JP6035849B2 - Optical encoder - Google Patents

Description

  The present invention relates to an optical encoder that detects an absolute angle using an optical scale.

  The encoder is used in various mechanical devices to detect the position and angle of the movable element. In general, there are encoders that detect relative positions or angles and encoders that detect absolute positions or angles. There are optical and magnetic encoders, but the optical encoder is easily affected by foreign matter and the like, and is easily affected by fluctuations in the amount of detected light.

  In Patent Document 1, a polarizer having a uniform polarization direction is provided on the entire scale disk, and the transmitted light that has passed through the polarizer and has become linearly polarized light in the rotation direction of the polarizer is fixed. A technique for detecting with a polarizer is described.

  Patent Document 2 describes a technique of an optical encoder that can detect an absolute angle within one rotation without being affected by fluctuations in the amount of detected light due to foreign matter or the like. This technique is an optical scale disc that is rotatably supported and whose rotation angle is detected, and has an annular signal track, and the signal track is a circumferential direction of the optical scale disc. The polarizers formed in the respective regions divided in FIG. 3 and the adjacent polarizers have sequentially different polarization orientations in the rotation direction of the optical scale disk, and the polarization orientations are When the optical scale disk rotates once, it rotates m / 2 times (m is an integer of 0 or more).

Japanese Utility Model Publication No. 60-95516 JP 2009-168706 A

  In the technique described in Patent Document 1, since the polarization direction of the polarizer in the rotating scale disk is uniform, the output of the detected light increases or decreases twice for one rotation of the scale disk. Will repeat. For this reason, it is difficult to determine an absolute angle exceeding 180 °. In the technique disclosed in Patent Document 2, the signal track needs to be configured by a minute fan-shaped region obtained by dividing the circumference into N equal parts in the circumferential direction of the optical scale disk. For this reason, in the technique disclosed in Patent Document 2, there is a possibility of causing false detection or noise at adjacent boundaries.

  The present invention has been made in view of the above, and an object thereof is to provide an optical encoder that detects an absolute angle using an optical scale in which the polarization direction of a polarizer in a plane faces one direction. To do.

  In order to solve the above-described problems and achieve the object, an optical encoder includes a light source, an optical scale in which the polarization direction of a polarizer in a plane faces one direction, and the optical scale by a transmitted rotational force. A rotation / linear motion conversion mechanism that transmits a linear motion of the optical scale that is linked to the rotation, and incident light that is incident upon the light source light of the light source being transmitted or reflected on the optical scale is a first polarization. A first polarizing layer that separates in the direction, a first light-receiving unit with a polarizing layer that receives the first separated light separated by the first polarizing layer, and a second polarizing layer that separates the incident light in the second polarization direction And an angle sensor including a second light receiving unit with a polarizing layer that receives the second separated light separated by the second polarizing layer, and incident light that is incident upon the light source light of the light source being reflected on the optical scale. Includes three or more light intensity detectors to receive light From the position sensor and the light intensity detected by the light intensity receiver of the position sensor, the shortest position of the light source irradiated with the light source light of the light source is calculated, and the light intensity of the first separated light, The relative movement amount of the optical scale and the angle sensor is calculated from the light intensity of the second separated light, and the absolute angle of the optical scale is calculated based on the shortest position and the relative movement amount. And an arithmetic means for performing the processing.

  With the configuration described above, incident light incident on the angle sensor is polarized and separated into first separated light and second separated light. As a result, the computing means can calculate the optical scale by changing the polarization angle of the transmitted light or reflected light from the light intensity (signal intensity) of each polarization component separated into the first polarization direction and the second polarization direction. The amount of movement relative to the angle sensor can be calculated without being affected by the linear movement of the optical scale. The change in the polarization axis repeats the increase / decrease twice with respect to one rotation of the optical scale, but exceeds the 180 ° of the optical scale based on the shortest position where the light source light is irradiated on the optical scale. The rotated absolute angle can be specified. Further, the optical scale does not need to be finely divided into segments having different polarization directions. Since the optical scale has a uniform polarization axis, there is no boundary between regions having different polarization axes, and disturbance of the polarization state of reflected light or transmitted light due to this boundary can be suppressed. For this reason, the optical encoder can reduce the possibility of causing false detection or noise.

  As a preferred aspect of the present invention, the rotation / linear motion conversion mechanism includes a screw shaft, a nut whose inner peripheral surface is screwed to the outer peripheral surface of the screw shaft, and a linear guide that guides the axial movement of the screw shaft. It is preferable that the optical scale is rotated and linearly moved according to the rotation and linear motion of the screw shaft.

  With this configuration, the optical encoder can interlock the optical scale with the rotation and linear motion of the screw shaft.

  As a desirable mode of the present invention, the calculation means calculates the distance from the light source to a position where a virtual line extending in a direction parallel to the rotation axis of the optical scale reaches the optical scale, thereby calculating the optical scale. It is preferable to calculate the position.

  With this configuration, in the optical encoder, the change of the polarization axis repeats the increase / decrease twice per rotation of the optical scale, but the optical scale is rotated from the reference position based on the rotation area of the optical scale. The absolute angle can be specified. The optical encoder can increase the detection accuracy of the position of the optical scale. Further, the optical encoder can calculate a multi-rotation angle including rotation of the optical scale of 360 ° or more.

  As a desirable mode of the present invention, it is preferable that the light intensity light receiving portions are arranged around the light source and at equal distances from the light source.

  With this configuration, the arithmetic device can easily calculate the position of the optical scale.

  As a desirable mode of the present invention, it is preferable that the angle sensor has a comb-tooth shape in which the first light receiving part with a polarizing layer and the second light receiving part with a polarizing layer are engaged with each other with a certain distance therebetween.

  With this configuration, it is possible to reduce the possibility that the first light receiving unit with a polarizing layer and the second light receiving unit with a polarizing layer are shielded to the same extent by a foreign substance, and one of them significantly lowers the signal intensity. . For this reason, even if the light intensity of the incident light is reduced by the foreign matter, the angle sensor can detect a change in the polarization direction of the transmitted light or the reflected light in a state where the influence on the foreign matter is reduced. In addition, even when a distribution exists in the light source, if the first light receiving unit with a polarizing layer and the second light receiving unit with a polarizing layer are comb-like, the influence of the polarization direction is reduced in a state where the influence on the distribution of the light source is reduced. Changes can be detected.

  ADVANTAGE OF THE INVENTION According to this invention, the optical encoder which detects an absolute angle using the optical scale in which the polarization direction of the polarizer in a surface has faced one direction can be provided.

FIG. 1 is a configuration diagram of an encoder unit according to the first embodiment. FIG. 2 is an explanatory diagram illustrating an example of the arrangement of the optical scale and the optical sensor unit. FIG. 3 is a block diagram of the encoder according to the first embodiment. FIG. 4 is an explanatory diagram illustrating an example of an optical scale pattern according to the first embodiment. FIG. 5 is an explanatory diagram for explaining an example of the optical sensor unit according to the first embodiment. FIG. 6A is an explanatory diagram for explaining an example of the first light receiving unit with a polarizing layer of the angle sensor according to the first embodiment. FIG. 6B is an explanatory diagram for explaining an example of the second light receiving unit with a polarizing layer of the angle sensor according to the first embodiment. FIG. 7-1 is an explanatory diagram for explaining separation of polarization components of the angle sensor according to the first embodiment. FIG. 7-2 is an explanatory diagram for explaining separation of polarization components of the angle sensor according to the first embodiment. FIG. 7C is an explanatory diagram for explaining separation of polarization components of the angle sensor according to the first embodiment. FIG. 8 is an explanatory diagram for explaining changes in the rotation angle of the optical scale and the polarization component of the angle sensor according to the first embodiment. FIG. 9 is a flowchart calculated by the optical encoder according to the first embodiment. FIG. 10A is an explanatory diagram for explaining the surface normal of the optical scale according to the first embodiment. FIG. 10-2 is an explanatory diagram for explaining the surface normal of the optical scale according to the first embodiment. FIG. 10C is an explanatory diagram for explaining the surface normal of the optical scale according to the first embodiment. FIG. 11 is a detailed flowchart of step S2. FIG. 12 is an explanatory diagram for explaining an operation example of the optical sensor unit according to the first embodiment. FIG. 13 is an explanatory diagram for explaining an operation example of the optical sensor unit according to the first embodiment. FIG. 14 is an explanatory diagram illustrating an example of database information in which the distance between the shortest position where the light source light of the light source on the optical scale is irradiated from the light source and the rotation angle are associated with each other. FIG. 15 is an explanatory diagram for explaining a first modification of the linear motion guide mechanism according to the first embodiment. FIG. 16 is an explanatory diagram for describing a second modification of the linear motion guide mechanism according to the first embodiment. FIG. 17 is an explanatory diagram for describing a third modification of the linear motion guide mechanism according to the first embodiment. FIG. 18 is an explanatory diagram for explaining an example of the optical sensor unit according to the second embodiment. FIG. 19 is an explanatory diagram for explaining an example of the optical sensor unit according to the second embodiment. FIG. 20 is an explanatory diagram illustrating an example of the arrangement of the optical scale and the optical sensor unit according to the second embodiment. FIG. 21 is an explanatory diagram for explaining an example of the optical sensor unit according to the third embodiment. FIG. 22 is an explanatory diagram for explaining an arrangement example of the light intensity light receiving units of the optical sensor unit according to the third embodiment. FIG. 23 is an explanatory diagram for explaining the surface normal of the optical scale according to the third embodiment. FIG. 24 is a detailed flowchart of step S2 according to the third embodiment. FIG. 25 is an explanatory diagram for explaining an angle sensor according to the fourth embodiment. FIG. 26A is an explanatory diagram for explaining the first light receiving unit with a polarizing layer and the second light receiving unit with a polarizing layer according to the fourth embodiment. FIG. 26B is an explanatory diagram for explaining a modification of the first light receiving unit with a polarizing layer and the second light receiving unit with a polarizing layer according to the fourth embodiment. FIG. 27A is an explanatory diagram for explaining separation of polarization components of the angle sensor according to the fourth embodiment. FIG. 27B is an explanatory diagram for explaining separation of polarization components of the angle sensor according to the fourth embodiment. FIG. 27C is an explanatory diagram for explaining separation of polarization components of the angle sensor according to the fourth embodiment. FIG. 27-4 is an explanatory diagram for explaining reduction in variation in the amount of light detected by the optical sensor according to the fourth embodiment. FIG. 28 is a flowchart for explaining a manufacturing process of the optical sensor according to the fourth embodiment. FIG. 29A is an explanatory diagram for explaining a manufacturing process of the optical sensor according to the fourth embodiment. FIG. 29-2 is an explanatory diagram for explaining a manufacturing process of the optical sensor according to the fourth embodiment. FIG. 29C is an explanatory diagram for explaining the manufacturing process of the optical sensor according to the fourth embodiment. FIGS. 29-4 is explanatory drawing for demonstrating the manufacturing process of the optical sensor which concerns on Embodiment 4. FIGS. FIGS. 29-5 is explanatory drawing for demonstrating the manufacturing process of the optical sensor which concerns on Embodiment 4. FIGS. FIGS. 29-6 is explanatory drawing for demonstrating the manufacturing process of the optical sensor which concerns on Embodiment 4. FIGS. FIG. 30 is a configuration diagram of an electric power steering apparatus according to the fifth embodiment.

