JP2017198630A - Displacement gauge - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a displacement gauge capable of highly accurately detecting a displacement of a measuring object.SOLUTION: A displacement gauge comprises: an optical fiber 2; a fixed holding part 3; a movement holding part 4 freely movable to the fixed holding part 3; a sensor element 2h provided in a portion of the optical fiber between the fixed holding part 3 and the movement holding part 4 and changing mode of light for detection according to a bent state of its own; and a displacement detecting part including a movable part which applies a force to the movement holding part 4 by moving in association with generation of a displacement of a measuring object. The optical fiber 2 comprises an optical propagation part 2d including a core and a clad formed of quarts glass, and a coating part 2e coating the optical propagation part 2d. The optical propagation part 2d is exposed from the coating part 2e at least between the movement holding part 4 and the fixed holding part 3.SELECTED DRAWING: Figure 4

Description

  The present invention relates to a displacement meter.

  Conventionally, an optical sensor element which is an optical fiber having a length shorter than that of the optical fiber sensor main body having a core having a core diameter different from the core of the optical fiber main body, which is an optical fiber composed of a core and a clad. There is known an optical fiber for a sensor including (see Patent Document 1).

  By measuring the Rayleigh scattered light due to light leakage at the interface between the main line body and the optical sensor element of Patent Document 1, it is possible to detect distortion or the like of the main line body.

  Patent Document 2 discloses a fixed holding unit that holds a part of such a sensor optical fiber connected to an OTDR (Optical Time-Domain Reflectometer), a predetermined distance from the fixed holding unit. An optical fiber for a sensor having a movable holding part that is movably arranged on the fixed holding part and holds the other part of the optical fiber for the sensor that is in a line-symmetrical position with the part around the optical sensor element is proposed. Has been.

  The sensor optical fiber has a direction connecting a point at which the movement holding unit holds the sensor optical fiber and a point at which the fixing holding unit holds the sensor optical fiber, such as the movement holding unit approaching the fixed holding unit. When a stress is applied in the same direction, the sensor optical fiber is bent around the optical sensor element in accordance with the stress, and when the stress is released, the mechanism returns to the bent state.

  In this sensor optical fiber, when distortion occurs in the measurement object connected to the movable holding unit, the movable holding unit approaches the fixed holding unit and the optical sensor element bends, causing loss of optical transmission to the sensor optical fiber. Occurs. In other words, by detecting this optical transmission loss with the OTDR connected to the sensor optical fiber, it is possible to detect the distortion of the measurement object connected to the moving holding unit.

Japanese Patent No. 3180959 Japanese Patent No. 4310606

  In order to protect the optical propagation part of the optical fiber called the core and the clad made of quartz glass from external pressure, it may be covered with a covering part such as plastic covering the glass element wire. However, the bending mode may be different for the same displacement due to the influence of the hysteresis of the covering portion such as plastic. As a result, there is a possibility that the detection accuracy of the displacement of the measurement object may be lowered.

  In view of such a problem, an object of the present invention is to provide a displacement meter capable of detecting a displacement of a measurement object with high accuracy.

The displacement meter of the present invention is
An optical fiber configured to be connectable to a light incident part for receiving detection light and a light receiving part for receiving the detection light;
A fixed holding portion that is fixed in position and holds the first portion of the optical fiber;
A movable holding portion that is movable with respect to the fixed holding portion and holds the second portion of the optical fiber;
A sensor element that is provided in a third portion of the optical fiber between the fixed holding portion and the movable holding portion, and changes a mode of the detection light according to its bending state;
A displacement detection unit configured to include a movable unit that is connectable to the measurement target and moves with the occurrence of the displacement of the measurement target, and applies a force to the movement holding unit;
The optical fiber includes a light propagation portion configured to include a core and a clad formed of quartz glass, and a covering portion that covers the light propagation portion,
The light propagation part is exposed from the covering part at least between the movement holding part and the fixed holding part.

