Optical probe

Abstract

To provide an optical probe that can easily perform alignment and joining operations at low cost when manufacturing the optical probe. [Solution] The optical probe 1 includes an optical member 2 having an optical element 21 and a reflector 22 that change the polarization state of light passing through in response to the strength of an external electric or magnetic field, a collimator lens 3, an optical fiber 4, a ferrule 5 that holds the optical fiber 4 therein, and a holding mechanism 6 that holds the optical member 2, the collimator lens 3, and the ferrule 5. The holding mechanism 6 includes a sleeve 61 that holds the ferrule 5 therein, a lens holder 62 that holds the collimator lens 3 therein, and an optical member holder 63 that holds the optical member 2 therein. Each of the sleeve 61, the lens holder 62, and the optical member holder 63 is formed from an insulating, low-dielectric, and thermoplastic material.

Description

[Technical Field]

[0001] The present invention relates generally to optical probes, and more particularly to optical probes that include a ferrule for holding an optical fiber, a collimator lens, and a holding mechanism for holding an optical member. [Background technology]

[0002] Conventionally, optical probes using electro-optical crystals whose birefringence changes depending on the strength of an external electric field or magneto-optical crystals having a magneto-optical effect (Faraday effect) have been known. For example, Patent Document 1 discloses an optical probe 100 as shown in FIG. 1. The optical probe 100 includes an optical member 130 including an optical element 110 whose polarization state of light passing through changes depending on the strength of an external electric field or magnetic field and a reflector 120 such as a dielectric reflective film or a mirror provided on the tip surface of the optical element 110; a collimator lens 140 for collimating light incident on the optical element 110 and further collecting the light reflected from the reflector 120; an optical fiber 150 that emits the incident light to the collimator lens 140 and into which the reflected light collected by the collimator lens 140 is incident; and a ferrule 160 that holds the optical fiber 150 therein.

[0003] The polarization state of light passing through the optical element 110 changes depending on the strength of the external electric field or external magnetic field 200. Light emitted from the optical fiber 150 and incident on the optical element 110 is collimated by the collimator lens 140 and then enters the optical element 110. The incident light that enters the optical element 110 passes through the optical element 110 and is reflected by the reflector 120. The reflected light that is reflected by the reflector 120 passes through the optical element 110, exits the optical element 110, is collected by the collimator lens 140, and enters the optical fiber 150 held in the ferrule 160. The light passing through the optical element 110 is polarized depending on the strength of the external electric field or external magnetic field 200, so the strength of the external electric field or external magnetic field 200 can be measured by detecting the polarization state of the reflected light that enters the optical fiber 150.

[0004] In such an optical probe 100, in order to increase the intensity of the reflected light incident into the optical fiber 150, it is necessary to perform accurate alignment (centering) of the optical member 130, the collimator lens 140, and the ferrule 160 that holds the optical fiber 150. Furthermore, since the polarization state of light passing through the optical element 110 changes depending on the strength of the external electric field or external magnetic field 200, if a member made of a conductive material is placed around the optical element 110, the member will function as an electromagnetic shield against the external electric field or external magnetic field, affecting the change in the polarization state of the light passing through the optical element 110. Furthermore, if a member made of a highly dielectric material is placed around the optical element 110, the member will be polarized by the external electric field or external magnetic field 200, affecting the change in the polarization state of the light passing through the optical element 110.

[0005] Therefore, holding members such as sleeves made of conductive or highly dielectric materials, such as stainless steel or metal, commonly used for aligning a ferrule that holds an optical fiber and a collimator lens cannot be used in optical probes. Furthermore, conventional methods for manufacturing optical probes require an alignment process to accurately align the ferrule that holds the optical fiber, the collimator lens, and the optical components, followed by a joining process to bond them together with an adhesive. However, these alignment and joining processes require extremely high precision and are therefore time-consuming and costly. Therefore, there has been a need for an easy and inexpensive alignment and joining process for manufacturing optical probes. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Japanese Patent Application Laid-Open No. 2009-115497 Summary of the Invention [Problem to be solved by the invention]

[0007] The present invention has been made in consideration of the above-mentioned conventional problems, and its object is to provide an optical probe that allows for easy and low-cost alignment and joining operations when manufacturing the optical probe. [Means for solving the problem]

[0008] These objects can be achieved by the present invention, which is defined by the following (1) to (8). (1) An optical member including an optical element that changes the polarization state of light passing through it depending on the strength of an external electric field or an external magnetic field, and a reflector provided on a tip surface of the optical element; a collimator lens for collimating the light incident on the optical element and for collecting the light reflected from the reflector; an optical fiber that emits the incident light toward the collimator lens and into which the reflected light collected by the collimator lens is incident; a ferrule that holds the optical fiber therein; a holding mechanism for holding the optical member, the collimator lens, and the ferrule, The holding mechanism includes: a cylindrical sleeve that holds the ferrule therein; a cylindrical lens holder provided on a tip end surface of the sleeve and holding the collimator lens therein; a cylindrical optical element holder provided on a tip end surface of the lens holder and holding the optical element therein; The optical probe is characterized in that the sleeve, the lens holder, and the optical element holder are each formed of an insulating, low-dielectric, and thermoplastic material.

[0009] (2) An optical probe as described in (1) above, in which the sleeve and the lens holder, and the lens holder and the optical element holder are laser welded together, thereby integrating the sleeve, the lens holder, and the optical element holder with each other.