  DESCRIPTION OF EMBODIMENTS Embodiments (embodiments) for carrying out the present invention will be described in detail with reference to the drawings. The present invention is not limited by the contents described in the following embodiments. The constituent elements described below include those that can be easily assumed by those skilled in the art and those that are substantially the same. Furthermore, the constituent elements described below can be appropriately combined.

(Embodiment 1)
FIG. 1 is a configuration diagram of an encoder unit according to the first embodiment. FIG. 2 is an explanatory diagram illustrating an example of the arrangement of the optical scale and the optical sensor unit. FIG. 3 is a block diagram of the encoder according to the first embodiment. FIG. 4 is an explanatory diagram illustrating an example of an optical scale pattern according to the first embodiment. The encoder unit 1 includes a shaft 29 connected to a rotary machine such as a motor, a housing 20A that is a stator, a rotor 10, and an optical sensor unit 31 that can read a signal pattern.

  The rotor 10 includes an optical scale 11 that is a disk-shaped member, a screw shaft 25, a rotating portion 22 that rotates together with the shaft 29, a linear motion guide mechanism 24 provided in the rotating portion 22, and a linear motion guide. And a moving unit 23 guided by the mechanism 24. The optical scale 11 is made of, for example, silicon, glass, or a polymer material. The optical scale 11 has a signal track T1 on one plate surface. The rotation center of the shaft 29, the rotation part 22, and the screw shaft 25 is coaxial and is the rotation center Zr. Even if the optical scale 11 is inclined like the optical scale 11A, if the inclination angle is small, the polarization separation function is not affected. That is, even if the optical scale 11 is inclined with respect to a plane orthogonal to the rotation center Zr due to the swing of the screw shaft 25, like the optical scale 11A, it functions as a polarization separation element.

  The screw shaft 25 is a rod-shaped member disposed at the rotation center Zr of the rotating unit 22. The screw shaft 25 is a ball screw shaft in which a screw groove is formed on the outer peripheral surface. The optical scale 11 is fixed to one end of the screw shaft 25, and the moving unit 23 is fixed to the other end.

  The housing 20A fixes the bearing portion 21 and the nut 26. Further, the inner peripheral surface of the nut 26 is screwed to the outer peripheral surface of the screw shaft 25. For example, the nut 26 is screwed into the screw groove of the screw shaft 25 that is a ball screw shaft through a rolling element present in the screw groove on the inner peripheral surface. With this structure, the nut 26 supports the screw shaft 25 inserted in the inner peripheral surface. Since the screw shaft 25 is inserted into the nut 26, the end portion is exposed from the end portion of the nut 26. In the nut 26, since the ball rolls between the screw shaft 25 and the nut 26, the friction is small, and the efficiency of making the rotary motion a linear motion can be increased. Further, the thread groove of the screw shaft 25 is formed longer than the length in the direction parallel to the rotation center Zr of the nut 26.

  The screw shaft 25 may be another type of screw shaft, for example, a trapezoidal screw shaft or a triangular screw shaft. When other screw shafts such as a trapezoidal screw shaft and a triangular screw shaft are applied to the screw shaft 25 instead of the ball screw shaft, the frictional force with which the screw grooves of the trapezoidal screw shaft and the triangular screw shaft are screwed with the nut 26. Can be used to suppress reverse operation of the screw shaft.

  The linear motion guide mechanism 24 is, for example, a ball spline mechanism. The linear motion guide mechanism 24 can transmit the rotational force of the rotating unit 22 to the moving unit 23 and can guide the movement of the moving unit 23 in the axial direction of the screw shaft 25 that is parallel to the rotation center Zr. .

  The housing 20A supports the shaft 29 via the bearing portion 21 so as to be rotatable. When the rotational force from the motor is transmitted to the shaft 29, the rotating portion 22 of the rotor 10 rotates about the rotation center Zr in conjunction with the shaft 29. Due to the rotation of the rotating unit 22, the screw shaft 25 rotates via the linear motion guide mechanism 24 and the moving unit 23. When the screw shaft 25 rotates with respect to the nut 26 by the rotation of the screw shaft 25, the screw shaft 25 rotates and linearly moves in the axial direction of the screw shaft 25 according to the pitch of the thread groove to be screwed. The moving unit 23 moves in a direction parallel to the rotation center Zr following the movement of the linear motion of the screw shaft 25 in the axial direction. Then, in conjunction with the rotation of the screw shaft 25, the optical scale 11 is displaced in a direction parallel to the rotation center Zr at the same time as the rotation. The encoder unit 1 can be applied to a multi-rotation encoder by the optical sensor unit 31 detecting a displacement in a direction parallel to the rotation center Zr.

  As shown in FIG. 1, the optical sensor unit 31 is fixed to the housing 20 </ b> A and is disposed at a position facing the optical scale 11. When the rotor 10 described above rotates, the signal track T1 of the optical scale 11 moves relative to the optical sensor unit 31 in the R direction, for example. As shown in FIG. 2, the optical sensor unit 31 includes a light source 41. The light source light 71 of the light source 41 is reflected by the signal track T1 of the optical scale 11, and the optical sensor unit 31 detects this reflected reflected light 72 as incident light. The encoder unit 1 according to the first embodiment is not limited to the arrangement of the reflection type optical scale and the optical sensor unit described above, and may be the arrangement of a transmission type optical scale and an optical sensor as in the embodiments described later. The light source 41 is, for example, a light emitting diode or a semiconductor laser light source.

  The optical encoder 2 includes the encoder unit 1 and the arithmetic device 3 described above, and the optical sensor unit 31 of the encoder unit 1 and the arithmetic device 3 are connected as shown in FIG. The arithmetic device 3 is connected to a control unit 5 of a rotary machine such as a motor.

  In the optical encoder 2, the optical sensor unit 31 detects reflected light 72 that is incident on the optical scale 11 when the light source light 71 is transmitted or reflected. The arithmetic device 3 calculates the relative position between the rotor 10 of the encoder unit 1 and the optical sensor unit 31 from the detection signal of the optical sensor unit 31, and uses the relative position information as a control signal to control the control unit 5 of a rotating machine such as a motor. Output to.

  The arithmetic device 3 is a computer such as a personal computer (PC), and includes an input interface 4a, an output interface 4b, a CPU (Central Processing Unit) 4c, a ROM (Read Only Memory) 4d, and a RAM (Random Access Memory). 4e and an internal storage device 4f. The input interface 4a, output interface 4b, CPU 4c, ROM 4d, RAM 4e, and internal storage device 4f are connected by an internal bus. Note that the arithmetic device 3 may be configured by a dedicated processing circuit.

  The input interface 4a receives an input signal from the optical sensor unit 31 of the encoder unit 1 and outputs it to the CPU 4c. The output interface 4 b receives a control signal from the CPU 4 c and outputs it to the control unit 5.

  A program such as BIOS (Basic Input Output System) is stored in the ROM 4d. The internal storage device 4f is, for example, an HDD (Hard Disk Drive), a flash memory, or the like, and stores an operating system program and application programs. The CPU 4c implements various functions by executing programs stored in the ROM 4d and the internal storage device 4f while using the RAM 4e as a work area.

  The internal storage device 4f, which is a storage unit, stores a database in which a polarization axis (to be described later) in the optical scale 11 and the sensor output of the optical sensor unit 31 are associated with each other. Further, the internal storage device 4f stores a database in which a value of distance D described later is associated with position information of the optical scale 11. Alternatively, the internal storage device 4f may also store a database in which values of parameter azimuth angle φ and inclination angle (zenith angle) θ, which will be described later, are associated with position information of the optical scale 11.

  In the signal track T1 shown in FIG. 4, an array of fine metal wires (wires) g called a wire grid pattern is formed on the optical scale 11 shown in FIG. The optical scale 11 linearly arranges adjacent fine metal wires g as signal tracks T1 in parallel. For this reason, the optical scale 11 has the same polarization axis regardless of the position where the light source light 71 is irradiated, and the polarization direction of the polarizer in the plane is in one direction.

  Further, the optical scale 11 having the fine metal wires g called the wire grid pattern can improve the heat resistance as compared with the light-induced polarizing plate. Further, since the optical scale 11 is a line pattern having no intersecting portions locally, the optical scale 11 can be an optical scale with high accuracy and few errors. Moreover, since the optical scale 11 can be stably manufactured by batch exposure or nanoimprint technology, the optical scale 11 can be an optical scale with high accuracy and less error. The optical scale 11 may be a light-induced polarizing plate.

