DE102006034841A1 - Sliver for a fiber optic sensor - Google Patents

Abstract

A sliver for a fiber-optic sensor comprises a first and at least one second optical fiber (10, 11), each with a fiber cladding (13) which is interrupted in a light exit region (15) or structured by elevations and / or depressions. In addition, the sliver comprises a cladding material (20) which surrounds the first and the at least one second optical fiber (10, 11) at least in the light exit region (15) and is configured such that light of a fiber wavelength for which the optical fibers (10, 11) are designed, absorbed. This makes it possible to prevent light of the fiber wavelength from being coupled into the optical fibers (10, 11) from the outside.

Description

The Invention relates to a sliver for a fiber optic sensor, in particular a bending sensor, and a use of the sliver.

investigations have shown that a high proportion of road deaths Pedestrian concerns. For this reason, legislative initiatives are under way to The aim is that devices to protect pedestrians in the event of a collision provided with a vehicle mandatory in modern motor vehicles are.

One especially high risk of injury to a pedestrian in case of Collision with a vehicle a very small distance between one typically easily deformable bonnet and a rigid Engine block dar. The arrangement of more and more electronic components in the engine compartment and very compact vehicles As a result, the engine compartment is densely packed with very rigid Bodies. In case of a collision with a pedestrian there is thus the high Danger of severe head injuries, if this with his head bounces on the hood and thus comes in contact with the components located under the bonnet.

One big enough Distance between the bonnet and the engine components below from, for example, over 10 cm, however, can greatly reduce the risk of injury as the Engine hood take enough energy through the deformation can and the pedestrian so comparatively can slow down gently.

Around the security for Pedestrians in the road traffic to increase, For example, the Association of European Automobile Manufacturers (ACEA) across from the authorities The European Union committed by action in the vehicle sector the number of traffic fatalities in the area of pedestrians up halve to the year 2010. One measure for this is the Construction of vehicles with correspondingly spaced engine hoods. by virtue of However, this is often not the case for the required compactness of vehicles possible.

To the Ensure sufficient damping in the event of a collision with a pedestrian in the case of a detected impact of a person to raise the bonnet on the vehicle by more than 10 cm from its closed position, so as to create a sufficient deformation range. A big challenge for such Security systems is the need for them to be reliable, but also very inexpensive are.

As an actuator for lifting the hood is for example from an article in the journal "Automotive Engineer", April 2004, page 48 ff., known to provide a spring-based actuator whose spring is biased and is released in the event of a detected collision, with the result that the hood is raised accordingly. In addition, however, pyrotechnic actuators are also known from the above-mentioned article.

In the CA 2 424 708 A1 For example, a method and apparatus for detecting a collision between a vehicle and an object are disclosed. Optical fibers are arranged along a front bumper of the vehicle. The optical fibers comprise in their fiber cladding light exit regions, which are arranged along the optical fibers. A collision leads to a bending of the optical fibers. The attenuation of the light transmitted in the optical fibers changes by the bending of the optical fiber when the optical fiber is bent in the light exit region. From the thus modulated light, a signal is obtained, which is processed in a signal processor. A safety device, eg for lifting a bonnet, can be activated in this way.

task The invention is a sliver for a fiber optic sensor, in particular to provide a bending sensor which is insensitive to Radiation from the outside is. About that It is also an object of the invention, a use of the sliver specify.

The Task is solved by the characteristics of the independent Claims. Advantageous developments of the invention are characterized in the subclaims.

The Invention is characterized by a sliver for a fiber optic sensor, which has a first and at least a second Optical fiber, each comprising a fiber cladding, which in a light exit area interrupted or structured by elevations and / or depressions is. In addition, a shell material provided that the first and the at least one second optical fiber surrounds at least in the light exit region and is formed such that light of a fiber wavelength, for the the optical fibers are designed to be absorbed.

