WO2024095488A1 - バンドルファイバ、偏光センサ、光学式エンコーダ、光散乱検出センサおよびバンドルファイバの製造方法 - Google Patents

バンドルファイバ、偏光センサ、光学式エンコーダ、光散乱検出センサおよびバンドルファイバの製造方法 Download PDF

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WO2024095488A1
WO2024095488A1 PCT/JP2022/041257 JP2022041257W WO2024095488A1 WO 2024095488 A1 WO2024095488 A1 WO 2024095488A1 JP 2022041257 W JP2022041257 W JP 2022041257W WO 2024095488 A1 WO2024095488 A1 WO 2024095488A1
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Prior art keywords
fiber
light
bundle
fibers
wire grid
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English (en)
French (fr)
Japanese (ja)
Inventor
義明 金森
泰佑 岡谷
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Tohoku University NUC
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Tohoku University NUC
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Priority to JP2024554087A priority Critical patent/JPWO2024095488A1/ja
Priority to PCT/JP2022/041257 priority patent/WO2024095488A1/ja
Publication of WO2024095488A1 publication Critical patent/WO2024095488A1/ja
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    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01D—MEASURING NOT SPECIALLY ADAPTED FOR A SPECIFIC VARIABLE; ARRANGEMENTS FOR MEASURING TWO OR MORE VARIABLES NOT COVERED IN A SINGLE OTHER SUBCLASS; TARIFF METERING APPARATUS; MEASURING OR TESTING NOT OTHERWISE PROVIDED FOR
    • G01D5/00—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable
    • G01D5/26—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable characterised by optical transfer means, i.e. using infrared, visible, or ultraviolet light
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01D—MEASURING NOT SPECIALLY ADAPTED FOR A SPECIFIC VARIABLE; ARRANGEMENTS FOR MEASURING TWO OR MORE VARIABLES NOT COVERED IN A SINGLE OTHER SUBCLASS; TARIFF METERING APPARATUS; MEASURING OR TESTING NOT OTHERWISE PROVIDED FOR
    • G01D5/00—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable
    • G01D5/26—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable characterised by optical transfer means, i.e. using infrared, visible, or ultraviolet light
    • G01D5/32—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable characterised by optical transfer means, i.e. using infrared, visible, or ultraviolet light with attenuation or whole or partial obturation of beams of light
    • G01D5/34—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable characterised by optical transfer means, i.e. using infrared, visible, or ultraviolet light with attenuation or whole or partial obturation of beams of light the beams of light being detected by photocells
    • G01D5/347—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable characterised by optical transfer means, i.e. using infrared, visible, or ultraviolet light with attenuation or whole or partial obturation of beams of light the beams of light being detected by photocells using displacement encoding scales
    • G—PHYSICS
    • G02—OPTICS
    • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B6/00—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings
    • G02B6/04—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings formed by bundles of fibres
    • G—PHYSICS
    • G02—OPTICS
    • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B6/00—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings
    • G02B6/24—Coupling light guides
    • G02B6/26—Optical coupling means
    • G02B6/27—Optical coupling means with polarisation selective and adjusting means

Definitions

  • the present invention relates to a fiber bundle, a polarization sensor, an optical encoder, a light scattering detection sensor, and a method for manufacturing a fiber bundle.
  • Encoders are sensors that convert the amount of mechanical displacement caused by rotation, etc. into an electrical signal, and process this electrical signal to detect the position, speed, etc. of the moving part.
  • optical encoders which use light to detect the amount of displacement, can greatly improve detection resolution.
  • Patent Document 1 discloses a detector for an encoder that includes a memory plate with multiple slits formed along the circumferential direction, a fiber that irradiates light toward one open end of the slits, and a light receiving unit that receives the light that has passed through the slits.
  • Non-Patent Document 1 discloses a polarization type encoder consisting of a light source, a rotating polarizing plate, four polarizing plates with different polarization axis directions, and four light receiving elements corresponding to each polarizing plate.
  • This polarization type encoder transmits light from the light source through the rotating polarizing plate and changes it into four different linearly polarized light directions. These four linearly polarized light are then detected by the respective light receiving elements and output as four types of electrical signals to obtain a Lissajous waveform. Then, based on this Lissajous waveform, the displacement angle of the rotating polarizing plate connected to the displacing member is detected.
