JP2004251893A - Optical encoder - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an optical encoder which can decrease wraparound components and crosstalk toward a light receiving element and has stable phase difference by eliminating wiring overlap. <P>SOLUTION: A periodic light intensity distribution pattern having a certain pitch (P) is generated by irradiating an emitted light from a light source (102) to a scale (104). A plurality of light receiving element groups which is a group in which a plurality of light elements having the same phase are located to be adjacent to each other and change their position according to the scale are provided. The light receiving element groups are arranged in a line. Each light receiving element group has a certain phase difference. A centroids of areas (28, 29; 38, 39) on the phase axis for the light receiving element groups in which the phase differences thereof have certain relationships with each other are made to agree. <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

  The present invention relates to a photoelectric encoder, and more particularly, to a photoelectric encoder that uses a displacement encoder scale and is used for position measurement of various machine tools, semiconductor manufacturing apparatuses, and the like, detection of a moving amount of a moving object, and the like.

  In a conventional photoelectric encoder, a light-receiving element having a width P / 2 of an A phase, a B phase, a / A phase, and a / B phase having a phase difference of P / 4 with respect to a signal pitch P in a scale moving direction. The four light receiving elements having different phases are arranged as one set, and a plurality of light receiving element groups are arranged in the moving direction of the scale to detect the moving amount of the scale, that is, the moving amount and the relative position of the moving object. are doing. The light source is arranged on the side opposite to the light receiving element with respect to the scale, and the duty (DUTY) ratio of the scale is set to 50% (for example, see Patent Document 1).

  As another conventional example, light receiving elements of A phase, B phase, / A phase, and / B phase having a phase difference of P / 4 with respect to the signal pitch P are arranged at every 3P / 4 in the scale moving direction. A photoelectric encoder that is arranged at intervals and detects the amount of movement of a scale is disclosed (for example, see Patent Document 2).

  Here, the pitch P is each interval between the plurality of light passing slits formed on the scale, and is the same as the signal period. Further, in the description of the present specification, for the A phase, B phase, / A phase, and / B phase having a predetermined phase difference, the / A phase is the A phase and the / B phase is the B phase inverted differential. This means that the signals have a complementary relationship (the phase difference is 180 degrees).

JP-A-8-2011117 (paragraph 0008, FIG. 2) JP-A-2002-236033 (paragraphs 0067 to 0069, FIG. 10)

  However, in the conventional photoelectric encoder as described above, the pitch is narrow, so that it is not possible to secure a space for providing the crosstalk preventing means, and an optical signal may sneak to the light receiving elements or crosstalk between the light receiving elements may occur. There was an inconvenience of doing it. In order to provide a means for preventing such crosstalk, it is conceivable to make the width of the light receiving element smaller than P / 2. However, if the width of the light receiving element is made smaller in this way, the signal output decreases.

  Further, in the conventional photoelectric encoder, the wiring is complicated, and in some places, the wirings overlap each other, which makes it difficult to manufacture the light receiving element array. Further, there is a problem that an error occurs in the phase difference of each phase due to the fluctuation of the radiation angle of the light source.

  SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems, and a photoelectric encoder capable of securing a space for providing a crosstalk preventing means between each light receiving element and reducing a wraparound component of an optical signal to the light receiving element and crosstalk. The purpose is to provide. It is another object of the present invention to reduce the crosstalk between wirings by eliminating the overlapping of the wirings and to facilitate the manufacture of the light receiving element array.

  Further, it is another object of the present invention to provide a photoelectric encoder capable of performing stable differential amplification without being affected by a variation in the radiation angle of a light source and reducing a phase error after differential due to a radiation angle error.

  In order to achieve the above object, a photoelectric encoder according to the present invention includes a scale that generates a periodic light intensity distribution pattern having a predetermined pitch (P) by irradiating with a radiation light from a light source, and a relative displacement between the scale and the scale. And a plurality of light receiving element groups for detecting the amount of movement based on signals having a predetermined phase difference from each of the plurality of light receiving element groups. A plurality of light receiving elements are arranged in each light receiving element group, and a plurality of light receiving elements having the same phase are adjacent to each other to form one light receiving element group, and a plurality of light receiving element groups are arranged in parallel.