  According to the displacement meter of the present invention, when the movable part moves with the occurrence of the displacement of the measurement object, force is applied to the movement holding part, and the movement holding part also moves.

  When the movable holding portion moves, the optical fiber between the movable holding portion and the fixed holding portion is bent, so that the optical fiber between the moving holding portion and the fixed holding portion is provided in the third portion. The sensor element is bent. Depending on the bending state of the sensor element, the sensor element changes the mode of detection light received by the light receiving unit.

  In other words, the change in the mode of the detection light received by the light receiving unit is measured, whereby the bending of the optical fiber and the displacement of the measurement object are detected.

  Moreover, according to the displacement meter of the said structure, even when the optical fiber between the said movement holding | maintenance part and a fixed holding | maintenance part bends according to the displacement of a measuring object, since the light propagation part of an optical fiber is exposed, In addition, it is possible to eliminate the influence of hysteresis due to the covering portion such as plastic. In other words, it is possible to accurately detect the displacement mode of the measurement object by detecting the change in the detection light indicating the bending mode of the optical fiber.

In the displacement meter of the present invention,
Each of the movement holding unit and the fixed holding unit has a guide groove that holds the optical fiber while the sensor element side is inclined toward the bending direction side of the sensor element with respect to the movement direction of the movement holding unit. Is preferred.

  According to the displacement meter of the said structure, the said sensor element side will be inclined to the bending direction side of the said sensor element rather than the moving direction of a movement holding part by hold | maintaining an optical fiber with a guide groove. For this reason, in the initial state, the optical fiber between the guide groove and the sensor element is substantially linear, thereby eliminating the influence of the hysteresis of the optical fiber and improving the reproducibility of the displacement.

  In the displacement meter having the above configuration, it is preferable that the light propagation portion of the optical fiber is exposed from the covering portion to a part of the guide groove on the sensor element side.

  When the movable holding portion moves, the optical fiber between the movable holding portion and the fixed holding portion is bent. At this time, the optical fiber held in the guide groove is also bent on the sensor element side, and when the optical fiber comes into contact with the guide groove, the amount of bending is limited.

  According to the displacement meter of the configuration configured in view of this point, since the light propagation portion is exposed from the covering portion to a part of the guide groove on the sensor element side, the optical fiber is connected to the guide groove of each holding portion. The range that can be bent without contact is relatively wide. Thereby, the restriction | limiting of the bending of the optical fiber resulting from the guide groove and optical fiber of each holding | maintenance part contacting is eased. Thereby, the bending state of the optical fiber more reflects the displacement of the measurement target. Thereby, the displacement of the measuring object can be detected with high accuracy.

In these displacement meters,
Each of the movable holding part and the fixed holding part includes a lid part and a holding base,
It is preferable that the guide groove is provided on the upper surface of the holding table so as to be visible.

  According to the displacement meter of the configuration, since the guide groove that can be visually recognized is provided on the upper surface of the holding base, whether or not the optical fiber is properly attached when the optical fiber is attached to the guide groove. Can be visually recognized. Damage caused by improperly attaching the optical fiber can be prevented by performing an operation such as attaching the lid to the holding table on the condition that the optical fiber is properly attached. .

FIG. 1A is a plan view of the displacement meter when the movable portion is in the initial position, and FIG. 1B is a plan view of the storage chamber of the displacement meter when the movable portion is in the second position. The figure at the time of abbreviate | omitting illustration of a lid | cover in a figure. 2A is a sectional view taken along the line IIA-IIA in FIG. 1B, FIG. 2B is a sectional view taken along the line IIB-IIB in FIG. 1A, FIG. 2C is a sectional view taken along the line IIC-IIC in FIG. FIG. 2E is a cross-sectional view of the displacement meter when the movable portion is at the fourth position. FIG. 3A is a cross-sectional view of the optical fiber between the optical fiber inlet / outlet and the fixed holding part and between the moving holding part and the optical fiber inlet / outlet, and FIG. 3B is an optical fiber between the fixed holding part and the moving holding part. Sectional drawing and FIG. 3C are sectional drawings of the optical fiber containing a sensor element. 4A is a right side view of the fixed holding portion, FIG. 4B is a plan view showing the arrangement of the fixed holding portion, the moving holding portion, and the optical fiber, and FIG. 4C is the fixed holding portion and the movement before mounting the lid portion. FIG. 4D is a left side view of the movable holding unit.

