JP4880132B2 - Photoelectric encoder - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a photoelectric encoder used for a linear scale or the like.
[0002]
[Prior art]
Conventionally, a three-grid linear encoder is known as a photoelectric encoder. In addition to the scale grating, the three-grating linear encoder has a first index grating on the light source side and a second index grating on the light receiving side. Light from the light source is modulated by the first index grating and applied to the scale grating, and light from the scale grating is modulated by the second index grating and received by the light receiving element. If the scale grating is reflective, the first and second index gratings are arranged on the same side with respect to the scale. Therefore, the first and second index gratings are formed on the same transparent substrate, the light emitting element is mounted on the first index grating of the transparent substrate, and the light receiving element is mounted on the second index grating. An example in which a small linear scale is configured by configuring a sensor module is also known (Japanese Patent Laid-Open No. 2000-321096). In recent years, the precision and miniaturization of equipment has progressed, and the demand for miniaturization of the encoder itself is high. The scale and the sensor head are manufactured as separate parts. In particular, the size of the sensor head greatly affects the determination of the size of the entire photoelectric encoder.
[0003]
[Problems to be solved by the invention]
However, in the conventional photoelectric encoder, the sensor head could be downsized to some extent by modularization, but the sensor head must be equipped with a light source and a light receiving element separately from the two index gratings. There is a limit to downsizing the sensor head, and it is difficult to downsize the encoder.
The present invention has been made in view of the above circumstances, and provides a photoelectric encoder in which the sensor head can be made smaller and thinner than before by integrating the light receiving portion and the light emitting portion of the sensor head. The purpose is to do.
[0004]
[Means for Solving the Problems]
A photoelectric encoder according to the present invention includes a scale and a sensor head that are arranged to face each other and move relative to each other in a measurement axis direction, and the scale is a reflection type along the measurement axis direction on a surface facing the sensor. The sensor head is mounted on the sensor substrate to irradiate the scale grating with light, and is arranged at a predetermined pitch and itself is the first grid. A plurality of light emitting elements constituting an index grating, and mounted on the sensor substrate to receive light reflected from the scale grating irradiated from the plurality of light emitting elements and arranged at a predetermined pitch And a plurality of light receiving elements constituting the second index grating.
[0005]
According to the present invention, the sensor head has a plurality of light emitting elements and a plurality of light receiving elements arranged on the sensor substrate at a predetermined pitch, and the light emitting elements and the light receiving elements themselves have the first and second index gratings, respectively. Since the sensor head is formed, the sensor head can be made extremely thin and small as compared with the conventional type in which the light emitting element and the light receiving element are mounted on the index grating. The size and thickness can be reduced.
[0006]
In particular, when the plurality of light-emitting elements and light-receiving elements are mounted on the same surface of the sensor substrate, the light-emitting elements and the light-receiving elements can be manufactured by a series of stacking processes on the sensor substrate, thereby reducing manufacturing costs. Can be achieved.
[0007]
In addition, when the light emitting elements are respectively arranged between a plurality of light receiving elements on the sensor substrate, the light emitting elements and the light receiving elements are efficiently arranged in a common area as compared with the case where they are formed in different areas. Therefore, the sensor head can be further downsized.
[0008]
As the sensor substrate, a transparent substrate such as a glass substrate can be used. In this case, it is desirable that the light emitting element and the light receiving element are mounted on the transparent substrate via a transparent electrode. When both the light emitting element and the light receiving element are mounted on the side of the transparent substrate not facing the scale via the transparent electrode, the scale grid of the scale is irradiated with light via the transparent electrode and the transparent substrate. Become. In this case, since no element is formed on the surface of the transparent substrate facing the scale, there is an advantage that the optical gap between the sensor head and the scale can be set accurately and the sensor is protected. When there is no fear of sensor damage, both the light emitting element and the light receiving element may be mounted on the surface facing the scale. In this case, unnecessary light of the reflected light from the scale can be prevented from passing through the transparent substrate and received by the light receiving element. As the light-emitting element, for example, an electroluminescence (EL) element that does not select a base material can be used.
[0009]
In the case of such a configuration, the sensor head includes, for example, a step of forming a transparent electrode on a transparent substrate, a step of arranging the plurality of light receiving elements on the transparent electrode at a predetermined pitch, It can be manufactured by a step of forming a protective layer covering each of them, and a step of arranging the light emitting elements on the transparent electrode at a predetermined pitch.