[0010] (3) The optical probe according to (2) above, wherein the laser welding between the sleeve and the lens holder and between the lens holder and the optical element holder is spot welding.

[0011] (4) The optical probe according to (1) above, wherein the sleeve, the lens holder, and the optical element holder are each formed of polyacetal resin.

[0012] (5) A transparent member formed of a transparent insulating and low-dielectric material is further provided, the optical element holder includes a cylindrical main body, a storage recess formed on a base end surface of the main body, and an opening penetrating a bottom surface of the storage recess; the transparent member is fixed on the bottom surface of the storage recess, The optical probe according to (1) above, wherein the optical member is located within the opening and fixed on the transparent member.

[0013] (6) The optical probe according to (5) above, wherein the optical element is in contact with the transparent member and the reflector is fixed on the transparent member so as to face the outside through the opening.

[0014] (7) The optical probe according to (1) above, wherein the ferrule and the sleeve are laser-welded together, thereby fixing the ferrule to the sleeve.

[0015] (8) The optical probe according to (1) above, wherein the holding member holds the optical element, the collimator lens, and the optical fiber in a state where the optical element, the collimator lens, and the optical fiber are aligned. [Effects of the Invention]

[0016] In the optical probe of the present invention, the optical element, the collimator lens, and the optical fiber are held by the sleeve, the lens holder, and the optical element holder of the holding mechanism, respectively. By using such a holding mechanism, the alignment and joining operations when manufacturing the optical probe are facilitated. Furthermore, because the alignment and joining operations are facilitated, the time and cost required for the alignment and joining operations are reduced, allowing for a lower cost optical probe.

[0017] Furthermore, because the sleeve, lens holder, and optical element holder of the holding mechanism are each made of insulating and low-dielectric materials, they are shielded from external electric or magnetic fields and are not polarized by the external electric or magnetic fields. As a result, the holding mechanism is prevented from affecting the polarization state of light passing through the optical element, improving the detection accuracy of the optical probe. [Brief explanation of the drawings]

[0018] [Figure 1] FIG. 1 is a schematic diagram showing the configuration of a conventional optical probe. [Figure 2] FIG. 1 is a perspective view of an optical probe according to an embodiment of the present invention. [Figure 3] FIG. 3 is a cross-sectional view of the optical probe shown in FIG. 2. [Figure 4] FIG. 3 is an exploded perspective view of the optical probe shown in FIG. 2. [Figure 5] FIG. 5 is a cross-sectional view of the ferrule shown in FIG. 4. [Figure 6] FIG. 5 is a cross-sectional view of the lens holder shown in FIG. [Figure 7] 3 is a flowchart showing a method for manufacturing the optical probe shown in FIG. 2. [Figure 8] 8 is a flowchart showing the alignment operation shown in FIG. 7. [Figure 9] FIG. 8 is a schematic diagram showing an inspection system used in the alignment work shown in FIG. 7. DETAILED DESCRIPTION OF THE INVENTION

[0019] The optical probe and the method for manufacturing the optical probe of the present invention will be described below based on the preferred embodiments shown in the accompanying drawings. The drawings referred to below are schematic diagrams prepared for the purpose of explaining the present invention. The dimensions (length, width, thickness, etc.) of each component shown in the drawings do not necessarily reflect the actual dimensions. In addition, the same reference numerals are used for the same or corresponding components in each drawing. In the following description, the positive direction of the Z axis is referred to as the "tip side", the negative direction of the Z axis is referred to as the "base side", and the Z direction is sometimes referred to as the "light transmission direction". In the following description, the term "low dielectric material" refers to a material having a relative dielectric constant of 10 6 This refers to materials with a resistance of 4.0 Hz or less to electromagnetic waves.

[0020] <Electromagnetic-Optical Probe> First, an optical probe according to an embodiment of the present invention will be described in detail with reference to Figs. 2 to 6. Fig. 2 is a perspective view of the optical probe according to the embodiment of the present invention. Fig. 3 is a cross-sectional view of the optical probe shown in Fig. 2. Fig. 4 is an exploded perspective view of the optical probe shown in Fig. 2. Fig. 5 is a cross-sectional view of the ferrule shown in Fig. 4. Fig. 6 is a cross-sectional view of the lens holder shown in Fig. 4.

[0021] The optical probe 1 according to the embodiment of the present invention shown in Fig. 2 is used to detect the strength of an external electric field or external magnetic field in an area where the tip of the optical probe 1 is located. By bringing the tip of the optical probe 1 close to a detection target, the strength of the external electric field or external magnetic field generated by a current flowing in the detection target can be detected, and a non-contact inspection can be performed to inspect the current flowing in the detection target based on the detected strength of the external electric field or external magnetic field. Typically, the optical probe 1 can be used to non-contact inspect the current flowing in wiring connecting a semiconductor IC and a circuit board.

[0022] As shown in Figure 4, the optical probe 1 includes an optical member 2 having an optical element 21 whose polarization state of light passing through changes depending on the strength of an external electric field or magnetic field and a reflector 22 provided on the tip surface of the optical element 21, a collimator lens 3 that collimates the light incident on the optical element 21 and further collects the light reflected from the reflector 22, an optical fiber 4 that emits the incident light to the collimator lens 3 and into which the reflected light collected by the collimator lens 3 is incident, a ferrule 5 that holds the optical fiber 4 inside, a holding mechanism 6 that holds the optical member 2, the optical member 2, the collimator lens 3, and the ferrule 5, and a transparent member 7 made of a transparent, insulating, and low-dielectric material (e.g., quartz glass).

