JP5172195B2 - Optical displacement measuring device - Google Patents

Description

  The present invention relates to an optical displacement measuring device used for measuring linear displacement, rotational displacement, and the like, and more particularly to an optical displacement measuring device provided with a reflective scale.

  2. Description of the Related Art Conventionally, an optical displacement measuring device including a scale and a detection head is known as a measuring instrument that performs precise measurement such as linear displacement and angular displacement. This optical displacement measuring device is widely used in electronic component mounting devices and the like that require highly accurate positioning control of conveyed objects. With recent advances in machining and miniaturization of semiconductors, there is a demand for optical displacement measuring devices that can perform measurements with higher accuracy and higher resolution.

  As a conventional optical displacement measuring device of this type, for example, there is one described in Patent Document 1. Patent Document 1 describes a photoelectric encoder that detects a position, an angle, a speed, an angular speed, and the like, a scale used for the photoelectric encoder, and the like. The scale described in Patent Document 1 is “a tape-shaped base material and a plurality of protrusions formed by a thin film on one surface of the base material and arranged at a predetermined pitch in the longitudinal direction of the base material. And the concavo-convex portions formed in the longitudinal direction of the base material by the plurality of protrusions form a scale, and together form a light reflecting surface ”.

  The photoelectric encoder using this scale is “an index scale having another scale corresponding to the scale of the scale by moving relative to the scale, and a relative movement of the scale together with the index scale. It has a light source that irradiates the scale with light via an index scale, and a light receiving means that receives the light emitted from the light source and reflected by the scale ”.

According to the invention described in Patent Document 1, “the scale processing accuracy is high, and both the concave and convex portions are light reflecting surfaces, so that the amount of light received by the light receiving means of the encoder, ie, the signal intensity is increased. (See paragraph number [0014]) ”and the like are expected.
JP 2006-162498 A

  However, in the photoelectric encoder described in Patent Document 1, a metal thin film such as Cr is formed on the surface of a base material made of metal such as stainless steel, and a plurality of protrusions (lattices) are formed on the scale by photoetching. Was.

  The photoetching method is performed as follows. First, a metal thin film such as Cr is formed on the surface of the base material, and a resist (photosensitive agent) is applied on the metal thin film by a resist coating apparatus. Next, the coated resist is exposed to a pattern having a predetermined pitch and then developed. Then, by etching the metal thin film with an etching apparatus using the remaining resist as an etching mask, a plurality of protrusions (lattices) are formed on the metal thin film.

  As described above, when a lattice is formed on a metal thin film formed on the surface of a base material by photoetching, expensive equipment such as a resist coating apparatus and an etching apparatus is required, and the number of work processes is increased, which increases costs. The problem was that

  In addition, a scale is known in which a grid is formed directly by pressing a mold against a base material made of metal. However, when a grid is formed in this manner, the accuracy of the unevenness of the grid is reduced, and the scale is fine. It was difficult to form a lattice (for example, a pitch of 10 μm or less). As a result, there is a problem that an optical displacement measuring device with high accuracy and high resolution cannot be realized.

  An object of the present invention is to provide an optical displacement measuring device that can measure displacement with high accuracy and high resolution at low cost in consideration of the above-mentioned problems.

The optical displacement measuring device of the present invention is diffracted by a reflective scale having a displacement measuring diffraction grating arranged along a measurement axis, a light source for irradiating light to the displacement measuring diffraction grating, and the displacement measuring diffraction grating. And a detection head that moves relative to the reflective scale. The reflective scale is laminated on the base material and the base material, and is made of a photocurable resin or a thermosetting resin, and a displacement measuring diffraction grating is formed on the surface opposite to the base material. possess a resin layer, and a reflective film formed on the surface of the resin layer, and a protective film surface on the opposite side is formed on the plane with the resin layer covers the resin layer reflecting film is formed, the resin The most important feature of the layer is that a diffraction grating for displacement measurement is formed by pressing after a photocurable resin or a thermosetting resin formed in a sheet shape is attached to a base material .

  According to the optical displacement measuring device of the present invention, since the diffraction grating for measuring the displacement of the reflective scale is formed on the resin layer made of a photocurable resin or a thermosetting resin, a fine pitch grating can be formed with high accuracy. And it can process easily. As a result, the displacement can be measured with high accuracy and high resolution, and the cost can be reduced.

  Hereinafter, the best mode for carrying out the optical displacement measuring device of the present invention will be described with reference to the drawings, but the present invention is not limited to the following modes.

