JP2006293019A - Optical fiber sensor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an optical fiber sensor which suppresses decrease in detection accuracy due to misalignment between an optical fiber and a light emitting means and/or a light receiving means. <P>SOLUTION: The optical fiber sensor 1 comprises an optical fiber, a light emitting means, and a light receiving means, wherein one end position of the optical fiber with respect to the light emitting unit and/or the other end position of the optical fiber with respect to the light receiving unit are fixed. The position of each end of the optical fiber with respect to the light emitting unit and/or the light receiving part is fixed, and as the result of suppression of changes in light due to misalignment (relative phase changes) of the optical fiber in a connecting part, the optical fiber sensor can perform measurement with high accuracy. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an optical fiber sensor, and more particularly to an optical fiber sensor used in a collision detection sensor that is installed on the outer periphery of a vehicle and detects a collision with the vehicle.

  In recent years, in vehicles, safety in the event of an accident has been improved. With respect to vehicle safety, not only is it necessary to ensure the safety of passengers in the event of an accident, but there is a need for improved safety for pedestrians who have collided with the vehicle.

  As a means of protection against pedestrians when a vehicle collides with a pedestrian, when the pedestrian collides with the vehicle, the damage when the pedestrian collides with the front part such as the hood of the vehicle is reduced as much as possible. A method of reducing the injury value (impact received by a pedestrian) is considered.

  In such a pedestrian safety device, it is important to determine a pedestrian collision. And as one method of detecting a pedestrian collision, there is a method of attaching an optical fiber sensor as a collision detection sensor to a bumper part of a vehicle.

  An optical fiber sensor is a sensor that performs sensing from a change in light transmitted through an optical fiber. Specifically, when a stress is applied to the optical fiber from the outside, the optical fiber is distorted, and the characteristic of transmitting light at the strained portion changes. And if the translucency of the optical fiber which has light permeate | transmitted inside changes, the intensity | strength and phase of the light which permeate | transmitted the optical fiber will change. The optical fiber sensor performs sensing using the phenomenon that the transmitted light changes. That is, the optical fiber sensor includes an optical fiber, a light emitting unit that emits light that passes through the optical fiber, and a light receiving unit that receives light transmitted through the optical fiber. In addition, there is an arithmetic means for calculating the stress applied to the optical fiber from the input light of the light emitting means and the output light of the light receiving means.

  A general optical fiber sensor is configured by, for example, modularizing an optical fiber, a light emitting unit, a light receiving unit, and an arithmetic unit, and connecting the modules. Each module is connected using a connector provided at a connection portion of the module.

  The connection by the connector has a problem that the connectors cannot be fixed completely. Specifically, the connector has a gap called play for attachment and detachment. When the connection was made by the connector, the position of the end face of the optical fiber and each means was shifted within the gap.

  Conventional optical communication using an optical fiber only transmits an on / off signal using light, and no problem occurs because it is possible to determine on / off even if the connector is displaced. However, the optical fiber sensor needs to measure the intensity and phase of light, and if the connection portion is displaced, the measurement accuracy decreases. In particular, when mounted on a vehicle, displacement of the connecting portion is likely to occur due to vibration of the vehicle during traveling.

  More specifically, when the end of the optical fiber is displaced, the position of the end face of the optical fiber is also shifted. Usually, the end of the optical fiber is disposed at a position where the central axis of the optical fiber faces the light emitting part of the light emitting means. The position where the end face of the optical fiber is arranged is the position where the light emitted from the light emitting means is best hit. For this reason, when the end of the optical fiber is displaced due to a shift in the connection portion, the light emitted from the light emitting means is not sufficiently applied. Further, when the end portion of the optical fiber is shifted, the end surface of the end portion of the optical fiber is inclined with respect to the light emitting portion of the light emitting means. That is, light is reflected at this end face. As a result, a sufficient amount of light for sensing is not supplied to the inside of the optical fiber, and the sensing accuracy decreases.

  The present invention has been made in view of the above circumstances, and an object of the present invention is to provide an optical fiber sensor in which a decrease in detection accuracy due to deviation between the optical fiber and the light emitting means and / or the light receiving means is suppressed.

