WO2005011511A1

WO2005011511A1 - Force sensor for an elongate device

Info

Publication number: WO2005011511A1
Application number: PCT/EP2004/008062
Authority: WO
Inventors: Thorsten Kern; Thorsten Meiss
Original assignee: Technische Universität Darmstadt
Priority date: 2003-08-01
Filing date: 2004-07-19
Publication date: 2005-02-10
Also published as: DE10335313B4; DE10335313A1

Abstract

Disclosed is a sensor for detecting a force acting on an elongate device, especially an elongate medical device such as a catheter, said force comprising a non-neglectable force component in the longitudinal direction of the elongate device. The inventive sensor encompasses: a force transducer for the force that is to be detected; a connection for mounting the sensor on the elongate device; at least one light input area which can be optically connected to at least one optical waveguide that injects light into the sensor; a light intensity modulator which modulates a predetermined intensity of the light that can be injected into the sensor according to the force applied to the force transducer; and at least one light-decoupling area via which the light having modulated intensity can be decoupled in at least one optical guide.

Description

FORCE SENSOR FOR A LONG STRETCH FURNITURE

The invention relates to a force sensor, a force sensor unit, an elongated device and a method for detecting a force.

A particular application of this invention relates to catheter technology, which is determined by an elongated device for at least partially inserting into an organism through an opening in the body. These elongated devices are used primarily in minimally invasive surgery on human bodies in particular. In order that during the invasion of the elongated device, no body vessels are injured by the tip of the elongated device which is to be operated manually by the attending physician, the doctor necessarily orients itself to the forces that are communicated to him in a handle of the elongated device. Because of the friction and the catheter mass continuously increasing in the course of the invasion of the catheter into the body, the force communicated to the treating doctor on the handle gives a barely usable information about the resistance actually occurring at the tip of the catheter. In order for the attending physician to be able to communicate the correct actuation force to the handle of the catheter, an extraordinarily rich wealth of experience in the operation of catheters is required.

From DE 103 03 270 a catheter arrangement is known in which the force acting on the catheter tip during insertion is measured by a force sensor. The physician is tactilely informed of the corresponding measured variable via a haptic handle. This makes it easier for an inexperienced doctor to find, for example, wire branches or perforations on the cardiac septum. An electrodynamic drive device which uses the measured variable representing the force at the tip to generate the haptic preload is known from DE 103 19 081. Both of the aforementioned documents should be incorporated here with reference, in particular with regard to the sensor system for detecting the forces at the tip of the elongated device and the evaluation of the measurement signals. According to US Pat. No. 6,221,023, a force sensor is provided at the tip of catheters, which is based on a resistive functional operation. The force introduced into the sensor is absorbed by a resistance bridge circuit. The sensor must be connected via several lines, in particular for the supply of electrical energy and for signal transmission to an external evaluation unit, the laying of at least one cable requiring a large amount of space along the catheter. The construction of this sensor is complex due to the large number of parts, and the associated high manufacturing costs make the known sensor particularly unsuitable for catheters due to their preferred disposable property. In addition, the miniaturizability of the electrically operated force sensor, in particular below a catheter diameter of less than 3 mm, can only be achieved with an extremely high level of design effort, if at all. Furthermore, an electrical force sensor is susceptible to faults with regard to electromagnetic radiation from a magnetic resonance tomograph, which vulnerabilities are to be eliminated in particular in medical technology.

DE 44 104 63 discloses a fiber optic sensor with two optical fibers, one of which is connected to a light source. The ends of the two optical fibers lie opposite a mirrored end of a bending beam, which is clamped quasi-firmly in a capsule housing. The position of the mirrored end is measured by reflecting the end of the beam. The ratio of the light components reflected in the two ends of the optical fibers results in an evaluation independent of absolute intensity measurements. This fiber optic sensor is not suitable for use with a catheter insofar as the sensor can only detect forces transverse to the longitudinal extension of the optical waveguide. Furthermore, the disclosed sensor structure is not suitable for miniaturization of elongated devices with lateral dimensions of less than 3 mm.

It is an object of the invention to provide a simply constructed sensor which can be integrated into elongated devices with a diameter of less than 3 mm, in particular 0.33 mm (1 French), and which can detect forces which are at least partially applied to the elongated device in its longitudinal direction attack.