  As described above, the light receiving elements of the same phase are adjacent to each other, and a plurality of light receiving elements of the same phase are arranged as a set, and a plurality of light receiving element groups are arranged in parallel. A space for providing members can be secured, and a signal light sneaking component to the light receiving element and crosstalk can be reduced. Further, the overlapping of the wirings can be eliminated, and the manufacture of the light receiving element array can be facilitated.

  Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings. In the drawings, common elements are denoted by the same reference numerals, and redundant description is omitted for simplicity.

(Embodiment 1)
Embodiment 1 of the present invention will be described below with reference to FIGS. FIG. 1 shows a schematic configuration of a photoelectric encoder according to Embodiment 1 of the present invention, and FIG. 2 is an enlarged view of a light receiving element array in which a plurality of sets of light receiving elements are arranged on the basis of a phase.
In FIG. 1, reference numeral 102 denotes a light source such as an LED, which generates radiated light for irradiating the rotary scale 104. Reference numeral 103 denotes a disk that rotates around the rotation shaft 108, and rotates integrally with the movement of the test object (not shown).

  The rotary scale 104 has a configuration in which a plurality of divided light-passing slits are formed radially, and are arranged concentrically radially in a disk (rotating body) 103 around a rotation axis 108 of the disk 103. The rotary scale 104 has a central axis 101 of an irradiation pattern perpendicular to the optical axis, and a duty ratio (DUTY) is 50% at a pitch P of the scale. Reference numeral 106 denotes a light receiving element array, in which a plurality of light receiving elements 105 such as photodiodes that receive transmitted light from the rotary scale 104 and perform photoelectric conversion are arranged, and the light receiving element array 106 is irradiated with a scale pattern having a pitch P. It is configured to: Here, the central axis 101 of the irradiation pattern of the scale coincides with the central axis of the light receiving element array 106 (described later with reference to FIG. 2).

  In the light receiving element array 106 shown in FIG. 2, a total of 16 light receiving elements each having a width of substantially P / 2 are arranged, and have a phase difference of 90 degrees with respect to the reference A phase (22). It is configured to detect four signals of a B phase (24), a / A phase (23) having a phase difference of 180 degrees, and a / B phase (25) having a phase difference of 270 degrees. It corresponds to. Regarding the arrangement position of each light receiving element, first, the A-phase light receiving element A1 is arranged, and the second A-phase light receiving element A2 is arranged at a position where the distance between the centers of the light receiving elements is the pitch P. Subsequently, the / A-phase light-receiving element / A1 is disposed at a position where the distance between the center of the light-receiving element and A2 is 3P / 2, and the / A-phase light-receiving elements / A2, / A3, / A4 are provided at every interval P. Are sequentially arranged.

  Next, the third light receiving element A3 of the A phase is arranged at a position where the distance between the center of the light receiving element from / A4 is 3P / 2, and further, the fourth light receiving element A4 of the A phase is arranged at an interval P. Is placed. Similarly, the B-phase light-receiving element B1 is arranged at a position where the distance between the light-receiving element A4 and the center of the light-receiving element is 5P / 4, the B-phase light-receiving element B2 is arranged at intervals P, and The / B-phase light receiving element / B1 is arranged at a position where the distance between the centers is 3P / 2, and the / B-phase light receiving elements / B2, / B3, / B4 are sequentially arranged at intervals P. Further, the third light receiving element B3 of the B phase is arranged at a position where the distance between / B4 and the center of the light receiving element is 3P / 2, and the light receiving element B4 of the B phase is arranged at an interval P. I have. That is, each light receiving element group is formed by four light receiving elements having the same phase, and in each light receiving element group, at least two light receiving elements are arranged adjacent to each other.

  In the above configuration, reference numeral 28 denotes a common area centroid on the phase axis 109 of each of the A-phase and / A-phase light receiving element groups, and 29 denotes a common area center of gravity on each of the B-phase and / B-phase light receiving element groups. Area centroid. Further, the light receiving element group is arranged such that the phase distance from the center axis 101 of the irradiation pattern to the area center of gravity 28 on the phase axis is equal to the phase distance from the center axis 101 to the area center of gravity 29.