  In order to solve the above problems, the present inventors have studied optical fiber sensors, and as a result, have found that the above problems can be solved by using an optical fiber sensor in which the position of the optical fiber relative to the light emitting means and the light receiving means is fixed. .

  In other words, the optical fiber sensor of the present invention receives the light emitted from the optical fiber, the light emitting means for emitting the light irradiated to one end of the optical fiber, and the other end of the optical fiber. And a light receiving means having a light receiving portion, wherein the position of one end of the optical fiber relative to the light emitting portion and / or the position of the other end of the optical fiber relative to the light receiving portion is fixed. To do.

  In the optical fiber sensor of the present invention, the position of each end of the optical fiber with respect to the light emitting part and / or the light receiving part is fixed. In other words, the optical fiber shift (relative phase change) at the connecting portion is suppressed. As a result, a measurement error due to a change in light at the connection portion does not occur. That is, the optical fiber sensor of the present invention can perform measurement with high accuracy.

  The optical fiber sensor of the present invention includes an optical fiber, a light emitting means, and a light receiving means.

  The optical fiber sensor emits light emitted from one end of the optical fiber while the light emitting means emits light. The light applied to one end of the optical fiber travels through the optical fiber and is emitted from the other end. The optical fiber sensor calculates a stress applied to the optical fiber from a change in light transmitted through the optical fiber. More specifically, the optical fiber sensor transmits light through the optical fiber. When stress is applied to the optical fiber, distortion occurs in the optical fiber itself. When the optical fiber is distorted, the light transmittance of the optical fiber changes. Furthermore, when the optical fiber is bent, the direction of the interface between the core and the clad where the transmitted light is reflected changes. When this change in light transmission occurs, the path of the transmitted light in the optical fiber changes, and the intensity of the light decreases in some cases. The stress applied to the optical fiber is detected from the change in intensity and phase of light irradiated from the other end.

  The optical fiber of the optical fiber sensor may be made of resin or glass as long as it is an optical fiber having a core and a clad formed of materials having different refractive indexes. Further, the difference in refractive index between the core and the clad is not particularly limited. Furthermore, the thickness and length of the optical fiber are not particularly limited. As the optical fiber, an optical fiber used in a conventional optical fiber sensor can be used.

  The light emitting means has a light emitting part that emits light irradiated to one end of the optical fiber. The light emitting means is connected to one end of the optical fiber. A light emission part shows the site | part which actually emits light. The light emitting means is disposed at a position where the light emitting unit can irradiate light to one end of the optical fiber. The light emitting means is preferably arranged so that the center of the light emitting portion is coaxial with the central axis of the optical fiber.

  The light emitted from the light emitting part of the light emitting means is applied to one end of the optical fiber. Here, the light emitting means is preferably arranged in a state where the surface of the light emitting portion is perpendicular to the end face of the optical fiber. The light emitted from the light emitting part is not limited as long as the light can be transmitted from one end of the optical fiber to the other end and irradiated from the other end. The light emitted from the light emitting means is preferably light having a single wavelength. The light emitting part is preferably a light emitting part of a light emitting diode (LED).

  The light receiving means is connected to the other end of the optical fiber. And it has the light-receiving part which light-receives the light emitted from the other edge part of an optical fiber. The light receiving unit indicates a part that actually receives light. The light receiving means is disposed at a position where the light receiving unit can receive light from the other end of the optical fiber. In the light receiving means, the light receiving portion is preferably arranged coaxially with the central axis of the optical fiber.

  The light receiving portion of the light receiving means receives the light transmitted through the optical fiber and generates a light reception signal. The force applied to the optical fiber is determined from the received light signal. The light receiving means is preferably arranged in a state where the surface of the light receiving portion is perpendicular to the end face of the optical fiber. The light receiving unit is not limited as long as it is a member that can receive irradiation light from the other end of the optical fiber and detect the change thereof. The light receiving portion of the light receiving means is preferably a light receiving portion of a photodiode (PD).

  The light receiving means and the light emitting means of the present invention may be either separate or integrated.