[0023] Incident light (typically, completely circularly polarized laser light) having a known initial polarization state emitted from a laser light source (not shown) is incident on the core 41 of the optical fiber 4. The incident light emitted from the core 41 of the optical fiber 4 is collimated by the collimator lens 3 and then incident on the optical element 21. The incident light then passes through the optical element 21 and is reflected by the reflector 22. The reflected light from the reflector 22 passes through the optical element 21 and then emerges from the optical element 21. The reflected light is then collected by the collimator lens 3 and incident on the core 41 of the optical fiber 4. The polarization state of the light passing through the optical element 21 changes depending on the strength of the external electric field or external magnetic field in the region where the tip of the optical probe 1 is located, so that the polarization state of the reflected light changes from the initial polarization state of the incident light. The reflected light that has propagated through the core 41 of the optical fiber 4 is separated from the incident light by an optical circulator (not shown) and then detected by a detection device (not shown). The strength of the external electric field or external magnetic field is calculated based on the polarization state of the reflected light.

[0024] The optical member 2 receives incident light collimated by the collimator lens 3 and emits reflected light toward the collimator lens 3. The optical member 2 includes an optical element 21 and a reflector 22 provided on the tip surface of the optical element 21. The optical element 21 has a property of changing the polarization state of light passing through the optical element 21 depending on the strength of an external electric field or magnetic field in the area where the optical element 21 is located. An electro-optical crystal or a magneto-optical crystal can be used as the optical element 21. In one example, a substantially rectangular parallelepiped member made of an electro-optical crystal such as CaTe, BiSiO2, or LiNO3 can be used as the optical element 21. An electro-optical crystal has a property that its birefringence changes depending on the strength of an external electric field in the area where the electro-optical crystal is located. Therefore, an electro-optical crystal can be suitably used as the optical element 21. Alternatively, an organic electro-optical polymer (EO polymer), which is a polymer in which dye molecules having an electro-optical (EO) effect are bonded and dispersed, may be used as the optical element 21 instead of an electro-optical crystal. In another example, a substantially rectangular parallelepiped member made of a magneto-optical crystal, such as a Bi-substituted YIG (yttrium iron garnet) thin film crystal, a TGG (terbium gallium garnet) crystal, or a TSAG (terbium scandium aluminum garnet) crystal, can be used as the optical element 21. Magneto-optical crystals have a magneto-optical effect (Faraday effect) in which the polarization state of light passing through the magneto-optical crystal changes depending on the strength of the external magnetic field in the region where the magneto-optical crystal is located. Therefore, magneto-optical crystals can be suitably used as the optical element 21. The distal and proximal end faces of the optical element 21 are flat surfaces perpendicular to the Z direction. In one example, a rectangular parallelepiped organic nonlinear optical crystal, DAST (4-N,N-dimethylamino-4'-N'-methylstilbazolium tosylate), is suitably used as the optical element 21. Because the nonlinear optical crystal DAST has a very large nonlinear optical constant, the birefringence of the nonlinear optical crystal DAST changes with high sensitivity to changes in the strength of the external electric field. Therefore, by using the organic nonlinear optical crystal DAST as the optical element 21, the sensitivity of the optical probe 1 can be improved.The polarization state of light passing through the optical element 21 changes depending on the strength of the external electric or magnetic field in the region (field) where the optical element 21 is located.

[0025] The reflector 22 is a plate-like or film-like member fixedly provided on the tip surface of the optical element 21. The reflector 22 has the function of reflecting the incident light that is incident on the optical element 21 from the collimator lens 3 and passes through the optical element 21. The reflector 22 may be a dielectric reflective film deposited on the tip surface of the optical element 21, or may be any reflective member such as a mirror fixed to the tip surface of the optical element 21 by any fixing means such as an adhesive. The reflected light from the reflector 22 passes through the optical element 21, exits the optical element 21, and is collected by the collimator lens 3. Note that because the incident light that enters the optical element 21 is collimated light, the reflected light that exits the optical element 21 is also collimated light. Since the reflected light that exits the optical element 21 passes through the optical element 21, it is polarized by the optical element 21. Therefore, the polarization state of the reflected light that exits the optical element 21 changes from the initial polarization state of the incident light depending on the strength of the external electric field.

[0026] The collimator lens 3 collimates the incident light emitted from the optical fiber 4 and further collects the reflected light emitted from the optical element 21, causing the light to enter the core 41 of the optical fiber 4. Note that in the illustrated embodiment, the collimator lens 3 is composed of a single lens, but the present invention is not limited to this. The collimator lens 3 may be composed of a combination of one or more spherical lenses or aspherical lenses, or a gradient index lens, a diffractive lens, or a metalens may be used. The incident light emitted from the core 41 of the optical fiber 4 to the collimator lens 3 is collimated by the collimator lens 3 and enters the base end surface of the optical element 21. The reflected light reflected by the reflector 22 and emitted from the base end surface of the optical element 21 to the collimator lens 3 is collected by the collimator lens 3 and enters the core 41 of the optical fiber 4.

