit 3 onto the scale 20 and reflected by the second incremental scale 23a.

[0076] Figure 11 shows an example of the configuration of the chips constituting the encoder device 1a according to this embodiment. Comparing the chip configuration according to this embodiment (Figure 11) with the chip configuration according to the first embodiment (Figure 3), the third sensor chip 12a and the signal processing chip 5a are different. Here, the configuration of the other components (first sensor chip 10) is the same as in the first embodiment.

[0077] In this embodiment, the first linear sensor 100 is an image sensor for reading the first incremental scale 21a. The first A / D converter 101 converts the output from the first linear sensor 100 into a first digital output. In other words, the first A / D converter 101 converts the output from the light receiving unit 4a, which receives light reflected by the first incremental scale 21a, into a first digital output.

[0078] The third sensor chip 13a is equipped with a third linear sensor 130a and a third A / D converter 131a. The third linear sensor 130a is a line sensor camera for reading the second incremental scale 23a. The configuration of the third linear sensor 130a is the same as that of the first linear sensor 100. The third A / D converter 131a converts the output from the third linear sensor 130a into a second digital output. In other words, the third A / D converter 131a converts the output from the light receiving unit 4a, which receives light reflected by the second incremental scale 23a, into a second digital output.

[0079] The signal processing chip 5a is an ASIC chip. The signal processing chip 5a detects the absolute angle of rotation of the disk 2 based on the output from the first linear sensor 100, which has been converted to a first digital output by the first A / D converter 101, and the output from the third linear sensor 130a, which has been converted to a second digital output by the third A / D converter 131a. The signal processing chip 5a also detects the absolute angle of rotation of the disk 2 based on the output from the second linear sensor 110, which has been converted to a digital output by the second A / D converter 111.

[0080] Furthermore, the signal processing chip 5a detects the relative angle of rotation of the disk 2 based on the output from the first linear sensor 100, which has been converted to a first digital output by the first A / D converter 101, and the output from the third linear sensor 130a, which has been converted to a second digital output by the third A / D converter 131a.

[0081] Referring now to Figure 12, the signal processing unit 6a, which is a function realized by the signal processing chip 5a, will be described. Figure 12 is a diagram showing an example of the functional configuration of the signal processing unit 6a according to this embodiment. The signal processing unit 6a includes a phase detection unit 60a, a counting unit 61, a relative position detection unit 62, an absolute position detection unit 63a, a reference waveform creation unit 64, an operation switching unit 65, and a storage unit 66a. These functional units are realized as an ASIC.

[0082] Comparing the signal processing unit 6a (Figure 12) according to this embodiment with the signal processing unit 6 (Figure 4) according to the first embodiment, the phase detection unit 60a, the absolute position detection unit 63a, and the storage unit 66a are different. Here, the functions of the other components (counting unit 61, relative position detection unit 62, reference waveform creation unit 64, and operation switching unit 65) are the same as in the first embodiment.

[0083] The phase detection unit 60a detects the phase of the periodic pattern provided on the scale 20a. The phase detection unit 60a detects the average of the first digital output, which is converted from the output of the first linear sensor 100, and the second digital output, which is converted from the output of the third linear sensor 130a, as the phase of the periodic pattern provided on the scale 20a.

[0084] Similar to the first embodiment, the phase detection unit 60a detects the phase of the periodic pattern included in the first incremental scale 21a by comparing the phase difference between a reference phase waveform stored in the storage unit 66a and a phase waveform obtained when the output from the first linear sensor 100 included in the light receiving unit 4a is converted to a digital output by the first A / D converter 101. The phase detection unit 60a also detects the phase of the periodic pattern included in the second incremental scale 23a by comparing the phase difference between a reference phase waveform stored in the storage unit 66a and a phase waveform obtained when the output from the third linear sensor 130a included in the light receiving unit 4a is converted to a digital output by the third A / D converter 131a.

[0085] The absolute position detection unit 63a detects the absolute angle of the disk 2a based on the phase difference between the first digital output, which is converted from the output of the first linear sensor 100, and the second digital output, which is converted from the output of the third linear sensor 130a.

[0086] The reference waveform creation unit 64a creates a first reference waveform and a second reference waveform. The first reference waveform is a reference waveform created for the first incremental scale 21a. The second reference waveform is a reference waveform created for the second incremental scale 23a. The reference waveform creation unit 64a stores the created first reference waveform and second reference waveform as reference waveform information 660a in the storage unit 66a.

