JP4244125B2 - Photoelectric encoder - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a photoelectric encoder, and more particularly to an improvement in the configuration of a light receiving and emitting unit of the photoelectric encoder.
[0002]
[Prior art]
Conventionally, photoelectric encoders that detect the displacement of two members that move relative to each other are used in various machine tools and measuring devices. This photoelectric encoder irradiates a light beam emitted from a light emitting element such as an LED toward a scale, receives a light beam transmitted, diffracted or reflected by the scale by a light receiving element such as a photodiode, and receives the light beam. The amount of displacement of the object is detected based on the state. Due to the demand for miniaturization of devices on which photoelectric encoders are mounted, there is a strong demand for miniaturization of photoelectric encoders.
[0003]
As a response to such a demand, a photoelectric encoder in which a light emitting element and a light receiving element are monolithically formed on the same integrated circuit substrate is known. However, in the case of such monolithic formation, there is a problem that the yield of the entire product is affected by both the yield of the light emitting elements and the yield of the light receiving elements, so that the yield rate is lowered, and as a result, the product becomes expensive. In the case of monolithic formation, since the light receiving / light emitting elements face each other in a bare state, the light receiving / emitting elements may be damaged if contacted by any chance.
[0004]
On the other hand, there is a method in which the light emitting element and the light receiving element are separately manufactured and mounted in a hybrid, but in this case, it is necessary to prepare individual holding members for the light emitting element and the light receiving element. There is a problem of becoming an obstacle.
[0005]
[Problems to be solved by the invention]
In view of this point, an object of the present invention is to provide a photoelectric encoder that can keep the size of the entire apparatus small while maintaining and improving the yield as much as possible. Another object of the present invention is to provide a photoelectric encoder in which the light receiving / light emitting element is not damaged by this contact.
[0006]
[Means for Solving the Problems]
To achieve the above object, a photoelectric encoder according to the present invention includes a surface-emitting light source including a reflective scale on which a predetermined reference grating is formed and a planar light-emitting surface that emits a light beam for irradiating the scale. A light transmissive member disposed in proximity to the surface light source at a position between the surface light source and the reflective scale, and formed on the light transmissive member and disposed in front of the surface light source. a transmission grating, the side of the transmission grating of the interior of the light transmissive member, a plurality of light receiving elements, is constructed by arranging with a predetermined interval between the plurality of light receiving element and the surface emitting A light receiving element array that receives a light beam from a light source via the light emitting side grating and the reference grating, and the light receiving element array includes a transparent electrode that commonly connects the reflective scale side of the plurality of light receiving elements; A plurality of the light receiving elements; A plurality of opaque electrodes formed on the surface-emitting light source side, and an opaque metal wiring for commonly connecting the plurality of opaque electrodes, and the light-emitting side lattice is formed by stacking the same semiconductor as the light receiving element. It is characterized by comprising a dummy element having a structure and a metal film formed on the dummy element.
[0007]
In the present invention, the light emitting side grating may be an electrode film that is provided on the surface emitting light source side of the plurality of light receiving elements and supplies a driving current to the plurality of light receiving elements.
In addition, a deflecting optical member that is formed by a thin film forming technique at a position facing the surface emitting light source on the light transmitting member and deflects a light beam from the surface emitting light source may be provided. For example, a Fresnel lens is suitable as the deflecting optical member.
The light receiving element array is separated into a plurality of light receiving element groups having different detection signal phases, and the light receiving element groups and the light emitting side grating are alternately arranged in the measurement axis direction of the reflective scale. Can be like that. In this case, it is preferable that the light emitting side grating is formed of the same material in the same process as the metal film for wiring of the light receiving element array. Further, the light emitting side grating may be constituted by a dummy element having a structure similar to that of the light receiving element and a metal film formed on the dummy element.
[0008]
DETAILED DESCRIPTION OF THE INVENTION
Next, embodiments of the present invention will be described with reference to the drawings.
[First embodiment]
FIG. 1 shows the configuration of a reflective photoelectric encoder according to the first embodiment of the present invention. The photoelectric encoder of this embodiment includes a reflective scale 10, a surface emitting light source 20 for irradiating light to the reflective scale 10, and a light receiving module that receives and modulates the reflected light from the scale 10. 30.
