Light guide and optical implant having a light guide

Abstract

The invention relates to a light guide (1) for an optical implant, having a substrate (3) which is elongated in a main direction (2) from a proximal end (21) to a distal end, a light-guiding core (4) which is arranged on the substrate (3), extends along the substrate (3) in the main direction (2) from a coupling-in end (19) at the proximal end (21) and ends with a coupling-out end (5) in front of the distal end, a coupling-in optical unit (18) which couples light incident in the main direction (2) into the at least one light-guiding core (4), and a coupling-out optical unit (6) which deflects light emerging from the coupling-out end (5) into a transverse direction extending transversely to the main direction (2). The coupling-in optical unit (18) is formed as a one-piece continuous optical body (24) on the coupling-in end (19) of the at least one light-guiding core (4) and the substrate (3) in such a way that the at least one light-guiding core (4) ends with its coupling-in end (19) within the coupling-in optical unit (18) and is embedded in the coupling-in optical unit (18) at least over a minimum length along the main direction (2), and / or the coupling-out optical unit (6) is formed as a one-piece continuous optical body (7) on the coupling-out end (5) of the at least one light-guiding core (4) and the substrate (3) in such a way that the at least one light-guiding core (4) ends with its coupling-out end (5) within the coupling-out optical unit (6) and is embedded in the coupling-out optical unit (6) at least over a minimum length along the main direction (2). The minimum length is equal to the thickness (17) of the core (4) on the substrate (3).

Description

[0001] Light guide and optical implant with light guide

[0002] TECHNICAL AREA OF INVENTION

[0003] The invention relates to a light guide for an optical implant. In particular, the invention relates to a light guide having the features of the preamble of independent claim 1. Furthermore, the invention relates to an optical implant with such a light guide. The optical implant may, in particular, be an optical cochlear implant.

[0004] In optical cochlear implants, the electrical power required to operate light sources for activating transferred neurons is a critical factor. The transferred neurons, or rather the rhodopsins expressed in the neurons via gene therapy, must be illuminated with a relatively high amount of light from the cochlear implant for activation to occur. Therefore, focusing the light emitted by the cochlear implant is advantageous. However, it is known that when inserting the optical fiber of a cochlear implant into the cochlea, it can easily become twisted around its main direction. This causes problems because the neurons that can be activated are located only on the inner surface of the cochlea.

[0005] STATE OF THE ART

[0006] A waveguide for an optical cochlear implant with the features of the preamble of independent claim 1 is known from C. Helke et al.: On the Fabrication and Characterization of Polymer-Based Waveguide Probes for Use in Future Optical Cochlear Implants, Materials 2023, 16, 106, 22.12.2022. The known waveguide is lithographically formed on a silicon wafer and ultimately detached from this wafer. First, an elongated substrate is formed on the wafer, on which several light-guiding cores are then arranged side by side at intervals, their distal ends being located at varying distances from a distal end of the substrate. The cores are covered with a sheath that, together with the substrate, covers the respective core in all lateral directions and also at its distal end.A scattering structure with a contoured surface is positioned on the substrate in front of the distal end of each core. This structure scatters light exiting the core in later directions. Light from a laser diode is coupled into the respective core via a spherical lens. The spaces between the laser diode, the spherical lens, and a holder for the optical fiber are filled with transparent epoxy resin.

[0007] Another optical waveguide for introducing light into biological tissues for the purpose of optogenetic stimulation, comprising the features of the preamble of independent claim 1, is known from JW Reddy et al.: Parylene photonics: a flexible, broadband optical waveguide platform with integrated micromirrors for biointerfaces, Microsystems & Nanoengineering (2020) 6:85. A silicon mold with an end face extending diagonally at 45° is formed on a substrate. The silicon mold is then filled with material for a light-guiding core up to the end face. Subsequently, the core is provided with a top cover. The end face of the silicon mold acts as a mirror, deflecting light guided along the cladding of the light-guiding core laterally, so that the light is coupled out in a transverse direction orthogonal to the main direction of the core.This results in a Gaussian intensity distribution across the cross-section of the emitted light.

[0008] In an optical cochlear implant known from US 2010 / 0174344A1, each light-guiding core of an optical fiber is arranged within a sheath. An optical element with a mirror surface oriented diagonally to the main direction of the core is positioned in front of a distal end of the sheath containing the embedded core. A microlens is arranged on a lateral exit surface of the optical element to focus the light exiting the core.

