DE102006046693A1 - Fiber optic sensor device - Google Patents

Abstract

The present invention relates to a fiber optic sensor device comprising an optical fiber having a light source coupled at a first end and a light detector coupled to the optical fiber at a second end, and means for detecting a deformation based on a change in the intensity of the light received by the optical fiber. In order to develop a fiber optic sensor device of the type mentioned a fiber optic sensor device of simpler construction and thereby also provide opportunities for cheaper production, it is proposed that at the first end (3) of the optical fiber (2) light of multiple frequencies or wavelengths (lambda <SUB> r </ SUB>, lambda <SUB> b </ SUB>, lambda <SUB> g </ SUB>) is coupled, which is coupled to the optical fiber (2) at a second end (7) light detector (8) is designed for frequency-selective intensity evaluation and the light emission regions (12) on the optical fiber (2) in coordination with the at the first end (3) coupled frequencies or wavelengths (lambda <SUB> r </ SUB>, lambda <SUB > b </ SUB>, lambda <SUB> g </ SUB>) are formed selectively acting.

Description

The The present invention relates to a fiber optic sensor device, the one optical fiber with coupled at a first end of the light source and one coupled to the optical fiber at a second end Light detector, and means for detecting a deformation based a change the intensity of the light received by the optical fiber.

Without restriction its field of application, the present invention is below Reference to the automotive sector. The automobile and Automotive sector is due to the high system requirements at the same time high cost pressure due to the high sales figures an economically very important area of application. alternative Areas of application in aircraft technology or in architecture and similar be basically not excluded.

Fiber optic sensor devices of the aforementioned type are known for example from WO 94/29671 A1 known. They are now used equally for slow, as well as fast-running bending or deformation processes and therefore find application in modern passenger cars. Thus, for example, a rapid detection of a collision of a motor vehicle with a pedestrian or cyclist by such sensors to initiate so-called active security measures, such as caused by pyrotechnic elements or an electric drive inclinations of a hood executed.

Based on the teaching of WO 94/29671 A1 has been developed by the applicant, a fiber optic sensor device through which a shape of a shock absorber on a motor vehicle over watches and thus a kind of accidental deformation can be detected. Thus, in the case of a crash, a distinction can be made between a collision with a pedestrian and, for example, a dustbin or a traffic sign. The fiber-optic sensor is constructed using four to 16 optical fibers which have been mechanically scratched or chemically defined at certain areas on their lateral surface. Thus, light emission surfaces or areas are created with a variety of forms. Fiber-optic sensor devices of the type mentioned regularly have light-emitting diodes as the light source, each of which is connected to an optical fiber, generally less than 2 m long, in the form of a polymeric optical fiber or polymer optical fiber, or POF for short.

It Object of the present invention, a fiber optic sensor device of the said type to further simplify their structure and This also means possibilities to create a cheaper production.

These The object is solved by the features of the independent claim. Further advantageous features of developments of the invention are the subject the dependent claims.

Draws according to the invention an optical sensor device of the type mentioned by from that at a first end of the optical fiber more light Frequencies coupled to the optical fiber at one second end coupled light detector for frequency-selective intensity evaluation is formed and the light emission areas on the optical fiber in agreement with the frequencies coupled in at the first end are formed frequency-selectively acting.

In order to can over the Length too only a single optical fiber multiple light emission areas are arranged, which are different from each other, as they respectively only for a frequency or a narrow frequency band act as light emission areas. Other frequencies are due to these light emission areas in the Propagation within the optical fiber is not substantially impeded. Of the Structure of a fiber optic sensor device with determination of a Type of a respective deformation is thereby considerably simplified.

