JP2001289674A - Displacement measuring device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a displacement-measuring device capable of improving reliability and yield in the case of a fine scale pitch. SOLUTION: In accordance with the pitch λ of an optical grating 12 of a scale 1, the light receiving elements PD1 and PD2 of a light receiving element array 22 are constituted of a plurality of stripe patterns 32 arranged with the pitch λ and connection parts 33 connecting between them.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a displacement measuring device comprising a scale which is arranged so as to be relatively movable and outputs a displacement signal, and a receiving element array.

[0002]

2. Description of the Related Art Conventionally, a photoelectric encoder using a light receiving element array also serving as an index grating on a light receiving side has been known. When the optical grating pitch of the scale is λ,
For example, in the case of obtaining displacement signals of four phases, the light receiving element array is configured by arranging light receiving elements at a pitch of 3λ / 4. In this case, the light receiving elements of the same phase in the light receiving element array are connected in parallel, and four-phase outputs of A, BB, B, and AB are obtained.

[0003]

When a photoelectric encoder having a fine pitch is manufactured, the arrangement pitch of the light receiving element array becomes fine. As a result of this miniaturization, for example, if there is dust adhesion or etching residue in the space of the adjacent light receiving element,
An accident occurs in which adjacent light receiving elements are short-circuited or leak increases. Since adjacent light receiving elements are used to output displacement signals of different phases, such a short circuit or leak causes reliability and yield reduction of the photoelectric encoder. In addition, when the width of the light receiving element is small, the wiring contact with the light receiving element becomes insufficient, which also causes a reduction in reliability.

The present invention has been made in view of the above circumstances, and has as its object to provide a displacement measuring device capable of improving reliability and yield in the case of fine scale pitch.

[0005]

According to the present invention, there is provided a scale in which a scale grating having a pitch λ is formed along a measurement axis;
A receiving element array that is disposed so as to be relatively movable along the measurement axis with respect to the scale and that detects the scale grating and outputs a plurality of displacement signals having different phases. The array includes a substrate, a plurality of stripe pattern portions formed on the substrate and arranged along the measurement axis at a pitch nλ (where n is a positive integer), and the stripe pattern portions. And a plurality of receiving elements that output a displacement signal having a different phase with a coupling unit that couples the signals.

In the present invention, one receiving element is composed of a plurality of stripe pattern portions having the same pitch as the pitch of the scale or an integer multiple thereof, and a connecting portion connecting these. In other words, in the present invention, one receiving element is configured such that a plurality of in-phase receiving elements in a normal receiving element array are integrated into one. With such a configuration, even if dust or etching residue exists between adjacent stripe pattern portions in one receiving element and a short circuit or leak occurs, the adjacent stripe pattern portions are used for in-phase output. Therefore, the displacement output signal is not affected at all. Therefore, the reliability and yield of the fine pitch encoder can be improved. Further, in the present invention, it is assumed that each receiving element has a receiving surface that is continuous from the stripe pattern portion to the connecting portion, and if the connecting portion is a wiring contact portion, even if the stripe pattern portion is thin, it can be surely formed. Contact can be made.

The present invention is applied to, for example, an optical encoder. In this case, the scale grating is an optical grating,
The receiving element array is constituted by a light receiving element array. In this case, the plurality of light receiving elements are, for example, Δn + (2M−1)
/ 2｝ λ (where M is a positive integer) having two light receiving elements which are arranged in the measurement axis direction at an arrangement pitch and output two-phase displacement signals of mutually opposite phases. Can be. Alternatively, the plurality of light receiving elements are Δn + (2M
-1) / 4) 4 arranged at an arrangement pitch of λ (where M is a positive integer) in the measurement axis direction and having a phase difference of 90 °.
One set of four light receiving elements that output a phase displacement signal can be provided. Further, the plurality of light receiving elements are arranged in the measurement axis direction at an arrangement pitch of (n + N / 3) λ (where N is a positive integer excluding a multiple of 3).
A set of three light receiving elements that output displacement signals of three phases different in phase by 0 ° can be provided.