[0009] From WO 2012 / 103 271 A1, an optical cochlear implant with an implantable stimulation source carrier is known, which has several stimulation contacts. Each stimulation contact has several optical stimulation sub-elements that emit light in different angular ranges around a main direction of the stimulation source carrier and collimate or focus the light in one or both transverse directions to the main direction. For this purpose, the stimulation sub-elements have concavely curved mirrors in front of the ends of individual light sources or optical fibers. The stimulation sub-elements can be activated individually so that only the stimulation sub-element with the greatest stimulation potential is used at any given time. This is the stimulation sub-element with the direct alignment to the neurons to be activated. This known cochlear implant is very complex because several sub-elements must be provided for each stimulation contact.In addition, the adjacent stimulation sub-elements increase the cross-section of the stimulation source carrier.

[0010] From WO 2024 / 159 133 A2, an endoscope device for imaging the cochlea and for image-guided cochlear implantation is known. The endoscope device has an optical imaging probe with a proximal end and a distal end and comprises a fiber connector, an optical probe positioning module, an optical fiber, and an optical probe head. The endoscope device is configured such that the optical probe head provides a focused beam of light, with the optical probe positioning module defining an axial position of the optical probe head. A sheath of the endoscope device with a proximal end and a distal end comprises a flexible sheath, a tube adapter, and a mandrel tube, wherein the flexible sheath, the tube adapter, and the mandrel tube are configured to form a continuous channel and to enclose at least a portion of the optical fiber.The optical probe head features a 3D-printed monolithic structure with two optical surfaces to reflect different light beams laterally and focus them onto adjacent tissue. The light beams are focused to multiple foci, giving the probe an extended depth of focus compared to a traditional single-lens optic.

[0011] From DE 10 2014 208 756 A1, a light guide for industrial, medical, or cosmetic applications is known, comprising an outer circumferential surface and at least one end face made of glass. An optical element made of glass and a transparent plastic is directly molded onto the glass end face by means of reactive injection molding, such that the electromagnetic radiation guided in the light guide during operation is directed through the glass end face into the transparent plastic of the optical element and exits again from it.

[0012] From DE 103 54 730 A1, an optical sensor head for use in a distance sensor is known, which can also be used in holes with a diameter of less than 1 mm. The optical sensor head is mounted on an optical fiber, through which light is coupled into and out of the sensor head, and comprises a fiber extension which is optically coupled to the optical fiber at its end facing the optical fiber and has a deflecting mirror at its other end for coupling the light in and out, and a connecting structure which receives a portion of the optical fiber and the fiber extension coupled to it in a fiber channel and which includes a transparent area for coupling the light guided via the deflecting mirror in and out.

[0013] Outside the technical field of optical fibers for optical implants, an optical device with a taper structure for bidirectional coupling of a waveguide to an external medium is known from DE 102019 009 399 B4. The taper structure comprises a beam input segment to couple a light beam from the waveguide into the taper structure, a beam output segment to focus the light beam and couple it into the external medium, and at least one first reflective surface between the beam input segment and the beam output segment to deflect the light beam out of the plane of the waveguide. The waveguide is designed as a freestanding waveguide arm. The first reflective surface is a total internal reflection surface. The height of the taper structure is continuously tapered in the region of the beam input segment, while the width is kept constant, thus forming a waveguide region.The beam input segment is followed by a substantially conical or pyramidal region, the width and height of which increase linearly. The beam output segment is followed by the conical or pyramidal region and comprises a substantially curved region that includes at least one reflective surface. The taper structure may include at least one further reflective surface. The beam output segment includes a collimating lens. The waveguide is a planar waveguide that may be mounted on a substrate and may be part of a waveguide array. The taper structure may be made of a polymer, and the optical device may be manufactured by 3D printing, in particular by direct laser writing.According to DE 10 2019 009 399 B4, the primary objective is to provide an optical device with a very broad coupling bandwidth, enabling the coupling of a wide spectrum of wavelengths into an external medium. Furthermore, the device aims to couple multiple optical fibers to a waveguide with low loss and achievable placement tolerances. The fundamental concept of DE 10 2019 009 399 B4 is to enable mode-matching of planar waveguides to the external medium, such as an optical fiber or microscope objective, using this optical device. TASK OF THE INVENTION.

[0014] The invention is based on the objective of demonstrating a light guide for an optical implant and an optical implant with such a light guide, in which the optics for coupling in and / or coupling out the light into the at least light-guiding core are designed to be particularly simple despite high optical performance and are integrated into the overall design of the light guide or the optical implant.

[0015] SOLUTION

[0016] The object of the invention is achieved by a light guide for an optical implant having the features of independent claim 1, and by an optical implant having the features of claim 15. The dependent claims are directed to preferred embodiments of the light guide and the implant according to the invention.