[0087] The storage unit 66a stores reference waveform information 660a. The reference waveform information 660a includes first phase shift data for the first reference waveform and second phase shift data for the second reference waveform. In other words, the storage unit 66a stores the reference phase waveform for each phase within one period of a periodic pattern with pixels as the unit, for both the first reference waveform and the second reference waveform.

[0088] Furthermore, in scale 20a, an absolute scale 22 may be provided along with the first incremental scale 21a and the second incremental scale 23a. In that case, the encoder device 1a detects both the absolute angle detected from the phase difference between the output of the first incremental scale 21a and the output of the second incremental scale 23a, and the absolute angle detected from the absolute scale 22. The encoder device 1a may improve the accuracy of absolute angle detection by, for example, using the average of these two absolute angles as the absolute angle detection result.

[0089] Furthermore, the absolute angle may be determined using only the absolute scale 22. In this case, the first incremental scale 21a and the second incremental scale 23a are used solely to detect the relative angle. That is, the average of the relative angle detected from the first incremental scale 21a and the relative angle detected from the second incremental scale 23a is used solely to detect the relative angle.

[0090] As described above, the encoder device 1a according to this embodiment includes a scale 20a, a light-emitting unit 3, a light-receiving unit 4a, a first A / D converter (first A / D converter 101 in this embodiment), a second A / D converter (third A / D converter 131a in this embodiment), and an absolute position detection unit 63a. The scale 20a is provided with a first periodic pattern (the first incremental scale 21a in this embodiment) and a second periodic pattern (the second incremental scale 23a in this embodiment) which has a different period from the first periodic pattern (the first incremental scale 21a in this embodiment) and is arranged in parallel with the first periodic pattern (the first incremental scale 21a in this embodiment). The light-emitting unit 3 irradiates light onto the scale 20a. The light-receiving unit 4a changes its relative position to the scale 20a due to the movement of the moving part (in this embodiment, the rotation of the disc 2a), and receives light that is irradiated from the light-emitting unit 3 onto the scale 20a and reflected by the first periodic pattern (in this embodiment, the first incremental scale 21a), and light that is irradiated from the light-emitting unit 3 onto the scale 20a and reflected by the second periodic pattern (in this embodiment, the second incremental scale 23a). The first A / D converter (in this embodiment, the first A / D converter 101) converts the output from the light receiving unit 4a, which receives light reflected by the first periodic pattern (in this embodiment, the first incremental scale 21a), into a first digital output. The second A / D converter (in this embodiment, the third A / D converter 131a) converts the output from the light receiving unit 4a, which receives light reflected by the second periodic pattern (in this embodiment, the second incremental scale 23a), into a second digital output. The absolute position detection unit 63a detects the absolute position of the moving part (in this embodiment, the absolute angle of rotation of the disk 2a) based on the phase difference between a first digital output converted from the output of the light receiving unit 4a that receives light reflected by the first periodic pattern (in this embodiment, the first incremental scale 21a), and a second digital output converted from the output of the light receiving unit 4a that receives light reflected by the second periodic pattern (in this embodiment, the second incremental scale 23a).

[0091] With this configuration, the encoder device 1a according to this embodiment can use the same periodic pattern for detecting relative position (i.e., relative phase) to detect the absolute position of the moving part (in this embodiment, the absolute angle of rotation of the disk 2a), and can use the same configuration of the light-receiving unit (i.e., the sensor configuration) as the light-receiving unit for detecting relative position (i.e., relative phase). Similar to the encoder device 1 according to the first embodiment, the encoder device 1a can improve the accuracy of detecting the phase of the periodic pattern (in this embodiment, the first incremental scale 21a and the second incremental scale 23a) by reducing the size of the pixels (for example, to 1 micrometer or less). Therefore, when detecting the absolute position of the moving part (in this embodiment, the absolute angle of rotation of the disk 2a) based on the phase difference between two periodic patterns (in this embodiment, the first incremental scale 21a and the second incremental scale 23a), the encoder device 1a can improve the detection accuracy.

[0092] Now, referring to Figure 13, we will explain an example of reading a scale, similar to that used in conventional encoder devices, using the first linear sensor 100 provided in encoder device 1 or encoder device 1a. The conventional Scale 200 has an incremental scale (labeled "INC"), an absolute scale (labeled "ABS"), and multi-track patterns (labeled "(M1)", "M2", "(M3)", and "M4" respectively) arranged from the outer circumference to the inner circumference. The multi-track patterns are for detecting rotational speed.