  An embodiment of the present invention will be described with reference to FIGS. 1A to 4D.

(Configuration of displacement meter)
As shown in FIGS. 1A, 1B and 2A to 2E, the displacement meter 1 includes a lid 1a and a storage chamber 1b. The storage chamber 1b corresponds to the “arrangement board” of the present invention.

  The lid 1a is fixed by a bolt 1d that is screwed into the bolt hole 1c of the accommodation chamber 1b.

  As shown in FIGS. 1A, 1B, and 2A to 2E, the storage chamber 1b is provided with a space. As shown in FIGS. 1A, 1B, and 2A to 2E, the optical fiber 2, the fixed holding unit 3, the moving holding unit 4, It is connected to the fiber fixing unit 5 and the measurement object, and is movable in the first direction D1 that is the direction toward the left side of FIG. 1A and the second direction D2 that is the reverse direction of the first direction D1 in accordance with the displacement of the measurement object. A part of the movable portion 6, an initial position stopper 7, and an excessive bending prevention stopper 8 are accommodated.

  As shown in FIG. 1A and FIG. 1B, the optical fiber 2 makes almost one turn along the wall of the accommodation chamber 1 b from the optical fiber entrance / exit 10 of the accommodation chamber 1 b, and the first portion is held by the fixed holding portion 3 and moved. The holding portion 4 holds the second portion, the optical fiber fixing portion 5 holds the fourth portion, and makes one round along the wall of the receiving chamber 1b from the fourth portion, and reaches the optical fiber entrance / exit 10 of the receiving chamber 1b. Is configured to do.

  This arrangement of the optical fiber 2 avoids an excessive curvature of the shape of the optical fiber 2, thereby reducing optical transmission loss. Moreover, since the optical fiber 2 is disposed along the wall of the storage chamber 1b, the optical fiber 2 can be easily installed inside the storage chamber 1b.

  The optical fiber 2 between the movement holding part 4 and the optical fiber fixing part 5 forms a U-shaped bent part 2a bent in the second direction D2.

  The optical fiber 2 i exposed from the optical fiber entrance / exit 10 is connected to the OTDR 9.

  As shown in FIGS. 3A to 3C, the configuration of the optical fiber 2 is different at each location.

  As shown in FIG. 3A, the optical fiber 2 includes a core 2b and a clad 2c between the optical fiber entrance 10 and the fixed holding portion 3 and between the movement holding portion 4 and the optical fiber entrance 10. A portion 2d and a covering portion 2e are provided.

  The core 2b is made of a material having a higher refractive index than that of the clad 2c, and the core 2b is covered with the clad 2c. Light propagates in the core 2b by total reflection due to the difference between the refractive index of the core 2b and the refractive index of the cladding 2c.

  Each of the core 2b and the clad 2c is made of quartz glass. Instead, each of the core 2b and the clad 2c may be formed of a material having a high refractive index such as plastic.

  The covering portion 2e covers the light propagation portion 2d in order to protect the light propagation portion 2d from external pressure. The covering portion 2e is made of plastic, for example.

  As shown in FIG. 3B, in the optical fiber 2, the light propagation part 2d including the core 2b and the clad 2c is exposed between the fixed holding part 3 and the movement holding part 4.

  The optical fiber 2 is connected to the core 2b in the third portion of the optical fiber 2 that is the central portion between the fixed holding portion 3 and the movable holding portion 4, and as shown in FIG. 3C. A sensor element 2h including a core 2f having a diameter different from that of 2b and a clad 2g covering the core 2f is formed. As the sensor element 2h, for example, a sensor element disclosed in Patent Document 1 can be adopted.