  • the encoder detection unit disclosed in Patent Document 1 uses a memory plate with slits formed therein to detect the displacement angle, making it difficult to increase the density of the slits formed, and therefore difficult to significantly improve the detection resolution.
  • Non-Patent Document 1 has problems such as low noise resistance and limited locations where it can be used due to external electromagnetic waves, because the polarized light that passes through the rotating polarizing plate is received by a light receiving element and the intensity of each polarized light is transmitted as an electrical signal.
  • This invention has been proposed in consideration of the above problems, and aims to provide a bundle fiber that has high noise resistance against electromagnetic waves and can improve detection resolution when applied to an encoder, a polarization sensor that uses the same, an optical encoder, a light scattering detection sensor, and a method for manufacturing the bundle fiber.
  • a bundle fiber according to a first aspect of the present invention is a bundle fiber having a fiber bundling section bundling a plurality of fibers each having a core and a cladding surrounding the outer periphery of the core, and is characterized in that, on one end side of the fiber bundling section, polarizers having polarization axes oriented differently from each other are formed on the ends of the cores of the individual fibers.
  • Aspect 2 of the present invention is characterized in that in the bundle fiber of aspect 1, the polarizer is a wire grid polarizer in which multiple light-shielding wires are arranged at equal intervals in a striped pattern along one direction.
  • Aspect 3 of the present invention is characterized in that in the bundle fiber of aspect 1 or 2, a fiber separation section is formed on the other end side of the fiber bundling section, in which the fibers are separated one by one.
  • Aspect 4 of the present invention is characterized in that in the bundle fiber of any one of aspects 1 to 3, each of the polarizers is bonded to an end face of each of the cores.
  • Aspect 5 of the present invention is characterized in that in the bundle fiber of any one of aspects 1 to 3, each of the polarizers is integrally formed at the end of each of the cores.
  • Aspect 6 of the present invention is characterized in that, in the bundle fiber of any one of aspects 1 to 5, the number of fibers in the fiber bundling section is N (0 ⁇ N ⁇ 180, N is an integer and a divisor of 180), and the orientation of each polarization axis of the polarizer formed at the end of each of the cores is rotationally symmetrical at (180/N)°.
  • Aspect 7 of the present invention is characterized in that, in the bundle fiber of any one of aspects 1 to 6, at least one of the multiple fibers in the fiber bundling section emits light to the outside from one end side of the fiber bundling section, and at least one of the multiple fibers receives light from one end side of the fiber bundling section.
  • the polarization sensor of aspect 8 of the present invention is characterized in that it includes a bundle fiber of any one of aspects 1 to 7.
  • the optical encoder of aspect 9 of the present invention is characterized in that it has a bundle fiber of any one of aspects 1 to 7, a rotating polarizing plate formed adjacent to one end side of the fiber bundling portion, and a light source that irradiates light toward the rotating polarizing plate.
  • the light scattering detection sensor of aspect 10 of the present invention is characterized by having a bundle fiber of any one of aspects 1 to 7, a detector connected to the bundle fiber, and a light source that irradiates light toward a measurement object.
  • the method for manufacturing a bundle fiber of aspect 11 of the present invention is the method for manufacturing a bundle fiber of aspect 2, characterized in that it includes a resist film forming step of forming a resist film on the surface of a light-transmitting substrate, a lithography step of forming the resist film into a striped resist pattern, and a metal film forming step of forming a metal film on the surface of the light-transmitting substrate using the resist pattern as a mask to obtain a wire grid polarizer having a striped wire grid.
  • Aspect 12 of the present invention is characterized in that in the method for manufacturing a bundle fiber of aspect 11, the light-transmitting substrate is made of the same material as the core that constitutes the fiber.
  • the present invention makes it possible to provide a bundle fiber that has high noise resistance against electromagnetic waves and can improve detection resolution when applied to an encoder, as well as a polarization sensor, optical encoder, light scattering detection sensor, and method for manufacturing the bundle fiber that use the same.
  • FIG. 1 is a schematic diagram showing a bundle fiber according to a first embodiment of the present invention
  • 2 is an enlarged plan view of a main portion showing one end side of a fiber bundling portion in a first embodiment which is an example of the present invention
  • FIG. 10 is an enlarged plan view of a main portion showing one end side of a fiber bundling portion in a fiber bundle according to a second embodiment which is an example of the present invention.
