JPH10267732A - Optical fiber sensor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To discriminate water and mud by providing a constitution wherein a slit is provided for a transparent optical guide and a detection part is provided so as to be movable in a hollow part within the optical guide. SOLUTION: A hollow part 1A and a slit 1B are provided in the longitudinal direction of an optical rod 1. An optical transmission line 2 comprises an input side optical fiber 3 connected to an optical source 6 and an output side optical fiber 4 connected to a light receiving part 7. A detection part 5 is constructed such that tips of both the fibers 3, 4 are set to face each other. The light made incident to the fiber 3 changes its direction at a cut surface of the tip, comes out of the fiber once and passes through a slit 1B, and thereafter it is reflected by an optical path changer 9 and converged into the fiber 4 through the slit 1B. When mud or the like enters the inside of the slit 1B, the transmission of light is decreased at the slit 1B so that the light transmission incident to the fiber 4 is decreased. Accordingly, based on variation of the quantity of light received at the light receiving part 7 the existence of mud in the vicinity of the slit 1B can be detected continuously.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical fiber sensor which can be used for detecting the level of a fluid substance such as a liquid, and more particularly to an optical fiber sensor in civil engineering and construction. For example, the present invention relates to an optical fiber sensor suitable for identifying opaque substances such as mud and slime.

[0002]

2. Description of the Related Art Conventionally, there is a method called a red sounding method. To determine in which part of the water there is a solid such as mud or slime, use a stick or a weight to search in the water, and at that time feel the mud, etc. Was checked for the presence of solids.

[0003] Such a conventional method is inefficient,
Moreover, it has been difficult to precisely and accurately detect which portion contains the solid matter.

[0004]

SUMMARY OF THE INVENTION The present invention is an improvement of the transmission measuring method, which solves the above-mentioned conventional problems, and provides an optical fiber sensor capable of accurately and precisely discriminating between water and mud. That is the task.

[0005]

Means for Solving the Problems The inventors of the present invention have made intensive studies to achieve the above object, and as a result, have considered the provision of a slit in a transparent light guide and the movement of a detection unit, and have considered the present invention. It was completed.

In other words, according to the present invention, a detection unit is provided in the longitudinal direction of the optical rod, in which the tip of the input optical fiber connected to the light source and the tip of the output optical fiber connected to the light receiving unit face each other. In addition to being provided movably in the cavity, a slit extending in the longitudinal direction of the optical rod is provided at a position that interrupts the optical path between the distal end of the input optical fiber and the distal end of the output optical fiber. Is an optical fiber sensor.

Further, the present invention is an optical fiber sensor provided with a means for changing an optical path in a longitudinal direction of an optical rod.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below with reference to the drawings. FIG. 1 is a perspective view showing an example of the optical fiber sensor of the present invention, FIG. 2 is a schematic sectional view thereof, and FIG.
FIG. 4 is a detailed view of the detection unit 5 taken along a line A in FIG.
1 to 3, reference numeral 1 denotes an optical rod, 1A denotes a cavity provided in the longitudinal direction of the optical rod 1, 1B denotes a slit provided in the longitudinal direction of the optical rod 1, 2 denotes an optical transmission line, and an input side optical fiber. 3 and an output side optical fiber 4. Reference numeral 5 denotes a detecting unit, 6 denotes a light source, and 7 denotes a light receiving unit. The input optical fiber 3 is connected to the light source 6 and the output optical fiber 4 is connected to the light receiving unit 7, respectively. 9 is an optical path changing means.

[0009] As shown in FIG.
Input optical fiber 3 and output optical fiber 4
The two optical fibers are fixed by the optical fiber end fixing bracket 8 with the tip portions of the two optical fibers facing each other.

[0010] Here, the opposing end portions of the two optical fibers 3 and 4 mean that the light from the end portion of the input side optical fiber 3 is reflected by the optical path changing means 9 and finally the output side optical fiber. This means that the distal ends of the optical fibers 3 and 4 are disposed in such a positional relationship as to enter the distal end of the optical fiber 4.

The distal ends of the optical fibers 3 and 4 are cut in a plane at an angle of 45 ° with respect to the longitudinal direction of the fibers. The cut surfaces 3a and 4a are directed downward, and the light changes its direction by 90 ° at the cut surfaces 3a and 4a, and the light path changes by 90 ° between the optical path changing means 9 and the distal ends of the optical fibers 3 and 4. Become. The ends of the optical fibers 3 and 4 may be polished or mirror-bonded in a plane.

Therefore, the light that has entered the input side optical fiber 3 is directed upward by a 45 ° cut surface 3a at the front end.
After changing the direction at 0 °, the light once out of the optical fiber passes through the slit 1B, and then is inclined at 45 ° on the left side of the optical path changing means 9.
Incident on the cut surface 9a, and is reflected by this surface to change the direction by 90 °.