[0010]
A semiconductor substrate can also be used as the sensor substrate. In this case, the light emitting element and the light receiving element can be formed directly on the surface of the semiconductor substrate facing the scale. As the light-emitting element, a light-emitting diode, an EL element, or the like can be used.
[0011]
A flexible material can also be used as the sensor substrate. By using such a flexible material as the substrate, it is possible to reduce the restrictions on the mounting of the sensor head and to realize a sensor head with a low risk of damage due to external force.
[0012]
The light emitting element desirably emits blue light. By using a light-emitting element that emits blue light with a short wavelength, the pitch of the grating can be made finer, and a photoelectric encoder having a high-accuracy sensor head can be realized with a high response speed. .
[0013]
DETAILED DESCRIPTION OF THE INVENTION
FIG. 1 is a perspective view showing a schematic configuration of a photoelectric encoder according to the present invention.
This photoelectric encoder is composed of a scale 10 and a sensor head 20 which are opposed to each other with a predetermined optical gap and are movable relative to each other in the measurement axis x direction.
The scale 10 is formed by forming scale gratings 12 at a predetermined pitch on a scale substrate 11 extending in the measurement axis x direction. The sensor head 20 is formed by alternately arranging light emitting elements 22 and photodiodes 23 facing the scale grating 12 on the sensor substrate 21 at a predetermined pitch. Note that the photodiode 23 actually has a phase relationship that is 90 ° out of phase with each other, and an A phase light receiving element and a B phase light receiving element with an opposite phase (180 ° phase difference), and a / A phase light receiving element ( However, “/” indicates negative) and a / B phase light receiving element.
[0014]
2 is an enlarged cross-sectional view taken along line AA ′ of FIG. In this example, the sensor substrate 21 is a transparent substrate formed of a glass substrate. A transparent conductive film 26 serving as a common lower electrode is formed on the surface of the sensor substrate 21 that does not face the scale 10. On the transparent conductive film 26, a p-type amorphous semiconductor layer 23a, an i-type amorphous semiconductor layer 23b, and an n-type amorphous semiconductor layer 23c are sequentially deposited, and a plurality of photos separated from each other by patterning these stacked films. Diodes 23 are arranged at a predetermined pitch along the measurement axis. On each photodiode 23, a wiring layer 27 made of a conductor such as Al serving as a cathode-side electrode is formed. The upper and side surfaces of the photodiode 23 on which the wiring layer 27 is formed are covered with a protective film 28 made of an insulating material of SiO2. The wiring layer 27 connects the photodiodes 23 of the in-phase group to each other through a contact hole (not shown) opened in the protective film 28.
On the other hand, the plurality of light emitting elements 22 are respectively disposed between the adjacent photodiodes 23 via the protective film 28 so as to project light in the direction of the scale 10. A wiring layer 29 made of a conductor such as Al is formed above the plurality of light emitting elements 22 and the protective film 28. Specifically, for example, an organic EL having a relatively strong emission intensity can be used as the light emitting element 22, and it is particularly preferable to use an element that emits blue light.
[0015]
As the transparent conductive film 26, for example, ITO, SnO2, ZnO or the like can be used. Si is an amorphous semiconductor. Furthermore, CdS / CdTe or the like can be used as a light receiving element as a polycrystalline material that can be produced on glass. The photodiode structure may be a pn structure in addition to the pin structure.
[0016]
In the case of the photoelectric encoder according to this embodiment, since the light emitting elements 22 are arranged in a lattice pattern, the light emitted from the light emitting elements 22 is the same as when the light passes through the first index grating as the first grating. It is in a state. Light from the light emitting element 22 is irradiated in the direction of the scale 10 and reflected by the scale grating 12 as the second grating formed on the scale 10. The light reflected from the scale grating 12 and transmitted through the sensor substrate 21 is received by a photodiode 23 having the role of a second index grating as a third grating that is also arranged in a lattice pattern, A relative displacement in the measurement axis x direction between the head 20 and the scale 10 is detected. In this way, it functions as a three-grid photoelectric encoder.