[0009]
The reflective scale 10 is formed by forming, on a scale substrate 11, a reference lattice 12 having a longitudinal direction in the direction perpendicular to the paper surface (Y-axis direction) at a predetermined pitch P1.
As the surface emitting light source 20, a surface emitting diode is suitable, and a surface emitting laser diode, an organic or inorganic EL element, or the like can be employed.
The light receiving module 30 is disposed to face the scale 10 with a predetermined gap, and can move relative to the scale 1 in the direction of the arrow x in the figure together with the light source 20.
[0010]
As shown in FIG. 1, the light receiving module 30 includes light receiving element arrays 30A and 30B formed by arranging a plurality of light receiving elements PD in the X-axis direction at predetermined intervals. The light receiving element arrays 30A and 30B are arranged so that the phases of the detection signals are 90 degrees different from each other, so that not only the displacement amount but also the displacement direction can be detected.
For example, as shown in FIG. 2, the light receiving element PD includes a transparent electrode 32, a P-type semiconductor layer 34, an i-type semiconductor layer 35, an n-type semiconductor layer 36, an upper portion as a common lower electrode made of ITO, SnO2, ZnO or the like. A pin photodiode made of a metal film 37 as an electrode can be used, but a PN structure may also be used. Each light receiving element PD has a shape in which strips having a longitudinal direction in the direction perpendicular to the paper surface (Y-axis direction) are arranged at predetermined intervals. In these light receiving elements PD, a transparent electrode film 32, a P-type semiconductor layer 34, an i-type semiconductor layer 35, an n-type semiconductor layer 36, and a metal film 37 are sequentially deposited on the entire transparent substrate 31, and then resist, exposure, It can be formed by developing and etching. Alternatively, a plurality of holes may be formed on the glass substrate, and the light receiving element PD may be embedded in the holes.
The light receiving element arrays 30A and 30B are covered with a protective film 33 made of a transparent material.
[0011]
When a light beam is incident on each light receiving element PD, a detection signal appears on the metal film 37, which is transmitted to an interpolation circuit and a signal processing circuit (not shown) by the flexible printed circuit board FPB, and the relative displacement amount and displacement direction of the scale 10 are transmitted. Is detected. The flexible printed circuit board FRB is electrically connected to the light receiving module 30 by an anisotropic conductive tape. Instead of using the flexible printed circuit board FRB, as shown in FIG. 3, a circuit board 40 on which an interpolation circuit or a signal processing circuit is mounted may be connected to the light receiving module 30 by solder bumps or gold bumps 50. Alternatively, as shown in FIG. 4, the circuit board 40 and the light receiving module 30 may be connected by wire bonding 60.
[0012]
The protective film 33 is formed of a transparent material, while the metal film 37 is formed of an opaque material. Therefore, the protective film 33 and the metal film 37 partially transmit the light flux from the surface light source 20. Functions as a light-emitting side grating.
[0013]
In the light emission side grating, each grating window serves as a secondary light source, and transmits light while modulating the light beam from the surface emitting light source 20. The transmitted light beam passes through the transparent electrode 32 and the transparent substrate 31 and is reflected by the scale 10 including the reference grating 12. The reflected light beam passes through the transparent substrate 31 and the transparent electrode 32 and is received by the light receiving element PD. As the light receiving module 30 having the light emitting side grating moves, the light / dark pattern of the reflected image from the scale 10 changes. By examining this change, the relative displacement amount and direction of the scale 10 can be detected.
[0014]
As described above, in the present embodiment, the surface emitting light source 20 and the light receiving element array 30 can be manufactured in separate steps, and only acceptable products can be assembled. Compared to the monolithic manufacturing, the yield is improved, the manufacturing cost can be reduced, and even if the surface light emitting diode is placed close to the planar light receiving module, there is no fear of damage, Miniaturization of the device can also be realized. Further, since the surface emitting light source 20 and the light receiving module 30 are flat, the opposing surfaces can be easily integrated by a method such as anisotropic conductive tape or solder bump, and a separate holding mechanism is provided for the surface emitting light source. do not need.