Next, as shown in FIGS. 3 and 4, the light reflected by the optical path changing means 9 is incident on the right 45 ° cut surface 9b of the optical path changing means 9 at an oblique angle of 45 °. change.

Next, the reflected light again passes through the slit 1B, and then enters the 45 ° cut surface 4a at the tip of the output side optical fiber 4, where the direction is changed again by 90 °. 4 is condensed.

The present invention utilizes the phenomenon that the light transmittance changes when an opaque substance such as mud enters the slit 1B provided in the longitudinal direction of the optical rod 1.

That is, when an opaque substance such as mud enters the slit 1B of the present invention, the transmittance of light at the slit portion decreases, and accordingly, the output side light which is a part of the optical transmission line 2 The amount of transmitted light incident on the fiber 4 decreases.

Therefore, the light source 6 provided at one end of the optical transmission line 2
From the slit 1B depending on whether or not the amount of light received by the light receiving unit 7 provided at the end of the optical transmission path changes.
The presence of an opaque substance such as mud in the vicinity can be detected.

In addition, since the detection unit 5 can move continuously in the longitudinal direction of the optical rod 1, continuous detection can be performed over the entire length of the optical rod 1, and a transparent object such as water and mud or the like can be detected. Detailed detection is possible, for example, opaque substances can be identified.

Here, the dimensions of the optical rod 1 are arbitrary, but the length is 0.1 m to 10 m and the cross section is 10 × 10
A rectangle of mm ² to 30 × 30 mm ² is particularly preferred.

Further, a cavity 1A is provided in the longitudinal direction of the optical rod 1. The size and shape of the hollow portion 1A are also arbitrary, but the cross section is 4 mm × 4 mm to 10 mm.
A rectangle of × 20 mm is particularly preferred.

A slit 1B is provided in the longitudinal direction of the optical rod 1. Regarding the width of the slit 1B,
1 mm to 5 mm is particularly preferred.

As for the depth of the slit 1B, even if the slit 1B is dug deep so as to block both sides of the optical path as shown in FIG. 3, one side of the optical path is blocked as shown in FIG. It may be either shallow or such.

Further, the installation location of the slit 1B can be variously selected, for example, as shown in FIG. 6, provided in the optical path between the two separate optical path changing means 9.

The material of the optical rod 1 is glass or PMM.
A, a transparent resin such as polycarbonate, PVC, PET polyethylene or the like is used.

The optical path changing means 9 disposed in the optical rod 1 can be selected from various types such as a prism or a reflecting mirror (mirror).

Next, the optical transmission line 2 is mainly made of an optical fiber, and is made of a plastic optical material having an outer diameter of 2.2 mm (cladding diameter of 1 mm), a core of PMMA resin, a cladding of fluorinated acrylate resin and a sheath of polyethylene. Fiber or HPCF with outer diameter of 2.2 mm (cladding diameter of 230 μm)
(Hard plastic clad fiber), core is quartz glass outer diameter 200 microns, cladding is fluorinated acrylate resin, outer diameter 230 microns, sheath is fluororesin,
The outer diameter is 500 microns, the reinforcing agent is Kevlar, and the outer covering member is vinyl chloride.

Next, a metal or resin material is used for the optical fiber terminal fixing fitting 8. Regarding the dimensions, any shape according to the shape of the cavity 1A is possible,
3.5mm x 3.5mm x 10mm-9mm x 19mm
× 20 mm is particularly preferred. The light source 6 is a halogen lamp,
A light emitting diode, a semiconductor laser, or the like is used. Light receiving section 7
Uses a silicon photodiode or a silicon phototransistor.

Next, still another embodiment of FIG. 7 will be described. In this case, as shown in FIG. 7, the detection unit 5 is configured by aligning two optical fibers of the input side optical fiber 3 and the output side optical fiber 4 which constitute the optical transmission line 2.

Next, another embodiment of FIG. 8 will be described.
In this case, the input side optical fiber 3 and the output side optical fiber 4 are installed at positions facing each other with a slit interposed therebetween, and the light emitted from the distal end cut surface 3a of the input side optical fiber 3 is transmitted through the slit 1B. After that, the light directly enters the distal end cut surface 4a of the output side optical fiber 4.

For this reason, in this embodiment, the optical path changing means 9 such as a prism or a reflecting mirror becomes unnecessary. However, as compared with the other embodiments, the shape of the hollow portion 1A and the detection portion 5
Becomes a U-shape, and the shape becomes slightly complicated.

Finally, another embodiment shown in FIGS. 9 and 10 will be described. In this case, the input / output optical fiber 3 and the output-side optical fiber 4 are combined to form one input / output optical transmission line 2.