[0027] The optical fiber 4 includes a core 41 and a cladding 42 surrounding the core 41, and is used to transmit incident and reflected light. The optical fiber 4 is a polarization-maintaining fiber, and the polarization states of the incident and reflected light propagating through the optical fiber 4 do not change during propagation through the optical fiber 4. If necessary, the optical fiber 4 may include a primary coating, a buffer layer, and a secondary coating located outside the cladding 42. The type of the optical fiber 4 is not particularly limited, and the optical fiber 4 may be a step-index (SI) optical fiber or a graded-index (GI) optical fiber. The optical fiber 4 is positioned such that the distance between the distal end face of the core 41 and the collimator lens 3 is equal to the working distance of the collimator lens 3, and the center of the distal end face of the core 41 is located on the optical axis of the collimator lens 3. The proximal end of the optical fiber 4 is typically optically connected to an optical circulator. Therefore, the optical circulator can separate incident light that enters the core 41 from the base end side from the light source via the optical circulator from reflected light that enters the core 41 from the tip end side via the collimator lens 3. The detection device can calculate the strength of the external electric field or magnetic field by detecting the polarization state of the reflected light separated by the optical circulator.

[0028] The optical member 2, collimator lens 3, and optical fiber 4 are aligned (centered) so that the center of the base end face of the optical element 21 and the center of the tip face of the core 41 of the optical fiber 4 are positioned on the optical axis of the collimator lens 3. Furthermore, the optical member 2, collimator lens 3, and optical fiber 4 are aligned so that the optical axis of the collimator lens 3 is perpendicular to the base end face of the optical element 21 and the tip face of the core 41 of the optical fiber 4. With this configuration, the optical paths of the incident light emitted from the core 41 of the optical fiber 4 and the reflected light incident on the core 41 of the optical fiber 4 are approximately the same, minimizing reduction in the intensity of the reflected light due to losses such as scattering.

[0029] The ferrule 5 is a cylindrical member formed of an insulating, low-dielectric, and thermoplastic material, such as polyacetal (or polyoxymethylene) resin, polypropylene, polyethylene, polystyrene, acrylic, polyamides including nylon 6 and nylon 66, polyethylene terephthalate, polybutylene terephthalate, acrylonitrile butadiene styrene, polyether ether ketone, cycloolefin polymer, polycarbonate, polyphenylene sulfide, polyetherimide, vinyl chloride, vinylidene chloride, butyral, vinyl acetate, or polybutylene. The ferrule 5 functions to hold an optical fiber 4 therein. As shown in FIGS. 4 and 5 , the ferrule 5 includes a cylindrical main body 51 and a through-hole 52 that linearly penetrates the main body 51 in the Z direction. The main body 51 includes a straight portion 511 that extends linearly in the Z direction and a tapered portion 512 that extends from the tip of the straight portion 511 toward the tip. The straight portion 511 is a cylindrical portion extending linearly in the Z direction. The outer diameter of the straight portion 511 is constant along the Z direction. The base end surface of the straight portion 511 is a flat surface perpendicular to the Z direction. The tapered portion 512 is a truncated cone-shaped portion extending from the tip end of the straight portion 511 toward the tip side. The outer diameter of the tapered portion 512 gradually decreases from the base end toward the tip side. The outer diameter of the base end of the tapered portion 512 is equal to the outer diameter of the straight portion 511, and the base end of the tapered portion 512 is continuous with the outer peripheral surface of the straight portion 511. The tip surface of the tapered portion 512 is a flat surface perpendicular to the Z direction. In order to reduce reflected back light at the tip surface of the tapered portion 512, additional measures may be taken, such as tilting the tip of the tapered portion 512 by 8 degrees with respect to a plane perpendicular to the optical axis or applying an anti-reflection coating to the tip surface of the tapered portion 512. The reflectance of the tip surface of tapered section 512 after anti-reflection coating is preferably 2% or less, more preferably 0.5% or less, and even more preferably 0.3% or less, at half width of the wavelength of the light source.

[0030] The through hole 52 is a circular hole that penetrates the center of the main body 51 linearly in the Z direction. The optical fiber 4 is inserted into the through hole 52 from the base end side, and is further bonded to the inner circumferential surface of the through hole 52 with an adhesive, whereby the optical fiber 4 is fixedly held by the ferrule 5. As shown in FIG. 5 , the through hole 52 includes a guide portion 521 located on the base end side, a large diameter portion 522 located on the distal side of the guide portion 521, a small diameter portion 523 located on the distal side of the large diameter portion 522, and an opening 524 located on the distal side of the small diameter portion 523.

[0031] The guide portion 521 is a tapered space that penetrates the base end surface of the straight portion 511 in the Z direction and communicates with the outside. The diameter of the guide portion 521 gradually decreases from the base end side toward the tip end side. When the optical fiber 4 is inserted into the through hole 52 from the base end side, the tip end of the optical fiber 4 slides on the inner circumferential surface of the guide portion 521, thereby guiding the insertion of the optical fiber 4 into the through hole 52. The large diameter portion 522 is located on the tip side of the guide portion 521 and is a cylindrical space that communicates with the guide portion 521. The diameter of the guide portion 521 is larger than the outer diameter of the optical fiber 4 and is constant along the Z direction. Furthermore, the diameter of the tip end of the guide portion 521 is equal to the diameter of the large diameter portion 522, and the tip end of the guide portion 521 and the large diameter portion 522 are continuous.