  The plurality of fine metal wires g are arranged without intersecting. Between adjacent metal thin wires g is a transmission region w through which all or part of the light source light 71 can be transmitted. When the width of the fine metal wire g and the interval between the adjacent fine metal wires g, that is, the width of the fine metal wire g and the width of the transmission region w are sufficiently smaller than the wavelength of the light source light 71 of the light source 41, the optical scale 11 The reflected light 72 can be polarized and separated. For this reason, the optical scale 11 has a polarizer with a uniform polarization axis in the plane. In the rotating circumferential direction of the optical scale 11, the polarization axis of incident light incident on the optical sensor unit 31 changes according to the rotation of the optical scale 11. In the first embodiment, the change of the polarization axis repeats the increase / decrease twice for one rotation of the optical scale 11.

  The optical scale 11 does not need to be finely divided into segments having different polarization directions. Since the optical scale 11 has a uniform polarization axis, there is no boundary between regions having different polarization axes, and disturbance of the polarization state of the reflected light 72 due to this boundary can be suppressed. The optical encoder 2 of Embodiment 1 can reduce the possibility of causing false detection or noise.

  FIG. 5 is an explanatory diagram for explaining an example of the optical sensor unit according to the first embodiment. FIG. 6A is an explanatory diagram for explaining an example of the first light receiving unit with a polarizing layer of the angle sensor according to the first embodiment. FIG. 6B is an explanatory diagram for explaining an example of the second light receiving unit with a polarizing layer of the angle sensor according to the first embodiment. As shown in FIGS. 2 and 5, the optical sensor unit 31 includes a light source 41, a first light receiving part PP (−) with a polarizing layer, and a second light receiving part PP with a polarizing layer ( +), Light intensity light receiving part PDx (+), light intensity light receiving part PDx (-), light intensity light receiving part PDy (+), and light intensity light receiving part PDy (-).

  As shown in FIG. 2, the light source light 71 emitted from the light source 41 is reflected by the optical scale 11 described above, and as the reflected light 72, the first light receiving part PP (−) with a polarizing layer and the second light receiving with a polarizing layer. It enters the part PP (+), the light intensity light receiving part PDx (+), the light intensity light receiving part PDx (−), the light intensity light receiving part PDy (+), and the light intensity light receiving part PDy (−).

  As shown in FIG. 5, the optical sensor unit 31 includes a light intensity light receiving unit PDx (+), a light intensity light receiving unit PDx (−), a light intensity light receiving unit PDy (+), and a light intensity light receiving unit PDy (−). Are arranged around the light source 41. When the light emission center of the light source 41 is O, light is emitted from each of the light intensity light receiving unit PDx (+), the light intensity light receiving unit PDx (−), the light intensity light receiving unit PDy (+), and the light intensity light receiving unit PDy (−). It is preferable to make the distances to the center O equal. With this structure, it is possible to reduce the calculation load on the CPU 4c which is the calculation means.

  Further, the light intensity light receiving part PDx (+) is arranged at a point-symmetrical position with respect to the light intensity light receiving part PDx (−) via the light emission center O, and the light intensity light receiving part PDy (+) is light transmitted via the light emission center O. It is disposed at a point-symmetrical position with respect to the intensity light receiving part PDy (−). In the first embodiment, the virtual axis on the surface of the unit substrate 30 that passes through the light intensity light receiving part PDx (+), the light emission center O, and the light intensity light receiving part PDx (−) is defined as the X axis, and the light intensity light receiving part PDy (+ ), A virtual axis on the surface of the unit substrate 30 passing through the light emission center O and the light intensity light receiving part PDy (−) is taken as a Y axis. In FIG. 5, the X axis is orthogonal to the Y axis on the surface of the unit substrate 30.

  As shown in FIG. 5, in the optical sensor unit 31, the first light receiving part PP (−) with a polarizing layer and the second light receiving part PP (+) with a polarizing layer are arranged around the light source 41. . When the light emission center of the light source 41 is O, the distance from the light emission center O to each of the first light receiving part PP (−) with a polarizing layer and the second light receiving part PP (+) with a polarizing layer may be equalized. preferable. With this structure, it is possible to reduce the calculation load on the CPU 4c which is the calculation means.

  As illustrated in FIG. 6A, the first light receiving unit PP (−) with a polarizing layer includes a silicon substrate 34, a light receiving unit 37, and a first polarizing layer 39a. Further, as illustrated in FIG. 6B, the second light receiving unit PP (+) with a polarizing layer includes a silicon substrate 34, a light receiving unit 37, and a second polarizing layer 39b. For example, the silicon substrate 34 is an n-type semiconductor, the light receiving portion 37 is a p-type semiconductor, and a photodiode formed by a PN junction with the silicon substrate 34 and the light receiving portion 37 can be configured. The first polarizing layer 39a and the second polarizing layer 39b can be formed of a light-induced polarizing layer or a wire grid pattern in which metal thin wires are arranged in parallel. The first polarizing layer 39a separates incident light that is incident on the optical scale 11 shown in FIG. 2 by reflecting the light source light 71 in the first polarization direction, and the second polarizing layer 39b separates the incident light into the second polarization direction. Separate in the polarization direction. It is preferable that the polarization axis of the first separated light and the polarization axis of the second separated light are relatively different by 90 °. With this configuration, the CPU 4c of the arithmetic device 3 can easily calculate the polarization angle.

  7A, 7B, and 7C are explanatory diagrams for explaining the separation of the polarization components of the angle sensor according to the first embodiment. As shown in FIG. 7A, incident light polarized in the polarization direction Pm is incident by the signal track T <b> 1 of the optical scale 11. In FIG. 7A, the sensing range includes a foreign matter D1 and a foreign matter D2. The polarization direction Pm of incident light can be expressed by the light intensity PI (−) of the first polarization direction component and the light intensity PI (+) of the second polarization direction component. As described above, the first polarization direction and the second polarization direction are preferably different from each other by 90 °, and are, for example, a + 45 ° component and a −45 ° component with respect to the reference direction. . In FIGS. 7-1, 7-2 and 7-3, the axial direction of the wire grid is shown parallel to the paper surface. When is small, the polarization separation function is not affected. That is, even if the optical scale 11 is inclined with respect to the rotation axis, it functions as a polarization separation element.

  As shown in FIG. 7B, the first light receiving unit PP (−) with a polarizing layer detects incident light through the first polarizing layer 39a that separates the incident light into the first polarization direction, and thus the first polarization direction. The light intensity PI (−) of the component is detected. As shown in FIG. 7-3, the second light receiving unit PP (+) with a polarizing layer detects incident light via the second polarizing layer 39b that separates the incident light into the second polarizing direction, and therefore the second polarizing direction. The light intensity PI (+) of the component is detected.

  FIG. 8 is an explanatory diagram for explaining changes in the rotation angle of the optical scale and the polarization component of the angle sensor according to the first embodiment. The CPU 4c of the arithmetic device 3 shown in FIG. 3 described above is a light intensity PI (−) of a component in the first polarization direction and a light intensity PI of a component in the second polarization direction, which are detection signals of the optical sensor unit 31. (+) Is acquired. The rotation angle of the optical scale 11 and the rotation angle of the polarization axis of the optical scale 11 are equal when the optical scale 11 is tilted and the tilt angle is small, and this value is represented by β in this embodiment. That is, β represents the rotation angle of the optical scale 11 and the rotation angle of the polarization axis of the optical scale. Then, the arithmetic device 3 rotates the optical scale 11 from the light intensity PI (−) of the component in the first polarization direction and the light intensity PI (+) of the component in the second polarization direction according to the following formula (1). The differential signal V that depends on is calculated.

  The differential signal V calculated by the equation (1) does not include a parameter that is affected by the light intensity of the light source light 71, and the optical encoder 2 determines the distance between the optical sensor unit 31 and the optical scale 11, The influence of variations in the light intensity of the light source 41 can be reduced. Then, as shown in Expression (1), the differential signal V is a function of the rotation angle β of the polarization axis of the optical scale 11 (hereinafter referred to as the polarization angle) β, which is the rotation angle of the optical scale 11.

  In the optical encoder 2, since the optical scale 11 is inclined, the distance between the optical sensor unit 31 and the optical scale 11 changes with the rotation of the optical scale 11, but the optical sensor unit 31 and the optical scale 11. Does not affect the differential signal V.

  Further, as shown in FIG. 7A, the optical encoder 2 has an influence on the foreign matter D1 and the foreign matter D2 even if the light intensity of the incident light is reduced by the foreign matter D1 and the foreign matter D2. In the state in which the above-mentioned is reduced, the above-described change in the polarization direction Pm can be detected by the differential signal V.

  The CPU 4c, which is an arithmetic means, performs a differential indicating the relative movement amount between the optical scale 11 and the angle sensor based on the light intensity PI (−) of the first separated light and the light intensity (+) of the second separated light. Although the signal V can be calculated, the differential signal V is repeatedly increased and decreased twice for one rotation of the optical scale 11 according to the rotation angle of the polarization axis. For this reason, the CPU 4c, which is the calculation means, specifies whether the rotation angle of the optical scale 11 is one of a region between 0 ° and less than 180 °, or a region between 180 ° and less than 360 °. Therefore, it is necessary to calculate the absolute angle. In addition, when the optical scale 11 rotates 360 ° or more (multi-rotation), the CPU 4c determines whether the rotation angle of the optical scale 11 is 360 ° or more and is in any position in the region every 180 °. After specifying, it is necessary to calculate the absolute angle.