  • FIG. 13A is an enlarged cross-sectional view of a main portion showing one end side of a fiber bundling portion of a fiber bundle according to a third embodiment which is an example of the present invention
  • FIG. 1 is a schematic diagram showing an optical encoder according to an embodiment of the present invention
  • FIG. 13 is a schematic diagram showing an optical encoder according to another embodiment of the present invention.
  • 1A to 1C are schematic diagrams showing, in a step-by-step manner, an example of a process for forming a wire grid polarizer at an end of a core in a method for manufacturing a fiber bundle.
  • FIG. 1A is a design drawing of a chip equipped with a wire grid polarizer
  • FIG. 1B is an enlarged plan view of the fine wires that constitute the wire grid polarizer.
  • 1A is a SEM photograph of an actually manufactured wire grid polarizer
  • FIG. 1B is a magnified photograph of an end face of a bundle fiber to which the actually manufactured wire grid polarizer was bonded. This is a photograph of the appearance of the optical encoder that was actually manufactured.
  • 13 is a graph showing the measurement results for light with a wavelength of 850 nm.
  • FIG. 1 is a schematic diagram showing a bundle fiber according to a first embodiment of the present invention
  • Fig. 2 is an enlarged plan view of a main part showing one end side of a fiber bundling part in the first embodiment of the present invention.
  • the fiber bundle 10 of this embodiment has a fiber bundling portion 11 and a fiber separating portion 12 connected to the other end 11 b of the fiber bundling portion 11 .
  • the fiber bundling portion 11 is configured by bundling a plurality of fibers, four fibers 21A, 21B, 21C, and 21D in this embodiment, with a covering portion 23.
  • the fibers 21A, 21B, 21C, and 21D each have a core 21a, 21b, 21c, and 21d, and a cladding 22a, 22b, 22c, and 22d surrounding the cores 21a, 21b, 21c, and 21d, respectively.
  • Each of the fibers 21A, 21B, 21C, and 21D may be covered with a light-shielding coating 29.
  • the cores 21a, 21b, 21c, and 21d are each molded from a light-transmitting material such as quartz (SiO 2 ), optical glass, or polymer.
  • the cores 21a, 21b, 21c, and 21d are made of quartz.
  • the cores 21a, 21b, 21c, and 21d can be single-mode cores with a diameter of 9 to 10 ⁇ m or multi-mode cores with a diameter of about 50 ⁇ m to 3000 ⁇ m.
  • the claddings 22a, 22b, 22c, and 22d are made of a light-transmitting material such as quartz (SiO 2 ) or a polymer, which has a lower refractive index than the cores 21a, 21b, 21c, and 21d.
  • the claddings 22a, 22b, 22c, and 22d are made of quartz.
  • the covering portion 23 is a bundling member that bundles the four fibers 21A, 21B, 21C, and 21D, and may be made of, for example, a resin that does not transmit light or a thin metal film. In this embodiment, a heat-shrinkable resin is used as the covering portion 23.
  • wire grid polarizers (polarizers) 24a, 24b, 24c, and 24d are provided corresponding to the end faces of the cores 21a, 21b, 21c, and 21d, respectively.
  • a wire grid type polarizer is used as the polarizer, but the polarizer is not limited to a wire grid polarizer.
  • various types of polarizers can be used, such as a crystal type polarizer that controls the polarization components by the birefringence of a crystalline material, a PBS (Polarizing Beam Splitter) type polarizer using an optical multilayer film, a resin polarizer formed by stretching a resin sheet impregnated with a dichroic dye in a certain direction, a Glan-Thompson prism type polarizer that combines calcite prisms to remove linearly polarized components in one direction by total reflection, a photonic crystal type polarizer, a metamaterial/metasurface type polarizer, and a structural birefringence type polarizer.
  • the wire grid polarizers 24a, 24b, 24c, and 24d of this embodiment are made of a light-transmitting base material made of a light-transmitting material containing SiO2 or a light-transmitting material containing a polymer, or a quartz substrate (light-transmitting base material) 26 in this embodiment, on one surface of which a light-shielding material, for example a metal film 27, is formed in a striped pattern.
  • the formation pitch of the individual thin wires 27a of the striped metal film 27 may be, for example, about 140 nm to 250 nm. Furthermore, the width of each thin wire 27a may be about 30 nm to 140 nm, and the thickness (height) may be about 10 nm to 150 nm.
  • wire grid polarizers 24a, 24b, 24c, and 24d are bonded to one end surface of the cores 21a, 21b, 21c, and 21d of the fiber bundling unit 11, respectively.
  • the wire grid polarizer 24a is bonded to the core 21a of the fiber bundling unit 11 so that their centers are aligned.
  • the wire grid polarizer 24a and the core 21a can be bonded by facing the striped metal film 27 that constitutes the wire grid polarizer 24a toward the end face of the core 21a and bonding them with a bonding layer 28 that uses a light-transmitting resin as a bonding material.
  • a light-transmitting ultraviolet-curing resin is used as the bonding material.
  • wire grid polarizers 24b, 24c, and 24d are bonded to one end face of cores 21b, 21c, and 21d of fiber bundling section 11 via bonding layer 28.
  • the wire grid polarizers 24a, 24b, 24c, and 24d are bonded to one end face of the cores 21a, 21b, 21c, and 21d of the fiber bundling section 11, respectively, so that the angles of the extension direction of the striped thin wires 27a are different from each other.
  • the wire grid polarizer 24b is attached at 45°
  • the wire grid polarizer 24c is attached at 90°
  • the wire grid polarizer 24d is attached at 135°.
  • the fiber separation section 12 is connected to the other end 11b of the fiber bundling section 11, and is composed of four single fibers 31A, 31B, 31C, 31D, each of which is made up of a single core 31a, 31b, 31c, 31d, a clad 32a, 32b, 32c, 32d surrounding the outer circumference of each of the four cores, and a coating 29 surrounding the outer circumference of each of the four clads 22.
  • Fiber 31A may be a series of cores in which core 31a is integrally formed with core 21a of fiber bundling section 11.
  • core 31b may be a series of cores integrally formed with core 21b
  • core 31c may be a series of cores integrally formed with core 21c
  • core 31d may be a series of cores integrally formed with core 21d.
  • the light that enters the cores 21a, 21b, 21c, and 21d from one end 11a of the fiber bundling section 11 is branched in the fiber separation section 12 and propagates to the separated fibers 31A, 31B, 31C, and 31D.
  • the one end side 11a of the fiber bundling section 11 may be fixed with a fixing member such as a connector. That is, the bundle fiber 10 may have a fixing member provided on the one end side 11a of the fiber bundling section 11 to fix the multiple fibers.
  • the fiber bundling section 11 is connected to a fiber holder, for example, via the above-mentioned connector.
  • the bundle fiber 10 does not need to have a connector, but in that case, a fixing member may be provided on the outermost periphery near the one end side 11a of the bundle fiber 10, for example, on the outer periphery of the coating section 23, or an optical fiber probe made of a tubular body and housing the bundle fiber 10 inside may be provided. This allows the multiple fibers and the multiple polarizers to be firmly fixed to each other, making it possible to increase the accuracy of setting the angle of each polarizer.
  • the wire grid polarizers 24a, 24b, 24c, and 24d maximize the transmittance of polarized light at an angle perpendicular to the extension direction of each striped thin wire (wire) 27a, and minimize the transmittance of polarized light at an angle along the extension direction of the thin wire (wire) 27a.
  • Four polarized lights with different angular components of the strongest light intensity are then emitted from the end faces of the cores 31a, 31b, 31c, and 31d of the fibers 31A, 31B, 31C, and 31D, respectively, separated by the wire grid polarizers 24a, 24b, 24c, and 24d.
  • the light incident on one end side 11a of the fiber bundling section 11 is split into polarized light beams with different angles by the wire grid polarizers 24a, 24b, 24c, and 24d, making it easy to obtain multiple polarized lights with different angle components.
  • the polarized light separated into its respective angular components by the wire grid polarizers 24a, 24b, 24c, and 24d is propagated as polarized light through the fibers 31A, 31B, 31C, and 31D without being converted into an electrical signal by a light receiving element as in the conventional case and then transmitted, so that the signal is not affected by external electromagnetic waves, etc., which would cause noise in an electrical signal.
  • This makes it highly resistant to noise, and makes it possible to detect the polarization of each angular component separated by the wire grid polarizer with high accuracy, even in places with strong external electromagnetic waves.
  • four cores are formed in the fiber bundling section, and four wire grid polarizers are provided with thin wires whose angles are offset by 45° from each other; however, the number of wire grid polarizers and the number of cores in the fiber bundling section are not limited.
  • three cores may be formed in the fiber bundle section, and three wire grid polarizers may be provided, with the wires offset by 60 degrees from each other. In this case, the cost of the bundle fiber can be reduced.