[0093] To read the conventional scale 200, the radial order of the pattern arrangement of the conventional scale 200 is changed from the order shown in Figure 13. For example, the pattern arrangement of the conventional scale 200 is changed to pattern arrangement C1 and pattern arrangement C2. Pattern arrangements C1 and C2 are arranged in this order from the outer circumference to the inner circumference. In pattern arrangement C1, the patterns are arranged in the order of "(M1)", "M2", and "INC" from the outer circumference to the inner circumference. In pattern arrangement C2, the patterns are arranged in the order of "ABS", "M4", and "(M3)" from the outer circumference to the inner circumference. Here, in pattern arrangement C2, the patterns "ABS", "M4", and "(M3)" are arranged as patterns that are radially inverted by 180 degrees compared to the conventional scale 200.

[0094] Pattern arrangement C1 and pattern arrangement C2 are each read by two linear sensors (line sensor cameras) of the same type. Furthermore, since the radial width of each pattern is read by a line sensor camera with multiple pixels arranged in a single row, a shorter width is preferable.

[0095] (Third embodiment) A third embodiment of the present invention will be described in detail below with reference to the drawings. Note that components identical to those in the first embodiment described above will be denoted by the same reference numerals, and descriptions of identical components and operations may be omitted.

[0096] In the embodiment described above, a predetermined interval is provided between multiple pixels in the sensor (such as the first linear sensor 100) of the light-receiving unit 4. This predetermined interval is a dead zone where light cannot be received. The dead zone is necessary for the wiring of the sensor. As shown in Figure 14, a dead zone 40 is provided between pixel 31 and pixel 32. Figure 14 shows how the reflection region 75 moves as a movement of the periodic pattern. The reflection region 75 is a reflected image formed at the position of the pixel row when light emitted from the light-emitting unit 3 is reflected by the reflection region of the periodic pattern.

[0097] Figure 14 shows graphs illustrating how the output from each pixel changes in response to the movement of the periodic pattern. Graph A1 shows the output from pixel 31 for the position of the reflection region 75 in response to the movement of the periodic pattern. Graph A2 shows the output from pixel 32 for the position of the reflection region 75 in response to the movement of the periodic pattern. When the position of the boundary 750 of the reflection region 75 is included in the dead zone 40, there exists a range R1 in which neither the output from pixel 31 nor the output from pixel 32 changes. Therefore, the dead zone 40 obscures the position of the boundary of the reflection portion that constitutes the periodic pattern.

[0098] On the other hand, Figure 15 shows how the output from each pixel changes in response to the movement of the periodic pattern when no dead zone is provided between multiple pixels. There is no dead zone between pixel 34 and pixel 35. Graph B1 shows the output from pixel 34 with respect to the position of the reflection region 75 in response to the movement of the periodic pattern. Graph B2 shows the output from pixel 35 with respect to the position of the reflection region 75 in response to the movement of the periodic pattern. As shown in graphs B1 and B2, when no dead zone is provided, at least one of the output from pixel 34 and the output from pixel 35 changes in response to the movement of the boundary 750 of the reflection region 75.

[0099] However, as mentioned above, the dead zone is an area necessary for the wiring of the sensor. In this embodiment, the shape of the pixels, the arrangement of the pixels, or the shape of the reflective region, which is the reflected image of the reflective part, is changed from that of the embodiment described above so that the output from the pixels changes in accordance with the movement of the periodic pattern even if there is a dead zone.

[0100] The encoder device according to this embodiment is referred to as encoder device 1b. Encoder device 1b comprises a disk 2b, a light-emitting unit 3, a light-receiving unit 4b, and a signal processing chip 5. A scale 20b is provided on the disk 2b. The scale 20b includes an incremental scale 21b and an absolute scale 22. The incremental scale 21b has reflective and non-reflective sections arranged alternately at equal intervals along the circumferential direction of the disk 2. The incremental scale 21b has a periodic pattern consisting of a pattern of reflective and non-reflective sections as its unit. Therefore, the scale 20b is provided with a periodic pattern.

[0101] The light-receiving unit 4b is provided with a linear sensor 100b for detecting relative angles. The linear sensor 100b has multiple pixels arranged in a line. In the encoder device 1b, a dead zone is provided between multiple pixels, which is an area where no pixels are placed.