[0032] The small diameter portion 523 is located on the tip side of the large diameter portion 522 and is a cylindrical space that communicates with the large diameter portion 522. The diameter of the small diameter portion 523 is smaller than the diameter of the large diameter portion 522 and is approximately equal to the outer diameter of the optical fiber 4. The diameter of the small diameter portion 523 is constant along the Z direction. The connection portion between the large diameter portion 522 and the small diameter portion 523 forms a flat surface perpendicular to the Z direction. The opening 524 is a circular hole that linearly penetrates the tip surface of the tapered portion 512 in the Z direction and communicates with the outside. The opening 524 is located on the tip side of the small diameter portion 523 and communicates with the small diameter portion 523. The diameter of the opening 524 is smaller than the diameter of the small diameter portion 523 and is constant along the Z direction. 3, when the optical fiber 4 is held by the ferrule 5, the optical fiber 4 comes into contact with the inner circumferential surface of the small diameter portion 523, and the core 41 is exposed to the outside through the opening 524. The guide portion 521, the large diameter portion 522, the small diameter portion 523, and the opening 524 are all concentric, and their centers are aligned on the same line as the centers of the main body portion 51 and the tapered portion 512. The optical fiber 4 is fitted into the small diameter portion 523, and is bonded to the inner circumferential surface of the small diameter portion 523 with an adhesive. This allows the optical fiber 4 to be fixedly held by the ferrule 5.

[0033] 4, the holding mechanism 6 has a function of holding the optical element 2, the collimator lens 3, and the ferrule 5 in a state in which the optical element 2, the collimator lens 3, and the optical fiber 4 are aligned. The holding mechanism 6 includes a cylindrical sleeve 61 that holds the ferrule 5 that holds the optical fiber 4 therein, a cylindrical lens holder 62 that is provided on the tip surface of the sleeve 61 and holds the collimator lens 3 therein, and a cylindrical optical element holder 63 that is provided on the tip surface of the lens holder 62 and holds the optical element 2 therein.

[0034] Like the ferrule 5, the sleeve 61, lens holder 62, and optical element holder 63 are each made of an insulating, low-dielectric, and thermoplastic material, such as polyacetal (or polyoxymethylene) resin, polypropylene, polyethylene, polystyrene, acrylic, polyamides including nylon 6 and nylon 66, polyethylene terephthalate, polybutylene terephthalate, acrylonitrile butadiene styrene, polyether ether ketone, cycloolefin polymer, polycarbonate, polyphenylene sulfide, polyetherimide, vinyl chloride, vinylidene chloride, butyral, vinyl acetate, or polybutylene. Therefore, the optical probe 1 does not include components made of conductive or high-dielectric materials. Therefore, the components of the optical probe 1 do not function as a shield against external electric or magnetic fields due to external electric fields or magnetic fields, and are not polarized by external electric or magnetic fields, thereby not affecting the polarization state of light passing through the optical element 21. This configuration improves the measurement accuracy of the optical probe 1.

[0035] The sleeve 61 is a cylindrical member that holds the ferrule 5, which holds the optical fiber 4, inside. As shown in FIG. 4 , the sleeve 61 includes a cylindrical main body 611, a flange 612 formed on the outer peripheral surface of the distal end of the main body 611, and a through-hole 613 that linearly penetrates the main body 611 in the Z direction. The main body 611 is a cylindrical portion that extends linearly in the Z direction. The outer diameter of the main body 611 is constant along the Z direction. The distal end surface and the proximal end surface of the main body 611 are flat surfaces that are perpendicular to the Z direction. The flange 612 is an annular portion that extends outward from the outer peripheral surface of the distal end of the main body 611. The outer diameter of the flange 612 is larger than the outer diameter of the main body 611 and is constant along the Z direction. The distal end surface and the proximal end surface of the flange 612 are flat surfaces that are perpendicular to the Z direction. The through hole 613 is a circular hole that penetrates the center of the main body 611 linearly in the Z direction. The diameter of the through hole 613 is approximately equal to the outer diameter of the straight portion 511 of the ferrule 5 and is constant along the Z direction. As shown in Fig. 3, the ferrule 5 is inserted into the through hole 613 from the base end side, and laser welding is performed between the straight portion 511 of the ferrule 5 and the inner circumferential surface of the through hole 613, whereby the ferrule 5 is fixedly held by the sleeve 61.

[0036] Returning to FIG. 4 , the lens holder 62 is a cylindrical member that holds the collimator lens 3 therein. The lens holder 62 includes a cylindrical main body 621, a storage recess 622 formed on the distal end surface of the main body 621, and an opening 623 that linearly penetrates the bottom surface of the storage recess 622 in the Z direction. The main body 621 is a cylindrical portion that extends linearly in the Z direction. The outer diameter of the main body 621 is larger than the outer diameter of the flange portion 612 of the sleeve 61 and is constant along the Z direction. The distal end surface and the proximal end surface of the main body 621 are flat surfaces that are perpendicular to the Z direction. The storage recess 622 is a recess formed in the center of the distal end surface of the main body 621, and the collimator lens 3 is fixedly held within the storage recess 622. In the illustrated embodiment, the storage recess 622 has a circular outer shape that corresponds to the outer shape of the collimator lens 3, but the present invention is not limited to this. The outer shape of the storage recess 622 only needs to correspond to the outer shape of the collimator lens 3. For example, if the outer shape of the collimator lens 3 is rectangular, the storage recess 622 will also have a rectangular outer shape. The opening 623 is a circular opening formed so as to penetrate in a straight line from the center of the bottom surface (the surface exposed toward the tip side) of the storage recess 622 toward the tip side. The diameter of the opening 623 is smaller than the outer diameter of the collimator lens 3. As shown in FIG. 3 , the collimator lens 3 is stored in the storage recess 622, and further, the collimator lens 3 is bonded to the inner circumferential surface and bottom surface of the storage recess 622 with an adhesive, whereby the collimator lens 3 is fixedly held by the lens holder 62.