In the above embodiment, a two-phase sine wave signal of A and B phases is obtained. In addition to the A and B phases, / A and / B phase signals obtained by inverting these 180 degrees are generated. It may be a phase sine wave signal. Further, when it is not necessary to know the displacement direction, one of the light receiving element arrays 30A and 30B may be eliminated to obtain a single-phase sine wave signal.
[0015]
[Second Embodiment]
Next, a second embodiment of the present invention will be described with reference to FIGS. In the first embodiment, the light receiving element arrays 30A and 30B also serve as the light emitting side grating. In this embodiment, as shown in FIG. 5, the light emitting side grating 70 is replaced with the light receiving element array 30A (30B). It is provided separately on the side. That is, in the first embodiment, the light receiving element array 30A (30B) also serves as the light emitting side grating, but in this embodiment, it does not serve as the light emitting side grating.
[0016]
Further, as shown in FIG. 5, a Fresnel lens FL for deflecting a light beam is arranged between the surface emitting light source 20 and the light receiving module 30A (30B), whereby the light receiving element array 30A ( Alternatively, the light beam reflected by the reference grating 12 may be incident on 30B).
[0017]
FIG. 6 shows a cross-sectional structure of the light receiving module 30.
On the transparent substrate 31, a transparent electrode 32 made of ITO, SnO2, ZnO or the like serving as a p-side common electrode of the light receiving element array 30A (30B) is formed. On the transparent electrode 32, a p-type semiconductor layer 34, an i-type semiconductor layer 35, and an n-type semiconductor layer 36 are laminated to form a photodiode PD in which a photoelectric conversion region of a pin junction is formed. The photodiode PD is covered with a protective film 33 made of a transparent material. A metal electrode 37 is formed on the n-type layer 36 of each photodiode PD. A metal wiring 38 serving as an output signal line is formed so as to commonly connect the metal electrodes 37 of the plurality of photodiodes PD.
[0018]
In the region of the light emitting side grating 70 of the transparent substrate 31, a photodiode structure similar to that of the light receiving element array 30 is formed as shown in FIG. These photodiodes are dummy elements. The metal electrodes 37 of these dummy photodiodes are patterned as non-transparent portions of the light emitting side grating 70. The lattice pitch of the light-emitting side lattice 70 is the same as the scale lattice pitch P1 of the scale 10 (or more generally an integer multiple of P1).
In FIG. 6, the light emitting side grating 70 is a dummy photodiode in which a metal electrode 37 is formed. However, as shown in FIG. The metal film 37 ′ may be directly formed. At this time, the metal film 37 ′ is preferably formed by the same process as the metal wiring 38.
[0019]
Also in the present embodiment, the surface emitting light source 20 and the light receiving element array 30 are manufactured in separate steps, and only acceptable products can be assembled. Therefore, the light emitting unit and the light receiving unit are manufactured monolithically. The yield can be improved compared to the case of reducing the manufacturing cost, and there is no risk of damage even if the surface light emitting diode is placed close to the planar light receiving module, so the device can be downsized. realizable.
Also in the above embodiment, a two-phase sine wave signal of A and B phases is obtained. In addition to the A and B phases, / A and / B phase signals are generated by inverting these 180 degrees. 4 phase sine wave signal. Further, when it is not necessary to know the displacement direction, one of the light receiving element arrays 30A and 30B may be eliminated to obtain a single-phase sine wave signal.
[0020]
[Third embodiment]
Next, a third embodiment of the present invention will be described with reference to FIGS.
[0021]
As shown in FIGS. 8 and 9, the light receiving module 30 includes a plurality of light receiving element groups 45 (45a, 45b, 45ab, 45bb) formed on the surface of the transparent substrate 31 opposite to the surface facing the scale 10. And an index scale 70 ′ formed between the light receiving element groups 45 as a light emitting side grating for modulating the irradiation light. The point that the light receiving element groups 45 and the index scale 70 ′ are alternately arranged in the direction of the measurement axis x of the scale 1 is different from the above embodiment. The surface-emitting light source 20 emits irradiation light that is incident substantially perpendicularly to the index scale 70 ′ distributed on the light-receiving module 30 in this way. The plurality of light receiving element groups 45 output A, B, AB, and BB phase displacement signals whose phases are shifted by 90 °, and each light receiving element group 45 includes a plurality of photodiodes PD having the same phase. It consists of
[0022]
In the actual light receiving module 30, a plurality of light receiving element groups 45 and index scales 70 ′ are arranged as a set of A, B, AB, and BB phases as shown in FIG. The output signal lines are commonly connected. As a result, signal strength is guaranteed and S / N is improved.
