TWI626484B - Coaxial fiber optic head, fiber optic sensor, coaxial fiber optic head manufacturing method - Google Patents

Abstract

The coaxial fiber-optic head (30) includes a distal end fitting (60) having a tubular portion (65) having a shaft hole (66) opened in the front; and a cylindrical internal component (70) mounted on the tubular type a shaft hole (66) of the tubular portion (65) and a coaxial fiber bare wire (40) for mounting the front end fitting (60) in a state of being inserted into the internal component (70), and The fiber bare wire (41) on one side of the bare fiber of the light projecting or receiving light is centered on the bare fiber line (43) on the other side, and the bare fiber line (43) on the other side is arranged on the concentric circle; and the fixed layer (77) And being formed in the inner component (70) for fixing the coaxial fiber bare wire (40) interposed in the inner component (70) to a state in which it is not displaceable; in the inner component (70) The inner peripheral wall is formed with a position restricting portion (75) that restricts the position of the bare optical fiber (43) on the other side at equal intervals in the circumferential direction, and the position restricting portion (75) is along the aforementioned inner part ( 70) The axial straight line shape.

Description

Coaxial fiber optic head, fiber optic sensor, and coaxial fiber optic head manufacturing method

The present invention relates to a technique for improving the accuracy of coaxial alignment of bare fibers.

The optical fiber sensor detects the presence or absence of an object in the detection area by irradiating the detection light toward the detection area and receiving the reflected light by using the optical fiber head composed of the bare optical fiber. In the optical fiber head used in the optical fiber sensor, as in the following Patent Document 1 or the following Patent Document 2, a plurality of light receiving elements are disposed on a concentric circle centering on the bare optical fiber for light projecting. A coaxial fiber optic head with bare fiber optic.

[Previous Technical Literature] [Patent Document]

Patent Document 1: Japanese Patent Laid-Open No. Hei 7-234319

Patent Document 2: Japanese Laid-Open Patent Publication No. 2002-82228

In order to improve the detection accuracy of the fiber sensor, as shown in Figure 23. As shown in the above, it is preferable to arrange the bare optical fibers F3 for light reception at equal intervals on the concentric circles centering on the bare optical fiber F1 for light projection, thereby improving the coaxial alignment accuracy of the bare optical fibers F1 and F3. However, the conventional structure is determined by the correlation between the aperture D1 on the accessory M side for mounting the bare fiber wires F1 and F3 and the fiber diameter (diameter of the bare wire) of the bare fibers F1 and F3. The coaxial alignment accuracy of the bare fiber lines F1 and F3. On the other hand, since there is a machining deviation (so-called tolerance) in the diameter D1 of the fitting M side or the optical fiber diameters of the bare fibers F1 and F3, when the diameter D1 side becomes the largest tolerance and the optical fiber diameter becomes the smallest tolerance, As shown in Fig. 24, there is a problem that the position of the bare optical fiber F1 for light projection and the bare optical fiber F3 for light reception are shifted, so that the accuracy of coaxial alignment is lowered.

The present invention has been accomplished based on the above-described circumstances, and its purpose is to improve the coaxial alignment accuracy of bare optical fibers.

The coaxial type optical fiber head disclosed in the present specification includes: a front end fitting having a tubular portion having a shaft hole opened in the front; and a cylindrical inner member attached to the shaft hole of the cylindrical portion And a coaxial optical fiber bare wire in which the front end fitting is mounted while being inserted into the internal component, and is centered on a bare fiber of one of the bare optical wires for light projecting or light receiving. a plurality of bare fibers on the other side are arranged on a plurality of concentric circles; and a fixed layer is formed in the foregoing The inner part of the inner part is fixed in a state in which the coaxial optical fiber inserted into the inner part is not displaceable; and the inner peripheral wall of the inner part is formed at equal intervals in the circumferential direction to restrict the other side. a position regulating portion at a position of the bare optical fiber, and the position regulating portion is a linear shape along an axial direction of the internal component.

In this configuration, due to the position limit set in the internal part The system limits the position of the bare fiber, so it is not easy to cause the fiber bare line to shift (eccentricity). Therefore, the coaxial alignment accuracy of the bare fiber can be improved. Further, since the bare optical fibers are fixed in a state in which the fixed layers are coaxially arranged, the coaxial arrangement is not lost due to the positional relationship of the bare fibers. Further, since the position regulating portion has a linear shape along the axial direction of the internal component, the bare optical fiber inserted into the other side of the internal component has a linear shape in accordance with the position regulating portion. Therefore, since the bare fiber of the other side is hard to bend inside the internal part, the coaxial position accuracy becomes high. In addition, when the position regulating portion is formed into a linear shape in advance, the position regulating portion can function as a guide for guiding the bare optical fiber to the axial front side when the internal component is inserted, so that it is easy to bare the optical fiber. The advantage of inserting a wire into an internal part.