In a preferred embodiment According to the invention, the light emission regions are so-called Bragg gratings wavelength selective acting educated. To produce such filters are high precise method known by which, however, an optical fiber itself not mechanically damaged becomes. Because every damage the fiber acts as a predetermined breaking point is by avoiding the reliability especially with the different strong vibration and torsional loads optical fibers in automotive technology significantly increased.

advantageously, If the optical fiber is designed as a polymeric optical fiber or POF, those with direct letters regarding at least one refractive index n manipulated light emission region is provided. The direct letter on or in a POF is z. B. from the field of micro-photolithography for Production of structures on silicon wafers by means of laser is known and will now taking advantage of the accuracy of illustrations in used this new field of application.

Preferably, the light of several frequencies by a corresponding broadband radiating LED coupled to the first end of the optical fiber. In this case, the light detector at the second end of the optical fiber is preferably designed as a so-called rbg sensor in coordination with the wavelength-selective light emission regions. Thus, in one embodiment of the invention, only one opto-electrical component has to be provided or coupled at both ends of the optical fiber.

Further Features and advantages of the invention will be described below of exemplary embodiments with reference to the figures of the drawing. In the Drawing show in schematized form:

1 : An embodiment of a fiber optic sensor device with a single optical fiber, broadband emitting LED, a trained for frequency-selective intensity evaluation light detector and three wavelength-selective light emission regions;

2 FIG. 2 is a schematic diagram of the function of a prior art fiber optic sensor device; FIG.

3 A known embodiment of a fiber optic sensor device according to a plurality of optical fibers 2 to provide an overall device capable of localizing and determining a type of deformation;

4a : An illustration of a basic structure and the operating principle of an optical fiber with end-side circuits according to the embodiment of 1 with exemplary beam path for the selective attenuation of light of a specific wavelength;

4b : a representation analogous to 4a with exemplary beam path for selective attenuation of light of a second specific wavelength;

4c a representation analogous to the two preceding figures with exemplary beam path for the selective attenuation of light of a third specific wavelength;

5a : a sketch of the arrangement according to the 4a -C with ideally undamped transmission of light of all wavelengths and

5b : a sketch of the arrangement analogous to the representation of 5a with indication of a selective signal attenuation due to a deformation of the optical fiber.

About the various embodiments and figures will hereafter be given the same reference numerals and names for same function or assemblies and process steps used.

3 shows a fiber optic sensor device 1 According to the state of the art. The fiber optic sensor device 1 includes an optical fiber 2 at a first end 3 the optical fiber 2 in a docking area 4 to a light source 5 with a face 6 and at a second end 7 to a light detector 8th is coupled. Not shown are circuit electronics and means for detecting a deformation in the region of a sensitive zone 9 based on a change in the intensity of the out of the optical fiber 2 in the light detector 8th received light. This sensitive zone 9 , which is realized inter alia by so-called High or Modes filter or HOMF as a scattering and / or loss range, is between the feed by the light source 5 and a diversion 10 arranged in a reversal point over a section.

Such a fiber optic sensor device 1 So senses a bending of the optical fiber 2 On the basis of intensity deviations and is therefore also advantageously used as a crash sensor in a passenger vehicle in areas of the body, which are deformed in accidents with pedestrians or cyclists. In order to take effective active safety measures to improve the protection of an injured person, such as an increase in the impact angle to create a softer catch structure in the hood, even a small deformation must be detected by such a sensor quickly and safely.

For cost reasons come in a known sensor device 1 LEDs as light sources 5 at about λ = 660 nm together with appropriately matched photodetectors as light detector components 8th for use. To be based on such a device 1 also be able to detect a kind of deformation, four to 16 separate sensor devices 1 summarized, as in the picture of 3 based on three such sensor devices 1 indicated in a bundling. Here, the length L of the optical fibers 2 in the present example, about 1.5 m. The sensitive zones 9 the individual fibers 2 are arranged offset from one another in such a way that they form a sensor area 11 form. The sensor area 11 is in an accident under the action of a force U with a sickle-shaped in the manner indicated in the above-indicated distribution with respect to its sub-areas 9 deformed differently. Out of it each fiber 2 as opposed to different attenuations of light intensity a normal case without deformation in one area 9 can be determined partial deformations, which per fiber 2 also a place can be assigned. This means that a deformation that is currently occurring as a result of the accident can be determined quickly and reliably, piece by piece, from individual results.