  In the optical fiber sensor of the present invention, the position of one end portion of the optical fiber with respect to the light emitting portion and / or the position of the other end portion of the optical fiber with respect to the light receiving portion is fixed. Since the position of the end portion of the optical fiber with respect to the light emitting portion and the light receiving portion is fixed, the loss of light at the connection portion of the optical fiber does not occur. In other words, since the position of the end of the optical fiber with respect to the light emitting part or the light receiving part is fixed, even if vibration is applied to the connection part of the optical fiber, there is no deviation between the two parts, so no change in light occurs. . That is, even in a state where vibration is applied to the connecting portion, light emitted from one of the light emitting portion or the light receiving portion and the end of the optical fiber strikes the other without changing. A decrease in measurement accuracy due to a change in light at the connection portion of the optical fiber does not occur.

  In the optical fiber sensor of the present invention, either one of the position of one end of the optical fiber relative to the light emitting portion and the position of the other end of the optical fiber relative to the light receiving portion may be fixed, but both are fixed. It is preferred that That is, in the optical fiber sensor of the present invention, it is preferable that the position of one end of the optical fiber with respect to the light emitting portion and the position of the other end of the optical fiber with respect to the light receiving portion are fixed.

  The method for fixing the position of one end of the optical fiber with respect to the light emitting part and the position of the other end of the optical fiber with respect to the light receiving part are not particularly limited. In other words, any method that does not hinder light reception / emission between the end of the optical fiber and the light emission / reception means may be used. Also, the method of fixing the position of one end of the optical fiber with respect to the light emitting part and the method of fixing the position of the other end of the optical fiber with respect to the light receiving part may be the same method or different methods. But you can.

  Each end of the optical fiber, the light emitting means and the light receiving means are preferably housed and fixed in a substantially box-shaped case. By accommodating and fixing each end of the optical fiber, the light emitting means, and the light receiving means in the case, the optical fiber, the light emitting means, and the light receiving means can be easily fixed. Specifically, each of the optical fiber and the light receiving / emitting means can be fixed by fixing them to the case. Furthermore, it is possible to easily assemble the optical fiber and the light receiving / emitting means. Moreover, by connecting and fixing in the case, the connection portion is covered, and the weather resistance of the connection portion is increased. The method for fixing the optical fiber to the case is not particularly limited.

  It is preferable that one end of the optical fiber and the light emitting means and / or the other end of the optical fiber and the light receiving means are resin-molded. By fixing with a resin mold, one end portion of the optical fiber and the light emitting means and / or the other end portion of the optical fiber and the light receiving means can be more firmly fixed, and a slight deviation in the connection portion does not occur. . In the resin mold in which one end of the optical fiber and the light emitting means and / or the other end of the optical fiber and the light receiving means are fixed, it is preferable that the case is also molded.

  Moreover, it is preferable that the vicinity of each edge part of the optical fiber is bonded to the case. The vicinity of the end of the optical fiber refers to the end of the optical fiber that does not contribute to sensing when the optical fiber sensor is formed. More preferably, the vicinity of the contact portion with the case is shown.

  The optical fiber sensor of the present invention preferably has a calculation unit that is connected to the light emitting unit and the light receiving unit and calculates the stress applied to the optical fiber from the light before and after the optical fiber. By having the computing means, the strain applied to the optical fiber and the stress applied to the optical fiber can be calculated from the signals from the light emitting means and the light receiving means.

  The optical fiber sensor of the present invention is preferably used as a collision detection sensor that is disposed on the outer periphery of the vehicle and detects a collision with the vehicle. The outer periphery of the vehicle is a position where an impact can be detected when an object collides with the vehicle. The optical fiber sensor of the present invention is preferably installed in a vehicle bumper. The optical fiber sensor is not affected by electromagnetic waves because it senses with light transmitted through the optical fiber. For this reason, since the optical fiber sensor does not require an electromagnetic wave countermeasure, it is preferably used for a vehicle sensor that requires an EMC (electromagnetic compatibility) countermeasure. Moreover, since the optical fiber sensor of this invention can lengthen the length of a sensor (optical fiber) because the loss of light was suppressed, among the sensors for vehicles, the sensor for collision detection which senses with a vehicle bumper It is more preferable to use as.