Further, in the present invention, the connecting portion of one light receiving element may be connected between (a) the central portion of the stripe pattern portion and (b) connected between the end portions of the stripe pattern portion. Or (c) connecting at a plurality of locations in the stripe pattern portion.

The present invention is also applicable to a magnetic encoder and a capacitive encoder. In the former case, the scale grating is a magnetic scale that generates a periodic magnetic field having a pitch λ, and the receiving element array is configured by a magnetic detecting element array. In the latter case, the scale grating is constituted by a transfer electrode array, and the sensor head is constituted by a transmission electrode capacitively coupled to the transfer electrode and a reception electrode array as a reception element array.

[0010]

1 and 2 show the basic structure of a photoelectric encoder to which the present invention is applied. Each of them includes a scale 1 and a sensor head 2 which moves relative to the scale 1 in the measurement axis x direction and outputs a displacement signal. FIG. 1 shows a transmission encoder, and FIG. 2 shows a reflection encoder. That is, in FIG. 1, the scale 1 has a transparent substrate 11 on which a transmission type optical grating 12 in which transmission parts and non-transmission parts are arranged is formed. In FIG. 2, the scale has a reflective optical grating 12 in which a reflective portion and a non-reflective portion are arranged on a substrate 11.

The sensor head 2 includes a light source 21 such as an LED, an index grating 23, and a light receiving element array 22 that receives light from the scale 1. The light receiving element array 22 arranges a plurality of light receiving elements at a predetermined pitch in relation to the optical grating pitch of the scale 1,
It is configured to obtain displacement signals of a plurality of phases.

[First Embodiment] FIG. 3 shows the relationship between the scale 1 and the light receiving element array 22 which can be applied to either of the formats shown in FIGS. Optical grating 12 of scale 1
Is configured by alternately arranging transmission parts (or reflection parts) 12a and non-transmission parts (or non-reflection parts) 12b along the measurement axis x, and the pitch is λ. The light receiving element array 22 includes a substrate 31 and two light receiving elements PD1 and PD1 formed thereon.
PD2. Light receiving elements PD1, PD2
Respectively have the same pitch S as the optical grating 12 of the scale 1
It is composed of three stripe pattern portions 32 arranged in the measurement axis x direction at 1 = λ, and a connecting portion 33 connecting these.

The relative positional relationship between the light receiving elements PD1 and PD2 is determined by the stripe pattern portion 32 of one of the light receiving elements PD1.
Is the transmission part (or reflection part) 1 of the optical grating 12 of the scale 1
When overlapping with 2a, the stripe pattern portion 32 of the other light receiving element PD2 is set to overlap with the non-transmissive portion (or non-reflective portion) 12b of the optical grating 12 of the scale 1. That is, the arrangement pitch of the light receiving elements PD1 and PD2 is P
1 = 3λ + λ / 2, and these light receiving elements PD
1 and PD2 are adapted to obtain A and B phase displacement output signals of opposite phases.

In FIG. 3, two light receiving elements PD1, PD2
Although only the two light receiving elements are shown,
As a set, a plurality of sets of light receiving elements are arranged. Further, in the case of the embodiment of FIG. 3, the light receiving elements PD1, PD2
Shows an example in which three stripe pattern portions 32 are provided, but in general, it is sufficient if there are two or more stripe pattern portions. That is, the pitch of the stripe pattern portions 32 of the light receiving elements PD1 and PD2 is generally S1 = nλ.
(N: positive integer). Also, the light receiving elements PD1,
The pitch S2 of the adjacent stripe pattern portions 32 between the PD2s is S2 = 3λ / 2 in the case of the drawing. However, as a condition for securing a necessary space and obtaining a reverse-phase output, generally, S2 = 3λ / 2. It is sufficient that {(2M-1) / 2} λ (M: a positive integer).