The embodiment of the coaxial optical fiber head is preferably as Under the composition.

The position restricting portion is formed into a circular cross section. According to this, when the bare optical fiber is inserted into the front end fitting (internal component), even if the bare optical fiber contacts the position regulating portion, the bare optical fiber is not easily damaged, and deformation or the like is less likely to occur.

Formed as follows: a peripheral surface is provided outside the inner part The strip is positioned to the cylindrical portion by abutting against the hole wall of the shaft hole formed in the tubular portion so that the center of the inner member coincides with the center of the tubular portion. According to this, the inner part and the bare fiber line can be positioned (positioned in a center-consistent manner) to the front end fitting. Therefore, the detection accuracy of the fiber sensor can be improved.

Formed as follows: at the front end of the internal part is set to have a head portion of the positioning surface, the head portion being positioned in the cylindrical portion by abutting against a hole edge of the shaft hole formed in the cylindrical portion so that the center of the inner part coincides with the center of the cylindrical portion . According to this, the inner part and the bare fiber line can be positioned (positioned in a center-consistent manner) to the front end fitting. Therefore, the detection accuracy of the fiber sensor can be improved.

The manufacturer of the coaxial optical fiber head disclosed in the present specification The method is centered on the bare fiber of one of the bare fibers of the optical fiber for light projecting or light receiving, and the bare fiber of the other side is arranged at the front end of the coaxial fiber bare wire on the concentric circle. And a method of manufacturing a coaxial optical fiber head in which a front end fitting is attached, characterized in that the cylindrical inner portion having the position regulating portion is formed at equal intervals in the circumferential direction with respect to the cylindrical portion of the front end fitting In the step of mounting, the position regulating portion has a function of restricting the position of the bare optical fiber on the other side and has a shape that linearly extends in the axial direction; and is accommodated in the aforementioned position by the bare optical fiber on the other side. a step of aligning the portions between the restricting portions, and assembling the bare optical wires for light projecting and receiving light to the front end fittings while the front end portion penetrates the cylindrical portion of the inner component; and a step of applying an adhesive to the front end portion of the bare optical fiber for light projecting or receiving light of the tubular portion; and a step of pulling back the bare optical fiber having the adhesive applied to the front end portion toward the inner component side; And removing a portion protruding from the front end surface of the cylindrical portion after pulling back, and forming the front end of the bare optical fiber to be the same plane as the front end surface of the cylindrical portion.

The filling operation of the internal parts by the subsequent agent is, for example, a test This is done before inserting the bare fiber strand into the internal part. However, when the adhesive is filled in advance, the insertion resistance when the bare optical fiber is inserted into the internal component is increased in any case, and the assembly workability is poor. In this regard, in the method of manufacturing a coaxial optical fiber head disclosed in the present specification, first, a bare fiber is inserted through a front end fitting (internal component), and then a bare fiber coated with an adhesive at a front end portion is transferred to an internal component. The inner side is pulled back, thereby filling the adhesive with the inner part. According to this, since the insertion resistance when the bare optical fiber is inserted into the internal component is small, the assemblability is excellent and the manufacturing efficiency is high. Further, since the position regulating portion is formed in a linear shape along the axial direction of the inner member, it functions as a guide when the bare optical fiber is inserted or pulled back toward the distal end fitting (internal component). Therefore, the assembly is better and the manufacturing efficiency is higher.

According to the present invention, the coaxial alignment accuracy of the bare optical fiber can be improved. It is also possible to improve the assembly workability of the optical fiber head.

10‧‧‧Fiber optic sensor

20‧‧‧Sensor body

20A‧‧‧shell

21‧‧‧Projecting Department

22‧‧‧Projection circuit

23‧‧‧Receiving Department

24‧‧‧Light-receiving circuit

27‧‧‧Control circuit

30‧‧‧Coaxial fiber optic head

40‧‧‧Coaxial fiber bare wire

41‧‧‧Fiber bare wire for light projection

43‧‧‧Fibered bare fiber

60‧‧‧ front end accessories

61‧‧‧Accessory body

63‧‧‧ accommodating department

65‧‧‧Cylinder

65A‧‧‧ front face

66‧‧‧Axis hole

67‧‧‧Cover components

70‧‧‧Internal parts

71‧‧‧ 突条

72‧‧‧ head

72A‧‧‧Conical surface (positioning surface)

73‧‧‧through holes

75‧‧‧Location Restriction Department

76‧‧‧Pushing Department

77‧‧‧Fixed layer

80‧‧‧plug (connector part)

81, 83‧‧‧ Insertion Department

90‧‧‧ Type tube

100‧‧‧ panel

110‧‧‧Mounting holes

C‧‧‧Binder

L‧‧‧Concentric Circle

U‧‧‧ hardening adhesive

Figure 1 is a block diagram of a fiber optic sensor suitable for use in an embodiment.