  As shown in FIGS. 2B to 2E and 4A, the fixed holding unit 3 includes a fixed holding base 3a and a fixed lid 3b.

  The fixed holding base 3a is formed in a rectangular parallelepiped shape, and as shown in FIGS. 4A to 4C, the sensor element 2h side is inclined by a predetermined angle θ with respect to the first direction D1 toward the bending direction D3 side of the sensor element 2h. And a first guide groove 3c through which the optical fiber 2 passes.

  The fixed lid portion 3b is formed on a flat plate.

  With the optical fiber 2 passed through the first guide groove 3c, the bolt hole (not shown) provided in the raised portion 1g of the storage chamber 1b and the bolt holes 3d and 3e provided in the fixed holding base 3a are respectively screwed. The fixed holding base 3a and the fixed lid 3b are fixed to the raised portion 1g of the storage chamber 1b by the bolts 1e and 1f to be combined.

  As shown in FIGS. 2B to 2E and 4D, the movement holding unit 4 includes a movement holding base 4a, a movement holding plate 4b, and a movement support base 4c. The movable holding base 4a is formed in a rectangular parallelepiped shape, and as shown in FIGS. 4B to 4D, the sensor element 2h side is inclined with respect to the first direction D1 by a predetermined angle θ toward the bending direction D3 side of the sensor element 2h. And the 2nd guide groove 4d of the grade which the optical fiber 2 passes is provided. The movement holding unit 4 is located at the initial position P1 in an initial state (a state in which the measurement object connected to the movable unit 6 is not displaced).

  In a state where the optical fiber 2 is passed through the second guide groove 4d, the movable holding table 4a and the movable holding table 4a are moved and held by bolts 4h and 4j which are screwed into bolt holes 4e and 4f provided in the movable holding table 4a and the movable support table 4c. The plate 4b is fixed to the movable support 4c.

  As shown in FIG. 4C, the light propagation part 2d is configured to be exposed a predetermined distance h from the sensor element 2h side of the guide grooves 3c, 4d. Here, the predetermined distance h is such a distance that the light propagation part 2d does not contact the fixed holding part 3 or the movement holding part 4 even if the optical fiber 2 is bent as the movable part 6 is displaced.

  Further, as shown in FIGS. 1A, 1B, and 2A, the movement holding unit 4 is configured so that the posture during movement is constant with respect to the storage chamber 1b by the posture support plate 4i fixed to the storage chamber 1b. Adjusted.

  As shown in FIGS. 1A and 1B, the optical fiber fixing portion 5 is configured by, for example, a screw fixed to the accommodation chamber 1b. The optical fiber fixing part 5 prevents the large displacement of the fourth part of the optical fiber 2 by sandwiching the fourth part of the optical fiber 2 by the wall and floor of the housing chamber 1b and itself.

  The movable portion 6 is formed of, for example, a metal rod, and as shown in FIGS. 1A, 1B, and 2A to 2E, one end portion is exposed from the storage chamber 1b and the other end portion is stored in the storage chamber 1b. ing. The movable part 6 moves in the first direction D1 with the occurrence of distortion of the measurement object connected to one end exposed from the storage chamber 1b, and moves in the second direction D2 with the elimination of the distortion of the measurement object. Is configured to move. The movable part 6 is located at the initial position R1 in an initial state (a state in which the measurement object connected to the movable part 6 is not displaced).

  The measurement object is, for example, a bridge, a tunnel wall, or a large building wall.

  As shown in FIGS. 2B to 2E, the movable portion 6 is inserted into a first insertion hole 4g provided in the movement support base 4c so as to be movable with respect to the movement support base 4c. Further, the movable portion 6 is also inserted into a second insertion hole 1h provided in the portion 1g so as to be movable with respect to the raised portion 1g of the storage chamber 1b.

  The movable part 6 includes a first spring 6b and a second spring 6c on both sides of the movement support base 4c. Coil springs can be employed for the first spring 6b and the second spring 6c, respectively. Instead of this, a compression spring or a tension spring may be employed.