  FIG. 9 is a flowchart calculated by the optical encoder according to the first embodiment. As described above, the CPU 4c of the calculation device 3 calculates the polarization angle (step S1). Next, the CPU 4c determines the distance (the moving distance of the optical scale 11) from the light source 41 to the position where the virtual line extending in the direction parallel to the rotation axis of the optical scale (the direction parallel to the rotation center Zr) reaches the optical scale 11. ) D is calculated (step S2).

10A, 10 </ b> B, and 10 </ b> C are explanatory diagrams for explaining surface normals of the optical scale according to the first embodiment. FIG. 10A illustrates the X axis, the Y axis, and the Z axis that passes through the light emission center O of the light source 41, is orthogonal to the X axis and the Y axis, and is parallel to the rotation center Zr. Even if the optical scale 11 is tilted so that the polarization direction of the polarizer in the plane is uniform and the surface normal is changed by the rotation, the CPU 4c of the arithmetic device 3 does not transmit the light of the position sensor described above. Light intensity I _x ⁺ , I _x ⁻ , I _y ⁺ detected by the light intensity receiver PDx (+), the light intensity receiver PDx (−), the light intensity receiver PDy (+), and the light intensity receiver PDy (−) , I _y ⁻ , the rotation angle of the optical scale 11 in the optical scale 11 can be calculated.

  The light emission center O of the light source 41 is set to (0, 0, 0), the light intensity light receiving part PDx (+) is set to (a, 0, 0), and the light intensity light receiving part PDx (−) is set to (−a, 0). , 0), the coordinates of the light intensity light receiving part PDy (+) are (0, a, 0), the coordinates of the light intensity light receiving part PDy (−) are (0, −a, 0), the Z axis and the optical scale 11 When the coordinate at which the plane Σ intersects is O ′ (0, 0, D), the CPU 4c calculates a surface normal vector (surface normal direction) η at the shortest position P between the light source 41 and the optical scale. Note that, when the optical scale 11 according to the first embodiment is not inclined, the shortest position P coincides with O ′ (0, 0, D). However, there is a possibility of tilting due to the swing of the screw shaft 25 or the fixing of the optical scale 11 may include tilt error and tilt. In such a case, when the optical scale 11 is inclined, the inclination angle (zenith angle) θ of the optical scale 11 is small, and a << D, the surface normal vector η is expressed by the following equation (2). Can be sought. The inclination angle (zenith angle) θ is a virtual line that connects the light source 41 with the shortest position P where the light source light of the light source 41 reaches the optical scale 11, and the light intensity light receiving part PDx (+) and the light intensity light receiving part PDx described above. (−), Vertical axis (Z-axis) including the light emission center O of the light source 41 among axes perpendicular to the reference plane (XY plane) including the light intensity light-receiving unit PDy (+) and the light intensity light-receiving unit PDy (−). ). The parameter azimuth angle (azimuth angle) includes the light emission center O of the light source 41 in the reference plane described above, and an azimuth reference line (for example, the X axis) arbitrarily defined as a reference line and the shortest position projected onto the reference plane This is an angle formed by a projection virtual line connecting P and the light emission center O of the light source 41. The distance D is a distance from the reference plane (XY plane) to the reference intersection point of the coordinate O ′ with the intersection point of the vertical axis (Z axis) and the optical scale 11 as the reference intersection point of the coordinate O ′. Here, in equation (2), the parameter azimuth is φ, the tilt angle (zenith angle) θ, and a virtual line extending from the light source 41 in a direction parallel to the rotation axis of the optical scale (a direction parallel to the rotation center Zr) ( Let D be the distance to the position where the Z axis) reaches the optical scale 11. Here, the parameter azimuth angle φ is equal to the polarization angle β described above.

FIG. 10-2 shows a cross section of the X-ξx plane including the shortest position P and the X axis described above with the coordinate axis obtained by rotating the Z axis around the X axis as the ξx axis. In FIG. 10-2, the distance from the intersection O ″ x between the X axis and the optical scale 11 to the light emission center O is η ₃ D / η ₁ . In FIG. 10-2, the distance from the shortest position P to the light emission center O described above is η ₃ D. In FIG. 10B, the distance from the intersection of the ξx axis and the optical scale 11 to the light emission center O is dx.

FIG. 10C illustrates a cross section of the Y-ξy plane including the shortest position P and the X axis described above, with the coordinate axis obtained by rotating the Z axis around the Y axis as the ξy axis. In FIG. 10-3, the distance from the intersection O ″ y between the Y axis and the optical scale 11 to the light emission center O is η ₃ D / η ₂ . In FIG. 10-3, the distance from the shortest position P to the light emission center O described above is η ₃ D. In FIG. 10C, the distance from the intersection of the ξy axis and the optical scale 11 to the light emission center O is dy.

  As can be seen from FIGS. 10-2 and 10-3, the distance D can be obtained by the following equation (3). The CPU 4c has a distance (moving distance of the optical scale 11) D from the light source 41 to a position where a virtual line extending in a direction parallel to the rotation axis of the optical scale (direction parallel to the rotation center Zr) reaches the optical scale 11. Arithmetic can be performed.

  Under the preconditions described above, the CPU 4c calculates the tilt angle αx of the optical scale 11 and the tilt angle αy of the optical scale 11 shown in FIG. 10-2 and FIG. Can be calculated.

FIG. 11 is a detailed flowchart of step S2. As shown in FIG. 11, the light intensity light receiving part PDx (+), the light intensity light receiving part PDx (−), the light intensity light receiving part PDy (+), and the light intensity light receiving part PDy (−) are respectively light intensity I _x ^+. , I _x ⁻ , I _y ⁺ , I _y ⁻ are detected (step S21).

Next, in step S <b> 22, the CPU 4 c calculates an average value I _av of light intensity from the light intensities I _x ⁺ , I _x ⁻ , I _y ⁺ , I _y ⁻ by the following formula (4).

Next, in step S22, CPU4c, the light intensity _I ^x +, _{I x} ^- by the following equation differential voltage _{V x} of (5) - from the light intensity light receiving unit PDx (+), the light intensity received portion PDx () Calculate.

Next, in step S22, the CPU 4c calculates the differential voltage V _y of the light intensity light receiving unit PDy (+) and the light intensity light receiving unit PDy (−) from the light intensities I _y ⁺ and I _y ⁻ by the following equation (6). Calculate.

CPU4c uses the resulting differential voltage _{V x} and the differential voltage _{V y,} calculates a Q value of formula (7).

After calculating the average value I _av , the differential voltage V _x , the differential voltage V _y, and the Q value of the light intensity, the CPU 4c advances the process to step S23 illustrated in FIG.

Next, in step S23, the CPU 4c calculates the parameter azimuth angle φ from the average value I _av , the differential voltage V _x , the differential voltage V _y and the Q value according to the following formula (8).

Next, in step S <b> 23, the CPU 4 c calculates the tilt angle (zenith angle) θ from the average value I _av , the differential voltage V _x , the differential voltage V _y and the Q value of the light intensity according to the following equation (9).

Next, in step S <b> 23, the CPU 4 c calculates the distance D from the average value I _av , the differential voltage V _x , the differential voltage V _y and the Q value of the light intensity according to the following formula (10).

  After calculating the distance D (step S24), the CPU 4c ends the process of step S2 shown in FIG. 9, and advances the process to step S3. Note that the CPU 4c can omit the calculation of the parameter azimuth angle φ and the tilt angle (zenith angle) θ described above. As a process of step 3, the CPU 4c calculates a multi-rotation angle including the rotation of the optical scale 11 of 360 ° or more based on the distance D (step S3). For example, the CPU 4c inquires the value of the distance D in the database of the internal storage device 4f that is a storage unit. Note that the calculation of the parameter azimuth angle φ and inclination angle (zenith angle) θ described above can be omitted.

  12 and 13 are explanatory diagrams for explaining an operation example of the optical sensor unit according to the first embodiment. FIG. 14 is an explanatory diagram illustrating an example of database information in which the distance between the shortest position where the light source light of the light source on the optical scale is irradiated from the light source and the rotation angle are associated with each other. When the rotational force from the motor is transmitted to the shaft 29, the rotating portion 22 of the rotor 10 rotates about the rotation center Zr in conjunction with the shaft 29. Due to the rotation of the rotating unit 22, the screw shaft 25 rotates via the linear motion guide mechanism 24 and the moving unit 23. When the screw shaft 25 rotates with respect to the nut 26 by the rotation of the screw shaft 25, the screw shaft 25 rotates and linearly moves in the axial direction of the screw shaft 25 according to the pitch of the thread groove to be screwed. For example, the value of the distance D in FIG. 13 is larger than the value of the distance D in FIG. The value of the distance D can be related to the rotation angle of the optical scale 11.

  For example, as shown in FIG. 14, when the value of the distance D is D0 or more and less than D1, the rotation range of the optical scale 11 is such that the rotation angle of the optical scale 11 from the reference position is 0 ° or more and less than 180 °. When the value of the distance D is not less than D1 and less than D2, the rotation angle of the optical scale 11 in the rotation area of the optical scale 11 is not less than 180 ° and less than 360 °. When the value of the distance D is not less than D2 and less than D3, the rotation angle of the optical scale 11 in the rotation area of the optical scale 11 is not less than 360 ° and less than 540 °. When the value of the distance D is not less than D3 and less than D4, in the rotation region of the optical scale 11, the rotation angle of the optical scale 11 from the reference position is not less than 540 ° and less than 720 °. When the value of the distance D is not less than D4 and less than D5, the rotation area of the optical scale 11 is such that the rotation angle of the optical scale 11 from the reference position is not less than 720 ° and less than 900 °. As described above, the CPU 4c can refer to the database of the internal storage device 4f, which is a storage unit, for the value of the distance D and derive the rotation angle of the optical scale 11.