  • six cores may be formed in the fiber bundling section, and six wire grid polarizers may be provided, with the wires offset from each other by 30°. In this case, the accuracy of detecting the polarization of each angle component can be further improved.
  • the number of fibers in the fiber bundling section may be N (0 ⁇ N ⁇ 180, N is an integer and a divisor of 180).
  • the orientation of the polarization axis of each of the polarizers formed at the end of the cores of the N fibers is rotationally symmetrical with respect to (180°/N).
  • each polarizer is arranged in an orientation that divides 180° into N, and the number N of the fibers may be an even number or an odd number. In this way, by increasing the number N of fibers in the fiber bundling section, the detection accuracy can be further improved.
  • FIG. 3 is an enlarged plan view of a main portion showing one end side of a fiber bundling portion in a fiber bundle according to a second embodiment of the present invention.
  • the fiber bundling portion 41 of the fiber bundle 40 of this embodiment is configured by bundling a plurality of fibers, four fibers 51A, 51B, 51C, and 51D in this embodiment, with a coating portion 23 (see FIG. 1).
  • the fibers 51A, 51B, 51C, and 51D each have a core 51a, 51b, 51c, and 51d, and a cladding 52a, 52b, 52c, and 52d surrounding the core 51a, 51b, 51c, and 51d, respectively.
  • the configurations of the cores 51a, 51b, 51c, and 51d and the clads 52a, 52b, 52c, and 52d are the same as in the first embodiment.
  • Wire grid polarizers 54a, 54b, 54c, and 54d are integrally formed at the ends of the cores 51a, 51b, 51c, and 51d, which are the end side 11a of the fiber bundling section 11.
  • the wire grid polarizers 54a, 54b, 54c, and 54d of this embodiment are formed by depositing a metal film 57 in a striped pattern directly on the ends of the cores 51a, 51b, 51c, and 51d.
  • the configuration of the metal film 57 of this embodiment is the same as that of the first embodiment.
  • a light-transmitting protective film 58 that protects the fine wires 57a is formed on each of the wire grid polarizers 54a, 54b, 54c, and 54d so as to cover the striped metal film 57.
  • the protective film 58 may be made of any light-transmitting material, and in this embodiment, a light-transmitting ultraviolet-curing resin is used.
  • the thin wires (wires) 57a of the metal film 57 constituting the wire grid polarizers 54a, 54b, 54c, and 54d are directly deposited on one end of the cores 51a, 51b, 51c, and 51d, respectively. This eliminates concerns about angle misalignment during bonding, compared to a configuration in which wire grid polarizers are formed separately from the cores and then bonded, and makes it possible to obtain a highly accurate bundle fiber 40 with fewer manufacturing steps.
  • FIG. 4(a) is an enlarged cross-sectional view of a main part showing one end side of a fiber bundling part in a fiber bundle according to a third embodiment of the present invention
  • Fig. 4(b) is an enlarged plan view of a main part showing the end side of Fig. 4(a).
  • the fiber bundling portion 61 of the fiber bundle 60 of this embodiment is configured by bundling a plurality of fibers 71A and 71B (two fibers in this embodiment) with a coating portion 23.
  • the fibers 71A and 71B each have a core 71a and 71b, and a cladding 72a and 72b surrounding the core 71a and 71b, respectively.
  • the fiber bundling portion 61 constitutes a multi-core fiber in which the two fibers 71A, 71B are arranged at equal intervals inside the coating portion 23.
  • One end 61a of the fiber bundling portion 61 is provided with wire grid polarizers 74a and 74b that correspond to the end faces of the cores 71a and 71b, respectively.
  • the wire grid polarizers 74a and 74b of this embodiment are formed by forming metal films 77 in a striped pattern on the ends of the cores 71a and 71b, respectively.
  • the wire grid polarizers 74a and 74b each have a protective film 78 that covers the fine wires 77a that make up the metal film 77.
  • the wire grid polarizers 74a and 74b may be formed by forming a metal film in stripes on one surface of a quartz substrate, as in the first embodiment, and bonding the stripes to the ends of the cores 71a and 71b, respectively.
  • the wire grid polarizers 74a and 74b are arranged so that the angles of the extension direction of the striped thin wires (wires) 77a are different from each other. In other words, when the angle perpendicular to the extension direction of the striped thin wires 77a of the wire grid polarizer 74a is set to 0°, the wire grid polarizer 74b is attached so that it is at 90°.