From the above, the arrangement pitch P1 of the light receiving elements PD1, PD2 is generally {n + (2M-1) / 2} λ
And it is sufficient. In FIG. 3, the terminal wiring of the light receiving elements PD1 and PD2 is omitted. FIG. 4 shows a specific example of the structure of the light receiving elements PD1 and PD2 including this terminal wiring. FIG. 4A is a plan view, and FIGS. 4B and 4C are sectional views taken along lines II ′ and II-II ′ of FIG. 4A, respectively.

The light receiving elements PD1 and PD2 are photodiodes formed by patterning p-type, i-type, and n-type amorphous silicon layers 321, 322, and 323 deposited on a substrate 31 such as glass. This photodiode has one light receiving surface which is continuous with the stripe pattern portion 32 and a connecting portion 33 connected at the center thereof. A common electrode 311 is previously formed on the substrate surface. The light receiving elements PD1 and PD2 are covered with an insulating film 312 such as a CVD oxide film, and a contact hole 314 is formed in the insulating film 312 to form a wiring 313. In this embodiment, the contact hole 314 of the wiring 313 is formed in the connecting portion 33 that connects the plurality of stripe pattern portions 32 of the light receiving elements PD1 and PD2 at the center thereof.

As described above, in this embodiment, one light receiving element is constituted by integrally integrating a plurality of in-phase light receiving elements in a light receiving element array in a normal photoelectric encoder. In this case, even if dust or the like enters between the stripe pattern portions 32 in the light receiving element or there is an etching residue, the displacement output signal is not affected. In the case of this embodiment, the problem of dust etc. is
This is a space between the light receiving elements PD1 and PD2, but this space is only one place when one set of light receiving elements is provided. In the case of FIG. 3, the space between the light receiving elements PD1 and PD2 is set to λ, which is larger than the space λ / 2 of the stripe pattern portion 32 in each light receiving element.

Therefore, according to this embodiment, even if the scale pitch λ becomes fine, a decrease in yield and a decrease in reliability due to dust and the like are suppressed, and crosstalk noise between displacement output signals having different phases is also suppressed. . Further, by forming a wiring contact at the connection portion, a wiring contact having a low resistance can be obtained even when the scale pitch λ becomes finer.

[Second Embodiment] FIG. 5A shows a layout of light receiving elements PD1 and PD2 according to another embodiment. Parts corresponding to those in the above embodiment are denoted by the same reference numerals as in the above embodiment, and detailed description is omitted. The dimensions of each part of the light receiving elements PD1 and PD2 are the same as in the previous embodiment. In this embodiment, a connecting portion 33 connecting the stripe pattern portions 32 of the light receiving elements PD1 and PD2 is arranged at an end of the stripe pattern portion 32, and this is used as a wiring contact portion. By doing so, the signal delay in the light receiving elements PD1 and PD2 is larger than in the previous embodiment. However, since the wiring is drawn out only from the end, the restriction on the width of the wiring is relaxed. Becomes easier. FIG. 5B is a layout in which connecting portions 33 are arranged at both ends of the light receiving elements PD1 and PD2 in FIG. 5A.

[Embodiment 3] FIG. 6A shows a layout of light receiving elements PD1 and PD2 according to still another embodiment. Parts corresponding to those in the above embodiment are denoted by the same reference numerals as in the above embodiment, and detailed description is omitted. The dimensions of each part of the light receiving elements PD1 and PD2 are the same as in the previous embodiment. In this embodiment, the light receiving elements PD1, PD
Connecting portion 33 connecting the two stripe pattern portions 32
Are provided at a plurality of locations in the stripe pattern portion 32, and this is used as a wiring contact portion. According to this embodiment, it is possible to reduce the influence of signal delay in the light receiving elements PD1 and PD2. FIG. 6B shows the light receiving element PD of FIG. 6A.
1, a layout in which connecting portions 33 are arranged at both ends of PD1.