  Fourteen signals of A phase 22, B phase 24, / A phase 23, and / B phase 25 are detected by a total of 16 light receiving elements divided into four light receiving element groups, and A phase 22 and / A phase 23, B The signals are differentially amplified by the phase 24 and the / B phase 25 to generate signals (22, 23; 24, 25) having a phase difference of 90 degrees. A common dummy layer 26 is provided as an intercepting layer for preventing crosstalk in an empty space between each of the 16 adjacent light receiving elements, and a light component incident on the dummy layer 26 is detected as a dummy signal (D) 27. Thereby, while blocking between the light receiving elements, the light that has once entered the space between the light receiving elements is absorbed as the dummy signal 27, thereby preventing the light from entering the light receiving element.

  As an example, if the average radius of the rotary scale 104 formed on the disk 103 from the rotation axis center O is r = 9.55 mm and the number of divisions of the rotary scale is 500, the average pitch P of the rotary scale is 2πr / 500. It is determined to be approximately 120 μm. At this time, the empty space between the light receiving elements is at least P / 2 (that is, 60 μm), and a sufficient space for providing the dummy layer 26 is secured.

  In such a configuration, by providing the dummy layer 26, it is possible to reduce a sneak component to each light receiving element and crosstalk between each signal component. Further, each signal component can be detected without overlapping the wiring of the A phase 22, B phase 24, / A phase 23, / B phase 25 and the dummy signal 27. Further, in the A phase 22 and the / A phase 23, and in the B phase 24 and the / B phase 25, the area centroids on the phase axis of the light receiving element group are completely matched.

  That is, the area centroids of the A-phase light receiving element groups A1, A2, A3, and A4 and the area centroids of the / A-phase light receiving element groups / A1, / A2, / A3, and / A4 are both area centroids 28 and B phase The area centroids of the light receiving element groups B1, B2, B3, and B4 of the above and the area centroids of the light receiving element groups / B1, / B2, / B3, and / B4 of the / B phase are both area centroids 29. By matching the area centroids on the phase axis of the light receiving element group in this way, it is possible to stabilize the phase difference between a plurality of signals having a predetermined phase without being affected by variations in the radiation angle of the light source. Can be.

  Further, the phase distance from the center axis 101 of the irradiation pattern to the area gravity center 28 of the A phase 22 and the / A phase 23 on the phase axis is equal to the phase distance from the area gravity center 29 of the B phase 24 and the / B phase 25. are doing. As described above, in the plurality of light receiving element groups having a predetermined phase difference, the area centroid on the phase axis of each light receiving element group is arranged symmetrically with respect to the center axis (101) of the light emitted from the light source. Accordingly, the phase difference between a plurality of signals having a predetermined phase difference can be stabilized without being affected by the axially symmetric component in the variation of the radiation angle of the light source.

  FIG. 5 is an explanatory diagram showing an example of a variation in the radiation angle from the light source. In the figure, 51 is a light source, 52 is a scale, 53 is a light receiving element array, 53 is a normal radiated light, and a solid line 55 is a radiated light at the time of occurrence of an error. An example of a radiation angle variation in which a phase error of a phase difference of 90 degrees has occurred is shown.

  On the other hand, in the first embodiment, as shown in FIG. 2, the area centroid positions on the phase axis of the light receiving element groups of the A phase 22 and the / A phase 23 and the B phase 24 and the / B phase 25 match. By doing so, it is possible to stabilize the phase difference between a plurality of signals having a predetermined phase difference without being affected by variations in the radiation angle of the light source.

  Further, since the area center of gravity 28 and the area center of gravity 29 are arranged symmetrically with respect to the central axis 101 of the irradiation pattern, a predetermined phase difference can be obtained without being affected by the axially symmetric component of the radiation angle variation of the light source. It is possible to stabilize the phase difference between the plurality of signals.

(Embodiment 2)
Embodiment 2 of the present invention will be described below with reference to FIG. FIG. 3 is an enlarged view of the light receiving element array 206 of the photoelectric encoder according to the second embodiment of the present invention, illustrating each light receiving element based on the phase.

  As shown in FIG. 3, in the light-receiving element array 206, the arrangement position of each light-receiving element is such that the distance between the centers of the light-receiving elements from the A-phase light-receiving element A <b> 1 is the pitch P, and the second A-phase The light receiving element A2 is arranged. Subsequently, a B-phase light-receiving element B1 is arranged at a position where the distance between the centers of the light-receiving elements from A2 is 5P / 4, and B-phase light-receiving elements B2, B3, and B4 are sequentially arranged at intervals of P. I have.