[0017]
As described above, according to the photoelectric encoder according to the present embodiment, since the light receiving unit and the light emitting unit of the sensor head 20 are integrated on the same substrate, the sensor head is made smaller and thinner than the conventional one. be able to. In addition, since the light receiving element and the light emitting element are arranged on the surface side that does not face the scale of the sensor substrate, the sensor substrate serves as a cover that protects these elements from dust and shocks, and the measurement accuracy of the encoder is reliable. It is possible to improve the performance.
[0018]
Further, in this embodiment, since a glass substrate that is an insulator is employed as the sensor substrate, the possibility of crosstalk, leakage, and the like can be reduced. Furthermore, since the light emitting element is directly disposed on the transparent conductive film, there is an effect that an electrical connection failure or the like hardly occurs.
[0019]
Blue light has a characteristic that the resolution of light is high because its wavelength is shorter than infrared light, red light, and the like. Therefore, by using a light emitting element that emits blue light, the pitch of the grating can be made finer, and a high-accuracy photoelectric encoder with a high response speed can be realized.
In this embodiment, an organic EL is used as the light emitting element. However, as the other light emitting element, an inorganic EL or the like that can be manufactured without selecting a base as in the organic EL may be used.
[0020]
FIG. 3 is a sectional view showing a sensor head portion of the second embodiment of the photoelectric encoder according to the present invention. This embodiment is an application of the above-described first embodiment.
The photoelectric encoder according to this embodiment is different from the first embodiment described above in the wiring method of the light emitting element 22 and the protective film in the sensor head.
That is, in the sensor head 40 according to the present embodiment, first, the transparent conductive film 26, the photodiode 23, and the wiring layer 27 are formed on the sensor substrate 21 in the same manner as in the first embodiment described above. A protective film 41 made of a transparent insulating material such as SiN is formed. Further, if SOG (spin-on-glass material) is used as the protective film, the surface can be formed flat.
Thereafter, a contact hole penetrating to the transparent conductive film 26 is formed in the protective film 41 between the adjacent photodiodes 23, and a transparent conductive film wiring 42 made of ITO, SnO2, ZnO or the like is formed in the contact hole.
Subsequently, the plurality of light emitting elements 22 are respectively disposed on the transparent conductive film wirings 42 between the adjacent photodiodes 23. With this arrangement, the light emitting element 22 and the transparent conductive film 26 are electrically connected via the transparent conductive film wiring 42 penetrating the contact hole. Finally, the wiring layer 29, which is also made of a conductor such as Al, is patterned from above so as to ensure conduction with the light emitting element 22.
[0021]
FIG. 4 is a cross-sectional view showing a sensor head portion of a photoelectric encoder according to a third embodiment of the present invention. This embodiment is an application of the above-described second embodiment.
The photoelectric encoder according to this embodiment is different from the above-described second embodiment in the wiring portion of the light emitting element 22.
That is, in the sensor head 50 according to the present embodiment, the transparent conductive film wiring 42 on the lower side of the light emitting element 22 is electrically connected to a portion other than the transparent conductive film 26 to supply power to the light emitting element 22.
[0022]
FIG. 5 is a sectional view showing a sensor head portion of a fourth embodiment of the photoelectric encoder according to the present invention. This embodiment is an application of the above-described third embodiment.
The photoelectric encoder according to this embodiment is different from the above-described third embodiment in the wiring in the sensor head.
That is, in the sensor head 60 in the present embodiment, the wiring layer 61 made of a conductor such as Al is formed between the protective films 41, and the transparent conductive film wiring 8 in which the light emitting element 22 and the wiring layer 61 pass through the contact holes. 'Electrically connected through. At this time, the wiring layer 61 can be formed of a transparent conductive film or a conductor such as Al that does not transmit light. For this reason, the light emitting element 22 can project light in the direction of the scale lattice 12 while avoiding the wiring pattern of the wiring layer 61 by shifting the light emitting element 22 and the wiring layer 61 in a direction perpendicular to the drawing sheet. Are arranged as follows.
[0023]
FIG. 6 is a sectional view showing a sensor head portion of a fifth embodiment of the photoelectric encoder according to the present invention. This embodiment is an application of the above-described first embodiment. The photoelectric encoder according to this embodiment is different from the first embodiment described above in the positional relationship between the light emitting element and the light receiving element in the sensor head and the protective film.
