JPS58171609A - Fiber optic sensor - Google Patents

Abstract

PURPOSE:To provide the resistance to electromagnetic force without an electric power source by operating a light emitting element at a receiving end, sending the light thereof through an optical fiber to a sensor part and transmitting the sensed measurement information to the receiving end through another optical fiber. CONSTITUTION:Light is fed from a light source 5 through an optical fiber 31 to a sensing part and when there is no mirror or the mirror surface does not face the sensor part, the reflected light thereof does not enter a condenser lens 21 and does not return to a receiver 4. However, when the mirror surface faces the sensor part and when the mirror comes to the position where the light enters the lens 21, the light which is sent by the fiber 31 and is reflected by the mirror is transmitted through a fiber 32 and is detected with the receiver 4.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a powerless sensor using an optical fiber. Currently, many types of measurement sensors are being developed and used, but the most important requirements are: 1) no power supply, 2) high resistance to electromagnetic environments, There are two. /) means that no batteries are required, and is a necessary condition to ensure stability, longevity, and reliability. 2) means noise resistance, which is essential to ensure high reliability of sensed data. However, there are very few conventional sensors that meet both of these conditions. For example, thermistors and thermocouples are used as temperature sensors, but thermistors require a power source, and thermocouples do not require a power source, but sufficient attention must be paid to noise.
The present invention does not have a power source other than the firM information receiving end,
A light emitting element is operated at the receiving end, and the light is sent to a part of the sensor through an optical fiber, and the sensed "[
The feature of the measurement is that it fully satisfies the conditions of /) and 2) mentioned above.

Therefore, the sensor according to the present invention can be used under severe electromagnetic environment conditions without being affected by them at all, and
Since there is no power supply inside the sensor, long life and high reliability are guaranteed.

Now, the details of the present invention will be explained with reference to the drawings. FIG. 4 is a diagram illustrating the principle of the present invention in a general configuration.

Reference numeral 1 denotes a box surrounding the sensing section, and this section is referred to as a part of the sensor. 2 generally shows a sensing section. Reference numeral 31 denotes a bundle of optical fibers for introducing the light from the light source 5 into the sensing section 2. The light passing through the sensing section passes through the optical fiber bundle 3 and is guided to the power receiver 4. 4, the most appropriate detection method is used depending on the object to be sensed or the amount to be measured, such as detecting the intensity of light, detecting a light pattern, or detecting the position of a light spot. Some embodiments of this principle will be described below.

2111th! ff is a diagram showing an embodiment in which the present invention is applied to a sensor for detecting the position of a mirror. 6 is a mirror, which is movable. Now, light cannot be sent from the light source of 5 to the sensing part through the optical fiber of 3, but if there is no mirror or the mirror surface is not facing the sensor part, the reflected light will not enter the light building lens of 2 and therefore 3. The light does not return to receiver 4 with optical fiber 2-. However, when the mirror comes to a position where the mirror surface faces the sensor part and the light enters the light lens 2, the reflected light from the mirror sent in 3 passes through the optical fiber 32. The signal is transmitted and detected by the receiver 4. This sensor functions as a limit switch when sensing the linear position of the mirror, and functions as a tachometer when sensing the rotation of the mirror. This is a simple embodiment of the present invention.

FIG. 3 is a diagram showing an embodiment in which the present invention is applied to vibration detection. 7 is a part of a vibrating body, and one end of an optical fiber sensor part 3 □ is fixed to a plate or rod 2 . When the vibrating body 7 vibrates, light transmitted from the light source 5 through the optical fiber 3 is intermittently detected by the receiver 4 through the optical fiber 3°.

That is, the optical fibers 3□ and 3° of the sensing part in the sensor part 1 have time to temporarily face each other due to the movement of 3□, and at this moment light is detected by the receiver 4 through 3. This type of sensor detects the presence or period of vibration across the 81
This is an embodiment of the present invention. Note 3
If the optical fiber is a one-dimensional or two-dimensional optical fiber bundle made by bundling a large number of optical fibers, the receiver 4 can detect the shape of the vibration as a change in the position of the light spot. The sensor can also sense the waveform of

Figure 5 is a diagram showing an embodiment of the present invention when it is implemented as a sensor for detecting rotational speed. In FIG. 1, only the inside of the sensing section 2 of FIG. 1 is shown, and the rest is omitted. 8 is a part of the rotating shaft.
In order to detect the rotation of the shaft, a protrusion 23 is provided on a part of the shaft. An optical fiber 31 is fixed to a leaf spring 24. 24 has a fixed upper end, but that part is omitted. As the shaft 8 rotates, the protrusion 23 comes into contact with the leaf spring 24, and moves the optical fiber 3 inside the sensing section. This movement allows the optical fibers 31 and 3 degrees inside the sensing section (inside of FIG. 1) to instantaneously face each other. Therefore shaft 8
If it rotates, light will be sent to the receiving end only when 3□ and 32 face each other, rotation can be detected, and the rotation speed can be detected by measuring the pulses of light.
This is also a simple embodiment of the invention.