  Next, the third light-receiving element A3 of the A-phase is arranged at a position where the distance between the centers of the light-receiving elements from B4 is 7P / 4. Are placed. Similarly, the first light receiving element / A1 of the / A phase is disposed at a position where the distance between the light receiving element A4 and the center of the light receiving element is 3P / 2, and the second light receiving element / A2 is disposed at an interval P. Then, the first light receiving element / B1 of the / B phase is arranged at a position where the distance between the center of the light receiving element and / A2 is 5P / 4, and the light receiving element / B2 of the / B phase is arranged at every interval P. , / B3 and / B4 are sequentially arranged. Further, a third light receiving element / A3 of the / A phase is arranged at a position where the distance between / B4 and the center of the light receiving element is 7P / 4, and a fourth light receiving element of the / A phase is further provided at an interval P. The element / A4 is arranged. Also in this configuration, as in the first embodiment, each light receiving element group is formed by four light receiving elements having the same phase, and in each light receiving element group, at least two light receiving elements are arranged adjacent to each other. I have.

  In the above configuration, the phase distance from the center axis 101 of the irradiation pattern to the area gravity center 38 of the A phase and the B phase on the phase axis is substantially equal to the phase distance from the area gravity center 39 of the / A phase and the / B phase. The light receiving element group is arranged as described above.

  From these 16 light receiving elements, four signals of A phase 32, B phase 34, / A phase 33, and / B phase 35 are detected, and A phase 32 and / A phase 33, and B phase 34 and / B phase 35 The signal is differentially amplified to generate a signal having a phase difference of 90 degrees. A common dummy layer 36 is provided in an empty space between the 16 light receiving elements, and a light component incident on the dummy layer 36 is detected as a dummy signal (D) 37. Thus, while blocking between the light receiving elements, the light once entering the space between the light receiving elements is absorbed as the dummy signal 37, thereby preventing the light from sneaking into the light receiving elements.

  In such a configuration, by providing the dummy layer 36, it is possible to reduce a sneak component to each light receiving element and crosstalk between each signal component. Further, each signal component can be detected without overlapping the wiring of the A phase 32, the B phase 34, the / A phase 33, the / B phase 35 and the dummy signal 37. Further, the phase distance from the center axis 101 of the irradiation pattern to the area center of gravity 38 of the A phase 32 and the B phase 34 on the phase axis is equal to the phase distance from the area center of gravity 39 of the / A phase 33 and the / B phase 35. Therefore, it is possible to perform stable differential amplification without being affected by disturbance such as radiation angle fluctuation.

  As described above, in the second embodiment, as shown in FIG. 3, the radiation angles of the light receiving element groups of the A phase 32 and the / A phase 33 and the B phase 34 and the / B phase 35 as shown in FIG. Phase error after differential due to error can be reduced.

(Embodiment 3)
Embodiment 3 of the present invention will be described below with reference to FIG. FIG. 4 is an enlarged view of a light receiving element array of the photoelectric encoder according to the third embodiment of the present invention, in which each light receiving element is illustrated based on a phase.

  As shown in FIG. 4, in the light receiving element array 306, the position of each light receiving element is such that the light receiving element A 1 of the A-phase is disposed first, and the second position is the position where the distance between the centers of the light receiving elements is the pitch P. An A-phase light receiving element A2 is arranged. Subsequently, a B-phase light receiving element B1 is arranged at a position where the distance between A2 and the center of the light receiving element is 5P / 4, and furthermore, a light receiving element B2 is arranged at an interval P.

  Next, the first light receiving element / A1 of the / A phase is arranged at a position where the distance between the centers of the light receiving elements from B2 is 5P / 4, and the light receiving element / A2 is further arranged at an interval P. I have. A / B phase light receiving element / B1 is arranged at a position where the distance between / A2 and the center of the light receiving element is 5P / 4, and a light receiving element / B2 is arranged at an interval P.