This object is achieved by the features of patent claim 1. The sensor according to the invention is then designed to detect a force that is exerted on an elongated direction, in particular an elongated medical device, such as a catheter or guide wire, which force can have a non-negligible force component in the longitudinal direction of the elongated device. The sensor according to the invention has a force transducer on which at least the essential part of the force to be detected can be introduced either directly via the elongated device or directly into the sensor. According to the invention, the sensor should be such that it can be attached to the elongated device and can be retrofitted, in particular, to existing elongated devices. According to the invention, the sensor has at least one light coupling area, at which light can enter the sensor in particular in a predetermined, known intensity. The light coupling area is optically connected to at least one optical waveguide, which connection can be realized inside the sensor or outside, the optical waveguide preferably being connectable to a light source outside the sensor. The sensor according to the invention has a light intensity modulator which modulates the predetermined intensity of the light which can be coupled into the sensor as a function of the force which is introduced into the sensor via the force transducer, that is to say changes as a function of the force. The sensor according to the invention has a light coupling-out area which can also form the light coupling-in area and via which the light of modulated intensity can be coupled out into at least one light guide. The same light guide can be used that is already used to couple the light into the sensor. The modulated or unmodulated light intensity can be evaluated by an evaluation unit that is particularly external to the sensor and that can determine the amount of force to be determined using a proportional relationship between the change in intensity and the force ,

The sensor according to the invention offers the following advantages over the known force sensors mentioned above:

• With the sensor according to the invention, there is the possibility of integrating a force sensor system into elongated devices which have a lateral extension or a diameter of less than 3 mm, in particular 0.33 mm (1 French);

• The sensor according to the invention is suitable for mass production because of the small number of parts; • The simple construction of the sensor according to the invention easily meets the high requirements of hygiene in medical technology; With the sensor according to the invention, very precise force magnitude and / or force effect measurements can be achieved due to the use of the sensitive light intensity measurement variable; and

• The sensor according to the invention dispenses with electrical lines which, particularly when using a magnetic resonance tomograph, can falsify the measurement results because of the electromagnetic alternating fields that occur.

The sensor according to the invention can detect forces according to the amount and / or the direction of action in real time and in particular continuously. In particular, the sensor according to the invention is designed to detect a force mainly in the longitudinal direction of the elongated device.

In a preferred embodiment of the invention, a reflector is provided which has a reflection surface assigned to the at least one light decoupling region. The reflection surface is designed to be force or pressure sensitive in such a way that it can change its reflection properties as a function of the load acting on the force transducer. The initial, unloaded reflection properties of the reflector are preferably restored automatically after the load has been released. In the case of certain disposable products, however, it may be advantageous to forego reversibility of the reflection properties with regard to low manufacturing costs. The reflective surface preferably changes to a force effect in such a way that it is enlarged or reduced.

In a further development of the invention, the reflection surface is designed to be uneven, in particular curved. Due to the unevenness of the reflection surface, the coupled light is more or less strongly reflected. This deterioration or improvement in the reflection properties can be changed by the force input into the force transducer of the sensor in that the degree of unevenness changes accordingly. In the case of a curved reflection surface, this can preferably be flattened or leveled when force is applied, as a result of which a higher or lower light intensity to a predetermined level Point can be created, which is preferably the light decoupling area of the sensor. In this way, a higher or lower intensity than the predetermined, known initial intensity can be generated, which can be interpreted by the evaluation unit as an increasing or decreasing force on the elongated device.

In a special further development of the invention, a spherical force transducer is provided which is designed to be reflective on its side facing the light input and / or light output region.

In a further development of the invention, the particularly uneven reflection surface can be dimensionally stable in such a way that it irreversibly or reversibly expands and / or limits the dimensions of the light decoupling area. In particular, the material defining the light decoupling area is softer than the dimensionally stable reflection surface, so that when force is applied to the force transducer of the sensor, the particularly uneven reflection surface comes into engagement with the material and the latter increases and / or decreases in a way that impresses the shape of the reflection surface.

With this further development, the number of parts of the sensor is further reduced, because the functions of sub-components of the sensor are taken over with the hardness properties of main components.

In a further embodiment of the invention, the change in light intensity dependent on the force is achieved in that a reflector is provided with a reflection surface which has a more or less strong reflection scattering component. The initial intensity that can be felt by the evaluation device is less than the intensity of the light coupled into the sensor. By shifting the position of the reflector relative to the light input and / or output area, light components can reach the light output area, which in the unloaded state were lost due to a reflection angle that is too strong for the intensity detection on the evaluation unit.

In a further embodiment of the invention, the force transducer is designed as a chamber, which is filled with a fluid, in particular gas, such as air, and in particular is pneumatically working, and is delimited by a flexible, in particular elastic, wall. Opposite the light input and output area of the sensor is a rigid reflector plate with In particular, a flat reflection surface is provided which, depending on the force acting on the air chamber, can be approximated or removed from the light input and output area. A suitable elastomer material and silicone, in particular an organism-compatible one, can be used for the elastic wall of the chamber.