[0102] In the encoder device 1, the reflective and non-reflective portions that constitute the periodic pattern, as well as the plurality of pixels, are arranged such that, during the process in which the relative position between the scale 20b and the light-receiving portion 4b changes, if the reflected image at the boundary between the reflective and non-reflective portions has a portion that overlaps with a dead zone, the boundary has a portion that overlaps with at least one of the plurality of pixels.

[0103] Figure 16 is a diagram showing an example of the shape and arrangement of multiple pixels according to this embodiment. Pixels 31b and 32b are examples of multiple pixels provided on the linear sensor 100b. As shown in Figure 16, the shape of the multiple pixels provided on the linear sensor 100b is a parallelogram in which adjacent angles are not equal. A dead zone 40b is provided between pixels 31b and 32b. Depending on the shapes of pixels 31b and 32b, the shape of the dead zone 40b is a parallelogram in which adjacent angles are not equal.

[0104] The boundary 750 of the reflective region 75 has a portion that overlaps with the dead zone 40b. In this case, the boundary 750 has a portion that overlaps with at least one of the pixels 31b and 32b.

[0105] Figure 17 shows an example of the shape of the reflective region 75c according to a modified example of this embodiment. In this modified example, the shapes of the reflective and non-reflective portions constituting the periodic pattern are parallelograms with adjacent angles not equal to each other. The reflective region 75c is the reflected image of the reflective portion. The boundary 750c of the reflective region 75c has a portion that overlaps with the dead zone 40. In this case, the boundary 750c has a portion that overlaps with at least one of the pixels 31 and 32.

[0106] Figure 18 shows an example of the shape and arrangement of a plurality of pixels according to a modified example of this embodiment. Pixels 31d and 32d are examples of a plurality of pixels provided on the linear sensor 100b. As shown in Figure 18, the shape of the plurality of pixels provided on the linear sensor 100b is rectangular. The plurality of pixels provided on the linear sensor 100b are arranged at an angle with respect to the direction in which the relative position between the scale 20b and the plurality of pixels changes. A dead zone 40d is provided between pixel 31d and pixel 32d. Depending on the arrangement of pixels 31d and 32d, the dead zone 40d is arranged at an angle with respect to the direction in which the relative position between the scale 20b and the plurality of pixels changes.

[0107] The boundary 750 of the reflective region 75 has a portion that overlaps with the dead zone 40d. In this case, the boundary 750 has a portion that overlaps with at least one of the pixels 31d and 32d.

[0108] Figure 19 shows an example of the shape and arrangement of multiple pixels according to a modified example of this embodiment. Pixels 31e, 32e, 33e, and 34e are examples of multiple pixels provided on the linear sensor 100b. The multiple pixels provided on the linear sensor 100b are arranged in multiple adjacent rows. Pixels 31e and 33e form the same row. Pixels 32e and 34e form the same row. A dead zone 401e is provided between pixel 31e and pixel 33e. A dead zone 402e is provided between pixel 32e and pixel 34e.

[0109] The reflective and non-reflective portions constituting the periodic pattern of the scale 20b, and the plurality of pixels provided on the linear sensor 100b, are arranged such that, during the process in which the relative position between the scale 20b and the light-receiving portion 4b changes, if the boundary between the reflective portion and the non-reflective portion has a portion that overlaps with a dead zone included in one of the plurality of columns, the reflected image of the boundary has a portion that overlaps with at least one of the plurality of pixels included in the other of the plurality of columns. In the example shown in Figure 19, the boundary 750 of the reflective region 75 has a portion that overlaps with the dead zone 401e. In this case, the boundary 750 has a portion that overlaps with the pixel 32e.

[0110] In the example shown in Figure 19, for instance, the weighted average of the outputs from each of the three pixels is used as the output from the linear sensor 100b. For example, the weighted average of the outputs from pixels 31e, 32e, and 33e is used as the output from the linear sensor 100b.