Since it is not necessary to use a prism as the light path changing means 9, a simple thin reflecting mirror (mirror) is sufficient.
Most compact design is possible.

However, in this case, since the light generated from the light source 6 is input to the optical transmission line 2 or the reception light output to the optical transmission line 2 is made to enter the light receiving section 7, FIG. Such a light branching means 10 may be used, or another method not using the light branching means 10 may be selected. A half mirror is cited as an example of the light splitting means.

FIG. 11 shows an example in which the optical fiber sensor of the present invention is used. The optical rod uses a transparent PMMA resin.
The dimensions were a rectangle with a cross section of 8 mm x 14 mm, and the total length was 1 m.

The dimensions of the cavity in the optical rod are 4.8 in cross section.
It was a rectangle of mm × 2.7 mm. Further, here, the slit width was 2 mm. Further, a prism was used as an optical path changing means. The size of the optical fiber terminal fixing bracket is 4.
5 mm × 2.5 mm, length 15 mm and made of brass were used.

The optical transmission line (input / output optical fiber) is made of a PMMA resin core, a fluororesin clad, a polyethylene sheath, and has a core diameter of 1 mm and an outer diameter of 2.2.
mm was used. The light source used was a light emitting diode with a wavelength of 660 mm, and the light receiving element was a silicon photodiode.

Further, the optical fiber winding bobbin preferably has an outer diameter of about 20 cm to 50 cm.
A resin product having a thickness of 0 cm and a thickness of 10 cm was used. The bobbin may be driven manually or electrically, but when the optical fiber sensor is long, it is preferable to drive the bobbin electrically.

The control wire is a wire connecting the control device to a light source, a light receiving portion or a bobbin driving portion. The control device includes a control circuit, a display circuit, a display unit, and the like. With this control device, the number of rotations of winding the optical fiber is counted, the reflected light (received light) power is displayed on the display unit, and the exact position (level) of solids such as underwater mud can be detected in detail by monitoring and monitoring. is there.

[0039]

According to the optical fiber sensor of the present invention, the position of mud deposited in water can be easily detected.

[Brief description of the drawings]

FIG. 1 is a perspective view showing an example of an optical fiber sensor of the present invention.

FIG. 2 is a schematic sectional view of the optical fiber sensor of the present invention.

FIG. 3 is a sectional view taken along line AA of FIG. 2;

FIG. 4 is a detailed diagram of a detection unit 5;

FIG. 5 is a schematic sectional view showing an embodiment in which a slit is provided on only one side of the optical path.

FIG. 6 is a schematic sectional view showing an embodiment in which a slit is provided between two prisms.

FIG. 7 is a schematic sectional view showing an embodiment in which an input side optical fiber and an output side optical fiber are aligned.

FIG. 8 is a schematic sectional view showing an embodiment having no optical path changing means.

FIG. 9 is a schematic sectional view showing still another embodiment using one optical fiber.

FIG. 10 is a schematic sectional view showing an embodiment using a light branching means.

FIG. 11 is a schematic diagram for explaining a use state of the optical fiber sensor of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Optical rod 1A cavity 1B slit 2 Optical transmission path 5 Detecting part 6 Light source 7 Light receiving part 9 Optical path changing means 10 Optical branching means

Claims (7)

[Claims] 1. A detecting section, in which a distal end of an input optical fiber connected to a light source and a distal end of an output optical fiber connected to a light receiving section face each other, are moved into a cavity provided in a longitudinal direction of the optical rod. And a slit extending in the longitudinal direction of the optical rod is provided at a position where an optical path between the distal end of the input side optical fiber and the distal end of the output side optical fiber is interrupted. Fiber optic sensor. 2. An optical fiber sensor according to claim 1, further comprising means for changing said optical path in a longitudinal direction of said optical rod. 3. The optical fiber sensor according to claim 2, wherein said optical path changing means is a light reflecting means. 4. The optical fiber sensor according to claim 2, wherein said optical path changing means is a prism. 5. A detection unit comprising an input side optical fiber connected to a light source and an output side optical fiber connected to a light receiving unit are movably provided in a cavity provided in a longitudinal direction of the optical rod. An optical fiber sensor comprising light reflecting means provided through a slit provided in a longitudinal direction of the rod. 6. A detecting section comprising one optical fiber connected to a light source and a light receiving section is movably provided in a cavity provided in a longitudinal direction of the optical rod, and a slit provided in a longitudinal direction of the optical rod is provided. An optical fiber sensor provided with a light reflecting means through the optical fiber sensor. 7. A light branching means connected to a light source and a light receiving unit,
A detecting section comprising one optical fiber connected to the light branching means is movably provided in a cavity provided in the longitudinal direction of the optical rod, and the light reflecting means is provided through a slit provided in the longitudinal direction of the optical rod. An optical fiber sensor comprising: