JPS61284625A - Optical fiber sensor - Google Patents

Abstract

PURPOSE:To easily make a curve having a small radius of curvature and to speed up a response to variation in the quantity of light by fitting alternate holders to plural plural plate type jigs which move reciprocally. CONSTITUTION:A sensor consists of the plate type jigs 6A and 6B which have plural holders 8a and 8b fitted alternately at specific intervals and move reciprocally and an optical fiber 1 which is held on the respective holders in an axially movable state and extends linearly. When either or both of the plate type jigs 6A and 6B move by a specific stroke, alternate C-shaped holders 8a fitted to the jig 6A or 6B move up, for example, and the other holders 6b move down to displace the held linear optical fiber 1 zigzag. When the quantity of the displacement is set a little bit larger than a critical angle, part of light is transmitted from the core to the clad at plural positions and detected as large variation in the quantity of light.

Description

[Detailed Description of the Invention] [Field of Industrial Application] This invention relates to an optical fiber (transparent fiber such as glass or plastic, etc.) that transmits light incident from one end to the other end.
or bundled together to transmit a light image, which has characteristics such as small diameter, light weight, flexibility, non-induction, and non-crosstalk, and is used in large-capacity optical communication systems). This invention relates to a fiber sensor, and in particular, the invention relates to a fiber sensor, and in particular, to
[This relates to an optical fiber sensor that can sensitively react to changes in the amount of light and can respond to this load with sufficient speed.

[Conventional technology]

Figure 5 shows a cross-sectional view of a conventional optical fiber cut in the longitudinal direction; , Fig. 7 is a side view showing a conventional optical fiber flexor constructed of an optical fiber and a pair of jigs for bending the optical fiber, and Fig. 8 is an explanatory diagram of the principle of light transmission in the optical fiber. First, in Figures 5 (4) and (E), (1) is the optical refractive index (n, ), and a core (1a) with a circular cross section and a core (1a) surrounding this core with an optical refractive index (n2). cladding (1b);
With the protective layer (1C) that protects the surface of this cladding,
(3) is the light transmitted in the core (1a), (5') is the core (1a) and the cladding (1a).
(3F) is the light reflected at the interface (2) between the core (1a) and the cladding (1b), and , In Fig. 8, (θ,) is the incident angle formed by the light (3) transmitted in the core (1a), the interface (2) between the core (18), and the cladding (1b), (θ2 ) is the light transmitted through the interface (2) (three refraction angles, (θ.) is the incident angle (θ1)
The 0th order, which is the critical angle when is above a certain value, and the 7th order
In the figure, (the force is applied to the uneven part (4a) on the opposing surface, (4
b) A pair of jigs (4A) that formed .

(4B) and the uneven part (4a).
.

(4b) The optical fiber (1
) In general, in this tip fiber, the incident angle (θ, ) of the light (3) transmitted in the core (1a) as shown in FIG.
is less than the critical angle (θ2), as shown in Figure 5 (4), the light (6I) that passes through the cladding (1b) and the light that is reflected at the interface (2) and enters the core (1a). If the incident angle (θ1) of the light (3) transmitted in the core (1a) is greater than or equal to the critical angle (θ0), it will be totally reflected and the light (3) will be transmitted into the core (1a). ) transmitting light (3
It becomes one. Therefore, in the case of the straight optical fiber (1) shown in FIGS. 5A and 5K, the loss of the light (3) is relatively small due to the above-mentioned total reflection effect.

However, when the optical fiber (1) is bent to a predetermined radius as shown in FIG.
1, light transmission occurs in the state of total reflection described above, but when the bend is steep, light (3) passes through the boundary surface (2).
When the angle tangent to the optical fiber (θ) becomes less than the critical angle (θ., will no longer be carried out.

The conventional optical fiber sensor (7) shown in FIG.
, (4B) When the optical fiber (1) is bent into a wave shape by pressing the concavo-convex portions (4a) and (4b), the amount of light transmitted changes for the reasons mentioned above.
Both sides of optical fiber (1)! Both jigs (4A)
, (4B) can be used as a sensor that detects the amount of physical displacement by changing the amount of light.