In a special embodiment of the invention, the modulation of the light intensity of the injected light is carried out as a function of the load acting on the force transducer on the basis of polarization change phenomena of the light in the sensor. For this purpose, a photo-elastic material is used, which is connected downstream of a polarizer, in particular a polarization grating, in the direction of coupling the light. In addition, the photoelastic material is followed by a reflector, in particular a reflection plate, which directs the first polarized and then polarization-modulated light in the direction of the light coupling-out area of the sensor. According to this development of the invention, before the reflected polarization-modulated light passes through the light coupling-out area, it must cross the polarizer of the same polarization direction. The change in the light intensity compared to the predeterminable, known light intensity after the first step through the polarizer provides information about the strength of the force- or pressure-dependent polarization modulation in the photo-elastic material.

An additional polarizer with respect to the light coupling direction is preferably connected upstream of the reflector, which greatly increases the sensitivity of the sensor according to the invention.

In a further embodiment of the invention, an elastic housing for the sensor is provided, which seals the individual sensor elements in a fluid-tight manner on the elongated device. This housing can be formed as a covering from a deformable material, such as silicone. The deformable material preferably encapsulates or encapsulates the sensor elements or the entire sensor.

In a further embodiment of the invention, a diaphragm arrangement is provided which is designed to be load-deformable and / or movable in such a way that it changes the light intensity of the coupled-in light by varying the diaphragm opening or the diaphragm passage. The light path to be influenced by the diaphragm arrangement is generated by a reflector arrangement, which preferably consists of at least two reflectors, which are arranged so that the injected light is redirected to the light decoupling area. In the light path of the reflector arrangement, an aperture is arranged to be movable depending on the force acting on the force transducer and can interrupt the light path to a greater or lesser extent in accordance with the force acting on the transducer. The light intensity that can be determined at the light decoupling area provides information about the force acting on the elongated device. The reflector arrangement is, in particular, immovable or stationary relative to the light coupling-in area and / or the light coupling-out area. Alternatively, the cover can be mounted in a fixed position, the reflectors being provided with a predetermined displacement path which can be labeled by the reflector arrangement by the force acting on the force transducer.

The light intensity signal emerging from the sensor is preferably evaluated monochromatically and / or over a spectrum.

In a development of the invention, the housing surrounding the sensor is at least partially rigid, so that the introduction of the force into the force transducer is made possible in a defined direction.

Furthermore, the invention relates to a sensor unit which has at least one optical waveguide which can be connected or connected to at least one light source and a sensor according to the invention.

In a development of the invention, the sensor unit comprises at least two, in particular several, preferably five optical waveguides, which are in particular arranged parallel to one another. In a special embodiment of the invention, an average optical waveguide is surrounded by a plurality of external optical waveguides in a concentric arrangement of the same circumferential distance. With this multi-light waveguide arrangement, the direction of action of an engaging force can also be determined.

In a development of the invention, the sensor according to the invention is arranged on the end face of the at least one optical waveguide, it being possible for the sensor, in particular with its force transducer, to be in direct contact with the at least one optical fiber. An adapter can be arranged between the elongated device and the sensor so that the force can be introduced in a predeterminable manner into the sensor, in particular on the force transducer, in accordance with a specific sensor structure.

In addition, the invention relates to an elongated device, in particular an elongated medical-technical device, such as a catheter, which device has at least one optical waveguide which is connected to at least one light source and a sensor according to the invention which is optically connected to the optical waveguide.

In a development of the invention, the sensor according to the invention or the sensor unit according to the invention is positioned in the region of the distal end of the elongated device in the elongated device, a small distance from the distal end being preferred. The sensor should not be directly exposed to the forces, rather the forces should be transmitted to the sensor or the sensor unit via an adapter piece of the elongated device.

In a development of the invention, the at least one optical waveguide extends along the elongated device from the sensor, preferably to an evaluation unit. The sensor is preferably attached to at least one guide wire of the elongated device.

In a special development of the invention, the longitudinal extension of the elongated device is essentially formed exclusively by the at least one optical waveguide. Guidewires are therefore not necessary if a fiber material is selected for the optical waveguide that has both the corresponding optical properties and the necessary strength and flexibility.

Finally, the invention relates to a method for detecting a force acting on an elongated device. An initial intensity of a light measurement variable is then predetermined, the light measurement variable is modulated as a function of the force, the modulated light intensity is compared with the predetermined initial intensity, and a non-negligible force component in the longitudinal direction of the elongated device is determined on the basis of the ratio of the initial intensity to the modulated intensity. Further advantages, features and properties of the invention will become apparent from the following description of preferred embodiments of the invention with reference to the accompanying drawings, in which:

Fig. La is a schematic diagram of the sensor according to the invention in a first embodiment, which is shown in an unloaded state;

Fig. Lb the sensor of FIG la in a loaded state.