[0037] 4, optical element holder 63 is a cylindrical member that holds optical element 2 therein. As shown in Figures 4 and 6, optical element holder 63 includes a cylindrical main body 631 that extends linearly in the Z direction, a flange 632 formed on the outer peripheral surface of the base end of main body 631, a tapered portion 633 that extends from the tip end of main body 631 toward the tip side, a storage recess 634 formed on the base end surface of main body 631, and an opening 635 that penetrates a bottom surface of storage recess 634 linearly in the Z direction.

[0038] The main body 631 is a cylindrical portion extending linearly in the Z direction. The outer diameter of the main body 631 is smaller than the outer diameter of the main body 621 of the lens holder 62 and is constant along the Z direction. The base end surface of the main body 631 is a flat surface perpendicular to the Z direction. The flange 632 is an annular portion formed to extend outward from the outer peripheral surface of the base end of the main body 621. The outer diameter of the flange 632 is larger than the outer diameter of the main body 631 and smaller than the outer diameter of the main body 621 of the lens holder 62. The outer diameter of the flange 632 is constant along the Z direction. The distal end surface and proximal end surface of the flange 632 are flat surfaces perpendicular to the Z direction. The tapered portion 633 is a truncated cone portion extending from the distal end of the main body 631 toward the distal end. The outer diameter of the tapered portion 633 gradually decreases from the proximal end toward the distal end. The tip surface of the tapered portion 633 is a flat surface perpendicular to the Z direction.

[0039] As shown in FIG. 6 , the storage recess 634 is a circular recess formed on the proximal end surface of the main body 631. The opening 635 is a circular opening formed so as to linearly penetrate the center of the bottom surface (the surface exposed toward the proximal end) of the storage recess 634 toward the distal end. The diameter of the opening 635 is smaller than the diameter of the storage recess 634. As shown in FIG. 3 , a rectangular parallelepiped transparent member 7 made of a transparent, insulating, low-dielectric material such as transparent resin or quartz glass is fixed to the bottom surface of the storage recess 634 with an adhesive and stored therein. The optical element 2 is placed on the distal end surface of the transparent member 7 so that the proximal end surface of the optical element 21 contacts the transparent member 7. The proximal end surface of the optical element 21 is fixed to the distal end surface of the transparent member 7 with an adhesive, and the optical element 2 is stored in the opening 635. As a result, the optical element 2 is fixedly held by the optical element holder 63. In this state, the optical element 2 is exposed to the outside through the opening 635. The reflector 22 of the optical member 2 faces the outside through the opening 635.

[0040] In the manufacturing method of the optical probe 1, the ferrule 5, the lens holder 62, and the optical element holder 63 inserted into the sleeve 61 are each held by a three-axis (X-axis, Y-axis, and Z-axis) movable stage. By moving the ferrule 5 in the X-axis or Y-axis direction using the movable stage, the sleeve 61 moves in the X-axis or Y-axis direction following the movement of the ferrule 5, and the position of the sleeve 61 in the X-axis or Y-axis direction is adjusted. Furthermore, by moving the ferrule 5 in the Z-axis direction using the movable stage, the sleeve 61 slides on the ferrule 5, and the position of the sleeve 61 in the Z-axis direction is adjusted. The positions of the sleeve 61, the lens holder 62, and the optical element holder 63 in the X-axis, Y-axis, and Z-axis directions, respectively, are finely adjusted, and the optical element 2, the collimator lens 3, and the optical fiber 4 are aligned (centered). The alignment work is performed, for example, by fine-tuning the positions of the sleeve 61, the lens holder 62, and the optical element holder 63 in the X-axis direction, the Y-axis direction, and the Z-axis direction, respectively, so that the ratio of the intensity of the reflected light from the optical probe 1 to the intensity of the incident light on the optical probe 1 (intensity of reflected light / intensity of incident light) exceeds a predetermined threshold value.

[0041] After the alignment process is completed, the distal end surface of the main body 621 of the lens holder 62 is laser welded to the proximal end surface of the main body 631 or flange 632 of the optical element holder 63, thereby integrating the lens holder 62 and the optical element holder 63. Then, the distal end surface of the main body 611 or flange 612 of the sleeve 61 is laser welded to the proximal end surface of the main body 621 of the lens holder 62, thereby integrating the sleeve 61 and the lens holder 62. When the sleeve 61, the lens holder 62, and the optical element holder 63 are integrated by laser welding, the manufacture of the optical probe 1 is completed. Laser welding between the lens holder 62 and the optical element holder 63 and between the sleeve 61 and the lens holder 62 is typically performed with a YAG laser. Laser welding between the lens holder 62 and the optical element holder 63 and between the sleeve 61 and the lens holder 62 may be line welding or spot welding. In the case of spot welding, it is preferable that the lens holder 62 and the optical element holder 63, and the sleeve 61 and the lens holder 62 are laser-welded at at least three points at equal angular intervals.

[0042] In the prior art described in the Background Art section, the alignment of the optical element 2, the collimator lens 3, and the optical fiber 4 is performed by holding each of the optical element 2, the collimator lens 3, and the optical fiber 4 on a three-axis (X-axis, Y-axis, and Z-axis) movable stage and fine-adjusting their positions in the X-axis, Y-axis, and Z-axis directions. However, the optical element 2, the collimator lens 3, and the optical fiber 4 are small in size. Therefore, it is very difficult to hold each of the optical element 2, the collimator lens 3, and the optical fiber 4 at a precise angle on the three-axis movable stage and fine-adjust their positions in the X-axis, Y-axis, and Z-axis directions. Furthermore, the joining process of integrating the optical element 2, the collimator lens 3, and the optical fiber 4 with an adhesive while maintaining their precise positions requires extremely high precision and is time-consuming and costly.

