Optical displacement-measuring apparatus

[0001] [Technical field to which the invention belongs] The present invention relates to an optical displacement measuring device. [0002] [Conventional technology] Conventionally, the xy scale for optically detecting the displacement in the biaxial directions of the x-axis and the y-axis has been known. For this xy scale, the sensor head is equipped with two light receiving devices that output displacement signals in the x-axis and y-axis directions. [0003] [Problems to be Solved by the Invention] However, when two light receiving devices are mounted on a substrate, it is difficult to obtain a highly accurate xy squareness because the xy squareness depends on the mounting accuracy. Further, since the two light receiving devices are mounted in different regions of the substrate, the sensor head cannot be miniaturized. In addition, a rigid flat substrate such as a glass substrate is usually used as the substrate on which the light receiving device is mounted. However, the scale surface of the xy scale is not limited to a flat surface, and may be a spherical surface, a cylindrical surface, or the like. Therefore, in a structure in which a light receiving device is mounted on a rigid substrate, it is not possible to flexibly correspond to an xy scale having various scale surfaces. [0004] The present invention has been made in consideration of the above circumstances, and an object of the present invention is to provide an optical displacement measuring device in which a light receiving element array for biaxial displacement detection is integrated with an excellent squareness. Another object of the present invention is to provide an optical displacement measuring device having a sensor head in which a light receiving element array for detecting biaxial displacement is compactly integrated. Another object of the present invention is to provide an optical displacement measuring device having a sensor head that can flexibly deal with various scale surfaces. [0005] [Means for solving problems] The optical displacement measuring device according to the present invention is arranged so as to be relatively movable in the biaxial direction facing the scale in which the optical lattice is formed in the biaxial direction, and optically detects the relative movement. A sensor head having a light receiving element array for outputting a displacement signal is provided, and the light receiving element array of the sensor head is formed by a substrate and a semiconductor film deposited on the substrate in the first axial direction of the optical lattice. A first light receiving element group that is arranged at a predetermined pitch and outputs a displacement signal corresponding to the displacement in the first axial direction, an insulating layer formed over the first light receiving element group, and an insulating layer. It has a second light receiving element group formed of a semiconductor film deposited on the above, which is arranged at a predetermined pitch in the second axis direction of the optical lattice and outputs a displacement signal corresponding to the displacement in the second axis direction. It is characterized by. [0006] According to the present invention, a light receiving element array for measuring displacement in a biaxial direction is configured as a laminated structure of a group of light receiving elements formed by film deposition of a semiconductor film and lithography. Therefore, the squareness of the biaxial light receiving element group becomes excellent, and a compact and high-performance optical displacement measuring device can be obtained. [0007] In the present invention, as the substrate of the light receiving element array, for example, a transparent substrate having a surface opposite to the surface on which the first and second light receiving element groups are laminated as a light incident surface is used. Further, a flexible resin substrate can be used as this substrate. As a result, even when the scale planes having the two-dimensional optical grid are curved surfaces, they can be flexibly opposed to each other. [0008] The optical displacement measuring device according to the present invention is also a light receiving element that is arranged so as to be relatively movable facing the scale on which an optical lattice is formed and optically detects the relative movement and outputs a displacement signal. The light receiving element array includes a sensor head having an array, the light receiving element array has a light receiving element group obtained by patterning a semiconductor film deposited on a substrate, and at least one of the scale and the light receiving element array is a flexible resin substrate. It is characterized in that it is formed in. [0009] According to the present invention, by forming at least one of the scale and the light receiving element array on the flexible resin