[Embodiment 4] In the embodiments described above, the case where two-phase displacement output is obtained has been described. However, the present invention can be similarly applied to an encoder which obtains four-phase displacement output. FIG. 7 shows a four-phase light receiving element PD according to such an embodiment.
1 shows a layout of 1 to PD4. The configuration of each light receiving element is the same as the embodiment of FIG. In the case of this embodiment, four light receiving elements PD1 to PD4 are arranged at an arrangement pitch P2 = 3λ + λ / 4 in the measurement axis direction. As a result, from each of the light receiving elements PD1 to PD4, 90
It is possible to obtain displacement outputs of the A, AB, B, and BB phases whose phases are shifted by °.

As described in the embodiment of FIG. 3, at least two stripe pattern portions 32 of one light receiving element are required. Further, when the interval between the stripe pattern portions 32 of adjacent light receiving elements is secured by (2M−1) λ / 4 (where M is a positive integer), the light receiving element array pitch P2 in this embodiment is generally Specifically, P2
= {N + (2M-1) / 4} λ.

According to this embodiment, the same effect as in the previous embodiment can be obtained. 5A, 5B, 6A, or 6B as the layout of the light receiving elements PD1 to PD4.
The above method can also be applied. In FIG. 7, one set of four light receiving elements PD1 to PD4 is shown, but a plurality of sets of light receiving elements may be used.

[Embodiment 5] FIG. 8 shows an embodiment applied to an encoder for obtaining a three-phase displacement output signal.
The layout of the three-phase light receiving elements PD1 to PD3 is shown. The configuration of each light receiving element is the same as the embodiment of FIG. In the case of this embodiment, three light receiving elements P
D1 to PD3 are arranged in the measurement axis direction at an arrangement pitch P3 = 3λ +
They are arranged at λ / 3. Thereby, each light receiving element PD1
変 位 PD3, it is possible to obtain displacement outputs of the A, B, and C phases whose phases are shifted by 120 °.

As described in the embodiment of FIG. 3, at least two stripe pattern portions 32 of one light receiving element are required. The interval between the stripe pattern portions 32 of the adjacent light receiving elements is set to Nλ / 3 (where N is 3
(Positive integer excluding a multiple of the following), the light receiving element array pitch P3 in this embodiment is generally
P3 = (n + N / 3) λ. According to this embodiment, the same effect as that of the previous embodiment can be obtained. FIGS. 5A and 5B show the layout of the light receiving elements PD1 to PD3.
B, FIG. 6A or the method of FIG. 6B can also be applied. In FIG. 8, one set of three light receiving elements PD1 to PD1 is provided.
Although the PD 3 is shown, a plurality of sets of light receiving elements can be used.

In the above embodiments, the light receiving element is described as a photodiode using an amorphous silicon film. However, the present invention can be similarly applied to a photodiode formed on a single crystal silicon substrate.

[Embodiment 6] FIG. 9 shows an embodiment in which the present invention is applied to a magnetic encoder. The provision of the scale 1 and the sensor head 2 opposed to the scale 1 is the same as in the above embodiments. Scale 1 has S pole and N
The poles are arranged at a pitch λ along the measurement axis x to form a magnetic grating and generate a periodic magnetic field. The sensor head 2 is
A magnetic resistance element 42 is arranged on a substrate 41 as a magnetic detection element for detecting a magnetic field of the scale 1.

One magnetoresistive element 42 has a plurality of (two in the figure) stripe pattern portions 43 arranged at an interval of λ and a connecting portion 44 connecting these. In the case of the drawing, such a magnetoresistive element 42 has P = 2λ + λ / 4.
Are arranged as one set at a pitch of .times., And output four-phase displacement signals of A, B, AB, and BB, respectively. In general, the interval between the stripe pattern portions of one magnetoresistive element can be nλ (n is a positive integer).

Also in this embodiment, as the scale pitch becomes finer, the magnetoresistive elements arranged in different phases are rearranged in the same manner as in the previous embodiment, so that the same effect as in the previous embodiment is obtained. Is obtained. Note that the magnetic encoder also has an induction type that detects an induction magnetic field from a scale. In this case, a coil or the like is used as a magnetic detection element, but the present invention can be applied to this induction type magnetic encoder as well. .