[0111] As described above, the encoder device 1b according to this embodiment comprises a scale 20b, a light-emitting unit 3, and a light-receiving unit 4b. The scale 20b is provided with a periodic pattern (incremental scale 21b in this embodiment). The light-emitting unit 3 irradiates light onto the scale 20b. The light-receiving unit 4b changes its relative position to the scale 20b as the moving unit moves, and receives the light that is irradiated from the light-emitting unit 3 onto the scale 20b and reflected by the scale 20b using multiple pixels (in this embodiment, multiple pixels provided on the linear sensor 100b). Between multiple pixels (in this embodiment, multiple pixels provided on the linear sensor 100b), there are dead zones (in this embodiment, dead zones 40, 40b, 40d, or dead zones 401e and 402e) where no pixels are located. The reflective and non-reflective portions constituting the periodic pattern (in this embodiment, the incremental scale 21b), and the plurality of pixels (in this embodiment, the plurality of pixels provided on the linear sensor 100b) are arranged such that, during the process in which the relative position between the scale 20b and the light-receiving portion 4b changes, if the reflected image at the boundary between the reflective and non-reflective portions constituting the periodic pattern (in this embodiment, the incremental scale 21b) (in this embodiment, the boundary 750, or boundary 750c) has a portion that overlaps with a dead zone (in this embodiment, dead zone 40, dead zone 40b, dead zone 40d, or dead zones 401e and 402e), the boundary has a portion that overlaps with at least one of the plurality of pixels (in this embodiment, the plurality of pixels provided on the linear sensor 100b).

[0112] This configuration allows the encoder device 1b according to this embodiment to suppress the ambiguity of the boundary position of the reflective portion constituting the periodic pattern, even when a dead zone is provided between multiple pixels. Therefore, the encoder device 1b according to this embodiment can improve the accuracy of relative position detection by reading the periodic pattern.

[0113] In the encoder device 1a according to the second embodiment and the encoder device 1b according to the third embodiment described above, it is not essential to detect the phase of the periodic pattern by comparing a reference phase waveform with a detected phase waveform, as is the case with the encoder device 1 according to the first embodiment. In the encoder device 1a according to the second embodiment and the encoder device 1b according to the third embodiment, the phase may be detected based on a conventional phase detection method used in encoder devices.

[0114] In the embodiments described above, an example was given where the light source provided in the light-emitting unit 3 is an LED 12, but the invention is not limited to this. The light-emitting unit 3 may be equipped with light-emitting elements other than LEDs as its light source. As mentioned above, it is preferable that the light source provided in the light-emitting unit 3 is close to a point light source.

[0115] Furthermore, while the embodiments described above describe an example where the signal processing chips 5 and 5a are ASICs, the invention is not limited to this. The signal processing chips 5 and 5a may be composed of ICs (Integrated Circuits) other than ASICs. The signal processing chips 5 and 5a may be composed of FPGAs (Field-Programmable Gate Arrays), microcontrollers, CPUs (Central Processing Units), etc. However, as described above, the encoder devices 1, 1a, and 1b perform phase detection at a high speed of 1 megaframe per second. In order to support high-speed arithmetic processing, it is preferable that the signal processing chips 5 and 5a are ASICs.

[0116] Furthermore, while the embodiments described above have described an example where the encoder devices 1, 1a, and 1b are rotary encoders for detecting the rotation angle of a disc, the invention is not limited to this example. The encoder devices according to the embodiments described above may also be applied to linear encoders.

[0117] Although one embodiment of this invention has been described in detail above with reference to the drawings, the specific configuration is not limited to that described above, and various design changes can be made without departing from the spirit of this invention. [Explanation of symbols]

[0118] 1, 1a, 1b…Encoder device, 2, 2a, 2b…Disk, 3…Light-emitting unit, 4, 4a, 4b…Light-receiving unit, 5, 5a…Signal processing chip, 6, 6a…Signal processing unit, 10…First sensor chip, 11…Second sensor chip, 20, 20a, 20b…Scale, 21, 21b…Incremental scale, 21a…First incremental scale, 23a…Second incremental scale, 22…Absolute scale, 660, 660a…Reference waveform information, 60, 60a…Phase detection unit, 63, 63a…Absolute position Detection unit, 66, 66a... Storage unit, 100... First linear sensor, 100b... Linear sensor, 101... First A / D converter, 110... Second linear sensor, 111... Second A / D converter, 130a... Third linear sensor, 131a... Third A / D converter, 30... Pixel row, 31, 31b, 31d, 31e, 32, 32b, 32d, 32e, 33e, 34, 34e, 35... Pixel, 40, 40b, 40d, 401e, 402e... Dead zone, 210... Reflecting part, 211... Non-reflective part, 212... Reflecting part, 750, 750c... Boundary

Claims

1. A scale with a periodic pattern, A light-emitting unit that irradiates light onto the scale, A light-receiving unit that receives light reflected by the aforementioned scale using multiple pixels, A storage unit that stores, based on the output from the light receiving unit relating to at least a portion of the scale, By comparing the above standard with the output from the light receiving unit, A detection unit for detecting the amount of movement of the scale, Equipped with Encoder device.