  The 1st spring 6b is attached to the 2nd direction D2 side seeing from the movement support stand 4c. One end of the first spring 6b is in contact with the protrusion 6d provided on the movable portion 6 on the second direction D2 side, and the other end of the first spring 6b is in contact with the movable support 4c. When the movable part 6 moves in the first direction D1, the protruding part 6d also moves in the first direction D1. At this time, the force of the first spring 6b works due to the contraction of the first spring 6b, and the movable support 4c is biased in the first direction D1.

  The 2nd spring 6c is attached to the 1st direction D1 side seeing from the movement support stand 4c. One end of the second spring 6c is in contact with the raised portion 1g of the storage chamber 1b, and the other end of the second spring 6c is in contact with the movable support 4c. When the movable part 6 moves in the first direction D1, the movement support 4c also moves in the first direction D1 by the force of the first spring 6b. At this time, the force of the second spring 6c works due to the contraction of the second spring 6c, and the movable support 4c is urged in the second direction D2, which is opposite to the first direction D1.

  Due to the force of the second spring 6c, the displacement amount x1 from the initial position P1 to the second position P2 of the movable support 4c is greater than the displacement amount x2 from the initial position R1 to the second position R2 of the movable portion 6. Get smaller.

  Specifically, assuming that the spring constant of the first spring 6b is n and the spring constant of the second spring 6c is m, the displacement amount x1 of the movable support base 4c is expressed by the following equation (1).

  It should be noted that the first spring 6b and the second spring suitable for realizing the moving amount of the moving support 4c that can avoid the damage of the optical fiber 2 from the assumed maximum value of the displacement amount of the measurement object and Expression (1). The spring 6c may be selected.

  When the movable unit 6 moves in the first direction D1, the movement holding unit 4 moves in the first direction D1, as shown in FIG.

  As the movement holding unit 4 moves, the optical fiber 2 is pulled, and the bent portion 2a of the optical fiber 2 contracts. Since the bending portion 2a of the optical fiber 2 contracts, the tensile force of the optical fiber 2 due to the movement of the movement holding portion 4 is absorbed, so the portion of the optical fiber 2 between the optical fiber fixing portion 5 and the optical fiber entrance / exit 10 Hardly move. Thereby, the damage of the optical fiber 2 is avoided.

  Further, as the movement holding unit 4 moves, the optical fiber 2 between the fixed holding unit 3 and the movement holding unit 4 is bent. Thereby, the sensor element 2h is also bent. If the sensor element 2h is bent, the light transmitted through the optical fiber 2 can be leaked at the interface of the sensor element 2h, so that a transmission loss occurs depending on the bent state. Thereby, the mode of the detection light (for example, Rayleigh scattered light) received by the OTDR 9 changes.

  Further, when the force in the first direction D1 applied to the movable part 6 is eliminated, the force for returning the movable holding part 4 and the movable part 6 to the initial positions P1 and R1 by the first spring 6b and the second spring 6c. (Force in the second direction D2) acts, and the movable holding portion 4 and the movable portion 6 move in the second direction D2 to return to the initial positions P1 and R1.

  The protrusion 6d is formed of, for example, an E ring, and is fitted into a groove provided in the circumferential direction of the movable portion 6. A reduced diameter portion is provided adjacent to the second direction D2 of the groove. The diameter of the reduced diameter portion is formed to be smaller than the diameter of most of the movable portion 6. As a result, when a large force is applied in the second direction D2 from the first spring 6b to the protruding portion 6d after the movement holding portion 4 abuts against the excessive bending prevention stopper 8, the protruding portion 6d comes off the groove and contracts. Slide in the second direction D2 of the diameter portion. Thereby, it can be avoided that an excessive load is applied to the first spring 6b. The protrusion 6d that has slid in the second direction D2 of the reduced diameter portion is movable until the movable portion 6 comes into the groove by coming into contact with the wall of the storage chamber 1b when the movable portion 6 returns to the initial position R1. 6 in the first direction D1.