Figure 2 is a perspective view of a coaxial fiber optic head.

Figure 3 is a vertical cross-sectional view of the front end fitting.

Fig. 4 is a cross-sectional view taken along line A-A in Fig. 3.

Fig. 5 is a perspective view of the front end fitting viewed from the rear (a schematic view showing the unmounted state of the cover member).

Figure 6 is a perspective view of the internal parts viewed from the rear.

Figure 7 is a perspective view of the internal parts viewed from the front.

Fig. 8 is an enlarged view of Fig. 4.

Figure 9 is a vertical cross-sectional view of the internal parts.

Figure 10 is a front view of the internal parts.

Figure 11 is a right side view of the internal parts.

Figure 12 is a left side view of the internal parts.

Figure 13 is a bottom view of the internal parts.

Figure 14 is a rear view of the internal part.

Figure 15 is a top view of the internal parts.

Fig. 16 is a perspective view showing the configuration of the plug.

Figure 17 is a schematic view showing the process of a coaxial fiber-optic head (showing a schematic view of the first step).

Figure 18 is a schematic view showing the process of a coaxial fiber-optic head (showing a schematic view of the second step).

Figure 19 is a schematic view showing the process of a coaxial fiber-optic head (display Schematic diagram of the third step).

Figure 20 is a schematic view showing the process of a coaxial fiber-optic head (showing a schematic view of the fourth step).

Figure 21 is a schematic view showing the process of a coaxial fiber-optic head (showing a schematic view of the fifth step).

Figure 22 is a schematic view showing the process of a coaxial fiber-optic head (showing a schematic view of the sixth step).

Fig. 23 is a cross-sectional view showing the coaxial type of optical fiber head (a schematic view showing a state in which the bare wire is not offset).

Fig. 24 is a cross-sectional view showing the coaxial type of optical fiber head (a schematic view showing a state in which a bare wire has an offset).

<Embodiment>

An embodiment of the present invention will be described with reference to Figs. 1 to 22 .

1. Construction of the optical fiber sensor 10

Figure 1 is a block diagram showing the construction of the fiber optic sensor 10. The optical fiber sensor 10 includes a sensor body portion 20 and a coaxial type optical fiber head 30 that is attached to the sensor body portion 20 by a plug 80. Further, the plug 80 is an example of the "connector portion" of the present invention.

The sensor body portion 20 is provided with a casing 20A that substantially forms a box shape. Inside the casing 20A, a light projecting portion is provided 21. Projection circuit 22, light receiving unit 23, light receiving circuit 24, and control circuit 27. The light projecting unit 21 is configured by, for example, a light projecting element such as an LED or a laser diode, and has a function of irradiating light to a predetermined detection area by the bare optical fiber 41 for light projection. The light projecting circuit 22 drives the drive circuit of the light projecting unit 21 in response to an instruction from the control circuit 27.

The light receiving portion 23 is, for example, a photoelectric crystal (photo The light-receiving element is formed by a light-receiving element such as a transistor, and has a function of receiving reflected light from the detection area by the bare optical fiber 43 for receiving light. The light receiving circuit 24 has a function of outputting a light receiving signal at a level corresponding to the amount of light received by the light receiving unit 23. The control circuit 27 compares the level of the received light signal output from the light receiving circuit 24 with a predetermined threshold value, thereby determining the position of the object in the detection area or the presence or absence of a function.

Figure 2 is a perspective view of a coaxial fiber optic head 30. Coaxial type The optical fiber head 30 includes: a coaxial optical fiber bare wire 40; and a protection tube 50 externally inserted outside the coaxial optical fiber bare wire 40; and a front end fitting 60 attached to the front end of the coaxial optical fiber bare wire 40; and internal components 70 And a plug 80 mounted to the terminal of the coaxial bare fiber 40. Further, reference numeral 90 shown in Fig. 2 is a type pipe for describing the type of the product or the like.

Figure 3 is a vertical sectional view of the front end fitting 60, Figure 4 It is a cross-sectional view taken along line A-A in Fig. 3. The coaxial optical fiber bare wire 40 includes: a bare optical fiber 41 for light projecting; and a plurality of optical bare wires 43 for receiving light (9 in this example). The wire diameter of the bare fiber line 43 for receiving light is smaller than the wire diameter of the bare fiber line 41 for light projecting, in this case. In the middle, the wire diameter of the optical fiber bare wire 43 for light receiving is about 1/2 of the wire diameter of the optical fiber bare wire 41 for light projection. As shown in Fig. 4 and Fig. 8, the optical fiber bare wires 43 for light receiving are arranged at equal intervals on a concentric circle opposite to the bare optical fiber 41 for light projection (centered on the center point of the bare fiber 41). Round) L. In the present specification, the arrangement of the bare fibers 43 at equal intervals on the concentric circles L centered on the bare fibers 41 is referred to as a coaxial arrangement.