  The rotation angle of the optical scale 11 calculated based on the value of the distance D may have some errors in the thread groove. For this reason, when the rotation angle of the optical scale 11 is not less than 0 ° and less than 180 °, the CPU 4c outputs the polarization angle β as the rotation angle of the optical scale 11 with high accuracy. When the rotation angle of the optical scale 11 is not less than 180 ° and less than 360 °, the CPU 4c outputs the polarization angle β + 180 ° as the rotation angle of the optical scale 11 with high accuracy. When the rotation angle of the optical scale 11 is 360 ° or more and less than 540 °, the CPU 4c outputs the polarization angle β + 360 ° as the rotation angle of the optical scale 11 with high accuracy. When the rotation angle of the optical scale 11 is not less than 540 ° and less than 720 °, the CPU 4c outputs the polarization angle β + 540 ° as the rotation angle of the optical scale 11 with high accuracy. When the rotation angle of the optical scale 11 is not less than 720 ° and less than 900 °, the CPU 4c outputs the polarization angle β + 720 ° as the rotation angle of the optical scale 11 with high accuracy.

  As described above, the CPU 4c calculates the distance D, inquires the value of the distance D in the database of the internal storage device 4f that is a storage unit, and calculates an integer n obtained by dividing the rotation angle of the optical scale 11 by 180 °. To do. Then, the CPU 4c calculates the above-described polarization angle β + 180 ° × n as an absolute angle. In this way, the optical encoder 2 can calculate the absolute angle of rotation of the optical scale 11 exceeding 180 °. Further, the optical encoder 2 can calculate the absolute angle of the optical scale 11 that rotates more than 360 °.

  As described above, the optical encoder 2 according to the first embodiment includes the light source 41, the optical scale 11, the first light receiving unit PP (−) with a polarizing layer, and the second light receiving unit PP (+) with a polarizing layer. An angle sensor including a light intensity light receiving unit PDx (+), a light intensity light receiving unit PDx (−), a light intensity light receiving unit PDy (+), a position sensor including the light intensity light receiving unit PDy (−), and an arithmetic means. A CPU 4c of a certain arithmetic device 3 and a rotation / linear motion conversion mechanism are included. The rotation / linear motion conversion mechanism includes a screw shaft 25, a nut 26 whose inner peripheral surface is screwed to the outer peripheral surface of the screw shaft 25, and a linear motion guide mechanism 24 that guides the axial movement of the screw shaft 25. . The optical scale 11 rotates and linearly moves according to the rotation and linear movement of the screw shaft 25.

In the optical scale 11, the polarization direction of the polarizer in the plane is in one direction. The CPU 4c of the arithmetic device 3 detects the light intensity light receiving part PDx (+), the light intensity light receiving part PDx (−), the light intensity light receiving part PDy (+), and the light intensity light receiving part PDy (−) of the position sensor described above. The aforementioned distance D in the optical scale 11 is calculated from the light intensities I _x ⁺ , I _x ⁻ , I _y ⁺ , I _y ⁻ . Then, based on the distance D, the CPU 4c of the arithmetic device 3 calculates the optical intensity from the light intensity PI (−) of the first separated light detected by the angle sensor and the light intensity PI (+) of the second separated light. An absolute angle of the optical scale 11 can be calculated by calculating a relative movement amount between the scale 11 and the angle sensor of the optical sensor unit 31.

  With this configuration, the angle sensor detects the rotation angle of the rotor 10 in a polarization state in which the reflected light 72 is polarized and separated. For this reason, compared with the case where the light intensity of incident light is directly detected, the optical encoder 2 can reduce the influence of fluctuations in the detected light amount due to the foreign matter D1, D2, or the like. Thereby, since the tolerance | permissible_range of a foreign material becomes wide, a use environment can be expanded.

  The optical scale 11 may be inclined such that the surface normal at the shortest position P changes due to rotation, like the optical scale 11A shown in FIG. In this case, when the CPU 4c calculates that O ′ (0, 0, D) is in an area of 0 ° or more and less than 180 ° based on the values of the parameter azimuth angle φ and the inclination angle (zenith angle) θ described above. The CPU 4c can calculate the polarization angle β described above as an absolute angle. For example, the values of the parameter azimuth angle φ and the inclination angle (zenith angle) θ are inquired to the database of the internal storage device 4f that is a storage means, and O ′ (0, 0, D) is in an area where 0 ° or more and less than 180 °. Can lead to being.

  Further, when the CPU 4c calculates O ′ (0, 0, D) in a region where the calculation is 180 ° or more and less than 360 ° based on the values of the parameter azimuth angle φ and the inclination angle (zenith angle) θ, the CPU 4c Can be calculated with the above-mentioned polarization angle β + 180 ° as an absolute angle. For example, the CPU 4c inquires the value of the parameter azimuth angle φ and the inclination angle (zenith angle) θ in the database of the internal storage device 4f that is a storage unit, and O ′ (0, 0, D) is 180 ° or more and less than 360 °. Can lead to being in the area.

(Modification)
FIG. 15 is an explanatory diagram for explaining a first modification of the linear motion guide mechanism according to the first embodiment. As described above, the rotating unit 22 rotates together with the shaft 29. As shown in FIG. 15, the linear motion guide mechanism 24 </ b> A of the rotor 10 </ b> A is a plurality of rod-shaped members (for example, three rod-shaped members), and is arranged in a direction parallel to the screw shaft 25. It can be inserted into the insertion hole. The linear guide mechanism 24A can transmit the rotational force of the rotating unit 22 to the moving unit 23 and can guide the movement of the moving unit 23 in the axial direction of the screw shaft 25, which is a direction parallel to the rotation center Zr. . The plurality of rod-like members are preferably 3 or more. Three or more rod-shaped members can transmit the rotational force of the rotating portion 22 to the moving portion 23 evenly as the number thereof increases.

  FIG. 16 is an explanatory diagram for describing a second modification of the linear motion guide mechanism according to the first embodiment. As shown in FIG. 16, the linear motion guide mechanism 24B of the rotor 10B can be inserted into an insertion hole of the rotating portion 22 opened in a direction parallel to the screw shaft 25, and has a polygon (for example, a corner on the outer periphery). , A square) square bar member. The linear motion guide mechanism 24B can transmit the rotational force of the rotating unit 22 to the moving unit 23 and guide the movement of the moving unit 23 in the axial direction of the screw shaft 25, which is a direction parallel to the rotation center Zr. .

  FIG. 17 is an explanatory diagram for describing a third modification of the linear motion guide mechanism according to the first embodiment. As shown in FIG. 17, the linear motion guide mechanism 24 </ b> C of the rotor 10 </ b> C can be inserted into the slit 22 a of the rotating portion 22 opened in a direction parallel to the screw shaft 25, and abuts in the rotational direction inside the slit 22 a. Thus, a rod-shaped member 24Ca having a length larger than the diameter of the rotating portion 22 is provided. The linear motion guide mechanism 24C can transmit the rotational force of the rotating unit 22 to the moving unit 23 and can guide the movement of the moving unit 23 in the axial direction of the screw shaft 25, which is a direction parallel to the rotation center Zr. .

(Embodiment 2)
18 and 19 are explanatory diagrams for explaining an example of the optical sensor unit according to the second embodiment. In addition, the same code | symbol is attached | subjected to the same member as Embodiment 1 mentioned above, and the overlapping description is abbreviate | omitted. The optical sensor unit 31 according to the second embodiment includes a position sensor 31A shown in FIG. 18 and an angle sensor 31B shown in FIG.

  In the position sensor 31A, the first light receiving part PP (−) with a polarizing layer and the second light receiving part PP (+) with a polarizing layer corresponding to the angle sensor of the optical sensor unit 31 described above are provided on the surface of the unit substrate 30. Instead, they are arranged on the surface of a unit substrate 30 a different from the unit substrate 30. Further, the angle sensor 31 </ b> B is disposed on the surface of the unit substrate 30 b different from the unit substrate 30. With this structure, the angle sensor 31B can be arranged at a position different from the position sensor 31A.

  Similar to the optical sensor unit 31 described above, the position sensor 31A includes a light source 41, a light intensity light receiving unit PDx (+), a light intensity light receiving unit PDx (−), and a light intensity light receiving on the surface of the unit substrate 30a. Part PDy (+) and light intensity light-receiving part PDy (-). In the position sensor 31A, the light intensity light receiving unit PDx (+), the light intensity light receiving unit PDx (−), the light intensity light receiving unit PDy (+), and the light intensity light receiving unit PDy (−) are arranged around the light source 41, respectively. ing. When the light emission center of the light source 41 is O, light is emitted from each of the light intensity light receiving unit PDx (+), the light intensity light receiving unit PDx (−), the light intensity light receiving unit PDy (+), and the light intensity light receiving unit PDy (−). The distance to the center O is equally arranged. Similar to the optical sensor unit 31 described above, the angle sensor 31B includes the first light receiving part PP (−) with a polarizing layer and the second light receiving part PP (+) with a polarizing layer on the surface of the unit substrate 30b. Including.

  FIG. 20 is an explanatory diagram illustrating an example of the arrangement of the optical scale and the optical sensor unit according to the second embodiment. As shown in FIG. 20, the light source light 71 emitted from the light source 41 is reflected by the optical scale 11 described above, and as reflected light 72, a light intensity light receiving part PDx (+), a light intensity light receiving part PDx (−), Light incident on the light intensity receiver PDy (+) and the light intensity receiver PDy (−). As shown in FIG. 20, the angle sensor 31 </ b> B is disposed at a position facing the light source 41 via the optical scale 11. With this configuration, the light source light 71 emitted from the light source 41 is transmitted through the optical scale 11 described above, and as the transmitted light 73, the first light receiving part PP (−) with a polarizing layer and the second light receiving part PP (with a polarizing layer) ( Incident on +).