2a shows a schematic diagram of a second embodiment of the sensor according to the invention, which is shown in an unloaded state;

2b shows the sensor according to FIG. 2a in a loaded state;

3a shows a schematic diagram of a third embodiment of the sensor according to the invention, which is shown in an unloaded state;

3b shows the sensor according to the invention according to FIG. 3a in a loaded state;

4a is a schematic diagram of a fourth embodiment of the sensor according to the invention, which is shown in an unloaded state;

4b shows a schematic diagram of the sensor according to the invention according to FIG. 4a;

5a shows a schematic diagram of a fifth embodiment of the sensor according to the invention, which is shown in an unloaded state;

5b the sensor according to the invention according to FIG. 5a in a loaded state;

6a is a plan view of a sensor according to the invention shown in a schematic diagram in the fifth embodiment, which is shown in an unloaded state;

6b shows a view according to FIG. 6a of the sensor according to the invention in a loaded state; 7a is a schematic side view of the fifth embodiment of the sensor, which is shown in an unloaded state;

7b shows the sensor according to FIG. 7a in a loaded state;

8 shows a distal region of one end of an elongated medical device, such as a catheter.

The first embodiment of the sensor 1 according to the invention shown in FIGS. 1 a and 1 b comprises a force transducer 3, which in the embodiment according to FIGS. 1 a and 1 b has a spherical elastic body 5 and / or a housing 7, which is formed, for example, from silicone. For easy manufacture of the sensor according to the invention, the housing 7 is formed as an encapsulating part around the body 5. For an assembly-fixed coupling of the force transducer to an optical waveguide 11, the housing 7 grips firmly around the end 13 of the optical waveguide 11.

The spherical body 5 has a reflection surface 15, which is assigned to a light input and output area, both of which can be defined as an intermediate or transition point, at which light leaves the optical waveguide and enters the body 5, that is to say the sensor.

La and lb, the spherical body 5 rests against the end face 19 of the end 13 of the light guide 11, so that there is a reflection surface 15 in the contact area of the spherical body 5 and the optical waveguide 11, also adjacent to the contact area in the Optical waveguide 11 is effective. The light 21 to be coupled through the light guide 11, which has an initial intensity, passes through the light coupling area on the surface 19 directly to the reflection surface 15 of the spherical body 5, is reflected there and arrives again via the light coupling area on the surface 19 of the optical waveguide 11 the latter as a light beam 23, the light intensity of which is evaluated by a monochromatic evaluation unit (not shown) or a spectrum which is preferably arranged at the end of the light guide 11. As indicated schematically in FIG. 1 a, only a part of the coupled light is reflected on the curved surface 15 of the spherical body 5 in such a way that light returns to the optical waveguide via the light decoupling area. The stronger the curvature is formed on the spherical body 5, the weaker is the light 23 reflected in the optical waveguide, which is to be indicated by the arrow 23 narrower than the arrow 21.

It is also conceivable to provide a reflection surface 25 diametrically opposite the reflection surface 15 in a modified embodiment. In this case, the spherical body 5 is to be made transparent, so that the coupled-in light is reflected through the light body 5 at the reflection surface 25 in order to partially reach the optical waveguide 11 via the light decoupling region.

If a force F directed essentially along the waveguide 11 is communicated to the force transducer 3, as shown in FIG. 1b, both the elastic housing 7 and the elastic, spherical body 5 deform from their essentially spherical initial shape into an egg shape. or EUipsoid form, as indicated in Fig. lb. Due to this deformation, the degree of curvature on the reflection surfaces 15 and / or 25 decreases, so that the effective reflection surface 15 and / or 25 increases and the reflected light associated with the light decoupling region of the sensor 1 can be introduced into the waveguide 11 with a higher intensity.

A calibration of the force sensor with regard to the ratio of degree of curvature / force, degree of curvature / effective reflecting surface, effective reflecting surface / modulated intensity can be used to perform a quantitative evaluation of the force based on the modulated light intensity.

2a and 2b show an alternative embodiment, the same reference numerals being used for better readability of the figure description for identical and similar components of the sensor of the alternative embodiment according to the invention, which are increased by 100.

The sensor 101 according to the invention shown in FIGS. 2a and 2b differs from the sensor 1 according to FIGS. 1a and 1b in that the spherical body 105 is formed from a solid material which is harder than the material of the optical waveguide 111 at its end 113 is. For the housing 107, as in the embodiment according to FIGS. 1 a and 1 b, an elastic material, such as silicone, is used, so that flexible encapsulation and fastening of the force transducer 103 to the optical waveguide 111 is ensured.

As shown in FIG. 2b, the end 113 of the waveguide 100 is pressed in due to the force F acting in the longitudinal direction of the optical waveguide 100. Due to the spherical indentation area, the contact area is increased, ergo the reflection area 115 is increased, which leads to light with a greater modulated intensity reaching the optical waveguide 111 via the light decoupling area of the sensor 101.