During operation of the fiber band according to the invention, light is fed into the optical fibers at one longitudinal end, which has a fiber wavelength adapted to the optical fibers. Depending on a bending of the sliver or of the optical fibers occurs more or less light over the respective Lichtaustrittsbe rich in the fiber coat. The light passing through the optical fibers is used to measure the attenuation of the optical fiber. In conventional fiber ribbons, light can also be coupled into the optical fibers via the light exit regions, as a result of which a measurement with the optical fibers is falsified. In particular, when used in a pedestrian protection system, therefore, the irradiation is problematic, for example, with bright halogen light or sunlight in a conventional sliver, since in this way unintentional protection systems can be triggered.

One Advantage of the sensor tape according to the invention is therefore that light radiation from external light sources through that for the light of the fiber wavelength impermeable shell material can not get to the light exit region of the optical fibers and thus a coupling of light into the optical fibers of Outside is prevented. An accuracy and reliability of a sliver according to the invention for one fiber optic sensor is opposite usual solutions improved.

In an advantageous embodiment of the invention comprises the shell material a fiber intake from a for the light of the fiber wavelength impermeable Material. It encloses the fiber receptacle the first and the at least one second optical fiber flush. The material of the fiber intake can advantageously be one for the light the fiber wavelength impermeable Plastic comprising, for example, by at least one acrylate is formed. To make the fiber receptacle impermeable to the light of the fiber wavelength make, the plastic can with color pigments and / or with soot particles be offset.

The Fiber receptacle forms a matrix in which the optical fibers are preferably side by side mechanically connected to each other, for example by a plastic or adhesive, such as acrylic. at usual solutions be for it used transparent materials that are an undesirable Allow coupling of light radiation from the outside. In contrast this can advantageously a correspondingly colored plastic or Adhesive used in particular the light of the fiber wavelength of a coupling into the optical fibers via the light exit areas keeps. For this purpose, the plastic or the adhesive with suitable color pigments and / or soot particles are colored, so the desired impermeability for light the fiber wavelength to reach.

In a further exemplary embodiment of the invention the wrapping material one on both sides of the first and the at least one second optical fiber applied laminate cladding, which is impermeable to the light of the fiber wavelength. It can the optical fibers are also combined in a fiber receptacle or matrix be. In this case, the fiber intake or the matrix may be both have transparent properties or according to the invention for light the fiber wavelength impermeable be.

In an advantageous embodiment of the laminate jacket by a Foil and a film applied to the film which is impermeable to the light of the fiber wavelength educated. The film may, for example, a polyethylene terephthalate, PET film be. For example, the layer applied to the film may be formed by a colored coating of the film. By the Colored coating of the film can be achieved by laminating the laminate the property of the invention has, for Light of the fiber wavelength impermeable to be. This is especially the case when using cheap and easy-to-process PET films that are usually beneficial transparent and therefore for the light of the fiber wavelength permeable are.

alternative can for the Laminate coat other materials used for light the fiber wavelength impermeable are, for example, colored Foils or other plastics.

In another exemplary embodiment of the invention the wrapping material a jacket comprising a composite of the first and the at least second Covered optical fiber and is impermeable to the light of the fiber wavelength. The composite can be embodied for example as a fiber receptacle or matrix, because of he inventive properties of the mantle the fiber intake or matrix turn both with transparent as well as with for Light of the fiber wavelength impermeable Material can be formed.

In an advantageous embodiment, the jacket by a formed on the composite molded and / or extruded plastic. Alternatively, the sheath may pass through a tube impermeable to the light of the fiber wavelength be formed. The jacket thus provides both an optical advantage Protection against coupling light of the fiber wavelength in the Optical fibers as well as a mechanical protection of the sliver or the optical fibers against damage.

The Fiber wavelength, for the the optical fibers are designed, for example, a wavelength for red Correspond to light. In this case, the fiber wavelength, for example, a value between 625 nm and 740 nm.