The front end fitting 60 is used to connect the coaxial fiber bare wire 40 The fitting (metal fitting) attached to the predetermined mounting portion is formed with a tubular portion 65 on the front side (the left side in Fig. 3) of the fitting main body 61 which is substantially block-shaped. Inside the fitting body 61, a housing portion 63 for accommodating the coaxial fiber bare wire 40 is provided. The accommodating portion 63 has a configuration in which the fitting main body 61 is penetrated downward, and the coaxial optical fiber bare wire 40 covering the protective tube 50 is pulled downward. Further, a cover member 67 is provided on the rear surface of the fitting main body 61. As shown in Fig. 5, in a state in which the cover member 67 is not attached, the rear side of the housing portion 63 of the accessory body 61 is opened, so that the coaxial optical fiber can be bare from the rear side. The front end of the wire 40 is inserted into the tubular portion 65.

As shown in FIGS. 2 and 3, the tubular portion 65 is provided in The center of the front side of the fitting body 61 is slightly above the upper position, and is formed in a horizontally straight shape. The tubular portion 65 has a shaft hole 66 into which the coaxial optical fiber bare wire 40 is inserted and fixed. The rear end side of the shaft hole 66 is communicated to the accommodating portion 63 of the fitting body 61, and the front end side is opened at the front side.

In the shaft hole 66 formed in the cylindrical portion 65, the front end The part is housed with an internal part 70. Fig. 6 and Fig. 7 are perspective views of the inner part 70. Figures 10 through 15 are six views of the internal part 70. The internal component 70 is made of a synthetic resin and has a cylindrical shape in which a through hole 73 penetrating in the front-rear direction is formed along the axial direction. As shown in Fig. 6, on the outer peripheral wall of the inner member 70, three ridges 71 are formed along the axial direction. The ridge 71 has a center portion of the inner member 70 (more specifically, a center of the through hole 73 formed in the inner member 70 opposite to the center of the shaft hole 66 formed in the tubular portion 65) and the cylindrical portion. The center of the 65 is consistent with the function of positioning the inner part 70 to the cylindrical portion 65. In other words, the three ridges 71 formed on the inner component 70 are brought into contact with the hole walls formed in the axial holes 66 of the tubular portion 65 to be centered on the inner component 70. The center of the through hole 73 can be in a state of being aligned with the center of the shaft hole 66 formed in the tubular portion 65. Further, the ridges 71 are formed at equal intervals in the circumferential direction and are formed substantially in a triangular shape (see FIG. 6).

Also, at the front end of the inner part 70, a large diameter is provided. Head 72. The head 72 of the large diameter is oriented rearward to form a conical shape having a reduced diameter. Similarly to the ridge 71, the head portion 72 has a function of matching the center of the inner member 70 with the center of the tubular portion 65.

That is, due to the conical surface 72A of the head 72, it abuts against the shaft hole. By the edge of the hole 66, the inner part 70 is centered toward the center of the cylindrical portion 65, so that the center of the inner part 70 can be positioned so as to coincide with the center of the cylindrical portion 65. In addition, when the hole edge of the shaft hole 66 is also formed in advance In the case of a conical surface, the inner part 70 can be centered with respect to the cylindrical portion 65 with high precision, which is preferable. Further, the conical surface 72A is an example of the "positioning surface" of the present invention.

Then, the coaxial optical fiber bare wire 40 inserted into the tubular portion 65 The front end portion is configured to be fixed to the through hole 73 penetrating the inner member 70 and to face the bare end from the front end surface 65A of the tubular portion 65 in the front side, and to be fixed by a fixing layer 77 to be described later.

Also shown in Figure 7 or Figure 8, formed in internal zero The hole wall of the through hole 73 of the member 70 is formed with a position regulating portion 75 that protrudes toward the inside as the center of the hole. The position regulating portion 75 is formed at equal intervals in the circumferential direction corresponding to the bare optical fibers 43 for light reception disposed on the concentric circles L centering on the bare optical fibers 41 for light projection.