If the optical waveguide 111 is designed to be elastically reversible at its end, any number of force impressions can be detected by the sensor 101 according to the invention.

Another preferred embodiment of the invention is shown in FIGS. 3a and 3b. For better readability of the description of the figures, similar and identical components are provided with the same reference numbers, which are increased by 200, with respect to the embodiment according to FIGS.

The sensor 201 according to FIGS. 3a and 3b according to the invention is designed to produce the desired light intensity changes dependent on the force via the phenomenon of polarization of light. The sensor 201 according to the invention comprises a sandwich arrangement 231, which is arranged in the extension of the optical waveguide 211. Immediately on the free end surface 219 of the optical waveguide 211, a polarizer 233 in the form of a polarization grating of the first polarization direction is arranged in the light input and output area of the sensor 201. The light arriving at the polarizer 233 from a light source (not shown) connected to the optical waveguide 211 is polarized according to the first polarization direction and enters a photo-elastic body 235 forming the force transducer 203, the polarization direction of which is changed when the photo-elastic body 235 is applied with force is applied, which results in asymmetrical internal stress, which is indicated in Fig. 3b.

A planar reflector 237 is arranged on the photo-elastic body 235, which reflects light by 180 degrees in the opposite direction. That again the photo-elastic body 235 passing light no longer changes its polarization direction and is filtered again at the polarizer 233 of the first polarization direction.

In the relaxed state of the sensor 201 according to the invention shown in FIG. 3a, the photo-elastic body 235 is set in relation to the polarizer 233 and the reflector 237 in such a way that the light intensity is not weakened when it passes through the sandwich arrangement 231. In the loaded state of the sensor 201 shown in FIG. 3b, the light polarized by the polarizer 233 enters the photo-elastic body 235, where the polarized light is modulated in accordance with the force F acting on the sensor 201 such that the polarization direction of the polarized light changes , in particular is elliptically polarized, so that the amount of the directional component by which the polarizer 233 filters decreases. This decrease explains the light intensity weakening of the light beam 223, which is generated during the second passage of the light through the polarizer 233 under load and can be determined quantitatively by the evaluation unit (not shown).

A further polarizer (not shown) of the same polarization direction or a second polarization direction is preferably arranged between the photo-elastic body 235 and the reflector 237.

The sandwich arrangement 231 is encapsulated or encapsulated by an elastic housing 207 made of silicone, the housing 207 holding the sandwich arrangement 231 firmly at the end 213 of the optical waveguide 211.

4a and 4b show a further alternative embodiment of the sensor according to the invention, with the same reference numerals being used for identical or similar components with respect to the embodiment according to FIGS. 1a and 1b, which are increased by 300.

The sensor 301 has, as a force transducer 303, an airtight chamber 341 which delimits on the optical fiber side through the free end surface 319, on the side regions through the housing 307, for example made of silicone, and on the end region opposite the end surface 319 by a plate reflector 343. The chamber 341 is filled with a fluid, in particular air. Because of the elasticity of the side walls 345 of the housing 307, there is movement of the reflector 343 towards the end face 319 of the optical waveguide 311 can be realized towards or away.

The reflector 343 or the reflection surface 347 assigned to the light input and output area of the sensor 301 is designed such that only part of the light 321 passing through the light input area is reflected on the reflection surface 347 in the opposite direction along the light guide 311 and thus via the light output area back into the optical fiber 311. The rest of the light is lost as scattered light 349 against the walls 345 of the housing 307 of the evaluation unit (not shown).

If a force F is communicated to the sensor 301, as shown in FIG. 4b, the volume of the chamber 341 is reduced and the fluid contained therein is thus pressurized. As indicated in Fig. 4b, however, with the reduction in the chamber 341, the distance of the reflector 343 from the end face 319 of the optical waveguide 311, that is to say the light coupling-out area of the sensor 301, is reduced to a greater or lesser extent, so that a larger part of the reflected light , ie also part of the scattered light, which is not taken into account in the relaxed state, reaches the optical waveguide 311 and thus to the evaluation unit (not shown). The intensity of the light beam 323 is therefore significantly stronger in the loaded state, which increase in intensity corresponds to a determinable increase in force at the sensor 301.

The sensor according to the invention shown in FIGS. 5a and 5b is a further alternative embodiment, in which, with respect to the sensor according to FIGS. 1a and 1b, the same reference numbers are used for identical or similar components, which are increased by 400.