One Sliver in one of the embodiments shown can be for example, in an impact sensor device of a pedestrian protection system of a vehicle. Alternatively, a sliver according to the invention for one fiber optic sensor used in the field of medical technology. For example, let a sensor with the sliver according to the invention on the back of a Attach patient, thereby measuring movements of the patient or a movement behavior of the patient is analyzed can be. The invention leaves but also for use other applications where bends are detected or to be sensed.

The Invention will be described below in several embodiments with reference to the Figures closer explained. Functional or equivalent elements contribute same reference numerals.

It demonstrate:

1 a vehicle and an impact object,

2 an impact sensor device,

3 an exemplary embodiment of an optical fiber with light exit area,

4 a first embodiment of a sliver,

5A and 5B different views of a second embodiment of the sliver and

6 a third embodiment of the sliver.

In 1 is a vehicle 1 with a crash sensor device 2 shown. The impact sensor device 2 has a sensing area 4 on that along a bumper 3 of the vehicle 1 is arranged. By means of the sensing area 4 can the impact sensor device 2 an impact of an impact object 5 detect. The impact objective 5 may be a pedestrian, for example. Further, the vehicle points 1 an evaluation unit 6 on, in the from the impact sensor device 2 delivered measurement signals are evaluated and, depending on the course of the respective measurement signal to an impact of the impact object 5 and, if necessary, measures to protect the impact object 5 or the vehicle occupants are initiated. These measures may be, for example, a slight lifting of a hood of the vehicle or an ignition of one or more airbags.

In the 2 Shock sensor device shown 2 includes the evaluation unit 6 and a sensor band 7 that includes a bending sensor or that forms the bending sensor. The sensor band 7 has a supply area 8th , a reversal area 9 and the sensing area 4 on. The evaluation unit 6 may include light sources and light sensors that tied to the sensor 7 are coupled. Alternatively, the light sources and / or the light sensors can also be arranged in the bending sensor. By bending the sensor band 7 in the sensing area 4 the attenuation of the light in the sensor band changes 7 , The evaluation unit 6 is designed to detect this change in damping.

3 shows an embodiment of an optical fiber 10 how it can be used in the sliver according to the invention. The optical fiber 10 includes a fiber core 14 and a fiber coat 13 , The fiber coat 13 is in a light exit area 15 structured by elevations or depressions. Alternatively, the fiber cladding 13 in the light exit area 15 also be interrupted.

Light that is in the fiber core 14 is guided on the fiber cladding 13 that has a refractive index other than the fiber core 14 has, usually reflected. In the light exit area 15 However, there is a change in the refractive index of the fiber cladding 13 so that light does not go back to the fiber core 14 is reflected, but over the light exit area 15 is discharged to the outside. The amount of light passing over the light exit area 15 is decoupled, ie the attenuation, the optical fiber 10 depends on a bending of the optical fiber 10 in the area of the light exit area 15 from. For example, the attenuation is compared to an unbent optical fiber 10 decreases at a bend down, while attenuation at a bend upwards compared to the unbent fiber 10 is increased.

The fiber core 14 the optical fiber 10 may be formed for example by a polymeric plastic fiber. Alternatively, the optical fiber 10 designed as a glass fiber. The optical fiber 10 usually has a round cross-section. Alternatively, the optical fiber 10 have a rectangular or square cross-section.

4 shows a first embodiment of a sliver. A first optical fiber 10 , a second optical fiber 11 and other optical fibers 12 are doing of a fiber intake 30 enclosed flush. The fiber intake 30 represents in this embodiment, a shell material 20 for the optical fibers 10 . 11 . 12 is or is of the shell material 20 includes. The fiber intake 30 is formed by a material impermeable to light of the fiber wavelength. For example, for the operation of a fiber optic sensor with the sliver uses red light beams so that the fiber wavelength corresponds to a wavelength of red light. For example, the fiber wavelength is between 625 nm and 740 nm. Thus, the fiber band can be operated, for example, with a fiber wavelength of 650 nm.