  The first light receiving part PP (−) with a polarizing layer and the second light receiving part PP (+) with a polarizing layer include a first polarizing layer 39a and a second polarizing layer 39b, as in the first embodiment. The first polarizing layer 39a is a first polarizing layer that separates incident light that is transmitted through and incident on the optical scale 11 shown in FIG. 20 in the first polarization direction, and the second polarizing layer 39b is The incident light is separated in the second polarization direction. It is preferable that the polarization axis of the first separated light and the polarization axis of the second separated light are relatively different by 90 °. With this configuration, the CPU 4c of the arithmetic device 3 can easily calculate the polarization angle β.

  The angle sensor 31B described above detects the rotation angle of the rotor 10 in a polarization state in which the transmitted light 73 is polarized and separated. For this reason, compared with the case where the light intensity of incident light is directly detected, the optical encoder 2 can reduce the influence of fluctuations in the detected light amount due to foreign matter or the like. Thereby, since the tolerance | permissible_range of a foreign material becomes wide, a use environment can be expanded. As described above, in the optical encoder 2, the incident light is polarized and separated into the first separated light and the second separated light. As a result, the CPU 4c causes the relative relationship between the optical scale 11 and the angle sensor 31B based on the change in the polarization angle of the transmitted light 73 from the light intensity of each polarization component separated into the first polarization direction and the second polarization direction. The amount of movement can be calculated.

(Embodiment 3)
FIG. 21 is an explanatory diagram for explaining an example of the optical sensor unit according to the third embodiment. FIG. 22 is an explanatory diagram for explaining an arrangement example of the light intensity light receiving units of the optical sensor unit according to the third embodiment. FIG. 23 is an explanatory diagram for explaining the surface normal of the optical scale according to the third embodiment. The optical sensor unit 31C according to the third embodiment has one light intensity light receiving unit less than the optical sensor unit 31 according to the first embodiment. In addition, the same code | symbol is attached | subjected to the same member as Embodiment 1 mentioned above, and the overlapping description is abbreviate | omitted.

  As shown in FIG. 21, in the optical sensor unit 31 </ b> C, each of the light intensity light receiving unit PD <b> 1, the light intensity light receiving unit PD <b> 2, and the light intensity light receiving unit PD <b> 3 is disposed around the light source 41. When the light emission center of the light source 41 is O, it is preferable that the distances from the light intensity light receiving unit PD1, the light intensity light receiving unit PD2, and the light intensity light receiving unit PD3 to the light emission center O are equal. With this structure, it is possible to reduce the calculation load on the CPU 4c which is the calculation means. In the third embodiment, a position of any one of the light intensity light receiving unit PD1, the light intensity light receiving unit PD2, and the light intensity light receiving unit PD3 is set as ak, and an axis parallel to ak is set as a k axis.

FIG. 23 shows a cross section of the k-ξk plane including the shortest position P and the k axis described above with the coordinate axis obtained by rotating the Z axis around the K axis as the ξk axis. In FIG. 23, the distance from the intersection O ″ k between the k axis and the optical scale 11 to the light emission center O is η ₃ D / η _k . In FIG. 23, the distance from the shortest position P to the light emission center O is η ₃ D. In FIG. 23, the distance from the intersection of the ξk axis and the optical scale 11 to the light emission center O is dk.

  Under the preconditions described above, the CPU 4c determines the inclination angle αk (k is 3 or more) in each direction from the light emission center O shown in FIG. 22 to the light intensity receiving unit PD1, the light intensity receiving unit PD2, and the light intensity receiving unit PD3. ) Can be calculated, the surface normal vector (surface normal direction) η at the shortest position P can be calculated. When the optical scale 11 according to the first embodiment is not inclined, the shortest position P coincides with O ′ (0, 0, D).

FIG. 24 is a detailed flowchart of step S2 according to the third embodiment. The CPU 4c first performs the process of step S1 shown in FIG. 9, and then starts the process of step S2. Then, as shown in FIG. 24, the light intensity light receiving unit PD1, the light intensity light receiving unit PD2, and the light intensity light receiving unit PD3 detect the light intensities I ₁ , I ₂ , and I ₃ , respectively (step S201).

Next, in step S202, the CPU 4c calculates an average value I _av of light intensity from the light intensities I ₁ , I ₂ , and I ₃ by the following formula (11).

Then, following the step S202, CPU4c, the light intensity _{I 1,} I 2, _{I 3} from the light intensity light receiving unit PD1, a differential voltage _{V x} of the X-axis component in the light intensity light-receiving unit PD2, and the light intensity received portion PD3 Calculation is performed according to equation (12).

Next, in step S202, the CPU 4c calculates the differential voltage V _y of the Y-axis component in the light intensity light receiving part PD1, the light intensity light receiving part PD2, and the light intensity light receiving part PD3 from the light intensity I ₁ , I ₂ , I ₃ as follows. Calculation is performed according to equation (13).

CPU4c uses the resulting differential voltage _{V x} and the differential voltage _{V y,} calculates a Q value of formula (14).

The CPU 4c calculates the average value I _av , the differential voltage V _x , the differential voltage V _y, and the Q value of the light intensity (step S202), and then proceeds to step S203 shown in FIG.

Next, in step S203, the CPU 4c calculates the parameter azimuth angle φ from the average value I _av , the differential voltage V _x , the differential voltage V _y, and the Q value according to the following formula (15).

Next, in step S203, the CPU 4c calculates the tilt angle (zenith angle) θ from the average value I _av , the differential voltage V _x , the differential voltage V _y and the Q value of the light intensity according to the following equation (16).

Next, in step S203, CPU4c calculates the average value of the light intensity _{I av,} differential voltage _{V x,} the following equation the distance D from the differential voltage _{V y} and Q value (17).

  After calculating the distance D (step S204), the CPU 4c ends the process of step S2 shown in FIG. 9 and advances the process to step S3. Note that the CPU 4c can omit the calculation of the parameter azimuth angle φ and the tilt angle (zenith angle) θ described above. As a process of step 3, the CPU 4c calculates a multi-rotation angle including the rotation of the optical scale 11 of 360 ° or more based on the distance D (step S3). For example, the CPU 4c inquires the value of the distance D in the database of the internal storage device 4f that is a storage unit. Note that the calculation of the parameter azimuth angle φ and inclination angle (zenith angle) θ described above can be omitted.

  For example, as shown in FIG. 14 described above, when the value of the distance D is D0 or more and less than D1, the rotation angle of the optical scale 11 is 0 ° or more and less than 180 °. When the value of the distance D is not less than D1 and less than D2, the rotation angle of the optical scale 11 is not less than 180 ° and less than 360 °. When the value of the distance D is not less than D2 and less than D3, the rotation angle of the optical scale 11 is not less than 360 ° and less than 540 °. When the value of the distance D is not less than D3 and less than D4, the rotation angle of the optical scale 11 is not less than 540 ° and less than 720 °. When the value of the distance D is D4 or more and less than D5, the rotation angle of the optical scale 11 is 720 ° or more and less than 900 °. As described above, the CPU 4c can refer to the database of the internal storage device 4f, which is a storage unit, for the value of the distance D and derive the rotation angle of the optical scale 11.

The rotation angle of the optical scale 11 calculated based on the value of the distance D has some errors in the thread groove. For this reason, when the rotation angle of the optical scale 11 is not less than 0 ° and less than 180 °, the CPU 4c outputs the polarization angle β as the rotation angle of the optical scale 11 with high accuracy. When the rotation angle of the optical scale 11 is not less than 180 ° and less than 360 °, the CPU 4c outputs the polarization angle β + 180 ° as the rotation angle of the optical scale 11 with high accuracy. When the rotation angle of the optical scale 11 is 360 ° or more and less than 540 °, the CPU 4c outputs the polarization angle β + 360 ° as the rotation angle of the optical scale 11 with high accuracy. When the rotation angle of the optical scale 11 is not less than 540 ° and less than 720 °, the CPU 4c outputs the polarization angle β + 540 ° as the rotation angle of the optical scale 11 with high accuracy. When the rotation angle of the optical scale 11 is not less than 720 ° and less than 900 °, the CPU 4c outputs the polarization angle β + 720 ° as the rotation angle of the optical scale 11 with high accuracy.

  The CPU 4c calculates the distance D, inquires the value of the distance D in the database of the internal storage device 4f that is a storage unit, and calculates an integer n obtained by dividing the rotation angle of the optical scale 11 by 180 °. Then, the CPU 4c calculates the above-described polarization angle β + 180 ° × n as an absolute angle. In this way, the optical encoder 2 can calculate the absolute angle of rotation of the optical scale 11 exceeding 180 °. Further, the optical encoder 2 can calculate the absolute angle of the optical scale 11 that rotates more than 360 °. Next, when the control unit 5 of the rotating machine such as a motor does not stop the rotation (No in Step S4), the CPU 4c returns the process to Step S1 and calculates the polarization angle. CPU4c complete | finishes a process, when the control part 5 of rotary machines, such as a motor, stops rotation (step S4, Yes).

  As described above, the optical encoder 2 according to the third embodiment includes the light source 41, the optical scale 11, the first light receiving unit PP (−) with a polarizing layer, and the second light receiving unit PP (+) with a polarizing layer. Includes a position sensor including a light intensity light receiving unit PD1, a light intensity light receiving unit PD2, and a light intensity light receiving unit PD3, a CPU 4c of the calculation device 3 serving as calculation means, and a rotation / linear motion conversion mechanism. The rotation / linear motion conversion mechanism includes a screw shaft 25, a nut 26 whose inner peripheral surface is screwed to the outer peripheral surface of the screw shaft 25, and a linear motion guide mechanism 24 that guides the axial movement of the screw shaft 25. . The optical scale 11 rotates and linearly moves according to the rotation and linear movement of the screw shaft 25.