The sensor 401 according to the invention can be referred to as an aperture arrangement which has a deformable aperture unit 451 which is designed in the form of an overlapping structure, namely a structure overlapping a reflector 453. Furthermore, a reflector arrangement comprising two reflectors 453 and 455 is provided, which are arranged in such a way that a light 421 entering above the light coupling area of sensor 401 is deflected at first reflector 455 by approximately 90 degrees. The deflected light beam 422 is again deflected by 90 degrees at the reflector 453, so that the light beam 423 returns to the optical waveguide 411 via the light decoupling area of the sensor 401. In an embodiment according to FIGS. 5a and 5b, two optical waveguides 411a and 411b are arranged symmetrically next to one another, the optical waveguide 411a being responsible for the light 421 to be coupled in and the optical waveguide 411b for the light 423 to be coupled out.

The aperture unit 451 is elastically deformable such that when the sensor 401 is subjected to a force F directed in the longitudinal direction of the optical waveguides 411a and 411b, the aperture unit 451 lowers into the light path between the reflectors 453 and 455 and thus an uninterrupted light path from the reflector 453 and 455 to the reflector 453 prevented. This weakening of the light intensity can be assigned to a certain force by the evaluation unit (not shown).

Both the reflector arrangement and the diaphragm unit 451 are encapsulated by a silicone material, which forms the housing 407. The housing 407 encompasses the end 413 of the optical waveguides 411a and 411b in such a way that the reflectors 453, 455 are positioned stationary with respect to the end surface 419 and the diaphragm unit 451.

6a, 6b, 7a and 7b show a further preferred embodiment of the sensor according to the invention which, in addition to the amount of the acting force F, can also determine the direction of action of the force F. For better readability of the description of the figures, the same reference numbers, which are increased by 500, are used for similar and identical components with regard to the design of the sensor according to FIGS. 1a and 1b.

The sensor 501 according to the invention is provided with a plurality of light input and output areas, each of which is assigned to one or more of the optical waveguides 511a, 511b, 511c, 511d, 51 le. The optical fibers 511a to 511e are arranged parallel to one another and extend in a longitudinal direction. The optical waveguides 511a to 511d are arranged concentrically with a central optical waveguide 51le at a constant circumferential distance.

The sensor 501 has a reflection spherical body 561, which is essentially encapsulated in an elastic full housing 563. The full housing 563 encompasses sections of the optical waveguides at the ends of the optical waveguides 511a to 511e, to keep them in position and to keep the reflection body 561 in a controlled, safe position relative to the light input and output areas.

The middle optical waveguide 511e serves to couple light into the transparent full housing 563 via a light coupling region, the light striking the reflection body being reflected by a reflection surface. If no force or an axial force acts, the injected light is largely thrown back into the optical waveguide 511e, which is indicated in FIGS. 6a, 7a, or the injected light is of a higher intensity than the unloaded state reflected in the optical fiber 51 le.

If, as in FIGS. 6b and 7b, a force F acts on the load-bearing housing 563, the reflection body approaches the end faces 519 of the optical waveguides 511a to 51le due to the flexibility of the housing, i.e. is axially displaced, and becomes over the end faces 519 the optical waveguide 511a to 511e shifted, that is to say shifted radially. Due to the axial change in the distance of the reflection body 561 to the end faces 519 of the optical waveguides 511a to 511e, the evaluation unit, not shown, can determine the axial force component due to the increased intensity, which acts in the longitudinal direction of the optical waveguides 511a to 51 le. The transverse or radial component of the force can be determined quantitatively via the light intensity of the four outer optical waveguides 511a to 511e, here by partially covering the optical waveguide 51lc with light.

In this embodiment, all end faces 519 of the optical waveguides 511a to 511e thus act as light decoupling areas. The elastic full housing 563 is the force transducer 503 of the sensor 501 according to the invention.

In all of the five different designs of the sensor according to the invention, a force / light intensity modulator is provided, which in the designs according to FIGS. La, lb, 2a, 2b, 4a, 4b, 5a, 5b, 6a, 6b, 7a, 7b Force modulates the light intensity directly, whereby changes in intensity are caused by mechanical force deformation phenomena. In the embodiment according to FIGS. 3a and 3b, the change in intensity is brought about by means of changes in polarization, which in turn are brought about by the force. 8 schematically shows the end region 71 of a catheter according to the invention, the end of which is slightly curved or hook-shaped in order to be able to insert the catheter end more easily into Y artery branches. The sensor 1 according to the invention is not arranged directly on the tip 73, but at a certain distance from the tip 73, so that an axial force input can be forced into the sensor. The region 75 of the catheter facing the tip 73 can have additional catheter devices. On the side 77 of the sensor 1 facing away from the tip 73, the at least one optical waveguide (not shown in more detail) is provided, the catheter in this section from the sensor to the actuating device being able to be formed exclusively from an optical waveguide which has an opaque, organism-compatible outer skin ( not shown) can have.