The device overhead for a sufficiently high resolution localization and shape determination 3 However, it also increases with the use of fiber optics bundled into cables or fiber ribbons, etc. 2 proportional to the number of sensitive parts 9 , 1 now shows an embodiment that breaks this rule by simple means. Here includes a fiber optic sensor device 1 a single POF optical fiber 2 that at the first end 3 is supplied or fed by a broadband emitting light emitting diode. The optical fiber 2 has a trained for frequency selective intensity evaluation light detector 8th and three wavelength-selective light emission regions 12 on. These light emission areas 12 are implemented in the present embodiment as a wavelength filter in the form of Bragg gratings. The filter effect is due to regionally limited changes in a refractive index n in the optical fiber in certain structures 2 causes, these refractive index changes are produced defined by direct writing or similar methods. Each of these filters has a respective tuning to one of the wavelengths λ _r , λ _b , λ _g . In the present case, the light source 5 Light emitted in the visible spectrum and the frequencies of the wavelengths λ _r , λ _b , λ _g are in the range of the visible colors red R, blue B and green G.

This type of filters and related manufacturing processes, such. As the direct writing or the photo-inscription for writing a defined structure in a waveguide with high accuracy in particular using a laser to produce refractive index changes by deviations in the material density, are known in the field of telecommunications and there for wavelength multiplex or Wavelength domain multiple access, WDM for short, adapted for fiber and polymer technology. For producing such frequency selective light emitting regions 12 on the optical fiber 2 must the optical fiber 2 Therefore, they are no longer damaged on their mantle or cladding and thus weakened mechanically.

The episode of 4a to 4c shows the operation of the above-described fiber optic bending and deformation sensor device 1 again in schematic form for the three selected frequencies with the respectively associated wavelengths λ _r , λ _b , λ _g in detail. 4a is a Dar position of a basic structure and the principle of operation of an optical fiber 2 with end-side circuits according to the embodiment of 1 with exemplary beam path for selective attenuation of light only the predetermined wavelength. For the sake of clarity, only two exemplary propagation paths are shown exclusively for light of the wavelengths λ _r that are present in the multimode fiber 2 each are capable of propagation to the core area in total reflection. A first path 13 extends through the exemplified fiber portion of the light source 5 to the detector 8th , This first path runs 13 also by a with respect to the wavelength λ _b selectively acting light emission region 12 , Because this light emission area 12 However, only on the wavelength λ _b selectively acts as a loss area, the light of wavelength λ _r passes this light emission area 12 essentially without damping and continues on the marked path 13 continued.

Different with a path 14 : Here, light of wavelength λ _r meets two light reflections after two total reflections 12 , which is tuned exactly to the wavelength λ _r . The light on this path 14 becomes the fiber 2 Completely deprived by decoupling in the outer space.

The pictures of the 4b and 4c show representations analogous to 4a with exemplary beam paths based on the paths 15 . 16 . 17 . 18 for the selective attenuation of light of a second and third predetermined wavelength λ _b , λ _g . The mode of action is always the same, so that in a rbg sensor as a one-piece photodetector 8th Finally, for each of these wavelengths, a radiation intensity in an unbent normal state can be determined.

5a shows a schematic diagram of the arrangement according to the 4a C in the case of ideally undamped transmission of light of all relevant wavelengths λ _r , λ _b , λ _{g of} an exemplary intensity distribution of these wavelengths, as at the rbg detector 8th is recorded. 5b shows a sketch of the arrangement analogous to the representation of 5a with an indication of selective signal attenuation due to deformation of the optical fiber 2 as they are in 3 in the known device 1 with three optical fibers 2 for three sensitive zones 9 already sketched. The deformation of 5b has been chosen so small that only the wavelength λ _r experiences a weakening of the intensity. Already the quasi adjacent arranged frequency selective for the color blue B acting light emission area 12 is no longer affected by the deformation, so that from the occurring only for the wavelength λ _r signal attenuation on a deformation of small extent just at the location of the Lichtemissionsbe Reich 12 for the wavelength λ _r can be concluded. The construction of the device 1 to 5b However, this is much less expensive than that in the known device 1 to 3 the case was.