[Embodiment 7] FIG. 10 shows an embodiment in which the present invention is applied to a capacitance type encoder. The provision of the scale 1 and the sensor head 2 opposed thereto is the same as in the previous embodiment. Transfer electrodes 51 are arranged at a predetermined pitch on the scale 1, and the sensor head 2 has a reception electrode group 52 and a transmission electrode 53 that are capacitively coupled to the transfer electrodes 51. The receiving electrode group 52 has phase information by its physical arrangement.

In a normal case, the receiving electrode group 52
For example, as shown in FIG. 11A, A, B,
The three-phase receiving electrodes C are arranged, and the same-phase receiving electrodes receive signals of the same phase. On the other hand, in this embodiment, as shown in FIG.
The receiving electrodes 55 in which two receiving electrodes of the same phase of A are combined into one are arranged at an arrangement pitch of λ + 2λ / 3,
A, B, and C phase receiving elements. Each receiving electrode 55 is composed of a stripe pattern portion 53 with an interval λ and a connecting portion 54 connecting the stripe pattern portions 53, as in the light receiving element of the first embodiment, for example. Alternatively, as shown in FIG. 11C, the receiving electrodes 55 are arranged at an arrangement pitch of λ + 4λ / 3 to form A, B, and C phase receiving elements. Further, FIG.
As shown by the broken line in FIG. 7, the receiving electrodes 55 can be arranged at an arrangement pitch of λ + λ / 3 to form A, B, and C phase receiving elements.

Further, the receiving electrode arrangement of FIG.
As shown in A, two receiving electrodes of the same phase can be rearranged so as to be adjacent to each other. In this case, 2
The receiving electrodes of each book are put together to form a stripe pattern section 5.
When one receiving electrode 55 composed of 3 and the connecting portion 54 is obtained,
As shown in FIG. 12B. This is the same as FIG. 11B. Also in this embodiment, when the scale pitch is miniaturized, a margin is provided in the receiving electrode arrangement, and short-circuiting of the receiving electrodes of different phases due to dust or the like can be prevented, so that the reliability can be improved.

As shown in FIG. 11B or FIG. 12B, the case where the receiving electrodes 55 are arranged at an interval of 2λ / 3, and FIG.
As shown by the solid line in C, when comparing the case where the receiving electrodes 55 are arranged at intervals of 4λ / 3, the configuration of FIG. 11C has a large averaging effect, but the area of one set of receiving elements is large. On the other hand, in FIG. 11B, the receiving element area can be reduced. In this embodiment, the case where a three-phase displacement signal having a phase difference of 120 ° is output has been described. However, a capacitance type which obtains a displacement output of four phases having a 90 ° phase difference or two phases having a 180 ° phase difference has been described. The same applies to encoders.

[0034]

As described above, according to the present invention, it is possible to provide a displacement measuring apparatus capable of improving reliability and yield in the case of fine scale pitch.

[Brief description of the drawings]

FIG. 1 is a diagram illustrating a configuration example of a photoelectric encoder to which the present invention is applied.

FIG. 2 is a diagram showing another configuration example of a photoelectric encoder to which the present invention is applied.

FIG. 3 is a diagram showing a relationship between a scale and a light receiving element according to the first embodiment of the present invention.

FIG. 4A is a diagram showing a structure of a light receiving element according to the first embodiment.

FIG. 4B is a sectional view taken along the line I-I 'of FIG. 4A.

FIG. 4C is a sectional view taken along the line II-II ′ of FIG. 4A.

FIG. 5A is a diagram showing a layout of a light receiving element according to a second embodiment.

FIG. 5B is a diagram showing a layout obtained by modifying the layout of FIG. 5A.

FIG. 6A is a diagram showing a layout of a light receiving element according to a third embodiment.

FIG. 6B is a diagram showing a layout obtained by modifying the layout of FIG. 6A.

FIG. 7 is a diagram showing a layout of a light receiving element according to a fourth embodiment.

FIG. 8 is a diagram showing a layout of a light receiving element according to a fifth embodiment.