  1 to 4 show examples of embodiments of the present invention. That is, FIG. 1 is a perspective view showing a first embodiment of the optical displacement measuring device of the present invention, and FIG. 2 is an explanatory diagram for explaining the configuration of a reflective scale according to the optical displacement measuring device of the present invention. 3A is an enlarged plan view showing a part of a reflective scale according to the optical displacement measuring device of the present invention, FIG. 3B is a cross-sectional view taken along line AA shown in FIG. 3A, and FIG. 4 is an optical displacement measuring device. It is explanatory drawing explaining the manufacturing process of the reflection type scale which concerns on.

The first embodiment of the optical displacement measuring device of the present invention shown in FIG. 1 measures linear displacement.
This is configured as a so-called linear type optical displacement measuring apparatus 1. The optical displacement measuring device 1 is an incremental method for measuring displacement from a fixed point (reference position) arbitrarily selected.

  As shown in FIG. 1, the optical displacement measuring device 1 has a reflective scale 2 having a displacement measuring diffraction grating 31 arranged along a measurement axis X, and moves relative to the reflective scale 2. A possible detection head 3 is provided.

  The detection head 3 of the optical displacement measuring apparatus 1 includes a light source 11 that irradiates light to the displacement measuring diffraction grating 31, a light receiving unit 12 that receives light diffracted by the displacement measuring diffraction grating 31, and the reflective scale 2. The fixed point detection light source for irradiating light to the fixed point detection diffraction grating 32, which will be described later, and a fixed point detection light receiving unit for receiving the light diffracted by the fixed point detection diffraction grating 32, and the like. Yes.

  In the present embodiment, the detection head 3 is provided with a fixed point detection light source. However, the detection head according to the present invention is not limited to this. The detection head according to the present invention may be configured to irradiate the displacement measurement diffraction grating 31 and the fixed point detection diffraction grating 32 with light emitted from one light source. As such a configuration, for example, a configuration in which a part of light emitted from a light source and diffracted by the displacement measuring diffraction grating 31 is reflected by a mirror or the like and irradiated to the fixed point detecting diffraction grating 32 can be exemplified.

The reflective scale 2 of the optical displacement measuring device 1 is a so-called tape scale that can be wound in a roll shape. The reflective scale 2, as shown in FIGS. 2 and 3, the base over scan material 21, the displacement-measuring diffraction grating 31 on the surface opposite to the base member 21 while being stacked on the base material 21 is formed And a protective film 24 that covers the resin layer 22 on which the reflective film 23 is formed, and a reflective film 23 that is formed on the surface of the resin layer 22.

  The base material 21 of the reflective scale 2 has a thin strip shape (tape shape) extending in the measurement axis X direction. As the material of the base material 21, stainless steel (SUS) having a low thermal expansion and high strength is applied. However, the base material of the reflective scale according to the present invention is not limited to stainless steel (SUS), and other metals such as aluminum and copper can be applied.

  The resin layer 22 of the reflective scale 2 is formed by superimposing an ultraviolet curable resin, which is a specific example of a photocurable resin, on one plane of the base material 21. The material of the resin layer 22 is not limited to the above-described photocurable resin such as an ultraviolet curable resin, and for example, a thermosetting resin such as an epoxy resin (EP) can be applied. A displacement measuring diffraction grating 31 and a fixed point detecting diffraction grating 32 are formed on the surface of the resin layer 22 opposite to the base material 21.

  The displacement measuring diffraction grating 31 is formed by providing a plurality of slits extending in the width direction at appropriate intervals in the longitudinal direction of the base material 21. The displacement measuring diffraction grating 31 generates diffracted light when irradiated with light from the light source 11 of the detection head 2. That is, the detection head 2 or the reflective scale 3 is moved in the measurement axis X direction, and the diffracted light generated by the displacement measurement diffraction grating 31 is received by the light receiving unit 12 of the detection head 2, thereby The relative displacement of the reflective scale 3 is measured.

  The fixed point detecting diffraction grating 32 has a first pattern region 34 and a second pattern region 35 in which different grating patterns are formed. The first pattern region 34 and the second pattern region 35 are formed in the same shape as a quadrangle, and are arranged in parallel along the measurement axis X with one side extending in the width direction of the base material 21 as a boundary between each other. Yes. These first and second pattern regions 34 and 35 generate diffracted light in different directions when irradiated with light from a fixed point detection light source.

  The fixed point detection light receiving unit of the detection head 2 includes two light receiving units that respectively receive two diffracted lights generated by the first and second pattern regions 34 and 35 of the fixed point detection diffraction grating 32. . When the irradiation area (beam spot) of the light emitted from the fixed point detection light source is at the boundary between the first and second pattern areas 34 and 35, the magnitudes of the signals obtained from the respective diffracted lights become equal. Thereby, a fixed point is detected.