As shown in Fig. 8, the position restricting portion 75 is tied to the position It is placed between the bare fiber wires 43 on the concentric circle L, and has a function of positioning each bare fiber wire 43 in the circumferential direction. In this way, since the displacement of the bare optical fiber 43 for light reception can be prevented compared to the case where the position regulating portion 75 is not provided, the coaxial alignment accuracy of the coaxial optical fiber bare wire 40 can be improved. In addition, the high coaxial alignment accuracy means that the center of the bare fiber 41 is aligned with the center of the tubular portion 65, and the optical fibers for light reception are arranged at equal intervals on the concentric circle L centering on the bare fiber 41. The status of bare wire 43.

Further, the position restricting portion 75 is formed in a circular cross section (substantially Semicircular). By forming the cross section into a circular shape, even when the bare optical wires 41 and 43 are inserted into the internal component 70, even the bare optical wires 41 and 43 are connected. When the position restricting portion 75 is touched, the bare fibers 41 and 43 are not easily damaged, and deformation or the like is less likely to occur.

Moreover, as shown in Fig. 8, the through hole in the inner part 70 The inside of 73 is filled with a curable adhesive U of a resin type (for example, an epoxy resin). The hardenable adhesive U forms a fixed layer 77 for fixing the bare optical fibers 41, 43 to avoid positional displacement. If the fixed layer 77 is not provided, the accuracy of the coaxial arrangement may decrease due to the movement of the bare optical fibers 41 and 43 inside the internal component 70. However, by providing the fixed layer 77 as in the present embodiment, Since the positions of the bare optical fibers 41 and 43 can be fixed, the coaxial alignment accuracy can be improved.

Moreover, each bare fiber line 41, 43 can be fixed by a layer 77, while remaining in a state of being separated from other bare fiber wires 41, 43 or internal parts 70. When the bare fiber wires 41, 43 are in contact with the internal component 70 or other bare fiber wires 41, 43, there is a fear that when an external force is applied under a chance, the bare fiber wires 41, 43 and the internal component 70 or Other bare fibers 41 and 43 interfere with each other and cause injury or deformation.

In this regard, as in the present embodiment, each of them is held in advance. The bare optical fibers 41 and 43 can be protected from the bare optical fibers 4, 43 or the internal components 70 by the fixing layer 77, and the bare optical fibers 41 and 43 can be protected even if they are applied under a single chance. The external force can also prevent the bare fibers 41 and 43 from being deformed or injured.

Further, as shown in FIG. 9, the position restricting unit 75 is configured A linear shape along the axial direction (front-rear direction) of the inner member 70 and formed in a range from the front end of the through hole 73 to the center portion Inside. By forming the position regulating portion 75 into a linear shape in advance, the bare optical fiber 43 inserted into the internal component 70 is formed into a linear shape in accordance with the position regulating portion 75. Therefore, since the bare optical fiber 43 is not easily bent inside the internal component 70, the coaxial arrangement accuracy becomes high. In addition, when the position regulating portion 75 is formed into a linear shape in advance, the position regulating portion 75 also functions as a guide for guiding the bare optical fiber 43 to the axial front side when inserted into the through hole 73, so that it is easy. The advantage of inserting the bare fiber strand 43 into the inner part 70.

When returning to Figure 1 and Figure 2, continue to explain, the plug 80 is installed at the terminal end of the coaxial optical fiber bare wire 40. At the lower end portion of the plug 80, a pair of left and right insertion portions 81, 83 are provided. In each of the insertion portions 81 and 83, a bare optical fiber 41 for light projection and a bare optical fiber 43 for light reception are respectively inserted (see FIG. 16). A receiving portion (not shown) for fixing the plug 80 is formed on the front wall of the sensor main body portion 20, and the plug 80 can be inserted into the receiving portion and locked.

Then, the plug 80 is inserted into the sensor body portion 20 In the state shown in Fig. 1, the bare optical fiber 41 for light projection inserted in the insertion portion 81 is located on the front surface of the light projecting portion 21, and the optical fiber bare wire 43 inserted into the insertion portion 83 is received. It is located on the front side of the light receiving unit 23. Therefore, when light is emitted from the light projecting portion 21, the light can be irradiated to the predetermined detection region through the bare optical fiber 41 for light projection. Further, the reflected light of the light that is incident on the detection region can be introduced into the light receiving unit 23 through the bare optical fiber 43 for receiving light to receive the light.

In the present embodiment, as shown in Fig. 2, Since the outer peripheral surface of the cylindrical portion 65 provided on the distal end fitting 60 is provided with a screw thread, when the coaxial optical fiber head 30 is fixed to a predetermined mounting portion (in this example, the panel 100), it can be formed in After the mounting hole 110 of the panel 100 is inserted into the tubular portion 65, the front end fitting 60 is fixed to the panel 100 by bolt locking.