FIG. 9 is a diagram showing a configuration of a magnetic encoder according to a sixth embodiment.

FIG. 10 is a diagram showing a configuration of a capacitive encoder according to a seventh embodiment.

FIG. 11A is a diagram showing a configuration of a conventional transmission electrode group.

11B is a diagram showing a configuration of a transmission electrode group according to the embodiment shown in comparison with FIG. 11A.

FIG. 11C is a diagram showing another configuration of the transmission electrode group.

FIG. 12A is a diagram showing another configuration of a conventional transmission electrode group.

FIG. 12B is a diagram showing a configuration of a transmission electrode group according to the embodiment shown in comparison with FIG. 12A.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Scale, 2 ... Sensor head, 22 ... Light receiving element array, PD1, PD2, PD3, PD4 ... Light receiving element, 31
... board, 32 ... stripe pattern part, 33 ... connecting part,
313: wiring, 314: contact hole.

Claims (11)

[Claims] 1. A scale on which a scale grating having a pitch λ is formed along a measurement axis, and a scale arranged so as to be relatively movable with respect to the scale along the measurement axis. In a displacement measuring apparatus having a receiving element array that outputs a plurality of different displacement signals, the receiving element array is formed on a substrate and has a pitch nλ (where n
Are positive integers), and a plurality of receiving elements that output displacement signals of different phases, including a plurality of stripe pattern portions arranged along the measurement axis and a connecting portion connecting these stripe pattern portions to each other. And a displacement measuring device. 2. The displacement measuring device according to claim 1, wherein the scale grating is an optical grating, and the receiving element array is a light receiving element array in which a plurality of light receiving elements are arranged. 3. The method according to claim 2, wherein the plurality of light receiving elements are Δn + (2M−
1) A set of two light receiving elements which are arranged in the direction of the measuring axis at an arrangement pitch of / 2｝ λ (where n and M are positive integers) and output displacement signals having phases opposite to each other is provided. The displacement measuring device according to claim 2, wherein 4. The method according to claim 1, wherein the plurality of light receiving elements are Δn + (2M−
1) One set of four light-receiving elements that are arranged in the measurement axis direction at an arrangement pitch of / 4 ／ λ (where n and M are positive integers) and output four-phase displacement signals that differ in phase by 90 °. 3. The displacement measuring device according to claim 2, further comprising an element. 5. The method according to claim 1, wherein the plurality of light receiving elements are (n + N / 3)
λ (where n is a positive integer, N is a positive integer excluding a multiple of 3) is arranged in the measurement axis direction at an arrangement pitch of 120.
Output three phase displacement signals with different phases by 1 °
3. The displacement measuring device according to claim 2, further comprising a set of light receiving elements. 6. The displacement measuring apparatus according to claim 2, wherein each of the light receiving elements has a light receiving surface continuous from the stripe pattern portion to a connecting portion, and the connecting portion is a wiring contact portion. . 7. The displacement measuring apparatus according to claim 2, wherein each of said light receiving elements has a plurality of stripe pattern portions and a connecting portion connecting between central portions of these stripe pattern portions. 8. The displacement measuring apparatus according to claim 2, wherein each of the light receiving elements has a plurality of stripe pattern portions and a connecting portion connecting at least one end of the stripe pattern portions. . 9. The displacement measuring device according to claim 2, wherein each of the light receiving elements has a plurality of stripe pattern portions and a connecting portion connecting the stripe pattern portions at a plurality of positions. 10. The scale grating is a magnetic scale grating that generates a periodic magnetic field having a pitch λ along a measurement axis, and the receiving element detects a magnetic field of the scale and has a different phase as the scale moves. The displacement measuring device according to claim 1, wherein the displacement measuring device is a magnetic detection element array that outputs a plurality of displacement signals. 11. The sensor according to claim 11, wherein the scale grating is a transfer electrode array, and the sensor head has a transmission electrode capacitively coupled to the transfer electrode array and a reception electrode array serving as the reception element array. 2. The displacement measuring device according to 1.