substrate, the scale surface shape can be cylindrical, spherical, or free regardless of whether the optical lattice of the scale is one-dimensional or two-dimensional. It can be flexibly adapted to curved surfaces and the like. Specifically, in the present invention, preferably, the light receiving element array includes a flexible resin substrate and a plurality of light receiving elements formed by a semiconductor film deposited on the flexible resin substrate and outputting displacement signals having different phases. It is composed of. When the scale has a two-dimensional optical lattice, the light receiving element array is configured to have first and second light receiving element groups formed at different positions on the substrate corresponding to the two-dimensional optical lattice. Alternatively, it may be configured to have a group of first and second light receiving elements laminated and formed at the same position on the substrate corresponding to a two-dimensional optical lattice via an insulating layer. [0010] BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, examples of the present invention will be described with reference to the drawings. FIG. 1 is a perspective view showing a basic configuration of the optical encoder of the present invention. Scale 1 is an xy scale in which a two-dimensional optical grid 11 in the orthogonal biaxial directions of the x-axis and the y-axis is formed. The sensor head 2 is arranged so as to be relatively movable in the biaxial direction facing the scale 1. The sensor head 2 is a light receiving element array that optically detects relative movement in the biaxial direction and outputs a displacement signal for each axis.<u style="single">3</u>And has a light source 4 such as an LED that illuminates the scale 1. [0011] The light receiving element array 3 includes photodiode arrays PDA1 and PDA2 for detecting displacement in the x-axis direction, and photodiode arrays PDA3 and PDA4 for detecting displacement in the y-axis direction. Specifically, for example, the photodiode array PDA1 has a group of photodiodes (PD) for A-phase output and a group of photodiodes (PD) for B-phase output 90 ° out of phase with each other at a predetermined pitch, and the photodiode array PDA2 has a group of photodiodes (PD) arranged at a predetermined pitch. Photodiodes (PD) groups for AB phase and BB phase outputs, which are opposite to the A and B phase outputs, are arranged at a predetermined pitch, respectively. Similarly, the photodiode array PDA3 has a group of photodiodes (PD) for A-phase and B-phase outputs, and the photodiode array PDA4 has a group of photodiodes (PD) for AB-phase and BB-phase outputs. Be arranged. [0012] In the present invention, the light receiving element array 3 including these biaxially oriented photodiode arrays PDA1-PDA4 is integrally formed by patterning an amorphous semiconductor film deposited on a predetermined array substrate 30. FIG. 2 shows the layout of the light receiving element array 3, and FIG. 3 shows the AA'cross-sectional structure of FIG. The substrate 30 is a transparent substrate, and in this example, the back surface of the substrate 30 is a light incident surface on which the reflected light from the scale enters. [0013] A transparent electrode 31 serving as a common electrode for each photodiode PD is formed on the substrate 30. By patterning the amorphous semiconductor film 32 deposited on the transparent electrode 31, the arrays PDA3 and PDA4 consisting of striped photodiode PDs elongated in the x-axis direction and the striped photodiode PD elongated in the y-axis direction are used. Arrays PDA1 and PDA2 are formed at the same time. [0014] Specifically, the semiconductor film 32 has a pin layer structure or a pn layer structure. A terminal electrode 33 is formed on the upper surface of each photodiode PD. The terminal electrode 33 is continuously deposited with the semiconductor film 32 and patterned at the same time as the semiconductor film 32. Each photodiode PD is covered with an insulating layer 34 such as a silicon oxide film. [0015] In this way, the photodiode arrays PDA1, PDA2 and PDA3, PDA4 that detect the displacement of the xy scale 1 in the biaxial direction are integrally formed by patterning a common amorphous semiconductor film 32, and these are individually made to form a substrate. The squareness of the xy biaxial is superior compared to the case where it is attached to the light receiving element array 3, and the light receiving element array 3 becomes smaller as a whole. [0016] The sensor head 2 according to the configuration shown in Fig. 1 to Fig. 3 can be combined with the sensor head 2 in the xy plane by processing the displacement signals of the four photodiode arrays PDA1-PDA4 as well as measuring the linear displacement in the x-axis and y-axis directions. It is also possible to measure the relative rotation angle displacement θ between scales 1. [0017] In