  The reflective film 23 of the reflective scale 2 is formed by depositing chromium (Cr) that has high hardness and is hardly damaged on the surface of the resin layer 22 by vapor deposition or sputtering. In the present embodiment, chromium (Cr) is applied as the reflective film 23, but the reflective film according to the present invention is not limited to this. As the reflective film according to the present invention, other metals such as gold, platinum, and aluminum can be applied.

  The protective film 24 is made of a transparent member that transmits light emitted from the light source 11 and the fixed point detection light source. An example of the protective film 24 is polycarbonate (PC) formed in a film shape. In that case, an adhesive may be applied to one surface of the protective film 24 in advance. Thus, by covering the resin layer 22 on which the reflective film 23 is formed with the protective film 24, it is possible to prevent the reflective film 23 from being stained or scratched. As a result, it is possible to always obtain predetermined diffracted light and measure an accurate displacement amount, and to improve the reliability of the optical displacement measuring apparatus 1.

  The protective film according to the present invention is not limited to a polycarbonate (PC) film. As the protective film according to the present invention, other resin films such as polyethylene terephthalate (PET) can be applied, and for example, a transparent resin material such as polycarbonate (PC) can be applied. .

  In the reflective scale 2 of the present embodiment, the protective film 24 is provided on the resin layer 22 on which the reflective film 23 is formed. However, as the reflective scale according to the present invention, the protective film 24 is not formed. It can also be configured. In this case, the reflective film formed on the resin layer becomes the surface of the reflective scale.

  The reflective scale 2 having the above-described configuration can be manufactured, for example, as follows. First, as shown in FIG. 4A, an ultraviolet curable resin is applied to one plane of the base material 21 to form a resin layer 22. At this time, the adhesion between the base material 21 and the resin layer 22 made of an ultraviolet curable resin may be improved by performing a surface treatment on one flat surface of the base material 21.

  Further, the ultraviolet curable resin may be formed in a sheet shape having a size corresponding to the shape of the base material 21 in advance. In that case, a sheet-like ultraviolet curable resin is attached to one surface of the base material 21.

  Next, as shown in FIG. 4B, the original plate 41 on which the mold 41 a corresponding to the displacement measurement diffraction grating 31 and the fixed point detection diffraction grating 32 is formed is pressed against the resin layer 22. That is, the resin layer 22 is pressed by the original plate 41. The original plate 41 is formed of, for example, a member capable of transmitting ultraviolet rays such as quartz glass, and is subjected to a peeling process such that the ultraviolet curable resin is easily peeled off from the mold 41a corresponding to the displacement measuring diffraction grating 31 and the like. It has been subjected.

  Subsequently, as shown in FIG. 4C, ultraviolet rays are irradiated from the original 41 side by the ultraviolet irradiation device 42. Accordingly, the resin layer 22 is irradiated with ultraviolet rays through the original plate 41, and the resin layer 22 is pressed against the original plate 41 and cured in a deformed state.

  Next, as shown in FIG. 4D, the original plate 41 is peeled off from the cured resin layer 22. Thereby, the displacement measurement diffraction grating 31 and the fixed point detection diffraction grating 32 (see FIG. 2 and the like) are formed in the resin layer 22. At this time, since the mold 41a of the original plate 41 has been subjected to the peeling process, the original plate 41 can be easily peeled off from the resin layer 22, and the deformation of the cured resin layer 22 is prevented and the displacement measuring diffraction grating 31 and The fixed point detecting diffraction grating 32 can be formed with high accuracy.

  Next, as shown in FIG. 4, chromium (Cr) is formed on the surface of the resin layer 22 by vapor deposition or sputtering to form the reflective film 23. And the protective film 24 is formed in the resin layer 22 in which the reflective film 23 was formed, and, thereby, the reflective scale 2 is manufactured. In addition, also when a resin layer is formed with a thermosetting resin, a reflective scale can be manufactured by passing through the process mentioned above. In that case, the thermosetting resin is cured using a heating device instead of the ultraviolet irradiation device 42.

  As described above, the reflective scale 2 of the optical displacement measuring device 1 includes the step of forming the resin layer 22 on the base material 21, and the displacement measuring diffraction grating 31 by pressing the mold 41 a of the original plate 41 against the resin layer 22. The step of forming the fixed point detection diffraction grating 32, the step of forming the reflection film 23 on the resin layer 22 on which the diffraction gratings 31 and 32 are formed, and the protective film 24 on the resin layer 22 on which the reflection film 23 is formed. It is manufactured by passing through the process of forming.

  By manufacturing the reflective scale 2 in this way, it is possible to easily form the displacement measurement diffraction grating 31 and the fixed point detection diffraction grating 32 in the resin layer 22 with a small number of work steps without requiring an expensive apparatus. It is possible to achieve a significant cost reduction. In addition, the displacement measurement diffraction grating 31 and the fixed point detection diffraction grating 32 can be accurately formed at a fine pitch, and a scale capable of measuring displacement with high accuracy and high resolution can be provided.