[0017] DESCRIPTION OF THE INVENTION

[0018] An optical fiber according to the invention for an optical implant, in particular an optical cochlear implant, comprises a flexible substrate elongated in a principal direction from a proximal end to a distal end. At least one light-conducting core of the optical fiber is arranged on the preferably substrate. This core extends along the substrate in the principal direction from an input end at the proximal end of the substrate, typically for more than 50% of the substrate's length, and terminates with an output end upstream of the distal end of the substrate, i.e., at a distance from the distal end of the substrate. Furthermore, the optical fiber comprises an input optic that couples incident light in the principal direction into the at least one light-conducting core, and an output optic that deflects light exiting the output end of the at least one light-conducting core into a first transverse direction perpendicular to the principal direction.The coupling optics are formed as a single, continuous optical body between the coupling end of the at least one light-guiding core and the substrate, such that the coupling end of the at least one light-guiding core terminates within the coupling optics and is embedded in the coupling optics for at least a minimum length along the principal direction. Alternatively or additionally, the output coupling optics are formed as a single, continuous optical body between the output end of the at least one light-guiding core and the substrate, such that the coupling end of the at least one light-guiding core terminates within the output coupling optics and is embedded in the output coupling optics for at least a minimum length along the principal direction. In both cases, the minimum length is equal to the thickness of the core on the substrate in the region of the coupling optics or output coupling optics.The core can also be embedded in the input or output coupling optics to a thickness several times greater, particularly two to ten times greater. This thickness is typically a few to several micrometers and ranges, for example, from 2 pm to 20 pm.

[0019] In the optical waveguide according to the invention, at least the coupling optics or the output optics are integrally formed optical bodies, in particular homogeneous optical bodies, which are integrally formed with the light-guiding core over at least the minimum length and, as a rule, not only over this minimum length but also beyond it. The integrally formed optical body is thus precisely aligned with respect to the light-guiding core and the substrate and simultaneously improves the mechanical bond between the light-guiding core and the substrate. The defined alignment of the integrally formed optical body with respect to the light-guiding core ensures that, as coupling optics, it precisely couples the incident light in the main direction into the light-guiding core and that, as output optics, it precisely deflects the light exiting the output end into the first transverse direction perpendicular to the main direction.The necessary light guidance is preferably achieved by the single-piece, continuous optical body itself, i.e., with its interfaces to the environment from which the light enters in the main direction or into which it laterally deflects the light exiting the coupling end, without requiring an optically effective coating of these interfaces. As a result, the optical fiber according to the invention comprises only a few different components.

[0020] The optical implant for which the light guide is intended can be a cochlear implant, in which case the substrate must be sufficiently flexible to allow insertion of the light guide into the cochlea. Alternatively, it could be another type of optical implant that works by delivering light, such as an optical implant used to stimulate muscle contraction or a sequence of muscle contractions, for example, of the esophagus or stomach. In such cases, the substrate must also be sufficiently flexible to allow for the correct positioning of the output optics relative to the input optics. The refractive index of the continuous optical element should differ as much as possible from that of the surrounding tissue in which the optical implant is used. Typically, it lies in the range of 1.50 to 1.75.

[0021] The required high functionality of the single-piece, continuous optical body can be achieved, for example, by molding the coupling optics or the output coupling optics onto the light-guiding core and the substrate using a light-curing resin that cures under two-photon excitation. A suitable 3D printing technology for this purpose is commercially available from Nanoscribe GmbH & Co. KG, Eggenstein-Leopoldshafen, Germany (see https: / / www.nanoscribe.com). Specifically, this technology allows for the printing of single-piece, continuous optical bodies with a spatial resolution on the order of 100 nm, enabling the coupling optics and / or the output coupling optics to be 3D printed as micro-optics with a diameter on the order of 1 mm perpendicular to the main direction of the optical fiber according to the invention. High-refractive-index light-curing resins are also available from Nanoscribe GmbH, e.g.,...Under the designation IP-S, a resin with a refractive index n=1.515, see https: / / www.nanoscribe.com / en / products / ip-photoresins / , and under the designation IP-n162, a resin preferred here with a refractive index n=1.62, see https: / / www.nanoscribe.com / en / products / ip-photoresins / ip-n162 / .

[0022] In the optical waveguide according to the invention, the at least one light-conducting core on the substrate is preferably covered with a cladding. The cladding, like the substrate, provides a large refractive index difference compared to the core, ensuring that the light is guided through the core under total internal reflection at its circumference around the main direction. Specifically, the cladding can be made of silicone with a refractive index n = 1.41, with Nusil MED 6215 (see https: / / nusil.avantorsciences.com / nusil / en / product / MED-6215 / optically-clear-low-viscosity-silicone-elastomer) being a preferred material. The cladding can extend into the respective integral optical body of the input or output optics along with the core. It can even extend beyond the input or output end of the core.However, it is preferable if the cladding does not extend beyond the coupling end in order to achieve the most complete possible coupling of the light incident in the main direction into the light-guiding core.