[Problem that the invention seeks to solve]

In the conventional optical fiber sensor described above, the uneven portions (4a) and (4) of the pair of jigs (4A) and (4B)
Since the optical fiber (1) is bent into a wave shape by the pressure in step b), it is detected as a change in light intensity, so both jigs (4A) and (4B) were turned against each other and returned to their original positions. When the optical fiber (1) is returned to a position where there is no change in light intensity, it must return to its original state by its own elastic restoring force, but this tip fiber has no elastic restoring force due to its constituent material. weak,
It has the disadvantage that it cannot respond quickly enough to changes in the load on the jig. In addition, in the conventional optical fiber sensor described above, in order to prevent large bending stress from being applied to the optical fiber (1), a jig (4
person”), (4B) uneven parts (4a), (4b)
◇Furthermore, in conventional optical fiber analyzers, in order to increase the change in light intensity, it is necessary to treat the irregularities (4a) and (4b) with small curvature radii. Ingredients (4A), (
It is necessary to provide a large number of these uneven portions (4a) on the opposing surface of 4B).

When the optical fiber (1) is repeatedly pressed and released by (4b), the optical fiber (1) at the part where the uneven part contacts
) is easily fatigued and cannot withstand long-term use. This invention was made with attention to this point, and in order to increase the change in the light intensity of the optical fiber sensor, the optical fiber is bent with a small radius of curvature. The present invention aims to provide an optical fiber sensor that can be easily added to the optical fiber sensor and speeds up the response to changes in light amount due to physical displacement of one optical fiber sensor.

[Means for solving problems]

The optical fiber sensor according to the present invention uses a plurality of holders on the same axis that are alternately attached at predetermined intervals to each of a plurality of plate-shaped jigs capable of reciprocating movement, so that light 7 that extends linearly Aino () is repeatedly deformed and held in a zigzag pattern on the same plane.

[For production]

In this invention, a linearly extending optical fiber is repeatedly displaced in a zigzag pattern by a plurality of holders provided at predetermined intervals on a plurality of jigs capable of reciprocating movement on the same plane. Therefore, the light incident on the optical fiber 7 can be transmitted from the core to the cladding during transmission, or reflected at the interface between the core and the cladding, so that the amount of light can be changed in accordance with the displacement.

[Embodiments of the invention]

Figures 1 to 6 all show one embodiment of the present invention, with Figure 1 being a front view of an optical fiber sensor, and Figure 2 being a front view of an optical fiber sensor.
FIG. 6 is a cross-sectional view taken along the line (10-(ll[)!) of FIG. 1.

(6A) and (6B) are a plurality of plate-shaped jigs that are slidably superimposed on each other and that one or both of them repeatedly move within a predetermined stroke range, and each of these plate-shaped jigs (6A
), C6B) K is attached to a plurality of C-shaped holders (8a), ('8b) alternately at predetermined intervals via locking screws) (9a), (9b), and these C-shaped Each holder (8a), (8b)
are arranged on the same axis in order to hold the linear optical fiber (1) movably in the axial direction on the same plane. (10a) and (10b) are plate-shaped jigs (6A
).

When only one or both of (6B) are moved repeatedly, each holder (8a) attached to each, (
8b) is an escape hole provided to prevent each jig (6A), (6B) K11r from hitting.◇In addition,
The reason why each of the holders (8a) and (8b) is C-shaped is that a slit for inserting the optical fiber (1) is required inside. In addition, a plurality of plate-shaped jigs (6A), (6
B) is slidably supported at its edge by a guide rail (not shown) K so that it can be smoothly and repeatedly moved.
), (6B) may be a hydraulic cylinder or an electric type.