In this case, in this embodiment, as a light source 5 a white light source LW T67C from Osram and as a photodetector 8th a silicon photodiode 59032-02 Hamamatsu photonics used. This is an inventive device 1 using commercially available components and known methods, wherein the use of Bragg gratings as a filter of the wavelength-selective light emitting regions 12 neither etching nor any other mechanical deformation of the optical waveguide 2 more are needed.

Due to the novel design of the fiber optic bending and position sensor device 1 could the number of optical fibers 2 with the same functionality over known devices 1 be lowered significantly. This is accompanied by an advantageous reduction in the number of opto-electrical components, ie light sources 5 and photodetectors 8th , As well as a reduction in the number of electrical and preferably executed via connectors optical connections to these opto-electrical devices in the example cases of six to only two achieved. This saves additional costs for secure connector systems. This results in a total of a fiber optic bending and position sensor device 1 with a compact design that provides information about a value and a location of a bend even using only a fiber optic cable 2 POF-based, whereby all applications, such as those in the WO 94/29671 A1 are known with such a device with improved quality and more compact design can be displayed.

1

sensor device

2

optical fiber

3

first end of the optical fiber 2

4

coupling area

5

light source

6

End face of the optical fiber 2

7

second end of the optical fiber 2

8th

light detector

9

with respect to deformation-sensitive zone of an optical fiber 2

10

redirection

11

Sensor Range / sensitive Zone for location and shape determination

12

wavelength selective acting light emission area

13

first path

14

path

15

path

16

path

17

path

18

path

n

refractive index

λ _r

wavelength

λ _b

wavelength

λ _g

wavelength

R

colour red

B

colour blue

G

colour green

L

length

U

deforming force

Claims (6)

Fiber optic sensor device comprising an optical fiber ( 2 ) with at a first end ( 3 ) coupled light source ( 5 ) and one to the optical fiber ( 2 ) at a second end ( 7 ) coupled light detector ( 8th ), and means for detecting a deformation based on a change in the intensity of the optical fiber ( 2 ) in the light detector ( 8th ), characterized in that at the first end ( 3 ) of the optical fiber ( 2 ) Light of several frequencies or wavelengths (λ _r , λ _b , λ _g ) is coupled to the optical fiber ( 2 ) at a second end ( 7 ) coupled light detector ( 8th ) is designed for frequency-selective intensity evaluation and the light emission areas ( 12 ) on the optical fiber ( 2 ) in agreement with those at the first end ( 3 ) coupled frequencies or wavelengths (λ _r , λ _b , λ _g ) are formed selectively acting. Sensor device according to claim 1, characterized in that the light emission areas ( 12 ) are formed as Bragg gratings wavelength-selectively acting. Sensor device according to one of the two preceding claims, characterized in that as light source ( 5 ) a broadband emitting LED is provided. Sensor device according to one of the preceding claims, characterized in that more than two different frequency-selectively acting light emission regions ( 12 ) on the optical fiber ( 2 ) are provided, preferably three different frequency selective light-emitting regions ( 12 ) per optical fiber ( 2 ). Sensor device according to one of the preceding claims, characterized in that the optical fiber ( 2 ) is formed as a polymeric optical fiber (POF), which is provided with a light emission region manipulated by direct writing with respect to at least one refractive index (n) ( 12 ) is provided. Sensor device according to one of the preceding claims, characterized in that the light detector ( 8th ) is designed as a rbg sensor.