[0023]
10 is a plan view of the light receiving module 30, and FIG. 11 is a cross-sectional view taken along the line AA 'of FIG. On the transparent substrate 31, a transparent electrode 32 such as ITO, SnO 2, ZnO or the like, which becomes the p-side common electrode of each light receiving element group 45 is formed. On the transparent electrode 32, a p-type semiconductor layer 34, an i-type semiconductor layer 35, and an n-type semiconductor layer 36 are laminated to form a photodiode PD in which a photoelectric conversion region of a pin junction is formed. The photodiode PD is covered with a protective film 33 made of a transparent material. A metal electrode 37 is formed on the n-type layer 36 of each photodiode PD. A metal wiring 38 serving as an output signal line is formed so as to commonly connect the metal electrodes 37 of the plurality of photodiodes PD in each light receiving element group 45.
[0024]
In the area of the index scale 70 ′ of the transparent substrate 31, the same photodiode structure as that of the area of the light receiving element group 45 is formed as shown in FIG. These photodiodes are dummy elements. The metal electrode 37 of these dummy photodiodes is patterned as an opaque portion of the index scale 70 '. That is, also in the present embodiment, as in the second embodiment, the light receiving element array 30A (30B) does not serve as the light emitting side grating.
[0025]
As shown in FIG. 10, the index scale 70 ′ is formed in a distributed manner so as to be sandwiched between the light receiving element groups 45. The grid pitch of the index scale 70 ′ is the same as the scale grid pitch P 1 of the scale 10 (or more generally an integer multiple of P 1), and the array of index scales 70 ′ dispersed with the light receiving element group 45 interposed therebetween. The pitch P2 is P2 = n · P1 (n is a positive integer). Further, since the plurality of photodiodes PD included in the light receiving element group 45 are in phase, the pitch is set to P1 (or more generally, an integer multiple of P1). The arrangement pitch P3 of the light receiving element group 45 is P3 = (m + 1/4) P1 (m is a positive integer). As a result, A, B, AB, and BB phase displacement signals whose phases are shifted by 90 ° are obtained from each light receiving element group 5.
[0026]
In order to obtain a four-phase output, the arrangement pitch P3 of the light receiving element groups 45 is more generally set to P3 = (m + M / 4) P1 (m is a positive integer and M is an odd number). . For example, if M = 3, displacement signals are obtained in the order of A, BB, AB, and B phases that are out of phase by 270 ° from the light receiving element group 5.
In order to obtain a three-phase output whose phase is shifted by 120 °, the arrangement pitch P3 of the light receiving element groups 45 may be P3 = (m + 1/3) P1 (m is a positive integer).
[0027]
Thus, in the third embodiment, in the light receiving module 30, the light receiving element groups 45 and the index scale 70 'are alternately arranged in a state where the areas do not overlap. For this reason, as described above, the material film of the metal electrode 37 used for the light receiving element group 45 can be used as it is for the index scale 70 ′.
In the third embodiment, a dummy photodiode having a metal electrode 37 formed thereon is used as the index scale 70 '. However, as shown in FIG. 12, the dummy photodiode is not formed. Alternatively, the metal film 37 ′ may be formed directly on the protective film 33. At this time, the metal film 37 ′ is preferably formed by the same process as the metal wiring 38.
[0028]
[Modification]
In the first to third embodiments, a one-dimensional scale and a one-dimensional light receiving element array are used as the scale 10, but the present invention is not limited to this, and the two-dimensional scale and the two-dimensional light receiving element. An array may be used.