2. The amount of movement of the scale is calculated by comparing a reference stored in the memory unit with the output of the light-receiving unit obtained as a result of the change in the relative position between the scale and the light-receiving unit. The encoder device according to claim 1.

3. In the light-receiving unit, the plurality of pixels are arranged in a single row, or in multiple rows with intervals between them. The encoder device according to claim 1 or claim 2.

4. The periodic pattern provided on the scale is a pattern in which reflective and non-reflective portions are arranged at a period of at least twice the size of the light-receiving portion. The encoder device according to any one of claims 1 to 3.

5. A dead zone, which is a region where no pixels are located, is provided between the aforementioned plurality of pixels. The reflective and non-reflective portions constituting the periodic pattern, as well as the plurality of pixels, are arranged such that, during the process in which the relative position between the scale and the light-receiving portion changes, if the reflected image at the boundary between the reflective portion and the non-reflective portion has a portion that overlaps with the dead zone, the boundary has a portion that overlaps with at least one of the plurality of pixels. The encoder device according to any one of claims 1 to 4.

6. A scale provided with a first periodic pattern and a second periodic pattern having a period different from the period of the first periodic pattern and arranged in parallel with the first periodic pattern, A light-emitting unit that irradiates light onto the scale, The relative position to the scale changes as the moving part moves, and the first light receiving unit receives light that is irradiated from the light emitting unit onto the scale and reflected by the first periodic pattern, and the second light receiving unit receives light that is irradiated from the light emitting unit onto the scale and reflected by the second periodic pattern, A first A / D converter that converts the output from the first light receiving unit, which receives light reflected by the first periodic pattern, into a first digital output, A second A / D converter that converts the output from the second light receiving unit, which receives light reflected by the second periodic pattern, into a second digital output, An absolute position detection unit detects the absolute position of the moving part based on the phase difference between a first digital output obtained by converting the output from the first light receiving unit that receives light reflected by the first periodic pattern, and a second digital output obtained by converting the output from the second light receiving unit that receives light reflected by the second periodic pattern. An encoder device equipped with the following features.

7. The method is characterized by calculating the amount of movement of the moving part by using the scale and averaging the first amount of movement of the moving part calculated from the first periodic pattern and the second amount of movement of the moving part calculated from the second periodic pattern. The encoder device according to claim 6.

8. A scale with a periodic pattern, A light-emitting unit that irradiates light onto the scale, The relative position of the movable part changes as the movable part moves, and the light receiving part receives the light that is irradiated from the light emitting part onto the scale and reflected by the scale using multiple pixels, Equipped with, A dead zone, which is a region where no pixels are located, is provided between the aforementioned plurality of pixels. The reflective and non-reflective portions constituting the periodic pattern, as well as the plurality of pixels, are arranged such that, during the process in which the relative position between the scale and the light-receiving portion changes, if the reflected image at the boundary between the reflective portion and the non-reflective portion has a portion that overlaps with the dead zone, the boundary has a portion that overlaps with at least one of the plurality of pixels. Encoder device.

9. The shape of the aforementioned plurality of pixels is a parallelogram in which adjacent angles are not equal. The encoder device according to claim 8.

10. The shapes of the reflective portion and the non-reflective portion are parallelograms in which adjacent angles are not equal. The encoder device according to claim 9.

11. The shape of the plurality of pixels is rectangular, The plurality of pixels are arranged at an angle with respect to the direction in which the relative position between the scale and the plurality of pixels changes. The encoder device according to claim 10.

12. The aforementioned plurality of pixels are arranged in multiple adjacent rows, The reflective portion and the non-reflective portion constituting the periodic pattern, as well as the plurality of pixels, are arranged such that, during the process in which the relative position between the scale and the light-receiving portion changes, if the boundary between the reflective portion and the non-reflective portion has a portion that overlaps with the dead zone included in one of the plurality of columns, the reflected image of the boundary has a portion that overlaps with at least one of the plurality of pixels included in the other of the plurality of columns. The encoder device according to claim 10.

Images