[0023] Preferably, the coupling optics in the optical fiber according to the invention are designed such that they couple collimated light incident in the main direction into the at least one light-guiding core. This facilitates the alignment of the optical fiber relative to a light source that provides the light incident in the main direction. With collimated incident light, the distance of the coupling optics from the light source in the main direction is irrelevant, and a lateral offset relative to the main direction also has no negative effect.

[0024] In a preferred embodiment of the optical fiber according to the invention, the coupling optics are integrally formed on both main sides of the substrate. Alternatively or additionally, the substrate is reinforced at its proximal end, i.e., where the coupling optics are integrally formed, on its second main side facing away from the at least one light-guiding core, with a rigid plate. The coupling optics are then precisely aligned with this rigid plate and can be positioned exactly relative to a light source by positioning the rigid plate.

[0025] In a preferred embodiment of the optical fiber according to the invention, the output optics focus the light deflected in the first transverse direction more strongly in a virtual longitudinal plane spanned by the first transverse direction and the main direction than in a virtual transverse plane spanned by a second transverse direction extending perpendicular to the main direction and the first transverse direction, and the main direction. The distribution of the focused light in the virtual longitudinal plane can have a half-width that is at most 10%, preferably at most 5%, and even more preferably at most 2% of the half-width of the focused light in the transverse plane. In other words, the output optics focus the light selectively in a direction extending along the main direction, but not—or at least to a lesser extent—in a circumferential direction around the main direction.This increases the intensity of the emitted light, but not, for example, the risk that twisting the light guide around its main direction in a cochlea will prevent the neurons to be activated from being hit by the emitted light.

[0026] Specifically, the output optics can focus the light deflected in the first transverse direction in the longitudinal plane, with a resulting line focus of the light in the first transverse direction located at a free distance of 0.5 mm to 1.5 mm from the output optics. The neurons to be activated by an optical cochlear implant are typically located at this distance from the light guide. In the longitudinal plane, the line focus preferably has a width along the main direction of no more than 0.1 mm, although an even smaller width would be advantageous but is limited by the optical capabilities of the output optics. To achieve the desired focusing of the output light in the longitudinal plane, the output optics can have a convex end surface that is more curved in the longitudinal plane than in the transverse plane. Specifically, the convex end surface can have a cylindrical section extending in the second transverse direction.

[0027] Furthermore, the output coupling optics can have a first flat surface inclined at no more than 25° to the main direction in front of the output end of the light-guiding core, on the inner surface of which the light exiting the output end undergoes total internal reflection. Due to the slight inclination of the first flat surface to the main direction, this total internal reflection is achieved without the need for a reflective coating on the first flat surface, i.e., solely through the refractive index difference of the continuous optical body of the output coupling optics compared to its surroundings. Adjoining the first flat surface towards the light output surface of the output coupling optics is a second flat surface, inclined at least 30° to the main direction and no more than 25° to the first flat surface.Total internal reflection of the incident light also occurs at this second flat surface. This includes, on the one hand, the light coming directly from the output end of the light-guiding core, whose direction of propagation is inclined relative to the main direction towards the light-emitting surface, and on the other hand, the light that has already undergone total internal reflection at the first flat surface. A third flat surface can then adjoin the second flat surface towards the light-emitting surface. This third surface is inclined at no more than 25° relative to the second flat surface, at least 30° relative to the first flat surface, and no more than 80° relative to the main direction. A further total internal reflection of the emitted light then occurs at this third surface. In principle, a fourth flat surface can also be connected to this third surface towards the light-emitting surface.The flat surfaces, through total internal reflection, guide the light exiting the core's output end stepwise towards the light exit surface of the output optics, where it is then shaped before exiting into the environment.

[0028] In order to reliably align the output optics with the substrate even in the area of ​​shallowly inclined flat surfaces, the output optics are preferably supported in the area of ​​the first and / or second flat surface by means of feet that are laterally offset in the second transverse direction and aligned in the first transverse direction.

[0029] In addition to the at least one light-guiding core, at least one further light-guiding core can be arranged on the substrate. This further core extends in the main direction from a further coupling end at the proximal end of the substrate over more than 50% of the substrate's length and terminates with a further coupling end in the main direction before the coupling end of the at least one light-guiding core. This further light-guiding core is then associated with a further coupling optic and a further coupling optic with the properties described here for the coupling optic and the coupling optic.

[0030] The output coupling optics molded onto multiple cores and the substrate are spaced apart from each other, while the input coupling optics molded onto multiple cores and the substrate can form a linear microlens array by allowing the individual input coupling optics to merge into one another or by allowing them to be defined and aligned to each other by a rigid plate stiffening the substrate at its proximal end.