FIG. S is a diagram showing an embodiment in which the present invention is applied to a position sensor. In the figure, 25 is a part of the sensor that is displaced depending on measurement information. In this example,
The spot of light sent by the optical fiber sensor 3□, which is displaced according to the ti measurement information, has its position as 25
It changes by displacing a part of the sensor that is displaced depending on the measurement information. The position of this spot is detected at the receiving end by three optical fiber arrays.
3r is a front view of the optical fiber array at the receiving end, and 3; shows in black and white the fibers detecting the light spot in the optical fiber array. The position of 31 frames in the optical fiber array corresponds to 1frBE information, and FIG. 5 shows an embodiment of the present invention that functions as a position sensor.

Figure 6 shows an example in which the displacement sensor shown in Figure S is applied to a bimetallic temperature sensor (Figure 6 (a)) and an example in which it is applied to a pressure sensor (Figure 6 (b)).
) are shown respectively.

First, let us explain FIG. 3(a).

This is indicated by the arrow in the figure. The displacement due to the bending of the bimetal is the position of the spot of light sent by 3°.
It becomes the rank. This is detected by 32 optical fiber arrays, and the principle is exactly the same as that described in detail with respect to FIG. In addition, in Fig. 3(a), the first
Only the portion corresponding to the second sensing section of the IU is shown.

Next, FIG. 6(b) shows a case where the present invention is applied to a pressure sensor that is displaced by pressure. 26 indicates a structure that can be expanded and contracted by pressure. Displacement due to pressure is indicated by an arrow in the figure.

The source fiber 3 is fixed to the variable part of the pressure sensor, and the spot of light sent at 31 is displaced by the pressure. Only the portion corresponding to the sensing portion 2 in FIG. 7 is shown for this displacement. 'In addition to detecting the position of the light spot on the receiver side in Figure 5, it is natural to use a method using an optical sensor array, in addition to the moon phase. The optical sensor array and its associated circuitry will be introduced, but this can be handled in a variety of ways depending on the implementation issues and requirements of the present invention.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing the principle of the present invention in a general configuration, and FIG. 2 is a diagram showing an embodiment in which the present invention is applied to a sensor for detecting the position of a mirror. FIG. 3 is a diagram showing an embodiment in which the present invention is applied to vibration detection, and FIG. 4 is a diagram showing an embodiment in which the present invention is implemented as a sensor for detecting rotational speed. Figure S is a diagram showing an embodiment of the present invention applied to the first position sensor;
5 is a diagram showing an embodiment in which the principle of FIG. 5 is applied to a B-imetal temperature sensor, and FIG. 3(b) is a diagram showing an embodiment in which the principle of FIG. 5 is similarly applied to a pressure sensor.

Claims (1)

[Claims] 1) One or some of the optical fibers in an optical fiber bundle consisting of two or more optical fibers are used for transmitting light, and the light is transmitted from one end of the fiber to the other end. Transmit this light to 7! By using the tt measurement information as a sensing light and sensing the measurement information, the other seven or more optical fibers in the optical fiber bundle ρ are used as the return path of the light, and the light is sent to the light sending side. A fiber optic sensor is characterized by detecting the presence, shape, or value of measurement information from the intensity of the returned light or the position or shape of the light spot. 2) Send light from one end of seven or some of the optical fibers in an optical fiber bundle consisting of two or more optical fibers, and reflect the light from the mirror at the other end of the optical fiber bundle. is returned to the light sending side using the other/a fiber bundle or multiple fiber bundles as a return path, and the existence or rotation of the movable mirror can be obtained as measurement information depending on the presence or absence of the light. A fiber optic sensor according to claim 1. 3) One end of seven or some of the optical fibers in an optical fiber bundle consisting of two or more optical fibers is used as a light transmission end, and the other end is used as a part of a vibrating body or a rotating body. The fibers are made movable by being connected or brought into contact with each other, and light is transmitted through the optical fiber from the light transmission end, and the movement of the light spot due to the displacement of the other end of the fiber is detected by the other seven or more of the optical fibers. The fiber optic sensor according to any one of claims 1 to 2), wherein the fiber optic sensor detects vibration or rotation of an object at the other end of the light transmission end. 4ZlII One end of seven or some of the optical fibers in an optical fiber bundle consisting of several optical fibers is used as the light sending end, and the other end is attached to the displacement part of a displacement converter that is displaced according to measurement information, and the displacement is determined according to the measurement information. The displacement of the light spot is detected at the light output end through the unused portion of the optical fiber bundle, and the measurement information at the other end is obtained from the movement of the light spot at the light output end. Claims 1 to 3)
A fiber optic sensor described in one of the above. 5) One end of seven or some of the optical fibers in the optical fiber bundle consisting of multiple optical fibers is used as the light sending end, and the other end is attached to the movable part of the bimetal, and the displacement of the bimetal due to temperature change is detected as a light spot. , the light spot is detected at the light output end through the unused part of the optical fiber east, and the temperature change is read as a change in the position of the light spot at the light output end. A fiber optic sensor according to claim 1 or claim 4). J) A movable part of a force transducer or pressure transducer in which one end of seven or some of the optical fibers in an optical fiber bundle consisting of several optical fibers is used as the light transmission end, and the other end is displaced by force or pressure. The displacement of the moving part due to a change in force or pressure is converted into a movement of a spot of light, and the spot of light is detected at the light delivery end through an unused portion of the fiber optic bundle to detect the force or pressure. The fiber optic sensor according to claim 1, wherein a change in pressure is read as a change in the position of a light spot at a light sending end.