In the optical scale 11, the polarization direction of the polarizer in the plane is in one direction. The CPU 4c of the arithmetic device 3 uses the light intensity I ₁ , I ₂ , and I ₃ detected by the light intensity light receiving unit PD1, light intensity light receiving unit PD2, and light intensity light receiving unit PD3 of the position sensor described above in the optical scale 11 as described above. The distance D is calculated. Then, based on the distance D, the CPU 4c of the arithmetic device 3 calculates the optical intensity from the light intensity PI (−) of the first separated light detected by the angle sensor and the light intensity PI (+) of the second separated light. The absolute angle of the optical scale 11 can be calculated by calculating the relative amount of movement between the scale 11 and the angle sensor of the optical sensor unit 31C.

  In addition, the optical scale 11 may be inclined so that the surface normal changes by rotation like the optical scale 11A shown in FIG. In this case, when the CPU 4c calculates that O ′ (0, 0, D) is in an area of 0 ° or more and less than 180 ° based on the values of the parameter azimuth angle φ and the inclination angle (zenith angle) θ described above. The CPU 4c can calculate the polarization angle β described above as an absolute angle. For example, the values of the parameter azimuth angle φ and the inclination angle (zenith angle) θ are inquired to the database of the internal storage device 4f that is a storage means, and O ′ (0, 0, D) is in an area where 0 ° or more and less than 180 °. Can lead to being.

  Further, the CPU 4c is not in a region where O ′ (0, 0, D) is 0 ° or more and less than 180 ° based on the values of the parameter azimuth angle φ and the inclination angle (zenith angle) θ (O ′ (0, 0). , D) is in a region where the calculation is 180 ° or more and less than 360 °), the CPU 4c can calculate the above-described polarization angle β + 180 ° as an absolute angle. For example, the CPU 4c inquires the value of the parameter azimuth angle φ and the inclination angle (zenith angle) θ in the database of the internal storage device 4f that is a storage unit, and O ′ (0, 0, D) is 180 ° or more and less than 360 °. Can lead to being in the area.

(Embodiment 4)
FIG. 25 is an explanatory diagram for explaining an angle sensor according to the fourth embodiment. FIG. 26A is an explanatory diagram for explaining the first light receiving unit with a polarizing layer and the second light receiving unit with a polarizing layer according to the fourth embodiment. In addition, the same code | symbol is attached | subjected to the same member as Embodiment 1 mentioned above, and the overlapping description is abbreviate | omitted.

  In the angle sensor unit 31BB shown in FIG. 25, each of the angle sensors 35 includes a first light receiving part 36A with a polarizing layer and a second light receiving part 36B with a polarizing layer shown in FIG. 26-1. The first light receiving part 36A with a polarizing layer includes an electrode base part 36KA and a first light receiving part 36a, and can detect the light intensity in the first polarization direction. The first light receiving unit 36a includes a first polarizing layer 39a that separates the above-described incident light in the first polarization direction, and receives the first separated light separated by the first polarizing layer 39a.

  The second light receiving part with polarization layer 36B includes an electrode base part 36KB and a second light receiving part 36b, and can detect the light intensity in the second polarization direction. The second light receiving unit 36b includes a second polarizing layer 39b that separates the above-described incident light in the second polarization direction, and receives the second separated light separated by the second polarizing layer 39b. And as shown to FIGS. 26-1, the 1st light-receiving part 36a and the 2nd light-receiving part 36b are formed in the comb-tooth shape which mutually meshes | intersects a fixed distance. The electrode base portion 36KA and the electrode base portion 36KB are made of a conductor such as Au, and can energize the first light receiving portion 36a and the second light receiving portion 36b, respectively. When the electrode base 36KA and the electrode base 36KB are light shielding bodies, noise can be further suppressed.

(Modification)
FIG. 26B is an explanatory diagram for explaining a modification of the first light receiving unit with a polarizing layer and the second light receiving unit with a polarizing layer according to the fourth embodiment. The angle sensor 35 includes a first light receiving part 36A with a polarizing layer and a second light receiving part 36B with a polarizing layer. The first light receiving part 36A with a polarizing layer includes an electrode base part 36KA, a sensor base part 36Ka connected to the electrode base part 36KA, and a first light receiving part 36a, and can detect the light intensity in the first polarization direction. . The first light receiving unit 36a includes a first polarizing layer 39a that separates the above-described incident light in the first polarization direction, and receives the first separated light separated by the first polarizing layer 39a.

  The second light receiving part with polarization layer 36B includes an electrode base part 36KB, a sensor base part 36Kb connected to the electrode base part 36KB, and a second light receiving part 36b, and can detect the light intensity in the second polarization direction. . The second light receiving unit 36b includes a second polarizing layer 39b that separates the above-described incident light in the second polarization direction, and receives the second separated light separated by the second polarizing layer 39b. As shown in FIG. 26-2, the first light receiving part 36a and the second light receiving part 36b are formed in a comb-teeth shape that meshes with each other at a predetermined distance. The electrode base portion 36KA and the electrode base portion 36KB are made of a conductor such as Au, and can energize the first light receiving portion 36a and the second light receiving portion 36b, respectively.

  FIGS. 27-1, 27-2, and 27-3 are explanatory diagrams for explaining the separation of polarization components of the angle sensor according to the fourth embodiment. As shown in FIG. 27A, incident light obtained by polarizing the light source light 71 in the polarization direction Pm by the optical scale 11 enters the signal track T <b> 1 in the sensing range of the angle sensor 35. In FIG. 27A, the sensing range includes a foreign matter D1 and a foreign matter D2. The polarization direction Pm of incident light can be expressed by the light intensity PI (−) of the first polarization direction component and the light intensity PI (+) of the second polarization direction component. The first polarization direction and the second polarization direction are preferably different from each other by 90 °, and are, for example, a + 45 ° component and a −45 ° component with respect to the reference direction.

  As shown in FIG. 27-2, the first light receiving unit 36A with a polarizing layer detects light through the first polarizing layer that separates the incident light into the first polarization direction, and thus the light of the component in the first polarization direction. Intensity PI (-) is detected. As shown in FIG. 27C, the second light receiving unit with polarization layer 36B detects the incident light through the second polarization layer that separates the incident light in the second polarization direction. Intensity PI (+) is detected.

  The arithmetic device 3 described above acquires the light intensity PI (−) of the first polarization direction component and the light intensity PI (+) of the second polarization direction component, which are detection signals of the angle sensor 35. . Then, the arithmetic unit 3 obtains the differential signal V from the light intensity PI (−) of the first polarization direction component and the light intensity PI (+) of the second polarization direction component according to the above-described equation (1). Calculate.

  FIG. 27-4 is an explanatory diagram for explaining a reduction in variation in the detected light amount of the angle sensor according to the fourth embodiment. As shown in FIG. 27-4, even if the foreign matter D3 shields a part of the sensing range, the probability that the first light receiving unit 36a and the second light receiving unit 36b are shielded to the same extent increases. It is possible to reduce the possibility that one of the signals will extremely reduce the signal strength. For this reason, even if the light intensity of the incident light is reduced by the foreign matter D3, the optical encoder 2 can detect the change in the polarization direction Pm with the differential signal V in a state where the influence on the foreign matter D3 is reduced. it can.

(Optical sensor manufacturing method)
FIG. 28 is a flowchart for explaining a manufacturing process of the optical sensor according to the fourth embodiment. FIGS. 29-1 to 29-6 are explanatory diagrams for explaining a manufacturing process of the optical sensor according to the fourth embodiment. FIGS. 29-1 to 29-6 are partial cross-sectional views for explaining the manufacturing process of the GG cross section of FIG. 26-1. The optical sensor manufacturing process will be described with reference to FIGS. 26-1, 28, and 29-1 to 29-6.

  As shown in FIG. 28, first, the manufacturing apparatus prepares an n-type silicon substrate 34 shown in FIG. 29-1 (step S11). Next, the manufacturing apparatus performs a doping process of doping an element such as B or In on the silicon substrate 34 (step S12). As shown in FIG. 29-2, a P-type semiconductor light receiving portion 37 is formed on the silicon substrate.

  Next, as shown in FIG. 28, the manufacturing apparatus performs an etching process in which etching is performed by masking the silicon substrate 34 with a photoresist so that the comb-like patterning as shown in FIG. It performs (step S13). The etching may be physical etching or chemical etching. Or the manufacturing apparatus of step S13 performs the etching process which masks with the resist pattern formed by the nanoimprint with respect to the silicon substrate 34 so that it may become comb-like patterning as shown in FIG. May be. As shown in FIG. 29-3, a recess 38a is formed on the surface of the silicon substrate 34 by etching. As a result, the first light receiving part with polarization layer 36A and the second light receiving part with polarization layer 36B shown in FIG. 26A are separated.

  Next, as shown in FIG. 28, the manufacturing apparatus performs an insulating process of covering the recess 38a with an insulator such as alumina by a sputtering process (step S14). As a result, as shown in FIG. 29-4, the recess 38a of the silicon substrate 34 shown in FIG. 29-3 is filled with the insulator 38b. In the insulating step, it is more preferable to flatten the surface so that the light receiving portion 37 is exposed.

  Next, as illustrated in FIG. 28, the manufacturing apparatus performs a first polarizing layer forming step of forming the first polarizing layer 39 a at a position that becomes the first light receiving unit 36 a illustrated in FIG. 26A (step S <b> 15). . The first polarizing layer 39a can be formed of a light-induced polarizing layer or a wire grit pattern in which fine metal wires are arranged in parallel. As a result, as shown in FIG. 29-5, the first polarizing layer 39a is formed on every other light receiving portion 37.

  Next, as illustrated in FIG. 28, the manufacturing apparatus performs a second polarizing layer forming step of forming the second polarizing layer 39 b at a position that becomes the second light receiving unit 36 b illustrated in FIG. 26A (Step S <b> 16). . The second polarizing layer 39b can be formed of a light-induced polarizing layer or a wire grit pattern in which fine metal wires are arranged in parallel. As a result, as shown in FIG. 29-6, the second polarizing layer 39b is formed on every other light receiving portion 37. The electrode base portion 36KA and the electrode base portion 36KB shown in FIG. 26-1 are formed of a conductor such as Au so that the first light receiving portion 36a and the second light receiving portion 36b can be energized.