  The initial position stopper 7 is configured integrally with the storage chamber 1b and is provided in the second direction D2 when viewed from the movement holding portion 4. As shown in FIG. 2B, the initial position stopper 7 is disposed at a position where the initial position P1, R1 of the movable portion 6 is in contact with the movable holding portion 4 in a state where the measurement target is not displaced. Yes. The initial position stopper 7 stabilizes the initial position of the movement holding unit 4 and prevents excessive displacement of the movement holding unit 4 in the second direction D2.

  The excessive bending prevention stopper 8 is configured integrally with the storage chamber 1b and is disposed in the first direction D1 when viewed from the movement holding portion 4. As shown in FIG. 2D, the excessive bending prevention stopper 8 is provided so as to be able to come into contact with the movement holding part 4 when the movement holding part 4 is moved by a predetermined distance in the first direction D1.

  When the movement holding unit 4 comes into contact with the excessive bending prevention stopper 8, the movement holding unit 4 stops moving. For example, as shown in FIG. 2E, when the movable portion 6 is at the third position R3 and the movable holding portion 4 is in contact with the excessive bending prevention stopper 8 at the third position P3, the movable portion is further moved in the first direction D1. Even when 6 moves by the displacement amount x3 and is positioned at the fourth position R4, the movement of the movable part 6 is absorbed by the contraction of the first spring 6b. It remains P3. Thereby, the situation where the bending amount of the sensor element 2h between the fixed holding part 3 and the movement holding part 4 exceeds the intention of the designer is avoided.

  The OTDR 9 includes a light incident portion 9a for injecting inspection light into the optical fiber 2, a light receiving portion 9b for receiving inspection light such as Rayleigh scattered light, and a measurement target based on the received inspection light. A displacement amount estimation unit 9c for estimating the estimated displacement amount ex2. Instead of the OTDR 9, the displacement meter 1 received light with a light incident part that is a light emitting element such as an LED (light-emitting diode, light emitting diode) and a light receiving part that is a light receiving element such as a PD (photodiode, photodiode). You may provide the displacement amount estimation part which estimates the estimated displacement amount of a measuring object based on the light for a test | inspection.

  The displacement amount estimation unit 9c estimates the bending mode of the sensor element 2h based on inspection light such as Rayleigh scattered light received by the light receiving unit 9b, and calculates the estimated movement amount ex1 of the movement holding unit 4 from the bending mode. presume.

  Subsequently, the displacement amount estimation unit 9c estimates the estimated displacement amount ex2 of the measurement target from the estimated movement amount ex1 by the following equation (2). Expression (2) is an expression derived from Expression (1), where n is the spring constant of the first spring 6b and m is the spring constant of the second spring 6c.

(Function and effect)
According to the displacement meter 1, when the movable part 6 moves with the occurrence of the displacement of the measurement object, a force is applied to the movement holding part 4, and the movement holding part 4 also moves.

  When the movement holding unit 4 moves, the optical fiber 2 between the movement holding unit 4 and the fixed holding unit 3 bends. As a result, the third optical fiber 2 between the movement holding unit 4 and the fixed holding unit 3 is bent. The sensor element 2h provided in the portion is bent. According to the bending state of the sensor element 2h, the sensor element 2h changes the aspect of the detection light received by the light receiving unit 9b.

  In other words, the change in the mode of the detection light received by the light receiving unit 9b is measured, whereby the bending of the optical fiber 2 and the displacement of the measurement object are detected.

  Moreover, according to the displacement meter 1 of the said structure, even when the optical fiber 2 between the movement holding | maintenance part 4 and the fixed holding | maintenance part 3 bends according to the displacement of a measuring object, the light propagation part 2d of the optical fiber 2 is Since it is exposed, it is possible to eliminate the influence of hysteresis due to the covering portion 2e made of plastic or the like. In other words, by detecting a change in light for detection indicating the bending mode of the optical fiber 2, the mode of displacement of the measurement object can be detected with high accuracy.