Since the optical fiber sensor of the present invention is constructed as described above, only one or both of the plate-shaped jigs (6A) and (6B) are arranged in the direction of the arrow as shown in FIGS. 2 and 6. When the plate-shaped jigs (6A) and (6B) are moved by a predetermined stroke, one of the plurality of C-shaped holders (8a) alternately attached to each of the plate-shaped jigs (6A) and (6B) rises, and the other holder (8b) rises. A straight optical fiber that is lowered and held is displaced in a zigzag pattern on the same plane, but if the amount of displacement is set to be slightly greater than the critical angle (θC) mentioned above, the As shown in Figure 8, part of the light (3) is transferred from the core (1a) to the cladding (1b).
), the transmission of light occurs at multiple locations as shown in FIG. 6, and can be detected as a large change in the amount of light.

In addition, FIG. 4 (B) shows another embodiment of the present invention, in which a plurality of plates are connected by a plurality of connection springs Q3, facing each other with a predetermined gap so as to be able to approach and separate from each other. A plurality of holders (8a) are arranged alternately at predetermined intervals on the opposing surfaces of the shaped jigs (6A) and (6B).

(8b) is attached, and a straight optical fiber (1) is inserted and held in the insertion hole αυ drilled in each of the holders so as to be movable in the axial direction on the same plane. By moving only one or both of (6A) and (6B) by a predetermined stroke as shown in FIG. 4 (A) K, a straight optical fiber (1) is formed.
is repeatedly displaced in a zigzag pattern on the same plane, and its operation and effect are similar to those of the above-mentioned embodiment.

〔Effect of the invention〕

As described above, (1) this invention uses a plurality of holders alternately attached at predetermined intervals to each of a plurality of reciprocally movable plate-shaped jigs to connect linearly extending optical fibers on the same plane. Since the zigzag-shaped rod is repeatedly displaced, it responds sensitively to changes in light intensity in response to an external load C2, and is able to respond with sufficient speed to this load C2. In addition, as mentioned above, since a straight optical fiber is held on the same plane by a plurality of holders, it can be moved freely in the axial direction. Optical fiber odor = partial arc even if the optical fiber is displaced; it does not apply large stress or twist, and can protect the optical fiber for long-term use (also has a durable effect). There is.

[Brief explanation of drawings]

Figures 1 to 6 all show one embodiment of the present invention, with Figure 1 being a front view and Figure 2 being (1) - (1) in Figure 1.
) line Cj & Figure 6 is a cross-sectional view taken along
) is a sectional view taken along line 8. Figure 4 (B) shows another embodiment of this invention, Figure 4 (4) is a front view showing another embodiment of this invention, and Figure 4 (CB) is a side view thereof. be. Figures 5 (5) and 8 show conventional optical fiber antennas and optical fibers, and Figure 5 (3)
is a cross-sectional view of a conventional optical fiber cut in the longitudinal direction;
Fig. 5(B) is a longitudinal cross-sectional view thereof, and Fig. 6 is a predetermined radius of curvature I.
7 is a side view showing an optical fiber sensor, and FIG. 8 is an explanatory diagram of the principle of light transmission in an optical fiber. In the figure, (1) is an optical fiber, (6A), (6
B) is a plate-shaped jig, (8a), (8b) holder,
(9a). (9b) is the mounting pusher j-1 (10a), (10b
) is an escape hole. Note that the same reference numerals in the figures indicate the same or corresponding parts. Agent Patent Attorney Tadashi Sato Figure 1 Figure 84 (A) (B) Figure 7 Figure 8

Claims (4)

[Claims] (1) A plurality of plate-shaped jigs capable of reciprocating movement having a plurality of holders installed alternately at predetermined intervals, and a linearly extending light held movably in the axial direction by each of the holders. 1. An optical fiber sensor, characterized in that the optical fiber is repeatedly deformed in a zigzag shape on the same plane by each of the holders. (2) The optical fiber sensor according to claim 1, wherein each holder is formed in a C-shape for inserting an optical fiber. (3) The optical fiber sensor according to claim 1, wherein each holder is arranged on the same axis in order to hold the linear optical fiber on the same plane. (4) The optical fiber sensor according to claim 1, wherein a plurality of reciprocating plate-shaped jigs each having a holder attached thereto are provided with escape holes to prevent collisions between the holders.