the configurations of FIGS. 1 to 3, silicon is typically used as the amorphous semiconductor film 32, but ZnSe, CdSe, and the like are also used. The same applies to the following examples. [0018] An example in which the photodiode array in the biaxial direction has a laminated structure based on the configurations of FIGS. 1 to 3 will be described below. FIG. 4 is a layout of such a light receiving element array 3, and FIGS. 5 and 6 are cross-sectional views taken along the line A-A'and B-B'of FIG. 3, respectively. The photodiode array PDAy for detecting displacement in the y-axis direction and the photodiode array PDAx for detecting displacement in the x-axis direction are formed by using different amorphous semiconductor films 32 and 36. The first layer amorphous semiconductor film 32 is deposited on the transparent substrate 30 via the transparent electrode 31 which is a common electrode of the photodiode array PDAy, and the first layer amorphous semiconductor film 32 is patterned to form the photodiode array PDAy. [0019] Each terminal electrode 33 of the photodiode array PDAy is a transparent electrode. This photodiode array PDAy is covered with an interlayer insulating film 34 such as a silicon oxide film. A second layer amorphous semiconductor film 36 is deposited on the interlayer insulating film 34 via a transparent electrode 35 which is a common electrode of the photodiode array PDAx, and this is patterned to form a photodiode array PDAx. A metal electrode can be used for each terminal electrode 37 of the photodiode array PDAx. The photodiode array PDAx is further covered by an insulating layer 37. [0020] The terminal electrode 33 of the photodiode array PDAy can also be a metal electrode. In this case, the terminal electrode 33 blocks the light from the back surface of the substrate to the photodiode array PDAx, but this adjusts the area ratio of the photodiode arrays PDAx and PDAy so that almost the same amount of light enters both. If you do, there is no problem. It can also be dealt with by adjusting the output gains of the photodiode arrays PDAx and PDAy separately from the area ratio or together with the area ratio. [0021] [0021] By stacking the photodiode arrays for detecting displacement in the biaxial direction in this way, the light receiving element array 3 becomes even smaller. Further, since the photodiode array is laminated by the lithography technique, the squareness of the xy biaxis is also excellent. In the lower photodiode array PDAy, both the upper and lower electrodes are transparent electrodes. Therefore, the light incident from the back surface of the substrate 30 is partially photoelectrically converted by the photodiode array PDAy and transmitted to the upper photodiode array PDAx. As a result, a displacement signal with sufficient S / N can be obtained for both the photodiode arrays PDAy and PDAx. [0022] In the above configuration example, a hard substrate such as a glass substrate can be used as the transparent substrate 30, but a flexible resin substrate is preferably used. As the flexible resin substrate, for example, a polyimide resin is used. As a result, the applicable range of the optical encoder is widened. An example of such an application will be described below. [0023] In FIG. 7, scale 1 is an example of a cylindrical scale. The cylindrical scale 1 has a biaxial optical grid formed in the cylindrical axis direction (x axis) and the circumferential direction (θ) on the outer peripheral surface thereof. On the other hand, a flexible resin substrate is used for the substrate 30 of the light receiving element array 3 forming the photodiode arrays PDA and PDA that detect the displacement in the x-axis and the θ direction. [0024] The light receiving element array 3 shall have the same photodiode array configuration as in FIGS. 1 to 3 (or the same photodiode array configuration as in FIGS. 4 to 6) except for the substrate material. Further, the manufacturing process is performed by utilizing film formation and lithography technology with the substrate 30 in a flat state. If the substrate 30 is a flexible resin substrate, the obtained light receiving element array 3 is curved according to the diameter of the cylindrical scale 1 as shown in FIG. 7 and faces the outer peripheral surface of the cylindrical scale 1 with a predetermined gap. Can be done. [0025] The pitch of the light receiving element array 3 in the θ direction is slightly deviated from the pitch of the photodiode arrays PDA and PDA in the state where the pattern is formed on the plane by bending. However, this pitch deviation can be ignored if the diameter of the cylindrical scale 1 is larger than a certain level. Therefore, by using the flexible resin substrate, the range in which the light receiving element array can be actually applied becomes wide. Since the above-mentioned pitch deviation can be predicted corresponding to the diameter of the curvature, the pattern pitch