[0031] An optical implant according to the invention, which is again in particular an optical cochlear implant, has a closed housing. An array of light sources and a microlens array for collimating the light from the light sources are arranged in the closed housing. A plane-parallel window in the housing adjoins the microlens array. Outside the housing, the optical fiber according to the invention, with its linear microlens array, connects to the window. The space between the window and the linear microlens array can be filled with a hardening transparent material in a cavity on the outside of the housing. This transparent material has a lower refractive index than the through optical elements of the coupling optics. Preferably, this lower refractive index is as close to 1 as possible.In the implant according to the invention, all parts are hermetically enclosed in the housing, which, except for the window, can be made of titanium and the window can be made of sapphire, and only the optical fiber according to the invention leads away from the housing, into which the light is coupled through the window.

[0032] The at least one light-guiding core can have a rectangular cross-section perpendicular to the main direction, with its thickness on the substrate being greater than its width. The thickness-to-width ratio can range from >1:1 to 1:10. However, the ratio is typically no greater than 1:5. The thickness-to-width ratio of the light-guiding core's cross-section can be constant or change continuously from the input end to the output end, increasing or decreasing in the process. The light-guiding core, as well as the input and output optics, can be applied to the substrate as a single, continuous optical element, particularly by 3D printing.

[0033] Advantageous further developments of the invention result from the patent claims, the description and the drawings.

[0034] The advantages of features and combinations of features mentioned in the description are merely exemplary and can have an effect alternatively or cumulatively, without the advantages necessarily having to be achieved by embodiments according to the invention.

[0035] Regarding the disclosure content—not the scope of protection—of the original application documents and the patent, the following applies: Further features can be derived from the drawings—in particular, the geometries depicted and the relative dimensions of several components to one another, as well as their relative arrangement and functional connection. The combination of features from different embodiments of the invention or from features of different claims is also possible, deviating from the chosen cross-references of the claims, and is hereby encouraged. This also applies to features that are illustrated in separate drawings or mentioned in their description. These features can also be combined with features from different claims.Likewise, features listed in the patent claims may be omitted for further embodiments of the invention, but this does not apply to the independent patent claims of the granted patent.

[0036] The features mentioned in the claims and the description are to be understood, with regard to their number, as meaning that exactly that number or a greater number than the stated number is present, without the need for the explicit use of the adverb "at least". Thus, for example, if a substrate is mentioned, this is to be understood as meaning that exactly one substrate, two substrates, or more substrates are present. The features listed in the claims may be supplemented by further features or may be the only features that the subject matter of the respective claim possesses.

[0037] The reference numerals contained in the patent claims do not constitute a limitation of the scope of the subject matter protected by the patent claims. They serve only to make the patent claims easier to understand. BRIEF DESCRIPTION OF THE FIGURES

[0038] The invention will now be further explained and described with reference to preferred embodiments shown in the figures.

[0039] Fig. 1 shows an output optic of a fiber optic cable according to the invention in a first perspective view obliquely from distal.

[0040] Fig. 2 shows the output coupling optics in a second perspective view obliquely from proximal.

[0041] Fig. 3 is a projection of the contours of the output coupling optics according to Figs. 1 and 2 and of the distal end of a light-guiding core embedded therein onto a longitudinal plane in which a principal direction of the light guide runs.

[0042] Fig. 4 is a projection of the contours of the light-guiding core according to Fig. 3 onto a transverse plane that runs perpendicular to the main direction of the light guide.

[0043] Fig. 5 is a perspective view of a coupling optic of an optical fiber according to the invention.

[0044] Fig. 6 schematically shows the interface between parts of an optical cochlear implant, which are arranged in a housing, and a light guide according to the invention.

[0045] FIGURE DESCRIPTION

[0046] Fig. 1 shows a section of an optical fiber 1 according to the invention. On a flexible substrate 3 extending in a principal direction 2 from a proximal end 21 (shown in one of the following figures) to a distal end 34 (shown in one of the following figures), several light-guiding cores 4 are arranged side by side, each extending along the principal direction 2. The individual light-guiding cores 4 terminate at different points in the principal direction 2 before the distal end of the substrate 3. In Fig. 1, the central light-guiding core 4 terminates with its output end 5 in an output optic 6. The output optic 6 is a one-piece, continuous optical body 7, which is formed from a transparent plastic, specifically a resin cured under two-photon excitation, and molded onto the light-guiding core 4 and the substrate 3 by 3D printing. The exact structure of the output optic 6 will be discussed in more detail in connection with Fig. 3.However, Fig. 1 clearly shows that the output coupling optics 6 are supported on the substrate 3 by means of support feet 9, which are oriented normal to the substrate 3 and laterally offset from each other transversely to the main direction 2, in the region of a planar surface 8 inclined relative to the main direction 2 and opposite the output end 5 of the light-guiding core 4. The support feet 9 are areas of the integral optical body 7. The support feet 9 stabilize the output coupling optics.