[0043] On the other hand, in the optical probe 1 of the present invention, the alignment of the optical element 2, collimator lens 3, and optical fiber 4 is performed by fine-tuning the X-axis, Y-axis, and Z-axis positions of the sleeve 61, lens holder 62, and optical element holder 63 of the holding mechanism 6. The sleeve 61, lens holder 62, and optical element holder 63 are sized to be easily held by a three-axis movable stage, making it very easy to hold the sleeve 61, lens holder 62, and optical element holder 63 at accurate angles and fine-tune their X-axis, Y-axis, and Z-axis positions. Furthermore, the joining process is performed by integrating the sleeve 61, lens holder 62, and optical element holder 63 with each other by laser welding. This can be performed much more easily and quickly than conventional joining processes in which the optical element 2, collimator lens 3, and optical fiber 4 are integrated with each other using adhesive. As a result, the alignment and joining processes during the manufacture of the optical probe 1 are easy and inexpensive.

[0044] <Method of manufacturing optical probe> Next, a method for manufacturing an optical probe of the present invention will be described in detail with reference to Fig. 7 to Fig. 9. Fig. 7 is a flowchart showing a method for manufacturing the optical probe shown in Fig. 2. Fig. 8 is a flowchart showing the alignment operation shown in Fig. 7. Fig. 9 is a schematic diagram showing an inspection system used in the alignment operation shown in Fig. 7.

[0045] 7 is performed by a manufacturing machine that automatically manufactures the optical probe 1 or by an operator that manually manufactures the optical probe 1. First, in step S110, the optical fiber 4 is held by the ferrule 5. Specifically, the optical fiber 4 is inserted into the through-hole 52 of the ferrule 5 from the base end side, and then the optical fiber 4 is fitted and bonded to the small diameter portion 523 of the through-hole 52 with an adhesive, and the optical fiber 4 is fixedly held by the ferrule 5.

[0046] Next, in step S120, the ferrule 5 is held by the sleeve 61, the collimator lens 3 is held by the lens holder 62, and the optical element 2 is held by the optical element holder 63. Specifically, the ferrule 5 is inserted into the through hole 613 of the sleeve 61 from the base end side, and the ferrule 5 is held by the sleeve 61. At this stage, laser welding is not performed between the ferrule 5 and the inner peripheral surface of the through hole 613, and the ferrule 5 is rotatably held by the sleeve 61. Furthermore, the collimator lens 3 is housed in the storage recess 622 of the lens holder 62 from the tip end side, and the collimator lens 3 is bonded to the inner peripheral surface and bottom surface of the storage recess 622 with an adhesive, thereby fixedly holding the collimator lens 3 to the lens holder 62. Furthermore, the transparent element 7 is housed in the storage recess 634 of the optical element holder 63 from the base end side, and the transparent element 7 is bonded to the bottom surface of the storage recess 634 with an adhesive. Thereafter, the optical element 2 is stored in the opening 635 of the optical element holder 63 from the distal end side, and the optical element 2 is placed on the distal end surface of the transparent element 7. Furthermore, the base end surface of the optical element 21 of the optical element 2 is adhered to the distal end surface of the transparent element 7 with an adhesive, and the optical element 2 is fixedly held by the optical element holder 63.

[0047] Next, in step S130, the ferrule 5, lens holder 62, and optical element holder 63 inserted into the sleeve 61 are each held by a three-axis movable stage. Next, in step S140, an alignment operation is performed for the optical element 2, collimator lens 3, and optical fiber 4. In the alignment operation, the inspection system shown in FIG. 9 is used. As shown in FIG. 9, in the alignment operation, incident light is applied from a light source to the core 41 of the optical fiber 4 of the optical probe 1 via an optical circulator. Furthermore, reflected light from the reflector 22 of the optical probe 1 is separated by the optical circulator and input to an optical power meter. In the alignment operation, fine adjustments are made to the X-axis, Y-axis, and Z-axis positions of the sleeve 61, lens holder 62, and optical element holder 63, respectively, so that the ratio of the intensity of the reflected light to the intensity of the incident light (intensity of reflected light / intensity of incident light) exceeds a predetermined threshold value (e.g., 0.8). Note that the intensity of the incident light is measured and known in advance.

[0048] As shown in FIG. 8 , in step S141, the ferrule 5 inserted into the sleeve 61 is moved by a three-axis movable stage to adjust the positions of the sleeve 61 in the X-axis, Y-axis, and Z-axis directions. Next, in step S142, the positions of the optical element holder are adjusted in the X-axis, Y-axis, and Z-axis directions. Next, in step S143, the ferrule 5 is rotated in the through-hole 613 of the sleeve 61 as needed to adjust the polarization direction of the incident light. Next, in step S144, the intensity of the reflected light is measured using an optical power meter, and the ratio of the intensity of the reflected light to the intensity of the incident light (intensity of reflected light / intensity of incident light) is calculated. Next, in step S145, it is determined whether the intensity of the reflected light is sufficient. Specifically, it is determined whether the value calculated in step S144 exceeds a predetermined threshold (e.g., 0.8). If the value calculated in step S144 exceeds the predetermined threshold, the alignment work in step S140 is completed. On the other hand, if the value calculated in step S144 is equal to or less than the predetermined threshold value, the process returns to step S141. Note that the order in which steps S141 to S143 are performed is not particularly limited, and steps S141 to S143 may be performed in any order.