on the plane can be determined in anticipation of the curvature. [0026] In FIG. 8, scale 1 is a cylindrical scale, but only one axis in the circumferential (θ) direction is measured. That is, the optical grid 11 of the scale 1 is formed on the outer peripheral surface at a predetermined pitch only in the θ direction. In this case, the light receiving element array 3 is also composed of the photodiode array PDA only in the θ direction. In this case as well, by using the flexible resin substrate as the substrate 30, flexible application becomes possible as in the case of FIG. 7. [0027] In FIG. 9, scale 1 is an example of a free-form surface scale. On the free-form surface scale 1, biaxial optical grids in the x-axis direction and the y-axis direction are formed on the free-form surface. On the other hand, a flexible resin substrate is used for the substrate 30 of the light receiving element array 3 forming the photodiode arrays PDA and PDA that detect the displacement in the x-axis direction and the y-axis direction. The light receiving element array 3 shall have the same photodiode array configuration as in FIGS. 1 to 3 (or the same photodiode array configuration as in FIGS. 4 to 6) except for the substrate material. As a result, the light receiving element array 3 is deformed according to the free curved surface scale 1 and is opposed to the outer peripheral surface of the scale 1 with a predetermined gap, so that the linear displacement and the rotational displacement θ in the xy axis direction can be measured. [0028] In the configuration of FIG. 9, the scale 1 can be formed on the flexible substrate, and the array substrate 30 of the light receiving element array 3 can be made rigid. In this case, the scale 1 is attached to an object having a free curved surface to become the free curved surface scale 1. On the other hand, the sensor heads 2 are opposed to each other with a predetermined gap so that they can move relative to each other. Also in the examples of FIGS. 7 and 8, the optical grid 11 of the scale 1 can be formed by using the flexible resin substrate and attached to the cylindrical surface. Further, both the scale 1 and the array substrate 30 of the light receiving element array 3 can be flexible substrates. When a flexible substrate is used for the light receiving element array 3, a surface emitting type light emitting element, for example, an organic EL element that can be flexibly deformed can be attached and used as a light source. [0029] In FIG. 10, scale 1 is an example of a spherical scale. Scale 1 is formed with two optical grids 11 having circumferential directions θ and φ orthogonal to the spherical surface. The sensor head 2 is attached so as to cover the scale 1 with a cap. A flexible resin substrate is used for the substrate 30 of the light receiving element array 3 forming the photodiode arrays PDA and PDA that detect displacements in the θ and φ directions so as to face the spherical surface of the scale 1. There is. The light receiving element array 3 shall have the same photodiode array configuration as in FIGS. 1 to 3 (or the same photodiode array configuration as in FIGS. 4 to 6) except for the substrate material. By using the flexible resin substrate as the substrate of the light receiving element array 3 in this way, it is possible to correspond to a spherical scale. [0030] Some specific configuration examples of the sensor head 2 of the optical displacement measuring device according to the present invention are given below. The sensor head 2 of FIG. 11 uses a transparent substrate 5 and mounts a light receiving element array 3 on the transparent substrate 5. An LED chip as a light source 4 is mounted on the light receiving element array 3 with its upper surface as a light emitting surface, and the LED mounting portion is molded with a transparent resin 6 having a convex surface. A reflective film 7 is formed on the convex surface of the transparent resin 6. As a result, the light from the LED is reflected by the convex surface to become substantially parallel light, and is irradiated to the scale 1 via the transparent substrate 5. In this case, the light source light is applied to the scale through the region where the light receiving element of the light receiving element array 3 is not formed. If the first optical grid is formed in this region, a three-grid system can be constructed. Further, even if a first optical grid is provided under the light receiving element array 3 and the light source light is applied to the scale through the light receiving element array 3 and the first optical grid, the three-grid system can be configured. In FIG. 11, a signal processing circuit 8 for processing the output signal of the light receiving element array 3 is also mounted on the transparent substrate 5. [0031] FIG. 12 shows an example in which a three-lattice system is configured. In this case, the sensor head 2 has a light source side index