After the front end fitting 60 is fixed, when the light projecting portion 21 is driven When the light is irradiated to the detection area by the bare optical fiber 41 for light projection, the light is reflected on the surface of the object as long as there is an object in the detection area. Then, a portion of the reflected light reflected on the surface of the object enters the light receiving portion 23 through the bare optical fiber 43 for receiving light, and the level of the received light signal output from the light receiving circuit 24 is higher than a predetermined threshold. .

On the other hand, there is no object in the detection area. In the meantime, since there is no reflection of light, and there is almost no light received by the light receiving unit 23, the level of the light receiving signal output from the light receiving circuit 24 is lower than a predetermined threshold. Therefore, in the control circuit 27, the position or presence or absence of the object in the detection area can be determined by comparing the level of the received light signal with a predetermined threshold value.

2. Method of manufacturing coaxial fiber tip 30

The coaxial fiber tip 30 is manufactured by the following seven steps. First, in the first step, the operation of attaching the internal component 70 to the tubular portion 65 of the distal end fitting 60 is performed. Internal part 70 is attached to the coating After the agent C is on the outer peripheral surface, the shaft hole 66 formed in the tubular portion 65 of the distal end fitting 60 is inserted from the front side (the left side of Fig. 17).

When the inner part 70 is continuously inserted into the cylindrical portion 65 At the time when the entire inner part 70 is substantially inserted, the large-diameter head portion 72 formed at the front end collides with the front end surface 65A of the tubular portion 65 to be in a state in which it cannot be further inserted, and the internal parts are completed. 70 installation. In the state in which the mounting is completed, the inner member 70 is almost entirely accommodated in the tubular portion 65 except for the front end portion 72, and the front end portion of the head portion 72 is slightly protruded from the front end surface 65A toward the front side as shown in Fig. status.

In addition, the internal component 70 accommodated in the tubular portion 65 is capable of The center of the through hole 73 is positioned so as to coincide with the center of the shaft hole 66 formed in the cylindrical portion 65 by the action of the conical surface 72A formed on the head portion 72 and the protrusion 71 formed on the outer peripheral wall. . Then, the adhesive C applied to the outer peripheral surface can be fixed to the hole wall of the shaft hole 66 while being held in the state of being positioned.

Then, in the second step, one is to cast a light The bare optical fiber 41 and the bare optical fiber 43 for receiving light are assembled to the front end fitting 60. Specifically, each of the bare optical fibers 41 and 43 is inserted into the distal end fitting 60 from the rear, and sequentially passes through the accommodating portion 63 of the fitting main body 61, the tubular portion 65, and the internal components accommodated on the front end side of the tubular portion 65. 70. The bare wire front end is inserted so as to protrude only from the front end surface of the tubular portion 65 toward the front by a predetermined length (the dimension H shown in Fig. 18).

Moreover, when the bare fiber wires 41 and 43 are inserted, the system can be used by the group. The operator adjusts the position of the bare fiber line 43 so that the bare fiber line 41 for light projection is at the center of the through hole 73 of the internal component 70, and the remaining nine bare fibers 43 for receiving the light are accommodated in the position restricting portion. Within 75. In this manner, the bare optical fiber 43 for light reception can be arranged at equal intervals on the concentric circle L centering on the bare optical fiber 41 for light projection.

In addition, the insertion method of the bare fiber lines 41 and 43 can be The following method is employed: first, after the bare optical fiber 41 for light projection is inserted into the through hole 73 of the internal component 70, the position is adjusted so as to be accommodated between the position regulating portions 75, and the optical fibers for receiving light are thereafter naked. The method in which the wires 43 are inserted into the through holes 73 or the bare optical fibers 43 are disposed at equal intervals on the outer side of the bare optical wires 41 for light projecting, and the position is adjusted so that the bare fibers 43 can be accommodated in the position restricting portion 75. A method of inserting the bare optical fibers 41 and 43 for projecting and receiving light into the through hole 73 of the internal component 70 at a time.

Moreover, a mortar type is formed at the rear end of the inner component 70. When the bare fiber wires 41 and 43 are inserted into the internal component 70, the bare fiber wires 41 and 43 are guided to the center side of the through hole 73.

Then, in the third step, as shown in Figure 19, The operation of applying the curable adhesive U to the end portions of the bare optical fibers 41 and 43 projecting forward from the front end surface 65A of the tubular portion 65 is performed. The work of applying the curable adhesive U is performed by using a syringe or the like so as to surround the outer circumferences of the bare optical fibers 41 and 43.

Then, in the fourth step, as shown in Figure 20, The operation of pulling the bare optical fibers 41 and 43 to the rear and pulling the front end portion of the bare wire (the portion after applying the curable adhesive U) back into the through hole 73 of the internal component 70 is performed. When the front end portions of the bare fibers 41 and 43 are pulled back, since the hardenable adhesive U applied together with the front end portion is introduced into the through hole 73, the hardened adhesive U can be filled inside the through hole 73. .