  • the fiber bundle 60 of this embodiment as described above can be used, for example, as a detector for a sensor that detects the surface condition of a material. As shown in FIG. 4(a), when visible light is emitted from the core 71a at one end 61a of the fiber bundling section 61, only the polarized light with the strongest component at an angle of 0° is emitted as inspection light toward the material M to be inspected by the wire grid polarizer 74a.
  • this inspection light When this inspection light is reflected from the surface of material M, it produces specularly reflected light and diffusely reflected light depending on the surface condition (reflectance, surface roughness) of material M.
  • wire grid polarizer 74b selectively transmits only the diffusely reflected light, and propagates the incident diffusely reflected light through core 71b. Therefore, the surface condition of material M can be detected by measuring the diffusely reflected light propagating through core 71b.
  • the bundle fiber 60 of this embodiment can be used as a detection sensor to detect the surface condition of a material, for example, by measuring the ratio of near-infrared light to visible light based on the difference in reflectance between visible light and near-infrared light, which differs depending on the material.
  • FIG. 5 is a schematic diagram showing an optical encoder according to an embodiment of the present invention.
  • the optical encoder 80 of this embodiment includes the bundle fiber 10 of the first embodiment, a rotating polarizing plate 81 formed adjacent to one end side 11a of the fiber bundling portion 11 of this bundle fiber 10, a light source 82 that irradiates light toward this rotating polarizing plate 81, and a control unit 83 that receives polarized light respectively emitted from the four fibers 31A, 31B, 31C, and 31D that constitute the fiber separation portion 12 of the bundle fiber 10 and calculates the rotation angle of the rotating polarizing plate 81 according to changes in the amount of light.
  • the light source 82 may be, for example, a non-polarized light source device such as an LED or a tungsten halogen light source. Such a light source 82 may further include an optical lens such as a focusing lens.
  • the rotating polarizer 81 only needs to have its rotation axis 81m connected to a detection target that detects the rotation of a mechanically movable part.
  • a rotating polarizer 81 may be, for example, a circular transparent substrate on which material molecules are oriented, a wire grid polarizer, a photonic crystal type polarizer, a metamaterial metasurface type polarizer, or a structural birefringence type polarizer.
  • a resin rotating polarizer is used, in which iodine compound molecules are adsorbed and oriented on a light-transmitting resin disk.
  • the control unit 83 is composed of light receiving elements that detect the amount of polarized light emitted from each of the four fibers 31A, 31B, 31C, and 31D, and a computer (PC) that calculates the rotation angle of the rotating polarizing plate 81 based on the amount of four polarized light beams detected by these light receiving elements at different angles.
  • PC computer
  • the optical encoder 80 configured as described above, when the rotating polarizer 81 is stopped and a constant amount of light is irradiated from the light source 82, the output polarized light (detection light) that passes through the rotating polarizer 81 is polarized by the wire grid polarizers 24a, 24b, 24c, and 24d in an amount according to its angular component, and is propagated through the end faces of the cores 21a, 21b, 21c, and 21d.
  • Fiber 31A of fiber separation section 12 emits polarized light with the strongest component at an angle of 0°.
  • fiber 31B emits only polarized light with the strongest component at an angle of 45°
  • fiber 31C emits only polarized light with the strongest component at an angle of 90°
  • fiber 31D emits only polarized light with the strongest component at an angle of 135°.
  • the rotating polarizer 81 rotates via the rotation axis 81m.
  • the angular component of the output polarized light (detection light) that passes through the rotating polarizer 81 changes.
  • the amount of polarized light that passes through each of the wire grid polarizers 24a, 24b, 24c, and 24d changes in accordance with the change in the angular component of the output polarized light (detection light).
  • the control unit 83 detects the degree to which the detection object has rotated by calculating the rotation angle of the rotating polarizing plate 81 according to the change in the amount of polarized light emitted from each of the four fibers 31A, 31B, 31C, and 31D.
  • the optical encoder 80 of this embodiment is not affected by external electromagnetic noise by transmitting light through the fibers 31A, 31B, 31C, and 31D to the control unit 83 that calculates the rotation angle. Therefore, it can be suitably used, for example, as an encoder for detecting the motion of robots for medical, industrial, and aerospace use, or as an encoder for detecting the mechanical motion of equipment placed in an environment with strong electromagnetic waves.
  • the light source 82 is arranged so that light passes through the rotating polarizer 81, but the light source is not limited to this.