  Hereinafter, the present invention will be described using examples.

  As an example of the present invention, an optical fiber sensor was manufactured.

(Example)
The optical fiber sensor 1 according to the present embodiment includes an optical fiber 2, a light emitting / receiving unit 3, a case 4, and a resin mold 5. The optical fiber sensor of this example is shown in FIGS. FIG. 1 is a cross-sectional view of the optical fiber sensor, and FIG. 2 is a cross-sectional view taken along line II in FIG.

  The optical fiber 2 is a linear plastic optical fiber.

  The light receiving / emitting means 3 includes an LED 30 to which one end 20 of the optical fiber 2 assembled on the substrate 33 is connected and a PD 31 to which the other end 21 of the optical fiber 2 assembled on the substrate 33 is connected. And an ECU 32 provided in a state of being connected to the LED 30 and the PD 31 on the substrate 33.

  The LED 30 irradiates light to the end face of one end 20 of the optical fiber 2. The PD 31 receives light emitted from the other end 21 of the optical fiber 2. As for LED30 and PD31, the light emission part and the light-receiving part have faced the direction where the board | substrate 33 spreads. That is, it receives and emits light in a direction spreading on the substrate 33. The light emitting part and the light receiving part of the LED 30 and the PD 31 are provided with cylindrical members 300 and 310 into which the ends of the optical fiber 2 are inserted. The cylindrical members 300 and 310 are connected to the ends 20 of the optical fiber 2. , 21 are inserted and fixed to connect the light emitting / receiving means 3 and the optical fiber 2. The end portions 20 and 21 of the optical fiber 2 inserted into the cylindrical members 300 and 310 were fixed at positions spaced apart from the surfaces of the LEDs 30 and PD31. This is because when the end portions 20 and 21 of the optical fiber 2 come into contact with the LED 30 and the PD 31, the LED 30 and the PD 31 are damaged due to stress at the time of contact.

  The ECU 32 is connected to the LED 30 and the PD 31. ECU32 controls the light which LED30 emits. Specifically, by controlling the current flowing through the LED 30, the intensity of light emitted from the LED 30 and the light emission time are controlled. Also, an output signal from the PD 31 is received, and the intensity and light emission time of the light received by the PD 31 are obtained. Then, the ECU 32 calculates the stress applied to the optical fiber 2 from the light emitted from the LED 30 and the light received by the PD 31. The actual ECU 32 calculates the stress on the optical fiber 2 from a comparison between the current flowing through the LED 30 and the current generated by the PD 31.

  The case 4 is formed in a substantially box shape in which both end portions 20 and 21 of the optical fiber 2 and the light emitting / receiving means 3 are accommodated. The case 4 includes an upper case 40 and a lower case 41. The lower case 41 has a fixing means (not shown) for fixing the light emitting / receiving means 3. A through-hole through which the optical fiber 2 passes is opened on the wall surface of the case 4 facing the LED 30 and the PD 31. The through hole opens at a connection portion between the upper case 40 and the lower case 41.

  The resin mold 5 molds the optical fiber 2, the light receiving / emitting means 3, and the case 4 in a state where the optical fiber 2 is connected to the light receiving / emitting means 3 and is assembled to the case 4. Specifically, a resin mold is formed on the outer peripheral portion of each connection portion with one end 20 of the optical fiber 2 inserted into the cylindrical member 300 and the other end 21 inserted into the cylindrical member 310. 5 and 5 are formed. Further, the resin molds 5 and 5 are formed up to a portion where the optical fiber 2 penetrates the case 4. The optical fiber 2 is completely fixed to the light receiving and emitting means 3 by the resin molds 5 and 5. Further, the resin mold 5 is fixed to the case 4. Thereby, not only the connection part of the optical fiber 2 and the light emitting / receiving means 3 was fixed, but this connection part was fixed to the case 4.

(Collision detection sensor)
This embodiment will be described in more detail using an example in which an optical fiber sensor is used as a collision detection sensor. The collision detection sensor is a sensor that is assembled to the vehicle bumper and detects a collision with the vehicle bumper. The optical fiber sensor assembled to the vehicle bumper is shown in FIGS.