The fiber intake 30 , which can also be referred to as a matrix, can be formed in this embodiment by a plastic which is mixed with color pigments and / or with soot particles. As a result, according to the invention, light beams are prevented from the outside at a wavelength corresponding to the fiber wavelength via the respective light exit region 15 in one of the optical fibers 10 . 11 . 12 is coupled. For example, as a material for fiber intake 30 an acrylic-containing plastic or adhesive used.

Through the fiber intake 30 become the optical fibers 10 . 11 . 12 fixed so that a defined position of the light exit areas, not shown here 15 can not be changed.

at a conventional one Fiber intake without application of the principle of the invention is usually a transparent plastic used. This makes it possible for that Light or parts of the light that are on the fiber intake or the optical fibers strikes, over the light exit areas is coupled into the optical fibers. This can be special in bright halogen light or direct sunlight problematic be.

Usually, such systems are operated with fiber optic sensors with pulsed light signals, so that a permanent irradiation of the optical fibers regularly leads to no negative influence on the optical system. However, a change of light, for example due to drop shadows of avenue trees when using the sliver in a vehicle could lead to an erroneous detection and an unwanted activation of a protective measure, such as an airbag. By the use of wrapping material according to the invention 20 which is specifically opaque to the fiber wavelength, erroneous detection can be prevented. This advantageously leads to increased safety when used in an impact sensor device 2 a pedestrian protection system of a vehicle 1 ,

It may be sufficient if the wrapping material 20 or the fiber intake 30 in the respective light exit areas 15 the optical fibers 10 . 11 . 12 has the property of being impermeable to light of the fiber wavelength. However, it is advantageous from a production point of view, if the optical fibers 10 . 11 . 12 or the sliver in the Sensierungsbereich 4 , in the reverse area 9 and in the supply area 8th is formed such that the light of the fiber wavelength is absorbed.

5A shows a further embodiment of a sliver according to the invention. Here are the optical fibers 10 . 11 . 12 in a composite 31 summarized, for example, like a fiber intake 30 is formed. In this case, the material of the composite 31 be transparent to light of the fiber wavelength. The material of the composite is advantageous 31 impermeable to light of the fiber wavelength.

The composite 31 is made of a laminate sheath on both sides 40 includes. The laminate jacket 40 is thus on the optical fibers 10 . 11 . 12 applied on both sides. The laminate jacket 40 has in this embodiment, each top and bottom of a slide 41 on, on the one layer 42 is applied. Because the layer 42 According to the invention is impermeable to light of the fiber wavelength, the laminate sheath 40 Prevent light from the fiber wavelength in the optical fibers 10 . 11 . 12 is coupled. The laminate jacket 40 puts the wrapping material 20 is or is covered by this.

The laminate jacket 40 In turn, in addition to the optical protection against light of the fiber wavelength also provides mechanical protection against damage to the sliver.

As a foil 41 For example, a PET film can be used. The on the slide 41 applied layer 42 can be achieved by a colored coating of the film 41 to reach. Alternatively, a colored foil 41 can be used without additional coating 42 is impermeable to light of the fiber wavelength. In a further alternative embodiment, the film 41 For example, in a layered structure of the film, a layer impermeable to light of the fiber wavelength 41 ,

5B shows a further view of the sliver with a laminate sheath 40 , The optical fibers 10 . 11 . 12 that in the composite 31 are held together as in 5A shown on both sides by a laminate sheath 40 surround.

6 shows a further embodiment of the sliver. A composite 31 in this case comprises optical fibers 10 . 11 . 12 as well as fibers 16 , The fibers 16 have a larger diameter or cross section than the optical fibers 10 . 11 . 12 and serve, for example, the stabilization of the sliver. The fibers 16 can be designed as optical fibers. Alternatively, the fibers have 16 no light-guiding function.