  In the present embodiment, an example in which a tape-type reflective scale is applied has been described. However, the reflective scale according to the present invention is not limited to the tape-type. The reflective scale according to the present invention can be applied to a long reflective scale having an appropriate thickness. In this case, as a material of the base material constituting a part of the reflective scale, glass or the like can be applied as well as the above-described metal such as stainless steel (SUS).

  As described above, according to the optical displacement measuring apparatus of the present invention, the reflective scale is provided with the resin layer made of a photocurable resin or a thermosetting resin, and the displacement measurement diffraction grating and the fixed point detection are provided on the resin layer. A diffraction grating was formed. Therefore, a fine diffraction grating can be easily formed with high accuracy simply by pressing a mold against the resin layer. In addition, an expensive apparatus such as photoetching is not required, and the diffraction grating can be formed with a small number of work steps, so that a significant cost reduction can be achieved. As a result, it is possible to provide an optical displacement measuring device that can perform displacement measurement with high accuracy and high resolution at low cost.

  Furthermore, since the resin layer on which the reflective film is formed is covered with a protective film, it is possible to prevent the reflective film from being stained or scratched, and it is possible to always obtain a predetermined diffracted light and accurately measure the amount of displacement. it can. As a result, durability and reliability can be improved. Moreover, since the tape-type reflective scale is formed by forming the base material into a thin strip shape, an optical displacement measuring device that is easy to carry and excellent in portability can be provided.

  The present invention is not limited to the embodiment described above and shown in the drawings, and various modifications can be made without departing from the scope of the invention. For example, in the above-described embodiment, an example of a linear type that measures linear displacement as an optical displacement measuring device has been described, but the present invention can also be applied to a rotary type that measures rotational displacement.

It is a perspective view which shows 1st Embodiment of the optical displacement measuring device of this invention. It is explanatory drawing explaining the reflection type scale which concerns on 1st Embodiment of the optical displacement measuring device of this invention. 1 is a cross-sectional view of a part of a reflective scale according to a first embodiment of an optical displacement measuring device of the present invention. FIG. 4A illustrates a manufacturing process of a reflective scale according to the optical displacement measuring device of the present invention. FIG. 4A is an explanatory diagram showing a state in which a resin layer made of an ultraviolet curable resin is provided on a base material, and FIG. 4B is a resin layer. FIG. 4C is an explanatory diagram of a state in which the original plate is pressed against the resin layer and irradiated with ultraviolet rays, and FIG. 4D is a state in which the original plate is peeled off and a displacement measuring diffraction grating is formed on the resin layer. FIG. 4E is an explanatory diagram of a state in which a reflective film is formed on the resin layer on which the displacement measuring diffraction grating is formed, and FIG. 4F is an explanatory diagram of a state in which a protective film is formed on the resin layer on which the reflective film is formed. It is.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Optical displacement measuring device, 2 ... Reflective scale, 3 ... Detection head, 11 ... Light source, 12 ... Light-receiving part, 21 ... Base material, 22 ... Resin layer, 23 ... Reflective film, 24 ... Protective film, 31 ... Displacement measuring diffraction grating 32... Fixed point detection diffraction grating 34... First pattern area 35. Second pattern area

Claims (4)

A reflective scale having a displacement measuring diffraction grating disposed along the measurement axis;
A detection head that has a light source that irradiates light to the displacement measurement diffraction grating and a light receiving unit that receives light diffracted by the displacement measurement diffraction grating, and is moved relative to the reflective scale; With
The reflective scale is
A base material;
A resin layer that is laminated on the base material, is made of a photo-curing resin or a thermosetting resin, and the displacement measurement diffraction grating is formed on the surface opposite to the base material,
A reflective film formed on the surface of the resin layer;
Have a, a protective film surface on the opposite side is formed on the plane with the resin layer covers the resin layer in which the reflecting film is formed,
The optical layer characterized in that the resin layer is obtained by forming the displacement measurement diffraction grating by pressing after a photo-curing resin or a thermosetting resin formed in a sheet shape is attached to a base material. Type displacement measuring device. The optical displacement measuring device according to claim 1, wherein the base material is formed in a tape shape. The optical displacement measuring device according to claim 1 or 2 , wherein a fixed point detecting diffraction grating for detecting a fixed point is formed in the resin layer. The fixed point detecting diffraction grating has a first pattern area and a second pattern area in which different grating patterns are formed across a boundary,
The optical displacement measuring device according to claim 3 , wherein the fixed point is detected when light emitted by the detection head irradiates a boundary between the first pattern region and the second pattern region.

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