grid 10 formed on the index substrate 9 made of a transparent substrate, and the light from the light source 4 is applied to the scale 1 through the index grid 10. There is. A light receiving element array 3 is mounted on the index board 9 apart from the index grid 10. [0032] The sensor head 2 in FIG. 13 is an example in which a surface emitting LED is used as the light source 4. A surface-emitting LED is arranged with its light emitting surface facing the scale 1 side, and a light receiving element array 3 is mounted on the light emitting surface. The light from the LED is irradiated to the scale 1 substantially vertically through the light receiving element array 3, and the light reflected substantially vertically from the scale 1 is detected by the light receiving element array 3. As the surface light emitting element, for example, an organic EL element can be used in addition to the LED. [0033] FIG. 14 is a modification of FIG. The light source is simply configured by arranging LED4. The light of the LED 4 is incident on the light receiving element array 3 which also serves as the first lattice and the third lattice substantially vertically, passes through the light receiving element array 3, and is irradiated on the scale 1. FIG. 15 is a modification of FIG. A concave mirror is composed of a transparent resin body 6b in which the sphere is divided into approximately 1/4 and a reflective film 7, and the LED 4 is attached to the side surface of the transparent resin body 6b with the light emitting surface vertical. The light reflected by the reflective film 7 obliquely enters the index grid 10 and irradiates the scale 1. A three-grid system that uses an index grid (or pinhole array) with the same pitch as the scale grid on the light source side is optically divided into two (that is, the output signal pitch is half that of the two-grid system). ) Although it has an advantage, the light source side index grid (or pin pole array) is not always necessary. For example, in the configurations of FIGS. 12 and 15, the light source side index grid 10 can be omitted. [0034] In the examples so far, each photodiode PD of the light receiving element array 3 has an elongated rectangular pattern, but the pattern of this photodiode PD is obtained by bundling a plurality of photodiodes of the same phase, FIGS. 16 (a) to 16 (c). The pattern can be as shown in. In FIG. 16A, a connecting portion 141 serving as a contact portion for terminal wiring is provided at the center of a plurality of photodiode PDs. In FIG. 16B, connecting portions 142 are provided at the ends of a plurality of photodiodes. Further, in FIG. 16 (c), a plurality of connecting portions 143 are provided. [0035] [Effect of the invention] As described above, according to the present invention, it is possible to obtain a compact optical displacement measuring device in which a light receiving element array for detecting biaxial displacement is integrated with an excellent squareness. Further, according to the present invention, an optical displacement measuring device having a sensor head capable of flexibly dealing with various scale surfaces can be obtained. [Simple explanation of drawings] FIG. 1 is a perspective view showing a basic configuration of an optical displacement measuring device according to the present invention. FIG. 2 is a plan view showing a configuration example of a sensor head. 3 is a cross-sectional view taken along the line AA'of FIG. FIG. 4 is a plan view showing another configuration example of the sensor head. [Fig. 5] It is a cross-sectional view of AA'of FIG. 6 is a cross-sectional view taken along the line B-B'of FIG. FIG. 7 is a perspective view showing a configuration of a displacement measuring device applied to a cylindrical scale. FIG. 8 is a perspective view showing the configuration of another displacement measuring device applied to a cylindrical scale. FIG. 9 is a perspective view showing a configuration of a displacement measuring device applied to a free-form surface scale. FIG. 10 is a perspective view showing a configuration of a displacement measuring device applied to a spherical scale. FIG. 11 is a diagram showing a specific configuration example of a sensor head. FIG. 12 is a diagram showing another configuration example of the sensor head. FIG. 13 is a diagram showing another configuration example of the sensor head. FIG. 14 shows a configuration example in which the configuration of FIG. 11 is modified. FIG. 15 shows a configuration example in which the configuration of FIG. 12 is modified. FIG. 16 is a diagram showing another layout example of the light receiving element array. [Explanation of symbols] 1 ... scale, 11 ... optical grid, 2 ... sensor head, 3 ... light receiving element array, 4 ... light source, PDA ... photodiode array, 30 ... array board, 31 , 35 ... transparent electrode, 32 ... semiconductor film, 33,37 ... terminal electrode, 34,38 ... insulating layer.