The features of the invention disclosed in the above description, in the drawings and in the claims can be essential individually as well as in any combination for realizing the invention in its various embodiments.

Technical University Darmstadt list of reference symbols

1, 101, 201, 301, 401, 501 sensor

3, 103, 203, 303, 403, 503 force transducers

5, 105 spherical bodies

7, 107, 207, 307, 407, 507 housing

11, 111, 211, 311, 41 la, b, 511a to e optical waveguide

13, 113, 213, 313, 413, 513 end

15, 115 reflective surface

17, 117 light decoupling area

19, 119, 219, 319, 419 end face

21, 121, 221, 321, 421 light to be coupled in

23, 123, 223, 323, 423 modulated light

25 reflective surface

26 end area 73 tip

75 catheter area

77 opposite side

231 sandwich arrangement

233 polarizer

235 photo-elastic body

237 reflector

341 chamber

343 reflector

345 side walls

347 reflective surface

349 flare

422 light path

451 aperture unit

453, 455 reflector

561 reflective body

563 full housing

F force

Claims

Technical University Darmstadt T50010PCTPatents

1. Sensor for detecting a force (F) acting on an elongated device, in particular an elongated medical device, such as a catheter, with a non-negligible force component in the longitudinal direction of the elongated device, comprising a force transducer (3, 103, 203, 303, 403, 503) for the force to be detected, a connection for attaching the sensor (1, 101, 201, 301, 401, 501) to the elongated device, at least one light coupling area, which emits at least one light into the sensor (1, 101 , 201, 301, 401, 501) coupling optical fiber (11, 111, 211, 311, 411 a, b, 511 a to e) can be optically connected, a light intensity modulator which has a predeterminable intensity of the sensor (1, 101, 201, 301, 401, 501) of light that can be coupled in (21, 121, 221, 321, 421) according to the force (F) acting on the force transducer (3, 103, 203, 303, 403, 503), and at least one light decoupling area . Via which the light (21, 121, 221, 321, 421) of modulated intensity can be coupled out into at least one light guide (11, 111, 211, 311, 41 la, b, 51 la to e).

2. Sensor according to claim 1, which is designed for continuous real-time detection of forces (F) according to the amount and / or the direction of action.

3. Sensor according to claim 1 or 2, which is designed to detect a substantially in the longitudinal direction of the elongated device acting force (F).

4. Sensor according to one of claims 1 to 3, in which a reflector (237, 343, 453, 455) is provided with a reflection surface (15, 115, 347) assigned to the at least one light decoupling region (17), the reflection surface of which is dependent on of the force (F) to be detected, preferably deforming, in particular irreversibly or reversibly and depending on the force (F) to be detected, in particular increasing and / or decreasing.

5. Sensor according to claim 4, in which an uneven reflection surface (15, 115) is provided, soften the force (F) acting on the force transducer (3, 103, 203, 303, 403, 503) in such a way that the Degree of unevenness changes depending on the force (F) and extends and / or limits an area of the reflection surface (15, 115) optically connected to the least one light decoupling area (17, 117).

6. Sensor according to claim 4 or 5, wherein the in particular spherical force transducer (3, 103,) has a curved reflection surface (15, 115).

7. Sensor according to any one of claims 4 to 6, in which the uneven reflection surface (15, 115) is designed to be dimensionally stable in such a way that it expands and / or limits the dimensions of the at least one light decoupling region when force is applied, in particular the at least one Area that defines the light decoupling area is impressively enlarged and / or reduced.

8. Sensor according to one of claims 4 to 7, in which an uneven reflection surface (15, 115) of the force transducer (3, 103), when force is applied, impressively and irreversibly or reversibly presses into the at least one optical waveguide (11, 111).

9. Sensor according to one of claims 1 to 3, in which a reflector (343) with a reflection surface assigned to the at least one light coupling-out area (347) is provided with a reflection scattering component, with which the light intensity can be modulated as a function of the force (F) to be detected is.

10. Sensor according to one of claims 1 to 3 or 9, in which a reflector (343) is arranged in relation to the at least one light decoupling area (17) in such a way that, as the force transducer (303) is subjected to increasing force, reflection components of increasing scattering angle in the at least one light decoupling area ( 17, 117, 317) to increase the light intensity.

11. Sensor according to claim 9 or 10, in which a fluid-tight chamber (341) filled with a fluid, in particular gas, such as air, is formed, which is partially delimited by the reflector (343) optically assigned to the light coupling and decoupling region.

12. Sensor according to claim 11, wherein the chamber (341) is delimited by a flexible and / or deformable, in particular elastic wall material, in particular silicone.

13. Sensor according to one of claims 1 to 3, or 9 to 12, in which the light intensity of the coupled light (221) is modulated by means of a transparent medium which changes the polarization of light (221) when force is applied.