[0047] 6 compared to the substrate 3.

[0048] In Fig. 1 and the following figures, the sides of the light-conducting cores 4 are marked with lines running perpendicular to the substrate 3, which, however, do not represent a structure of these sides, but only serve to distinguish the sides of the light-conducting cores 4 from other surfaces shown.

[0049] Fig. 2 shows the output coupling optics 6 from an oblique rear view. Fig. 2 shows more clearly than Fig. 1 that the light-guiding cores 4 have approximately rectangular cross-sections that lie flat against the substrate 3.

[0050] The section shown in Fig. 3, running in the main direction 2 and normal to the substrate s in a longitudinal plane, reveals that the light-guiding core 4 extends into the integral optical body 7 of the output coupling optics 6 over a length 22, which is greater than the thickness 17 of the light-guiding core 4 on the substrate 3. This ensures a planar bond between the body 7, the core 4, and the substrate 3. This is true even though the light-guiding core 4 on the substrate 3 is covered by a sheath 10, which also extends over the output end 5 of the light-guiding core 4. The sheath 10 separates the integral optical body 7 of the output coupling optics 6 from the material of the light-guiding core 4, which is embedded in the body 7 with its output end 5. The material bond between the light-guiding core 4 and the integral optical body

[0051] 7 is indirectly connected via the cladding 10. The fact that the cladding 10, which ensures light transmission along the main direction 2 through the core 4 by total internal reflection, also covers the end face of the light-conducting core 4 at its output end 5, does not impair the exit of the light from the output end 5 into the output optics 6, since it strikes the cladding 10 in front of the output end 5 at a large angle. In front of the output end 5 lies the flat surface 8 of the output optics 6, which is inclined at approximately 20° relative to the main direction 2. Light incident from the light-conducting core 4 is totally internally reflected at this surface due to the shallow angle of incidence. The first flat surface 8 is adjoined by a second flat surface 11, which is inclined at about 40° to the main direction 2 and which totally reflects light already totally reflected from the flat surface 8 and light emerging obliquely upwards from the light-guiding core 4.The same applies to a third flat surface 12, which adjoins the flat surface 11 and is inclined at approximately 60° to the principal direction 2. A convex light-emitting surface 13 of the output coupler 6 adjoins the third flat surface 12. Here, the light-emitting surface 13 has the form of a cylindrical segment running perpendicular to the drawing plane. The convex light-emitting surface 13 focuses the light 14 exiting the output coupler 6 into a line focus 15 that runs approximately perpendicular to the drawing plane. Ideally, the line focus 15 is formed along a circular arc segment around the principal direction 2. The line focus 15 lies at a free distance 16, typically 0.5 mm to 1.0 mm in front of the light-emitting surface 13, which is normal to the substrate 3.This is where the optically activated neurons are located when the optical fiber 1 is inserted into a cochlea with transferred neurons as part of an optical cochlear implant. Misalignment of the optical fiber 1 by twisting it around the main direction 2 is harmless due to the line focus 2 extending around the main direction in this circumferential direction.

[0052] Fig. 4 shows a section along a transverse plane, to which the principal direction 2 is a surface normal, of the light-guiding core 4 and its sheath 10 on the substrate 3. The thickness 17 of the core 4 on the substrate 3 is typically on the order of 2 pm to 20 pm. The width of the core 4 along the substrate 3 is approximately the same or, particularly for cores 4 with a smaller thickness 17, about twice as large, and is typically on the order of 5 pm to 25 pm. The substrate 3 has a typical thickness of 5 pm. Specifically, the thickness of the substrate can be 5 pm, the thickness 17 of the core 4 above the substrate 3 can also be 5 pm, and the thickness of the sheath can be 2.5 pm.

[0053] Fig. 5 shows two coupling optics 18 for coupling collimated light incident along the principal direction 2 into coupling ends 19 of two light-guiding cores 4 on the substrate 3. The coupling optics 18 have convex light entry surfaces 20 that project from the proximal end 21 of the substrate 3 opposite the principal direction 2. To stabilize this arrangement, the substrate 3 is reinforced at its distal end with a rigid plate 23, and continuous optical elements 24 of the coupling optics 18 extend to the underside of the substrate 3 or the rigid plate 23. The coupling ends 19 of the light-guiding cores 4 terminate at the level of the proximal end 21 of the substrate 3 within the coupling optics 18.Specifically, the proximal end 21 of the substrate 3 is formed by breaking off the substrate 3 with the light-guiding cores 4 arranged on it, so that the light-guiding cores 4 are not covered by their claddings 10 at their coupling ends 19. The integrally formed optical bodies 24 of the coupling ends 18 are formed on the coupling ends 19 of the light-guiding cores 4 and the substrate 3 in the same way as the integrally formed bodies 7 of the coupling optics 6 are formed on the coupling ends 5 of the light-guiding cores 4 and the substrate 3.