  • a fiber bundle 90 having a fiber bundling section 92 housing five fibers 91A, 91B, 91C, 91D, and 91E can be used, with four of the fibers 91A, 91B, 91C, and 91D used to propagate the output polarized light (detection light) as described above, and one fiber 91E used to emit light incident from a light source connected to the other end.
  • a reflective rotating polarizer 93 with a light-reflecting film formed on the back side can be used. This configuration can further reduce the size and weight of the optical encoder.
  • FIG. 7 is a schematic diagram showing the steps of the manufacturing method of a fiber bundle up to the formation of a wire grid polarizer at the end of the core.
  • a substrate made of a glass material containing SiO2 for example a quartz substrate 26, is prepared, and an electron beam (EB) resist film 102 is formed on one surface of the quartz substrate 26 by a film forming method such as spin coating (resist film forming process: see FIG. 7(a)).
  • EB electron beam
  • the EB resist film 102 is subjected to EB lithography to obtain a resist pattern 103 in the form of solidified stripes on one surface of the quartz substrate 26 (lithography step: see FIG. 7B).
  • EB lithography is used as the lithography process, but other methods such as nanoimprint lithography or lithography using a stepper may also be used, and the lithography method is not limited to this.
  • a metal film for example an aluminum film, is formed on the surface of the quartz substrate 26 by, for example, electron beam deposition.
  • a metal film for example, gold, silver, copper, platinum, etc. can also be used as the metal film.
  • the metal film 27 is deposited in a striped pattern on the portion of the surface of the quartz substrate 26 that is exposed from the striped resist pattern 103, and numerous fine lines (wires) 27a are formed on the surface of the quartz substrate 26 (see FIG. 7(c)). Thereafter, the striped resist pattern 103 is removed to obtain a wire grid polarizer (assembly) 24 having the striped metal film 27 (metal deposition process: see FIG. 7(d)).
  • the wire grid polarizer (aggregate) 24 can be formed by a procedure other than that described above.
  • a metal film can be formed on the surface of a quartz substrate, a striped resist pattern can be formed on this metal film by lithography, the metal film is etched using this resist pattern as an etching mask, and then the resist pattern can be removed to form a wire grid polarizer (aggregate) having a striped metal film.
  • this wire grid polarizer (aggregate) 24 is diced to a size that allows it to be attached to the core (see FIG. 7(e)). Then, a bonding material, for example a transparent UV-curable resin R, is applied to the small pieces 24S on which the wire grid polarizers 24a, 24b, 24c, and 24d are formed (see FIG. 7(f)).
  • a bonding material for example a transparent UV-curable resin R
  • the pieces are then positioned on the end faces of the cores 21a, 21b, 21c, and 21d of the fiber bundling section 11, and then irradiated with UV light, thereby manufacturing a bundle fiber 10 in which the wire grid polarizers 24a, 24b, 24c, and 24d are bonded to the end faces of the cores 21a, 21b, 21c, and 21d via the bonding layer 28 (see FIG. 7(g)).
  • the small piece 24S on which the wire grid polarizers 24a, 24b, 24c, and 24d are formed may be further formed into chips for each of the wire grid polarizers 24a, 24b, 24c, and 24d, and each chip may be individually bonded to the end face of the cores 21a, 21b, 21c, and 21d.
  • the bundle fiber of this embodiment can be used in a light scattering detection sensor.
  • the light scattering detection sensor has a bundle fiber, a detector connected to the bundle fiber, and a light source that irradiates light toward the measurement target.
  • the light scattering detection sensor detects information on the direction and intensity of the polarization.
  • the configuration of the bundle fiber can be the same as the configuration of the bundle fiber provided in the encoder.
  • the number of fibers in the fiber bundling section of the bundle fiber may be N (0 ⁇ N ⁇ 180, N is an integer and a divisor of 180), and the detection accuracy can be further improved by increasing the number N of fibers in the fiber bundling section.
  • the object to be measured is a non-scattering object such as a mirror
  • the incident light (linearly polarized) is reflected while maintaining its linear polarization state, and therefore cannot pass through a polarizer oriented 90 degrees from the polarization direction.
  • a linearly polarized light source is irradiated onto a scattering object, the light is diffusely reflected, and the reflection direction is also reflected at an angle other than regular reflection, and at the same time, the direction of polarization changes and the light is reflected with various components with different polarization directions.