  The vehicle bumper 6 is provided in front of the engine room. In the vehicle bumper 6, a bumper force 60 is fixed to a front side member Vm provided in the vehicle, an optical fiber 2 is extended on the front surface of the bumper force 60, and a substantially plate-shaped load plate is formed on the front surface of the optical fiber 2. 61 is provided, and an absorber 62 made of an elastic member such as foamed resin for relaxing the impact is provided on the front surface thereof, and a bumper cover 63 is further provided. The case 4 accommodating the light emitting / receiving means 3 was disposed in the vicinity of one end portion (end portion on the passenger seat side) of the bumper force 60.

  In this embodiment, the ECU 32 also serves as a calculation means of a collision safety system that protects a pedestrian when a pedestrian collides with the vehicle bumper 6. The ECU 32 can activate the collision safety system when it is determined that the object colliding with the vehicle bumper 6 is a pedestrian. An apparatus for protecting a pedestrian with the collision safety system is not particularly limited.

  Below, operation | movement of the optical fiber sensor 1 is demonstrated.

  In the optical fiber sensor 1, a current flows through the LED 30 according to an instruction from the ECU 32, and the LED 30 emits light. The light emitted from the LED 30 hits the end face of one end 20 of the optical fiber 2 and passes through the inside of the optical fiber 2. And the light which permeate | transmitted the optical fiber 2 is irradiated to PD31 from the other edge part 21 of the optical fiber 2. FIG. The PD 31 receives the light transmitted through the optical fiber 2 and issues a light reception signal to the ECU 32.

  ECU32 compares the instruction | indication to LED30 and a light reception signal, and determines whether the collision object to the bumper 6 of a vehicle is a human body. When it is determined that the collision object is a human body, a signal is sent to the collision safety system to activate the collision safety system.

  The optical fiber sensor 1 is a sensor that detects a collision with the vehicle bumper 6 and performs sensing during operation of the vehicle. Various vibrations are generated in the traveling vehicle. In the optical fiber sensor 1 of the present embodiment, the connection portion between the optical fiber 2, the LED 30, and the PD 31 is fixed by the resin mold 5. That is, the positions of the end portions 20 and 21 of the optical fiber 2 with respect to the LED 30 and the PD 31 are fixed. Due to this fixing, the position of the end portions 20 and 21 of the optical fiber 2 at the connecting portion is not displaced. As a result, the loss of light that occurs when the end portions 20 and 21 of the optical fiber 2 are displaced does not occur. That is, since the decrease in measurement efficiency due to the loss of light at the connection portion is suppressed, the optical fiber sensor 1 according to the embodiment exhibits an effect capable of performing measurement with high accuracy.

It is the figure which showed the structure of the optical fiber sensor of an Example. It is the figure which showed the structure of the optical fiber sensor of an Example. It is the figure which showed the structure when the optical fiber sensor of an Example is assembled | attached to the vehicle bumper. It is the figure which showed the structure when the optical fiber sensor of an Example is assembled | attached to the vehicle bumper.

Explanation of symbols

1: Optical fiber sensor 2: Optical fiber 20: One end 21: The other end 3: Light emitting / receiving means 30: LED
31: PD 32: ECU
33: Substrate 300, 310: Tubular member 4: Case 40: Upper case 41: Lower case 5: Resin mold 6: Vehicle bumper 60: Bumper reinforcement 61: Load plate 62: Absorber 63: Bumper cover

Claims (3)

Optical fiber,
A light emitting means having a light emitting section for emitting light irradiated to one end of the optical fiber;
A light receiving means having a light receiving portion for receiving light emitted from the other end of the optical fiber;
In an optical fiber sensor having
An optical fiber sensor, wherein a position of the one end of the optical fiber with respect to the light emitting part and / or a position of the other end of the optical fiber with respect to the light receiving part is fixed.   The optical fiber sensor according to claim 1, wherein each end of the optical fiber, the light emitting means, and the light receiving means are accommodated and fixed in a substantially box-shaped case. 2. The optical fiber sensor according to claim 1, wherein the one end of the optical fiber and the light emitting means and / or the other end of the optical fiber and the light receiving means are resin-molded.

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