The wrapping material 20 in this embodiment comprises a jacket 50 that the composite 31 closed and impermeable to the light of the fiber wavelength. Thus, in turn, it is achieved that light radiated from outside onto the fiber sliver is absorbed by the cladding material 20 is absorbed at least in the fiber wavelength.

The coat 50 For example, by one on the composite 31 molded and / or extruded plastic may be formed. The plastic has in this case the light-absorbing properties.

Alternatively, the coat 50 formed by an impermeable to the light of the fiber wavelength hose.

A fiber ribbon for a fiber optic sensor in one of the illustrated embodiments may be used, for example, in an impact sensor device 2 a pedestrian protection system of a vehicle 1 according to 1 be used. Alternatively, the sliver can be used in a measuring system for analyzing a movement behavior of a patient in medical technology. In this case, for example, a fiber-optic sensor is glued with the sliver on the back of a patient, so as to measure the movements or flexion of the patient's back.

1

vehicle

2

Impact sensor device

3

bumper

4

sensing area

5

impact object

6

evaluation

7

Sensorband

8th

lead region

9

reversal region

10 11, 12

optical fiber

13

fiber cladding

14

fiber core

15

Light output region

20

shell material

30

fiber intake

31

composite

40

laminate coat

41

foil

42

layer

16

fiber

50

coat

Claims (15)

A fiber ribbon for a fiber optic sensor, comprising - a first and at least a second optical fiber ( 10 . 11 ) each with a fiber cladding ( 13 ) located in a light exit area ( 15 ) interrupted or structured by elevations and / or depressions; and - a shell material ( 20 ), the first and the at least one second optical fiber ( 10 . 11 ) at least in the light exit area ( 15 ) and is configured such that light of a fiber wavelength for which the optical fibers ( 10 . 11 ) are absorbed. A sliver according to claim 1, wherein the wrapping material ( 20 ) a fiber intake ( 30 ) comprising a material which is impermeable to the light of the fiber wavelength, and the fiber receptacle ( 30 ) the first and the at least one second optical fiber ( 10 . 11 ) encloses flush. A sliver according to claim 2, wherein the material of the fiber intake ( 30 ) comprises a plastic impermeable to the light of the fiber wavelength. A sliver according to claim 3, wherein the plastic is formed by at least one acrylate. A sliver according to claim 3 or 4, wherein the plastic with color pigments and / or soot particles is offset. A sliver according to any one of claims 1 to 5, wherein the wrapping material ( 20 ) on both sides of the first and the at least one second optical fiber ( 10 . 11 ) applied laminate jacket ( 40 ) which is opaque to the light of the fiber wavelength. Sliver according to Claim 6, in which the laminate sheath ( 40 ) through a foil ( 41 ) and one on the film ( 41 ) applied to the light of the fiber wavelength impermeable layer ( 42 ) is formed. Sliver according to Claim 7, in which the film ( 41 ) is formed by a PET film. A sliver according to claim 7 or 8, wherein the sliver on the film ( 41 ) applied layer ( 42 ) by a colored coating of the film ( 41 ) is formed. A sliver according to any one of claims 1 to 9, wherein the wrapping material ( 20 ) a coat ( 50 ), which is a composite ( 31 ) of the first and the at least one second optical fiber ( 10 . 11 ) is closed and impermeable to the light of the fiber wavelength. A sliver according to claim 10, wherein the sheath ( 50 ) by one on the composite ( 31 ) molded and / or extruded plastic is formed. A sliver according to claim 10, wherein the sheath ( 50 ) is formed by a tube which is impermeable to the light of the fiber wavelength. A sliver according to any one of claims 1 to 12, wherein the fiber wavelength of a Wavelength for red Light corresponds. A sliver according to claim 13, wherein the fiber wavelength is between 625 nm and 740 nm. Use of a sliver according to one of claims 1 to 14 in a crash sensor device ( 2 ) of a pedestrian protection system of a vehicle ( 1 ).