In the above embodiment, the semiconductor layers 34, 35, and 36 are preferably made of amorphous silicon, but polysilicon can also be used to improve responsiveness. In addition, ZnSe, CdSe, or the like can also be used. In the above-described embodiment, the semiconductor layers 34, 35, and 36 are stacked on the transparent electrode 32 in this order. However, this order is changed, and the semiconductor layers 36, 35, and 34 are stacked on the transparent electrode 32 in this order. You may make it laminate.
[0029]
【The invention's effect】
As described above, in the photoelectric encoder according to the present invention, the surface-emitting light source and the light-receiving element array are manufactured in separate processes, and only acceptable products can be assembled. Compared to the case where parts are manufactured monolithically, the yield can be improved, the manufacturing cost can be reduced, and there is no risk of damage even if the surface emitting light source is arranged close to the planar light transmitting member. Therefore, downsizing of the apparatus can be realized. Moreover, since the holding mechanism of the light emitting / receiving unit can be simplified, the production efficiency can be increased.
[Brief description of the drawings]
FIG. 1 shows a configuration of a photoelectric encoder according to a first embodiment of the present invention.
FIG. 2 shows a structure of a light receiving module 30 used in the first embodiment.
FIG. 3 shows one method for connecting the light receiving module 30 and the circuit board 50 used in the first embodiment.
FIG. 4 shows another method for connecting the light receiving module 30 and the circuit board 50 used in the first embodiment.
FIG. 5 shows a configuration of a photoelectric encoder according to a second embodiment of the present invention.
6 shows an example of a cross-sectional structure of the light receiving module 30 shown in FIG.
FIG. 7 shows another example of the cross-sectional structure of the light receiving module 30.
7 shows another example of a cross-sectional structure of the light receiving module 30. FIG.
FIG. 8 shows a configuration of a photoelectric encoder according to a third embodiment of the present invention.
FIG. 9 is a diagram showing an arrangement configuration of a plurality of sets of light receiving element groups and index scales according to the embodiment;
FIG. 10 is a plan view of the light receiving module 30 according to the embodiment.
FIG. 11 is a cross-sectional view taken along the line AA ′ of FIG.
FIG. 12 shows a modification of the third embodiment.
[Explanation of symbols]
10 ... Scale 20 ... Surface emitting light source 30 ... Light receiving module 31 ... Transparent substrate 32 ... Transparent electrode 33 ... Protective film 50 ...・ ・ ・ ・ ・ Circuit board 70 ・ ・ ・ ・ ・ ・ Emission-side grating

Claims (5)

A reflective scale on which a predetermined reference grating is formed;
A surface-emitting light source having a planar light-emitting surface that emits a light beam for irradiation on the scale;
A light transmissive member disposed close to the surface emitting light source at a position between the surface emitting light source and the reflective scale;
A light emitting side grating formed on the light transmissive member and disposed in front of the surface emitting light source;
On the side of the transmission grating of the interior of the light transmissive member, a plurality of light receiving elements, it is constructed by arranging with a predetermined interval between the plurality of light-receiving elements the light from said surface emitting light source A light receiving element array for receiving light through the light emitting side grating and the reference grating,
The light receiving element array includes a transparent electrode for commonly connecting the reflective scale side of the plurality of light receiving elements, a plurality of opaque electrodes formed on the surface emitting light source side of the plurality of light receiving elements, and a plurality of the opaque elements An opaque metal wiring for connecting electrodes in common,
The light emitting side grating is composed of a dummy element having a structure in which the same semiconductor as the light receiving element is laminated, and a metal film formed on the dummy element. Encoder. The photoelectric encoder according to claim 1, wherein the light emitting side grating is an electrode film provided on the surface emitting light source side of the plurality of light receiving elements and connected to the light receiving element array. The photoelectric encoder according to claim 1, further comprising: a deflecting optical member that is formed at a position facing the surface emitting light source on the light transmitting member and deflects a light beam from the surface emitting light source. The light receiving element array includes a plurality of light receiving element groups having different detection signal phases, and the light receiving element groups and the light emitting side gratings are alternately arranged in a measurement axis direction of the reflective scale. The photoelectric encoder according to 1. The photoelectric encoder according to claim 4, wherein the light emitting side grating is formed of the same material in the same process as the metal film for wiring of the light receiving element array.

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