  In the angle sensor 35 shown in FIG. 29-6, the first light receiving part 36a and the second light receiving part 36b are formed in a comb-teeth shape that meshes with each other at a predetermined distance. The first light receiving unit 36a includes a first polarizing layer 39a that separates incident light in the first polarization direction, and the first separated light separated by the first polarizing layer 39a is formed by a PN junction. Light can be received by a photodiode. The second light receiving unit 36b includes a second polarizing layer 39b that separates the incident light in the second polarization direction. The second separated light separated by the second polarizing layer 39b is formed by a PN junction. The received photodiode can receive light. Note that light reception is not limited to a photodiode formed by a PN junction, and a phototransistor or the like may be used.

  The angle sensor 35 described above splits incident light into first separated light and second separated light. As a result, the calculation device 3 can calculate the polarization angle of the reflected light 72 or the transmitted light 73 from the signal intensity of each polarization component separated into the first polarization direction and the second polarization direction. The angle sensor unit 31BB includes a plurality of angle sensors 35 to be redundant, and the CPU 4c calculates a polarization angle based on each angle sensor 35 and takes an average value, thereby reducing the influence of the foreign matter D1 and D2. . In addition, the first light receiving part 36A with the polarizing layer and the second light receiving part 36B with the polarizing layer are shielded to the same extent by the foreign matter D3, so that it is possible to reduce the possibility that one of them will extremely reduce the signal intensity. it can. For this reason, even if the light intensity of the incident light is reduced by the foreign matter D3, the angle sensor 35 detects a change in the polarization direction of the transmitted light 73 or the reflected light 72 in a state where the influence on the foreign matter D3 is reduced. Can do. In addition, even when a distribution exists in the light source 41, if the first light receiving part with polarization layer 36A and the second light receiving part with polarization layer 36B are comb-like, the influence on the distribution of the light source 41 is reduced. The change in the polarization direction can be detected. Further, it is more preferable that the first polarization direction and the second polarization direction are directions that are relatively different by 90 °. Thereby, the arithmetic unit 3 can easily calculate the polarization angle β.

(Embodiment 5)
FIG. 30 is a configuration diagram of an electric power steering apparatus according to the fifth embodiment. In addition, the same code | symbol is attached | subjected to the same member as what was mentioned above, and the overlapping description is abbreviate | omitted. In the present embodiment, the above-described optical encoder 2 is used as the rotation detection means of the torque sensor 91a.

  The electric power steering apparatus 80 includes a steering wheel 81, a steering shaft 82, a steering force assist mechanism 83, a universal joint 84, a lower shaft 85, a universal joint 86, A pinion shaft 87, a steering gear 88, and a tie rod 89 are provided. The electric power steering device 80 includes an ECU (Electronic Control Unit) 90, a torque sensor 91a, and a vehicle speed sensor 91v. Note that the arithmetic device 3 described above may function as the ECU 90 or may be provided separately from the ECU 90.

  The steering shaft 82 includes an input shaft 82a and an output shaft 82b. The input shaft 82a has one end connected to the steering wheel 81 and the other end connected to the steering force assist mechanism 83 via the torque sensor 91a. The output shaft 82 b has one end connected to the steering force assist mechanism 83 and the other end connected to the universal joint 84. In the present embodiment, the input shaft 82a and the output shaft 82b are made of a magnetic material such as iron.

  The lower shaft 85 has one end connected to the universal joint 84 and the other end connected to the universal joint 86. The pinion shaft 87 has one end connected to the universal joint 86 and the other end connected to the steering gear 88.

  Steering gear 88 includes a pinion 88a and a rack 88b. The pinion 88a is connected to the pinion shaft 87. The rack 88b meshes with the pinion 88a. The steering gear 88 is configured as a rack and pinion type. The steering gear 88 converts the rotational motion transmitted to the pinion 88a into a linear motion by the rack 88b. The tie rod 89 is connected to the rack 88b.

  Steering force assist mechanism 83 includes a reduction gear 92 and a brushless motor 101. The reduction gear 92 is connected to the output shaft 82b. The brushless motor 101 is an electric motor that is connected to the reduction gear 92 and generates auxiliary steering torque. In the electric power steering device 80, a steering column is constituted by the steering shaft 82, the torque sensor 91a, and the speed reducer 92. The brushless motor 101 gives auxiliary steering torque to the output shaft 82b of the steering column. That is, the electric power steering apparatus 80 of this embodiment is a column assist system.

  The optical encoder 2 described in the above-described embodiment can be used to detect the rotation angle of the torque sensor 91a. The torque sensor 91a detects the driver's steering force transmitted to the input shaft 82a via the steering wheel 81 as a steering torque. The vehicle speed sensor 91v detects the traveling speed of the vehicle on which the electric power steering device 80 is mounted. The ECU 90 is electrically connected to the brushless motor 101, the torque sensor 91a, and the vehicle speed sensor 91v. The brushless motor 101 may be a motor with a brush and may be a rotary motor.

  The ECU 90 controls the operation of the brushless motor 101. Further, the ECU 90 acquires signals from each of the torque sensor 91a and the vehicle speed sensor 91v. That is, the ECU 90 acquires the steering torque T from the torque sensor 91a, and acquires the traveling speed Vb of the vehicle from the vehicle speed sensor 91v. The ECU 90 is supplied with electric power from a power supply device (for example, a vehicle-mounted battery) 99 with the ignition switch 98 turned on. The ECU 90 calculates an assist steering command value of the assist command based on the steering torque T and the traveling speed Vb. Then, the ECU 90 adjusts the power value X supplied to the brushless motor 101 based on the calculated auxiliary steering command value. The ECU 90 acquires information on the induced voltage as the operation information Y from the brushless motor 101.

  The steering force of the driver (driver) input to the steering wheel 81 is transmitted to the speed reduction device 92 of the steering force assist mechanism 83 via the input shaft 82a. At this time, the ECU 90 acquires the steering torque T input to the input shaft 82a from the torque sensor 91a, and acquires the traveling speed Vb from the vehicle speed sensor 91v. The ECU 90 controls the operation of the brushless motor 101. The auxiliary steering torque created by the brushless motor 101 is transmitted to the speed reducer 92.

  The steering torque (including auxiliary steering torque) output via the output shaft 82 b is transmitted to the lower shaft 85 via the universal joint 84 and further transmitted to the pinion shaft 87 via the universal joint 86. The steering force transmitted to the pinion shaft 87 is transmitted to the tie rod 89 via the steering gear 88 to steer the steered wheels.

  As described above, the electric power steering device 80 can detect the steering torque by attaching the first rotating shaft and the second rotating shaft of the torque sensor 91a described above to the steering shaft 82.

  With this configuration, the optical sensor unit 31 described above can detect a change in the polarization direction of transmitted light or reflected light in a state in which the influence on the foreign matter is reduced. Thereby, the reliability of the electric power steering apparatus can be improved.

DESCRIPTION OF SYMBOLS 1 Encoder unit 2 Optical encoder 3 Arithmetic device 4c CPU
5 Control section 10, 10A, 10B, 10C Rotor 11 Optical scale 20A Housing 21 Bearing section 22 Rotating section 22a Slit 23 Moving section 24, 24A, 24B, 24C Linear motion guide mechanism 24Ca Bar-shaped member 25 Screw shaft 26 Nut 29 Shaft 30, 30a, 30b Unit substrates 31, 31C Optical sensor unit 31A Position sensor 31B Angle sensor 31BB Angle sensor unit 34 Silicon substrate 35 Angle sensor 71 Light source light 72 Reflected light 73 Transmitted light 80 Electric power steering device g Metal thin wires PD1, PD2, PD3, PDx (+), PDx (-), PDy (+), PDy (-) Light intensity detector

Claims (5)

A light source;
An optical scale in which the polarization direction of the polarizer in the plane faces one direction;
A rotation / linear motion conversion mechanism for rotating the optical scale by the transmitted rotational force and transmitting a linear motion of the optical scale interlocking with the rotation;
Light source light of the light source is transmitted through or reflected by the optical scale, and incident light incident thereon is separated in a first polarization direction, and polarized light is received by the first separated light separated by the first polarization layer. A first light receiving unit with a layer, a second polarizing layer that separates the incident light in a second polarization direction, a second light receiving unit with a polarizing layer that receives the second separated light separated by the second polarizing layer, An angle sensor including:
A position sensor including three or more light intensity light receiving parts that receive incident light reflected from the light source and reflected by the optical scale;
From the light intensity detected by the light intensity receiving unit of the position sensor, the shortest position of the light source irradiated with the light source light of the light source is calculated, and the light intensity of the first separated light and the second separated light are calculated. A calculating means for calculating a relative movement amount between the optical scale and the angle sensor from the light intensity of the light, and calculating an absolute angle of the optical scale based on the shortest position and the relative movement amount; ,
An optical encoder comprising:   The rotation / linear motion conversion mechanism includes a screw shaft, a nut whose inner peripheral surface is screwed to the outer peripheral surface of the screw shaft, and a linear motion guide mechanism that guides the axial movement of the screw shaft, The optical encoder according to claim 1, wherein the optical scale rotates and linearly moves according to the rotation and linear movement of the screw shaft.   The said calculating means calculates the position of the said optical scale by calculating the distance from the said light source to the position where the virtual line extended in the direction parallel to the rotating shaft of the said optical scale reaches the said optical scale. The optical encoder according to claim 2.   The optical encoder according to any one of claims 1 to 3, wherein the light intensity light receiving units are arranged around the light source and at equal distances from the light source.   The said angle sensor is a comb-tooth shape with which the said 1st light-receiving part with a polarizing layer and the said 2nd light-receiving part with a polarizing layer mesh | engage at a fixed distance mutually. Optical encoder.

Images