Therefore, when the filled hardenable adhesive U is hardened, As shown in Fig. 8, the optical fiber bare wires 43 for receiving light can be fixed at positions at equal intervals in a state of being concentric with the concentric circle L centered on the bare fiber 41. Further, the hardenable adhesive U filled in the inside of the through hole 73 is drilled into the gap between the internal component 70 and each of the bare optical fibers 41 and 43 and between the bare optical fibers 41 and 43 at the time of pulling back. Since the gap is maintained, it is possible to maintain the state in which the bare optical fibers 41 and 43 are separated from the other bare fibers 41 and 43 or the internal components 70.

In addition, the amount of pullback of the bare fiber wires 41 and 43 is preferably The protruding length from the front end surface 65A is also slightly small, so that the front ends of the bare fibers 41 and 43 are slightly exposed from the front end surface 65A of the tubular portion 65 toward the front after being pulled back. By doing so, the portion protruding from the front end surface 65A among the bare optical fibers 41 and 43 can be finally removed, and the front ends of the bare fibers 41 and 43 can be aligned with the front end surface 65A of the cylindrical portion 65.

After that, in the fifth step, as shown in Figure 21, The operation of assembling the protective tube 50, the plug 80, and the type tube 90 to the bare optical fibers 41 and 43 is performed. Then, in the sixth step, as shown in Fig. 22, the optical fiber bare wires 41, 43 are pulled out to the accessory body 61. The portion is bent together with the protective tube and accommodated in the accommodating portion 63 of the fitting body 61. Thereafter, the cover member 67 to which the adhesive is applied to the back surface is attached to the accessory body 61. Thereby, the rear surface of the fitting main body 61 is in a state of being closed by the lid member 67.

Then, the hardenability applied in the third step is then After the agent U is hardened, the seventh step is carried out. In the seventh step, a work such as a grinder or a sander is used to grind the front end portion of the tubular portion 65. By the grinding operation, the portion exposed from the front end surface 65A of the tubular portion 65 (the portion B shown in Fig. 22, and the front end of the inner part 70 or the front end of the bare fiber lines 41, 43) can be removed, and As shown in Fig. 3, the front end of the inner member 70 and the front end of the bare optical fibers 41 and 43 are formed to be flush with the front end surface 65A of the tubular portion 65. With the above, the coaxial fiber tip 30 can be manufactured.

3. Effect description

In the coaxial fiber-optic head 30, since the position of the bare fiber 43 is restricted by the position regulating portion 75 provided in the internal component 70, the offset (eccentricity) of the bare fibers 41 and 43 is less likely to occur. Therefore, the coaxial alignment accuracy of the bare fibers 41 and 43 can be improved. Further, since the bare optical fibers 41 and 43 can be fixed in a coaxial arrangement by the fixed layer 77, the coaxial arrangement is not lost due to the change in the positional relationship of the bare fibers 41 and 43 during use. Original shape. Further, since the position regulating portion 75 has a linear shape along the axial direction of the internal component 70, the bare optical fiber 43 inserted into the internal component 70 is modeled after the position regulating portion 75. Straight line shape. Therefore, since the bare optical fiber 43 is not easily bent inside the internal component 70, the coaxial arrangement accuracy becomes high. In addition, when the position regulating portion 75 is formed into a linear shape in advance, the position regulating portion 75 can function as a guide for guiding the bare optical fiber 43 to the axial front side when the through hole 73 is inserted. The advantage of inserting the bare fiber strand 43 into the inner part 70 is easy.

Moreover, the filling operation of the curable adhesive U is, for example, It is considered that the bare optical fibers 41 and 43 are inserted before the through holes 73 of the internal component 70. However, when the curable adhesive U is filled in advance, the insertion resistance when the bare optical fibers 41 and 43 are inserted into the through holes 73 is increased, and the assembly workability is inferior. In this regard, in the method of manufacturing the coaxial optical fiber head 30 disclosed in the present specification, first, the optical fiber bare wires 41 and 43 are inserted through the internal component 70, and then the bare optical fiber coated with the curable adhesive U at the front end portion is applied. 41 and 43 are pulled back inside the inner part 70, whereby the hardenable adhesive U is filled in the through hole 73 of the inner part 70. As a result, the insertion resistance when the bare optical wires 41 and 43 are inserted into the internal component 70 is reduced, so that the assemblability is excellent and the manufacturing efficiency is high.

Further, in the present embodiment, the front end is formed from a cylindrical shape. The bare metal wires 41 and 43 are pulled back in a state where the front end surface 65A of the portion 65 is slightly exposed, and the exposed front end is finally removed, whereby the front ends of the optical fiber bare wires 41 and 43 are processed to be the same as the front end surface 65A of the cylindrical portion 65. flat. By doing so, it is possible to reduce the unevenness of the position of the end of the bare wire, and as a result, the distance from the object to be detected to the end of the bare wire can be maintained, and the detection accuracy of the optical fiber sensor 10 can be improved.