  Similarly, an A-phase light receiving element A3 is arranged at a position where the distance between / B2 and the center of the light receiving element is 5P / 4, and furthermore, a light receiving element A4 is arranged at an interval P. The B-phase light receiving element B3 is disposed at a position where the distance between the light receiving element A4 and the center of the light receiving element is 5P / 4, and the light receiving elements B4 are disposed at intervals P. Subsequently, the / A-phase light receiving element / A3 is arranged at a position where the distance between B4 and the center of the light receiving element is 5P / 4, and the light receiving elements / A4 are sequentially arranged at intervals P, and / A4 is further arranged. , A third light receiving element / B3 of the / B phase is arranged at a position where the distance between the centers of the light receiving elements is 5P / 4, and furthermore, the light receiving element / B4 is arranged at an interval P. Thus, in the above configuration, for example, the distance between the centers of the light receiving elements of the adjacent light receiving element groups represented by the light receiving elements A2 and B1 is set to 5P / 4. Also in this configuration, similarly to the first and second embodiments, each light receiving element group is formed by four light receiving elements having the same phase, and at least two light receiving elements are adjacent to each other in each light receiving element group. Are placed.

  From these 16 light receiving elements, four signals of A-phase 42, B-phase 44, / A-phase 43 and / B-phase 45 are detected and differentially amplified to generate a signal having a phase difference of 90 degrees. A common dummy layer 46 is provided in an empty space between the 16 light receiving elements for preventing crosstalk, and a light component incident on the dummy layer 46 is detected as a dummy signal (not shown). Thus, while blocking between the light receiving elements, the light that has once entered the space between the light receiving elements is absorbed as a dummy signal, thereby preventing the light from sneaking into the light receiving elements. Thus, the area of the entire light receiving element array can be reduced while maintaining the juxtaposed arrangement and the arrangement of the dummy layers, as compared with the case where the light receiving elements are arranged one by one at intervals of 5P / 4.

  In the first to third embodiments, each light receiving element group is formed by four light receiving elements having the same phase, and in each light receiving element group, at least two light receiving elements are arranged adjacent to each other. However, the number of light receiving elements in each light receiving element group may be increased or decreased according to the pitch of the scale or the irradiation area of the light source. Further, the width of the light receiving elements constituting the light receiving element group is P / 2, but this width may be narrowed or widened. The phase difference of each light receiving element group is set to 0 degree, 90 degrees, 180 degrees, and 270 degrees every 90 degrees as in the first to third embodiments. Although it is preferable in that two signals having a 90-degree phase difference are obtained by dynamic amplification, the phase difference of each light-receiving element group may be a phase difference other than 90 degrees. For example, eight light-receiving element groups are formed every 45 degrees. By forming the signals and differentially amplifying signals having a phase difference of 180 degrees to obtain four signals having a phase difference of 45 degrees, the number of signals increases, but the accuracy of phase detection can be improved.

  Further, the phase difference between the respective light receiving element groups may be non-uniform. For example, the phase difference between the light receiving element groups is 90 ° and 270 °, although the light receiving element group is easily affected by the fluctuation of the radiation angle and the intensity of the light source. Alternatively, the configuration may be such that the light receiving element group has only two phases of 0 ° and 90 °, and two signals having a 90 ° phase difference are obtained without performing differential amplification.

  Further, although the number of light receiving element groups having a predetermined phase difference is four, the number of light receiving element groups having a predetermined phase difference may be any number such as two, three, or eight. Further, it is desirable that the area centers of gravity on the respective phase axes of the plurality of light receiving element groups having a predetermined relationship with respect to the phase difference are completely matched. The effect of stabilizing the phase difference is obtained. In addition, it is preferable that the area centroids on the respective phase axes of the plurality of light receiving element groups having a predetermined relationship with respect to the phase difference are arranged axially symmetrically with respect to the central axis of the light emitted from the light source. Even in the case of symmetry, the effect of stabilizing the phase difference between the plurality of light receiving element groups can be obtained.

  As shown in FIG. 6, a light receiving element 61 having a width equal to or greater than the pitch P, and a light shielding plate 63 in which a plurality of light receiving windows 62 having a width of P / 2 are arranged at a pitch P (that is, in the same phase). Can be combined to form one light receiving element group. Further, in FIG. 6, the width of the light receiving window 62 is P / 2, but the width may be narrowed or widened.