  • the bundle fiber of this embodiment can be used as a polarization sensor such as an encoder or a light scattering detection sensor.
  • the polarization sensor is equipped with a bundle fiber, it can also be used as a sensor other than an encoder and a light scattering detection sensor.
  • the intensity of the light (non-polarized light) emitted from the light source 82 when it passes through the rotating polarizing plate 81 is set as I0 , and the intensities of the polarized light after passing through the four-directional wire grid polarizers (WGPs) 24a, 24b, 24c, and 24d are set as I1 , I2 , I3 , and I4 .
  • WGPs wire grid polarizers
  • I1 I0 (1+cos2( ⁇ + ⁇ ))/2 (1)
  • I2 I0 (1+sin2( ⁇ + ⁇ ))/2 (2)
  • I 3 I 0 (1-cos2( ⁇ + ⁇ ))/2 (3)
  • I4 I0 (1 - sin2 ( ⁇ + ⁇ )) / 2 ... (4)
  • ⁇ is determined by equation (5).
  • ⁇ Arctan 2(I 1 ⁇ I 3 , I 2 ⁇ I 4 ) ⁇ (5)
  • Fig. 8(a) is a design drawing of the chip
  • Fig. 8(b) is an enlarged plan view of the thin wires that make up the WGP.
  • the bundle fiber used was a bundle fiber (BF74LS01: manufactured by Thorlabs Japan Co., Ltd.) consisting of seven fibers bundled together.
  • the ferrule diameter was 3.2 mm, and the tip was 2 mm square.
  • the WGP was a circle with a diameter of 0.43 mm so that the end face of the core with a diameter of 0.4 mm was covered.
  • the width of each wire was 80 nm, the height was 30 nm, and the formation pitch between the wires was set to 180 nm.
  • Fig. 9(a) shows an SEM photograph of the WGP that was actually fabricated.
  • the white thin lines are Al wires, and the grey area between them is the glass substrate (SiO 2 ) that serves as the base. From the SEM photograph of FIG. 9(a), it was confirmed that the width of one wire was 74 nm.
  • the glass substrate on which the obtained WGP was formed was diced into small pieces of 2 mm square. Then, the small pieces were aligned so that the WGP overlapped each core of one end face of the bundle fiber.
  • FIG. 9(b) shows an enlarged photograph of the end face of the bundle fiber to which the WGP was actually bonded.
  • Light (unpolarized light) was irradiated from the light source onto a rotating polarizer and incident on one end of a fiber bundle equipped with wire grid polarizers in four directions. The intensity of the light transmitted through each of the wire grid polarizers in the four directions was then measured while changing the angle of the rotating polarizer.
  • Measurements were performed by irradiating the end face of the bundle fiber with parallel light from the light source via an optical fiber and a collimating lens, and rotating the rotating polarizer by 10° at a time.
  • a spectrometer HR4000CG-UV-NIR: manufactured by Ocean Photonics, Inc. was connected to the other end of the bundle fiber, i.e., to each of the four fibers separated for each core, to measure the intensity of the polarized light.
  • FIG. 11 A graph of the measurement results for light with a wavelength of 850 nm, for which a commercially available LED light source can be used, is shown in Figure 11.
  • the measurement results for the wire grid polarizer in four directions were normalized so that the maximum intensity was 1 and the minimum intensity was 0.
  • the measurement results were almost consistent with the theoretical values (calculated values) when the intensity I0 was set to 1 and the initial tilt angle ⁇ was set to 31.2° in the above-mentioned formulas (1) to (4).
  • the fiber bundle of the present invention and the optical encoder using the same can be used as a motion detection sensor for devices installed in locations with strong external electromagnetic waves, for medical, industrial, and aerospace robots, and as a detection sensor for the rotation angle of devices that are easily affected by electromagnetic waves. Therefore, it has industrial applicability.
  • REFERENCE SIGNS LIST 10 ... fiber bundle 11... fiber bundling section 12... fiber separation section 21A, 21B, 21C, 21D... fibers 21a, 21b, 21c, 21d... cores 22a, 22b, 22c, 22d... cladding 23... coating section 24a, 24b, 24c, 24d... wire grid polarizer

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PCT/JP2022/041257 2022-11-04 2022-11-04 バンドルファイバ、偏光センサ、光学式エンコーダ、光散乱検出センサおよびバンドルファイバの製造方法 Ceased WO2024095488A1 (ja)

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