<Other Embodiments>

The present invention is not limited to the embodiments described above with reference to the drawings, and the following embodiments are also included in the technical scope of the present invention.

(1) In the present embodiment, as a configuration example of the coaxial optical fiber bare wire 40, the bare fiber of the light receiving line is arranged at equal intervals on the concentric circle L centering on the bare optical fiber 41 for light projection. Example of 43. The arrangement of the bare optical fibers 41 and 43 is not limited to the arrangement disclosed in the embodiment. For example, the arrangement for light projection and light reception may be reversed, and the bare optical fiber 43 for light reception may be disposed on the center side. The bare fiber line 41 for light projection is arranged at equal intervals on the concentric circles centered on the bare fiber line 43.

(2) In the present embodiment, although the display is limited to the position The portion 75 is formed in the front half of the inner member 70, but may be formed in the total length of the inner member. Further, in the embodiment, the position regulating portion 75 is formed in a circular cross section. However, as long as the positional deviation of the bare optical fiber 43 can be prevented, for example, a trapezoidal shape or the like may be employed.

Claims (5)

A coaxial fiber-optic head comprising: a front end fitting having a tubular portion having a shaft hole opened in the front; and a cylindrical inner member attached to the shaft hole of the tubular portion; And a coaxial optical fiber bare wire in which the front end fitting is mounted while being inserted into the internal component, and is centered on a bare fiber of one of the bare optical wires for light projecting or light receiving, Aligning the bare fiber of the other side with a plurality of concentric circles; and fixing a layer formed in the inner part for fixing the coaxial fiber bare wire interposed in the inner part to be non-displaceable a state in which the inner peripheral wall of the inner member is formed with a position restricting portion that restricts a position of the bare optical fiber on the other side at equal intervals in the circumferential direction, and the position restricting portion is along an axial direction of the inner member. a straight shape; a ridge is provided on a peripheral surface of the inner part, and the rib is abutted against a hole wall formed in the shaft hole of the cylindrical portion to center and front of the inner part Central cylindrical portion of uniform manner the internal components positioned in the cylindrical portion; the outer circumferential surface of the inner element, coated with the adhesive for the inner part is fixed to the shaft hole. A coaxial optical fiber head according to claim 1, wherein The position restricting portion is formed in a circular cross section. The coaxial type optical fiber head according to claim 1 or 2, wherein a front end portion of the inner part is provided with a head having a positioning surface, and the head portion is formed by the shaft hole formed in the cylindrical portion The hole edge abuts, and the inner part is positioned in the cylindrical portion such that the center of the inner part coincides with the center of the cylindrical portion. A fiber optic sensor, comprising: a sensor body portion; and the coaxial fiber optic head according to any one of claims 1 to 3, which is fixed to the coaxial fiber The connector portion at the end of the bare wire is attached to the sensor body portion. A method for manufacturing a coaxial optical fiber head, wherein a bare fiber of one of the bare optical wires for light projecting or light receiving is centered on a bare fiber of the other side, and a plurality of bare fibers of the other side are arranged on a concentric circle. A method of manufacturing a coaxial optical fiber head in which a front end fitting is attached to a front end portion of a coaxial optical fiber bare wire, and a method of forming a position restricting portion at equal intervals in a circumferential direction with respect to an inner peripheral wall and having an outer peripheral surface a step of attaching the inner part of the tubular shape to the shaft hole formed in the tubular portion of the front end fitting, the position restricting portion having a function of restricting the position of the bare optical fiber on the other side and becoming along the shaft a shape extending in a straight line; the protrusion is formed by abutting against a shaft hole formed in the tubular portion of the distal end fitting such that a center of the inner member coincides with a center of the tubular portion The part is positioned in the aforementioned cylindrical portion; and By aligning the bare optical fiber on the other side of the optical fiber between the position regulating portions, the bare fiber of the light projecting and receiving light is assembled so that the front end portion penetrates the cylindrical portion of the internal component. a step of applying the adhesive to the front end of the bare fiber of the light projecting or receiving light that penetrates the tubular portion; and a process of applying the adhesive to the bare fiber of the front end portion a step of pulling back the inner part side; and removing a portion protruding from the front end surface of the cylindrical portion after pulling back, and forming a front end of the bare fiber line to be flush with a front end surface of the cylindrical portion; The step of attaching the inner member to the shaft hole formed in the tubular portion is to insert the inner member into the shaft hole of the tubular portion after applying an adhesive to the outer peripheral surface.