  In addition, although a scale having a duty ratio of 50% is used at the pitch P for the rotary scale, any scale that changes periodically at the pitch P, such as a scale that changes in a sine wave shape or a triangular wave shape at the pitch P, may be used. Further, a light-blocking member such as a vapor-deposited film may be arranged between the adjacent light receiving elements to reduce crosstalk. It is also possible to provide a signal light blocking means, for example, by etching between the light receiving elements, to reduce crosstalk. Further, although the rotary encoder has been described in the above embodiment, the present invention is similarly applicable to a linear encoder.

  As described above, according to the present invention, it is possible to secure a space for providing a crosstalk preventing member between each light receiving element even at a relatively narrow pitch, and to utilize the signal light wraparound component and the crosstalk to the light receiving element. it can. Further, the overlapping of the wirings can be eliminated, and the manufacture of the light receiving element array can be utilized for facilitation. In addition, the area centroids of the light receiving element groups of the A phase and the / A phase, and the B phase and the / B phase are made to coincide with each other, and the positions of the area centroids are arranged axially symmetric with respect to the center axis of the irradiation pattern. It can be used to stabilize the phase difference between a plurality of signals without being affected by radiation angle fluctuation.

FIG. 2 is a perspective view of a principal part showing a schematic configuration of a photoelectric encoder according to Embodiment 1 of the present invention. FIG. 2 is an enlarged view of a light receiving element array in which light receiving elements of the photoelectric encoder shown in FIG. 1 are arranged. FIG. 9 is an enlarged view of a light receiving element array in which light receiving elements of a photoelectric encoder according to a second embodiment of the present invention are arranged. FIG. 11 is an enlarged view of a light receiving element array in which light receiving elements of a photoelectric encoder according to Embodiment 3 of the present invention are arranged. FIG. 4 is an explanatory diagram illustrating an example of a variation in radiation angle from a light source. It is a perspective view showing an example of a light sensing element group.

Explanation of reference numerals

22, 32, 42 A phase signal, 23, 33, 43 / A phase signal, 24, 34, 44 B phase signal, 25, 35, 45 / B phase signal, 26, 36, 46 dummy layer, 27, 37 dummy Signals, 28, 29, 38, 39 Area center of gravity of light receiving element group, 61 light receiving elements, 62 light receiving windows, 63 light shielding plate, 101 central axis, 102 light source, 103 disk, 104 rotary scale, 105 light receiving elements, 106, 206 , 306 light receiving element array, 108 rotation axis

Claims (9)

A scale that generates a periodic light intensity distribution pattern of a predetermined pitch (P) by irradiating with a radiation light from a light source; and a plurality of light receiving element groups that are displaced relative to the scale. Based on a signal having a phase difference of a predetermined phase from each, in a photoelectric encoder that detects the amount of movement,
A photoelectric encoder, wherein a plurality of light receiving elements are arranged at the same phase position and at least two light receiving elements are adjacent to each other, and the plurality of light receiving elements having the same phase constitute one light receiving element group. 2. The plurality of light receiving element groups have a predetermined phase difference, and the area centroids on the respective phase axes of the plurality of light receiving element groups having a predetermined phase difference with each other are matched. 2. The photoelectric encoder according to 1. The plurality of light receiving element groups have a predetermined phase difference, and the area centroids on the respective phase axes of the plurality of light receiving element groups having a predetermined phase difference with respect to each other are set to the central axis of the radiated light from the light source. 2. The photoelectric encoder according to claim 1, wherein the photoelectric encoder is arranged symmetrically with respect to the axis. In the plurality of light receiving element groups, a center distance between adjacent light receiving elements having the same phase is the pitch P, and a center distance between light receiving elements at ends of adjacent light receiving element groups having different phases is 5P / 4. Item 2. The photoelectric encoder according to Item 1. The photoelectric encoder according to any one of claims 1 to 4, wherein the plurality of light receiving element groups have an integrated crosstalk prevention unit provided between adjacent light receiving elements. The photoelectric encoder according to claim 5, wherein the crosstalk prevention unit is a deposited film member. The photoelectric encoder according to claim 5, wherein the crosstalk prevention unit is a signal light blocking member formed by etching. There are four light receiving element groups, corresponding to four-phase signals, and arranged such that when one phase is used as a reference, the phases of other signals are 90 °, 180 °, and 270 °. Item 6. The photoelectric encoder according to any one of Items 1 to 5. The photoelectric encoder according to claim 1, wherein a width of each of the light receiving elements is approximately の of the predetermined pitch (P).

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