[0054] Fig. 6 schematically shows an interface between parts of an optical cochlear implant 25, which are arranged in a closed housing 26 (shown with a dashed line), and an adjoining light guide 1, as described above. An array of light sources 27 is arranged in the housing 26. Opposite the light sources 27 is a microlens array 28, which collimates the divergent light 29 emitted by the light sources 27. The collimated light 30 exits the housing 26 through a plane-parallel window 31 formed in the housing 26 from sapphire. The collimated light 30 then strikes a linear microlens array 32 formed from the coupling optics 18, which focuses the collimated light 30 into the light-guiding cores 4 of the light guide 1.The relative position of the microlens array 32 from the output optics 18 is fixed by potting a cavity between the window 31 and the linear microlens array 32 with epoxy resin 33. This potting can be achieved by filling a cavity on the outside of the housing 26. Since collimated light 30 exits the housing 26 through the window 31 and strikes the microlens array 32 of the input optics 18, the interface shown in Fig. 6 is relatively insensitive to positioning inaccuracies of the microlens array 32 relative to the collimated light 30. REFERENCE MARK LIST.

[0055] optical fibers

[0056] Main direction

[0057] Substrate light-conducting core

[0058] Detaching

[0059] Output optics, one-piece continuous body of the output optics, 6 first flat surface

[0060] base

[0061] mantel, second plane surface, third plane surface

[0062] Light emission surface, emitted light

[0063] Line focus

[0064] Distance

[0065] Thickness of the light-conducting core 4 on the substrate 3

[0066] Coupling optics

[0067] Coupling

[0068] Light entry surface proximal end of the substrate 3

[0069] length

[0070] Plate, one-piece continuous body of the coupling optic 18 optical cochlear implant

[0071] Housing

[0072] light source

[0073] Microlens array divergent light collimated light

[0074] Window linear microlens array 33 epoxy resin

[0075] 34 distal end of substrate 3

Claims

PATENT CLAIMS 1. Optical fiber (1) for an optical implant comprising a flexible substrate (3) elongated in a principal direction (2) from a proximal end (21) to a distal end, comprising at least one light-guiding core (4) arranged on the substrate (3), extending in the principal direction (2) from an input end (19) at the proximal end (21) of the substrate (3) along the substrate (3) and terminating with an output end (5) in front of the distal end of the substrate (3), comprising an input optic (18) that couples incident light in the principal direction (2) into the at least one light-guiding core (4), and an output optic (6) that deflects light exiting the output end (5) into a first transverse direction perpendicular to the principal direction (2), characterized in thatthat the coupling optics (18) are formed as a single-piece continuous optical body (24) onto the coupling end (19) of the at least one light-guiding core (4) and the substrate (3) such that the at least one light-guiding core (4) terminates with its coupling end (19) within the coupling optics (18) and is embedded in the coupling optics (18) for at least a minimum length along the principal direction (2), and / or the output coupling optics (6) are formed as a single-piece continuous optical body (7) onto the output end (5) of the at least one light-guiding core (4) and the substrate (3) such that the at least one light-guiding core (4) terminates with its output end (5) within the output coupling optics (6) and is embedded in the output coupling optics (6) for at least a minimum length along the principal direction (2), wherein the minimum length is equal to a thickness (17) of the core (4) on the substrate (3).

2. Optical fiber (1) according to claim 1, wherein the output coupling optics (6) focuses the light deflected in the first transverse direction more strongly in a longitudinal plane spanned by the first transverse direction and the main direction (2) than in a transverse plane spanned by a second transverse direction extending transversely to the main direction (2) and the first transverse direction and the main direction (2), wherein a distribution of the focused light in the longitudinal plane a half-width which optionally is a maximum of 10%, preferably a maximum of 5% and even more preferably a maximum of 2% of a half-width of the bundled light in the transverse plane.

3. Light guide (1) according to claim 2, wherein the output coupling optics (6) focuses the light deflected in the first transverse direction in the longitudinal plane, wherein a line focus (15) extends at a free distance (16) in the first transverse direction of 0.5 mm to 1.5 mm to the output coupling optics (6), and wherein the line focus (15) optionally has a width along the main direction (2) of no more than 0.1 mm in the longitudinal plane.