14. Sensor according to claim 13, wherein a polarizer (233) and a photo-elastic body (235) is arranged in such a way to the light coupling and light coupling-out area that light (221) coupled into the sensor (201) via the polarizer (233) and polarized Light reaches the light decoupling area via the photo-elastic body (235).

15. Sensor according to claim 13 or 14, wherein a sandwich arrangement (231) in the order of a polarizer (233), a photoelastic body (235), preferably another polarizer, and a reflector (237) is provided, wherein in particular the sandwich arrangement (231) connects to one end of the at least one optical waveguide (211) and serves as a photoelastic force transducer.

16. Sensor according to one of claims 1 to 3, in which a reflector arrangement of at least two reflectors (453, 455) is provided for deflecting light coupled in through the light coupling-in area through to the light coupling-out area, with a particularly deformable, in particular elastic A light path (422) along the reflector arrangement can be interrupted to a greater or lesser extent depending on the force (F).

17. Sensor according to claim 16, in which the reflectors (453, 455) of the reflector arrangement are arranged in a stationary manner with respect to the light coupling-in area and the light coupling-out area.

18. Sensor according to one of claims 1 to 17, wherein the reflector (237, 343, 453, 455), the sandwich arrangement (231), the force transducer (3, 103, 203, 303, 403, 503) and / or the sensor (1, 101, 201, 301, 401, 501) itself is surrounded by a coating of a deformable material, such as silicone, in a fluid-tight manner, in particular encapsulated or encapsulated, so that in particular the reflector (237, 343, 453, 455), the sandwich Arrangement (231), the force transducer (3, 103, 203, 303, 403, 503) and / or the sensor (1, 101, 201, 301, 401, 501) itself relative to the elongated device, in particular the at least one optical waveguide (11, 111, 211, 311, 411a, b, 511a to e), are movable.

19. Sensor unit with a sensor (1, 101, 201, 301, 401, 501) designed according to one of claims 1 to 18 and at least one optical waveguide (11, 111, 211, 311, 411a, 411b, 511a to e) that can be connected or connected to at least one light source,

20. Sensor unit according to claim 19, in which at least two, in particular several, preferably five optical fibers (511a to e) are arranged parallel to one another.

21. Sensor unit according to claim 19 or 20, in which a central optical waveguide (511e) is surrounded by a plurality of external optical waveguides (511a to d), which are positioned in particular with the central optical waveguide (511e) in a concentric arrangement of the same circumferential distance.

22. Sensor unit according to one of claims 19 to 21, wherein the sensor (1, 101, 201, 301, 401, 501) on an end face (19, 119, 219, 319, 419, 519) of the at least one optical waveguide (11 , 111, 211, 311, 411a and b, 511 a to e) is attached, in particular the force transducer (3, 103, 203, 303, 403, 503) in direct contact with at least one optical waveguide (11, 111, 211 , 311, 411, 511).

23. Sensor unit according to one of claims 19 to 22, in which an adapter can be attached, which is designed for predeterminable introduction of the force acting on the elongated device (F).

24. Elongated device, in particular medically technical elongated device, such as catheters, with at least one optical waveguide (11, 111, 211, 311, 411a and b, 511a to e), which is connected to at least one light source, and one with the at least one Optical fibers (11, 111, 211, 311, 411a and b, 511a to e) optical connected sensor (1, 101, 201, 301, 401, 501) designed according to one of claims 1 to 18 for detecting a force (F) acting on the elongated device.

25. The elongated device according to claim 24, wherein the sensor (1, 101, 201, 301, 401, 501) is arranged in the region of a distal end of the elongated device, in particular at a distance from the distal end.

26. The elongated device according to claim 24 or 25, wherein the at least one optical waveguide (11, 111, 211, 311, 411a and b, 511a to e) extends along the elongated device from the sensor (1, 101, 201, 301, 401, 501) extends.

27. Elongated device according to one of claims 24 to 26, wherein the sensor (1, 101, 201, 301, 401, 501) is attached to at least one guide wire of the elongated device.

28. Elongated device according to one of claims 24 to 27, the longitudinal extent of which is essentially formed by the at least one optical waveguide (11, 111, 211, 311, 411a and b, 51 la to e).

29. A method of measuring a force (F) engaging an elongated device, particularly an elongated medical device such as a catheter, wherein: an initial intensity of a light measurement variable is predetermined, the light measurement variable is modulated as a function of the force (F) that modulated light intensity is compared with the predetermined initial intensity and a non-negligible force component in the longitudinal direction of the elongated device is determined based on the ratio of the initial intensity to the modulated intensity.

30. The method according to claim 29 with method steps corresponding to the mode of operation of the sensor (1, 101, 201, 301, 401, 501) specified in one of claims 1 to 19.