[0049] 7 , in step S150, laser welding is performed between the ferrule 5 and the inner circumferential surface of the through-hole 613 of the sleeve 61, so that the ferrule 5 is fixedly held by the sleeve 61. Next, in step S160, a distal end surface of the main body 621 of the lens holder 62 is laser welded to a proximal end surface of the main body 631 or the flange 632 of the optical element holder 63, so that the lens holder 62 and the optical element holder 63 are integrated together. Next, in step S170, a distal end surface of the main body 611 or the flange 612 of the sleeve 61 is laser welded to a proximal end surface of the main body 621 of the lens holder 62, so that the sleeve 61 and the lens holder 62 are integrated together. Note that the order in which steps S160 and S170 are performed is not particularly limited, and steps S160 and S170 may be performed in any order, or steps S160 and S170 may be performed simultaneously. When the joining operations for integrating the sleeve 61, the lens holder 62, and the optical element holder 63 with one another are completed in steps S160 and S170, the manufacturing method S100 ends.

[0050] While the optical probe and the method for manufacturing the optical probe of the present invention have been described above based on the illustrated embodiments, the present invention is not limited to these. Each component of the present invention can be replaced with any component that can perform the same function, or any component can be added to each component of the present invention.

[0051] Those skilled in the art and technology to which the present invention pertains will be able to modify the configuration of the described optical probe of the present invention without significantly departing from the principles, concepts, and scope of the present invention, and optical probes having modified configurations are also within the scope of the present invention.

[0052] 2 to 6 are merely examples for the purpose of explanation, and the present invention is not necessarily limited thereto. The scope of the present invention also includes embodiments in which any component is added or combined, or any component is deleted, as long as the addition does not deviate from the principles and intent of the present invention. The number and types of steps in the method for manufacturing an optical probe shown in FIG. 7 are merely examples for the purpose of explanation, and the present invention is not necessarily limited thereto. The scope of the present invention also includes embodiments in which any process is added or combined for any purpose, or any process is deleted, as long as the addition does not deviate from the principles and intent of the present invention. [Explanation of symbols]

[0053] 1: Optical probe 2: Optical components 21: Optical elements 22:Reflector 3: Collimator lens 4: Optical fiber 41: Core 42: Clad 5: Ferrule 51: Main body 511: Straight section 512: Tapered section 52: Through hole 521: Guide section 522: Large diameter section 523: Small diameter part 524 :Aperture 6: Retention mechanism 61: Sleeve 611: Main body 612: Flange part 613: Through hole 62: Lens holder 621: Main body 622: Storage recess 623 :Aperture 63: Optical component holder 631: Main body 632: Flange part 633: Tapered section 634: Storage recess 635 :Aperture 7: Transparent material 100: Optical probe 110: Optical elements 120:Reflector 130: Optical components 140: Collimator lens 150: Optical fiber 160: Ferrule 200: External electric or magnetic field S100: Manufacturing method S110, S120, S130, S140, S141, S142, S143, S144, S145, S150, S150, S160, S170: Process

Claims

1. an optical member including an optical element that changes the polarization state of light passing through it depending on the strength of an external electric field or an external magnetic field, and a reflector provided on a tip surface of the optical element; a collimator lens for collimating the light incident on the optical element and for collecting the light reflected from the reflector; an optical fiber that emits the incident light toward the collimator lens and into which the reflected light collected by the collimator lens is incident; a ferrule that holds the optical fiber therein; a holding mechanism for holding the optical member, the collimator lens, and the ferrule, The holding mechanism includes: a cylindrical sleeve that holds the ferrule therein; a cylindrical lens holder provided on a tip end surface of the sleeve and holding the collimator lens therein; a cylindrical optical element holder provided on a tip end surface of the lens holder and holding the optical element therein; The optical probe is characterized in that the sleeve, the lens holder, and the optical element holder are each formed of an insulating, low-dielectric, and thermoplastic material.

2. The optical probe of claim 1 , wherein the sleeve and the lens holder, and the lens holder and the optical element holder are laser welded together, thereby integrating the sleeve, the lens holder, and the optical element holder.

3. 3. The optical probe of claim 2, wherein the laser welds between the sleeve and the lens holder and between the lens holder and the optical element holder are spot welds.

4. 2. The optical probe according to claim 1, wherein the sleeve, the lens holder, and the optical element holder are each made of polyacetal resin.

5. The device further includes a transparent member formed of a transparent insulating and low-dielectric material, the optical element holder includes a cylindrical main body, a storage recess formed on a base end surface of the main body, and an opening penetrating a bottom surface of the storage recess toward a tip end side, the transparent member is fixed on the bottom surface of the storage recess, The optical probe of claim 1 , wherein the optical member is located within the opening and fixed on the transparent member.

6. The optical probe according to claim 5 , wherein the optical member is fixed on the transparent member so that the optical element is in contact with the transparent member and the reflector faces the outside through the opening.

7. 2. The optical probe of claim 1, wherein a laser weld is formed between the ferrule and the sleeve, whereby the ferrule is fixedly held by the sleeve.

8. The optical probe according to claim 1 , wherein the holding member holds the optical member, the collimator lens, and the optical fiber in a state where the optical member, the collimator lens, and the optical fiber are aligned.

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