4. Light guide (1) according to claim 2 or 3, wherein the output coupling optics (6) has a convex light exit surface (13) which is more curved in the longitudinal plane than in the transverse plane, and wherein the convex light exit surface (13) optionally has a cylindrical shell section extending in the second transverse direction.

5. Optical fiber (1) according to one of the preceding claims, wherein the at least one light-conducting core (4) on the substrate (3) is covered with a sheath (10) which optionally covers the outcoupling end (5) but not the incoupling end (19).

6. Light guide (1) according to one of the preceding claims, wherein the coupling optics (18) and / or the coupling optics (6) are formed onto the light-conducting core (4) and the substrate (3) from a resin that is light-cured under two-photon excitation.

7. Light guide (1) according to one of the preceding claims, wherein the coupling optics (18) couples collimated light incident in the main direction (2) into the at least one light-guiding core (4).

8. Optical fiber (1) according to one of the preceding claims, wherein the coupling optics (18) are integrally formed on a first main surface facing the at least one light-guiding core (4) and a second main surface of the substrate (3) facing away from the at least one light-guiding core (4) and / or wherein the substrate (3) is reinforced at its proximal end (21) on its second main side facing away from the at least one light-conducting core (4) with a rigid plate (23).

9. Optical fiber (1) according to one of the preceding claims, wherein the output coupling optics (6) has a first flat surface (8) inclined at no more than 25° to the main direction (2), on the inside of which the light exiting from the output end (5) is totally reflected, and a second flat surface (11) adjoining the first flat surface (8) towards the light exit surface (13) of the output coupling optics (6), which is inclined at least 30° to the main direction (2) and at no more than 25° to the first flat surface (8), wherein optionally a third flat surface (12) adjoining the second flat surface (11) towards the light exit surface (13) is inclined at no more than 25° to the second flat surface (11), is inclined at least 30° to the first flat surface (8) and is inclined at no more than 80° to the main direction (2).

10. Light guide (1) according to claim 9, wherein the output coupling optics (6) is supported on the substrate (3) in the region of the first and / or second planar surface (8, 11) by means of support feet (9) aligned in the first transverse direction and laterally offset in the second transverse direction, which are optionally regions of the integrally continuous optical body (7) of the output coupling optics (6).

11. Optical fiber (1) according to one of the preceding claims, wherein, in addition to the at least one light-guiding core (4), at least one further light-guiding core (4) is arranged on the substrate (3), extends in the main direction (2) from a further coupling end (19) at the proximal end of the substrate (3) along the substrate (3) and terminates with a further coupling end (5) in the main direction (2) in front of the coupling end (5) of the at least one light-guiding core (4), wherein a further coupling optic (18), which couples incident light in the main direction (2) into the at least one further light-guiding core (4), is formed as a single-piece continuous optical body (24) onto the further coupling end (19) of the at least one further light-guiding core (4) and the substrate (3) such that the at least one further light-guiding core (4) with its further coupling end (19) is located within the further coupling optic (18) terminates and is embedded in the further coupling optics (18) for at least the minimum length along the main direction (2), and a further output coupling optics (6), which deflects light exiting from the further output end (5) into a further transverse direction perpendicular to the main direction (2) and parallel to the first transverse direction, is formed as a single continuous optical body (7) onto the further output end (5) of the at least one further light-guiding core (4) and the substrate (3) such that the at least one further light-guiding core (4) terminates with its further output end (5) within the further output coupling optics (6) and is embedded in the further output coupling optics (6) for at least the minimum length along the main direction (2).

12. Optical fiber (1) according to claim 11, wherein the output coupling optics (6) formed on several cores (4) and the substrate (3) are spaced apart from each other.

13. Optical fiber (1) according to claim 11 or 12, wherein the coupling optics (18) formed on several cores (4) and the substrate (3) form a linear microlens array (32).

14. Optical fiber (1) according to any of the preceding claims, wherein each core (4) extends over more than 50% of the length of the substrate (3) along the substrate (3).

15. Optical implant comprising a closed housing (26), an array of light sources (27) arranged in the housing (26), a microlens array (28) arranged in the housing (26) for collimating the light (29) from the light sources (27), a plane-parallel window (31) in the housing (26) adjoining the microlens array (28), and a light guide (1) adjoining the window (31) outside the housing (26) with its linear microlens array (32) according to claim 13 as far as referenced backwards to claim 4.

16. Optical implant according to claim 15, wherein a space between the window (31) and the linear microlens array (32) in a cavity on the outside of the housing (26) is filled with a cured transparent mass.

17. Optical implant according to claim 15 or 16, wherein each core (4) extends over more than 50% of the length of the substrate (3) along the substrate (3).

18. Optical implant according to any one of claims 15 to 17, wherein the optical implant is an optical cochlear implant (25).

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