  Further, according to the displacement meter 1 of the configuration, the optical fiber 2 is held by the guide grooves 3c and 4d, so that the sensor element 2h side is closer to the bending direction D3 side of the sensor element 2h than the moving direction of the moving holding unit 4 is. Will be inclined to. For this reason, in the initial state, the optical fiber 2 between the guide grooves 3c and 4d and the sensor element 2h is substantially linear, so that the influence of the hysteresis of the optical fiber 2 is eliminated and the reproducibility of the displacement is improved.

  Further, when the movement holding unit 4 moves, the optical fiber 2 between the movement holding unit 4 and the fixed holding unit 3 is bent. At this time, the optical fiber 2 held in the guide grooves 3c and 4d is also bent on the sensor element 2h side. When the optical fiber 2 comes into contact with the guide grooves 3c and 4d, the amount of bending is limited.

  According to the displacement meter 1 configured in view of this point, the light propagation portion 2d is exposed from the covering portion 2e up to a part of the guide grooves 3c and 4d on the sensor element 2h side. However, the range that can be bent without contacting the guide grooves 3c and 4d of the holding portions 3 and 4 is relatively wide. Thereby, the restriction | limiting of the bending of the optical fiber 2 resulting from the contact of the guide grooves 3c and 4d of each holding | maintenance part 3 and 4 and the optical fiber 2 is eased. Thereby, the bending state of the optical fiber 2 more reflects the displacement of the measurement object. Thereby, the displacement of the measuring object can be detected with high accuracy.

  Moreover, according to the displacement meter 1 of the said structure, since the guide grooves 3c and 4d which can be visually recognized are provided in the upper surface of the holding bases 3a and 4a, when attaching the optical fiber 2 to the guide grooves 3c and 4d, An operator can visually check whether or not the optical fiber 2 is properly attached. The optical fiber 2 is improperly attached by performing an operation such as attaching the lid portions 3b and 4b to the holding bases 3a and 4a on the condition that the optical fiber 2 is properly attached. The damage caused by the can be prevented.

  DESCRIPTION OF SYMBOLS 1 ... Displacement meter, 1a ... Lid, 1b ... Storage chamber, 2 ... Optical fiber, 2a ... Bending part, 2h ... Sensor element, 3 ... Fixed holding part, 4 ... Moving holding part, 5 ... Optical fiber fixing part, 6 ... Movable part, 6b... First spring, 6c... Second spring, 7... Initial position stopper, 8.

Claims (4)

An optical fiber configured to be connectable to a light incident part for receiving detection light and a light receiving part for receiving the detection light;
A fixed holding portion that is fixed in position and holds the first portion of the optical fiber;
A movable holding portion that is movable with respect to the fixed holding portion and holds the second portion of the optical fiber;
A sensor element that is provided in a third portion of the optical fiber between the fixed holding portion and the movable holding portion, and changes a mode of the detection light according to its bending state;
A displacement detection unit configured to include a movable unit that is connectable to the measurement target and moves with the occurrence of the displacement of the measurement target, and applies a force to the movement holding unit;
The optical fiber includes a light propagation portion configured to include a core and a clad formed of quartz glass, and a covering portion that covers the light propagation portion,
The displacement meter, wherein the light propagation part is exposed from the covering part at least between the movement holding part and the fixed holding part. The displacement meter according to claim 1,
Each of the movement holding unit and the fixed holding unit has a guide groove that holds the optical fiber while the sensor element side is inclined toward the bending direction side of the sensor element with respect to the movement direction of the movement holding unit. Displacement meter characterized by The displacement meter according to claim 2,
The optical fiber has a light propagation portion exposed from the covering portion to a part of the guide groove on the sensor element side. The displacement meter according to claim 2 or 3,
Each of the movable holding part and the fixed holding part includes a lid part and a holding base,
The said guide groove is provided in the upper surface of the said holding stand so that visual recognition is possible, The displacement meter characterized by the above-mentioned.