That is, in the sensor head 70 in this embodiment, first, the transparent conductive film 26 that becomes the common lower electrode is formed on the surface side of the sensor substrate 21 that does not face the scale 10. On the transparent conductive film 26, a plurality of light emitting elements 22 are arranged at a predetermined pitch along the measurement axis. Next, the wiring layer 8 made of a conductor such as Al is formed on the light emitting elements 22. Subsequently, a protective film 5 made of a transparent insulating material such as SiO2, SiN, or SOG is formed thereon.
[0024]
Thereafter, a transparent conductive film 71 serving as a common lower electrode is formed on the protective film 5. On the transparent conductive film 71, a p-type amorphous semiconductor layer 23a, an i-type amorphous semiconductor layer 23b, an n-type amorphous semiconductor layer 23c and a wiring layer 27 are sequentially deposited, and these stacked films are separated from each other by patterning. A plurality of the photodiodes 23 are arranged at a predetermined pitch along the measurement axis. At this time, the photodiodes 23 are arrayed so as to be positioned between the plurality of light emitting elements 22. Then, the protective film 72 made of an insulating material such as SiO 2 is formed again on the photodiodes 23, whereby the sensor head 70 is completed.
According to this embodiment, in addition to the effects of the first embodiment described above, since the light emitting elements and the photodiodes are arranged in different layers, there is no interference between the photodiodes and the light emitting elements. Problems such as crosstalk are less likely to occur. That is, the arrangement pitch of the optical grating formed by the light receiving element and the light emitting element can be easily reduced, and a highly accurate photoelectric encoder can be easily realized.
[0025]
FIG. 7 is a sectional view showing a sensor head portion of a sixth embodiment of the photoelectric encoder according to the present invention. This embodiment is an application of the above-described first embodiment.
The photoelectric encoder according to this embodiment is different from the first embodiment described above in the arrangement of light emitting elements in the sensor head.
That is, the sensor head 80 according to the present embodiment is first formed of a transparent conductive film 26, a plurality of photodiodes 23, and a conductor such as Al serving as a cathode side electrode on the sensor substrate 21 as in the first embodiment. The wiring layers 27 are sequentially formed.
Subsequently, the transparent conductive film 81 is similarly formed on the lower surface side of the sensor substrate 21, that is, the surface side facing the scale (not shown). Thereafter, the light emitting element 22 is disposed on the lower surface of the transparent conductive film 81 so as to project light in a scale direction (not shown). At this time, the plurality of light emitting elements 22 are arrayed so as to be positioned between the plurality of photodiodes 23, respectively. Finally, the transparent conductive film wiring 42 made of ITO, SnO2, ZnO or the like is formed on the lower surface of the light emitting element 22, thereby completing the sensor head 80.
[0026]
According to the photoelectric encoder of this embodiment, since the light emitting element is arranged on the side of the substrate facing the scale, there is no interference between the light emitting element and the photodiode, and problems such as crosstalk also occur. Hard to do. That is, the arrangement pitch of the optical grating formed by the light receiving element and the light emitting element can be easily reduced. Therefore, in addition to the effect of the first embodiment described above, there is an effect that a highly accurate photoelectric encoder can be easily realized.
[0027]
FIG. 8 is a sectional view showing a sensor head portion of a seventh embodiment of the photoelectric encoder according to the present invention. This embodiment is an application of the above-described first embodiment.
In the sensor head 90 of the photoelectric encoder according to this embodiment, first, after forming the transparent conductive film 26 and the plurality of photodiodes 23 on the sensor substrate 21 as in the first embodiment, these photodiodes 23 are formed. A wiring layer 27 made of a conductor such as Al serving as a cathode side electrode is formed on the upper side.
Subsequently, the plurality of light emitting elements 22 are arranged along the measurement axis in a region where each photodiode 23 on the surface side where the photodiode 23 of the sensor substrate 21 is arranged, that is, the surface side not facing the scale (not shown) is not formed. Arrange each at a predetermined pitch.
[0028]
Finally, the oblique incidence type sensor head 90 is completed by forming the wiring layer 29 made of a conductor such as Al on the plurality of light emitting elements 22.
[0029]
9 and 10 are plan views of the photoelectric encoder according to this embodiment. 9 shows an example in which the light emitting element 22 and the photodiode 23 are arranged in the longitudinal direction of the scale 10, and FIG. 10 shows an example in which the light emitting element 22 and the photodiode 23 are arranged in the short direction of the scale 10. Show.
[0030]
According to the photoelectric encoder according to this embodiment, since the light emitting element is arranged in a region where the light receiving element on the surface side not facing the scale of the substrate is not formed, interference between the light emitting element and the photodiode, Problems such as crosstalk are unlikely to occur. That is, the arrangement pitch of the optical grating formed by the light receiving element and the light emitting element can be easily reduced. Therefore, in addition to the effect of the first embodiment described above, there is an effect that a highly accurate photoelectric encoder can be easily realized.
[0031]
Moreover, in each embodiment mentioned above, flexible materials, such as a flexible resin board | substrate, can also be employ | adopted as a sensor board | substrate as needed. By using a flexible material as a substrate, it is possible to reduce the restriction on the mounting position of the sensor head and the like, and to realize a sensor head with less risk of damage due to external force. Of course, by adopting a Si substrate or the like as the substrate, photodiodes or LEDs as light emitting elements can be directly formed on the Si substrate, and the thickness can be further reduced.
[0032]
【Effect of the invention】
As described above, according to the present invention, the sensor head has a plurality of light emitting elements and a plurality of light receiving elements arranged on the sensor substrate at a predetermined pitch, and the light emitting elements and the light receiving elements themselves are the first and first elements, respectively. Since the index grating of 2 is formed, the sensor head can be made extremely thin and small as compared with the conventional type in which the light emitting element and the light receiving element are mounted on the index grating. A photoelectric encoder capable of reducing the overall size and thickness of the photoelectric encoder can be provided.
[Brief description of the drawings]
FIG. 1 is a perspective view showing a schematic configuration of a photoelectric encoder according to the present invention.
FIG. 2 is an enlarged cross-sectional view taken along the line AA ′ of FIG.
FIG. 3 is a sectional view showing a sensor head portion of a second embodiment of the photoelectric encoder according to the present invention.
FIG. 4 is a sectional view showing a sensor head portion of a third embodiment of the photoelectric encoder according to the present invention.
FIG. 5 is a sectional view showing a sensor head portion of a fourth embodiment of the photoelectric encoder according to the present invention.
FIG. 6 is a sectional view showing a sensor head portion of a photoelectric encoder according to a fifth embodiment of the present invention.
FIG. 7 is a sectional view showing a sensor head portion of a sixth embodiment of a photoelectric encoder according to the present invention.
FIG. 8 is a sectional view showing a sensor head portion of a photoelectric encoder according to a seventh embodiment of the present invention.
FIG. 9 is a plan view of the sensor head.
FIG. 10 is a plan view of another configuration example of the sensor head.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 10 ... Scale, 11 ... Scale substrate, 12 ... Scale lattice, 20 ... Sensor head, 22 ... Sensor substrate, 22 ... Light emitting element, 23 ... Photodiode, 26 ... Transparent conductive film, 27, 29 ... Wiring layer, 30, 50 , 60, 70, 80, 90... Sensor head.

Claims (3)

A scale and a sensor head that are arranged opposite to each other and can move relative to each other in the measurement axis direction,
The scale is formed by forming a reflective scale grating along the measurement axis direction on the surface facing the sensor.
The sensor head is
A sensor substrate made of a glass substrate ;
A plurality of light-emitting elements composed of electroluminescence elements mounted on the sensor substrate and irradiating the scale grating with light, and arranged at a predetermined pitch and constituting the first index grating itself;
Mounted in a region where the first index grating by the plurality of light emitting elements on the sensor substrate is not formed, receives light reflected from the scale grating irradiated from the plurality of light emitting elements to the scale grating, A photoelectric encoder comprising: a plurality of light receiving elements which are arranged at a predetermined pitch and which themselves constitute the second index grating.   The photoelectric encoder according to claim 1, wherein the light emitting element and the light receiving element are mounted on the same surface of the sensor substrate. The sensor substrate is a transparent substrate,
The photoelectric encoder according to claim 1, wherein the light emitting element and the light receiving element are mounted on a surface of the transparent substrate opposite to the scale via a transparent electrode.

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